String Theory

We propose the concepts of philomatics and psychomatics as hybrid combinations of philosophy and psychology with mathematics. We explain four motivations for this combination which are fulfilling the desire of analytical philosophy, proposing science of philosophy, justifying mathematical algorithms by philosophy, and abstraction in both philosophy and mathematics. We enumerate various examples for philomatics and psychomatics, some of which are explained in more depth. The first example is the analysis of relation between the context principle, semantic holism, and the usage (...) theory of meaning with the attention mechanism in mathematics. The other example is on the relations of Plato's theory of forms in philosophy with the holographic principle in string theory, object-oriented programming, and machine learning. Finally, the relation between Wittgenstein's family resemblance and clustering in mathematics is explained. This paper opens the door of research for combining philosophy and psychology with mathematics. (shrink)

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)

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)

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)

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)

The claim that at the so-called Planck scale our current physics breaks down and a new theory of quantum gravity is required is ubiquitous, but the evidence is shakier than the confidence of those assertions warrants. In this paper, I survey five arguments in favour of this claim - based on dimensional analysis, quantum black holes, generalised uncertainty principles, the nonrenormalisability of quantum gravity, and theories beyond the standard model - but find that none of them succeeds. The argument from (...) nonrenormalisability is the most convincing, yet it requires the unwarranted assumption that the same constant of action occurs in every quantum field theory. Therefore, our theories don’t (yet) predict that quantum gravity happens at the Planck scale. (shrink)

The black hole information loss paradox is a catch-all term for a family of puzzles related to black hole evaporation. For almost 50 years, the quest to elucidate the implications of black hole evaporation has not only sustained momentum, but has also become increasingly populated with proposals that seem to generate more questions than they purport to answer. Scholars often neglect to acknowledge ongoing discussions within black hole thermodynamics and statistical mechanics when analyzing the paradox, including the interpretation of Bekenstein-Hawking (...) entropy, which is far from settled. To remedy the dialectical gridlock, I have formulated an overarching, unified framework, which I call ``Black Hole Paradoxes'', that integrates the debates and taxonomizes the relevant `camps' or philosophical positions. -/- I demonstrate that black hole evaporation within Hawking's semi-classical framework insinuates how late-time Hawking radiation is an entangled global system, a contradiction in terms. The relevant forms of information loss are associated with a decrease in maximal Boltzmann entropy and an increase in global von Neumann entropy respectively, which engender what I've branded the ``paradox of phantom entanglement''. Prospective solutions are then tasked with demonstrating how late-time Hawking radiation is either exclusively an entangled subsystem, in which a black hole remnant lingers as an information safehouse, or exclusively an unentangled global system, in which information is evacuated to the exterior. -/- The disagreement between safehouse and evacuation solutions boils down to the statistical interpretation of thermodynamic black hole entropy, i.e., Bekenstein-Hawking entropy. Safehouse solutions attribute Bekenstein-Hawking entropy to a minority of black hole degrees of freedom, those that are associated with the horizon. Evacuation solutions, in contrast, attribute Bekenstein-Hawking entropy to all black hole degrees of freedom. I argue that the interpretation of Bekenstein-Hawking entropy is the litmus test to vet the overpopulated proposal space. So long as any proposal rejecting Hawking's original calculation independently derives black hole evaporation, globally conserves degrees of freedom and entanglement, preserves a version of semi-classical gravity at sub-Planckian scales, and describes black hole thermodynamics in statistical terms, then it counts as a genuine solution to the paradox. (shrink)

