In this work, we explore the cosmological dynamics of a modified gravity framework based on the function $$f(Q,B)=\delta Q^{2}+\beta B$$ , where $\textit{Q}$ denotes the nonmetricity scalar and $\textit{B}$ is the boundary term that relates $\textit{Q}$ to the Ricci scalar. The matter sector is modeled using the Modified Chaplygin Gas (MCG) with the equation of state $$p=A\rho -\frac{D_{1}}{\rho ^{\alpha }}$$ , allowing the model to interpolate between early-time matter behavior and late-time cosmic acceleration. By deriving an analytical expression for the Hubble parameter $\textit{H}$($\textit{z}$), we perform a parameter estimation using Markov Chain Monte Carlo (MCMC) techniques in conjunction with the latest cosmological observations: 46 Hubble parameter measurements, 15 BAO data points, DESI DR2 BAO data and the Pantheon+ Type Ia supernovae compilation. The best-fit values are obtained as $$H_0=72.2814^{+3.4702}_{-4.5209}$$ km/s/Mpc, $$A_s = 0.6964^{+0.0779}_{-0.1258}$$ , $$\alpha = 0.0027^{+0.0225}_{-0.0209}$$ and $$A = 0.0024^{+0.0702}_{-0.0464}$$ . The deceleration parameter transitions at redshift $$z_{tr} \approx 0.946$$ , while the present-day value is $$q_0 = -0.789$$ . The model yields an age of the Universe $$t_0 \approx 13.53$$ Gyr and a present EoS parameter $$\omega _0 \approx -0.691$$ , which reflects the late-time acceleration consistent with observational bounds. These results demonstrate that the MCG scenario within $\textit{f}$($\textit{Q}$, $\textit{B}$) gravity provides a viable and observationally consistent framework for explaining the late-time accelerated expansion of the Universe.

India

Amit Samaddar

S. Singh

A new parametric study of $\textit{f}$($\textit{Q}$, $\textit{B}$) gravity with modified Chaplygin gas and recent observations

The anisotropic distribution of ultra high energy cosmic rays (UHECRs) remains a compelling and deeply informative observable in astro-particle physics, illuminating their enigmatic origins, extreme acceleration processes, and trajectories shaped by the cosmic large-scale structure. Among the hierarchy of anisotropy modes, the dipole stands out as a particularly sensitive tracer reflecting both the spatial configuration of sources and the foundational cosmological model. In this work, we conduct a rigorous comparative analysis of dipolar anisotropy within the diffusive propagation regime, evaluating its evolution across three gravitational framework: the standard ΛCDM model, a power-law extension of <italic>f</italic>( <italic>R</italic>) modified gravity, and the Starobinsky inflationary scenario. Our objective is to disentangle the gravitational signatures embedded in UHECR anisotropy, with particular emphasis on deviations arising from extended theories of gravity within the <italic>f</italic>( <italic>R</italic>) formalism. The results reveal a striking dependence on the underlying gravitational paradigm: the power-law model predicts significantly enhanced anisotropies, &#923;CDM consistently produces the most suppressed amplitudes, and the Starobinsky model exhibits an intermediate profile with partial convergence toward &#923;CDM. These findings reinforce the notion that UHECR anisotropy is not merely a reflection of astrophysical processes, but also a subtle messenger of the fundamental gravitational laws governing the universe offering a novel and promising avenue for testing physics beyond the standard cosmological framework.

Pakistan

Iftikhar Ahmad

Muhammad Mahtisham

Azerbaijan

China

Adnan Malik

Saudi Arabia

Fatemah Mofarreh

Model-dependent predictions for UHECR dipolar anisotropies in a <italic>f</italic>( <italic>R</italic>) modified gravity

