We systematically investigate static plane symmetric configurations in $\textit{f}$($\textit{Q}$) gravity. For vacuum regions, we discuss the constancy of the nonmetricity scalar $\textit{Q}$ and derive general vacuum solutions, which correspond effectively to Taub-(anti) de Sitter spacetimes with a cosmological constant determined by the specific $\textit{f}$($\textit{Q}$) model. By matching a singular thin shell source to the vacuum solutions, we relate the shell’s energy density and pressure to the integration constants of the exterior geometry. We also examine a finite-thickness slab as another matter source supporting the vacuum solution. Through numerical analysis of a quadratic model $$f(Q)=Q+\alpha Q^2$$ with isotropic matter, we show that the maximum pressure inside the slab generally does not coincide with the geometric center. Moreover, a negative $$\alpha $$ with larger magnitude leads to higher internal pressure and a thicker slab, while models with positive $$\alpha $$ are incompatible with a self-gravitating slab of positive pressure.

China

Jun-Qin Long

Rui-Hui Lin

Xiang-Hua Zhai

Static plane symmetric solutions in $\textit{f}$($\textit{Q}$) gravity

We investigate the consistency of linear dark sector interactions within coincident <italic>f</italic>( <italic>Q</italic>) gravity restricting to a &#923;CDM-mimicking background. We focus on a linear model supplemented by a geometrically motivated background-inert <math altimg='si23.svg'><msqrt><mi>Q</mi></msqrt></math> correction ensuring expansion history identical to &#923;CDM, with all the gravitationally motivated effects arising exclusively at the perturbation level. We show that background consistency enforces a nontrivial structural restriction - any interaction proportional to the matter density is mathematically incompatible leading to a unique dark energy proportional coupling. This unique no-go result reflects the geometric origin of the effective dark energy sector in <italic>f</italic>( <italic>Q</italic>) gravity. The parameter space of this residual interacting sector is quantified using Markov Chain Monte Carlo analysis using late-time cosmological data including Redshift-Space Distortions, updated Cosmic Chronometers, DESI DR2 BAO and Type Ia Supernovae. The <math altimg='si23.svg'><msqrt><mi>Q</mi></msqrt></math> term modifies growth structure through a gravitational coupling, introducing perturbation level sensitivity in <italic>f&#963;</italic> <inf>8</inf>. We find that all the parameters are tightly constrained and are compatible with zero, indicating the strong observational limits on perturbation level departures from &#923;CDM. The model remains statistically compatible with &#923;CDM according to information criteria, while preserving a viable growth history. Our results therefore establish sharp structural and observational bounds on interacting dark energy scenarios in Symmetric Teleparallel Gravity, providing a benchmark consistency test for future high precision surveys.

India

Ameya Kolhatkar

Preet Dalal

P.K. Sahoo

Structural constraints on interacting dark sector in ΛCDM-mimicking <italic>f</italic>( <italic>Q</italic>) gravity

We investigate the realization of a nonsingular cosmological bounce in metric $\textit{f}$($\textit{R}$) gravity using a controlled exponential deformation of the Starobinsky $$R^{2}$$ model. Adopting a smooth Gaussian-type bouncing scale factor, we first demonstrate a no-go result showing that a positive-curvature vacuum bounce cannot be supported by the model $$f(R)=R+\alpha R^{2}(1-e^{-R/R_b})$$ alone. We then show that a minimal extension obtained by introducing a constant term restores the bounce exactly, with the constant fixed algebraically by the bounce condition. A systematic parameter-space scan is performed to identify regions free of ghost and tachyonic instabilities. Working in the Einstein frame, we study the evolution of scalar and tensor perturbations across the bounce and show that both remain finite and well behaved. Our results establish a minimal, perturbatively stable realization of a vacuum bounce in $\textit{f}$($\textit{R}$) gravity that goes beyond background-level constructions.

