Particles

11 pages, 383 KB

Open AccessArticle

Determining the Ground State for Superheavy Nuclei from the Deformed Relativistic Hartree–Bogoliubov Theory in Continuum

by Sibo Wang, Peng Guo and Cong Pan

Particles 2024, 7(4), 1139-1149; https://doi.org/10.3390/particles7040070 - 23 Dec 2024

Cited by 4 | Viewed by 1093

Abstract

The deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) has garnered significant attention for its ability to describe the properties of nuclei across the entire nuclear chart, from light to heavy nuclei, including both stable and exotic ones. As part of ongoing efforts to [...] Read more.

The deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) has garnered significant attention for its ability to describe the properties of nuclei across the entire nuclear chart, from light to heavy nuclei, including both stable and exotic ones. As part of ongoing efforts to construct a mass table using the DRHBc theory, determining the ground states of nuclei is a crucial task in the systematic studies of deformed nuclei. In this work, a strategy for identifying the ground state in the superheavy nuclei region is proposed and evaluated, by taking

Z = 134

and 135 isotopes as examples. First, we examine how the step size of the initial quadrupole deformation parameter,

Δ β_{2}

, affects the pattern of the potential energy curves (PECs) and the determination of the ground state. Our findings indicate that

Δ β_{2} = 0.05

producing smooth and well-defined PECs while maintaining an acceptable numerical cost. Next, we explore the convergence of PECs with respect to the angular momentum cutoff,

J_{\max}

. Based on the results, we recommend using

J_{\max} = 31 / 2 ℏ

, especially for nuclei with competing oblate and prolate minima. Finally, we conclude that the accurate identification of the ground state can be achieved by performing unconstrained calculations around the minima of the PECs. Full article

(This article belongs to the Special Issue Selected Papers from the “7th Workshop on the Nuclear Mass Table with DRHBc Theory”)

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11 pages, 1378 KB

Open AccessArticle

Giant Halo in ⁶⁶Ca Within Relativistic Continuum Hartree–Bogoliubov Theory Combined with Lipkin–Nogami Method

by Chang Zhou, Peng Guo and Xiaofei Jiang

Particles 2024, 7(4), 1128-1138; https://doi.org/10.3390/particles7040069 - 21 Dec 2024

Cited by 2 | Viewed by 975

Abstract

The impact of the Lipkin–Nogami (LN) method on a giant halo is investigated within the relativistic continuum Hartree–Bogoliubov (RCHB) theory. The ground-state properties of Ca isotopes obtained from RCHB and RCHB+LN calculations are presented. The results show that the LN correction does not [...] Read more.

The impact of the Lipkin–Nogami (LN) method on a giant halo is investigated within the relativistic continuum Hartree–Bogoliubov (RCHB) theory. The ground-state properties of Ca isotopes obtained from RCHB and RCHB+LN calculations are presented. The results show that the LN correction does not change the range of Ca isotopes with a giant halo. Taking ⁶⁶Ca as an example, the neutron density distribution with LN correction is found to be slightly more diffused, which can be illustrated by the enlargement of the root mean square radius and the enhancement of the relative contribution in neutron

3 s_{1 / 2}

level. Full article

(This article belongs to the Special Issue Selected Papers from the “7th Workshop on the Nuclear Mass Table with DRHBc Theory”)

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8 pages, 242 KB

Open AccessArticle

FRW Cosmology with Chiral Tensor Particles

by Daniela Kirilova, Emanuil Chizhov and Mihail Chizhov

Particles 2024, 7(4), 1120-1127; https://doi.org/10.3390/particles7040068 - 19 Dec 2024

Viewed by 673

Abstract

We discuss an extended model of FRW cosmology with additional chiral tensor particles. We discuss the influence of these particles on the expansion rate of the Universe, their direct interactions with the constituents of the early Universe plasma, we determine their cosmological place [...] Read more.

