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Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches

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

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 37949

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Special Issue Editors

Dr. Sunny Vagnozzi

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Guest Editor

Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, TN, Italy
Interests: cosmology; cosmic microwave background; large-scale structure; dark matter; dark energy; neutrino cosmology; modified gravity; gravitational waves; astroparticle physics; black hole physics

Dr. Eleonora Di Valentino

E-Mail Website
Guest Editor

School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH, UK
Interests: cosmology; CMB; dark energy; modified gravity; neutrinos
Special Issues, Collections and Topics in MDPI journals

Prof. Alessandro Melchiorri

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Guest Editor

Department of Physics and Istituto Nazionale di Fisica Nucleare (INFN), University of Rome “La Sapienza”, Piazzale Aldo Moro 2, I-00815 Rome, Italy
Interests: cosmology; cosmic microwave background; large-scale structure; cosmological tensions; dark matter; dark energy; neutrino cosmology; modified gravity; cosmic inflation; gravitational waves

Prof. Olga Mena

E-Mail Website
Guest Editor

Instituto de Física Corpuscolar (IFIC), University of Valencia and CSIC, Parque Cientifico, c/Catedrático José Beltrán 2, E-46980 Paterna, Spain
Interests: cosmology; dark matter; dark energy; neutrino cosmology; modified gravity; astroparticle physics; neutrino oscillations; 21-cm cosmology; cosmic inflation; particle physics

Dr. Luca Visinelli

E-Mail Website
Guest Editor

Gravitation Astroparticle Physics Amsterdam (GRAPPA), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
Interests: cosmology; dark matter; dark energy; astroparticle physics; particle physics; cosmic inflation; axions; gravitational waves; black hole physics; Higgs physics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Thanks to a variety of astrophysical and cosmological observations, it has been established that the energy budget of the Universe is dominated by two dark components, whose origin and composition remain unknown: dark matter (DM) and dark energy (DE). One of the major tasks of cosmology, particle physics, and astrophysics in the coming years will be to unravel the nature of DM and DE both through joint and complementary efforts.

On the particle physics side, DM candidates are ubiquitous in extensions of the standard model of particle physics. However, DM has so far eluded discovery despite significant detection efforts, making it worth thinking of both alternative DM candidates, as well as novel detection methods. Moreover, the predictions of the collisionless cold DM paradigm appear to be in tension with galactic and sub-galactic structure observations (the so-called “small scale crisis”), which might be pointing towards a richer particle DM structure. From the particle physics point of view, the nature of DE is even more uncertain and no leading paradigm exists.

On the cosmological side, the ΛCDM standard cosmological model has been able to successfully explain a wide variety of observations ranging from cosmic microwave background radiation to the large-scale structure of the Universe. Yet, we know that ΛCDM cannot be the end of the story. Intriguingly, hints of cracks in the ΛCDM model have been appearing in relation to tensions between parameters determined from high- and low-redshift observations, such as the well-known Hubble constant tension. These tensions could be pointing towards a richer dark sector, especially on the DE side (for instance in the form of an early DE component, DM-DE interactions, or phase transitions in the DE).

Our goal in this Special Issue is to foster discussions to further understand the dark sector, including novel theoretical models, new detection ideas, and reviews on what the dark sector components might or might not be. We believe that a joint and complementary effort between particle physics, cosmology, and astrophysics, is vital to shedding light on the dark side of the Universe, and we, thus, especially encourage works at the interface of model building, phenomenology, and observations. Topics of interest to this Special Issue include (but are most certainly not limited to) the keywords summarized below. We welcome both original submissions and review papers, and look forward to your contributions!

