The dependence of $$\textrm{f}_{0}$$ (980) production on the final-state charged-particle multiplicity is reported for proton–proton (pp) collisions at the centre-of-mass energy, $$\sqrt{s}=$$ 13 TeV. The production of $$\textrm{f}_{0}$$ (980) is measured with the ALICE detector via the $$\textrm{f}_0 (980) \rightarrow \pi ^{+}\pi ^{-}$$ decay channel in a midrapidity region of $$|y|<$$ 0.5. The evolution of the integrated yields and mean transverse momentum of f $$_{0}$$ (980) as a function of charged-particle multiplicity measured in pp at $$\sqrt{s}=$$ 13 TeV follows the trends observed in pp at $$\sqrt{s}=$$ 5.02 TeV and in proton–lead (p–Pb) collisions at $$\sqrt{s_{\textrm{NN}}}=$$ 5.02 TeV. Particle yield ratios of $$\textrm{f}_{0}$$ (980) to $$\pi ^{\pm }$$ and $$\textrm{K}^{*}$$ (892) $$^{0}$$ are found to decrease with increasing charged-particle multiplicity. These particle ratios are compared with calculations from the canonical statistical thermal model as a function of charged-particle multiplicity. The thermal model calculations provide a better description of the decreasing trend of particle ratios when no strange or antistrange quark composition for f $$_{0}$$ (980) is assumed, which suggests that the data do not support significant hidden strangeness in the $$\textrm{f}_{0} (980)$$ .

United States

I. Abualrob

Italy

S. Acharya

Switzerland

G. Aglieri Rinella

L. Aglietta

M. Agnello

N. Agrawal

India

Z. Ahammed

S. Ahmad

Slovakia

I. Ahuja

Indonesia

ZUL. Akbar

A. Akindinov

Germany

V. Akishina

M. Al-Turany

D. Aleksandrov

B. Alessandro

China

H. Alfanda

Mexico

R. Alfaro Molina

B. Ali

A. Alici

South Korea

A. Alkin

Norway

J. Alme

G. Alocco

T. Alt

A. Altamura

I. Altsybeev

Romania

C. Andrei

United Kingdom

N. Andreou

A. Andronic

E. Andronov

V. Anguelov

F. Antinori

P. Antonioli

N. Apadula

H. Appelshäuser

France

C. Arata

S. Arcelli

R. Arnaldi

Brazil

J. Arneiro

I. Arsene

M. Arslandok

A. Augustinus

R. Averbeck

M. Azmi

Japan

H. Baba

A. Babu

A. Badalà

J. Bae

Y. Bae

Y. Baek

X. Bai

R. Bailhache

Y. Bailung

R. Bala

A. Baldisseri

Poland

B. Balis

S. Bangalia

Z. Banoo

V. Barbasova

F. Barile

L. Barioglio

Greece

M. Barlou

B. Barman

Hungary

G. Barnaföldi

L. Barnby

E. Barreau

V. Barret

L. Barreto

K. Barth

E. Bartsch

N. Bastid

G. Batigne

D. Battistini

B. Batyunya

D. Bauri

Peru

J. Bazo Alba

Denmark

I. Bearden

P. Becht

D. Behera

S. Behera

I. Belikov

V. Bella

F. Bellini

R. Bellwied

L. Beltran

Y. Beltran

G. Bencedi

A. Bensaoula

S. Beole

Y. Berdnikov

A. Berdnikova

L. Bergmann

L. Bernardinis

L. Betev

P. Bhaduri

T. Bhalla

A. Bhasin

B. Bhattacharjee

S. Bhattarai

L. Bianchi

Czechia

J. Bielčík

Multiplicity dependence of f $$_{\textbf{0}}$$ (980) production in pp collisions at $$\mathbf {\sqrt{s}}=$$ 13 TeV

This paper studies the impact of bulk viscosity on the feasibility of the cosmological bounce solutions in the framework of $\textit{F}$($\textit{R}$) theory. In this perspective, the behavior of an isotropic homogeneous universe with a perfect matter configuration and new formulation of the bulk viscosity coefficient is explored. We select a specific mathematical form of the modified gravity model to see how it affects the dynamics of cosmic evolution. In addition, we analyze various cosmological parameters, exploring the presence of feasible cosmological bounce solutions. A physically acceptable bouncing scenario occurs when the energy density stays positive, pressure becomes negative, and the violation of null and strong energy conditions highlight the important role of bulk viscosity. We also study the cosmographic parameters and their paths in the $$r-s$$ diagnostic framework. Finally, a thermodynamic investigation is carried out to test the generalized second law of thermodynamics and the overall stability of the cosmological model. The results show that $\textit{F}$($\textit{R}$) gravity is a realistic and promising alternative to the standard cosmological model, giving deeper understanding of gravitational dynamics and the early evolution of cosmos.

