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Universe
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Warm Inflation
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Warm Inflation

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Cosmology".

Deadline for manuscript submissions: closed (10 December 2022) | Viewed by 6803

Special Issue Editors

Prof. Dr. Rudnei O. Ramos

E-Mail Website
Guest Editor
Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20550-013, Brazil
Interests: cosmic inflation; field dynamics; finite temperature quantum field theory; cosmological phase transitions; early universe physics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Kamali Vahid

E-Mail Website1 Website2
Guest Editor
1. Department of Physics, Bu-Ali Sina (Avicenna) University, Hamedan, Iran
2. School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
Interests: early time cosmology; inflation; string theory; conformal field theory

Special Issue Information

Dear Colleagues,

Since its original proposal about 25 years ago, the idea of warm inflation has evolved considerably. Among the different proposals that try to implement consistent inflationary dynamics within an explicit quantum field theory realization, the warm inflation paradigm is perhaps one of the most attractive. Warm inflation explores the fact that inflationary dynamics is inherently a multifield problem, since the vacuum energy that drives inflation must eventually be converted to radiation, which generally is comprised of a variety of particle species. The realization of the warm inflation model then explores this fact to realize radiation production concurrently with the inflationary expansion. This is the opposite of the more usual scenario of cold (supercooled) inflation, where a separated period of radiation production after the end of inflation is required. 

Recent developments in warm inflation have demonstrated how it can alleviate and address some of the long-lasting problems plaguing the cold inflation scenario. In particular, warm inflation has been shown to be one of the few inflation model realizations that can be consistent with the so-called swampland program, which indicates warm inflation to be one of the few inflation pictures capable of having a possible UV-complete realization.

The aim of this Special Issue is then to promote further discussions of warm inflation model building, its different implementations, novel theoretical ideas, and the connection to observations through results at the cosmological perturbation level, among other fundamental aspects related to warm inflation. Both original and review papers are invited for this Special Issue.

Prof. Dr. Rudnei O. Ramos
Prof. Dr. Kamali Vahid
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

  • General Aspects of Warm Inflation
  • Dissipative Effects in Inflation
  • Warm Inflation Model Building
  • Cosmological Perturbations in Warm Inflation
  • Connections of Warm Inflation with Quantum Gravity Models

Published Papers (5 papers)

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Research

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16 pages, 527 KiB  
Article
On Warm Natural Inflation and Planck 2018 Constraints
by Mahmoud AlHallak, Khalil Kalid Al-Said, Nidal Chamoun and Moustafa Sayem El-Daher
Universe 2023, 9(2), 80; https://doi.org/10.3390/universe9020080 - 02 Feb 2023
Cited by 9 | Viewed by 977
Abstract
We investigate natural inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the warm inflation paradigm during the slow-roll stage, in both strong and weak dissipation limits; and show that, in the case of a T [...] Read more.
We investigate natural inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the warm inflation paradigm during the slow-roll stage, in both strong and weak dissipation limits; and show that, in the case of a T-linearly dependent dissipative term, it can accommodate the spectral index ns and tensor-to-scalar ratio r observables given by Planck 2018 constraints, albeit with a too-small value of the e-folding number to solve the horizon problem, providing, thus, only a partial solution to natural inflation issues, assuming a T-cubically dependent dissipative term can provide a solution to this e-folding number issue. Full article
(This article belongs to the Special Issue Warm Inflation)
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18 pages, 919 KiB  
Article
Cosmic Evolution of the Logarithmic f(R) Model and the dS Swampland Conjecture
by Jafar Sadeghi, Behnam Pourhassan, Saeed Noori Gashti, Elaheh Naghd Mezerji and Antonio Pasqua
Universe 2022, 8(12), 623; https://doi.org/10.3390/universe8120623 - 25 Nov 2022
Cited by 6 | Viewed by 1048
Abstract
In this paper, we study the inflationary scenario in logarithmic f(R) gravity, where the rate of inflation roll is constant. On the other hand, our gravitational f(R) model is a polynomial plus a logarithmic term. We take [...] Read more.
In this paper, we study the inflationary scenario in logarithmic f(R) gravity, where the rate of inflation roll is constant. On the other hand, our gravitational f(R) model is a polynomial plus a logarithmic term. We take advantage of constant-roll conditions and investigate the cosmic evolution of the logarithmic f(R) gravity. We present a numerical and a graphical study using the model parameters. Additionally, we obtain the corresponding potential by using the constant-roll condition. We obtain the exact value of the potential satisfying the constant-roll conditions. Next, we challenge it with refined swampland conjecture with respect to the Planck data. Finally, we compare our results with the latest observable data. Full article
(This article belongs to the Special Issue Warm Inflation)
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Review

