25 research outputs found
String Theory - From Physics to Metaphysics
Currently, string theory represents the only advanced approach to a
unification of all interactions, including gravity. In spite of the more than
thirty years of its existence it did not make any empirically testable
predictions. And it is completely unknown which physically interpretable
principles could form the basis of string theory. At the moment, "string
theory" is no theory at all, but rather a labyrinthic structure of mathematical
procedures and intuitions which get their justification from the fact that
they, at least formally, reproduce general relativity and the standard model of
elementary particle physics as low energy approximations. However, there are
now strong indications that string theory does not only reproduce the dynamics
and symmetries of our standard model, but a plethora of different scenarios
with different low energy nomologies and symmetries. String theory seems to
describe not only our world, but an immense landscape of possible worlds. So
far, all attempts to find a selection principle which could be motivated
intratheoretically remained without success. So, recently the idea that the low
energy nomology of our world, and therefore also the observable phenomenology,
could be the result of an anthropic selection from a vast arena of
nomologically different scenarios entered string theory. Although multiverse
scenarios and anthropic selection are not only motivated by string theory, but
lead also to a possible explanation for the fine tuning of the universe, they
are concepts which transcend the framework defined by the epistemological and
methodological rules which conventionally form the basis of physics as an
empirical science.Comment: 30 pages, submitted to "Physics and Philosophy" (Online-Journal
String Theory - Nomological Unification and the Epicycles of the Quantum Field Theory Paradigm
String Theory is the result of the conjunction of three conceptually
independent elements: (i) the metaphysical idea of a nomological unity of the
forces, (ii) the model-theoretical paradigm of Quantum Field Theory, and (iii)
the conflict resulting from classical gravity in a quantum world. String Theory
is sometimes assumed to solve this conflict: by means of an application of the
model-theoretical apparatus of (perturbative) Quantum Field Theory. But, String
Theory does not really solve the conflict. Rather it exemplifies the inadequacy
of this model-theoretical apparatus in the context of Quantum Gravity: After
several decades of development it still exists only in an essentially
perturbative formulation (with minor non-perturbative extensions and vague
ideas with regard to a possible non-perturbative formulation). And, due to its
quantum field theoretical heritage, it is conceptually incompatible with
central implications of General Relativity, especially those resulting from the
general relativistic relation between gravity and spacetime. All known
formulations of String Theory are background-dependent. On the other hand, it
was not even possible to reproduce the Standard Model. Instead, String Theory
led to a multitude of internal problems - and to the plethora of low-energy
scenarios with different nomologies and symmetries, known as the String
Landscape. All attempts to find a dynamically motivated selection principle
remained without success, leaving String Theory without any predictive power.
The nomological unification of the fundamental forces is only achieved in a
purely formal way within the model-theoretical paradigm of Quantum Field Theory
- by means of physically unmotivated epicycles like higher dimensionality,
Calabi-Yau spaces, branes, etc.Comment: 23 page
Quantum Gravity: Has Spacetime Quantum Properties?
The incompatibility between GR and QM is generally seen as a sufficient
motivation for the development of a theory of Quantum Gravity. If - so a
typical argumentation - QM gives a universally valid basis for the description
of all natural systems, then the gravitational field should have quantum
properties. Together with the arguments against semi-classical theories of
gravity, this leads to a strategy which takes a quantization of GR as the
natural avenue to Quantum Gravity. And a quantization of the gravitational
field would in some sense correspond to a quantization of geometry. Spacetime
would have quantum properties. But, this strategy will only be successful, if
gravity is a fundamental interaction. - What, if gravity is instead an
intrinsically classical phenomenon? Then, if QM is nevertheless fundamentally
valid, gravity can not be a fundamental interaction. An intrinsically classical
gravity in a quantum world would have to be an emergent, induced or residual,
macroscopic effect, caused by other interactions. The gravitational field (as
well as spacetime) would not have any quantum properties. A quantization of GR
would lead to artifacts without any relation to nature. The serious problems of
all approaches to Quantum Gravity that start from a direct quantization of GR
or try to capture the quantum properties of gravity in form of a 'graviton'
dynamics - together with the, meanwhile, rich spectrum of approaches to an
emergent gravity and/or spacetime - make this latter option more and more
interesting for the development of a theory of Quantum Gravity. The most
advanced emergent gravity (and spacetime) scenarios are of an
information-theoretical, quantum-computational type.Comment: 31 page
Las Bases Materiales de Nuestras Capacidades Epistemicas. Ensayo de Una Revision Sintetica de la Epistemologia