Pakistan

Azerbaijan

M. Sharif

Saudi Arabia

Eman Moneer

Nusrat Fatima

Russia

Euaggelos Zotos

Cosmic evolution beyond the singularity: a study of viscous bounce dynamics in $\textit{F}$($\textit{R}$) theory

We investigate a bouncing cosmological model within the Weyl-type <italic>f</italic>( <italic>Q</italic>) gravity framework, employing a power-law form of the non-metricity scalar <italic>Q</italic>. The model successfully resolves the initial singularity problem by demonstrating a nonsingular bounce, where the universe transitions from a contracting phase <math altimg='si18.svg'><mrow><mover accent='true'><mi>a</mi><mo>&#729;</mo></mover><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>&lt;</mo><mn>0</mn></mrow></math> to an expanding phase ( <math altimg='si19.svg'><mrow><mover accent='true'><mi>a</mi><mo>&#729;</mo></mover><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>&gt;</mo><mn>0</mn></mrow></math>) at the bouncing point <italic>t</italic>&#8239;&#8776;&#8239;0. Key features include the violation of the null energy condition (NEC) near the bounce and the crossing of the phantom divide line ( <math altimg='si20.svg'><mrow><mi>&#969;</mi><mo linebreak='goodbreak'>=</mo><mo>&#8722;</mo><mn>1</mn></mrow></math>) by the equation of state (EoS) parameter, indicating quintom-like behavior. The model exhibits accelerated expansion post-bounce, suggesting an inflationary phase. Stability analysis via the adiabatic index reveals instability near the bouncing point, while energy conditions highlight the dominance of dark energy. Additionally, the study explores scalar fields, showing that quintessence-like kinetic energy becomes negative and phantom-like kinetic energy peaks positively near the bounce, aligning with dark energy dynamics. The Hubble parameter, deceleration parameter, and Hubble radius further validate the bouncing scenario, with the latter displaying symmetric behaviour around the bounce. These results underscore the viability of Weyl-type <italic>f</italic>( <italic>Q</italic>) gravity as a framework for nonsingular bouncing cosmologies, offering insights into early universe dynamics and dark energy behaviour.

Rita Rani

G.K. Goswami

J.K. Singh

South Africa

Sushant G. Ghosh

Sunil D. Maharaj

Scale-invariant bounce cosmology in Weyl <italic>f</italic>( <italic>Q</italic>) gravity with quintom signature

In this manuscript, we explore two static and spherically symmetric, anisotropic, charged stars employing the formalism of modified <italic>f</italic>( <italic>R, T</italic>) gravity, where the gravitational Lagrangian is taken as <math altimg='si17.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo><mo>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mn>2</mn><mi>&#947;</mi><mi>T</mi></mrow></math>. By introducing a core-envelope structure, we bring a new dimension to stellar modeling in modified gravity. Where the core follows a polytropic equation of state (EoS) and the envelope is modeled linearly. The internal spacetime continuously matched to the exterior Reissner&#8211;Nordstr <math altimg='si18.svg'><mover accent='true'><mi>o</mi><mo>&#168;</mo></mover></math>m spacetime at the surface. We incorporate the effects of matter-geometry coupling by analyzing the physical quantities for three values of the coupling constant <italic>&#947;</italic>, offering new insights into how such coupling (associated with dark matter effects) influence stellar behavior. To validate the physical acceptability of the model, we examine key physical parameters and stability criteria, including density, pressure profiles, energy conditions, causality constraints, and the modified Tolman&#8211;Oppenheimer&#8211;Volkoff (TOV) equation. The stability of the model is further evaluated by the adiabatic index for astrophysical objects <math altimg='si9.svg'><mrow><mi>S</mi><mi>A</mi><mi>X</mi><mspace width='0.33em' /><mi>J</mi><mn>1808.4</mn><mo linebreak='goodbreak'>&#8722;</mo><mn>3658</mn></mrow></math>, <math altimg='si10.svg'><mrow><mn>4</mn><mi>U</mi><mspace width='0.33em' /><mn>1608</mn><mo linebreak='goodbreak'>&#8722;</mo><mn>52</mn></mrow></math>. Our results demonstrate that the proposed model is physically free from singularity, and sensitive to the matter-geometry coupling. The significance of <italic>f</italic>( <italic>R, T</italic>) gravity in star&#8217;s modeling is highlighting with possible dark matter effects.