Dr. Sunny Vagnozzi
Dr. Eleonora Di Valentino
Prof. Alessandro Melchiorri
Prof. Olga Mena
Dr. Luca Visinelli
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

Dark matter
Dark energy
Current and future cosmological and astrophysical observations
Experimental searches for dark matter and dark energy
Extensions of ΛCDM and beyond the standard model physics
Small-scale structure problems of ΛCDM
Cosmological tensions
Modified gravity
Self-interacting dark matter
Interacting dark energy

Published Papers (21 papers)

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15 pages, 361 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Gravitational Condensate Stars: An Alternative to Black Holes

by Pawel O. Mazur and Emil Mottola

Universe 2023, 9(2), 88; https://doi.org/10.3390/universe9020088 - 07 Feb 2023

Cited by 50 | Viewed by 2741

Abstract

A new final endpoint of complete gravitational collapse is proposed. By extending the concept of Bose–Einstein condensation to gravitational systems, a static, spherically symmetric solution to Einstein’s equations is obtained, characterized by an interior de Sitter region of

p = - ρ

gravitational [...] Read more.

p = - ρ

gravitational vacuum condensate and an exterior Schwarzschild geometry of arbitrary total mass M. These are separated by a phase boundary with a small but finite thickness ℓ, replacing both the Schwarzschild and de Sitter classical horizons. The resulting collapsed cold, compact object has no singularities, no event horizons, and a globally defined Killing time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of order

k_{B} ℓ M c / ℏ

, instead of the Bekenstein–Hawking entropy,

S_{B H} = 4 π k_{B} G M^{2} / ℏ c

. Unlike BHs, a collapsed star of this kind is consistent with quantum theory, thermodynamically stable, and suffers from no information paradox. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

16 pages, 569 KiB

Open AccessArticle

Scalar Field Models of Barrow Holographic Dark Energy in f(R,T) Gravity

by Umesh Kumar Sharma, Mukesh Kumar and Gunjan Varshney

Universe 2022, 8(12), 642; https://doi.org/10.3390/universe8120642 - 02 Dec 2022

Cited by 7 | Viewed by 1238

Abstract

This research study investigates Barrow holographic dark energy with an energy density of

ρ_{Λ} = C H^{2 - Δ}

by considering the Hubble horizon as the IR cut-off in the

f (R, T)

gravity framework. We employ Barrow [...] Read more.

This research study investigates Barrow holographic dark energy with an energy density of

ρ_{Λ} = C H^{2 - Δ}

by considering the Hubble horizon as the IR cut-off in the

f (R, T)

gravity framework. We employ Barrow holographic dark energy to obtain the equation of the state for the Barrow holographic energy density in a flat FLRW Universe. Concretely, we study the correspondence between quintessence, k-essence, and dilation scalar field models with the Barrow holographic dark energy in a flat

f (R, T)

Universe. Furthermore, we reconstruct the dynamics and potential for all these models for different values of the Barrow parameter:

Δ

. Via this study, we can show that for Barrow holographic quintessence, k-essence, and dilation scalar field models, if the corresponding model parameters satisfy some limitations, the accelerated expansion can be achieved. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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15 pages, 1166 KiB

Open AccessArticle

Bouncing Cosmology in Modified Gravity with Higher-Order Gauss–Bonnet Curvature Term

by Santosh V. Lohakare, Francisco Tello-Ortiz, S. K. Tripathy and B. Mishra

Universe 2022, 8(12), 636; https://doi.org/10.3390/universe8120636 - 29 Nov 2022

Cited by 5 | Viewed by 1137

Abstract

In this paper, we studied the bouncing behavior of the cosmological models formulated in the background of the Hubble function in the

F (R, G)

theory of gravity, where R and

G

, respectively, denote the Ricci scalar and Gauss–Bonnet [...] Read more.

In this paper, we studied the bouncing behavior of the cosmological models formulated in the background of the Hubble function in the

F (R, G)

theory of gravity, where R and

G

, respectively, denote the Ricci scalar and Gauss–Bonnet invariant. The actions of the bouncing cosmology are studied with a consideration of the different viable models that can resolve the difficulty of singularity in standard Big Bang cosmology. Both models show bouncing behavior and satisfy the bouncing cosmological properties. Models based on dynamical, deceleration, and energy conditions indicate the accelerating behavior at the late evolution time. The phantom at the bounce epoch is analogous to quintessence behavior. Finally, we formulate the perturbed evolution equations and investigate the stability of the two bouncing solutions. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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22 pages, 1058 KiB

