In the first author's thesis [10], a sequential language, LRT, for real number computation is investigated. That thesis includes a proof that all polynomials are programmable, but that work comes short of giving a complete characterization of the expressive power of the language even for first-order functions. The technical problem is that LRT is non-deterministic. So a natural characterization of its expressive power should be in terms of relations rather than in terms of functions. In [2], Brattka examines a (...) formalization of recursive relations in the style of Kleene's recursive functions on the natural numbers. This paper is an expanded version of [13] which establishes the expressive power of LRTp, a variant of LRT, in terms of Brattka's recursive relations. Because Brattka already did the work of establishing the precise connection between his recursive relations and Type 2 Theory of Effectivity, we thus obtain a complete characterization of first-order definability in LRTp. (shrink)

We present a survey of the recent applications of continuous domains for providing simple computational models for classical spaces in mathematics including the real line, countably based locally compact spaces, complete separable metric spaces, separable Banach spaces and spaces of probability distributions. It is shown how these models have a logical and effective presentation and how they are used to give a computational framework in several areas in mathematics and physics. These include fractal geometry, where new results on existence and (...) uniqueness of attractors and invariant distributions have been obtained, measure and integration theory, where a generalization of the Riemann theory of integration has been developed, and real arithmetic, where a feasible setting for exact computer arithmetic has been formulated. We give a number of algorithms for computation in the theory of iterated function systems with applications in statistical physics and in period doubling route to chaos; we also show how efficient algorithms have been obtained for computing elementary functions in exact real arithmetic. (shrink)

We study some representations of real numbers. We compare these representations, on the one hand from the viewpoint of recursive functionals, and of complexity on the other hand.The impossibility of obtaining some functions as recursive functionals is, in general, easy. This impossibility may often be explicited in terms of complexity: - existence of a sequence of low complexity whose image is not a recursive sequence, - existence of objects of low complexity but whose images have arbitrarily high time- complexity .Moreover, (...) some representations of real numbers that are equivalent from the viewpoint of recursive functionals, are very distinct from the viewpoint of complexity.We make a particular study of representations via continued fractions . We precise exactly what part of information available in the x's dfc is equivalent to the information available in its Dedekinds cut. We show that the sum of two reals whose dfcs are polynomial-time computable may be a real whose dfc has time complexity arbitrarily high.This work confirms that the unique representation of real numbers suitable for the ordinary calculus is via explicit Cauchy sequences of rationals.RésuméNous étudions différentes manières de présenter les nombres réels. Nous comparons ces présentations du point de vue des fonctionnelles récursives d'une part, et de celui des classes de complexité d'autre part.L'impossibilité d'obtenir certaines fonctions sous forme de fonctionnelles récursives est en général facile à établir. Cette impossiblité peut souvent être explicitée en termes de complexité: - il existe une suite de faible complexité dont l'image est une suite non récursive, - il existe des objets de faible complexité mais dont les images sont des objets de complexité arbitrairement grande .En outre, certaines présentations des réels équivalentes du point de vue des fonctionnelles récursives se distinguent nettement du point de vue de la complexité.Nous faisons une étude particulière concernant les développements en fraction continue . Nous précisions exactement quelle est la partie de l'information disponible dans le dfc d'un réel x qui équivaut à l'information disponible dans sa coupure de Dedekind. Nous montrons également que la somme de deux réels dont le dfc est calculable en temps polynomial peut être un réel dont le dfc est de complexité arbitrairement grande.Ce travail confirme que seule une présentation des réels via des suites de rationnels explicitement de Cauchy est adaptée aux calculs avec les réels. (shrink)

One recursively enumerable real α dominates another one β if there are nondecreasing recursive sequences of rational numbers (a[n] : n ∈ ω) approximating α and (b[n] : n ∈ ω) approximating β and a positive constant C such that for all n, C(α − a[n]) ≥ (β − b[n]). See [R. M. Solovay, Draft of a Paper (or Series of Papers) on Chaitin’s Work, manuscript, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, 1974, p. 215] and [G. J. (...) Chaitin, IBM J. Res. Develop., 21 (1977), pp. 350–359]. We show that every recursively enumerable random real dominates all other recursively enumerable reals. We conclude that the recursively enumerable random reals are exactly the Ω-numbers [G. J. Chaitin, IBM J. Res. Develop., 21 (1977), pp. 350–359]. Second, we show that the sets in a universal Martin-Lof test for randomness have random measure, and every recursively enumerable random number is the sum of the measures represented in a universal Martin-Lof test. (shrink)

We study the system IFP of intuitionistic fixed point logic, an extension of intuitionistic first-order logic by strictly positive inductive and coinductive definitions. We define a realizability interpretation of IFP and use it to extract computational content from proofs about abstract structures specified by arbitrary classically true disjunction free formulas. The interpretation is shown to be sound with respect to a domain-theoretic denotational semantics and a corresponding lazy operational semantics of a functional language for extracted programs. We also show how (...) extracted programs can be translated into Haskell. As an application we extract a program converting the signed digit representation of real numbers to infinite Gray code from a proof of inclusion of the corresponding coinductive predicates. (shrink)

Let h : ℕ → ℚ be a computable function. A real number x is called h-monotonically computable if there is a computable sequence of rational numbers which converges to x h-monotonically in the sense that h|x – xn| ≥ |x – xm| for all n andm > n. In this paper we investigate classes h-MC of h-mc real numbers for different computable functions h. Especially, for computable functions h : ℕ → ℚ, we show that the class h-MC coincides (...) with the classes of computable and semi-computable real numbers if and only if Σi∈ℕ) = ∞and the sum Σi∈ℕ) is a computable real number, respectively. On the other hand, if h ≥ 1 and h converges to 1, then h-MC = SC no matter how fast h converges to 1. Furthermore, for any constant c > 1, if h is increasing and converges to c, then h-MC = c-MC. Finally, if h is monotone and unbounded, then h-MC contains all ω-mc real numbers which are g-mc for some computable function g. (shrink)

Area number x is called k-monotonically computable , for constant k > 0, if there is a computable sequence n ∈ ℕ of rational numbers which converges to x such that the convergence is k-monotonic in the sense that k · |x — xn| ≥ |x — xm| for any m > n and x is monotonically computable if it is k-mc for some k > 0. x is weakly computable if there is a computable sequence s ∈ ℕ of (...) rational numbers converging to x such that the sum equation image|xs — xs + 1| is finite. In this paper we show that a mc real numbers are weakly computable but the converse fails. Furthermore, we show also an infinite hierarchy of mc real numbers. (shrink)

Over recent decades, computer simulations have become a common tool among practitioners of the social sciences. They have been utilized to study such diverse phenomena as the integration and segregation of different racial groups, the emergence and evolution of friendship networks, the spread of gossip, fluctuations of housing prices in an area, the transmission of social norms, and many more. Philosophers of science and others interested in the methodological status of these studies have identified a number of distinctive virtues of (...) the use of computer simulations. For instance, it has been generally appreciated that as simulations require the formulation of an explicit algorithm, they foster precision and clarity about whatever conceptual issues are involved in the study. The value of computer simulations as a heuristic tool for developing hypotheses, models, and theories has also been recognized, as has been the fact that they can serve as a substitute for real experiments. This is especially useful in the social domain, given that human beings cannot be freely manipulated at the discretion of the experimenter . However, the main virtue of computer simulations is generally believed to be that they are able to deal with the complexities that arise when many elements interact in a highly dynamic system and which often evade an exact formal analysis. (shrink)

Given a class ℱ oft otal functions in the set oft he natural numbers, one could study the real numbers that have arbitrarily close rational approximations explicitly expressible by means of functions from ℱ. We do this for classes ℱsatisfying certain closedness conditions. The conditions in question are satisfied for example by the class of all recursive functions, by the class of the primitive recursive ones, by any of the Grzegorczyk classes ℰnwith n ≥ 2, by the class of all (...) functions recursive in a given function and by the class of the functions primitive recursive in it, as well as by the class of all total functions in the set of the natural numbers. (shrink)

A real is computable if it is the limit of a computable, increasing, computably converging sequence of rational...