We discuss an extended model of FRW cosmology with additional chiral tensor particles. We discuss the influence of these particles on the expansion rate of the Universe, their direct interactions with the constituents of the early Universe plasma, we determine their cosmological place and derive updated cosmological constraints on their interaction strength. Full article

(This article belongs to the Special Issue Selected Papers from "The Modern Physics of Compact Stars and Relativistic Gravity 2023")

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25 pages, 511 KB

Open AccessArticle

On the Exact Solution for the Schrödinger Equation

by Yair Mulian

Particles 2024, 7(4), 1095-1119; https://doi.org/10.3390/particles7040067 - 12 Dec 2024

Viewed by 2539

Abstract

For almost 75 years, the general solution for the Schrödinger equation was assumed to be generated by an exponential or a time-ordered exponential known as the Dyson series. We study the unitarity of a solution in the case of a singular Hamiltonian and [...] Read more.

For almost 75 years, the general solution for the Schrödinger equation was assumed to be generated by an exponential or a time-ordered exponential known as the Dyson series. We study the unitarity of a solution in the case of a singular Hamiltonian and provide a new methodology that is not based on the assumption that the underlying space is

L^{2} (R)

. Then, an alternative operator for generating the time evolution that is manifestly unitary is suggested, regardless of the choice of Hamiltonian. The new construction involves an additional positive operator that normalizes the wave function locally and allows us to preserve unitarity, even when dealing with infinite dimensional or non-normed spaces. Our considerations show that Schrödinger and Liouville equations are, in fact, two sides of the same coin and together they provide a unified description for unbounded quantum systems. Full article

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9 pages, 983 KB

Open AccessArticle

Exploring the Neutron Magic Number in Superheavy Nuclei: Insights into N = 258

by Pengxiang Du and Jian Li

Particles 2024, 7(4), 1086-1094; https://doi.org/10.3390/particles7040066 - 12 Dec 2024

Cited by 2 | Viewed by 1397

Abstract

In the framework of axial symmetric relativistic Hartree–Bogoliubov (RHB) theory and the Skyrme Hartree–Fock–Bogoliubov (HFB) theory, the evolution of shell structure, density distribution, and ground state deformation in superheavy nuclei proximate to

N = 258

are investigated within the relativistic functionals DD-PC1 and [...] Read more.

In the framework of axial symmetric relativistic Hartree–Bogoliubov (RHB) theory and the Skyrme Hartree–Fock–Bogoliubov (HFB) theory, the evolution of shell structure, density distribution, and ground state deformation in superheavy nuclei proximate to

N = 258

are investigated within the relativistic functionals DD-PC1 and DD-ME2, as well as the non-relativistic functional UNEDF0. The results from DD-ME2 and UNEDF0 indicate that

N = 258

is a neutron magic number, whereas DD-PC1 does not anticipate the existence of a bound

N = 258

magic nucleus. Further discussion suggests that the emergence of the magic number

N = 258

is related to the depression of the central density. Full article

(This article belongs to the Special Issue Selected Papers from the “7th Workshop on the Nuclear Mass Table with DRHBc Theory”)

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8 pages, 527 KB

Open AccessArticle

Magic Number N = 350 Predicted by the Deformed Relativistic Hartree-Bogoliubov Theory in Continuum: Z = 136 Isotopes as an Example

by Wei-Jian Liu, Chen-Jun Lv, Peng Guo, Cong Pan, Sibo Wang and Xin-Hui Wu

Particles 2024, 7(4), 1078-1085; https://doi.org/10.3390/particles7040065 - 26 Nov 2024

Cited by 3 | Viewed by 1332

Abstract

The investigation of magic numbers for nuclei in the hyperheavy region

(Z > 120)

is an interesting topic. The neutron magic number

N = 350

is carefully validated by the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), via analysing even-even nuclei [...] Read more.