General Relativity (GR) is not the only way gravity can be geometrized. Instead of curvature, the Teleparallel Theory attributes gravity to the torsion <italic>T</italic>, which is related to the antisymmetric part of the connection. On the other hand, the Symmetric Teleparallel Theory no longer preserves metricity, describing gravity through the non-metricity tensor <italic>Q<inf>&#945;&#956;&#957;</inf></italic>&#8239;&#8801;&#8239;&#8711; <inf><italic>&#945;</italic></inf> <italic>g<inf>&#956;&#957;</inf></italic>. These descriptions give form to what is known as geometrical trinity of gravity. Recently, the extensions of GR have been intensively investigated in order to solve the theoretical impasses which have arisen. In this sense, it is also useful to investigate the extensions of alternative descriptions of gravity, which leads us to the so-called <italic>f</italic>( <italic>T</italic>) and <italic>f</italic>( <italic>Q</italic>) gravities. In this paper, we consider a family of <italic>f</italic>( <italic>Q</italic>) models and obtain their corresponding Tolman-Oppenheimer-Volkoff equations applied to polytropic stars. It is worth mentioning that the <italic>f</italic>( <italic>Q</italic>) covariant formulation is adopted and we present a new equation that substantially simplifies the numerical calculations. Using numerical integration, it is possible to solve a system of differential equations to calculate, among other things, the maximum mass and mass-radius relation allowed. In addition, we explicitly show the non-metricity behavior inside and outside the star.

Brazil

J.C.N. de Araujo

H.G.M. Fortes

Polytropic stars in <math altimg='si11.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>Q</mi><mo linebreak='goodbreak'>+</mo><mi>&#958;</mi><msup><mi>Q</mi><mn>2</mn></msup></mrow></math> covariant formulation

We perform a comprehensive investigation of the radiative decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>P</mi></math>-wave charmed baryons in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></math> flavor <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mn mathvariant="bold">6</mn></mrow><mrow><mi>F</mi></mrow></msub></mrow></math> representation, employing the light-cone quantum chromodynamics (QCD) sum rule approach within the framework of heavy quark effective theory. We analyze their electromagnetic transitions into ground-state charmed baryons via photon emission. When combined with the mass spectra and strong decay properties previously studied in Yang and Chen [<a href="http://dx.doi.org/10.1103/PhysRevD.104.034037">Phys. Rev. D 104, 034037 (2021)</a>], our results constitute a systematic and complete QCD sum rule analysis of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>P</mi></math>-wave singly charmed baryons within the framework of heavy quark effective theory. As summarized in Table V, several excited charmed baryons are found to possess suppressed strong decay widths, thereby rendering their radiative decay channels particularly significant for experimental identification and theoretical understanding.

Xuan Luo

Hua-Xing Chen

Er-Liang Cui

Hui-Min Yang

Dan Zhou

Zhi-Yong Zhou

Radiative decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>P</mi></mrow></math>-wave charmed baryons in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></math> flavor <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mn>6</mn><mi mathvariant="normal">F</mi></msub></math> representation

In this work, we explore the existence of wormhole geometries within the framework of <italic>f</italic>( <italic>R, T</italic>) gravity by employing a novel functional form based on the Capozziello-De Laurentis model, given by <math altimg='si18.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>&#945;</mi><msup><mi>R</mi><mi>n</mi></msup><mo linebreak='goodbreak'>&#8722;</mo><mi>&#946;</mi><msup><mi>R</mi><mrow><mo>&#8722;</mo><mi>q</mi></mrow></msup><mo linebreak='goodbreak'>+</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mi>&#955;</mi><mi>T</mi></mrow></math>. We assume a static, spherically symmetric spacetime and analyze the viability of wormhole solutions by imposing appropriate constraints on the shape function. Our investigation reveals specific parameter regions where traversable wormhole configurations can be realized without the necessity of exotic matter. Furthermore, we extend our analysis to perfect fluid models and two different equation-of-state (EoS) scenarios: <math altimg='si19.svg'><mrow><msub><mi>P</mi><mi>r</mi></msub><mo linebreak='goodbreak'>=</mo><mi>k</mi><mi>&#961;</mi></mrow></math> and <math altimg='si20.svg'><mrow><msub><mi>P</mi><mi>t</mi></msub><mo linebreak='goodbreak'>=</mo><mi>k</mi><mi>&#961;</mi></mrow></math>. For each case, we confirm that the obtained shape functions satisfy the required conditions for wormhole existence. Additionally, we examine the energy conditions and find that they remain valid, reinforcing the physical plausibility of the constructed wormhole solutions. Our results demonstrate that viable wormhole geometries can emerge in <italic>f</italic>( <italic>R, T</italic>) gravity under suitable parameter choices, providing further insights into the role of modified gravity in astrophysical structures.