Number concepts must support arithmetic inference. Using this principle, it can be argued that the integer concept of exactly ONE is a necessary part of the psychological foundations of number, as is the notion of the exact equality - that is, perfect substitutability. The inability to support reasoning involving exact equality is a shortcoming in current theories about the development of numerical reasoning. A simple innate basis for the natural number concepts can be proposed that embodies the arithmetic (...) principle, supports exact equality and also enables computational compatibility with real- or rational-valued mental magnitudes. (shrink)

On countable structures computability is usually introduced via numberings. For uncountable structures whose cardinality does not exceed the cardinality of the continuum the same can be done via representations. Which representations are appropriate for doing real number computations? We show that with respect to computable equivalence there is one and only one equivalence class of representations of the real numbers which make the basic operations and the infinitary normed limit operator computable. This characterizes the real numbers in terms of the (...) theory of effective algebras or computable structures, and is reflected by observations made in real number computer arithmetic. Demanding computability of the normed limit operator turns out to be essential: the basic operations without the normed limit operator can be made computable by more than one class of representations. We also give further evidence for the well-known non-appropriateness of the representation to some base b by proving that strictly less functions are computable with respect to these representations than with respect to a standard representation of the real numbers. Furthermore we consider basic constructions of representations and the countable substructure consisting of the computable elements of a represented, possibly uncountable structure. For countable structures we compare effectivity with respect to a numbering and effectivity with respect to a representation. Special attention is paid to the countable structure of the computable real numbers. (shrink)

A real number x is computable iff it is the limit of an effectively converging computable sequence of rational numbers, and x is left computable iff it is the supremum of a computable sequence of rational numbers. By applying the operations “sup” and “inf” alternately n times to computable sequences of rational numbers we introduce a non-collapsing hierarchy {Σn, Πn, Δn : n ∈ ℕ} of real numbers. We characterize the classes Σ2, Π2 and Δ2 in various ways and give (...) several interesting examples. (shrink)

In mathematics, various representations of real numbers have been investigated. All these representations are mathematically equivalent because they lead to the same real structure – Dedekind-complete ordered field. Even the effective versions of these representations are equivalent in the sense that they define the same notion of computable real numbers. Although the computable real numbers can be defined in various equivalent ways, if “computable” is replaced by “primitive recursive” , these definitions lead to a number of different concepts, which we (...) compare in this article. We summarize the known results and add new ones. In particular we show that there is a proper hierarchy among p. r. real numbers by nested interval representation, Cauchy representation, b -adic expansion representation, Dedekind cut representation, and continued fraction expansion representation. Our goal is to clarify systematically how the primitive recursiveness depends on the representations of the real numbers. (shrink)

In [8], the third author defined a reducibility$\le _w^{\rm{*}}$that lets us compare the computing power of structures of any cardinality. In [6], the first two authors showed that the ordered field of reals${\cal R}$lies strictly above certain related structures. In the present paper, we show that$\left \equiv _w^{\rm{*}}{\cal R}$. More generally, for the weak-looking structure${\cal R}$ℚconsisting of the real numbers with just the ordering and constants naming the rationals, allo-minimal expansions of${\cal R}$ℚare equivalent to${\cal R}$. Using this, we show that (...) for any analytic functionf,$\left \equiv _w^{\rm{*}}{\cal R}$. $is noto-minimal.). (shrink)

A real number is recursively approximable if there is a computable sequence of rational numbers converging to it. If some extra condition to the convergence is added, then the limit real number might have more effectivity. In this note we summarize some recent attempts to classify the recursively approximable real numbers by the convergence rates of the corresponding computable sequences ofr ational numbers.

We consider two classical computability notions for functions mapping all computable real numbers to computable real numbers. It is clear that any function that is computable in the sense of Markov, i.e., computable with respect to a standard Gödel numbering of the computable real numbers, is computable in the sense of Banach and Mazur, i.e., it maps any computable sequence of real numbers to a computable sequence of real numbers. We show that the converse is not true. This solves a (...) long-standing open problem posed by Kushner. (shrink)

The aim of this paper is to determine the logical and computational strength of instances of the Bolzano-Weierstraß principle and a weak variant of it.We show that BW is instance-wise equivalent to the weak König’s lemma for Σ01-trees . This means that from every bounded sequence of reals one can compute an infinite Σ01-0/1-tree, such that each infinite branch of it yields an accumulation point and vice versa. Especially, this shows that the degrees d ≫ 0′ are exactly those containing (...) an accumulation point for all bounded computable sequences.Let BWweak be the principle stating that every bounded sequence of real numbers contains a Cauchy subsequence . We show that BWweak is instance-wise equivalent to the cohesive principle and—using this—obtain a classification of the computational and logical strength of BWweak. Especially we show that BWweak does not solve the halting problem and does not lead to more than primitive recursive growth. Therefore it is strictly weaker than BW. We also discuss possible uses of BWweak. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (shrink)

The spectrum of a first-order sentence is the set of natural numbers occurring as the cardinalities of finite models of the sentence. In a recent survey, Durand et al. introduce a new class of real numbers, the spectral reals, induced by spectra and pose two open problems associated to this class. In the present note, we answer these open problems as well as other open problems from an earlier, unpublished version of the survey. Specifically, we prove that every algebraic real (...) is spectral, every automatic real is spectral, the subword density of a spectral real is either 0 or 1, and both may occur, and every right-computable real number between 0 and 1 occurs as the subword entropy of a spectral real. In addition, Durand et al. note that the set of spectral reals is not closed under addition or multiplication. We extend this result by showing that the class of spectral reals is not closed under any computable operation satisfying some mild conditions. (shrink)

ABSTRACT The Gödel–Dummett logic and Łukasiewicz one are two main many-valued logics used by the fuzzy logic community. Our goal is a quantitative comparison of these two. In this paper, we will mostly consider the 3-valued Gödel–Dummett logic as well as the 3-valued Łukasiewicz one. We shall concentrate on their implicational-negation fragments which are limited to formulas formed with a fixed finite number of variables. First, we investigate the proportion of the number of true formulas of a certain length n (...) to the number of all formulas of such length built with exactly one variable. Then, we investigate such proportion for satisfiable formulas. Second, we generalise our investigation on formulas written with $ k\ge 1 $ k ≥ 1 variables. The primary goal of the paper is the research on the asymptotic behaviour of these fractions when the length n tends to infinity. If such limits exists, they are real numbers between 0 and 1, which are called the density of truth or the density of SAT. To compare the density of truth and the density of satisfiable formulas for both fragments of 3-valued Gödel–Dummett's and Łukasiewicz's logics we use the powerful theory of analytic combinatorics. This paper is a natural continuation of the previous brief conference note by Kostrzycka and Zaionc (2020) as well as enriched with some previous results from Kostrzycka and Zaionc (2003). In the conference note we computed analytically the density of truth and the density of SAT (with a determined precision) for 3-valued Łukasiewicz's logic restricted to a language with only one variable. In Kostrzycka and Zaionc (2003) we computed the same values for exactly the same fragment of the 3-valued Gödel–Dummett logic. This paper answers the more general questions of the existence of density of truth and density of SAT for both many-valued logics with an arbitrary finite number of variables. Therefore this paper gives an an interesting picture of two main families of finite-valued fuzzy logics problems treated quantitatively. This picture is taken from the perspective of classical logic. It shows that unexpectedly there is quantitatively a little distance between these two approaches. (shrink)

I defend Putnam’s modal structuralist view of mathematics but reject his claims that Wittgenstein’s remarks on Dedekind, Cantor, and set theory are verificationist. Putnam’s “realistic realism” showcases the plasticity of our “fitting” words to the world. The applications of this—in philosophy of language, mind, logic, and philosophy of computation—are robust. I defend Wittgenstein’s nonextensionalist understanding of the real numbers, showing how it fits Putnam’s view. Nonextensionalism and extensionalism about the real numbers are mathematically, philosophically, and logically robust, but the (...) two perspectives are often confused with one another. I separate them, using Turing’s work as an example. (shrink)

The usual completeness theorem for first-order logic is extended in order to allow for a natural incorporation of real analysis. Essentially, this is achieved by building in the set of real numbers into the structures for the language, and by adjusting other semantical notions accordingly. We use many-sorted languages so that the resulting formal systems are general enough for axiomatic treatments of empirical theories without recourse to elements of set theory which are difficult to interprete empirically. Thus we provide a (...) way of applying model theory to empirical theories without tricky detours. Our frame is applied to axiomatizations of three empirical theories: classical mechanics, phenomenological thermodynamics, and exchange economics. (shrink)

In mathematics, various representations of real numbers have been investigated. All these representations are mathematically equivalent because they lead to the same real structure - Dedekind-complete ordered field. Even the effective versions of these representations are equivalent in the sense that they define the same notion of computable real numbers. Although the computable real numbers can be defined in various equivalent ways, if computable is replaced by primitive recursive (p. r., for short), these definitions lead to a number of different (...) concepts, which we compare in this article. We summarize the known results and add new ones. In particular we show that there is a proper hierarchy among p. r. real numbers by nested interval representation, Cauchy representation, b -adic expansion representation, Dedekind cut representation, and continued fraction expansion representation. Our goal is to clarify systematically how the primitive recursiveness depends on the representations of the real numbers. (shrink)

If one wants to compute with infinite objects like real numbers or data streams, continuity is a necessary requirement: better and better (finite) approximations of the input are transformed into better and better (finite) approximations of the output. In case the objects are constructively generated, they can be represented by a finite description of the generating procedure. By effectively transforming such descriptions for the generation of the input (respectively, their codes) into (the code of) a description for the generation of (...) the output another type of computable operation is obtained. Such operations are also called effective. The relationship of both classes of operations has always been a question of great interest. In this paper the setting is extended to the case of multifunctions. Various ways of coding (indexing) sets are discussed and their relationship is investigated. Moreover, effective versions of several continuity notions for multifunctions are introduced. For each of these notions an indexing system for sets is exhibited so that the multifunctions that are effective with respect to this indexing system are exactly the multifunction which are effectively continuous with respect to the continuity notion under consideration. Mostly, in addition to being effective the multifunctions need also possess certain witnessing functions. Important special cases are discussed where such witnessing functions always exist. (shrink)

An event is something in space and time, just some of it, and so it is rightly said to be something that occurs or happens. For at least these reasons it is not a number or a proposition, or any abstract object. There are finer conceptions of an event, of course, one being a thing having a general property for a time, another being exactly an individual property of a thing -- say my computer monitor's weight (19 kg) as against (...) yours (also 19 kg). None of these finer conceptions can put in doubt that events are individuals in a stretch of time and space. (shrink)