The investigation of magic numbers for nuclei in the hyperheavy region

(Z > 120)

is an interesting topic. The neutron magic number

N = 350

is carefully validated by the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), via analysing even-even nuclei around

N = 350

of the

Z = 136

isotopes in detail. Nuclei with

Z = 136

and

340 \leq N \leq 360

are all found to be spherical in their ground states. A big drop of the two-neutron separation energy

S_{2 n}

is observed from

N = 350

to

N = 352

in the isotopic chain of

Z = 136

, and a peak of the two-neutron gap

δ_{2 n}

appears at

N = 350

. There exists a big shell gap above

N = 350

around the spherical regions of single-neutron levels for nucleus with

(Z = 136, N = 350)

. These evidences from the DRHBc theory support

N = 350

to be a neutron magic number in the hyperheavy region. Full article

(This article belongs to the Special Issue Selected Papers from the “7th Workshop on the Nuclear Mass Table with DRHBc Theory”)

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16 pages, 3518 KB

Open AccessArticle

Classical and Bohmian Trajectories in Integrable and Nonintegrable Systems

by George Contopoulos and Athanasios C. Tzemos

Particles 2024, 7(4), 1062-1077; https://doi.org/10.3390/particles7040064 - 25 Nov 2024

Cited by 2 | Viewed by 1244

Abstract

In the present paper, we study both classical and quantum Hénon–Heiles systems. In particular, we make a comparison between the classical and quantum trajectories of integrable and nonintegrable Hénon–Heiles Hamiltonians. From a classical standpoint, we study both theoretically and numerically the form of [...] Read more.

In the present paper, we study both classical and quantum Hénon–Heiles systems. In particular, we make a comparison between the classical and quantum trajectories of integrable and nonintegrable Hénon–Heiles Hamiltonians. From a classical standpoint, we study both theoretically and numerically the form of invariant curves in the Poincaré surfaces of section for several values of the coupling parameter in the integrable case and compare them with those in the nonintegrable case. Then, we examine the corresponding Bohmian trajectories, and we find that they are chaotic in both cases, but with chaos emerging at different times. Full article

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24 pages, 9885 KB

Open AccessArticle

General Three-Body Problem in Conformal-Euclidean Space: New Properties of a Low-Dimensional Dynamical System

by Ashot S. Gevorkyan, Aleksander V. Bogdanov and Vladimir V. Mareev

Particles 2024, 7(4), 1038-1061; https://doi.org/10.3390/particles7040063 - 20 Nov 2024

Viewed by 1541

Abstract

Despite the huge number of studies of the three-body problem in physics and mathematics, the study of this problem remains relevant due to both its wide practical application and taking into account its fundamental importance for the theory of dynamical systems. In addition, [...] Read more.

Despite the huge number of studies of the three-body problem in physics and mathematics, the study of this problem remains relevant due to both its wide practical application and taking into account its fundamental importance for the theory of dynamical systems. In addition, one often has to answer the cognitive question: is irreversibility fundamental for the description of the classical world? To answer this question, we considered a reference classical dynamical system, the general three-body problem, formulating it in conformal Euclidean space and rigorously proving its equivalence to the Newtonian three-body problem. It has been proven that a curved configuration space with a local coordinate system reveals new hidden symmetries of the internal motion of a dynamical system, which makes it possible to reduce the problem to a sixth-order system instead of the eighth order. An important consequence of the developed representation is that the chronologizing parameter of the motion of a system of bodies, which we call internal time, differs significantly from ordinary time in its properties. In particular, it more accurately describes the irreversible nature of multichannel scattering in a three-body system and other chaotic properties of a dynamical system. The paper derives an equation describing the evolution of the flow of geodesic trajectories, with the help of which the entropy of the system is constructed. New criteria for assessing the complexity of a low-dimensional dynamical system and the dimension of stochastic fractal structures arising in three-dimensional space are obtained. An effective mathematical algorithm is developed for the numerical simulation of the general three-body problem, which is traditionally a difficult-to-solve system of stiff ordinary differential equations. Full article

(This article belongs to the Special Issue Selected Papers from "The Modern Physics of Compact Stars and Relativistic Gravity 2023")

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21 pages, 571 KB

Open AccessArticle

Hayward–Letelier Black Holes in AdS Spacetime

by Arun Kumar, Ashima Sood, Sushant Ghoshtokumar Ghosh and Aroonkumar Beesham

Particles 2024, 7(4), 1017-1037; https://doi.org/10.3390/particles7040062 - 20 Nov 2024

Cited by 5 | Viewed by 1943

Abstract

We analyze Hayward black holes (BHs) with a negative cosmological constant surrounded by a cloud of strings, which we designate Hayward–Letelier AdS BHs. These solutions can be obtained by coupling the Einstein equations with nonlinear electrodynamics and the energy–momentum tensor of clouds of [...] Read more.

