String Theory

Comme la théorie des cordes n'a jusqu'à présent pas pu expliquer les phénomènes, il peut sembler que cela confirme l'opinion de Feyerabend selon laquelle il n'y a pas de « méthode » de la science. Et pourtant, la théorie des cordes est toujours le programme de recherche le plus actif pour la gravité quantique. Mais, par rapport à d'autres théories non falsifiables, cela a quelque chose de plus, en particulier : le langage mathématique, avec une logique claire de décoctions. Jusqu'à (...) un certain point, il peut reproduire les théories de jauge classiques et la relativité générale. Et il y a de l'espoir que dans un avenir pas trop lointain, des expériences pourront être développées pour tester la théorie. DOI: 10.13140/RG.2.2.28282.21443 . (shrink)

Le programme de recherche sur la théorie des cordes est basé sur l'hypothèse de 1930 que la relativité générale ressemble à la théorie d'un champ de spin-deux sans masse dans l'espace plat minkowskian . La quantification d'une telle théorie s'est avérée être renormalisable sans perturbation, impliquant une infinité qui ne peut être éliminée. Cette première théorie a été abandonnée jusqu'au milieu des années 1970, lorsqu'elle s'est développée en tant que théorie des cordes unidimensionnelle. Plus tard, a été développé la théorie (...) des supercordes, basé sur la supersymétrie entre les bosons et les fermions, puis est apparu d'autres versions de la théorie. Au milieu des années 1990, les scientifiques se sont concentrés sur le développement d'un programme de recherche unificateur, une théorie à onze dimensions appelée la théorie M. DOI: 10.13140/RG.2.2.32024.32000. (shrink)

Plusieurs théories unificatrices ont été proposées. Une grande unification implique l'existence d'une force électronucléaire. La dernière étape de l'unification nécessiterait une théorie qui inclue à la fois la mécanique quantique et la gravité par la relativité générale (« la théorie finale »). Après 1990, certains physiciens considèrent que la théorie M à 11 dimensions, souvent identifiée à l'une des cinq théories des supercordes perturbateurs, ou parfois à la supergravité à supersymétrie maximale supersymétrique à 11 dimensions, est la théorie finale. L'idée (...) de la théorie M s'inspire des idées de la théorie de Kaluza-Klein, dans laquelle il a été constaté que l'utilisation d'un espace-temps à 5 dimensions pour la relativité générale (une des dimensions étant petite) est vue, du point de vue à 4 dimensions, comme la relativité générale habituelle avec l'électrodynamique de Maxwell. DOI: 10.13140/RG.2.2.30364.62084. (shrink)

Întrucât teoria corzilor nu a fost până în prezent capabilă să explice fenomenele, ar putea părea că aceasta confirmă opinia lui Feyerabend că nu există o "metodă" a științei. Și totuși, teoria corzilor este în continuare cel mai activ program de cercetare pentru gravitația cuantică. Dar, față de alte teorii nefalsificabile, aceasta are ceva în plus, special: limbajul matematic, cu o logică clară a decucțiilor. Până la un punct poate reproduce teoriile clasice gauge și relativitatea generală. Și există speranța ca (...) într-un viitor nu foarte îndepărtat să se poată elabora experimente care să verifice teoria. DOI: 10.13140/RG.2.2.22843.16163. (shrink)

Since string theory has not been able to explain phenomena to date, it may seem that this confirms Feyerabend's view that there is no "method" of science. And yet, string theory is still the most active research program for quantum gravity. But, compared to other non-falsifiable theories, this has something extra, especially mathematical language, with a clear logic of deductions. Up to a point it can reproduce classical gauge theories and general relativity. And there is hope that in the not (...) too distant future experiments can be developed to test the theory. DOI: 10.13140/RG.2.2.28892.33920. (shrink)

In quantum field theory, the main obstacle is the occurrence of the untreatable infinities in the interactions of the particles due to the possibility of arbitrary distances between the point particles. Strings, as extended objects, provide a better framework, which allows finite calculations. String theory is part of a research program in which point particles in particle physics are replaced by one-dimensional objects called strings. It describes how these strings propagate through space and interact with one another. The purpose of (...) string theory was to replace elementary particles with one-dimensional strings in order to unify quantum physics and gravity. DOI: 10.13140/RG.2.2.18894.82240. (shrink)