A. Khalid

A. Zahra

Jordan

Muhammad Bilal Riaz

S.A. Mardan

Rubab Manzoor

Analysis of charged compact stars by core-envelope model in <italic>f</italic>( <italic>R, T</italic>) gravity

We construct the Hamiltonian formulation of the isotropic Universe in a generic metric $\textit{f}$($\textit{R}$)-theory in the Jordan frame. We canonically quantize the Universe volume via a polymer formulation, and we adopt the scalar field naturally arising from this scenario as a physical clock. Being within the limit of cut-off values of the space volume, we are legitimized to neglect, at first approximation level, the self-interacting potential term associated with the scalar field. We first study the semi-classical polymer dynamics, outlining the emergence of a bouncing cosmology, both in the internal as well as in the synchronous time. In this latter time variable, we are also able to compare the obtained picture with that of a standard polymer Big-Bounce. We see that in the studied case, the collapsing and expanding branches are no longer symmetric with respect to the minimum volume configuration. Then, we fully quantize the system dynamics in the momentum representation, constructing a suitable dynamical Hilbert space and setting up the dynamics of localized wave packets. The mean value dynamics, both for the momentum and volume spaces, is characterized by a bouncing dynamics as described via the internal time, which closely resembles that one obtained in Loop Quantum Cosmology and Polymerization, respectively.

Maria Limongi

Simone Lo Franco

Giovanni Montani

Sebastiano Segreto

Big-bounce in quantum f(R)-cosmology: polymer dynamics with internal time

We demonstrate that the scalaron, a scalar degree of freedom, emerging from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>f</mi><mo stretchy="false">(</mo><mi>R</mi><mo stretchy="false">)</mo></math> theory of gravity, can account for the observed dark matter (DM) abundance if its mass is around the MeV scale, to ensure its cosmological stability. Focusing on two well-known <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>f</mi><mo stretchy="false">(</mo><mi>R</mi><mo stretchy="false">)</mo></math> gravity models, we systematically show that if scalaron production proceeds via the freeze-in mechanism, the right relic abundance is satisfied over a very narrow window of reheating temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>14</mn></msup><mo>≲</mo><msub><mi>T</mi><mrow><mi>rh</mi></mrow></msub><mo>≲</mo><msup><mn>10</mn><mn>16</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. We delineate the viable parameter space of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>f</mi><mo stretchy="false">(</mo><mi>R</mi><mo stretchy="false">)</mo></math> models consistent with the observed DM abundance, and highlight relevant experimental constraints from searches targeting DM decay signatures.

Basabendu Barman

Ashmita Das

Rakesh Kumar SivaKumar

Rudra Pratap Udgata

Freeze-in production of scalaron dark matter in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>f</mi><mo stretchy="false">(</mo><mi>R</mi><mo stretchy="false">)</mo></mrow></math> gravity

In this paper, we intend to explore Conformal Vector Fields (CVFs) of the Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model within the setup of <italic>f</italic>( <italic>Q, T</italic>) gravity, where <italic>Q</italic> denotes the non-metricity scalar and <italic>T</italic> is the trace of stress energy tensor. We start with a linear form of <italic>f</italic>( <italic>Q, T</italic>) gravity to solve equations of motion in the background of a type I LRS Bianchi cosmological model. We then follow a general form of the function <italic>f</italic>( <italic>Q, T</italic>) along with some additional constraints to explore exact space-times. With the help of such general form, we construct four types of non-trivial <italic>f</italic>( <italic>Q, T</italic>) gravity models. These models are in square root form, power law form, an exponential as well as a logarithmic form. Applying these <italic>f</italic>( <italic>Q, T</italic>) gravity models, we explore a variety of cosmological solutions admitting rotational symmetry. For these cosmological solutions, we find the CVFs. We observe that the constructed LRS Bianchi type-I solutions admit CVFs of dimension four, five, six, or fifteen. The physical entities like energy density and pressure associated with each Bianchi cosmological model are also being discussed.