Open AccessArticle

QCD Axion Kinetic Misalignment without Prejudice

by Basabendu Barman, Nicolás Bernal, Nicklas Ramberg and Luca Visinelli

Universe 2022, 8(12), 634; https://doi.org/10.3390/universe8120634 - 29 Nov 2022

Cited by 17 | Viewed by 983

Abstract

The axion field, the angular direction of the complex scalar field associated with the spontaneous symmetry breaking of the Peccei–Quinn (PQ) symmetry, could have originated with initial non-zero velocity. The presence of a non-zero angular velocity resulting from additional terms in the potential that explicitly break the PQ symmetry has important phenomenological consequences such as a modification of the axion mass with respect to the conventional PQ framework or an explanation for the observed matter-antimatter asymmetry. We elaborate further on the consequences of the “kinetic misalignment” mechanism, assuming that axions form the entirety of the dark matter abundance. The kinetic misalignment mechanism possesses a weak limit in which the axion field starts to oscillate at the same temperature as in the conventional PQ framework, and a strong limit corresponding to large initial velocities which effectively delay the onset of oscillations. Following a UV-agnostic approach, we show how this scenario impacts the formation of axion miniclusters, and we sketch the details of these substructures along with potential detecting signatures. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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13 pages, 389 KiB

Open AccessArticle

Scalar Weak Gravity Conjecture in Super Yang-Mills Inflationary Model

by Jafar Sadeghi, Mohammad Reza Alipour and Saeed Noori Gashti

Universe 2022, 8(12), 621; https://doi.org/10.3390/universe8120621 - 25 Nov 2022

Cited by 2 | Viewed by 985

Abstract

In this article, we want to check four inflation models, namely, composite NJL inflation (NJLI), Glueball inflation (GI), super Yang–Mills inflation (SYMI), and Orientifold inflation (OI), with two conjectures of the swampland program: scalar weak gravity conjecture (SWGC) and strong scalar weak gravity conjecture (SSWGC) since all these models violate the dS swampland conjecture (DSC) but are compatible with further refining de Sitter swampland conjecture (FRDSSC) through manual adjustment of free parameters of the mentioned conjecture. We want to study the simultaneous compatibility of each model with these two new conjectures. Despite being consistent with (FRDSSC), we find that all models are not compatible with the other conjectures of the Swampland program in all regions, and these conjectures are only satisfied in a specific area. Moreover, due to the presence of constant parameter

(ϕ_{0})

in the higher orders derivatives, the (SYMI) and (OI) among all the models are more compatible with all conjectures of the swampland program. These models can provide a more significant amount of satisfaction with all of them. They can be suitable and accurate inflation models for a more profound examination of universe developments. We determined a particular region for these models is compatible with (FRDSSC), (SWGC), and (SSWGC) simultaneously. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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15 pages, 685 KiB

Open AccessArticle

Does Lorentz Relativistic Mass Make Dark Energy Superfluous?

by Espen Gaarder Haug

Universe 2022, 8(11), 577; https://doi.org/10.3390/universe8110577 - 02 Nov 2022

Cited by 1 | Viewed by 4691

Abstract

This paper shows that a simple and relativistic extension of Newtonian gravity that takes into account Lorentz relativistic mass leads to predictions that fit supernova observations of magnitude versus redshift without the need to introduce dark energy. To test the concept, we look at 580 supernova data points from the Union2 database. Some relativistic extensions of Newtonian gravity have been investigated in the past, but we have reason to believe the efforts were rejected prematurely before their full potential was investigated. Our model suggests that mass, as related to gravity, is also affected by Lorentz relativistic effects, something that is not the case in standard gravity theory, and this adjustment gives supernova predictions that fit the observations. Our model seems very robust with respect to supernova data, as no arbitrary parameters are introduced. Since recent investigations of Lorentz’s relativistic mass also seem to solve other challenges in physics, we think it is worthwhile for the physics community to look into this more carefully, at least before rejecting it based on prejudice. After all, no one has been able to detect dark energy despite massive efforts to do so. Until dark energy is really confirmed, other alternative models should be worth investigating further. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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21 pages, 859 KiB

Open AccessArticle

k-Essence Inflation Evading Swampland Conjectures and Inflationary Parameters

by Abdul Jawad, Shamaila Rani, Abdul Malik Sultan and Kashaf Embreen

Universe 2022, 8(10), 532; https://doi.org/10.3390/universe8100532 - 14 Oct 2022

Cited by 3 | Viewed by 1000

Abstract

In this paper, we study the inflationary scenario in the realm of k-essence model and swampland conjectures. Taking into account three models of Chaplygin gas, such as generalized, modified, and generalized cosmic Chaplygin gas models, we discuss the equation of state (EoS) [...] Read more.