În teoria câmpului cuantic, principalul obstacol este apariția infinităților netratabile în interacțiunile particulelor datorită posibilității unor distanțe arbitrare între particulele punctuale. Corzile, ca obiecte extinse, oferă un cadru mai bun, care permite calcule finite. Teoria corzilor face parte dintr-un un program de cercetare în care particulele punctuale din fizica particulelor sunt înlocuite de obiecte unidimensionale numite corzi. Ea descrie modul în care aceste corzi se propagă prin spațiu și interacționează una cu cealaltă. La scale de dimensiuni mai mari, o coardă (...) arată ca o particulă obișnuită, cu masa, sarcina și alte proprietăți determinate de starea vibrațională a corzii. DOI: 10.13140/RG.2.2.13066.41924. (shrink)

This paper aims to address conceptual issues concerning black holes in the context of string theory, with the aim of illuminating the ontological unification of gravity and matter, and the interpretation of cosmological models. §1 describes the central concepts of the theory: the fungibility of matter and geometry, and the reduction of gravity and supergravity. The ‘standard’ interpretation presented draws on that implicit in the thinking of many (but not all) string theorists, though made more explicit and systematic than usual. (...) §2 explains how to construct a stringy black hole, and some of its features, including evaporation. §3 critically examines the assumptions behind such modeling, and their bearing on ontological questions. (shrink)

Within the field of quantum gravity, there is an influential research program developing the connection between quantum entanglement and spatiotemporal distance. Quantum information theory gives us highly refined tools for quantifying quantum entanglement such as the entanglement entropy. Through a series of well-confirmed results, it has been shown how these facts about the entanglement entropy of component systems may be connected to facts about spatiotemporal distance. Physicists are seeing these results as yielding promising methods for better understanding the emergence of (...) (the dynamical) spacetime (of general relativity) from more fundamental quantum theories, and moreover, as promising for the development of a nonperturbative theory of quantum gravity. However, to what extent does the case for the entanglement entropy-distance link provide evidence that spacetime structure is nonfundamental and emergent from nongravitational degrees of freedom? I will show that a closer look at the results lends support only to a weaker conclusion, that the facts about quantum entanglement are constrained by facts about spatiotemporal distance, and not that they are the basis from which facts about spatiotemporal distance emerge. (shrink)

In this paper, I offer an analysis of the radical disagreement over the adequacy of string theory. The prominence of string theory despite its notorious lack of empirical support is sometimes explained as a troubling case of science gone awry, driven largely by sociological mechanisms such as groupthink (e.g. Smolin 2006). Others, such as Dawid (2013), explain the controversy by positing a methodological revolution of sorts, according to which string theorists have quietly turned to nonempirical methods of theory assessment given (...) the technological inability to directly test the theory. The appropriate response, according to Dawid, is to acknowledge this development and widen the canons of acceptable scientific methods. As I’ll argue, however, the current situation in fundamental physics does not require either of these responses. Rather, as I’ll suggest, much of the controversy stems from a failure to properly distinguish the “context of justification” from the “context of pursuit”. Both those who accuse string theorists of betraying the scientific method and those who advocate an enlarged conception of scientific methodology objectionably conflate epistemic justification with judgements of pursuit-worthiness. Once we get clear about this distinction and about the different norms governing the two contexts, the current situation in fundamental physics becomes much less puzzling. After defending this diagnosis of the controversy, I’ll show how the argument patterns that have been posited by Dawid as constituting an emergent methodological revolution in science are better off if reworked as arguments belonging to the context of pursuit. (shrink)

In this paper, I describe some strategies for teaching an introductory philosophy of science course to Science, Technology, Engineering, and Mathematics (STEM) students, with reference to my own experience teaching a philosophy of science course in the Fall of 2020. The most important strategy that I advocate is what I call the “Second Philosophy” approach, according to which instructors ought to emphasize that the problems that concern philosophers of science are not manufactured and imposed by philosophers from the outside, but (...) rather are ones that arise internally, during the practice of science itself. To justify this approach, I appeal to considerations from both educational research and the epistemology of testimony. In addition, I defend some distinctive learning goals that philosophy of science instructors ought to adopt when teaching STEM students, which include rectifying empirically well-documented shortcomings in students’ conceptions of the “scientific method” and the “nature of science.” Although my primary focus will be on teaching philosophy of science to STEM students, much of what I propose can be applied to non-philosophy majors generally. Ultimately, as I argue, a successful philosophy of science course for non-philosophy majors must be one that advances a student’s science education. The strategies that I describe and defend here are aimed at precisely that end. (shrink)