We analyze Hayward black holes (BHs) with a negative cosmological constant surrounded by a cloud of strings, which we designate Hayward–Letelier AdS BHs. These solutions can be obtained by coupling the Einstein equations with nonlinear electrodynamics and the energy–momentum tensor of clouds of strings. We show that these solutions are no longer regular and have a curvature singularity at the center. In turn, we analyze the thermodynamics associated with these BHs by establishing the form of the Smarr formula and the first law of thermodynamics. We derive the expressions for the thermodynamic quantities such as pressure, temperature, heat capacity, Gibbs free energy, and isothermal compressibility. We explore the phase structure of these solutions by analyzing the behavior of the heat capacity and Gibbs free energy. These solutions exhibit a first-order phase transition, similar to van der Waals fluids. We also check the behavior of the thermodynamic quantities near the critical points and calculate the values of the critical exponents. This illustrates a robust analogy between our solutions and van der Waals fluids. Full article

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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13 pages, 320 KB

Open AccessArticle

Structure of the Baryon Halo Around a Supermassive Primordial Black Hole

by Boris Murygin, Viktor Stasenko and Yury Eroshenko

Particles 2024, 7(4), 1004-1016; https://doi.org/10.3390/particles7040061 - 13 Nov 2024

Cited by 1 | Viewed by 1335

Abstract

According to some theoretical models, primordial black holes with masses of more than 10⁸ solar masses could be born in the early universe, and their possible observational manifestations have been investigated in a number of works. Dense dark matter and baryon halos [...] Read more.

According to some theoretical models, primordial black holes with masses of more than 10⁸ solar masses could be born in the early universe, and their possible observational manifestations have been investigated in a number of works. Dense dark matter and baryon halos could form around such primordial black holes even at the pre-galactic stage (in the cosmological Dark Ages epoch). In this paper, the distribution and physical state of the gas in the halo are calculated, taking into account the radiation transfer from the central accreting primordial black hole. This made it possible to find the ionization radius, outside of which there are regions of neutral hydrogen absorption in the 21 cm line. The detection of annular absorption regions at high redshifts in combination with a central bright source may provide evidence of the existence of supermassive primordial black holes. We also point out the fundamental possibility of observing absorption rings with strong gravitational lensing on galaxy clusters, which weakens the requirements for the angular resolution of radio telescopes. Full article

(This article belongs to the Special Issue Selected Papers from XXVIII Workshop “What Comes Beyond the Standard Models?”: New Trends in Particle Cosmology)

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20 pages, 1797 KB

Open AccessArticle

Hyperon Production in Bi + Bi Collisions at the Nuclotron-Based Ion Collider Facility and Angular Dependence of Hyperon Spin Polarization

by Nikita S. Tsegelnik, Vadym Voronyuk and Evgeni E. Kolomeitsev

Particles 2024, 7(4), 984-1003; https://doi.org/10.3390/particles7040060 - 13 Nov 2024

Cited by 3 | Viewed by 1316

Abstract

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of [...] Read more.

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for

\bar{Λ}

,

Ξ

,

\bar{Ξ}

baryons are found to be systematically narrower than for

Λ

s. The

p_{T}

slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to

| y | < 1

increases the slope parameters by 13–30 MeV, depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated, and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated, and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of

Λ

and

Ξ

hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class, 60–70%. We show that, for the considered hyperon polarization mechanism, the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane,

ϕ_{H}

,

cos ϕ_{H} = p_{x} / p_{T}

. For particles with positive longitudinal momentum,

p_{z} > 0

, the polarization increases with

cos ϕ_{H}

, while for particles with

p_{z} < 0

it decreases. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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17 pages, 423 KB

Open AccessArticle

Thermal Conductivity and Thermal Hall Effect in Dense Electron-Ion Plasma

by Arus Harutyunyan and Armen Sedrakian

Particles 2024, 7(4), 967-983; https://doi.org/10.3390/particles7040059 - 11 Nov 2024

Cited by 4 | Viewed by 1283

Abstract

In this study, we examine thermal conductivity and the thermal Hall effect in electron-ion plasmas relevant to hot neutron stars, white dwarfs, and binary neutron star mergers, focusing on densities found in the outer crusts of neutron stars and the interiors of white [...] Read more.

