I argue that Deutsch’s model for the behavior of systems traveling around closed timelike curves relies implicitly on a substantive metaphysical assumption. Deutsch is employing a version of quantum theory with a significantly supplemented ontology of parallel existent worlds, which differ in kind from the many worlds of the Everett interpretation. Standard Everett does not support the existence of multiple identical copies of the world, which the D-CTC model requires. This has been obscured because he often refers to the branching (...) structure of Everett as a “multiverse”, and describes quantum interference by reference to parallel interacting definite worlds. But he admits that this is only an approximation to Everett. The D-CTC model, however, relies crucially on the existence of a multiverse of parallel interacting worlds. Since his model is supplemented by structures that go significantly beyond quantum theory, and play an ineliminable role in its predictions and explanations, it does not represent a quantum solution to the paradoxes of time travel. (shrink)

Osiurak and Reynaud highlight the critical role of technical-reasoning skills in the emergence of human cumulative technological culture, in contrast to previous accounts foregrounding social-reasoning skills as key to CTC. We question their analysis of the available evidence, yet for other reasons applaud the emphasis on causal understanding as central to the adaptive and collaborative dynamics of CTC.

A recent paper from Brun et al. has argued that access to a closed timelike curve would allow for the possibility of perfectly distinguishing nonorthogonal quantum states. This result can be used to develop a protocol for instantaneous nonlocal signaling. Several commenters have argued that nonlocal signaling must fail in this and in similar cases, often citing consistency with relativity as the justification. I argue that this objection fails to rule out nonlocal signaling in the presence of a CTC. I (...) argue that the reason these authors are motivated to exclude the prediction of nonlocal signaling is because the No Signaling principle is considered to a fundamental part of the formulation of the quantum information approach. I draw out the relationship between nonlocal signaling, quantum information, and relativity, and argue that the principle theory formulation of quantum mechanics, which is at the foundation of the quantum information approach, is in tension with foundational assumptions of Deutsch’s D-CTC model, on which this protocol is based. (shrink)

The D-CTC condition, introduced by David Deutsch as a condition to be fulfilled by analogues for processes of quantum systems in the presence of closed timelike curves, is investigated for classical statistical bi-partite systems. It is shown that the D-CTC condition can generically be fulfilled in classical statistical systems, under very general, model-independent conditions. The central property used is the convexity and completeness of the state space that allows it to generalize Deutsch’s original proof for q-bit systems to more general (...) classes of statistically described systems. The results demonstrate that the D-CTC condition, or the conditions under which it can be fulfilled, is not characteristic of, or dependent on, the quantum nature of a bi-partite system. (shrink)

In this paper I argue that the consistency condition from the Deutsch's influential model for closed timelike curves differs significantly from the classical consistency condition found in Lewis and Novikov, as well as from the consistency condition found in the P-CTC model, the major rival to Deutsch's approach. Both the CCC and the P-CTC consistency condition are formulable in the context of a single history of the world. Deutsch's consistency condition relies on the existence of a structure of parallel worlds. (...) I argue that Deutsch's commitment to realism about parallel worlds puts his solutions to the information paradox in jeopardy. I argue that, because of Deutsch's commitment to this metaphysical picture, he is committed to the existence of physical situations that are in every way indistinguishable from the paradoxes he attempts to rule out by adopting the model in the first place. Deutsch's proposed solution to the Knowledge Paradox, in particular his commitment to the actuality of the many worlds of the Everett interpretation, guarantees the existence of worlds that are indistinguishable from worlds in which the genuine Knowledge Paradox arises. (shrink)

To support their claim for technical reasoning skills rather than imitation as the key for cumulative technological culture, Osiurak and Reynaud argue that chimpanzees can imitate mechanical actions, but do not have CTC. They also state that an increase in working memory in human evolution could not have been a key driver of CTC. We discuss why we disagree with these claims.