String theory reduces to general relativity in appropriate regimes. Huggett and Vistarini have given an account of this reduction that includes a deflationary thesis about symmetry: although the usual derivation of general relativity from string theory appeals to a premise about the theory’s symmetry, Huggett and Vistarini argue that this premise plays no logical role. In this article I disagree with their deflationary thesis and argue that their analysis is based on a popular but flawed conception of the interaction between (...) symmetry and quantization. I argue that a better conception recognizes a distinction between ordinary, broken, and anomalous symmetries. (shrink)

L'éternalisme, la thèse selon laquelle les entités que nous catégorisons comme étant passées, présentes et futures existent tout autant, est la meilleure approche ontologique de l'existence temporelle qui soit en accord avec les théories de la relativité restreinte et de la relativité générale. Cependant, les théories de la relativité restreinte et générale ne sont pas fondamentales si bien que plusieurs programmes de recherche tentent de trouver une théorie plus fondamentale de la gravité quantique rassemblant tous les enseignements de la physique (...) relativiste et de la physique quantique. Certaines de ces approches soutiennent que le temps n'est pas fondamental. Toutefois, si le temps n'est pas fondamental, quelles en sont les conséquences pour l'éternalisme et les débats sur l'existence dans le temps ? Premièrement, je soutiendrai que la non-fondamentalité du temps que l'on rencontre dans la théorie des cordes mène à l'éternalisme standard. Deuxièmement, je soutiendrai que la non-fondamentalité du temps rencontrée dans la gravité quantique à boucles implique l'éternalisme atemporel, à savoir une nouvelle position qui demeure fidèle à l'esprit de l'éternalisme standard. (shrink)

As a candidate theory of quantum gravity, the popularity of string theory has waxed and waned over the past four decades. One current source of scepticism is that the theory can be used to derive, depending upon the input geometrical assumptions that one makes, a vast range of different quantum field theories, giving rise to the so-called landscape problem. One apparent way to address the landscape problem is to posit the existence of a multiverse; this, however, has in turn drawn (...) heightened attention to questions regarding the empirical testability and predictivity of string theory. We argue first that the landscape problem relies on dubious assumptions and does not motivate a multiverse hypothesis. Nevertheless, we then show that the multiverse hypothesis is scientifically legitimate and could be coupled to string theory for other empirical reasons. Looking at various cosmological approaches, we offer an empirical criterion to assess the scientific status of multiverse hypotheses. (shrink)

Eternalism, the view that what we regard locally as being located in the past, the present and the future equally exists, is the best ontological account of temporal existence in line with special and general relativity. However, special and general relativity are not fundamental theories and several research programs aim at finding a more fundamental theory of quantum gravity weaving together all we know from relativistic physics and quantum physics. Interestingly, some of these approaches assert that time is not fundamental. (...) If time is not fundamental, what does it entail for eternalism and the standard debate over existence in time? First, I will argue that the non-fundamentality of time to be found in string theory entails standard eternalism. Second, I will argue that the non-fundamentality of time to be found in loop quantum gravity entails atemporal eternalism, namely a novel position in the spirit of standard eternalism. (shrink)

L'évolution des tests gravitationnels dans une perspective épistémologique encadré dans le concept de reconstruction rationnelle d'Imre Lakatos, fondée sur sa méthodologie de programmes de recherche. Contrairement à d'autres travaux sur le même sujet, la période évaluée est très longue, allant de la philosophie naturelle de Newton aux théories de la gravité quantique d'aujourd'hui. Afin d'expliquer de manière plus rationnelle l'évolution complexe du concept de gravité du siècle dernier, je propose une extension naturelle de la méthodologie des programmes de recherche que (...) j'utilisais ensuite au cours de la communication. Je pense que cette approche offre une nouvelle perspective sur la manière dont le concept de gravité et les méthodes de test de chaque théorie de la gravité ont évalué dans le temps, par le biais d'observations et d'expériences. Je soutiens, sur la base de la méthodologie des programmes de recherche et des études des scientifiques et des philosophes, que les théories actuelles de la gravité quantique sont dégénératives, en raison du manque de preuves expérimentales sur une longue période et d'auto-immunisation contre la possibilité de la réfutabilité. De plus, un courant méthodologique est en cours de développement, attribuant un rôle secondaire, sans importance, aux vérifications par le biais d'observations et / ou d'expériences. Pour cette raison, il ne sera pas possible d'avoir une théorie complète de la gravité quantique sous sa forme actuelle qui inclura à la limite la relativité générale, car les théories physiques ont toujours été ajustées, au cours de leur évolution, sur la base d'essais d'observation ou expérimentaux, et vérifiées par les prédictions effectuées. En outre, contrairement à une opinion répandue et aux programmes en cours concernant l'unification de toutes les forces fondamentales de la physique dans une théorie finale unique, basée sur la théorie des cordes, je soutiens que cette unification est généralement improbable et, de toute façon, impossible pour que l'unification soit développée sur la base des théories actuelles de la gravité quantique, y compris la théorie des cordes. En outre, je partage l’avis de certains scientifiques et philosophes selon lequel on consacre actuellement trop de ressources à l’idée de développer des théories de la gravité quantique, et en particulier de la théorie des cordes, qui devrait inclure la relativité générale et unifier la gravité avec d’autres forces, en particulier conditions dans lesquelles la science n’impose pas de tels programmes de recherche. (shrink)

