The concept of complexity related to the celestial systems is elaborated within the context of distinct revised gravity theories. However, its interpretation in $\textit{f}$($\textit{R}$, $\textit{G}$) gravity is the main idea of our manuscript. We assume that the inner configuration of the system is a cylindrically symmetric geometry comprising the anisotropic configuration of matter. In our case study, we determine the revised equations of motion combined with the orthogonal decomposition of the Riemann tensor. The implications of anisotropic pressure and nonhomogeneous energy density are relevant. Decisive results relating to the Tolman mass, Weyl scalar, and the complexity factor are derived by incorporating dark source terms corresponding to the $\textit{f}$($\textit{R}$, $\textit{G}$) theory. Additionally, the structure scalars calculated in our manuscript are employed to derive the expression for the complexity factor, after considering reducing the complexity constraint to obtain the solutions for the specific models. The compact structures with anisotropic pressure and non-homogeneous energy density claim the maximum complexity. However, these fluids might not demonstrate any complexity if the implications of non-homogeneous energy density and anisotropic pressure are eradicated because of dark source terms corresponding to the $\textit{f}$($\textit{R}$, $\textit{G}$) theory.

Pakistan

A. Rehman

Azerbaijan

M. Yousaf

China

Faisal Javed

Thailand

Phongpichit Channuie

Interpretation of complexity associated with cylindrically symmetric configuration in $\textit{f}$($\textit{R}$, $\textit{G}$) theory

We show that gravitational leptogenesis with dynamical <italic>CPT</italic> breaking in an expanding universe can be reconciled with the exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity model, which introduces only one additional parameter <italic>&#946;</italic> compared to the standard &#923;CDM cosmology. This model incorporated axions as cold dark matter. For <italic>L</italic> violating interactions, we consider both a non-supersymmetric model with heavy right-handed neutrino decay and a supersymmetric model with sneutrino decay. For both cases, we have shown that the required baryonic asymmetry could be obtained. We have also shown the variation of decoupling temperature for lepton number violating interactions with the <italic>&#946;</italic> parameter in exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity. Lepton number-violating model parameters are constrained with the <italic>&#946;</italic> through the decoupling temperature. An upper bound on the <italic>&#946;</italic> parameter of the exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity is also obtained.

India

Suhail Khan

Ajay Bassi

Rathin Adhikari

Leptogenesis in exponential <italic>f</italic>( <italic>R</italic>) gravity model

The branching fractions of the axial vector meson decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><msub><mi>a</mi><mn>0</mn></msub><mi>π</mi><mo>,</mo><mi>π</mi><mi>π</mi><mi>η</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><mi>ρ</mi><mi>π</mi><mo>,</mo><mi>π</mi><mi>π</mi><mi>π</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><mi>K</mi><mi>K</mi><mi>π</mi></math> are calculated in the standard <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo><mo>×</mo><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></math> quark Nambu–Jona-Lasinio model. The intermediate channels with the states <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo><mi>π</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>500</mn><mo stretchy="false">)</mo><mi>η</mi></math> are taken into account in the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><mi>π</mi><mi>π</mi><mi>η</mi></math>. In the case of the scalar mesons, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover><mi>q</mi></math> representation as a chiral symmetric partners of the pseudoscalar mesons is used. It is shown that the decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><mi>ρ</mi><mi>π</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">→</mo><mn>3</mn><mi>π</mi></math> occur due to the mass difference of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>u</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi></math> quarks. All the results are obtained without using any additional arbitrary parameters and are in satisfactory agreement with the known experimental data.

JINR

M.K. Volkov

A.A. Pivovarov

Kazakhstan

K. Nurlan

Decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><msub><mrow><mi>f</mi></mrow><mrow><mn>1</mn></mrow></msub><mo stretchy="false">→</mo><msub><mrow><mi>a</mi></mrow><mrow><mn>0</mn></mrow></msub><mi>π</mi><mo>,</mo><mi>π</mi><mi>π</mi><mi>π</mi></mrow><mo stretchy="false">(</mo><mi>η</mi><mo stretchy="false">)</mo></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>f</mi></mrow><mn>1</mn></msub><mo stretchy="false">→</mo><mi>K</mi><mi>K</mi><mi>π</mi></mrow></math> in the chiral <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo><mo>×</mo><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></mrow></math> quark NJL model