Egypt

South Africa

G. Nashed

Saudi Arabia

A. Eid

A minimal and stable vacuum bounce in exponential $\textit{f}$($\textit{R}$) gravity

<italic>f</italic>( <italic>R</italic>) gravity is a well-known modification of General Relativity, which is used in various models of dark matter and dynamical dark energy. We study static spherically symmetric (SSS) asymptotically flat configurations of the <italic>f</italic>( <italic>R</italic>) gravity in the Einstein frame for three known scalaron potentials with different asymptotic properties. The main attention is paid to the case of astrophysically relevant configuration mass <italic>M</italic> and scalaron mass <italic>&#956;</italic> greater than several <italic>meV</italic>, according to existing experimental constraints. This means very large values of the dimensionless (in geometrized units) parameter <italic>M&#956;</italic>, leading to specific properties of the SSS solutions. We consider a sufficiently large size of a scalarization region <italic>r</italic> <inf>0</inf>&#8239;&#8811;&#8239; <italic>r<inf>g</inf></italic>, where the space-time metric is essentially different from the Schwarzschild one. It turns out that the scalaron field has universal behavior regardless of <italic>M&#956;</italic> and <italic>r</italic> <inf>0</inf> and is practically the same for different scalaron potentials. Asymptotic parameters of the metric near the naked singularity at the center of the SSS configuration are obtained analytically for all the models. The test body circular orbits are discussed in view of observational signatures, which can distinguish these configurations from a regular black hole.

Ukraine

V.I. Zhdanov

Universality in static spherically symmetric solutions of <italic>f</italic>( <italic>R</italic>) gravity

This study presents a novel interpretation of complexity in the formalism of <math altimg='si1.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 mathvariant='script'>T</mi><mo>)</mo></mrow></math> gravity, where <italic>R</italic> specifies the Ricci scalar, <math altimg='si2.svg'><msub><mi mathvariant='script'>L</mi><mi>m</mi></msub></math> is written as matter Lagrangian that describes characteristics of the matter fields, and <math altimg='si3.svg'><mi mathvariant='script'>T</mi></math> represents the trace of energy-momentum tensor. We commence with the contemplation of the inner sector as a cylindrical configuration having anisotropic matter and linked with the exterior region through a hypersurface. We determine the modified field equations associated with <math altimg='si1.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 mathvariant='script'>T</mi><mo>)</mo></mrow></math> gravity and assume the preliminarily established relations between the conformal tensor and the intrinsic curvature. We consider the generally employed mathematical expressions for Tolman mass and C-Energy and evaluate their relationship with the conformal tensor. The structural scalars are calculated from orthogonal splitting of Riemann tensor, out of which <italic>Y<inf>TF</inf></italic> is categorized as complexity factor for the inferred fluid composition. It is important to specify that the complexity factor is eradicated in the framework of uniform matter configuration and also in the scenario when anisotropic terms are canceled with each other. Significant results related to the Weyl scalar, Tolman mass, and the complexity factor are derived in <math altimg='si1.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 mathvariant='script'>T</mi><mo>)</mo></mrow></math> gravity. The vanishing complexity constraint is considered in order to deal with the modified field equations that have extra degrees of freedom and to find particular solutions corresponding to the specific models.

Pakistan

A. Rehman

Azerbaijan

M. Yousaf

Uzbekistan

Bekzod Rahmatov

Javlon Rayimbaev

Munisbek Akhmedov

Complexity evaluation related to the cylindrically symmetric anisotropic matter in <math altimg='si1.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 mathvariant='script'>T</mi><mo>)</mo></mrow></math> theory

We investigate the dynamics of four-dimensional $$ \mathcal{N}=2 $$ SU(2) super Yang-Mills theory on an AdS background. We propose that the boundary conditions that preserve the AdS super-isometries are determined by maximizing the real part of the AdS partition function $\textit{F}$ = −log $\textit{Z}$ . At weak coupling Λ$\textit{L}$ ≪ 1 the maximization singles out the Dirichlet boundary condition with an SU(2) boundary global symmetry, corresponding to the classical vacuum at the origin of the Coulomb branch with fully un-higgsed gauge group. We find that for Λ$\textit{L}$ ~ 𝒪(1) new boundary conditions are favored, with gauge-group higgsed down to U(1), matching the expectation from the flat space limit. We use supersymmetric localization to compute $\textit{Z}$ nonperturbatively. We further provide evidence for a relation between $\textit{F}$ and the $$ \mathcal{N}=2 $$ prepotential in AdS background.