My aim in this paper is twofold: to distinguish two notions of naturalness employed in beyond the standard model physics and to argue that recognizing this distinction has methodological consequences. One notion of naturalness is an “autonomy of scales” requirement: it prohibits sensitive dependence of an effective field theory’s low-energy observables on precise specification of the theory’s description of cutoff-scale physics. I will argue that considerations from the general structure of effective field theory provide justification for the role this notion (...) of naturalness has played in BSM model construction. A second, distinct notion construes naturalness as a statistical principle requiring that the values of the parameters in an effective field theory be “likely” given some appropriately chosen measure on some appropriately circumscribed space of models. I argue that these two notions are historically and conceptually related but are motivated by distinct theoretical considerations and admit of distinct kinds of solution. (shrink)

Dawid's account of non-empirical theory assessment is meant to complement traditional theory assessments. I contend that his arguments don't provide support for this account. His three arguments, the no alternatives argument, the unexpected explanatory connections argument, and the meta-inductive argument from prior theories' success, are all problematic, particularly for an assessment of string theory. In particular, I argue that the meta-inductive argument is idle, because it's role in underwriting the future predictive success of a theory is subsumed by the normal (...) accounting of its predecessor's predictions in theory growth and testing. Dawid's arguments are interdependent, so showing that one fails is sufficient to cast doubt on his entire account. (shrink)

Relationships between current theories, and relationships between current theories and the sought theory of quantum gravity (QG), play an essential role in motivating the need for QG, aiding the search for QG, and defining what would count as QG. Correspondence is the broad class of inter-theory relationships intended to demonstrate the necessary compatibility of two theories whose domains of validity overlap, in the overlap regions. The variety of roles that correspondence plays in the search for QG are illustrated, using examples (...) from specific QG approaches. Reduction is argued to be a special case of correspondence, and to form part of the definition of QG. Finally, the appropriate account of emergence in the context of QG is presented, and compared to conceptions of emergence in the broader philosophy literature. It is argued that, while emergence is likely to hold between QG and general relativity, emergence is not part of the definition of QG, and nor can it serve usefully in the development and justification of the new theory. (shrink)

It has been argued in Dawid that physicists at times generate substantial trust in an empirically unconfirmed theory based on observations that lie beyond the theory’s intended domain. A crucial role in the reconstruction of this argument of “non-empirical confirmation” is played by limitations to scientific underdetermination. The present paper discusses the question as to how generic the role of limitations to scientific underdetermination really is. It is argued that assessing such limitations is essential for generating trust in any theory’s (...) predictions, be it empirically confirmed or not. The emerging view suggests that empirical and non-empirical confirmation are more closely related to each other than one may expect at first glance. (shrink)

I will defend two claims. First, Schaffer's priority monism is in tension with many research programs in quantum gravity. Second, priority monism can be modified into a view more amenable to this physics. The first claim is grounded in the fact that promising approaches to quantum gravity such as loop quantum gravity or string theory deny the fundamental reality of spacetime. Since fundamental spacetime plays an important role in Schaffer's priority monism by being identified with the fundamental structure, namely the (...) cosmos, the disappearance of spacetime in these views might undermine classical priority monism. My second claim is that priority monism can avoid this issue with two moves: first, in dropping one of its core assumptions, namely that the fundamental structure is spatio-temporal, second, by identifying the connection between the non-spatio-temporal structure and the derivative spatio-temporal structure with mereological composition. (shrink)

