String Theory

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)

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)

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)

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)

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)

Au fost propuse mai multe teorii unificatoare. Marea unificare presupune existența unei forțe electronucleare. Ultimul pas în unificare ar necesita o teorie care să includă atât mecanica cuantică cât și gravitația prin relativitatea generală (”teoria finală”). După 1990, unii fizicieni consideră că teoria M 11-dimensională, identificată adesea cu una dintre cele cinci teorii ale supercorzilor perturbative, sau uneori cu supergravitația maximal-supersimetrică 11-dimensională, este teoria finală. DOI: 10.13140/RG.2.2.23549.92642.

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)

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)

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)

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)

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)

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 assumption, 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)

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)

"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)

The host of SUSY(supersymmetry) based string theories is considered. Superstrings are comprehended as possible candidates on Quantum Gravity basic objects. It is argued that superstring theories constitute mainly mathematical progress and can reconcile general relativity with quantum field theory at best. Yet they cannot provide the genuine synthesis. Superstring unification of all the four forces at hand is a formal one . It is contended that genesis and proliferation of superstrings can better be described not by philosophy of science models (...) but in terms of modern sociology of science. The formal character of gravity and quantum fields fusion and the lack of experimental verification make the transition to superstring theories ad hoc in Lakatosian standards. Possible way of explanation is proposed based on social interests conception of Andrew Pickering. -/- Key words: superstrings, unification, Kaluza-Klein, sociology of science . (shrink)

The notion of consciousness has been studied in many ways out of which, there could be a scientific approach of studying it using string theory which enjoys the mathematical coherence. The paper aims to study consciousness using string theory in which the role of graviton will be discussed. The notion of parallel universes given by string theory would be tackled to understand consciousness and make an attempt to clarify the notion of other world or universe and parallel universes, the problems (...) of time travel, soul and death in the universe or universes of strings which gets twisted and compactified. (shrink)