This abstract presents a novel brain-computer interface (BCI) framework to control a prosthetic leg, for the rehabilitation of patients suffering from locomotive disorders, using functional near-infrared spectroscopy (fNIRS). fNIRS signals corresponding to walking intention and rest are used to initiate and stop the gait cycle and a nonlinear proportional derivative computed torque controller (PD-CTC) with gravity compensation is used to control torques of hip and knee joints for minimization of position error. The brain signals of walking intention and rest tasks (...) are acquired from primary motor cortex in the left hemisphere for nine subjects. After acquiring brain signals, in order to remove motion artifacts and physiological noises, the performance of six different filters i.e. Kalman, Wiener, Gaussian, hemodynamic response filter (hrf), Band-pass and finite impulse response, is evaluated. Afterwards, six different features are extracted from oxygenated hemoglobin signals and their different combinations were used for classification. The classification performance of five different classifiers i.e. artificial neural network, quadratic discriminant analysis, linear discriminant analysis (LDA), Naïve Bayes and support vector machine (SVM) is used. The classification accuracies obtained from SVM using hrf filter are significantly higher (p < 0.005) than the other combinations of classifier and filters. These accuracies are 77.5%, 72.5%, 68.3%, 74.2%, 73.3%, 80.8%, 65%, 76.7%, and 86.7% for all nine subjects. The control commands generated using classifier initiate and stop the gait cycle of the prosthetic leg whose knee and hip torques are controlled using PD-CTC to minimize position error. The proposed scheme can be effectively used for neurofeedback training and rehabilitation of lower limb amputation of paralyzed patients. (shrink)

Cumulative technological culture (CTC) refers to the increase in the efficiency and complexity of tools and techniques in human populations over generations. A fascinating question is to understand the cognitive origins of this phenomenon. Because CTC is definitely a social phenomenon, most accounts have suggested a series of cognitive mechanisms oriented toward the social dimension (e.g., teaching, imitation, theory of mind, and metacognition), thereby minimizing the technical dimension and the potential influence of non-social, cognitive skills. What if we have failed (...) to see the elephant in the room? What if social cognitive mechanisms were only catalyzing factors and not thesufficient and necessaryconditions for the emergence of CTC? In this article, we offer an alternative, unified cognitive approach to this phenomenon by assuming that CTC originates in non-social cognitive skills, namely technical-reasoning skills which enable humans to develop the technical potential necessary to constantly acquire and improve technical information. This leads us to discuss how theory of mind and metacognition, in concert with technical reasoning, can help boost CTC. The cognitive approach developed here opens up promising new avenues for reinterpreting classical issues (e.g., innovation, emulation vs. imitation, social vs. asocial learning, cooperation, teaching, and overimitation) in a field that has so far been largely dominated by other disciplines, such as evolutionary biology, mathematics, anthropology, archeology, economics, and philosophy. (shrink)

Closed timelike curves (CTCs) appear in many solutions of the Einstein equation, even with reasonable matter sources. These solutions appear to violate causality and so are considered problematic. Since CTCs reflect the global properties of a spacetime, one can attempt to extend a local CTC-free patch of such a spacetime in a way that does not give rise to CTCs. One such procedure is informally known as unwrapping. However, changes in global identifications tend to lead to local effects, and unwrapping (...) is no exception, as it introduces a special kind of singularity, called quasi-regular. This “unwrapping” singularity is similar to the string singularities. We define an unwrapping of a (locally) axisymmetric spacetime as the universal cover of the spacetime after one or more of the local axes of symmetry is removed. We give two examples of unwrapping of essentially 2+1 dimensional spacetimes with CTCs, the Gott spacetime and the Gödel spacetime. We show that the unwrapped Gott spacetime, while singular, is at least devoid of CTCs. In contrast, the unwrapped Gödel spacetime still contains CTCs through every point. A “multiple unwrapping” procedure is devised to remove the remaining circular CTCs. We conclude that, based on the given examples, CTCs appearing in the solutions of the Einstein equation are not simply a mathematical artifact of coordinate identifications. Alternative extensions of spacetimes with CTCs tend to lead to other pathologies, such as naked quasi-regular singularities. (shrink)

I wish to discuss a supposed implication of one sort of time travel. The sort of time travel is time travel into one’s past along a closed timelike curve. The implication is that in spacetimes with CTCs there can be no temporal passage or “flow” of time. I will argue that the implication does not hold.