The basic motivation behind this work is to tie together various computational complexity classes, whether over different domains such as the naturals or the reals, or whether defined in different manners, via function algebras (Real Recursive Functions) or via Turing Machines (Computable Analysis). We provide general tools for investigating these issues, using two techniques we call approximation and lifting. We use these methods to obtain two main theorems. First, we provide an alternative proof of the result from Campagnolo et al. (...) (J Complex 18:977–1000, 2002), which precisely relates the Kalmar elementary computable functions to a function algebra over the reals. Second, we build on that result to extend a result of Bournez and Hainry (Theor Comput Sci 348(2–3):130–147, 2005), which provided a function algebra for the ${\mathcal{C}}^2$ real elementary computable functions; our result does not require the restriction to ${\mathcal{C}}^2$ functions. In addition to the extension, we provide an alternative approach to the proof. Their proof involves simulating the operation of a Turing Machine using a function algebra. We avoid this simulation, using a technique we call lifting, which allows us to lift the classic result regarding the elementary computable functions to a result on the reals. The two new techniques bring a different perspective to these problems, and furthermore appear more easily applicable to other problems of this sort. (shrink)

The Gödel–Dummett logic and Łukasiewicz one are two main many-valued logics used by the fuzzy logic community. Our goal is a quantitative comparison of these two. In this paper, we will mostly consider the 3-valued Gödel–Dummett logic as well as the 3-valued Łukasiewicz one. We shall concentrate on their implicational-negation fragments which are limited to formulas formed with a fixed finite number of variables. First, we investigate the proportion of the number of true formulas of a certain length n to (...) the number of all formulas of such length built with exactly one variable. Then, we investigate such proportion for satisfiable formulas. Second, we generalise our investigation on formulas written with k≥1 variables. The primary goal of the paper is the research on the asymptotic behaviour of these fractions when the length n tends to infinity. If such limits exists, they are real numbers between 0 and 1, which are called the density of truth or the density of SAT. To compare the density of truth and the density of satisfiable formulas for both fragments of 3-valued Gödel–Dummett's and Łukasiewicz's logics we use the powerful theory of analytic combinatorics. This paper is a natural continuation of the previous brief conference note by Kostrzycka and Zaionc (Citation2020) as well as enriched with some previous results from Kostrzycka and Zaionc (Citation2003). In the conference note we computed analytically the density of truth and the density of SAT (with a determined precision) for 3-valued Łukasiewicz's logic restricted to a language with only one variable. In Kostrzycka and Zaionc (Citation2003) we computed the same values for exactly the same fragment of the 3-valued Gödel–Dummett logic. This paper answers the more general questions of the existence of density of truth and density of SAT for both many-valued logics with an arbitrary finite number of variables. Therefore this paper gives an an interesting picture of two main families of finite-valued fuzzy logics problems treated quantitatively. This picture is taken from the perspective of classical logic. It shows that unexpectedly there is quantitatively a little distance between these two approaches. (shrink)

A topological index can be focused on uprising of a chemical structure into a real number. The degree-based topological indices have an active place among all topological indices. These topological descriptors intentionally associate certain physicochemical assets of the corresponding chemical compounds. Graph theory plays a very useful role in such type of research directions. The hex-derived networks have vast applications in computer science, physical sciences, and medical science, and these networks are constructed by hexagonal mesh networks. In this paper, we (...) determined the exact values of vertex-edge-degree-based topological descriptors for hex-derived networks HDN 1 p and HDN 2 p, which are generated by the hexagonal network of dimension p. (shrink)

In [5] it has been shown that for first-order definability over the reals there exists an effective procedure which by a finite formula with equality defining an open set produces a finite formula without equality that defines the same set. In this paper we prove that there exists no such procedure for Σ-definability over the reals. We also show that there exists even no uniform effective transformation of the definitions of Σ-definable sets into new definitions of Σ-definable sets in such (...) a way that the results will define open sets, and if a definition defines an open set, then the result of this transformation will define the same set. These results highlight the important differences between Σ-definability with equality and Σ-definability without equality. (shrink)

For the given logical calculus we investigate the proportion of the number of true formulas of a certain length n to the number of all formulas of such length. We are especially interested in asymptotic behavior of this fraction when n tends to infinity. If the limit exists it is represented by a real number between 0 and 1 which we may call the density of truth for the investigated logic. In this paper we apply this approach to the intuitionistic (...) logic of one variable with implication and negation. The result is obtained by reducing the problem to the same one of Dummett's intermediate linear logic of one variable (see [2]). Actually, this paper shows the exact density of intuitionistic logic and demonstrates that it covers a substantial part (more than 93%) of classical prepositional calculus. Despite using strictly mathematical means to solve all discussed problems, this paper in fact, may have a philosophical impact on understanding how much the phenomenon of truth is sporadic or frequent in random mathematics sentences. (shrink)

The strong weak truth table (sw) reducibility was suggested by Downey, Hirschfeldt, and LaForte as a measure of relative randomness, alternative to the Solovay reducibility. It also occurs naturally in proofs in classical computability theory as well as in the recent work of Soare, Nabutovsky, and Weinberger on applications of computability to differential geometry. We study the sw-degrees of c.e. reals and construct a c.e. real which has no random c.e. real (i.e., Ω number) sw-above it.

The computability of reals was introduced by Alan Turing [20] by means of decimal representations. But the equivalent notion can also be introduced accordingly if the binary expansion, Dedekind cut or Cauchy sequence representations are considered instead. In other words, the computability of reals is independent of their representations. However, as it is shown by Specker [19] and Ko [9], the primitive recursiveness and polynomial time computability of the reals do depend on the representation. In this paper, we explore how (...) the weak computability of reals depends on the representation. To this end, we introduce three notions of weak computability in a way similar to the Ershov's hierarchy of Δ02-sets of natural numbers based on the binary expansion, Dedekind cut and Cauchy sequence, respectively. This leads to a series of classes of reals with different levels of computability. We investigate systematically questions as on which level these notions are equivalent. We also compare them with other known classes of reals like c. e. and d-c. e. reals. (shrink)

Given any oracle, A, we construct a basic sequence Q, computable in the jump of A, such that no A-computable real is Q-distribution-normal. A corollary to this is that there is a Δn+10 basic sequence with respect to which no Δn0 real is distribution-normal. As a special case, there is a limit computable sequence relative to which no computable real is distribution-normal.

The present article discusses the computational tools (both conceptual and material) used in various attempts to deal with individual cases of FLT, as well as the changing historical contexts in which these tools were developed and used, and affected research. It also explores the changing conceptions about the role of computations within the overall disciplinary picture of number theory, how they influenced research on the theorem, and the kinds of general insights thus achieved. After an overview of Kummer’s contributions and (...) its immediate influence, I present work that favored intensive computations of particular cases of FLT as a legitimate, fruitful, and worth-pursuing number-theoretical endeavor, and that were part of a coherent and active, but essentially low-profile tradition within nineteenth century number theory. This work was related to table making activity that was encouraged by institutions and individuals whose motivations came mainly from applied mathematics, astronomy, and engineering, and seldom from number theory proper. A main section of the article is devoted to the fruitful collaboration between Harry S. Vandiver and Emma and Dick Lehmer. I show how their early work led to the hesitant introduction of electronic computers for research related with FLT. Their joint work became a milestone for computer-assisted activity in number theory at large. (shrink)

A new approach for a uniform classification of the computably approximable real numbers is introduced. This is an important class of reals, consisting of the limits of computable sequences of rationals, and it coincides with the 0'-computable reals. Unlike some of the existing approaches, this applies uniformly to all reals in this class: to each computably approximable real x we assign a degree structure, the structure of all possible ways available to approximate x. So the main criterion for such classification (...) is the variety of the effective ways we have to approximate a real number. We exhibit extreme cases of such approximation structures and prove a number of related results. (shrink)

In this paper we investigate conditions for Lp-computability which are in accordance with the classical Grzegorczyk notion of computability for a continuous function. For a given computable real number p ≥ 1 and a compact computable rectangle I ⊂ ℝq, we show that an Lp function f ∈ Lp is LP-computable if and only if f is sequentially computable as a linear functional and the Lp-modulus function of f is effectively continuous at the origin of ℝq.

For the computability of subsets of real numbers, several reasonable notions have been suggested in the literature. We compare these notions in a systematic way by relating them to pairs of ‘basic’ ones. They turn out to coincide for full-dimensional convex sets; but on the more general class of regular sets, they reveal rather interesting ‘weaker/stronger’ relations. This is in contrast to single real numbers and vectors where all ‘reasonable’ notions coincide.

