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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 (30 November 2022) | Viewed by 7967

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Special Issue Editors

Prof. Dr. Maxim Y. Khlopov

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Guest Editor

1. Institute of Nuclear Physics and Engineering, National Research Nuclear University MEPhI, 115409 Moscow, Russia
2. Director of Virtual Institute of Astroparticle Physics, Université de Paris, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France
3. Principal Researcher Institute of Physics, Southern Federal University, 344006 Rostov on Don, Russia
Interests: cosmoparticle physics; cosmology and particle physics; physics of dark matter and the early universe; physics beyond the standard model
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Antonino Marciano

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Guest Editor

Center for Field Theory and Particle Physics and Department of Physics, Fudan University, Shanghai 200433, China
Interests: early cosmology; inflation; dark energy; quantum comsology and quantum gravity; quantum gravity phenomenology
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Andrea Addazi

E-Mail Website
Guest Editor

Department of Physics, Sichuan University, Sichuan 610017,China
Interests: particle physics; cosmology; physics beyond the standard model; dark matter

Special Issue Information

Dear Colleagues,

Dark matter is one of the basic cornerstones of the modern theory of structure, and the evolution of the universe and its physical nature is among the hottest topics of modern fundamental physics. At the microscopic level, dark matter should represent new stable forms of particles. Originating from the very early universe, it reflects the existence of processes, governed by the (unknown) laws of ultra-high energy physics. Being dominant in the matter content of the modern universe, it still remains enigmatic for its direct and indirect searches. We focus in this issue on the possible physical nature of dark matter in its relationship with physics beyond the standard model and physics of the very early universe and the ways to probe this nature in underground, collider, and cosmic ray experiments, as well as in astronomical and astrophysical data. We invite authors to contribute to this issue and to help us to make a step in the attempt to shed light on this dark side of the modern Universe.

Prof. Dr. Maxim Yu. Khlopov
Prof. Dr. Antonino Marciano
Prof. Dr. Andrea Addazi
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.

Published Papers (6 papers)

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Research

Open AccessCommunication

Proposition of FSR Photon Suppression Employing a Two-Positron Decay Dark Matter Model to Explain Positron Anomaly in Cosmic Rays

Ramin Barak

Konstantin Belotsky

and

Ekaterina Shlepkina

Universe 2023, 9(8), 370; https://doi.org/10.3390/universe9080370 - 15 Aug 2023

Viewed by 415

Abstract

The origin of an anomalous excess of high-energy (about 100 GeV and higher) positrons in cosmic rays is one of the rare problems in this field, which is proposed to be solved with dark matter (DM). Attempts to solve this problem are faced with the issue of having to satisfy the data on cosmic positrons and cosmic gamma radiation, which inevitably accompanies positron production, such as FSR (final state radiation), simultaneously. We have been trying to come up with a solution by means of two approaches: making assumptions (*) about the spatial distribution of the dark matter and (**) about the physics of its interactions. This work is some small final step of a big investigation regarding the search for gamma suppression by employing the second approach, and a model with a doubly charged particle decaying into two positrons (

X^{+ +} \to e^{+} e^{+}

) is suggested as the most prospective one from those considered before. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

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Open AccessArticle

Assessment of Dark Matter Models Using Dark Matter Correlations across Dwarf Spheroidal Galaxies

Ahmad Borzou

Universe 2022, 8(7), 386; https://doi.org/10.3390/universe8070386 - 21 Jul 2022

Cited by 1 | Viewed by 813

Abstract

The predicted size of dark matter substructures in kilo-parsec scales is model-dependent. Therefore, if the correlations between dark matter mass densities as a function of the distances between them are measured via observations, we can scrutinize dark matter scenarios. In this paper, we present an assessment procedure of dark matter scenarios. First, we use Gaia’s data to infer the single-body phase-space density of the stars in the Fornax dwarf spheroidal galaxy. The latter, together with the Jeans equation, after eliminating the gravitational potential using the Poisson equation, reveals the mass density of dark matter as a function of its position in the galaxy. We derive the correlations between dark matter mass densities as a function of distances between them. No statistically significant correlation is observed. Second, for the sake of comparison with the standard cold dark matter, we also compute the correlations between dark matter mass densities in a small halo of the Eagle hydrodynamics simulation. We show that the correlations from the simulation and from Gaia are in agreement. Third, we show that Gaia observations can be used to limit the parameter space of the Ginzburg–Landau statistical field theory of dark matter mass densities and subsequently shrink the parameter space of any dark matter model. As two examples, we show how to leave limitations on (i) a classic gas dark matter and (ii) a superfluid dark matter. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

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Open AccessArticle

Antistars or Antimatter Cores in Mirror Neutron Stars?