ω

, slow roll parameters

(ϵ (ϕ), η (ϕ))

, curvature perturbation

(P_{s})

, tensor to scalar ratio

(r)

, and scalar spectral index

(n_{s})

. As regards the k-essence model, the coupling function as a function of scalar field

L (ϕ)

is used. We investigate the swampland conjecture and then find the value of

ζ (ϕ)

, i.e., bound of second conjecture for these three models by unifying swampland conjecture and k-essence. We plot the EoS parameter

ω

, inflationary parameters plane

r - n_{s}

and bound of swampland conjecture

ζ (ϕ) - ϕ

, which determine that the values of

ω < - 1

for each model, r, are

r < 0.0094, r \leq 0.0065, r \leq 0.0067

, and ranges for

n_{s}

are

[0.934, 0.999], [0.9, 0.999], [0.9, 0.992]

for generalized, modified, and generalized cosmic Chaplygin gas models, respectively, and compare their compatibility with the Planck data from 2018. Furthermore, we determine the bound for swampland conjecture as

ζ (ϕ) \leq 0.992, ζ (ϕ) \leq 0.964, ζ (ϕ) \leq 0.964

for generalized, modified and generalized cosmic Chaplygin gas models, respectively. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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45 pages, 2556 KiB

Open AccessArticle

A Reanalysis of the Latest SH0ES Data for H₀: Effects of New Degrees of Freedom on the Hubble Tension

by Leandros Perivolaropoulos and Foteini Skara

Universe 2022, 8(10), 502; https://doi.org/10.3390/universe8100502 - 25 Sep 2022

Cited by 22 | Viewed by 1296

Abstract

We reanalyze in a simple and comprehensive manner the recently released SH0ES data for the determination of

H_{0}

. We focus on testing the homogeneity of the Cepheid+SnIa sample and the robustness of the results in the presence of new degrees of [...] Read more.

We reanalyze in a simple and comprehensive manner the recently released SH0ES data for the determination of

H_{0}

. We focus on testing the homogeneity of the Cepheid+SnIa sample and the robustness of the results in the presence of new degrees of freedom in the modeling of Cepheids and SnIa. We thus focus on the four modeling parameters of the analysis: the fiducial luminosity of SnIa

M_{B}

and Cepheids

M_{W}

and the two parameters (

b_{W}

and

Z_{W}

) standardizing Cepheid luminosities with period and metallicity. After reproducing the SH0ES baseline model results, we allow for a transition of the value of any one of these parameters at a given distance

D_{c}

or cosmic time

t_{c}

, thus adding a single degree of freedom in the analysis. When the SnIa absolute magnitude

M_{B}

is allowed to have a transition at

D_{c} ≃ 50

Mpc (about 160 Myrs ago), the best-fit value of the Hubble parameter drops from

H_{0} = 73.04 \pm 1.04

km s

^{- 1}

Mpc

^{- 1}

H_{0} = 67.32 \pm 4.64

km s

^{- 1}

Mpc

^{- 1}

in full consistency with the Planck value. Additionally, the best-fit SnIa absolute magnitude

M_{B}^{>}

for

D > D_{c}

drops to the Planck inverse distance ladder value

M_{B}^{>} = - 19.43 \pm 0.15

, while the low distance best fit

M_{B}^{<}

parameter remains close to the original distance ladder calibrated value

M_{B}^{<} = - 19.25 \pm 0.03

. Similar hints for a transition behavior is found for the other three main parameters of the analysis (

b_{W}

M_{W}

and

Z_{W}

) at the same critical distance

D_{c} ≃ 50

Mpc, even though in that case, the best-fit value of

H_{0}

is not significantly affected. When the inverse distance ladder constraint on

M_{B}^{>}

is included in the analysis, the uncertainties for

H_{0}

reduce dramatically (

H_{0} = 68.2 \pm 0.8

km s

^{- 1}

Mpc

^{- 1}

), and the

M_{B}

transition model is strongly preferred over the baseline SH0ES model (

Δ χ^{2} ≃ - 15

Δ A I C ≃ - 13

) according to the AIC and BIC model selection criteria. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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12 pages, 928 KiB