For any class of operators which transform unary total functions in the set of natural numbers into functions of the same kind, we define what it means for a real function to be uniformly computable or conditionally computable with respect to this class. These two computability notions are natural generalizations of certain notions introduced in a previous paper co-authored by Andreas Weiermann and in another previous paper by the same authors, respectively. Under certain weak assumptions about the class in question, (...) we show that conditional computability is preserved by substitution, that all conditionally computable real functions are locally uniformly computable, and that the ones with compact domains are uniformly computable. The introduced notions have some similarity with the uniform computability and its non-uniform extension considered by Katrin Tent and Martin Ziegler, however, there are also essential differences between the conditional computability and the non-uniform computability in question. (shrink)

Infinite time Turing machines represent a model of computability that extends the operations of Turing machines to transfinite ordinal time by defining the content of each cell at limit steps to be the lim sup of the sequences of previous contents of that cell. In this paper, we study a computational model obtained by replacing the lim sup rule with an ‘eventually constant’ rule: at each limit step, the value of each cell is defined if and only if the content (...) of that cell has stabilized before that limit step and is then equal to this constant value. We call these machines weak infinite time Turing machines. We study different variants of wITTMs adding multiple tapes, heads, or bidimensional tapes. We show that some of these models are equivalent to each other concerning their computational strength. We show that wITTMs decide exactly the arithmetic relations on natural numbers. (shrink)

Numbers. Natural numbers -- Integers -- Real numbers -- Irrational and transcendental numbers -- Funny numbers. Zero -- e : the unnatural natural number -- [Phi] : the golden ratio -- i : the imaginary number -- Writing numbers. Roman numerals -- Egyptian fractions -- Continued fractions -- Logic. Mr. Spock is not logical -- Proofs, truth, and trees : oh my! -- Programming with logic -- Temporal reasoning -- Sets. Cantor's diagonalization : infinity isn't just infinity -- Axiomatic set (...) theory : keep the good, dump the bad -- Models : using sets as the LEGOs of the math world -- Transfinite numbers : counting and ordering infinite sets -- Group theory : finding symmetries with sets -- Mechanical math. Finite state machines : simplicity goes far -- The turing machine -- Pathology and the heart of computing -- Calculus : no, not that calculus- [lambda] calculus -- Numbers, booleans, and recursion -- Types, types, types : modeling [lambda] calculus -- The halting problem. (shrink)

This book is dedicated to a classic presentation of the theory of computable functions in the context of the foundations of mathematics. Part I motivates the study of computability with discussions and readings about the crisis in the foundations of mathematics in the early 20th century, while presenting the basic ideas of whole number, function, proof, and real number. Part II starts with readings from Turing and Post leading to the formal theory of recursive functions. Part III presents sufficient formal (...) logic to give a full development of Gödel's incompleteness theorems. Part IV considers the significance of the technical work with a discussion of Church's Thesis and readings on the foundations of mathematics. This new edition contains the timeline "Computability and Undecidability" as well as the essay "On mathematics". (shrink)

In lieu of an abstract, here is a brief excerpt of the content:The Touching TestAI and the Future of Human IntimacyMartha J. Reineke (bio)Each Friday, the New York Times publishes Love Letters, a compendium of articles on courtship. A recent story featured Melinda, a real estate agent, and Calvin, a human resources director.1 They had met at a market deli counter. On their first date, a lasagna dinner at Melinda's home, Calvin posed the question, "What are you looking for in (...) a man?" To his surprise, Melinda reached into her pocket and pulled out a two-page list, "Melinda's Husband Traits." Her 46-item list begins with "Christian, honor God, put Him first" and includes as entry number 37, "He likes to be touched and likes to touch me." Notwithstanding laudable features of Melinda's inventory, if David Levy, President of the International Computer Games Association and an expert on artificial intelligence (AI), is correct in his predictions, in the years ahead, women like Melinda who know exactly what they are looking for in a husband will desire something radically new: a robot. After all, artificial agents will soon possess or improve on every quality the romantically inclined previously have sought in a human partner. [End Page 123]Levi predicts robots will be preferred romantic partners by the middle of this century.2 Capable of providing erotic satisfaction and creating deep emotional bonds with human partners, these robots will be an achievable outcome of AI engineering that already has brought to market industrial and service robots, virtual pets, and caregiver robots for the elderly. Levi offers a research-based inventory of traits a robot will offer its human partner: kindness and understanding, a sense of humor, expressiveness, intelligence, and sociability.3 He pinpoints additional features that will facilitate romance: The ideal robot partner will elicit erotic attraction, give evidence of readiness for a serious relationship with its verbal assertions, and possess a capacity for mutual intimacy.4 Levi's argument is intentionally provocative, for he emphasizes the centrality of sex to future robot/human pairings, waxing rhapsodic about the performative superiority of robots to humans in the sexual act.5Elaborating on potential human love relationships with robots, Levi asserts that a robot will need to master imitation if a human is to want it as a romantic partner. Not only is imitation a central aspect of every human-to-human relationship, but also imitation has been identified by researchers as a crucial element in romantic desire.6 Levi states that human-to-human attraction is founded on similarities between prospective partners in appearance, personality, and social context. It is sustained only through what Levi calls "reciprocal liking."7 For romantic relationships between humans and robots to flourish, they too must engage in acts of reciprocal imitation.In highlighting the necessity of imitation in effective robot and human interactions, Levi draws close to René Girard's theory of "mimetic desire." According to Girard, imitation structures all "wanting,"8 delineating what we aspire to look like or hope to possess and determining what we value, take comfort in, or experience as a threat. Indeed, the individual is never the origin point of its desires. Each of us always desires mimetically—according to the desire of the other.9 As Scott Garrels confirms in Mimesis and Science, researchers studying imitation in developmental, comparative, and social psychology, as well as in neurophysiology and cognitive neuroscience, support Girard's claims: Imitation is fundamental in human life.10 Likewise, Girard concurs with Levi that romantic relationships are primary examples of imitative desire. As described by Girard in Deceit, Desire, and the Novel, imitative behaviors form the romantic triangles that feature prominently in fiction: for example, Odette and the many men enchanted by her in Proust's In Search of Lost Time; Anselmo, Lotario, and Camilla in Don Quixote; and Velchaninov and Troussotzki, along with Troussotzki's deceased wife and prospective fiancée, in Dostoyevsky's The Eternal Husband.11 [End Page 124]Notwithstanding similarities in Levi and Girard's views of imitation, they differ in a crucial respect. Only Girard acknowledges just how extraordinarily fraught mimesis can become. When imitators compete (e.g., for things, status, and experiences), they will contest... (shrink)