Davide Bason

United Kingdom

Christian Copetti

Italy

Lorenzo Pietro

United States

Ziming Ji

$$ \mathcal{N}=2 $$ super Yang-Mills in AdS4 and $\textit{F}$ AdS-maximization

We investigate the cosmological implications of two analytically solvable <italic>f</italic>( <italic>Q</italic>) gravity models within the framework of symmetric teleparallel gravity. The first model corresponds to the linear case <math altimg='si9.svg'><mrow><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo><mo>=</mo><mi>&#945;</mi><mi>Q</mi><mo linebreak='goodbreak'>+</mo><mi>&#946;</mi></mrow></math>, which is dynamically equivalent to general relativity with a cosmological constant, while the second model introduces a nonlinear correction <math altimg='si10.svg'><mrow><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo><mo>=</mo><mi>&#945;</mi><mi>Q</mi><mo linebreak='goodbreak'>+</mo><mi>&#946;</mi><mo linebreak='goodbreak'>/</mo><mi>Q</mi></mrow></math>. By assuming pressureless matter, we derive exact background solutions for both models, allowing the Hubble expansion rate, the matter energy density, and the deceleration parameter to be expressed in terms of the redshift. Then, we constrain the model parameters using a Bayesian Markov Chain Monte Carlo analysis based on <italic>H</italic>( <italic>z</italic>) cosmic chronometer measurements, the Pantheon+SH0ES Type Ia supernova compilation, and DESI baryon acoustic oscillation data. The results show that the linear model reproduces the standard &#923;CDM background dynamics, whereas the nonlinear model leads to modified cosmological evolution while remaining consistent with observational data. Moreover, the reconstructed deceleration parameter indicates a transition from an early matter-dominated decelerating phase to the present accelerated expansion. In addition, the <italic>Om</italic>( <italic>z</italic>) diagnostic reveals that Model I behaves identically to &#923;CDM, while Model II exhibits a redshift-dependent behavior indicative of a phantom-like effective regime. We conclude that symmetric teleparallel <italic>f</italic>( <italic>Q</italic>) gravity presents a viable geometric framework for describing the late-time acceleration of the universe.

Morocco

M. Koussour

Alnadhief H.A. Alfedeel

I. Davletov

J. Rayimbaev

Matching exact cosmological solutions in linear and nonlinear <italic>f</italic>( <italic>Q</italic>) gravity with cosmological data

This article explores traversable wormhole geometries obtained in the context of the symmetric teleparallel gravity theory and highlights their distinctive physical characteristics. Our methodology involves determining the tidal force by employing a specified form of the shape function along with an appropriate equation of state for Case I. In order to extract the shape functions associated with the wormhole solution, we apply the null-complexity condition with tidal force in Case II. In Case III, we utilize the balancing Tolman–Oppenheimer–Volkoff equation in conjunction with a tidal force to obtain viable wormhole shape function. The analysis focuses on the dependence of wormhole characteristics on the parameter $$\zeta $$ . The energy conditions are examined within their respective validity domains for various ranges of the model parameters. We also calculate, the volume integral quantifier, the extent of exotic matter needed to uphold the traversable wormhole structure. Through the effective potential for timelike geodesics, the influence of angular momentum on trajectories is clarified, and the corresponding deflection angle evaluation points to significant light bending close to the throat. By introducing small radial perturbations around the equilibrium shell radius, we examine the stability characteristics for all considered shape functions.

