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Universe
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Quantum Aspects of the Universe
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Quantum Aspects of the Universe

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Foundations of Quantum Mechanics and Quantum Gravity".

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 3349

Special Issue Editors

Dr. Sayantan Choudhury

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Guest Editor
Max Planck Institute for Gravitational Physics, 14476 Potsdam, Germany
Interests: theoretical cosmology; quantum information theory; open quantum system; quantum entanglement; quantum field theory; non equilibrium aspects of statistical field theory; classical and quantum aspects of gravity; quantum chaos; quantum quench; string theory
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Sudhakar Panda

E-Mail Website
Guest Editor
National Institute of Science Education and Research, Jatni, PO: Bhimpur-Padanpur, Pin: 752050, Odisha, India
Interests: string theory; cosmology; finite temperature field theory; conformal field theory; gravity and supergravity; neutrino physics
Prof. Dr. Subhashish Banerjee

E-Mail Website
Guest Editor
Indian Institute of Technology Jodhpur, Old Residency Road, Ratnada, Jodhpur 342011, India
Interests: open quantum systems; quantum information; quantum optics

Special Issue Information

Dear Colleagues,

Recently, the study of the quantum aspects of the universe has been experiencing a strong comeback. Several tools and techniques to study various quantum aspects of the universe are proving extremely significant and enlightening. The study of such issues explores various unknown cosmological, quantum gravity and quantum field theory implications and applications in our universe. This special edition of Universe is completely devoted to recent developments in quantum mechanical and field theoretic aspects of our universe, with a special focus on the quantum field theory aspects of cosmology. Any related articles are invited to be submitted for this Special Issue.

The topics of interest for this Special Issue include, but are not limited to:

  • Various quantum field theory aspects of cosmology
  • Non-perturbative approach to quantum gravity and string theory
  • Open quantum systems
  • Quantum entanglement, information theory and its connection with quantum gravity
  • Non-equilibrium aspects of quantum field theory
  • Quantum chaos and quantum quench
  • Cosmology condensed matter physics correspondence
  • Various aspects of AdS/CFT

 

Dr. Sayantan Choudhury
Prof. Dr. Sudhakar Panda
Prof. Dr. Subhashish Banerjee
Guest Editors

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. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. 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

  • Quantum field theory
  • Quantum gravity
  • Quantum cosmology
  • Quantum entanglement and information theory
  • Open quantum systems
  • Non-equilibrium aspects
  • Quantum chaos
  • Quantum quench
  • Cosmology condensed matter physics correspondence
  • AdS/CFT

Published Papers (2 papers)

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Research

39 pages, 2287 KiB  
Article
No Intrinsic Decoherence of Inflationary Cosmological Perturbations
by Jen-Tsung Hsiang and Bei-Lok Hu
Universe 2022, 8(1), 27; https://doi.org/10.3390/universe8010027 - 03 Jan 2022
Cited by 14 | Viewed by 1288
Abstract
After a brief summary of the four main veins in the treatment of decoherence and quantum to classical transition in cosmology since the 1980s, we focus on one of these veins in the study of quantum decoherence of cosmological perturbations in inflationary universe, [...] Read more.
After a brief summary of the four main veins in the treatment of decoherence and quantum to classical transition in cosmology since the 1980s, we focus on one of these veins in the study of quantum decoherence of cosmological perturbations in inflationary universe, the case when it does not rely on any environment. This is what ‘intrinsic’ in the title refers to—a closed quantum system, consisting of a quantum field which drives inflation. The question is whether its quantum perturbations, which interact with the density contrast giving rise to structures in the universe, decohere with an inflationary expansion of the universe. A dominant view which had propagated for a quarter of a century asserts yes, based on the belief that the large squeezing of a quantum state after a duration of inflation renders the system effectively classical. This paper debunks this view by identifying the technical fault-lines in its derivations and revealing the pitfalls in its arguments which drew earlier authors to this wrong conclusion. We use a few simple quantum mechanical models to expound where the fallacy originated: The highly squeezed ellipse quadrature in phase space cannot be simplified to a line, and the Wigner function cannot be replaced by a delta function. These measures amount to taking only the leading order in the relevant parameters in seeking the semiclassical limit and ignoring the subdominant contributions where quantum features reside. Doing so violates the bounds of the Wigner function, and its wave functions possess negative eigenvalues. Moreover, the Robertson-Schrödinger uncertainty relation for a pure state is violated. For inflationary cosmological perturbations, in addition to these features, entanglement exists between the created pairs. This uniquely quantum feature cannot be easily argued away. Indeed, it could be our best hope to retroduce the quantum nature of cosmological perturbations and the trace of an inflation field. All this points to the invariant fact that a closed quantum system, even when highly squeezed, evolves unitarily without loss of coherence; quantum cosmological perturbations do not decohere by themselves. Full article
(This article belongs to the Special Issue Quantum Aspects of the Universe)
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11 pages, 272 KiB  
Article
Anti-BRST in the Causal Approach
by Dan-Radu Grigore
Universe 2021, 7(2), 26; https://doi.org/10.3390/universe7020026 - 26 Jan 2021
Viewed by 1542
Abstract
It is known that the elimination of anomalies in all orders of perturbation theory is an open problem. The constraints given by usual invariance properties and the Wess–Zumino identities are not enough to eliminate the anomalies in the general case of a Yang–Mills [...] Read more.
It is known that the elimination of anomalies in all orders of perturbation theory is an open problem. The constraints given by usual invariance properties and the Wess–Zumino identities are not enough to eliminate the anomalies in the general case of a Yang–Mills theory. So, any new symmetry of the model could restrict further the anomalies and be a solution of the problem. We consider the anti-BRST transform of Ojima in the causal approach and investigate if such new restrictions are obtained. Unfortunately, the result is negative: if we have BRST invariance up to the second order of perturbation theory, we also have anti-BRST invariance up to the same order. Probably, this result is true in all orders of perturbation theory. So, anti-BRST transform gives nothing new, and we have to find other ideas to restrict and eventually eliminate the anomalies for a general Yang–Mills theory. Full article
(This article belongs to the Special Issue Quantum Aspects of the Universe)
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