"Ever Since This World Began" from Love Dog (Penny-Ante Editions, 2013) by Masha Tupitsyn continent. The audio-essay you've recorded yourself reading for continent. , “Ever Since the World Began,” is a compelling entrance into your new multi-media book, Love Dog (Success and Failure) , because it speaks to the very form of the book itself: vacillating and finding the long way around the question of love by using different genres and media. In your discussion of the face, one of the (...) themes of Love Dog , I think there is something to be said about the surfaces media create and how you constantly manipulate them in your work. This seems important for thinking also about your book LACONIA: 1,200 Tweets on Film ; a book on film written in tweets, interposing already three sets of expectations and pushing the boundaries of each medium's faciality, it's surface tension. In Love Dog , is there another kind of facial interaction? Perhaps the discursive faces of approaching love as topic and love as method? If so, how did/do these intersect for you, do/did they drive the creation of this book? MASHA TUPITSYN With LACONIA and Love Dog , I wanted to pay homage to the work modernism has done on subjective time and chronological time by carrying that experiment over into the digital economy. Because LACONIA is a time-based work of cultural criticism that employs the aphorism to look at 21 st century American culture, it is also an archival work of cultural mourning and memory. And in Love Dog , which is also a work about mourning as it relates to love, I wanted to think with all my senses, and to reflect that in the writing itself by using a multi-media form. LACONIA tackled the sound bite and the promotional image--the everyday language of consumer culture--which often wants to communicate ideological agendas through the repetition of a single image or reductive phrase. I had always been interested in the approaches of artists like Barbara Kruger and Jenny Holzer and essayistic, typographical filmmakers, like Chris Marker and Godard. In both cases, I felt it was important to try to compose a book in which deep—critical—thinking happens in so-called immediate, informal, and disposable contexts. That is, in places where you are either not supposed to be serious or are not required to take things seriously. To me the most intervention is needed in every day instances of culture and representation. In order to do that, I had to utilize and interrogate the very structures I was critiquing. In other words, the writing had to materialize in that live, digital, public space. It couldn’t simply happen at home on a piece of paper or in a word document on my computer that no one could see until it was finished. It had to unfold in real time, amidst everything else. And it had to literally be surrounded by the cultural landscape I wanted to assess. In both LACONIA and Love Dog , I wanted to know how and if we can get away from what we cannot get away from? From which there is no respite. Given this, I don’t think hypertexts can really be called hypertexts anymore. Hypertexts are simply the world today. This is not only the way we read the world now. It is the way the world reads. Likewise, interfaciality, as you put it, works on a number of levels for me, both on and off the page. There is my relation to epistemological and phenomenological surfaces—the screen, the body, the face, the voice, gender; the official story. Then there is the way this dovetails formally, and to which the digital adds yet another dimension. It’s also where sound comes into Love Dog (giving the book a sound; giving tonality to the book’s ideas and feelings). As Anne Carson pointed out in her essay “The Gender of Sound,” the two are connected, and of course so are love and gender. In “Ever Since This World Began,” I wanted to think about the phenomenology of the voice, which is why I visualize the sonic in the book and why in my writing about faces, I look at the tonal aspects (the things a face voices and a voice faces) of a face. This was standard to do when images and faces were “silent” in the silent era. Those images/faces were extraordinarily audible. The greatest screen face, to me, is still Falconetti’s in Dreyer’s The Passion of Joan of Arc . We can hear her face—even though there is no actual sound on screen of her speaking. The internet is a similarly “silent” space where actual voices are lacking. So intertextuality goes with interfaciality. I’ve also talked a lot about how categorization worked when it came to the reception of my first book, Beauty Talk & Monsters . How despite the fact that Beauty Talk is a text that crisscrosses form and content in a variety of ways, not pinpointing its exact genre—choosing one genre over another—only made things worse. Fiction was the category people were most adverse to me using, even though of course there is a lot of fiction in the book. Part of how fiction works in Beauty Talk is in the reader not knowing exactly where the fiction resides. In Godard’s 1967 film, Weekend , for example, everything matters. Everything is political, whether it’s real or imaginary, film or reality. In Weekend , life is not a game and neither is the game a game. The game is really life. Either everything is important or nothing is. But many people want clear answers and demarcations so that they can decide what is important and what is not important. My use of the “I,” subjective criticism, made everything “real” in Beauty Talk . But fiction is in the construction. It is in the blending. This is why I perforate the movie screen and connect the onscreen and the offscreen; the official story and the backstory. Although I don’t think there is a difference between onscreen and offscreen anymore. Nor is there a dialectic. It’s all screen all the time now. Non-fiction, on the other hand, was more tolerated as a moniker. Unlike Love Dog , Beauty Talk wasn’t explicitly or tangibly (what is tangible is a question in all these books) working with digital forms or within this digital economy, so some people resisted the book’s hypertextuality or intertextuality because they couldn’t see its other forms, if that makes sense. It was a problem of invisibility; of how to make something appear (this is where Nietzsche, big presence in Love Dog , comes in—the nature of appearances). Something people don’t necessarily want to see. Some readers couldn’t see the way forms were interfacing in that book. On the surface, Beauty Talk was simply a text about media culture—the domination of entertainment as a mode of being and knowing—and most readers could only see that one side of the book. But as Godard puts it in Wim Wenders’ documentary about the future of cinema, Room 666 , “Films are made, images are made, when there’s no one looking. That’s what the invisible is, that which we don’t see. That’s what the incredible is, that which we don’t see. And cinema shows you that which we don’t see, the incredible.” We are living in the aftermath of narrative and temporal collapse, which means we don’t read or feel in the same way. I began to use digital forms in my writing because I don’t see us as traditional book people anymore. I would add that power also resides in the invisible, in the things we make invisible by making them visible. Or it did for a long time. The new face of power is quickly becoming so-called transparency, which is even more corrupt because even though we now live in a behind-the-scenes culture, and see and know how the mechanisms of power and corruption operate, we still don't change. The world still doesn't change. Finally, another important thing that Godard says in Room 666 that relates to Love Dog is: “I’m here in front of the camera, and yet in my body and in my head, I’m behind it. My world is the imaginary and the imaginary is a journey between forwards and backwards.” This idea of visible/invisible, foresight and hindsight , backwards and forwards is an important dialectic in relation to time and the idea of the destinal. This is why I wanted Love Dog to travel, literally, figuratively, and discursively. You have to be open to not knowing. To epistemological, geographical, chronological, and emotional aporias. In Love Dog my story is both visible and invisible to me. Sometimes I could see where I was going. Other times I was completely in the dark existentially. Truth procedure, which love is, as bell hooks and Badiou tell us, requires expedition and openness to possibility. Unless you want a story you already know, but that is not truth procedure. So I tried to create this backwards and forwards journey in the book—this sense of travel and motion, hope and doubt—by jumping between forms, media, time; traveling to different places, texts, and emotional registers. The book’s “Time-Jump series,” which mostly takes the form of music—songs—but also a series of “green” videos that I shot, is the most obvious tribute to this idea of subjective and chronological time. continent. Your work aligns with writers that play with the form of their language, or have assumed the role of performance artist at some point: Kathy Acker, Chris Kraus, Avital Ronell, and Anne Carson to name a few representing varied approaches that show up in Love Dog . At the risk of ossifying the work, or missing the point—as these experimental modes of writing stack-up in piles of published works, do they approach a genre? MASHA As I noted in my book Life As We Show It , in Chelsea Girls the poet Eileen Myles points out, “You can’t get money without a category.” More importantly, you can’t get a category—or respect, rank—without a clear genre. This makes genre and gender an obvious pair. The two words are even linked etymologically and both genre and gender concern taxonomies of legitimacy—of sorting through what and who is valuable. So the words share common prejudices. The things one does not want to read is often synonymous with who one doesn't want to read about. Therefore a break-up of or with genre is maybe the genre or anti-genre that could be said to link these writers. Avital Ronell breaks up with philosophical tradition and modes of inquiry. Like Nietzsche, she revaluates methods of evaluation, testing out things you are not supposed to use philosophy to test (and, by the same token, testing philosophy in ways it’s not supposed to be tested), like drugs and stupidity—where philosophy fails and we fail philosophy. And Chris Kraus does something similar in her experimental fiction, using different forms to put female subjectivity “to the test,” so to speak. All these female writers and thinkers have tried to destabilize the systems that have been set up in (and against) writing. Thus missing the mark with genre, even intentionally, means that we have missed the point in some sense as writers and thinkers. And that to me is a good thing, however difficult. We’ve started at the wrong point and gone somewhere else instead. We’ve acknowledged that writing and thinking are also about failure, and that failure is always embedded in the act of writing and in our reasons for writing. So that missing the point is also the point. Derrida insisted: “We must invent a name for those ‘critical’ inventions which belong to literature while deforming its limits.” But how can you give something that resists and deforms, a name? Wouldn’t the name also be deformed? Isn't this why the aforementioned writers get hyphenated descriptors like ficto-criticism? Do we need a proper name to be able to read something carefully? I don’t think so. I don’t need it as a reader. I’ve always taken a work on its own terms. But for most people, if you don’t have an address, people don’t know how to find you. A lot of time, they won’t even know how to look. And in some cases, they’ll think you’re not even worth finding. You are not on the map because you have to literally make the map in order to exist. In her essay, “The Gender of Sound” Carson asks, “Why is female sound bad to hear?” I think for the same reason something uncategorizable (pedagogically, creatively, racially, and sexually)—Other—is hard to read. *For an audio recording of Florida , read by Masha Tupitsyn click here . continent. : We're also curious to hear know how you see the significance of 'performance' (and why the label sticks to the shoes of these authors like toilet paper) in describing this kind of writing work? MASHA I think I responded to the parenthetical portion of this question in my previous answer. As far as how performance relates to Love Dog , in Acker’s Don Quixote , which is another big presence in the book, she writes, “there is no other reality than anthropomorphism.” In Don Quixote , the dog is human and the human is dog. Which brings us to the title of Love Dog and the totemic function of the dog in the book: giving human things animal characteristics and animal things human characteristics. Rather than investing all our human love ideals into dogs, which we do constantly as a culture of dog lovers, I wanted to put the dog into love. It is the difference between the consumption of love as a patriarchal institution or status position and the essence of a type of radical and liberatory relation that would benefit humans in their bonds with other humans. So the dog in Love Dog is not simply the book’s cover or performative affect, so to speak. Love has always needed the dog, which is why the dog is the very embodiment of belief in love . Recall Argos The Great Dog and Odysseus. Argos is the only one who remembers and recognizes the ragged and old Odysseus even after his 20-year absence. So love is the high ideal and the dog, both common and dependable, is the bridge between the sacred and the profane. The dog is the house of love. And because Love Dog is a digital project, it seemed impossible to think about the post-human, technology, the virtual, or difference (which Badiou says is essential to love in In Praise of Love ) without thinking about animal-being and being-animal. Instead of simply “performing” these ideas and characteristics as literary affects, I’m interested in being-becoming. Which means the book’s tropes, leitmotifs, series, and even its titles are in service of that truth procedure. In other words, I actually want to live this way, not just write this way. And, more importantly, I want to live this way not just think this way. So Love Dog became both my totem animal and my autobiographical animal. This made the book organic, anthropomorphic—beyond literary. See the trailer to Masha Tupitsyn's new book available now from Penny Ante Editions. (shrink)