Open AccessArticle

Phase Space Analysis of Barrow Agegraphic Dark Energy

by Hai Huang, Qihong Huang and Ruanjing Zhang

Universe 2022, 8(9), 467; https://doi.org/10.3390/universe8090467 - 07 Sep 2022

Cited by 4 | Viewed by 1303

Abstract

Using the Barrow entropy and considering the timescale as IR cutoff, a new holographic dark energy model named Barrow agegraphic dark energy (BADE) was proposed. We use phase space analysis method to discuss the evolution of the universe in three different mode of [...] Read more.

Q = 0

;

Q = 3 α H (ρ_{m} + ρ_{D})

;

Q = H (α ρ_{m} + β ρ_{D})

). We find the attractor which represents the dark energy-dominated era exists in all cases. In the case

Q = 0

and

Q = H (α ρ_{m} + β ρ_{D})

with

β = 0

, the attractor can behave as the cosmological constant, and these models can used to mimic the cosmological constant. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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20 pages, 5279 KiB

Open AccessArticle

Dark Energy from Virtual Gravitons (GCDM Model vs. ΛCDM Model)

by L. S. Marochnik and D. A. Usikov

Universe 2022, 8(9), 464; https://doi.org/10.3390/universe8090464 - 07 Sep 2022

Viewed by 1291

Abstract

The dark energy from virtual gravitons is consistent with observational data on supernovas with the same accuracy as the ΛCDM model. The fact that virtual gravitons are capable of producing a de Sitter accelerated expansion of the FLRW universe was established in 2008 (see references). The combination of conformal non-invariance with zero rest mass of gravitons (unique properties of the gravitational field) leads to the appearance of graviton dark energy in a mater-dominated era; this fact explains the relatively recent appearance of the dark energy and answers the question “Why now?”. The transition redshifts (where deceleration is replaced by acceleration) that follow from the graviton theory are consistent with model-independent transition redshifts derived from observational data. Prospects for testing the GCDM model (the graviton model of dark energy where G stands for gravitons) and comparison with the ΛCDM model are discussed. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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10 pages, 276 KiB

Open AccessArticle

General Thermodynamic Properties of FRW Universe and Heat Engine

by Ujjal Debnath

Universe 2022, 8(8), 400; https://doi.org/10.3390/universe8080400 - 29 Jul 2022

Cited by 1 | Viewed by 921

Abstract

In this work, the Friedmann–Robertson–Walker (FRW) Universe is considered a thermodynamic system, where the cosmological constant generates the thermodynamic pressure. Using a unified first law, we have determined the amount of energy

d E

crossing the apparent horizon. Since heat is one of [...] Read more.

d E

crossing the apparent horizon. Since heat is one of the forms of thermal energy, so the heat flows

δ Q

through the apparent horizon = amount of energy crossing the apparent horizon. Using the first law of thermodynamics, on the apparent horizon, we found

T d S = A (ρ + p) H {\tilde{r}}_{h} d t + A ρ d {\tilde{r}}_{h}

where

T, S, A, H, {\tilde{r}}_{h}, ρ, p

are respectively the temperature, entropy, area, Hubble parameter, horizon radius, fluid density and pressure. Since the apparent horizon is dynamical, so we have assumed that

d {\tilde{r}}_{h}

cannot be zero in general, i.e., the second term

A ρ d {\tilde{r}}_{h}

is non-zero on the apparent horizon. Using Friedmann equations with the unified first law, we have obtained the modified entropy-area relation on the apparent horizon. In addition, from the modified entropy-area relation, we have obtained modified Friedmann equations. From the original Friedmann equations and also from modified Friedmann equations, we have obtained the same entropy. We have derived the equations for the main thermodynamical quantise, such as temperature, volume, mass, specific heat capacity, thermal expansion, isothermal compressibility, critical temperature, critical volume, critical pressure and critical entropy. To determine the cooling/heating nature of the FRW Universe, we have obtained the coefficient of Joule–Thomson expansion. Next, we have discussed the heat engine phenomena of the thermodynamical FRW Universe. We have considered the Carnot cycle and obtained its completed work. In addition, we studied the work completed and the thermal efficiency of the new heat engine. Finally, we have obtained the thermal efficiency of the Rankine cycle. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

