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Universe
Special Issues
The Cosmological Constant Puzzle
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The Cosmological Constant Puzzle

A special issue of Universe (ISSN 2218-1997).

Deadline for manuscript submissions: closed (1 October 2019) | Viewed by 5512

Special Issue Editor

Prof. Dr. Steven D. Bass

E-Mail Website
Guest Editor
1. Marian Smoluchowski Institute of Physics, Jagiellonian University, 30-348 Krakow, Poland
2. Kitzbühel Centre for Physics, Kitzbühel, Austria
Interests: theoretical particle physics; QCD; the spin structure of the proton; eta-prime meson physics; the cosmological constant puzzle; positronium physics; quantum field theory

Special Issue Information

Dear Colleagues,

This Special Issue concerns the cosmological constant puzzle. What drives the accelerating expansion of the Universe? Possible contributions to the cosmological constant or vacuum energy density perceived by gravitation are the zero-point energies of quantum field theory and vacuum condensates associated with spontaneous symmetry breaking. The vacuum energy density suggested by the classical Higgs potential in the Standard Model of particle physics is 1056 times too big and comes with the opposite sign compared to the cosmological constant extracted from astrophysics. Results from the Large Hadron Collider at CERN suggest that the particle physics vacuum is close to the border between stable and metastable, with the Standard Model working as a consistent theory up to the Planck scale. Might the Higgs mass hierarchy puzzle and the size of the cosmological constant be linked, involving new physics close to the Planck scale? Is the vacuum energy perceived by gravitation time-dependent or time-independent? Might the cosmological constant be hinting at the need for modifications to our theory of gravity, e.g., involving a new 5th force or new extra dimensions? Is quantum gravity required to understand the cosmological constant? This Special Issue will explore these fundamental issues at the interface of particle physics and gravity science.  We welcome the submission of research or review articles addressing these topics, broadly interpreted. To promote communication between the different sub-fields, we encourage papers that are accessible to both theorists and experimentalists working on this fundamental science.

Prof. Dr. Steven D. Bass
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. 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

  • cosmological constant
  • vacuum energy
  • dark energy
  • zero-point energies
  • spontaneous symmetry breaking
  • vacuum condensates
  • vacuum stability
  • 5th forces
  • modified gravity
  • inflation

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Published Papers (2 papers)

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Research

15 pages, 289 KiB  
Article
Cosmological Constant in SUGRA Models with Degenerate Vacua
by Colin Froggatt, Holger Nielsen, Roman Nevzorov and Anthony Thomas
Universe 2019, 5(10), 214; https://doi.org/10.3390/universe5100214 - 22 Oct 2019
Viewed by 2509
Abstract
The extrapolation of couplings up to the Planck scale within the standard model (SM) indicates that the Higgs effective potential can have two almost degenerate vacua, which were predicted by the multiple point principle (MPP). The application of the MPP to [...] Read more.
The extrapolation of couplings up to the Planck scale within the standard model (SM) indicates that the Higgs effective potential can have two almost degenerate vacua, which were predicted by the multiple point principle (MPP). The application of the MPP to ( N = 1 ) supergravity (SUGRA) implies that the SUGRA scalar potential of the hidden sector possesses at least two exactly degenerate minima. The first minimum is associated with the physical phase in which we live. In the second supersymmetric (SUSY) Minkowski vacuum, the local SUSY may be broken dynamically, inducing a tiny vacuum energy density. In this paper, we consider the no-scale-inspired SUGRA model in which the MPP conditions are fulfilled without any extra fine-tuning at the tree-level. Assuming that at high energies, the couplings in both phases are identical, one can estimate the dark energy density in these vacua. Using the two-loop renormalization group (RG) equations, we find that the measured value of the cosmological constant can be reproduced if the SUSY breaking scale M S in the physical phase is of the order of 100 TeV. The scenario with the Planck scale SUSY breaking is also discussed. Full article
(This article belongs to the Special Issue The Cosmological Constant Puzzle)
77 pages, 654 KiB  
Article
Cosmic Microwave Background from Effective Field Theory
by Sayantan Choudhury
Universe 2019, 5(6), 155; https://doi.org/10.3390/universe5060155 - 19 Jun 2019
Cited by 25 | Viewed by 2560
Abstract
In this work, we study the key role of generic Effective Field Theory (EFT) framework to quantify the correlation functions in a quasi de Sitter background for an arbitrary initial choice of the quantum vacuum state. We perform the computation in unitary gauge, [...] Read more.
In this work, we study the key role of generic Effective Field Theory (EFT) framework to quantify the correlation functions in a quasi de Sitter background for an arbitrary initial choice of the quantum vacuum state. We perform the computation in unitary gauge, in which we apply the Stückelberg trick in lowest dimensional EFT operators which are broken under time diffeomorphism. In particular, using this non-linear realization of broken time diffeomorphism and truncating the action by considering the contribution from two derivative terms in the metric, we compute the two-point and three-point correlations from scalar perturbations and two-point correlation from tensor perturbations to quantify the quantum fluctuations observed in the Cosmic Microwave Background (CMB) map. We also use equilateral limit and squeezed limit configurations for the scalar three-point correlations in Fourier space. To give future predictions from EFT setup and to check the consistency of our derived results for correlations, we use the results obtained from all classes of the canonical single-field and general single-field P ( X , ϕ ) model. This analysis helps us to fix the coefficients of the relevant operators in EFT in terms of the slow-roll parameters and effective sound speed. Finally, using CMB observations from Planck we constrain all these coefficients of EFT operators for the single-field slow-roll inflationary paradigm. Full article
(This article belongs to the Special Issue The Cosmological Constant Puzzle)
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