continent. 1.3 (2011): 201-207. “Poetry is experience, linked to a vital approach, to a movement which is accomplished in the serious, purposeful course of life. In order to write a single line, one must have exhausted life.” —Maurice Blanchot (1982, 89) Nikos Karouzos had a communist teacher for a father and an orthodox priest for a grandfather. From his four years up to his high school graduation he was incessantly educated, reading the entire private library of his granddad, comprising mainly (...) the Orthodox Church Fathers and the ancient classics. Later on in his life he sold the library for money, only to buy a little more time before he went broke again: “I carry sorrow like a cage/ I got no birds/ as I come back from her hair/ I see the profit emptied/ cool from terror.” (1993, Ι, 101) Nowadays—and ridiculously recently—we are more than apt to speak of a certain insouciance pertaining to the Greek form of expenditure: expenditure without any type of investment, sometimes not (even) symbolic. In the vaults of the European unconscious, this imprudent stance still conjures a “capital punishment” in the form of de-capitation, reflecting back the fear of excess and the terror of its consequences.1 Thus the Greek way of living is very close to what a stranger could have termed as “the Greek way of dying.” Yet, what is not often understood is that the Greek esprit , the same one that invented the maxim μηδ?ν ?γαν (“nothing in excess”), does not experience death solely as an imminent fear of bankruptcy. For it miraculously combines its unconditional acceptance with the promise of a resurrection that is always there in the scents of Spring, from Dionysus to the orthodox Christ: “Everyone resurrects himself through dying [….] Resurrection is the switching of mortalities.” (2002, 94) Hence, if an entire library was imprudently traded for a plate with seven olives, a sliced tomato and some fresh goat cheese, let us not be fooled: this is not the meal of the pauper, but that of “an aristocrat from God” (1993, II, 491) feeding his eloquent loudmouth, ridiculously cut open in an otherwise rock-solid caput . *** To speak of the Greek experience is to speak about a half-dead language that still utters in life what is seemingly excluded from it and thus forbidden to be talked about: death. Death as anything that is out of this world, as something that will never return . Still, along with an experience of death that recently waned as a worn-out academic fashion, the Greek experience is dead too. Nearly 2300 years of written words separating Homer from the fall of Byzantium equal 500 books on a library traded for money: “I am with the killed. Hence my deepest solitude. I do not feel this tremendous macho society, beyond from the fact that it is a ruthlessly consuming one. It is me who pays all the time .” (2002, 57) Let us do the math and see how much this dealing with the Greek experience is costing the poet and how much dealing with the Greek experience might cost us today. *** “I do not guarantee a single word.” (Karouzos, 1993, II, 454) Through its various dialects and forms, the Greek language speaks through an incessant historical dissemination. Anyone who is aware of this terrifying polymorphy and still calls himself a poet, must stand against a white sheet of paper, pen-in-hand, with a very particular duty: to be as fully inconsistent as possible. In the formally ironic uniqueness of the poem, the poet functions as “a band-aid for lesser and greater antinomies.” (1993, I, 251) Of course these antinomies are not exhausted in language—they are historical, political and, alas, existential. Yet, beyond appearances , it is language that ruthlessly encodes them through history, submitting the poet to the temptation of placing them one next to the other on a single white sheet. The closer their neighboring, the greater the scattering of the writer in the ironic uniqueness of the paper. In a work where poetic license is described as a “freedom-impasse” (2002, 51), this task is undertaken in full conscience of its personal consequences: “what I am interested in is to escape my individuality (envisioning the non-ego) […] Nevertheless, my dissociations never achieve duration.” (2002, 74-75) Hence, though poetry is the “deserted direction of will,” (1998, 62) the stance of the poet is not that of a Nietzschean “great man.”2 Whereas drunkenness provides a thread between the poem and the excess it both presupposes and infuses (“Poetry always enlarges. ‘Drunkenness’ is nothing more than that,” (2002, 85)), whereas language flashes in loudmouth spurts of déraison (“When I am alone I do something else. I utter words. For example, while having my ouzo and listening to music I am most likely capable of randomly shouting ‘Electricity!’” (2002, 138)), the poet never gives in to the double affirmation that would eventually risk the “element of pleasure in discourse.” (2002, 80)” It is exactly because the gap of the antinomies is so vast that poetry is not meant to be written with a hammer. Neither does writing consist in a reevaluation of those elements. In short, poetry is not an affirmation of difference, but the surprising beauty of chiming antinomies. We might never transcend them, but it is up to us to put them together. Yet again, this voisinage is not to be identified with the necessity of chance as an eternal return.4 On the contrary it is a return from that very return : Let us treat Yes as a No to No and No as a Yes […] And let us not forget that this pissed affirmation crumbled down Nietzsche’s intellect in the dark paths of this world. (2002, 88) This return from the “vicious circle” should in no way be taken as a form of artistic prudence. Rather it can be seen as a dribble of demonic inconsistency as Dionysus transforms himself into a Christ that is in turn de-theologized: “Who can forbid that? Every man is capable of his own theology, nothing can stop him.” (2002, 73-74) This is a turn towards an existential vision of the world, historically coinciding with a particular political defeat of the Left, to which the poet devoted all his life: after the defeat of the popular front I raised the question “why do we exist?” while others were asking “why we failed.” (2002, 57)5 But most of all it is a return to poetry that exceeds the existential question itself, going beyond the issue of faith. Poetry comes in as a question of return after a defeat that is confessed in full profanity. Though it accepts the necessity of the defeat, it does not affirm it. Though it negates it, the negation is not in the name of a promise to be delivered in the kingdom of heavens. Following a historical and existential defeat, poetry is born post mortem . It signals a return to Christ as “groundless religiousness in the surprise of the real as such” (2002, 72) which is at once a return to the refuge of childhood. It is not a question of endurance towards an eternal return. Rather it is a question on the possibility of an existential return. Returning in a world as someone who cannot enjoy any returns exactly because he is averse to guarantees. A return without returns. *** PHOTOCOPY OF HAPPINESS When I was young I used to pin down cicadas and step on ant nests. I used to stand there silent for hours. With threads I decapitated bees. Now I am a dead man breathing. (Karouzos, 1993, II, 336.) The return to the “paradise of childhood” (2002, 68) constitutes the devouring refuge of its own memory when defeat becomes the synonym of adulthood. The political struggles of a young communist in a country torn up by a civil war right after World War II fraught with incarcerations and exiles. Historically they resulted in the defeat of the communist movement in Greece and opened up a long turbulent road that would peak in the dictatorship of 1967. Existentially they led to a series of disillusionments: mental breakdown, divorce, abandonment of studies in law school. To the question “why do we exist” the answer was poetry. Still this exposé should not be read as a sweeping chronography of a man. For it actually happens to coincide with the historical fate of a nation that after its modern constitution never stopped dreaming of the glories of its past youth, in a present that was (and is) sweepingly disappointing. But isn’t this return to youth finally a way of compensating for a loss of youth that necessarily results in a losing adulthood? Will Greeks, the eternal children of Plato and Nietzsche, ever learn? How to return without dying, how to remember without wasting time? WE ARE IN THE OPEN MEANING Living the coldest mauve night right across Parthenon I went to take a piss on some foliage and I was enjoying the foliage as it was steaming. (Karouzos, 1993, II, 340) Beyond the historical tragedies of modern Greece and away from any personal disappointments, the relation that this land holds with language and history is mediated through the Greek light—whose omnipresence is the very condition of its transcendence. All historical contradictions from Dionysus to Christ took place under this light; all those disseminated dialects were spoken beneath its warmth. To paraphrase Lévinas,6 light is both the condition of the world and of our withdrawal from it—a withdrawal towards the invisibility of God, of the dead, of meta-physics, resulting from the temptation that all is still here, behind this light the visibility of which they once evaded: “birds, the allurement of God.” (1993, I, 17) Under that luminous sky, if Greeks can do anything at all, it is to envision a return that will never come. All they can do is write poetry—which is doing nothing; other than lending an ear to a disseminated language whispering a unity that cannot be promised, as an adulthood in defeat is ready to recognize. Trying “to trap the invisible in visibility” (1993, II, 483) they forget that they have grown up and one day they die—with the promise of return. Hence an additional meaning must be given to this return to childhood. It does not signal salvation but rather its promise. To the ears of an aged continent it means that the return to/of poetry is a losing game, a return without returns. “Europe, Europe… you are nothing more than the continuation of Barabbas.” (1993, I, 295) *** “Life is not there to verify theories.”7 The records show that Karouzos was finally given a second-class pension from the Greek government, at the time when he was being recognized by the literary press as one of Greece’s major contemporary poets. Being neither a bourgeois nor a nobelist, he proclaimed himself to be an anarcho-communist, unconditionally faithful to the utopia of a classless society. He also drank, heavily. “Capitalism made an animal out of man/ Marxism made an animal out of truth/ Shut up.” (1993, II, 369) Perhaps one of the most scandalous divides of our times has been the one between the living and the dead, the latent prohibition that the living should not be concerned with the dead based on the mere impossibility of the dead to be concerned with the living in the first place. What adds to this scandal is that this divide abuses anything that cannot return to us by subsuming it under the same futility. Hence death is no longer “loss” in the usual sense. It no more refers to the things we lost but to our “loss” (of time, money and well-being) as we insist to dwell on them. Death is a waste —of time. It is this waste that we find in the insouciance of Greek expenditure; the waste in dealing with a language that most of its historical part is no longer spoken (a dead language); the waste in translating a poet who is ex definitio untranslatable; the waste of his vision, his money, his life. The waste of dealing with anything that cannot return and that cannot bring in any returns . But it is also the waste of life that poetry itself presupposes, the waste of dealing with invisibility, with anything that is out of this world and thus invokes the fear of death that is in turn—and surprisingly— nowhere to be found. Instead of death, what is there, beyond the light, is the being without us (to recall the Lévinasian il y a ), the mumble of our own nothingness which constitutes the price to be paid for writing poetry under an evergreek light. To understand this to-and-fro, is to realize that poetry is something out of this world that nevertheless takes place in this world, by virtue of this world. But to ridiculously equate this to-and-fro with death as non-existence, is to exile poetry along with its own possibility from this same old world: I do not believe that poetry will ever disappear from this world. […] But I am also sure that it does not have many chances of playing, as you say, a redemptive role in our vertiginous technological future. Without being endangered as a creative need, it will be placed on the side of history. (2002, 32) It is mainly there that we would like to locate the meaning of Nikos Karouzos’s poetry today. If we are willing to include the Greek original it is because we consider that it will be both a waste of time for us to do so (since most of you cannot read Greek) and because it might induce you to the even larger waste of learning it. We would additionally be glad if this small introduction served as an equally wasteful, academically useless piece of reading, gesturing towards a taboo of investing in anything Greek—that is in anything dead among the living, in anything that will never come back and maybe was never here in the first place. This is the only way to reserve for ourselves the possibility of poetry and preserve the light of its promise. “To return: that is the miracle.” (1993, I, 17) Athens, Greece July 10, 2011 NOTES 1 “ Capitale (a Late Latin word based on caput “head”) emerged in the twelfth to thirteenth centuries in the sense of funds, stock of merchandise, sum of money or money carrying interest.