Muhammad Qasim

Asifa Ashraf

Muhammad Ramzan

Shabeela Malik

Shahid Iqbal

Fiaz Hussain

Perfect fluid Bianchi cosmological model admitting conformal motions in <italic>f</italic>( <italic>Q, T</italic>) gravity

In this work, we derive a new class of analytic black hole solutions within the framework of <math altimg='si8.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity, where the black hole is surrounded by an anisotropic fluid acting as the matter source. We consider both linear and nonlinear forms of the function <math altimg='si8.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math>, enabling a detailed exploration of how anisotropic pressures and different <math altimg='si8.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> influence the spacetime structure. Furthermore, we derive the conditions on the coupling parameters ( <italic>&#946;</italic> <inf>1</inf>, <italic>&#946;</italic> <inf>2</inf>, <italic>&#946;</italic> <inf>3</inf>) under which the energy condition is satisfied. Utilising these constraints, we then investigate the thermodynamic behaviour of the resulting black hole solutions in the presence of various matter fields. An important outcome of this study is that the results obtained deviate from those predicted by standard General Relativity. It is also observed that these deviations depend explicitly on the interaction between the matter Lagrangian <math altimg='si9.svg'><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub></math> and the trace <italic>T</italic> of the energy-momentum tensor.

Aniruddha Ghosh

Ujjal Debnath

The new black hole solution with anisotropic fluid in <math altimg='si8.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity: Thermodynamics

We investigate exact charged and uncharged black hole solutions in a (2+1)-dimensional spacetime within the framework of quadratic form of <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> symmetric teleparallel gravity, where <math altimg='si15.svg'><mi mathvariant='double-struck'>Q</mi></math> is the non-metricity scalar. By adopting spherical symmetry and considering both vanishing and non-vanishing electromagnetic fields, we derive new classes of black hole solutions and analyze their geometric and physical properties. The study demonstrates that the inclusion of quadratic corrections in the gravitational Lagrangian significantly modifies the structure of solutions, producing deviations from the standard BTZ geometry. Invariants such as curvature and non-metricity scalars are calculated to classify the singularity structure and spacetime behavior. Thermodynamic quantities, including Hawking temperature, entropy, and heat capacity, are computed, showing consistency with the first law of black hole thermodynamics. Furthermore, we examine the geodesic motion of test particles and derive the effective potential to explore the stability of photon orbits. A notable outcome is the identification of weaker black hole singularities in comparison to General Relativity, attributed to the non-metricity corrections. The possibility of multi-horizon configurations is also explored. This study provides a comprehensive analysis of the gravitational, thermodynamic, and dynamical features of lower-dimensional black holes in <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> gravity and highlights their distinct characteristics with respect to General Relativity.

Egypt

Gamal G.L. Nashed

Salvatore Capozziello

Stable black holes in lower dimensional <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> non-metric gravity

The observed matter–antimatter asymmetry of the Universe remains a fundamental challenge in modern physics. In this work, we explore gravitational baryogenesis within the framework of <italic>f</italic>( <italic>T, L<inf>m</inf></italic>) gravity, where the gravitational Lagrangian depends on both the torsion scalar <italic>T</italic> and the matter Lagrangian <italic>L<inf>m</inf></italic>. We consider three representative models and examine their ability to generate the observed baryon-to-entropy ratio. Our analysis shows that couplings involving both torsion and the matter Lagrangian, <math altimg='si35.svg'><mrow><msub><mi>&#8706;</mi><mi>&#956;</mi></msub><mrow><mo>(</mo><mo>&#8722;</mo><mi>T</mi><mo linebreak='badbreak'>&#8722;</mo><mfrac><msub><mi>L</mi><mi>m</mi></msub><msub><mi>L</mi><mn>0</mn></msub></mfrac><mo>)</mo></mrow></mrow></math>, can successfully account for the baryon asymmetry for decoupling temperatures in the range 10 12&#8211;10 14&#8201;GeV, while remaining consistent with small deviations from General Relativity. These results highlight the capacity of <italic>f</italic>( <italic>T, L<inf>m</inf></italic>) gravity to provide novel mechanisms for baryogenesis, demonstrating that the interplay between torsion and matter-sector contributions can naturally generate the observed asymmetry. The framework also remains compatible with late-time cosmological evolution, offering a unified setting for early- and late-time dynamics.

Portugal

Daniel F P Cruz

David S. Pereira

Francisco S N Lobo

Gravitational baryogenesis in <italic>f</italic>( <italic>T, L<inf>m</inf></italic>) gravity