This chapter explores the concept of time itself, as physicists understand it. Einstein's special theory of relativity requires worldlines of physical objects to be timelike; the field equations of his general theory of relativity predict that massive bodies such as stars and black holes distort space‐time and bend worldlines. Suppose space‐time becomes so distorted that some worldlines form closed loops. If one tried to follow such a closed timelike curve (or CTC) exactly, all the way around, one would bump into (...) ones former selves and get pushed aside. But by following part of a CTC, we could return to the past and participate in events there. According to a recent calculation by J. Richard Gott of Princeton, a cosmic string passing rapidly by another would generate CTCs. The chapter concludes that if time travel is impossible, then the reason has yet to be discovered. (shrink)

We investigate Kerr–Newman black holes in which a rotating charged ring-shaped singularity induces a region which contains closed timelike curves (CTCs). Contrary to popular belief, it turns out that the time orientation of the CTC is oppo- site to the direction in which the singularity or the ergosphere rotates. In this sense, CTCs “counter-rotate” against the rotating black hole. We have similar results for all spacetimes sufficiently familiar to us in which rotation induces CTCs. This motivates our conjecture that perhaps (...) this counter-rotation is not an accidental oddity particular to Kerr–Newman spacetimes, but instead there may be a general and intuitively comprehensible reason for this. (shrink)

There is an internal connection between ecclesiology, the teaching about the Church that we call academic ecclesiology, and mission, which is the inner heart of the Church and becomes visible through different practices. For the Orthodox Church involved in the ecumenical movement, there is a struggle to balance ecclesiology (theology) with ecumenical mission and dialogue (practice) in a divided Christian world. Nevertheless, the recent Synod of Crete (June 2016) addressed some important elements of this struggle. I have in mind, for (...) example, the act to accept the historical name of other non-Orthodox Christian Churches and Confessions that are not in communion with it. Also, this is the first Synod of the Orthodox Churches in modern times at which ecumenical dialogue, especially in the World Council of Churches, is officially affirmed. Because of mission dialogue has to continue, “if we wish never to ‘put an obstacle in the way of the gospel of Christ’ (1 Cor 9:12).” The present paper highlights those statements of the Holy and Great Council which have direct relevance for discussing the relation of ecclesiology and mission. I assert that we should understand firstly the document Relations of the Orthodox Church with the Rest of the of the Christian World and only then reflect upon The Mission of the Orthodox Church in Today’s World (MOCT). Furthermore, I will make some references to the other texts which were central for this conference: The Cape Town Commitment (CTC), Together Towards Life (TTL) and Apostolic Exhortation Evangelii Gaudium (EG). I conclude by exposing briefly my reflections after reading these mission documents and by formulating some agenda points for further work in theology of mission. (shrink)

Incidental fndings of potential medical signifcance are seen in approximately 5-8 percent of asymptomatic subjects and 16 percent of symptomatic subjects participating in large computed tomography colonography studies, with the incidence varying further by CT acquisition technique. While most CTC research programs have a well-defned plan to detect and disclose IFs, such plans are largely communicated only verbally. Written consent documents should also inform subjects of how IFs of potential medical signifcance will be detected and reported in CTC research studies.

In this article, I shall present three arguments for thc pcrmissibility 0f physician-assisted suicide (PAS), and then examine several objections 0f 21 "K21nti2m" and non-Kantian nature against them. These are really 0bjcctions against certain types of suicide. I shall focus 0n active PAS (eg., when 21 patient takes 21 lethal drug given by E1 physician, in which case both thc physician and patient are active). I shall assume the patient is 21 competent, responsible, rational agent, who gives his being in (...) physical discomfort (pain, nausea, ctc.) as thc reason for intending his death. I am assuming, therefore, thc pain while 21 sourcc of suffering docs not undermine his rational agency in 21 way that threatens responsibility for choice.] Current legal proposals for permitting PAS focus 0n procedures.. (shrink)

