Any consistent coupling between classical gravity and quantum matter is fundamentally irreversible

• URL: http://arxiv.org/abs/2301.10261v2
• Date: Thu, 12 Oct 2023 10:08:02 GMT
• Title: Any consistent coupling between classical gravity and quantum matter is fundamentally irreversible
• Authors: Thomas D. Galley, Flaminia Giacomini, John H. Selby
• Abstract summary: We argue that when gravity is classical at least one of the following assumptions needs to be violated. We argue that theories of classical gravity and quantum matter must be fundamentally irreversible.
• Score: 0.0
• License: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Abstract: When gravity is sourced by a quantum system, there is tension between its role as the mediator of a fundamental interaction, which is expected to acquire nonclassical features, and its role in determining the properties of spacetime, which is inherently classical. Fundamentally, this tension should result in breaking one of the fundamental principles of quantum theory or general relativity, but it is usually hard to assess which one without resorting to a specific model. Here, we answer this question in a theory-independent way using General Probabilistic Theories (GPTs). We consider the interactions of the gravitational field with a single matter system, and derive a no-go theorem showing that when gravity is classical at least one of the following assumptions needs to be violated: (i) Matter degrees of freedom are described by fully non-classical degrees of freedom; (ii) Interactions between matter degrees of freedom and the gravitational field are reversible; (iii) Matter degrees of freedom back-react on the gravitational field. We argue that this implies that theories of classical gravity and quantum matter must be fundamentally irreversible, as is the case in the recent model of Oppenheim et al. Conversely if we require that the interaction between quantum matter and the gravitational field is reversible, then the gravitational field must be non-classical.

Related papers

• Relaxation of first-class constraints and the quantization of gauge theories: from "matter without matter" to the reappearance of time in quantum gravity [75.38606213726906]
  First-class phase-space constraints may be relaxed if we interpret them as fixing the values of new degrees of freedom. This idea goes back to Fock and Stueckelberg, leading to restrictions of the gauge symmetry of a theory. In particular, in the case of canonical quantum gravity, the Fock--Stueckelberg approach is relevant to the so-called problem of time.
  arXiv  Detail & Related papers  (2024-02-19T19:00:02Z)
• Distinguishable consequence of classical gravity on quantum matter [0.0]
  A consistent co-existence of classical gravity and quantum matter requires that gravity exhibit irreducible classical fluctuations. We use a consistent theory of quantum-classical dynamics, together with general relativity, to show that experimentally relevant observables can conclusively test the hypothesis that gravity is classical.
  arXiv  Detail & Related papers  (2023-09-16T22:32:04Z)
• Does the Universe have its own mass? [62.997667081978825]
  The mass of the universe is a distribution of non-zero values of gravitational constraints. A formulation of the Euclidean quantum theory of gravity is also proposed to determine the initial state. Being unrelated to ordinary matter, the distribution of its own mass affects the geometry of space.
  arXiv  Detail & Related papers  (2022-12-23T22:01:32Z)
• Quantum Instability [30.674987397533997]
  We show how a time-independent, finite-dimensional quantum system can give rise to a linear instability corresponding to that in the classical system. An unstable quantum system has a richer spectrum and a much longer recurrence time than a stable quantum system.
  arXiv  Detail & Related papers  (2022-08-05T19:53:46Z)
• Correspondence Between the Energy Equipartition Theorem in Classical Mechanics and its Phase-Space Formulation in Quantum Mechanics [62.997667081978825]
  In quantum mechanics, the energy per degree of freedom is not equally distributed. We show that in the high-temperature regime, the classical result is recovered.
  arXiv  Detail & Related papers  (2022-05-24T20:51:03Z)
• Is gravitational entanglement evidence for the quantization of spacetime? [0.0]
  Experiments witnessing the entanglement between two particles interacting only via the gravitational field have been proposed as a test whether gravity must be quantized. We present a parametrized model for the gravitational interaction of quantum matter on a classical spacetime, inspired by the de Broglie-Bohm formulation of quantum mechanics.
  arXiv  Detail & Related papers  (2022-05-02T14:37:24Z)
• Quantum dynamics corresponding to chaotic BKL scenario [62.997667081978825]
  Quantization smears the gravitational singularity avoiding its localization in the configuration space. Results suggest that the generic singularity of general relativity can be avoided at quantum level.
  arXiv  Detail & Related papers  (2022-04-24T13:32:45Z)
• Quantum interference in external gravitational fields beyond General Relativity [0.0]
  We study the phenomenon of quantum interference in the presence of external gravitational fields. In the non-relativistic regime, it is possible to come across a gravitational counterpart of the Bohm-Aharonov effect. On the other hand, beyond the Newtonian approximation, the relativistic nature of gravity plays a crucial role.
  arXiv  Detail & Related papers  (2021-04-22T16:11:42Z)
• A no-go theorem on the nature of the gravitational field beyond quantum theory [0.0]
  Table-top experiments involving massive quantum systems have been proposed to test the interface of quantum theory and gravity. In particular, the crucial point of the debate is whether it is possible to conclude anything on the quantum nature of the gravitational field. We introduce the framework of Generalised Probabilistic Theories (GPTs) to study the nature of the gravitational field.
  arXiv  Detail & Related papers  (2020-12-02T19:00:03Z)
• Emergence of classical behavior in the early universe [68.8204255655161]
  Three notions are often assumed to be essentially equivalent, representing different facets of the same phenomenon. We analyze them in general Friedmann-Lemaitre- Robertson-Walker space-times through the lens of geometric structures on the classical phase space. The analysis shows that: (i) inflation does not play an essential role; classical behavior can emerge much more generally; (ii) the three notions are conceptually distinct; classicality can emerge in one sense but not in another.
  arXiv  Detail & Related papers  (2020-04-22T16:38:25Z)
• A postquantum theory of classical gravity? [0.0]
  We present an alternative approach by constructing a consistent theory of classical gravity coupled to quantum field theory. The dynamics doesn't suffer from the pathologies of the semiclassical theory based on expectation values. One can view the classical-quantum theory as fundamental or as an effective theory useful for computing the backreaction of quantum fields on geometry.
  arXiv  Detail & Related papers  (2018-11-07T19:10:10Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.