In this study, we examine thermal conductivity and the thermal Hall effect in electron-ion plasmas relevant to hot neutron stars, white dwarfs, and binary neutron star mergers, focusing on densities found in the outer crusts of neutron stars and the interiors of white dwarfs. We consider plasma consisting of single species of ions, which could be either iron

{}^{56}{Fe}

or carbon

{}^{12}C

nuclei. The temperature range explored is from the melting temperature of the solid

T \sim 10^{9}

K up to

10^{11}

K. This covers both degenerate and non-degenerate electron regimes. We find that thermal conductivity increases with density and temperature for which we provide analytical scaling relations valid in different regimes. The impact of magnetic fields on thermal conductivity is also analyzed, showing anisotropy in low-density regions and the presence of the thermal Hall effect characterized by the Righi–Leduc coefficient. The transition froma degenerate to non-degenerate regime is characterized by a minimum ratio of thermal conductivity to temperature, which is analogous to the minimum observed already in the case of electrical conductivity. We provide also formulas fit to our numerical results, which can be used in dissipative magneto-hydrodynamics simulations of warm compact stars. Full article

(This article belongs to the Special Issue Selected Papers from "The Modern Physics of Compact Stars and Relativistic Gravity 2023")

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12 pages, 625 KB

Open AccessArticle

On the Thermomechanics of Hadrons and Their Mass Spectrum

by Leonardo Chiatti

Particles 2024, 7(4), 955-966; https://doi.org/10.3390/particles7040058 - 11 Nov 2024

Viewed by 1184

Abstract

A little-known thermomechanical relation between entropy and action, originally discovered by Boltzmann in the classical domain, was later reconsidered by de Broglie in relation to the wave–particle duality in the free propagation of single particles. In this paper, we present a version adapted [...] Read more.

A little-known thermomechanical relation between entropy and action, originally discovered by Boltzmann in the classical domain, was later reconsidered by de Broglie in relation to the wave–particle duality in the free propagation of single particles. In this paper, we present a version adapted to the phenomenological description of the hadronization process. The substantial difference with respect to the original de Broglie scheme is represented by the universality of the temperature at which the process occurs; this, in fact, coincides with the Hagedorn temperature. The main results are as follows: (1) a clear connection between the universality of the temperature and the existence of a confinement radius of the color forces; (2) a lower bound on the hadronic mass, represented by the universal temperature, in agreement with experimental data; and (3) a scale invariance, which allows the reproduction of the well-known hadronic mass spectrum solution of the statistical bootstrap model. The approach therefore presents a heuristic interest connected to the study of the strong interaction. Full article

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16 pages, 508 KB

Open AccessArticle

A Probe into the Evolution of Primordial Perturbations in the f(T) Gravity Framework with Chaplygin Gas

by Sanjeeda Sultana, Surajit Chattopadhyay and Antonio Pasqua

Particles 2024, 7(4), 939-954; https://doi.org/10.3390/particles7040057 - 31 Oct 2024

Viewed by 1092

Abstract

This work is focused on studying the cosmology of variable modified Chaplygin gas (VMCG) in the framework of exponential and logarithmic

f (T)

theory. The equation of state (EoS) for VMCG in exponential and logarithmic

f (T)

gravity shows [...] Read more.