We examine the time discontinuity in rotating space–times for which the topology of time is S1. A kinematic restriction is enforced that requires the discontinuity to be an integral number of the periodicity of time. Quantized radii emerge for which the associated tangential velocities are less than the speed of light. Using the de Broglie relationship, we show that quantum theory may determine the periodicity of time. A rotating Kerr–Newman black hole and a rigidly rotating disk of dust are also (...) considered; we find that the quantized radii do not lie in the regions that possess CTCs. (shrink)

Coleridge, Mark Many thanks indeed, Master, for your words of welcome. When I was in your position, I never thought I'd be back to give the Knox Lecture. But I was pleased to be invited and glad that I was able to accept, and I'm delighted to be back among the community of Catholic Theological College. I had a hand in designing the new college in East Melbourne, but I never had the chance to work there. So it's good to (...) be back-at least close by-after all these years during which so much water has flowed beneath the bridge. It's also good to honour the memory of Cardinal James Knox, founder of CTC, and to pray that he will find eternal rest beyond the travails of this life, both in Melbourne and beyond. (shrink)

I argue against counterfactual theories of causation , develop a pragmatic version of the Covering Law view, and offer a causal theory of counterfactuals. ;The initial idea of CTCs is that event a causes event b if b would not have occurred, if a had not occurred. David Lewis proposes this view as a solution to problems of "effects" and "epiphenomena". I argue that CTCs cannot solve these problems. Covering Law theories can, but only by rejecting traditional Humean accounts of (...) laws. ;Following Nancy Cartwright , I argue that there is no a priori route from probabilistic association to causal relevance, and that distinguishing causal relevance from mere association requires further causal knowledge. Some recent literature on causal modelling is also examined. ;Much causal knowledge concerns rough, approximate ceteris paribus laws and generalizations. I examine these and argue that they involve important pragmatic components. ;Many aspects of intuitive causal judgment and reasoning are explained by ceteris paribus causes. For example, many causes are preventable, and only ceteris paribus causes could be prevented. Ceteris paribus causes are capacities, which make similar contributions to different circumstances, and interact with each other . The pragmatic features of ceteris paribus laws hold equally of ceteris paribus causes. ;Singular and generic causes are unified by appeal to the a posteriori impossibility of "action at a distance". The locality of causal relations requires that causes act by continuous intervening processes. Singular causes and effects are instances of generic causal process types. ;Numerous cases of unclear and conflicting intuitions about causes and effects are explained by contextual factors . ;I explain away the attraction of CTCs by offering a causal account of counterfactuals. It is natural to express causal facts using counterfactuals because the truth conditions of counterfactuals are direct consequences of causal facts. (shrink)

The physical possibility of spacetimes containing closed timelike curves (CTCs) challenges the philosophy of time in the way that temporal ordering is, at best, remarkably non-standard: events on CTCs precede themselves. Apparently, such universes do not possess a consistent time order but only a consistent time direction. Thus, temporal directionality seems to be more fundamental than ordering in earlier-later or past-present-future. I will argue that this favors presentism as the adequate ontology of spacetimes: only presentism consistently copes with the idea (...) that temporal ordering depends on empirical constraints. The presentist Now is fundamentally undivided and productively directed towards existence. Time order arises by extending the Now, which can fail and in fact fails in universes containing CTCs. (shrink)

We discuss the possibility to build and operate a time machine, a device that produces closed timelike curves. We specify the spacetime structure needed to implement a time machine and assess attempted no-go results against time machines in classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and in Euclidean quantum gravity. Such no-go theorems for time machines would show that, under physically reasonable conditions, CTCs cannot develop in spacetimes initially free of these pathologies. Our review indicates (...) that an investigation of the prospects of achieving no-go results has not been entirely successful in establishing such generality. At the same time, the pursuit of chronology protection results has proved to be a fruitful way to probe the foundations of classical GTR and the interface between general relativity and quantum field theory. (shrink)

The debate on cumulative technological culture is dominated by social-learning discussions, at the expense of other cognitive processes, leading to flawed circular arguments. I welcome the authors' approach to decouple CTC from social-learning processes without minimizing their impact. Yet, this model will only be informative to understand the evolution of CTC if tested in other cultural species.