13 pages, 276 KiB

Open AccessArticle

Anisotropic Multiverse with Varying c and G and Study of Its Thermodynamics

by Ujjal Debnath and Soumak Nag

Universe 2022, 8(8), 398; https://doi.org/10.3390/universe8080398 - 29 Jul 2022

Cited by 3 | Viewed by 928

Abstract

We assume the anisotropic model of the Universe in the framework of a varying speed of light c and a varying gravitational constant G theories and study different types of singularities. We write the scale factors for the singularity models in terms of cosmic time and find some conditions for possible singularities. For future singularities, we assume the forms of a varying speed of light and varying gravitational constant. For regularizing the Big Bang singularity, we assume two forms of scale factors: the sine model and the tangent model. For both models, we examine the validity of null and strong energy conditions. Starting from the first law of thermodynamics, we study the thermodynamic behaviors of a number n of universes (i.e., multiverse) for (i) varying c, (ii) varying G and (iii) varying both c and G models. We find the total entropies for all the cases in the anisotropic multiverse model. We also find the nature of the multiverse if the total entropy is constant. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

4 pages, 223 KiB

Open AccessCommunication

Using Neutrino Oscillations to Measure H₀?

by Luis A. Anchordoqui

Universe 2022, 8(7), 377; https://doi.org/10.3390/universe8070377 - 11 Jul 2022

Viewed by 941

Abstract

Recently, the idea of using neutrino oscillations to measure the Hubble constant was introduced. We show that such a task is unfeasible because for typical energies of cosmic neutrinos, oscillations average out over cosmological distances and so the oscillation probability depends only on [...] Read more.

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

9 pages, 245 KiB

Open AccessArticle

Accelerated Universe from Modified Chaplygin Gas and Tachyonic Fluid

by Hachemi Benaoum

Universe 2022, 8(7), 340; https://doi.org/10.3390/universe8070340 - 21 Jun 2022

Cited by 16 | Viewed by 1300

Abstract

A cosmological model with an exotic fluid is investigated. We show that the equation of state of this “modified Chaplygin” gas can describe the current accelerated expansion of the universe. We then reexpress it as FRW cosmological model containing a scalar field

ϕ

[...] Read more.

ϕ

and find its self-interacting potential. Moreover motivated by recent works on tachyon field theory, a map for this exotic fluid as a normal scalar field

ϕ

with Lagrangian

L_{ϕ} = \frac{{\dot{ϕ}}^{2}}{2} - U (ϕ)

to the tachyonic field T with Lagrangian

L_{T} = - V (T) \sqrt{1 - {\dot{T}}^{2}}

is obtained. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

5 pages, 252 KiB

Open AccessCommunication

A Note on Proton Stability in the Standard Model

by Seth Koren

Universe 2022, 8(6), 308; https://doi.org/10.3390/universe8060308 - 30 May 2022

Cited by 6 | Viewed by 1250

Abstract

In this short note, we describe the symmetry responsible for absolute, nonperturbative proton stability in the Standard Model. The SM with

N_{c}

colors and

N_{g}

generations has an exact, anomaly-free, generation-independent, global symmetry group [...] Read more.

In this short note, we describe the symmetry responsible for absolute, nonperturbative proton stability in the Standard Model. The SM with

N_{c}

colors and

N_{g}

generations has an exact, anomaly-free, generation-independent, global symmetry group

U {(1)}_{B - N_{c} L} \times Z_{N_{g}}^{L}

, which contains a subgroup of baryon plus lepton number of order

2 N_{c} N_{g}

. This disallows proton decay for

N_{g} > 1

. Many well-studied models beyond the SM explicitly break this global symmetry, and the alternative deserves further attention. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