Sweeti Kiroriwal

Oman

S. Maurya

Jitendra Kumar

Wormhole solutions under tidal force constraints in $\textit{f}$($\textit{Q}$) gravity: a unified approach

Using the topological-diagram approach based on SU(3) flavor symmetry, we investigate two-body $$ {\Lambda}_c^{+}\to \textbf{B}S $$ decays, where denotes the final-state baryon and $\textit{S}$ refers to a light scalar meson, such as $\textit{f}$ /$\textit{f}$ (980), $\textit{a}$ /$\textit{a}$ (980), $\textit{σ}$ /$\textit{f}$ (500), or $$ \kappa /{K}_0^{\ast }(700) $$ . Our analysis indicates that interpreting the light scalar mesons as tetraquark states provides a more consistent description of the currently available experimental data. In particular, this framework naturally accommodates the experimentally observed branching fraction $$ \mathcal{B}\left({\Lambda}_c^{+}\to \Lambda {a}_0^{+}\right) $$ , which exceeds predictions based solely on long-distance effects by an order of magnitude. Within the tetraquark scenario, we predict $$ \mathcal{B}\left({\Lambda}_c^{+}\to {\Sigma}^{+}{f}_0\right)=\left(4.9\pm 1.9\right)\times {10}^{-2} $$ and $$ \mathcal{B}\left({\Lambda}_c^{+}\to p{f}_0\right)=\left(3.6\pm 1.4\right)\times {10}^{-3} $$ . Owing to $\textit{f}$ − $\textit{σ}$ mixing, $$ \mathcal{B}\left({\Lambda}_c^{+}\to {\Sigma}^{+}{\sigma}_0\right) $$ and $$ \mathcal{B}\left({\Lambda}_c^{+}\to p{\sigma}_0\right) $$ are suppressed to the levels of 1 × 10 and 5 × 10 , respectively. These modes therefore provide sensitive probes of the internal structure of the light scalar mesons. More generally, the remaining branching ratios of $$ {\Lambda}_c^{+}\to \textbf{B}S $$ are found to be comparable to those of $$ {\Lambda}_c^{+}\to \textbf{B}M $$ , where $\textit{M}$ denotes a pseudoscalar meson. Their predicted sizes suggest that these decay modes should be accessible to ongoing and near-future experimental studies at BESIII, Belle II, and LHCb.

Y. Wang

Y. Hsiao

Charmed $$ {\Lambda}_c^{+} $$ baryon decays into light scalar mesons in the topological SU(3) $\textit{f}$ framework

In the present work, we incorporate redshift space distortion measurement to investigate the growth of large scale structure within the framework of multi-fluid cosmology in the context of $\textit{f}$($\textit{G}$) gravity. Using 3 different $\textit{f}$($\textit{G}$) gravity models, where $\textit{f}$($\textit{G}$) is the function of Gauss–Bonnet invariant, we compare the predictions of $\textit{f}$($\textit{G}$) gravity expansion history—through the Friedmann equation with Hubble data, BAO data sets and constrain models parameters such as $$\Omega _{m}$$ and $$H_{0}$$ . Within the context of multi-fluid cosmology in $\textit{f}$($\textit{G}$) gravity, we obtain the structure growth equation. This equation is then combined with $$\sigma _{8}$$ to get $$f\sigma _{8}$$ predictions—which is compared with redshift space distortion data to constrain models parameters to obtain best-fit values including $$\sigma _{8}$$ . This involves performing a Markov Chain Monte Carlo (MCMC) analysis for these specific forms of $\textit{f}$($\textit{G}$) models. we also perform a statistical analysis incorporating the Akaike Information Criterion (AIC), the Bayesian Information Criterion (BIC), to assess the goodess-of-fit of the considered models.

Praveen Dhankar

Rwanda

Albert Munyeshyaka

Aritra Sanyal

Safiqul Islam

Farook Rahaman

Constraints on multi-fluid cosmology in $\textit{f}$($\textit{G}$) gravity with different observational data sets