We examine the structure scalars constructed from the orthogonal splitting of the Riemann tensor for the spacetime metric describing the interior of a charged matter configuration undergoing dissipative collapse in the framework of <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity (where <math altimg='si2.svg'><mi>R</mi></math> and <math altimg='si3.svg'><mi>T</mi></math> are the Ricci scalar and the trace of energy-momentum tensor, respectively), and also the way these quantities influence the various physical parameters of the collapsing matter. In absence of dissipation, the energy density inhomogeneity is found to be influenced by the structure scalar <math altimg='si4.svg'><msub><mi>X</mi><mrow><mi>T</mi><mi>F</mi></mrow></msub></math> and the mass-function of the collapsing matter. Further, the presence of charge affects the structure scalars and the total mass-energy content. The dependence of the various physical parameters like heat dissipation, energy density inhomogeneity, evolution of the expansion scalar, the shear scalar, effective homogeneous energy density, and pressure anisotropy on the structure scalars, have been clearly indicated along with a discussion on the complexity factor of the collapsing configuration. The <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> junction conditions have been presented, showing the matching conditions for the matter Lagrangian and their derivatives at the boundary. The energy conditions are also presented and the possibility of violation of the Strong Energy Condition has been discussed.

Uttaran Ghosh

Sarbari Guha

Structure scalars for charged dissipative spherical collapse in <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity

Germany

Ipsita Mandal

Corrigendum: Stable non-Fermi liquid fixed point at the onset of incommensurate 2 <italic>k</italic> <inf><italic>F</italic></inf> charge density wave order [Nucl. Phys. B 1005 (2024) 116586]

A partial-wave analysis is performed on the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></math> within the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math> invariant-mass region below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.6</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>/</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>, using <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mn>10.09</mn><mo>±</mo><mn>0.04</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>9</mn></mrow></msup></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> events collected with the BESIII detector. Significant isospin-violating decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi><mo stretchy="false">(</mo><mn>1405</mn><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1420</mn><mo stretchy="false">)</mo></math> into <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo><msup><mi>π</mi><mn>0</mn></msup></math> are observed. For the first time, three axial vectors, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1285</mn><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1420</mn><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1510</mn><mo stretchy="false">)</mo></math>, are observed to decay into <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math>. The product branching fractions of these resonances are reported.

M. Ablikim

Russia

M.N. Achasov

Sweden

P. Adlarson

O. Afedulidis

X.C. Ai

R. Aliberti

Italy

A. Amoroso

Q. An

Y. Bai

O. Bakina

I. Balossino

Y. Ban

H.R. Bao

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

United States

R.A. Briere

A. Brueggemann

H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

G.R. Che

Y.Z. Che

G. Chelkov

C. Chen

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.L. Chen

S.M. Chen

T. Chen

X.R. Chen

X.T. Chen

Y.B. Chen

Y.Q. Chen

Z.J. Chen

South Korea

S.K. Choi

G. Cibinetto

F. Cossio

J.J. Cui

H.L. Dai

J.P. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denysenko

M. Destefanis

F. De Mori

B. Ding

X.X. Ding

Y. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

M.C. Du

S.X. Du

Y.Y. Duan

Z.H. Duan

P. Egorov

G.F. Fan

J.J. Fan

Y.H. Fan

J. Fang

S.S. Fang

W.X. Fang

Y.Q. Fang

R. Farinelli

L. Fava

F. Feldbauer

G. Felici

C.Q. Feng

J.H. Feng

Y.T. Feng

M. Fritsch

C.D. Fu

J.L. Fu

Y.W. Fu

H. Gao

Study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>f</mi></mrow><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1420</mn><mo stretchy="false">)</mo></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi><mo stretchy="false">(</mo><mn>1405</mn><mo stretchy="false">)</mo></math> in the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msup><mrow><mi>π</mi></mrow><mn>0</mn></msup><msup><mrow><mi>π</mi></mrow><mn>0</mn></msup><msup><mrow><mi>π</mi></mrow><mn>0</mn></msup></mrow></math>