The metaphysics of quantum gravity explores metaphysical issues related to research programs in theoretical physics clustered under the term quantum gravity. These research programs aim at the formulation of a theory that reconciles the theory of general relativity with quantum theory. The goal is not necessarily to come up with a unified single theory but, more pragmatically, to describe phenomena with a dual nature, embodying both quantum and relativistic features—such as black holes and the early universe. Approaches to quantum gravity (...) are not yet fully worked-out theories. Nevertheless, they already provide a certain partial understanding of physical reality in different ways. Remarkably, they do so with a striking similarity: they virtually all deny the existence of some features usually regarded as essential to the existence of spacetime (or space and/or time) such as its four-dimensionality, the existence of distances and durations between events, or even the very partial ordering of events. This observation is particularly noteworthy, considering the pervasive influence of spatial and temporal organisation on the human mind across various facets of daily life and theoretical thinking, ranging from most ancient religions to contemporary scientific worldviews. The metaphysics of quantum gravity takes as its starting point the puzzling observation that physics could teach us that space and time are not fundamental. It draws on resources from traditional metaphysics to tackle a set of issues related to the possible non-fundamentality of spacetime, and it investigates its potential implications for venerable traditional issues in metaphysics. The metaphysics of quantum gravity is a relatively small and new research field, and thus as of now, its focus has been on explaining how spacetime could emerge from a more fundamental and non-spatiotemporal ontology. Consequently, this article is equally focused on questions regarding the status of spacetime and the emergence of spacetime. Section 1 situates the field within metaphysics of science more broadly. Sections 2 and 3 investigate, respectively, the status of spacetime in different approaches to quantum gravity and a number of potential issues with its lack of fundamentality. The article then covers the nature of the emerging spatiotemporal ontology (Section 4) and the building relation that relates it to the underlying non-spatiotemporal ontology (Section 5). Section 6 surveys various potential applications of spacetime emergence to a number of debates in metaphysics. (shrink)

The early history of string theory is marked by a shift from strong interaction physics to quantum gravity. The first string models and associated theoretical framework were formulated in the late 1960s and early 1970s in the context of the S-matrix program for the strong interactions. In the mid-1970s, the models were reinterpreted as a potential theory unifying the four fundamental forces. This paper provides a historical analysis of how string theory was developed out of S-matrix physics, aiming to clarify (...) how modern string theory, as a theory detached from experimental data, grew out of an S-matrix program that was strongly dependent upon observable quantities. Surprisingly, the theoretical practice of physicists already turned away from experiment before string theory was recast as a potential unified quantum gravity theory. With the formulation of dual resonance models (the “hadronic string theory”), physicists were able to determine almost all of the models' parameters on the basis of theoretical reasoning. It was this commitment to “non-arbitrariness”, i.e., a lack of free parameters in the theory, that initially drove string theorists away from experimental input, and not the practical inaccessibility of experimental data in the context of quantum gravity physics. This is an important observation when assessing the role of experimental data in string theory. (shrink)

The problem of time involves an overlap between physics, philosophy, psychology and neuroscience. My talk will discuss the role of time in physics but also emphasize that physics may need to expand to address issues usually regarded as being in the other domains. I will first review the mainstream physics view of time, as it arises in Newtonian theory, relativity theory and quantum theory. I will then discuss the various arrows of time, the most fundamental of which is the passage (...) of time associated with consciousness. I will argue that this goes beyond both relativity theory and quantum theory, so that one needs some new physical paradigm to accommodate it. A new paradigm is required anyway to describe quantum gravity and this may elucidate the nature of both time and consciousness. (shrink)

Singularities in general relativity and quantum field theory are often taken not only to motivate the search for a more-fundamental theory (quantum gravity, QG), but also to characterise this new theory and shape expectations of what it is to achieve. Here, we first evaluate how particular types of singularities may suggest an incompleteness of current theories. We then classify four different 'attitudes' towards singularities in the search for QG, and show, through examples in the physics literature, that these lead to (...) different scenarios for the new theory. Two of the attitudes prompt singularity resolution, but only one suggests the need for a theory of QG. Rather than evaluate the different attitudes, we close with some suggestions of factors that influence the choice between them. (shrink)