Causality violations are typically seen as unrealistic and undesirable features of a physical model. The following points out three reasons why causality violations, which Bonnor and Steadman identified even in solutions to the Einstein equation referring to ordinary laboratory situations, are not necessarily undesirable. First, a space-time in which every causal curve can be extended into a closed causal curve is singularity free—a necessary property of a globally applicable physical theory. Second, a causality-violating space-time exhibits a nontrivial topology—no closed timelike (...) curve (CTC) can be homotopic among CTCs to a point, or that point would not be causally well behaved—and nontrivial topology has been explored as a model of particles. Finally, if every causal curve in a given space-time passes through an event horizon, a property which can be called “causal censorship”, then that space-time with event horizons excised would still be causally well behaved. (shrink)

It is claimed that unacceptable constraints on initial data are imposed by certain responses to paradoxes that threaten time travel, closed timelike curves (CTCs) and other backwards causation hypotheses. In this paper I argue against the following claims: to say “contradictions are impossible so something must prevent the paradox” commits in general to constraints on initial data, that for fixed point dynamics so-called grey state solutions explain why contradictions do not arise, and the latter have been proved to avoid constraints (...) on initial data. †To contact the author, please write to: Philosophy, University of Queensland, Brisbane, Queensland 4072, Australia; e-mail: [email protected]. (shrink)

BackgroundAdolescents living with human immunodeficiency virus (HIV) experience challenges, including lack of involvement in their care as well nondisclosure of HIV status, which leads to poor adherence to antiretroviral therapy (ART). Parents have authority over their children, but during adolescence there is an increasing desire for independence. The aim of the study was to explore adolescents’ experience of challenges identified by adolescents ages 10–19 years attending HIV care and treatment at Temeke Regional Referral Hospital in Tanzania. MethodsAn exploratory descriptive qualitative (...) design was employed in the HIV Care and Treatment Centre (CTC) in the Out-Patient Department at the Temeke Regional Referral Hospital in Tanzania with adolescents living with HIV who were 10–19 years of age. A total of 22 adolescents participated in semi-structured face-to-face interviews after parental consent and adolescent assent were obtained. Participants were interviewed about their participation in decisions to be tested for HIV and enrolled in the CTC, concerns surrounding disclosure of their HIV status to the adolescent or to others, stigma and discrimination, and the effect of these challenges on their adherence to medication. All interviews were audio-taped, transcribed verbatim in Swahili, and back-translated to English. Data analysis included both inductive and deductive thematic analysis.ResultsQualitative themes identified included lack of participation in decisions about HIV testing, challenges to enrollment in care and treatment; issues around disclosure of HIV status, such as delays in disclosure to the adolescent and disclosure to other persons and benefits and harms of such disclosures; and factors supporting and interfering with adherence to ART, such as parental support, organizational (clinic) support and problems, and self-stigmatization and shame.ConclusionLack of adolescents’ involvement in their care decision making and delayed disclosure of HIV status to the adolescent were identified concerns, leading to poor adherence to ART among adolescents. Disclosure to others, especially teachers, helped adolescents at school to take their medication properly. Disclosure to others led to stigma and discrimination for some adolescents. More research is needed to better understand the role of disclosure and its benefits and challenges for HIV-positive adolescents in Tanzania. (shrink)

The accurate recognition of speech is beneficial to the fields of machine translation and intelligent human–computer interaction. After briefly introducing speech recognition algorithms, this study proposed to recognize speech with a recurrent neural network (RNN) and adopted the connectionist temporal classification (CTC) algorithm to align input speech sequences and output text sequences forcibly. Simulation experiments compared the RNN-CTC algorithm with the Gaussian mixture model–hidden Markov model and convolutional neural network-CTC algorithms. The results demonstrated that the more training samples the speech (...) recognition algorithm had, the higher the recognition accuracy of the trained algorithm was, but the training time consumption increased gradually; the more samples a trained speech recognition algorithm had to test, the lower the recognition accuracy and the longer the testing time. The proposed RNN-CTC speech recognition algorithm always had the highest accuracy and the lowest training and testing time among the three algorithms when the number of training and testing samples was the same. (shrink)

Osiurak and Reynaud argue that children are not a good methodological choice to examine cumulative technological culture. However, the paper ignores other current work that suggests that young children do display some aspects of creative problem-solving. We argue that using multiple methodologies and examining how technical-reasoning develops in children will provide crucial support for a cognitive approach to CTC.