This work is focused on studying the cosmology of variable modified Chaplygin gas (VMCG) in the framework of exponential and logarithmic

f (T)

theory. The equation of state (EoS) for VMCG in exponential and logarithmic

f (T)

gravity shows quintom behavior. Primordial perturbations were studied for VMCG in both exponential and logarithmic

f (T)

gravity, and it was observed that the potential increases with cosmic time t, and the scalar field decreases toward the minimum value of the potential. The squared speed of sound was positive, meaning that VMCG in both exponential and logarithmic

f (T)

gravity shows stability against small gravitational perturbations. Full article

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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12 pages, 838 KB

Open AccessArticle

Decoding the Gaugino Code Naturally at High-Lumi LHC

by Howard Baer, Vernon Barger and Kairui Zhang

Particles 2024, 7(4), 927-938; https://doi.org/10.3390/particles7040056 - 17 Oct 2024

Cited by 2 | Viewed by 1286

Abstract

Natural supersymmetry with light higgsinos is most favored to emerge from the string landscape, since the volume of a scan parameter space shrinks to tiny volumes for electroweak unnatural models. Rather general arguments favor a landscape selection of soft SUSY breaking terms tilted [...] Read more.

Natural supersymmetry with light higgsinos is most favored to emerge from the string landscape, since the volume of a scan parameter space shrinks to tiny volumes for electroweak unnatural models. Rather general arguments favor a landscape selection of soft SUSY breaking terms tilted to large values, but they are tempered by the atomic principle that the derived value of the weak scale in each pocket universe lies not too far from its measured value in our universe. But, that leaves (at least) three different paradigms for gaugino masses in natural SUSY models: unified (as in nonuniversal Higgs models), anomaly mediation form (as in natural AMSB), and mirage mediation form (with comparable moduli- and anomaly-mediated contributions). We perform landscape scans for each of these, and we show that they populate different, but overlapping, positions in

m (ℓ \bar{ℓ})

and

m (w i n o)

space. The first of these may be directly measurable at high-lumi LHC via the soft opposite-sign dilepton plus jets plus

E /_{T}

signature arising from higgsino pair production, while the second of these could be extracted from direct wino pair production, leading to same-sign diboson production. Full article

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9 pages, 1116 KB

Open AccessArticle

Hurst Exponent and Event-by-Event Fluctuations in Relativistic Nucleus–Nucleus Collisions

by Anastasiya I. Fedosimova, Khusniddin K. Olimov, Igor A. Lebedev, Sayora A. Ibraimova, Ekaterina A. Bondar, Elena A. Dmitriyeva and Ernazar B. Mukanov

Particles 2024, 7(4), 918-926; https://doi.org/10.3390/particles7040055 - 15 Oct 2024

Viewed by 1218

Abstract

A joint study of multi-particle pseudo-rapidity correlations and event-by-event fluctuations in the distributions of secondary particles and fragments of the target nucleus and the projectile nucleus was carried out in order to search for correlated clusters of secondary particles. An analysis of the [...] Read more.

A joint study of multi-particle pseudo-rapidity correlations and event-by-event fluctuations in the distributions of secondary particles and fragments of the target nucleus and the projectile nucleus was carried out in order to search for correlated clusters of secondary particles. An analysis of the collisions of the sulfur nucleus with photoemulsion nuclei at an energy of 200 A·GeV is presented based on experimental data obtained at the SPS at CERN. The analysis of multi-particle correlations was performed using the Hurst method. A detailed analysis of each individual event showed that in events of complete destruction of a projectile nucleus with a high multiplicity of secondary particles, long-distance multi-particle pseudo-rapidity correlations are observed. The distribution of average pseudo-rapidity in such events differs significantly from others, as it is much narrower, and its average value is noticeably shifted towards lower values <η>. Full article

(This article belongs to the Special Issue Feature Papers for Particles 2023)

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19 pages, 1025 KB

Open AccessReview

Some Singular Spacetimes and Their Possible Alternatives

by Andrew DeBenedictis

Particles 2024, 7(4), 899-917; https://doi.org/10.3390/particles7040054 - 14 Oct 2024

Cited by 3 | Viewed by 1716

Abstract

In this review, we begin with a historical survey of some singular solutions in the theory of gravitation, as well as a very brief discussion of how black holes could physically form. Some possible scenarios which could perhaps eliminate these singularities are then [...] Read more.