A ‘duality’ is a formal mapping between the spaces of solutions of two empirically equivalent theories. In recent times, dualities have been found to be pervasive in string theory and quantum field theory. Naïvely interpreted, duality-related theories appear to make very different ontological claims about the world—differing in e.g. space-time structure, fundamental ontology, and mereological structure. In light of this, duality-related theories raise questions familiar from discussions of underdetermination in the philosophy of science: in the presence of dual theories, what (...) is one to say about the ontology of the world? In this paper, we undertake a comprehensive and non-technical survey of the landscape of possible ontological interpretations of duality-related theories. We provide a significantly enriched and clarified taxonomy of options—several of which are novel to the literature. (shrink)

This paper investigates the significance of T-duality in string theory: the indistinguisha- bility with respect to all observables, of models attributing radically different radii to space – larger than the observable universe, or far smaller than the Planck length, say. Two interpretational branch points are identified and discussed. First, whether duals are physically equivalent or not: by considering a duality of the familiar simple harmonic oscillator, I argue that they are. Unlike the oscillator, there are no measurements ‘outside’ string theory (...) that could distinguish the duals. Second, whether duals agree or disagree on the radius of ‘target space’, the space in which strings evolve according to string theory. I argue for the latter position, because the alternative leaves it unknown what the radius is. Since duals are physically equivalent yet disagree on the radius of target space, it follows that the radius is indeterminate between them. Using an analysis of Brandenberger and Vafa (1989), I explain why – even so – space is observed to have a determinate, large radius. The conclusion is that observed, ‘phenomenal’ space is not target space, since a space cannot have both a determinate and indeterminate radius: instead phenomenal space must be a higher-level phenomenon, not fundamental. (shrink)

In the author’s previous contribution to this journal (Rosen 2015), a phenomenological string theory was proposed based on qualitative topology and hypercomplex numbers. The current paper takes this further by delving into the ancient Chinese origin of phenomenological string theory. First, we discover a connection between the Klein bottle, which is crucial to the theory, and the Ho-t’u, a Chinese number archetype central to Taoist cosmology. The two structures are seen to mirror each other in expressing the psychophysical (phenomenological) action (...) pattern at the heart of microphysics. But tackling the question of quantum gravity requires that a whole family of topological dimensions be brought into play. What we find in engaging with these structures is a closely related family of Taoist forebears that, in concert with their successors, provide a blueprint for cosmic evolution. Whereas conventional string theory accounts for the generation of nature’s fundamental forces via a notion of symmetry breaking that is essentially static and thus unable to explain cosmogony successfully, phenomenological/Taoist string theory entails the dialectical interplay of symmetry and asymmetry inherent in the principle of synsymmetry. This dynamic concept of cosmic change is elaborated on in the three concluding sections of the paper. Here, a detailed analysis of cosmogony is offered, first in terms of the theory of dimensional development and its Taoist (yin-yang) counterpart, then in terms of the evolution of the elemental force particles through cycles of expansion and contraction in a spiraling universe. The paper closes by considering the role of the analyst per se in the further evolution of the cosmos. (shrink)

We give an introductory review of gauge/gravity duality, and associated ideas of holography, emphasising the conceptual aspects. The opening sections gather the ingredients, viz. anti-de Sitter spacetime, conformal field theory and string theory, that we need for presenting, in Sect. 5, the central and original example: Maldacena’s AdS/CFT correspondence. Sections 6 and 7 develop the ideas of this example, also in applications to condensed matter systems, QCD, and hydrodynamics. Sections 8 and 9 discuss the possible extensions of holographic ideas to (...) de Sitter spacetime and to black holes. Section 10 discusses the bearing of gauge/gravity duality on two philosophical topics: the equivalence of physical theories, and the idea that spacetime, or some features of it, are emergent. (shrink)

The present study explores the Bianchi type I universe in the frame work of f theory of gravity by considering strange quark matter attached to string cloud and domain walls in the presence and absence of magnetism. Field equations are solved by choosing a constant curvature method. It is found that obtained cosmological models are relevant to the early era of evolution of the universe. The strange quark matter may be a source of string cloud and domain walls.