M. Ilyas

Khalid Masood

South Korea

Nehad Ali Shah

Fawad Khan

Traversable wormhole solutions through Capozziello-De Laurentis model in <italic>f</italic>( <italic>R, T</italic>) gravity

Baryogenesis refers to the physical process responsible for generating the observed baryon asymmetry in the early universe. The presence of a nonzero baryon number density suggests a surplus of matter over antimatter. In this study, a novel approach is proposed to verify the direct consequences of late-time observations on gravitational baryogenesis. The incorporation of two key data sets, DESI and gravitational wave observations, makes the analysis more intriguing. In the teleparallel framework, the methodology connects the primordial time to the late time. The intermediating epochs are also investigated with the help of the deceleration parameter. Our results show that the net remaining asymmetry yields a baryon-to-entropy ratio in excellent agreement with observations.

Sai Swagat Mishra

N.S. Kavya

P.K Sahoo

Effects of DESI and GW observations on <italic>f</italic>( <italic>T</italic>) gravitational baryogenesis

We discuss the conversion mechanism from scalar field to gravitational waves in magnetic background in <italic>f</italic>( <italic>R</italic>) gravity minimal coupled to the Maxwell electrodynamics. Applying the conversion in early universe with primordial magnetic field and the neutron star with strong magnetosphere, the generated gravitational waves, converted from the scalar field, exhibit distinct power spectra which can be potentially probed by future experiments such as DECIGO, BBO, CE and ET.

Italy

Salvatore Capozziello

Qingyu Gan

Gravitational waves in minimal Maxwell <italic>f</italic>( <italic>R</italic>) gravity

We study the symmetries and conserved quantities in $$f(R)$$ gravity for the static, spherically symmetric Reissner–Nordström spacetime using two complementary frameworks: Noether symmetries and Mei symmetries. Starting from a canonical Lagrangian for radial metric functions and the curvature scalar $$R$$ , we derive the associated Hamiltonian and show that the Legendre map is regular whenever both the first derivative of $\textit{f}$($\textit{R}$) with respect to $\textit{R}$ and the second derivative with respect to $\textit{R}$ is non-zero. Within Noether’s approach (variational and Lie-derivative forms), we obtain general, canonical, and internal symmetry classes and identify explicit generators; for the quadratic model $$f(R)=R^{2}$$ these include radial translations and scaling symmetries. We then formulate Mei symmetry conditions as invariance of the Euler–Lagrange equations under the first prolongation, which yields an overdetermined partial differential equation (PDE) system for the generator components. Solving this system for $$f(R)=R^{2}$$ , we find eight independent Mei generators and construct the corresponding conserved currents, some with no direct Noether analogue. The analysis demonstrates that Mei symmetries extend the standard Noether framework for higher-order Lagrangians and provide additional conserved quantities relevant to black-hole dynamics in modified gravity. We conclude with a comparison of the two symmetry schemes and outline applications to broader $$f(R)$$ models and to rotating spacetimes.

Egypt

Tahia Dabash

United States

Moataz Emam

Germany

Lukas Schöppner

Symmetry and conserved quantities in $$ f(R) $$ -gravity: Mei vs. Noether approaches