13 pages, 778 KiB

Open AccessArticle

Weak Deflection Angle and Greybody Bound of Magnetized Regular Black Hole

by Wajiha Javed, Sibgha Riaz and Ali Övgün

Universe 2022, 8(5), 262; https://doi.org/10.3390/universe8050262 - 25 Apr 2022

Cited by 13 | Viewed by 1674

Abstract

In this paper, we examine the weak deflection angle and greybody bound for a magnetized regular black hole. For this purpose, we apply the Gauss–Bonnet theorem on the black hole and obtain the deflection angle in plasma and non-plasma mediums. Moreover, we investigate graphically the effect of impact parameter on the deflection angle for regular black hole in both mediums. We examine that the deflection angle goes to infinity when the impact parameter approaches zero. We also observe that the deflection angle shows negative behaviour at

q = 0.6

and

q = 2.09

, but at

0.6 < q < 2.09

, the angle shows positive behaviour. Furthermore, we study the rigorous bound phenomenon of the greybody factor in the background for a magnetized regular black hole. Later, we analyse the graphical behaviour of greybody bound with respect to different values of

ω

and observe that, at small values of

ω

, the bound increases, but for large values, the bound decreases. After that, we examine that, when we put

G = 1

l = 0

and

q = 0

, all results for the magnetized regular black hole solution reduce into results of the Schwarzschild black hole solution. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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16 pages, 630 KiB

Open AccessArticle

Nonsingular Black Holes in 4D Einstein–Gauss–Bonnet Gravity

by Arun Kumar, Dharmanand Baboolal and Sushant G. Ghosh

Universe 2022, 8(4), 244; https://doi.org/10.3390/universe8040244 - 14 Apr 2022

Cited by 10 | Viewed by 1828

Abstract

Recently, several methods have been proposed to regularize a

D \to 4

limit of Einstein–Gauss–Bonnet (EGB), leading to nontrivial gravitational dynamics in

4 D

. We present an exact nonsingular black hole solution in the

4 D

EGB gravity coupled to non-linear electrodynamics [...] Read more.

Recently, several methods have been proposed to regularize a

D \to 4

limit of Einstein–Gauss–Bonnet (EGB), leading to nontrivial gravitational dynamics in

4 D

. We present an exact nonsingular black hole solution in the

4 D

EGB gravity coupled to non-linear electrodynamics and analyze their thermodynamic properties to calculate precise expressions for the black hole mass, temperature, and entropy. Because of the magnetic charge, the thermodynamic quantities are corrected, and the Hawking–Page phase transition is achievable with diverges of the heat capacity at a larger critical radius

r = r_{+}^{C}

in comparison to the

5 D

counterpart where the temperature is maximum. Thus, we have a black hole with Cauchy and event horizons, and its evaporation leads to a thermodynamically stable extremal black hole remnant with vanishing temperature, and its size is larger than the

5 D

counterpart. The entropy does not satisfy the usual exact horizon Bekenstein–Hawking area law of general relativity with a logarithmic area correction term. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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14 pages, 539 KiB

Open AccessArticle

Bardeen Black Holes in the Regularized 4D Einstein–Gauss–Bonnet Gravity

by Arun Kumar, Rahul Kumar Walia and Sushant G. Ghosh

Universe 2022, 8(4), 232; https://doi.org/10.3390/universe8040232 - 10 Apr 2022

Cited by 16 | Viewed by 1704

Abstract

We obtain exact Bardeen black holes to the regularized

4 D

Einstein–Gauss–Bonnet (EGB) gravity minimally coupled with the nonlinear electrodynamics (NED). In turn, we analyze the horizon structure to determine the effect of GB parameter

α

on the minimum cutoff values of mass, [...] Read more.

We obtain exact Bardeen black holes to the regularized

4 D

Einstein–Gauss–Bonnet (EGB) gravity minimally coupled with the nonlinear electrodynamics (NED). In turn, we analyze the horizon structure to determine the effect of GB parameter

α

on the minimum cutoff values of mass,

M_{0}

, and magnetic monopole charge,

g_{0}

, for the existence of a black hole horizon. We obtain an exact expression for thermodynamic quantities, namely, Hawking temperature

T_{+}

, entropy

S_{+}

, Helmholtz free energy

F_{+}

, and specific heat

C_{+}

associated with the black hole horizon, and they show significant deviations from the

4 D

EGB case owing to NED. Interestingly, there exists a critical value of horizon radius,

r_{+}^{c}

, corresponding to the local maximum of Hawking temperature, at which heat capacity diverges, confirming the second-order phase transition. A discussion on the black holes of alternate regularized