[…] The word and the reality it stood for appear in the sermons of St. Bernardino of Siena (1380-1444) ‘… quamdam seminalem rationem lucrosi quam communiter capitale vocamus ’, ‘that prolific cause of wealth that we commonly call capital’” (Braudel, 1992, 232-233). 2 “A great man – a man whom nature has constructed and invented in the grand style – what is he? First : there is a long logic in all of his activity, hard to survey because of its length, and consequently misleading; he has the ability to extend his will across great stretches of his life and to despise and reject everything petty about him, including even the fairest, ‘divinest’ things in the world.” (Nietzsche, 1968, 505, §962) 3 Cf. Deleuze, 1986, 186-9. 4 “Return is the being of becoming, the unity of multiplicity, the necessity of chance: the being of difference as such or the eternal return.” (Deleuze, 189)5 In this 1982 interview Karouzos refers to the defeat of the communist movement in Greece after the civil war of 1946-1949 between the Governmental Army and the Democratic Army of Greece, the military division of the Greek communist party. Karouzos’s father was a member of the communist National Liberation front (EAM) members of which formed the mainl resistance movement (ELAS) in Greece during WWII. The poet was a member of the United Panhellenic Organization of Youth (EPON), which was a youth division of EAM. After the end of the war, ELAS was called to disarmament in view of the formation of a National Army. The members of EAM resigned from the government of national unity and a series of protests led to a 3 year civil war between ELAS and the Government Army. After the defeat of ELAS the Communist party was outlawed and many communists were exiled in deserted Greek islands. Karouzos, who took action in the Greek resistance and was active during the Greek civil war, was exiled in Icaria on 1947 and in Makronisos on 1953 where he was called two years earlier to do his military service. 6 “Existence in the world qua light, which makes desire possible, is then, in the midst of being, the possibility of detaching oneself from being. To enter into being is to link up with objects; it is in effect a bond that is already tainted with nullity. It is already to escape anonymity. In this world where everything seems to affirm our solidarity with the totality of existence, where we are caught up in the gears of a universal mechanism, our first feeling, our ineradicable illusion, is a feeling or illusion of freedom. To be in the world is this hesitation, this interval in existing, which we have seen in the analyses of fatigue and the present.” (Lévinas, 1988,43-4) 7from a TV interview. THE POETRY OF NIKOS KAROUZOS From Redwriter [ Ερυθρογρ?φος ], in Collected Works, Vol . II, Athens: Ikaros. 1993, 463-4. [Athens: Apopeira, 1990, 9-10.] JESUS ANTI-OEDIPUS* Why were we once saving till the fifth day the Paschal lamb? The scriptures say: with this victim’s meat we ought to cleanse all of our senses. To give life to the whitest wave miraculous odors in the extension of the chest. Ideals to death. For us to witness the illustrious dawns of Absinthe and for the soul to be a deeply carved ornament on the fore we named will. Then many deer running amidst the evergreen growth with watery hymns, then, the unintended angels descending with heights spiraling in their momentum offer themselves to the luminous Adventure. Whence the need for speech and our sufferings covered with flags like the glorified dead. An incorporeal finger pointing at the flamboyant and fragrant holocausts within the tired horizons and the exhausted breadths with joys of the mistletoe on fire and shivering all of the green-leaved love. Something would have chirped again had we not driven it away— maybe the ewe’s grass. Something would have called us to the eternal resurrection— maybe the grace of spring. But now our heart is fiercely blinded, withdrawn to the appearances of Hades. Silence and ice incessantly cover the Infant Spirit in thatched times. While the cherry trees are dreaming faintly glowing in absolute darkness there’s nothing the Babylonians can contemplate in labs with automatic colored lights. How to rejoice now in the fifth day of the lamb? We have forked the stars. We’ve gradually become supposedly sublime with plucked chimeras in our hands. Avenged relentlessly by science. *Though the poem appears in a 1990 collection, it was actually written in 1968. Hence the reader must be aware in not associating Karouzos’ Anti-Oedipus with the famous 1972 work of Deleuze and Guattari, given that the former precedes the latter. ΙΗΣΟΥΣ ΑΝΤΙ-ΟΙΔΙΠΟΥΣ Γιατ? κρατο?σαμε κ?ποτε ?ς την π?μπτη μ?ρα το πασχαλιν? πρ?βατο; Τα κε?μενα λ?νε: μ’ αυτο? του θ?ματος το κρ?ας ?πρεπε να καθαρ?σουμε ?λες τις αισθ?σεις. Για να δ?σουμε κ?μα στη ζω? λευκ?τατο θαυμ?σιες ευωδι?ς στην ?κταση του στ?θους. Ιδανικ? στο χ?ρο. Για να βλ?πουμε τα λαμπρ? χαρ?ματα του ?ψινθου και να ’ναι η ψυχ? στ?λισμα βαθυχ?ρακτο της πλ?ρης που την ε?παμε θ?ληση. Τ?τε πολλ?ς δορκ?δες τρ?χοντας αν?μεσα στην καταπρ?σινη φ?ση με τους υδ?τινους ?μνους, τ?τε, κατεβα?νοντας οι αθ?λητοι ?γγελοι με κυλινδο?μενο το ?ψος στην ορμ? τους χαρ?ζονται της αστραφτερ?ς Περιπ?τειας. ?θεν η μιλι? γι’ αυτ? χρει?ζεται και τα δειν? σκεπ?ζονται ωσ?ν τους τιμημ?νους νεκρο?ς με σημα?ες. Ασ?ματο δ?χτυλο δε?χνει τα φλογ?δη και μοσχοβ?λα ολοκαυτ?ματα στους κουρασμ?νους ορ?ζοντες στα εξουθενωμ?να πλ?τη καθ?ς αν?βουν οι χαρ?ς του νερα?δ?ξυλου και τρ?μει ολ?κληρη η πρασιν?φυλλη αγ?πη. Κ?τι θα κελαηδο?σε π?λι αν δεν το δι?χναμε— μπορε? της προβατ?νας το χορτ?ρι. Κ?τι θα μας καλο?σε στην απ?ραντη αν?σταση— μπορε? του ?αρος η χ?ρη. Μα η καρδι? μας ?γρια τυφλ?θηκε π?ρασε στα φαιν?μενα του ?δη. Σιγ? και π?γος αδι?κοπα σκεπ?ζει στους αχυρ?νιους καιρο?ς το Ν?πιο Πνε?μα. Την ?ρα που ονειρε?ονται οι βυσσινι?ς και λ?μπουν αμυδρ? μεσ’ στο απλ?τατο σκοτ?δι τ?ποτα δε στοχ?ζονται οι βαβυλ?νιοι στα εργαστ?ρια με τ’ αυτ?ματα χρωματιστ? φ?τα. Π?ς να χαρο?με πια την π?μπτη μ?ρα του προβ?του; Φουρκ?σαμε τ’ αστ?ρια. Γ?ναμε σιγ?-σιγ? δ?θεν υπ?ροχοι με μαδημ?νες χ?μαιρες στα χ?ρια. Μας ν?μεται σκληρ? η επιστ?μη. From: Redwriter [Ερυθρογρ?φος], in Collected Works, Vol. II, Athens: Ikaros. 1993, 472. [Athens: Apopeira, 1990, 18.] DIALECTΙCS OF SPRING Christ the straight angle; Christ the Pythagorean theorem. Christ the infinitesimal calculus from above the blessed Sets Christ. Christ the tessellation of massive particles Christ the zero mass. Hence we spray numbers and fields of lust. We are carabineers of diseased logic plus something— Observed means observer and Hekate The darkness luminous and light in the dark Astarte banqueters demons from today. ΔΙΑΛΕΚΤΙΚΗ ΤΟΥ ΕΑΡΟΣ Χριστ?ς η ορθ? γων?α· Χριστ?ς το πυθαγ?ριο θε?ρημα. Χριστ?ς ο απειροστικ?ς λογισμ?ς ?νωθεν ?λβια Χριστ?ς τα Σ?νολα. Χριστ?ς η ψηφιδογραφ?α στα μαζικ? σωμ?τια Χριστ?ς η μ?ζα μηδ?ν. ?ρα ψεκ?ζουμε αριθμο?ς και πεδ?α λαγνε?ας. Ε?μαστε τυφεκιοφ?ροι νοσο?σης λογικ?ς και κ?τι-- παρατηρο?μενο σημα?νει παρατηρητ?ς και Εκ?τη σκ?τος το π?μφωτο και φως εν τ? σκοτ?? η Αστ?ρτη συνδαιτημ?νες δα?μονες απ’ ?ρτι. From: Redwriter [Ερυθρογρ?φος], Athens: Apopeira, 1990, 18. [1993, II, 472]. CREDO (as we are used to say in Latin) Α I believe in one Poet expelled from heavens / fugitive from the god and vagabond, Empedocles / and here on earth / exile on the earth etc. of Baudelaire /. Β I believe in one Computer inside thunder and through matter. Γ Suffering undefiled / substantive / the Poet uplifts himself slow-burning suicidal implying lengthy sleeps. Δ Cutting down on prospective mistakes. Ε Of all things visible and invisible officiating the onion-peelings. Ζ The Poet has nothing / see the departed /. Η I believe in one Poet that says: madness I enjoy; he ridicules existence; let me light up from my mana. Θ Syntax he doesn’t care about when musicality commands him. Along with still more licenses, and Ts are played according to the concept sound anywhere. E.g. the winters here, he winters there; it will not come—I will not rest, etc. etc. Ι The Poet exercises thought until it’s stripped down. Κ And if he’s Greek he must always study the fineness of Attica, in light, mountains, fields and sea. For this fineness teaches language. Λ And if he’s deeply destined the Poet expresses the unexplainable of the explained; he happens to be a rightful heir to the scientist and his predecessor. Μ On the froth he does not last; the Poet blusters at the bottom of the pot. Ν Flamebred and never redeemed. Ξ The Poet must sometimes say: what a consumption of presence — be a bit lonely for a change! Ο The Poet is twilit. Π He is susceptible of deaths and resurrections. Ρ He looks from the corner of his eye and exists in a glance. Σ He follows behind the mother. Τ Eveningless when it comes to age. Υ I believe in one Poet who says: let the purities coincide. Until the Corinth of the Universe or even further. Φ In a higher despair. Χ In a brighter quintessence. Ψ In one sensation that lifts off. Ω Forgiving everyone. CREDO (ως ε?θισται να λ?με λατινιστ?) Α Πιστε?ω εις ?να Ποιητ?ν εκτ?ς ουρανο? / φυγ?ς θε?θεν και αλ?της, Εμπεδοκλ?ς / και επ? της γης / εξ?ριστος π?νω στη γη κ.λπ. του Βωδελα?ρου /. Β Πιστε?ω εις ?να Υπολογιστ?ν εντ?ς κεραυνο? και δια της ?λης. Γ Υποφ?ροντας ?χραντα / ουσιαστικ?ν / ο Ποιητ?ς ανατε?νεται βραδυφλεγ?ς αυτ?χειρας εξυπακο?οντας πολ?ωρους ?πνους. Δ Τα υποψ?φια λ?θη λιγοστε?οντας. Ε Ορατ?ν τε π?ντων και αορ?των ιερουργ?ντας την αποκρομμ?ωση. Ζ Ο Ποιτ?ς ?χει τ?ποτα / βλ?πε τους αναχωρ?σαντες /. Η Πιστε?ω εις ?να Ποιητ?ν που λ?ει: η τρ?λα μ’ αρ?σει· γελοιοποιε? την ?παρξη· ας αν?ψω απ’ τη μ?να μου. Θ Συνταχτικ? δεν το γνοι?ζεται στην προσταγ? της μουσικ?τητας. Μαζ? και μ’ ?λλες ακ?μη λευτερι?ς, και τα νυ πα?ζονται κατ? την ?ννοια ?χος οπουδ?ποτε. Π.χ. τον χειμ?να εδ?, το χειμ?να εκε?· δε θ? ’ρθει – δεν θα καταλαγι?σουμε, κ. λπ. κ.λπ. Ι Ο Ποιητ?ς γυμν?ζει τη σκ?ψη σε απογ?μνωση. Κ Κι αν ε?ναι ?λληνας οφε?λει να σπουδ?ζει π?ντοτε της Αττικ?ς τη λεπτ?τητα, σε φως, βουν?, χωρ?φια και θ?λασσα. Διδ?σκει γλ?σσα η λεπτ?τητα το?τη. Λ Κι αν ε?ναι βαθι? πεπρωμ?νος ο Ποιητ?ς εκφρ?ζει το ανεξ?γητο του εξηγητο?· τυγχ?νει ν?μιμος δι?δοχος του επιστ?μονα και προκ?τοχ?ς του. Μ Στον αφρ? δεν ?χει δι?ρκεια· στο πατοκ?ζανο μα?νεται ο Ποιητ?ς. Ν Φλογοδ?αιτος και ποτ? ξελυτρωμ?νος. Ξ Ο Ποιητ?ς κ?ποτε πρ?πει να λ?ει: μεγ?λη καταν?λωση παρουσ?ας – γενε?τε και λ?γο μοναξι?ρηδες! Ο Ο Ποιητ?ς ε?ναι αμφ?φλοξ. Π Επιδ?χεται θαν?τους και αναστ?σεις. Ρ Ακροθωρ?ζει και υπ?ρχει σε ξαφνοκο?ταγμα. Σ Ε?ναι ουραγ?ς της μητ?ρας. Τ Αν?σπερος απ? ηλικ?α. Υ Πιστε?ω εις ?να Ποιητ?ν που λ?ει: να συμπ?σουν οι αγν?τητες. Μ?χρι την Κ?ρινθο του Σ?μπαντος ? μακρ?τερα. Φ Σε αν?τερη απελπισ?α. Χ Σε φαειν?τερη πεμπτουσ?α. Ψ Σε μια α?σθηση που πτηνο?ται. Ω Συγχωρ?ντας τους π?ντες. From Large Sized Logic [ Λογικ? μεγ?λου σχ?ματος ], Athens: Erato, 1989, n.p. [1993, II, 521-3]. (shrink)

