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Entropy
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Exploring Spacetime Emergence from the Quantum Level
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Exploring Spacetime Emergence from the Quantum Level

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Time".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 8192

Special Issue Editor

Dr. Ruth E. Kastner

E-Mail Website
Guest Editor
Philosophy Department, Skinner Building, University of Maryland, College Park, MD 20742, USA
Interests: interpretations of quantum theory; temporal symmetry breaking; spacetime emergence; modifications of general relativity

Special Issue Information

Dear Colleagues,

It has long been recognized that quantum theory seems to be in tension with certain aspects of relativity theory, although Shimony observed that there is a form of “peaceful coexistence” in that quantum theory disallows faster-than-light controllable signaling (i.e., transfers of energy). This Special Issue explores the possibility that quantum theory and relativity describe distinctly different aspects or domains of physical reality, yet which are ultimately reconcilable. In particular, the spacetime construct might be viewed as a structure that is emergent from the quantum level. Since emergence is a process that implies a directional component, and thus some form of irreversibility, consideration of spacetime emergence could break new ground in understanding time-asymmetrical processes such as those described by thermodynamics.

This possibility raises intriguing questions, such as:

  • What is the relation between the quantum level and the spacetime level?
  • Might the arrow of time emerge from the quantum level along with the spacetime construct? If so, does “measurement” play a role in this emergence?
  • What sorts of correspondence (or other) principles would reconcile local spacetime processes with the apparently nonlocal quantum level?
  • Might consideration of spacetime emergence lead to a novel approach to a theory of quantum gravity?

Dr. Ruth E. Kastner
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Time asymmetry
  • Irreversible processes
  • Quantum theory
  • Quantum measurement
  • Spacetime emergence
  • General relativity
  • Quantum gravity
  • Nonlocality

Published Papers (3 papers)

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Research

15 pages, 1756 KiB  
Article
The Potential of a Thick Present through Undefined Causality and Non-Locality
by Alessandro Capurso
Entropy 2022, 24(3), 410; https://0-doi-org.brum.beds.ac.uk/10.3390/e24030410 - 15 Mar 2022
Cited by 1 | Viewed by 3477
Abstract
This paper elaborates on the interpretation of time and entanglement, offering insights into the possible ontological nature of information in the emergence of spacetime, towards a quantum description of gravity. We first investigate different perspectives on time and identify in the idea of [...] Read more.
This paper elaborates on the interpretation of time and entanglement, offering insights into the possible ontological nature of information in the emergence of spacetime, towards a quantum description of gravity. We first investigate different perspectives on time and identify in the idea of a “thick present” the only element of reality needed to describe evolution, differences, and relations. The thick present is connected to a spacetime information “sampling rate”, and it is intended as a time symmetric potential bounded between a causal past of irreversible events and a still open future. From this potential, spacetime emerges in each instant as a space-like foliation (in a description based on imaginary paths). In the second part, we analyze undefined causal orders to understand how their potential could persist along the thick present instants. Thanks to a C-NOT logic and the concept of an imaginary time, we derive a description of entanglement as the potential of a logically consistent open choice among imaginary paths. We then conceptually map the imaginary paths identified in the entanglement of the undefined orders to Closed Time-like Curves (CTC) in the thick present. Considering a universe described through information, CTC are interpreted as “memory loops”, elementary structures encoding the information potential related to the entanglement in both time and space, manifested as undefined causality and non-locality in the emerging foliation. We conclude by suggesting a possible extension of the introduced concepts in a holographic perspective. Full article
(This article belongs to the Special Issue Exploring Spacetime Emergence from the Quantum Level)
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15 pages, 332 KiB  
Article
Categorical Smoothness of 4-Manifolds from Quantum Symmetries and the Information Loss Paradox
by Jerzy Król and Torsten Asselmeyer-Maluga
Entropy 2022, 24(3), 391; https://0-doi-org.brum.beds.ac.uk/10.3390/e24030391 - 11 Mar 2022
Viewed by 1725
Abstract
In this paper, we focus on some aspects of the relation of spacetime and quantum mechanics and the study counterparts (in Set) of the categorical local symmetries of smooth 4-manifolds. In the set-theoretic limit, there emerge some exotic smoothness structures on R4 [...] Read more.
In this paper, we focus on some aspects of the relation of spacetime and quantum mechanics and the study counterparts (in Set) of the categorical local symmetries of smooth 4-manifolds. In the set-theoretic limit, there emerge some exotic smoothness structures on R4 (hence the Riemannian nonvanishing curvature), which fit well with the quantum mechanical lattice of projections on infinite-dimensional Hilbert spaces. The method we follow is formalization localized on the open covers of the spacetime manifold. We discuss our findings in the context of the information paradox assigned to evaporating black holes. A black hole can evaporate entirely, but the smoothness structure of spacetime will be altered and, in this way, the missing information about the initial states of matter forming the black hole will be encoded. Thus, the possible global geometric remnant of black holes in spacetime is recognized as exotic 4-smoothness. The full-fledged verification of this proposal will presumably be possible within the scope of future quantum gravity theory research. Full article
(This article belongs to the Special Issue Exploring Spacetime Emergence from the Quantum Level)
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15 pages, 474 KiB  
Article
Possibility and Time in Quantum Mechanics
by Olimpia Lombardi, Sebastian Fortin and Matías Pasqualini
Entropy 2022, 24(2), 249; https://0-doi-org.brum.beds.ac.uk/10.3390/e24020249 - 08 Feb 2022
Cited by 3 | Viewed by 1577
Abstract
In the discourse of quantum mechanics it is usual to say that non-commuting observables cannot have definite values at the same time, or that they cannot be simultaneously measured. But, what does the term ‘cannot’ mean in this context? Does it stand for [...] Read more.
In the discourse of quantum mechanics it is usual to say that non-commuting observables cannot have definite values at the same time, or that they cannot be simultaneously measured. But, what does the term ‘cannot’ mean in this context? Does it stand for impossible? Should Heisenberg’s principle be read in terms of uncertainty or of indeterminacy? On the other hand, whereas the debates about the nature of time in classical and relativistic mechanics have been many and varied, the question about the nature of time in quantum mechanics has not received the same attention, especially when compared to the large amount of literature on interpretive issues. The purpose of this paper is to show that, under a realist interpretation of quantum mechanics, these two matters, possibility and time, are strongly related. The final aim is to argue that, when possibility and actuality are conceived as irreducible modes of being, they are correlated to two different notions of time that can be distinguished in the quantum realm: parameter-time and event-time. Full article
(This article belongs to the Special Issue Exploring Spacetime Emergence from the Quantum Level)
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