Zurab Berezhiani

Universe 2022, 8(6), 313; https://doi.org/10.3390/universe8060313 - 31 May 2022

Cited by 9 | Viewed by 1240

Abstract

The oscillation of the neutron n into mirror neutron

n^{'}

The oscillation of the neutron n into mirror neutron

n^{'}

, its partner from the dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process taking place in the mirror neutron stars depend on the sign of baryon asymmetry in the mirror sector. Namely, if it is negative, as predicted by certain baryogenesis scenarios, then

\bar{n^{'}} - \bar{n}

transitions create a core of our antimatter gravitationally trapped in the mirror star interior. The annihilation of accreted gas on such antimatter cores could explain the origin of

γ

-source candidates with an unusual spectrum compatible with baryon–antibaryon annihilation, recently identified in the Fermi LAT catalog. In addition, some part of this antimatter escaping after the mergers of mirror neutron stars can produce the flux of cosmic antihelium and also heavier antinuclei which are hunted in the AMS-02 experiment. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

Open AccessArticle

Modified Equations of State for Dark Energy and Observational Limitations

German S. Sharov

and

Vasily E. Myachin

Universe 2022, 8(4), 201; https://doi.org/10.3390/universe8040201 - 24 Mar 2022

Cited by 4 | Viewed by 1387

Abstract

Cosmological models with variable and modified equations of state for dark energy are confronted with observational data, including Type Ia supernovae, Hubble parameter data

H (z)

from different sources, and observational manifestations of cosmic microwave background radiation (CMB). We consider scenarios [...] Read more.

Cosmological models with variable and modified equations of state for dark energy are confronted with observational data, including Type Ia supernovae, Hubble parameter data

H (z)

from different sources, and observational manifestations of cosmic microwave background radiation (CMB). We consider scenarios generalizing the

Λ

CDM, wCDM, and Chevallier–Polarski–Linder (CPL) models with nonzero curvature and compare their predictions. The most successful model with the dark energy equation of state

w = w_{0} + w_{1} (1 - a^{2}) / 2

was studied in detail. These models are interesting in possibly alleviating the Hubble constant

H_{0}

tension, but they achieved a modest success in this direction with the considered observational data. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

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Open AccessCommunication

A Dark Matter WIMP That Can Be Detected and Definitively Identified with Currently Planned Experiments

Diego Cristancho Guerrero

Jessica Jaksik

Drue Lubanski

and

Roland Allen

Universe 2021, 7(8), 270; https://doi.org/10.3390/universe7080270 - 27 Jul 2021

Cited by 6 | Viewed by 1425

Abstract

A recently proposed dark matter WIMP (weakly interacting massive particle) has only second-order couplings to gauge bosons and itself. As a result, it has small annihilation, scattering, and creation cross-sections, and is consequently consistent with all current experiments and the observed abundance of dark matter. These cross-sections are, however, still sufficiently large to enable detection in experiments that are planned for the near future, and definitive identification in experiments proposed on a longer time scale. The (multi-channel) cross-section for annihilation is consistent with thermal production and freeze-out in the early universe, and with current evidence for dark matter annihilation in analyses of the observations of gamma rays by Fermi-LAT and antiprotons by AMS-02, as well as the constraints from Planck and Fermi-LAT. The cross-section for direct detection via collision with xenon nuclei is estimated to be slightly below

10^{- 47}

^{2}

, which should be attainable by LZ and Xenon nT and well within the reach of Darwin. The cross-section for collider detection via vector boson fusion is estimated to be ∼1 fb, and may be ultimately attainable by the high-luminosity LHC; definitive collider identification will probably require the more powerful facilities now being proposed. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

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Figure 1

Open AccessArticle

Hyperfine Splitting of Excited States of New Heavy Hadrons and Low-Energy Interaction of Hadronic Dark Matter with Photons, Nucleons, and Leptons

Vladimir Kuksa

and

Vitaly Beylin

Universe 2020, 6(6), 84; https://doi.org/10.3390/universe6060084 - 19 Jun 2020

Cited by 6 | Viewed by 1262

Abstract

We consider the structure of excited states and low-energy interaction of hadronic dark matter with photons, leptons, and nucleons. Description of the lowest excited levels is fulfilled in an analogy with the standard heavy-light mesons. Using the effective vertex of new heavy hadrons interaction with W-boson, we calculate cross-section of the lepton scattering on the dark matter particle. Analysis of strong low-energy interaction of new hadrons was carried out within the effective meson-exchange model based on dynamical realization of SU(3)-symmetry. A cross-section of nucleon scattering on the hadronic dark matter was also calculated using this model. The most essential phenomenological consequences of the low-energy dark matter interaction with leptons and nucleons are discussed. Full article

(This article belongs to the Special Issue Focus on Dark Matter)

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