4 D

EGB gravity belonging to the scalar-tensor theory is appended. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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15 pages, 4696 KiB

Open AccessArticle

Directional Observation of Cold Dark Matter Particles (WIMP) in Light Target Experiments

by Anna Anokhina, Vasilisa Gulyaeva, Emil Khalikov, Evgeny Kurochkin, Tatiana Roganova, Eduard Ursov and Ivan Vidulin

Universe 2021, 7(7), 215; https://doi.org/10.3390/universe7070215 - 28 Jun 2021

Cited by 1 | Viewed by 1875

Abstract

For the last 10 years, the search for dark matter (DM) was carried out taking into account the fact that the DM particles are WIMPs (Weakly Interacted Massive Particles) which were introduced in supersymmetric extensions of the Standard Model. Many experiments such as XENON1T, DarkSide, CRESST, etc. set the constraints on the WIMP-nucleon elastic interaction cross sections for different assumed WIMP masses. Methods for detecting WIMPs could play a special role, allowing one to determine the directions of the tracks of recoil nuclei and, therefore, to determine the preferred direction of the WIMP flux. In this work, we analyze the capabilities of such direct detection experiments through analyzing the lengths and directions of the tracks of recoil nuclei. Taking into account the existing experimental constraints, we conclude that the optimal target would be a lower density target containing nuclei of the CNO group, for example, liquid propane. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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25 pages, 6483 KiB

Open AccessArticle

A Table-Top Pilot Experiment for Narrow Mass Range Light Cold Dark Matter Particle Searches

by Masroor H. S. Bukhari

Universe 2020, 6(2), 28; https://doi.org/10.3390/universe6020028 - 03 Feb 2020

Cited by 1 | Viewed by 3269

Abstract

This report presents the detection framework and a proposal for a pilot table-top experiment (supported by simulations and preliminary test results) for adoption into narrow mass range light Cold Dark Matter (CDM) searches, specifically for axions or Axion-Like Particles (ALPs) in a resonant cavity-based scheme. The novelty of this proposal lies in an attempt to concentrate searches corresponding to specific axion masses of interest (coinciding with recent proposals), using multiple cavities in a symmetric scheme, instead of using noisy and complicated tuning mechanisms, and in reduction of associated hardware by employing simpler underlying instrumentation instead of heterodyne mode of detection, by means of a low-noise ac amplification and dc phase-sensitive detection scheme, in order to make a viable and compact table-top experiment possible. These simplifications could possibly be valuable in substantially reducing detection hardware, experiment complexities (and associated noise) and long run-times, while maintaining low noise similar to conventional axion searches. The feasibility of proposed scheme and the experiment design are demonstrated with some calculations, simulations and preliminary tests with artificial axion signals injected into the cavities. The technique and ideas reported here have significant potential to be developed into a small-scale table-top, narrow-range, dark matter axion/ALP spectroscopy experiment, in addition to aiding in the on-going resonant cavity-based and broadband experiments. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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Review

Jump to: Research

16 pages, 1755 KiB

Open AccessReview

Two Sides of the Same Coin: Sterile Neutrinos and Dark Radiation, Status and Perspectives

by Maria Archidiacono and Stefano Gariazzo

Universe 2022, 8(3), 175; https://doi.org/10.3390/universe8030175 - 10 Mar 2022

Cited by 13 | Viewed by 2190

Abstract

The presence of light sterile neutrinos is one of the unanswered questions of particle physics. The cosmological counterpart is represented by dark radiation, i.e., any form of radiation present in the early Universe besides photons and standard (active) neutrinos. This short review provides a comprehensive overview of the two problems and of their connection. We review the status of neutrino oscillation anomalies, commenting on the most recent oscillation data and their mutual tensions, and we discuss the constraints from other terrestrial probes. We show the shortcomings of translating light sterile neutrinos in cosmology as additional thermalised relativistic species, produced by neutrino oscillations, and we detail alternative solutions, specifically focusing on neutrino nonstandard interactions, and on their link to the Hubble constant problem. The impact of a new force leading to dark radiation–dark matter interactions is also discussed in the realm of new physics in the dark sector. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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