Inflation, the rapid expansion of spacetime in the early universe, provides an elegant resolution to several fundamental cosmological problems. Among various theoretical approaches, <italic>f</italic>( <italic>R</italic>) gravity offers a minimal yet powerful extension of General Relativity capable of generating inflationary dynamics. In this work, we aim to provide a detailed and systematic derivation of a bottom-up analytical reconstruction method for <italic>f</italic>( <italic>R</italic>) gravity, given the number of e-folds and the scalar power spectrum under the slow-roll approximation. Through explicit calculation, we demonstrate that an exponential dependence of the scalar spectrum on the e-fold number leads to the theory <math altimg='si1.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mfrac><msup><mi>R</mi><mn>2</mn></msup><mrow><mn>8</mn><mi>&#954;</mi><msub><mi>V</mi><mn>0</mn></msub><mspace width='-0.16em' /><msup><mrow><mo stretchy='true'>[</mo><msqrt><mfrac><mn>3</mn><mrow><mn>2</mn><mi>&#954;</mi></mrow></mfrac></msqrt><mi>ln</mi><mspace width='-0.16em' /><mrow><mo stretchy='true'>(</mo><mfrac><mi>R</mi><msub><mi>R</mi><mn>0</mn></msub></mfrac><mo stretchy='true'>)</mo></mrow><mo>&#8722;</mo><msub><mi>&#981;</mi><mn>0</mn></msub><mo stretchy='true'>]</mo></mrow><mrow><mn>2</mn><mo>(</mo><mi>&#945;</mi><mo>&#8722;</mo><mn>1</mn><mo>)</mo></mrow></msup></mrow></mfrac></mrow></math>, while a linear dependence yields, <math altimg='si2.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><msub><mi>A</mi><mn>0</mn></msub><mfrac><msup><mi>R</mi><mn>2</mn></msup><msup><mrow><mo stretchy='true'>(</mo><mfrac><mi>R</mi><msub><mi>R</mi><mn>0</mn></msub></mfrac><mo stretchy='true'>)</mo></mrow><msqrt><mfrac><mrow><mn>3</mn><mi>&#945;</mi></mrow><mrow><mn>2</mn><mi>&#954;</mi></mrow></mfrac></msqrt></msup></mfrac></mrow></math>. Our analysis provides a transparent derivation of these functional forms and highlights how specific choices of the scalar spectrum naturally reconstruct distinct inflationary <italic>f</italic>( <italic>R</italic>) models.

Thailand

David Senjaya

<italic>f</italic>( <italic>R</italic>) Cosmology, analytical inversion method

In this work, we present a new analysis for <italic>f</italic>( <italic>R, T</italic>) gravity by exploring the energy momentum tensor. We demonstrate that <italic>f</italic>( <italic>R, T</italic>) gravity with the form <math altimg='si40.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mn>2</mn><msup><mi>&#954;</mi><mn>2</mn></msup><mi>&#955;</mi><mi>T</mi><mo linebreak='goodbreak'>&#8722;</mo><mn>2</mn><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></mrow></math> is equivalent to Running Vacuum Energy (RVE), which interacts with the components of the cosmic fluid, namely dark matter and radiation. Interestingly, the form of such interaction is inferred from the non-conservation of the stress energy tensor in <italic>f</italic>( <italic>R, T</italic>) gravity rather than being introduced in a phenomenological manner. Furthermore, the parameters that distinguish RVE from &#923;CDM are fixed once the parameter of <italic>f</italic>( <italic>R, T</italic>) gravity, <italic>&#955;</italic>, is known. To illustrate our setup, we perform a Markov Chain Monte Carlo analysis of three interaction scenarios using a combination of different data. we find that the parameters characterizing the RVE model are very small as expected. These results give an accuracy to this equivalence between <italic>f</italic>( <italic>R, T</italic>) gravity under consideration and support the recent result obtained from a quantum field theory in curved space-time point of view which could open a new relationship between <italic>f</italic>( <italic>R, T</italic>) gravity and quantum field theory. Finally, the interaction of the running vacuum increases the current value of the Hubble rate by 3.5&#8201;% compared to the &#923;CDM model, which may be a promising study for the Hubble tension.

Morocco

Ahmed Errahmani

Mounia Magrach

Safae Dahmani

Amine Bouali

Taoufik Ouali

Emergence of running vacuum energy in <italic>f</italic>( <italic>R, T</italic>) gravity : Observational constraints