We determine the low-energy constants <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>0</mn></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi>L</mi></mrow><mrow><mn>4</mn></mrow><mrow><mi>r</mi></mrow></msubsup></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>L</mi><mn>5</mn><mi>r</mi></msubsup></math> of SU(3) chiral perturbation theory from a lattice QCD calculation of the scalar form factors of the pion with fully controlled systematics. Lattice results are computed on a large set of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>N</mi></mrow><mrow><mi>f</mi></mrow></msub><mo>=</mo><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math> gauge ensembles covering four lattice spacings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>a</mi><mo>∈</mo><mo stretchy="false">[</mo><mn>0.049</mn><mo>,</mo><mn>0.086</mn><mo stretchy="false">]</mo><mtext> </mtext><mtext> </mtext><mi>fm</mi></mrow></math>, pion masses <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>π</mi></mrow></msub><mo>∈</mo><mo stretchy="false">[</mo><mn>130</mn><mo>,</mo><mn>350</mn><mo stretchy="false">]</mo><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math>, and various large physical volumes. By determining the notorious quark-disconnected contributions with unprecedented precision and using a large range of source-sink separations <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>t</mi></mrow><mrow><mi>sep</mi></mrow></msub><mo>∈</mo><mo stretchy="false">[</mo><mn>1.0</mn><mo>,</mo><mn>3.25</mn><mo stretchy="false">]</mo><mtext> </mtext><mtext> </mtext><mi>fm</mi></mrow></math>, we are able for the first time to obtain the scalar radii from a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>z</mi></math>-expansion parametrization of the form factors rather than a simple linear approximation at small momentum transfer. The low-energy constants are obtained from the physical extrapolation of the radii using next-to-leading-order SU(3) next-to-leading-order chiral perturbation theory to parametrize the quark mass dependence. Systematic uncertainties are estimated via model averages based on the Akaike information criterion. Our determination of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi>L</mi></mrow><mrow><mn>4</mn></mrow><mrow><mi>r</mi></mrow></msubsup></mrow></math> is the first lattice determination to obtain a result not compatible with zero.

Georg von Hippel

Konstantin Ottnad

Low-Energy Constants of Chiral Perturbation Theory from Pion Scalar Form Factors in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>N</mi></mrow><mrow><mi>f</mi></mrow></msub><mo>=</mo><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math>-Flavor Lattice QCD with Controlled Errors

This study explores baryogenesis within a modified gravitational framework where the action incorporates a non-local kernel dependent on the Ricci scalar <italic>R</italic> and its covariant derivative &#8711; <italic>R</italic>. This extension, referred to as <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi mathvariant='normal'>&#8711;</mi><mi>R</mi><mo stretchy='false'>)</mo></math> gravity, generalizes traditional <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> theories by introducing additional derivative terms that may influence early-universe dynamics. Within this framework, we examine four distinct forms of the cosmological scale factor: (i) an intermediate scaling solution, (ii) a conventional power-law expansion, (iii) a generalized hybrid evolution combining both power-law and exponential growth terms and (iv) logamediate scale factor. We introduce a charge-parity (CP) violating interaction term that scales linearly with the spacetime derivative of the combined Ricci scalar and its covariant derivative, expressed as <math altimg='si3.svg'><msub><mrow><mo>&#8706;</mo></mrow><mrow><mi>&#956;</mi></mrow></msub><mo stretchy='false'>(</mo><mi>R</mi><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mi mathvariant='normal'>&#8711;</mi><mi>R</mi><mo stretchy='false'>)</mo></math>. Through numerical computation, we determine the resulting baryon asymmetry by evaluating the dimensionless ratio <math altimg='si4.svg'><mfrac><mrow><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow><mrow><mi>s</mi></mrow></mfrac></math>, where <math altimg='si5.svg'><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>B</mi></mrow></msub></math> represents the baryon number density and <italic>s</italic> denotes the entropy density of the universe. We quantitatively compare our theoretical predictions for the baryon-to-entropy ratio, <math altimg='si4.svg'><mfrac><mrow><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow><mrow><mi>s</mi></mrow></mfrac></math>, with the current observational constraint of <math altimg='si6.svg'><mn>9.42</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>11</mn></mrow></msup></math>. Notably, our numerical results demonstrate remarkable agreement with this empirically established value, supporting the viability of our modified gravitational framework in explaining the observed baryon asymmetry of the universe.