"There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact" Mark Twain-Life on the Mississippi -/- This is a lovely book full of fascinating info on the evolution of physics and cosmology. Its main theme is how the idea of higher dimensional geometry created by Riemann, recently extended to 24 dimensions by string theory, has revolutionized our understanding of the universe. Everyone knows that Riemann created multidimensional geometry in 1854 (...) but it is amazing to learn that he also was a physicist who believed that it held the key to explaining the fundamental laws of physics. Maxwell´s equations did not exist then and Riemann´s untimely death at age 39 prevented his pursuit of these ideas. Both he and his British translator Clifford believed that magnetic and electric fields resulted from the bending of space in the 4th dimension-more than 50 years before Einstein! The fourth dimension became a standard subject in the popular media for the next 50 years with several stories by HG Wells using it and even Lenin wrote about it. The American mathematician Hinton had widely publicized his idea that light is a vibration in the 4th spatial dimension. Amazingly, physicists and most mathematicians forgot about it and when Einstein was looking for the math needed to encompass general relativity 60 years later, he had never heard of Riemannian geometry. He spent 3 years trying to find the equations for general relativity and only after a math friend told him about Riemann was he able to complete his work. Riemann´s equations with four dimensional metric tensors describing every point in space were incorporated almost unchanged into relativity. And on and on it goes. Since this review I have written a great deal on the language games of math and science, uncertainty, incompleteness, the limits of computation etc., so those interested should find them useful since this volume like most science frequently wanders across the line into philosophy (scientism). -/- Those wishing a comprehensive up to date framework for human behavior from the modern two systems view may consult my book ‘The Logical Structure of Philosophy, Psychology, Mind and Language in Ludwig Wittgenstein and John Searle’ 2nd ed (2019). Those interested in more of my writings may see ‘Talking Monkeys--Philosophy, Psychology, Science, Religion and Politics on a Doomed Planet--Articles and Reviews 2006-2019 3rd ed (2019), The Logical Structure of Human Behavior (2019), and Suicidal Utopian Delusions in the 21st Century 4th ed (2019). (shrink)

We analyse the possibility that string-theoretic dualities present a genuine case of strong underdetermination of theory by evidence. Drawing on the parallel discussion of the hole argument, we assess the possible interpretations of dualities. We conclude that there exist at least two defensible interpretations on which dualities do not present a worrying case of underdetermination per se.

The Birth of String Theory by Cappelli et al. tells the story of the beginnings of string theory and of the evolutionary process it has undergone from its origins in S-matrix theory to its current status as a candidate unification theory. The book is intended for an audience of students and researchers in physics, as well as historians and philosophers of science with some background in quantum field theory.In the 50s and early 60s, theoretical particle physics focused on formulating a (...) theory to explain the strong interactions. Due to issues with the application of perturbative quantum field theory to the strong interactions, theoretical particle physicists shifted their attention to Heisenberg’s ‘S-matrix’ theory, which focused solely on observable quantities. This endeavour led in 1968 to the breakthrough of the famous ‘Veneziano amplitude’, which along with the Dolen–Horn–Schmid duality between the s- and the t-channels led to the dual resonance model . Following Ve .. (shrink)

We present an exact solution of the one-dimensional modified Klein Gordon and Duffin Kemmer Petiau equations with a step potential in the presence of minimal length in the uncertainty relation, where the expressions of the new transmission and reflection coefficients are determined for all cases. As an application, the Klein paradox in the presence of minimal length is discussed for all equations.

Weyl symmetry of the classical bosonic string Lagrangian is broken by quantization, with profound consequences described here. Reimposing symmetry requires that the background space-time satisfy the equations of general relativity: general relativity, hence classical space-time as we know it, arises from string theory. We investigate the logical role of Weyl symmetry in this explanation of general relativity: it is not an independent physical postulate but required in quantum string theory, so from a certain point of view it plays only a (...) formal role in the explanation. (shrink)

String theory has been very influential within theoretical physics for the past few decades. It is the most popular attempt to solve the problem of formulating a viable theory of quantum gravity. Furthermore, it also unifies the other fundamental forces within one theoretical framework. In string theory, it is assumed that what before was thought to be point particles should really be seen as one-dimensional extended entities, i.e. strings. Different particles are supposed to correspond to various vibrational patterns of the (...) strings.In recent years, much critique has been directed towards string theory, and the fact that it inhabits such a strong position within the theoretical physics community. The main complaint is the complete lack of empirical confirmation of new predictions derived from string theory. The books, criticizing string theory, that have received most attention are the ones written by Smolin (2006), Woit (2006), but there are many more critics some of which express much harsher criticism towards string theory than the above-mentioned authors. (shrink)