In this review, we begin with a historical survey of some singular solutions in the theory of gravitation, as well as a very brief discussion of how black holes could physically form. Some possible scenarios which could perhaps eliminate these singularities are then reviewed and discussed. Due to the vastness of the field, its coverage is not exhaustive; instead, the concentration is on a small subset of topics such as possible quantum gravity effects, non-commutative geometry, and gravastars. A simple singularity theorem is also reviewed. Although parts of the manuscript assume some familiarity with relativistic gravitation or differential geometry, the aim is for the broad picture to be accessible to non-specialists of other physical sciences and mathematics. Full article

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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12 pages, 357 KB

Open AccessArticle

Cross-Sections of Neutral-Current Neutrino Scattering on ^94,96Mo Isotopes

by T. S. Kosmas, R. Sahu and V. K. B. Kota

Particles 2024, 7(4), 887-898; https://doi.org/10.3390/particles7040053 - 4 Oct 2024

Viewed by 1988

Abstract

In our recent publications, we presented neutral-current

ν

–nucleus cross-sections for the coherent and incoherent channels for some stable Mo isotopes, assuming a Mo detector medium, within the context of the deformed shell model. In these predictions, however, we have not included the [...] Read more.

In our recent publications, we presented neutral-current

ν

–nucleus cross-sections for the coherent and incoherent channels for some stable Mo isotopes, assuming a Mo detector medium, within the context of the deformed shell model. In these predictions, however, we have not included the contributions in the cross-sections stemming from the stable ^94,96Mo isotopes (abundance of ⁹⁴Mo 9.12% and of ⁹⁶Mo 16.50%). The purpose of the present work is to perform detailed calculations of

ν

–^94,96Mo scattering cross-sections, for a given energy

E_{ν}

of the incoming neutrino, for coherent and incoherent processes. In many situations, the

E_{ν}

values range from 15 to 30 MeV, and in the present work, we used

E_{ν}

= 15 MeV. Mo as a detector material has been employed by the MOON neutrino and double-beta decay experiments and also from the NEMO neutrinoless double-beta decay experiment. For our cross-section calculations, we utilize the Donnelly–Walecka multipole decomposition method in which the

ν

–nucleus cross-sections are given as a function of the excitation energy of the target nucleus. Because only the coherent cross-section is measured by current experiments, it is worth estimating what portion of the total cross-section represents the measured coherent rate. This requires the knowledge of the incoherent cross-section, which is also calculated in the present work. Full article

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8 pages, 285 KB

Open AccessArticle

Implications of the Spin-Induced Accretion Disk Truncation on the X-ray Binary Broadband Emission

by Theodora Papavasileiou, Odysseas Kosmas and Theocharis Kosmas

Particles 2024, 7(4), 879-886; https://doi.org/10.3390/particles7040052 - 1 Oct 2024

Viewed by 1359

Abstract

Black hole X-ray binary systems consist of a black hole accreting mass from its binary companion, forming an accretion disk. As a result, twin relativistic plasma ejections (jets) are launched towards opposite and perpendicular directions. Moreover, multiple broadband emission observations from X-ray binary [...] Read more.

Black hole X-ray binary systems consist of a black hole accreting mass from its binary companion, forming an accretion disk. As a result, twin relativistic plasma ejections (jets) are launched towards opposite and perpendicular directions. Moreover, multiple broadband emission observations from X-ray binary systems range from radio to high-energy gamma rays. The emission mechanisms exhibit thermal origins from the disk, stellar companion, and non-thermal jet-related components (i.e., synchrotron emission, inverse comptonization of less energetic photons, etc.). In many attempts at fitting the emitted spectra, a static black hole is often assumed regarding the accretion disk modeling, ignoring the Kerr metric properties that significantly impact the geometry around the usually rotating black hole. In this work, we study the possible implications of the spin inclusion in predictions of the X-ray binary spectrum. We mainly focus on the most significant aspect inserted by the Kerr geometry, the innermost stable circular orbit radius dictating the disk’s inner boundary. The outcome suggests a higher-peaked and hardened X-ray spectrum from the accretion disk and a substantial increase in the inverse Compton component of disk-originated photons. Jet-photon absorption is also heavily affected at higher energy regimes dominated by hadron-induced emission mechanisms. Nevertheless, a complete investigation requires the full examination of the spin contribution and the resulting relativistic effects beyond the disk truncation. Full article

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