Background. Decisions to test, enrol and disclose HIV status are among the ethical challenges that may influence adherence to antiretroviral therapy (ART) and HIV care and treatment in adolescents living with HIV. In the Tanzanian setting, how parental perceptions of ethical issues affect adolescents’ adherence to HIV care and treatment is not well known.Objective. To explore parental perceptions of ethical issues in adolescent HIV care and treatment. Methods. The study employed a descriptive qualitative exploratory design and was conducted at Temeke (...) Regional Referral Hospital in Dar es Salaam Care and Treatment Centre (CTC) in the Outpatient Department (OPD). The study population were parents and non-parent caregivers of HIV-infected adolescents 10 - 19 years of age. A total of 16 persons participated in semi-structured interviews after their consent was obtained. All interviews were audiotaped, transcribed verbatim in Swahili and back-translated into English. An inductive content analysis was used, and standards of qualitative rigour applied. Results. Three qualitative themes emerged: balancing adolescents’ autonomy with parents’ desire to protect their children; parental dilemmas regarding disclosure of adolescents’ HIV status; and parental reasons for delayed disclosure.Conclusion. Participants perceived that parental authority should override adolescents’ autonomy in HIV care and treatment. Disclosure of HIV status to adolescents is a challenge to parents. Delays in disclosure often occur because parents feel guilty and because they have fears of rejection by their adolescent children. (shrink)

Most of this work is concerned with two theories that underlie cognitive science; theories which I call "the representational theory of intentionality" and "the computational theory of cognition" . While the representational theory of intentionality asserts that mental states are about the world in virtue of a representation relation between the world and the state, the computational theory of cognition asserts that humans and others perform cognitive tasks by computing functions on these representations. CTC draws upon a rich analogy between (...) the mind and digital computers, portraying cognizers as receiving input and generating outputs . ;Since researchers within cognitive science--especially within cognitive psychology, computer science, and philosophy of mind--share a common theoretic background in their adherence to the combination of RTI and CTC, what I call "computationalism" most of the work done in philosophy of mind has been aimed at either refuting or further articulating these two theories. This work is strongly within that tradition. ;RTI and CTC combine to create an explanatory framework for explanation in cognitive science. In this work, I seek to delineate the exact structure of this framework, to determine its components and their overall relationships. In my mind, this involves making implicit aspects of computational explanation explicit, providing an overall rationale for the various components and their relationships, and defending that rationale against criticism. ;In particular, the project of this work is to argue that computationalist explanations of cognition within cognitive science need to make appeals to both representation and knowledge; to distinguish the respective roles of knowledge and of representation in an overall picture of computational explanations, and to develop and argue for definitions of representation and knowledge that would allow those concepts to play their respective roles within computational explanations in cognitive science. ;The first half of this work , therefore, is devoted to theories of representation, especially to the need for, and role of representation in computational explanations. The first half of the work culminates in chapter three with a definition of representation and a picture of the structure of computational explanations. The second half of the project then becomes to generate a definition of knowledge that defines knowledge in non-epistemic language amenable to computationalism and that carries the epistemic burdens placed upon knowledge by its use in computational explanations, as well as to offer a limited defence of that definition within the framework of traditional epistemology. (shrink)

Proposed models of closed timelike curves have been shown to enable powerful information-processing protocols. We examine the simulation of models of CTCs both by other models of CTCs and by physical systems without access to CTCs. We prove that the recently proposed transition probability CTCs are physically equivalent to postselection CTCs, in the sense that one model can simulate the other with reasonable overhead. As a consequence, their information-processing capabilities are equivalent. We also describe a method for quantum computers to (...) simulate Deutschian CTCs. In cases for which the overhead is reasonable, it might be possible to perform the simulation in a table-top experiment. This approach has the benefit of resolving some ambiguities associated with the equivalent circuit model of Ralph et al. Furthermore, we provide an explicit form for the state of the CTC system such that it is a maximum-entropy state, as prescribed by Deutsch. (shrink)