Some philosophers of science have suggested that contemporary science should be the source of inspiration to the new analytic metaphysics (A. Chakra vartty, C. Callender, S. French, J. Ladyman, T. Maudlin, etc.). This paper explores the prospect of a string metaphysics: a research program in analytic metaphysics based on string theory. Different forms of fundamentalism and pluralism are discussed in this context. The paper focus on string metaphysics with S-dualities (a relation between models of string theory at different coupling regimes) (...) and argues that fundamentality and compositionality have to be reconceptualized. String metaphysics with dualities is better couched in terms of metaphysical pluralism. Grounding, as well as a sketch of a string modality, are briefly discussed. The paper concludes with a suggestion for future work: the metaphysician may find a productive ground for research in discussing other dualities (especially the T-dualities, or the AdS/CFT duality), the emergence of spacetime, the concept of time in string theory, the multiverse etc. (shrink)

“The confrontation between string theory and its critics,” writes Jarod Lanier, “is one of the great intellectual dramas of our age”. String theory is widely regarded by its practitioners as the only the only viable option for constructing a unified theory of gravity and elementary particle physics. It has attracted an unprecedented number of researchers, including many Nobel Laureates, and has been instrumental in opening up new areas at the intersection of mathematics and physics.. Yet, since the 1980s it has (...) been mired in controversy, and has been labelled science, speculative metaphysics, non-science, pseudoscience.. (shrink)

The PreambleIn the early seventies the newly discovered gauge symmetries had made it possible to give a unified description of three of the four basic forces in nature.Dawid [1]. However, it remained a mystery how the force of gravity was to be incorporated in the resulting standard model. In 1974 it was proposed by Joel Scherk and John Schwarz that string theory—which until then was regarded as a theory only of hadrons—was a theory that could unite the whole of microphysics. (...) The promise of full unification attracted many researchers to the field of string theory. A lot of work was done which expanded the mathematical framework and in 1984 Scherk and Schwarz finally succeeded in formulating the Lagrangian of the superstring: a quantised string that includes a matter field. With the mathematical formalism now firmly in place, the scientific community waited for experimental verification of the string hypothesis. And it waited.The Current DebateToday, more than 40 years after the earlies. (shrink)

The early history of the attempts to unify quantum theory with the general theory of relativity is depicted through the work of the under--appreciated Italo-Brazilian physicist Gleb Wataghin, who is responsible for many of the ideas that the quantum gravity community is entertaining today.

It is put forward that modern elementary particle physics cannot be completely unified with the laws of gravity and general relativity without addressing the question of the ontological interpretation of quantum mechanics itself. The position of superstring theory in this general question is emphasized: superstrings may well form exactly the right mathematical system that can explain how quantum mechanics can be linked to a deterministic picture of our world. Deterministic interpretations of quantum mechanics are usually categorically rejected, because of Bell’s (...) powerful observations, and indeed these apply here also, but we do emphasize that the models we arrive at are super-deterministic, which is exactly the case where Bell expressed his doubts. Strong correlations at space-like separations could explain the apparent contradictions. (shrink)

String theory has played a highly influential role in theoretical physics for nearly three decades and has substantially altered our view of the elementary building principles of the Universe. However, the theory remains empirically unconfirmed, and is expected to remain so for the foreseeable future. So why do string theorists have such a strong belief in their theory? This book explores this question, offering a novel insight into the nature of theory assessment itself. Dawid approaches the topic from a unique (...) position, having extensive experience in both philosophy and high-energy physics. He argues that string theory is just the most conspicuous example of a number of theories in high-energy physics where non-empirical theory assessment has an important part to play. Aimed at physicists and philosophers of science, the book does not use mathematical formalism and explains most technical terms. (shrink)

String theory has by now maintained a highly influential position in high energy physics for more than a quarter of a century. The present article analyses the reasons for the considerable trust exponents of string theory have in their theory even though it has neither found empirical confirmation nor a complete formulation up to this point. It is argued that this trust can be understood in terms of an emerging new conception of theory assessment that relies strongly on the identification (...) of limitations to the underdetermination of scientific theory building. The second part of the paper makes the point that another conspicuous element of string theoretical reasoning, the prominent role of the notion of a final theory, can be understood in terms of this altered notion of theory assessment as well. (shrink)