Tras el fracaso del fundamentalismo epistemológico (que es el fracaso de los ideales de la fundamentación, de la certeza y de la justificación rigurosa de nuestro conocimiento) existen motivos suficientes para una transición de la epistemología pura y analítica a un procedimiento sintético, que integra componentes empírico-científicos en el contexto de la epistemología descriptiva. De una relevancia específica para la cuestión de la realización de nuestros conocimientos son por ejemplo los resultados recientes de las neurociencias. El artículo presenta los primeros resultados de una "neuro-epistemología" constituida con la integración de elementos procedentes de las neurociencias en los problemas de la epistemología.After the breakdown of epistemological fundamentalism (i.e. the ideals of fundamentation, of certainty and of a definitive justification for our knowledge) we have sufficient causes to change the traditional pure and analytic epistemology for a synthetic procedure, which integrates components from the empirical sciences into the context of descriptive epistemology. Of specific relevance for the question of the neurosciences. The article presents the first results of a "neuro-epistemology", hich forms by the integration of elements from the neurosciences into the consideration of the problems of epistemology
Quantum Gravity: Motivations and Alternatives
The mutual conceptual incompatibility between GR and QM/QFT is generally seen
as the most essential motivation for the development of a theory of Quantum
Gravity (QG). It leads to the insight that, if gravity is a fundamental
interaction and QM is universally valid, the gravitational field will have to
be quantized, not at least because of the inconsistency of semi-classical
theories of gravity. If this means to quantize GR, its identification of the
gravitational field with the spacetime metric has to be taken into account. And
the resulting quantum theory has to be background-independent. This can not be
achieved by means of quantum field theoretical procedures. More sophisticated
strategies have to be applied. One of the basic requirements for such a
quantization strategy is that the resulting quantum theory has GR as a
classical limit. - However, should gravity not be a fundamental, but an
residual, emergent interaction, it could very well be an intrinsically
classical phenomenon. Should QM be nonetheless universally valid, we had to
assume a quantum substrate from which gravity would result as an emergent
classical phenomenon. And there would be no conflict with the arguments against
semi-classical theories, because there would be no gravity at all on the
substrate level. The gravitational field would not have any quantum properties,
and a quantization of GR would not lead to any fundamental theory. The
objective of a theory of 'QG' would instead be the identification of the
quantum substrate from which gravity results. - The paper tries to give an
overview over the main options for theory construction in the field of QG.
Because of the still unclear status of gravity and spacetime, it pleads for the
necessity of a plurality of conceptually different approaches to QG.Comment: 32 page
Quantum gravity: motivations and alternatives
The mutual conceptual incompatibility between General Relativity and Quantum Mechanics / Quantum Field Theory is generally seen as the most essential motivation for the development of a theory of Quantum Gravity. It leads to the insight that, if gravity is a fundamental interaction and Quantum Mechanics is universally valid, the gravitational field will have to be quantized, not at least because of the inconsistency of semi-classical theories of gravity. The objective of a theory of Quantum Gravity would then be to identify the quantum properties and the quantum dynamics of the gravitational field. If this means to quantize General Relativity, the general-relativistic identification of the gravitational field with the spacetime metric has to be taken into account. The quantization has to be conceptually adequate, which means in particular that the resulting quantum theory has to be background-independent. This can not be achieved by means of quantum field theoretical procedures. More sophisticated strategies, like those of Loop Quantum Gravity, have to be applied. One of the basic requirements fo
Von der Physik zur Metaphysik. Physikalische Vereinheitlichung und Stringansatz
Obwohl der Stringansatz als Versuch einer nomologisch vereinheitlichten Erfassung aller Wechselwirkungen, inklusive der Gravitation, schon über drei Jahrzehnte existiert, sind die ihm zugrundeliegenden physikalischen Prinzipien noch völlig unklar; und es gibt nicht die geringste empirisch überprüfbare, quantitative Vorhersage. Ohne empirische Daten, die mit den etablierten Theorien - quantenfeldtheoretischem Standardmodell und Allgemeiner Relativitätstheorie - unvereinbar wären, liefert nur die konzeptionelle Inkompatibilität beider, gemeinsam mit der Vereinheitlichungsidee, eine Motivation für den Stringansatz. Mit diesem droht jedoch die Physik, unter konsequenter Weiterführung ihrer bisher erfolgreichen Strategien, den methodologischen Rahmen der empirischen Wissenschaften zu überschreiten
The Internal and External Problems of String Theory - A Philosophical View
String theory is at the moment the only advanced approach to a unification of all interactions, including gravity. But, in spite of the more than thirty years of its existence, it does not make any empirically testable predictions, and it is completely unknown which physically interpretable principles could form the basis of string theory. At the moment, "string theory" is no theory at all, but rather a labyrinthic structure of mathematical procedures and intuitions. The only motivations for string theory consist in the mutual incompatibility of the standard model of quantum field theory and of general relativity as well as in the metaphysics of the unification program of physics, aimed at a final unified theory of all interactions, including gravity. The article gives a perspective on the problems leading to and resulting from this situation