C.F Gauss’s computational work in number theory attracted renewed interest in the twentieth century due to, on the one hand, the edition of Gauss’s Werke, and, on the other hand, the birth of the digital electronic computer. The involvement of the U.S. American mathematicians Derrick Henry Lehmer and Daniel Shanks with Gauss’s work is analysed, especially their continuation of work on topics as arccotangents, factors of n2 + a2, composition of binary quadratic forms. In general, this strand in Gauss’s reception (...) is part of a more general phenomenon, i.e. the influence of the computer on mathematics and one of its effects, the reappraisal of mathematical exploration. (shrink)

This dissertation examines aspects of the interplay between computing and scientific practice. The appropriate foundational framework for such an endeavour is rather real computability than the classical computability theory. This is so because physical sciences, engineering, and applied mathematics mostly employ functions defined in continuous domains. But, contrary to the case of computation over natural numbers, there is no universally accepted framework for real computation; rather, there are two incompatible approaches --computable analysis and BSS model--, both claiming to (...) formalise algorithmic computation and to offer foundations for scientific computing. The dissertation consists of three parts. In the first part, we examine what notion of 'algorithmic computation' underlies each approach and how it is respectively formalised. It is argued that the very existence of the two rival frameworks indicates that 'algorithm' is not one unique concept in mathematics, but it is used in more than one way. We test this hypothesis for consistency with mathematical practice as well as with key foundational works that aim to define the term. As a result, new connections between certain subfields of mathematics and computer science are drawn, and a distinction between 'algorithms' and 'effective procedures' is proposed. In the second part, we focus on the second goal of the two rival approaches to real computation; namely, to provide foundations for scientific computing. We examine both frameworks in detail, what idealisations they employ, and how they relate to floating-point arithmetic systems used in real computers. We explore limitations and advantages of both frameworks, and answer questions about which one is preferable for computational modelling and which one for addressing general computability issues. In the third part, analog computing and its relation to analogue (physical) modelling in science are investigated. Based on some paradigmatic cases of the former, a certain view about the nature of computation is defended, and the indispensable role of representation in it is emphasized and accounted for. We also propose a novel account of the distinction between analog and digital computation and, based on it, we compare analog computational modelling to physical modelling. It is concluded that the two practices, despite their apparent similarities, are orthogonal. (shrink)

The philosophy of mathematics has largely abandoned foundational studies, but is still fixated on theorem proving, logic and number theory, and on whether mathematical knowledge is certain. That is not what mathematics looks like to, say, a knot theorist or an industrial mathematical modeller. The "computer revolution" shows that mathematics is a much more direct study of the world, especially its structural aspects.

This textbook is designed for an Introduction to Proofs course organized around the themes of number and space. Concepts are illustrated using both geometric and number examples, while frequent analogies and applications help build intuition and context in the humanities, arts, and sciences. Sophisticated mathematical ideas are introduced early and then revisited several times in a spiral structure, allowing students to progressively develop rigorous thinking. Throughout, the presentation is enlivened with whimsical illustrations, apt quotations, and glimpses of mathematical history and (...) culture. Early chapters integrate an introduction to sets, logic, and beginning proof techniques with a first exposure to more advanced mathematical structures. The middle chapters focus on equivalence relations, functions, and induction. Carefully chosen examples elucidate familiar topics, such as natural and rational numbers and angle measurements, as well as new mathematics, such as modular arithmetic and beginning graph theory. The book concludes with a thorough exploration of the cardinalities of finite and infinite sets and, in two optional chapters, brings all the topics together by constructing the real numbers and other complete metric spaces. Designed to foster the mental flexibility and rigorous thinking needed for advanced mathematics, Introduction to Mathematics suits either a lecture-based or flipped classroom. A year of mathematics, statistics, or computer science at the university level is assumed, but the main prerequisite is the willingness to engage in a new challenge. (shrink)