Saudi Arabia

Abdulmohsen Daham Alruwaili

Nadeem Azhar

Abdul Jawad

Investigating baryon to entropy ratio phenomenon in <italic>f</italic>( <italic>R</italic>,&#8711; <italic>R</italic>) gravity

This study explores the structure of compact stars using an extended theory of gravity known as <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi><mo stretchy='false'>)</mo></math> gravity, where <math altimg='si3.svg'><mi mathvariant='script'>R</mi></math>, is the Ricci scalar, <math altimg='si4.svg'><mi mathvariant='script'>G</mi></math>, the Gauss-Bonnet invariant, and <math altimg='si5.svg'><mi mathvariant='script'>T</mi></math> the trace of the energy-momentum tensor. Focusing on massive radio pulsars, specifically neutron stars with masses greater than 1.8 solar masses, utilize these extreme astrophysical environments to test gravity in regimes unreachable by Earth-based experiments. We adopt a linear form of the theory, <math altimg='si18.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi mathvariant='script'>R</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#945;</mi><mi mathvariant='script'>G</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#946;</mi><mi mathvariant='script'>T</mi></math>, with <italic>&#945;</italic>, <cross-ref refid='fn0010' id='crf0390'>1</cross-ref> and <italic>&#946;</italic> are dimensional constants, and derive an exact analytical solution for anisotropic perfect fluid spheres in hydrostatic equilibrium. This model incorporates the compactness factor <math altimg='si7.svg'><mi>C</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mn>2</mn><mi>G</mi><mi>M</mi></mrow><mrow><mi>R</mi><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math>, to describe all physical properties within the stellar interior. To constrain the model, we employ observational data from the pulsar <italic>U</italic>1724, using its mass and radius to fix the parameters at their upper bounds: <math altimg='si8.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#945;</mi></mrow><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.023</mn></math> and <math altimg='si9.svg'><msub><mrow><mi>&#946;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#946;</mi></mrow><mrow><msup><mrow><mi>&#954;</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.001</mn></math>. The resulting model is consistent with physical viability and observational constraints. Notably, the squared sound speed in this framework remains below the theoretical limit ( <math altimg='si10.svg'><mmultiscripts><mrow><mtext mathvariant='normal'>c</mtext></mrow><mrow><mi>s</mi></mrow><none /><none /><mrow><mn>2</mn></mrow></mmultiscripts><mo linebreak='goodbreak' linebreakstyle='after'>&lt;</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy='false'>/</mo><mn>3</mn></math>), contrasting with general relativity results. Without assuming a specific equation of state, the model exhibits linear behavior and predicts a core density several times higher than nuclear saturation density ( <math altimg='si11.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mtext>nuc</mtext></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>2.6</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></math> g/cm 3), with surface density <math altimg='si12.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mi>s</mi></mrow></msub></math>, also exceeding this threshold. Additionally, the derived mass-radius relation agrees well with existing astrophysical observations.

Egypt

South Africa

G.G.L. Nashed

Constraining linear form of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo></math> gravity from astrophysical observations of the Pulsar U1724

In this paper, we investigate Friedmann Robertson Walker (FRW) space time filled with a perfect fluid in <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub><mo stretchy='false'>)</mo></math> modified theory framework formulated by Harko and Lobo (2010), where <italic>R</italic> is the Ricci scalar curvature, <math altimg='si2.svg'><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub></math> is the ideal fluid's Lagrangian. Two specific non-linear <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub><mo stretchy='false'>)</mo></math> functional forms are assumed: <math altimg='si3.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mo stretchy='false'>(</mo><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mi>&#945;</mi><mi>R</mi><mo stretchy='false'>)</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub></math> representing a non-minimal coupling case and <math altimg='si4.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><msubsup><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow><mrow><mi>n</mi></mrow></msubsup><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#946;</mi></math> representing a minimal coupling case. Here, we use a cubic parametrization of the deceleration parameter that produces an accelerating universe to obtain the exact solution for the field equations. We investigate the evolution of cosmological parameters including pressure and energy density. Using <math altimg='si5.svg'><msub><mrow><mi>L</mi></mrow><mrow><mi>m</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi>&#961;</mi></math> and a cubic parametrization of the deceleration parameter to account for late-time cosmic acceleration. We analyze the evolution of cosmological parameters in terms of both cosmic time and redshift and constrain model parameters using observational datasets from <math altimg='si6.svg'><mi>H</mi><mo stretchy='false'>(</mo><mi>z</mi><mo stretchy='false'>)</mo></math>, Pantheon, BAO, H(z)+Pantheon, H(z)+BAO+Pantheon. The results show a transition of the deceleration parameter from deceleration to acceleration and indicate a possible quintessence-like behavior at the present epoch. The findings suggest that the proposed models can effectively describe the universe's expansion history in agreement with observations.

Kangujam Priyokumar Singh

Syed Sabanam

Anil Kumar Yadav

Asem Jotin Meitei

Modeling through the cubic parametrization of the deceleration parameter in <italic>f</italic>( <italic>R</italic>, <italic>Lm</italic>) gravity with observational constraints