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41 pages, 519 KiB  
Review
The Warm Inflation Story
by Arjun Berera
Universe 2023, 9(6), 272; https://doi.org/10.3390/universe9060272 - 06 Jun 2023
Cited by 10 | Viewed by 1151
Abstract
Warm inflation has normalized two ideas in cosmology, that in the early universe the initial primordial density perturbations generally could be of classical rather than quantum origin and that during inflation, particle production from interactions amongst quantum field, and its backreaction effects, can [...] Read more.
Warm inflation has normalized two ideas in cosmology, that in the early universe the initial primordial density perturbations generally could be of classical rather than quantum origin and that during inflation, particle production from interactions amongst quantum field, and its backreaction effects, can occur concurrent with inflationary expansion. When we first introduced these ideas, both were met with resistance, but today they are widely accepted as possibilities with many models and applications based on them, which is an indication of the widespread influence of warm inflation. Open quantum field theory, which has been utilized in studies of warm inflation, is by now a relevant subject in cosmology, in part due to this early work. In this review I first discuss the basic warm inflation dynamics. I then outline how to compute warm inflation dynamics from first-principles quantum field theory (QFT) and in particular how a dissipative term arises. Warm inflation models can have an inflaton mass bigger than the Hubble scale and the inflaton field excursion can remain sub-Planckian, thus overcoming the most prohibitive problems of inflation model building. I discuss the early period of my work in developing warm inflation that helped me arrive at these important features of its dynamics. Inflationary cosmology today is immersed in hypothetical models, which by now are acting as a diversion from reaching any endgame in this field. I discuss better ways to approach model selection and give necessary requirements for a well constrained and predictive inflation model. A few warm inflation models are pointed out that could be developed to this extent. I discuss how, at this stage, more progress would be made in this subject by taking a broader view on the possible early universe solutions that include not just inflation but the diverse range of options. Full article
(This article belongs to the Special Issue Warm Inflation)
11 pages, 310 KiB  
Review
Looking inside the Swampland from Warm Inflation: Dissipative Effects in De Sitter Expansion
by Arjun Berera and Jaime Calderón-Figueroa
Universe 2023, 9(4), 168; https://doi.org/10.3390/universe9040168 - 30 Mar 2023
Cited by 1 | Viewed by 903
Abstract
This paper reviews the theoretical and phenomenological implications of the swampland conjectures from the perspective of inflationary cosmology, focusing on warm inflation. We demonstrate how the swampland conjectures appear to favor the strong dissipative regime, giving warm inflation a competitive edge over standard [...] Read more.
This paper reviews the theoretical and phenomenological implications of the swampland conjectures from the perspective of inflationary cosmology, focusing on warm inflation. We demonstrate how the swampland conjectures appear to favor the strong dissipative regime, giving warm inflation a competitive edge over standard inflation. Additionally, we ponder the possible deeper implications of dissipation for constructing successful inflation models from string theory. Full article
(This article belongs to the Special Issue Warm Inflation)
34 pages, 1118 KiB  
Review
Recent Developments in Warm Inflation
by Vahid Kamali, Meysam Motaharfar and Rudnei O. Ramos
Universe 2023, 9(3), 124; https://doi.org/10.3390/universe9030124 - 28 Feb 2023
Cited by 16 | Viewed by 1243
Abstract
Warm inflation, its different particle physics model implementations, and the implications of dissipative particle production for its cosmology are reviewed. First, we briefly present the background dynamics of warm inflation and contrast it with the cold inflation picture. An exposition of the space [...] Read more.
Warm inflation, its different particle physics model implementations, and the implications of dissipative particle production for its cosmology are reviewed. First, we briefly present the background dynamics of warm inflation and contrast it with the cold inflation picture. An exposition of the space of parameters for different well-motivated potentials, which are ruled out, or severely constrained in the cold inflation scenario, but not necessarily in warm inflation, is provided. Next, the quantum field theory aspects in realizing explicit microscopic models for warm inflation are given. This includes the derivation of dissipation coefficients relevant in warm inflation for different particle field theory models. The dynamics of cosmological perturbations in warm inflation are then described. The general expression for the curvature scalar power spectrum is shown. We then discuss in detail the relevant regimes of warm inflation, the weak and strong dissipative regimes. We also discuss the results predicted in these regimes of warm inflation and how they are confronted with the observational data. We explain how the dissipative dynamics in warm inflation can address several long-standing issues related to (post-) inflationary cosmology. This includes recent discussions concerning the so-called swampland criteria and how warm inflation can belong to the landscape of string theory. Full article
(This article belongs to the Special Issue Warm Inflation)
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