The transcendental expectation of string theory is that the nature of the fundamental forces, particle spectra and masses, together with coupling constants, is uniquely determined by mathematical and logical consistency, non-empirically, that is by pure reason. However pluralism triumphed with the explosive emergence of the multiverse. String theorists have extended a long-sought dream to a landscape or a happy caparnaum. Proponents of string theory try to qualify their arguments via swampland conjectures while cosmologists retreat to their telescopes. We review the (...) current status of the string theory swampland. (shrink)

There are scientists that have speculated that, since science involves abstraction, generalizations across facts, and the generalization of causes and theories across empirical phenomena, the direction of science is to increasingly unify forces and causes until there is a single general theory unifying all of the forces of nature. The most prominent contemporary example of this attempt to unify all of the forces of nature in a single theory is string theory or superstring theory. String theorists have attempted to emulate (...) Albert Einstein’s call for physicists to attempt to unify all of the forces of physics in a single theory, sometimes called a “theory of everything.” String Theory has been called “untestable,” empirically unverifiable, and “post-empiricist,” and I use another standard by which String Theory might be evaluated, a _Standard of Instrument Design and Technological Productivity. _Moreover, I seek to show that, instead of attempting to unify all of the forces of nature in a single theory or “theory of everything,” it is possible to identify and separate the forces of nature in relation to each other, and order and rank the forces of nature by their capacity to generate branching patterns in the biological sciences or the physical sciences. Ranking forces by their capacity to generate branching patterns (or other shapes or patterns), in the biological sciences or in the physical sciences, is more positivist and testable than attempts to unify all of the forces of nature in a single theory. (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)

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)

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)

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)

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)

We discuss the relation between string theory/supergravity and the observational data in cosmology, as well as at LHC, past and future. We pay particular attention to the possibility of the future detection of primordial gravitational waves and how this might affect our understanding of fundamental physics.

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)

Dualities are a pervasive phenomenon in contemporary physics, in which two physical theories are empirically equivalent, yet prima facie make different ontological claims about the world (potentially very different claims—differing in e.g. the number and radius of dimensions of the universe). Dualities thus present a particular instantiation of the well-known notion of underdetermination of theory by evidence. Many different philosophical proposals have been made for how such putative underdetermination might be resolved—this continues to be a programme of active research.

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, for example, spacetime 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? Int his paper, we undertake a comprehensive and nontechnical 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)

In this paper, some conceptual issues are addressed in order to make sense of what string theory is supposed to tell us about spacetime. The dualities in string theory are used as a starting point for our argumentation. We explore the consequences of a standard view towards these dualities, namely that the dual descriptions represent the same physical situation. Given this view, one has to understand string theory in a manner such that what counts as physical spacetime is based only (...) on the shared physical content—or common core—of the dual descriptions. In general such a spatiotemporal picture does not have to agree with, or be similar to, any of the ones suggested by naïve readings of the dual descriptions. However, in certain regimes or limits, one or the other of the initial dual descriptions may give a good effective description of physical spacetime. (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)

Anthropic reasoning has lately been strongly associated with the string theory landscape and some theories of particle cosmology, such as cosmological inflation. The association is not, contrary to multiple statements by physicists and philosophers alike, necessary. On the contrary, there are clear reasons and instances in which the anthropic reasoning is useful in a diverse range of fields such as planetary sciences, geophysics, future studies, risk analysis, origin of life studies, evolutionary theory, astrobiology and SETI studies, ecology, or even strategic (...) studies and global policy. The association of anthropic reasoning with string theory and particle cosmology has not only become the standard wisdom, but has been often construed in a negative way, in order to demonstrate or insinuate that such reasoning is too abstract or even belongs to 'fringe science', remote from run-of-the-mill research practices in any other more 'mundane' and less theoretical scientific discipline. The purpose of this paper is to (i) analyse some of the counter-examples to the standard wisdom, (ii) suggest that the anthropic reasoning is more flexible, more general, and less fashion-driven than the detractors state. In addition, we consider some historical and/or extrascientific motivation for this persistent prejudice. (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.