Notoriously, the Einstein equations of general relativity have solutions in which closed timelike curves occur. On these curves time loops back onto itself, which has exotic consequences: for example, traveling back into one's own past becomes possible. However, in order to make time travel stories consistent constraints have to be satisfied, which prevents seemingly ordinary and plausible processes from occurring. This, and several other "unphysical" features, have motivated many authors to exclude solutions with CTCs from consideration, e.g. by conjecturing a (...) chronology protection law. In this contribution we shall investigate the nature of one particular class of exotic consequences of CTCs, namely those involving unexpected cases of indeterminism or determinism. Indeterminism arises even against the backdrop of the usual deterministic physical theories when CTCs do not cross spacelike hypersurfaces outside of a limited CTC-region|such hypersurfaces fail to be Cauchy surfaces. We shall compare this CTC-indeterminism with four other types of indeterminism that have been discussed in the philosophy of physics literature: quantum indeterminism, the indeterminism of the hole argument, non-uniqueness of solutions of differential equations and lack of predictability due to insuffcient data. By contrast, a certain kind of determinism appears to arise when an indeterministic theory is applied on a CTC: things cannot be different from what they already were. Again we shall make comparisons, this time with other cases of determination in physics. We shall argue that on further consideration both this indeterminism and determinism on CTCs turn out to possess analogues in other, familiar areas of physics. CTC- indeterminism is close to the epistemological indeterminism we know from statistical physics, while the "fixedness" typical of CTC-determinism is pervasive in physics. CTC- determinism and CTC-indeterminism therefore do not provide incontrovertible grounds for rejecting CTCs as conceptually inadmissible. (shrink)

New Caledonian crow populations have developed complex tools that show suggestive evidence of cumulative change. These tool designs, therefore, appear to be the product of cumulative technological culture. We suggest that tool-using NC crows offer highly useful data for current debates over the necessary and sufficient conditions for the emergence of CTC.

Bennett and Schumacher’s postselected quantum teleportation is a model of closed timelike curves (CTCs) that leads to results physically different from Deutsch’s model. We show that even a single qubit passing through a postselected CTC (P-CTC) is sufficient to do any postselected quantum measurement with certainty, and we discuss an important difference between “Deutschian” CTCs (D-CTCs) and P-CTCs in which the future existence of a P-CTC might affect the present outcome of an experiment. Then, based on a suggestion of Bennett (...) and Smith, we explicitly show how a party assisted by P-CTCs can distinguish a set of linearly independent quantum states, and we prove that it is not possible for such a party to distinguish a set of linearly dependent states. The power of P-CTCs is thus weaker than that of D-CTCs because the Holevo bound still applies to circuits using them, regardless of their ability to conspire in violating the uncertainty principle. We then discuss how different notions of a quantum mixture that are indistinguishable in linear quantum mechanics lead to dramatically differing conclusions in a nonlinear quantum mechanics involving P-CTCs. Finally, we give explicit circuit constructions that can efficiently factor integers, efficiently solve any decision problem in the intersection of NP and coNP, and probabilistically solve any decision problem in NP. These circuits accomplish these tasks with just one qubit traveling back in time, and they exploit the ability of postselected closed timelike curves to create grandfather paradoxes for invalid answers. (shrink)

This essay surveys and synthesizes the academic literature, archival sources and interviews with key policy makers regarding the emergence of community technology centers in the US. Community Technology Centers came to the fore in the late 1990s through an activist nonprofit sector combined with federal government and private sector funding. Federal data indicates that CTCs now represent the most important access points to information communications technology for the poor in the US. This essay reviews the latest arguments for and against (...) continued investment in CTCs and public access in general. In addition to providing access, which is often used beneficially for employment and education related purposes, CTCs appear to contribute to social capital as they become social gathering points. This paper concludes, that both government and nonprofits play a vital role in ensuring public access for the poor and that continued investment in CTCs is warranted. (shrink)

This paper is a survey of the theories of time travel in a perspective close to theories of time. In the last section we discuss the special ontology of the objects that exist on closed timelike curves. We simply assert that CTC need a new ontology and these objects are not simply impossible or unconcevaible.

The computational theory of cognition (CTC) holds that the mind is akin to computer software. This article aims to show that CTC is incorrect because it is not able to distinguish the ability to solve a maze from the ability to solve its mirror image. CTC cannot do so because it only individuates brain states up to isomorphism. It is shown that a finer individuation that would distinguish left-handed from right-handed abilities is not compatible with CTC. The view is explored (...) that CTC correctly individuates in an autonomous domain of the mental, leaving discrimination between left and right to some non-cognitive component of psychology such as physiology. I object by showing that the individuation provided by CTC does not properly describe in any domain. An embodied computational taxonomy, rather than software alone, is required for an adequate science of the mind. (shrink)

The paper is principally concerned with (a) outlining the range of possibilities that exist for organisations which wish to undertake environmental and sustainability reporting and (b) suggesting particular approaches as the more desirable. But the paper also attempts to show that there is an important difference between environmental reporting and reporting for sustainability, and that, so far, efforts to encourage organisations to voluntarily undertake either have not been successful. Environmental reporting is business-centred and there are a number of practicable ways (...) in which it can be undertaken. The most notable of these are the UN CTC approach to financial environmental reporting plus the Compliance-with-Standard Report. Reporting for sustainability is life-centred and, whatever method we adopt it is likely to show that western organisations are not currently sustainable. The concept of sustainability is widely underestimated and misused in business and political circles. This is explored and the real meaning of sustainability operationalised. Environmental reporting and sustainability reporting are shown to be essential and practicable. It is argued, however, that there is little or no prospect of widespread, systematic reporting by corporations without a major regulatory initiative. (shrink)

Osiurak and Reynaud do not explain the evolutionary emergence and development of the elephant in the room, that is, technical cognition. We first argue that there is a tight correlation between the evolution of cumulative technological culture and the evolution of reasoning about abstract forces. Second, intentional teaching plays a greater role in CTC evolution than acknowledged in the target article.

There has been considerable recent interest in the consequences of closed timelike curves (CTCs) for the dynamics of quantum mechanical systems. A vast majority of research into this area makes use of the dynamical equations developed by Deutsch, which were developed from a consistency condition that assumes that mixed quantum states uniquely describe the physical state of a system. We criticize this choice of consistency condition from an epistemic perspective, i.e., a perspective in which the quantum state represents a state (...) of knowledge about a system. We demonstrate that directly applying Deutsch’s condition when mixed states are treated as representing an observer’s knowledge of a system can conceal time travel paradoxes from the observer, rather than resolving them. To shed further light on the appropriate dynamics for quantum systems traversing CTCs, we make use of a toy epistemic theory with a strictly classical ontology due to Spekkens and show that, in contrast to the results of Deutsch, many of the traditional paradoxical effects of time travel are present. (shrink)

In this paper, we propose to incorporate the local attention in WaveNet-CTC to improve the performance of Tibetan speech recognition in multitask learning. With an increase in task number, such as simultaneous Tibetan speech content recognition, dialect identification, and speaker recognition, the accuracy rate of a single WaveNet-CTC decreases on speech recognition. Inspired by the attention mechanism, we introduce the local attention to automatically tune the weights of feature frames in a window and pay different attention on context information for (...) multitask learning. The experimental results show that our method improves the accuracies of speech recognition for all Tibetan dialects in three-task learning, compared with the baseline model. Furthermore, our method significantly improves the accuracy for low-resource dialect by 5.11% against the specific-dialect model. (shrink)

Gödel’s contention that closed timelike curves (CTC’s) are a necessary consequence of the Einstein equations for his metric is challenged. It is seen that the imposition of periodicity in a timelike coordinate is the actual source of CTC’s rather than the physics of general relativity. This conclusion is supported by the creation of Gödel-like CTC’s in flat space by the correct choice of coordinate system and identifications. Thus, the indications are that the notion of a time machine remains exclusively an (...) aspect of science fiction fantasy. The element of the identification of spacetime points is also seen to be the essential factor in the modern creation of CTC’s in the Gott model of moving cosmic strings. (shrink)