Motivated by the first observation of $\rm CP $ violation in baryon decays, we study the topological amplitudes of bottom baryon decays in the $ S U(3)_{\rm F} $ limit. The topological diagrams of the charmless two-body decays of bottom baryons are presented in detail. The linear relations between topologies and $ S U(3) $ irreducible amplitudes are derived through tensor contraction and $ S U(3) $ decomposition. Four amplitudes among the 13 independent amplitudes are critical to the $\rm CP$ asymmetries. The small $ \rm CP $ asymmetries might indicate small relative strong phases between amplitudes $ A_2 $ and $ A_{12,14}^\prime $ . To avoid them, we suggest measuring $\rm CP $ asymmetries in the $ \Xi^0_b\to pK^- $ and $ \Xi^-_b\to \Lambda^0 K^- $ decays. Furthermore, the Körner-Pati-Woo theorem can be tested by measuring the branching fractions of the $ \Lambda_b^0\to\Sigma^0K^0_S $ and $ \Lambda_b^0\to\Sigma^-K^+ $ modes.

China

Di Wang

Wei-Chen Fu

Topological amplitudes of bottom baryon decays in the $\textit{SU}$(3)$_{F}$ limit * Supported in part by the National Natural Science Foundation of China (12105099)

We use a modified relativistic quark model to study the properties of excited charmed and charmed strange mesons. We calculate the masses and wave functions of conventional charmed and charmed strange mesons incorporating both spin and $\textit{S}$-$\textit{D}$ mixing effects and fit parameters of the potential model with known experimental states using differential evolution techniques. Using leading Born-Oppenheimer expansion, we compute the spectrum and wave functions of the first gluonic excited state of charmed and charmed strange mesons. We examine the effects of gluonic excitation on the spectrum of the resulting hybrid mesons. Using our calculated spectrum and wave functions, we determine the radiative transitions of the conventional and hybrid open charm mesons. We compare our calculations with experimental data and other works. We expect our results will be beneficial in the detection of charmed and charmed strange conventional and hybrid mesons.

Pakistan

Saba Noor

Faisal Akram

Bilal Masud

Study of excited $\textit{D}$ and D$_{s}$ mesons in a relativized quark model * F. A. acknowledges HEC grant 20-15728/NRPU/R&D/HEC/2021, Pakistan

The classical Isaacson’s procedure for describing back-reaction of the averaged energy–momentum for high frequency gravitational waves is generalized to the $\textit{f}$($\textit{R}$) gravity case. From the beginning it is assumed that an initial background could be arbitrary one. Then, we restrict the background to be de Sitter, which is a novelty regarding the study of a back-reaction in $\textit{f}$($\textit{R}$) gravity. Consideration of the de Sitter space as a background spacetime allows us to provide the averaging procedure completely. Using the results on the de Sitter space and generalizing the Isaacson procedure, we construct the averaged energy–momentum on an additionally curved (averaged) background. Consistency tests for de Sitter spacetime are performed both at the background and perturbative regimes. Our results generalize previous studies in which the authors consider the flat (Minkowski) spacetime as the initial background.

Russia

Petr Tretyakov

Alexander Petrov

On energy–momentum tensor for gravitational waves in $\textit{f}$($\textit{R}$) gravity

<p>This study investigates the mass spectra and decay behaviors of the experimentally unobserved <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mi>F</mi></math>-wave singly bottom baryons. Calculating their mass spectra could provide crucial guidance for determining their spectroscopic positions. Additionally, by analyzing their decay properties, we could predict the important decay channels, which are essential for experimental searches and quantum number assignments. Our calculations aim to support ongoing experimental and theoretical efforts in singly bottom baryon spectroscopy.</p>

Zi-Le Zhang

Si-Qiang Luo

Spectroscopic properties of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mi>F</mi></math>-wave singly bottom baryons

This study is concern to the homothetic symmetry approach to get exact solutions for locally rotationally symmetric (LRS) Bianchi type-I spacetimes within the framework of <math altimg='si108.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow></math> gravity, revealing that such spacetimes posses homothetic symmetry of different dimensions. By employing the Rif tree algorithm implemented in Maple, we systematically transform the symmetry and field equations into a set of constraints on the metric functions, enabling the derivation of exact analytical forms for the homothetic vector fields. Furthermore, we compute the corresponding physical quantities, including the energy density <math altimg='si109.svg'><mi>&#961;</mi></math>, pressure <math altimg='si110.svg'><mi>p</mi></math>, Ricci scalar <math altimg='si111.svg'><mi>R</mi></math>, shear scalar <math altimg='si8.svg'><msup><mi>&#963;</mi><mn>2</mn></msup></math>, equation of state <math altimg='si112.svg'><mi>w</mi></math> and modified gravity function <math altimg='si113.svg'><mrow><mi>F</mi><mo>(</mo><mi>r</mi><mo>)</mo></mrow></math>, for each solution, providing crucial insights into the geometric and physical properties of these spacetimes within the <math altimg='si107.svg'><mrow><mi>F</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow></math> gravity.

Jamshed Khan

Sumaira Saleem Akhtar

Ambreen Ayub

Exact LRS Bianchi type I solutions in quadratic <math altimg='si107.svg'><mrow><mi>F</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow></math> gravity from homothetic symmetries: A Rif tree approach

We investigate the construction and viability of rotating Casimir wormholes within the framework of $\textit{f}$($\textit{R}$) gravity, focusing on models of the form $$f(R) = R + \alpha R^2$$ . Building upon previous work in general relativity, where the Casimir effect serves as a physically motivated source of exotic matter, we explore how higher-order curvature corrections impact the energy conditions, stability, and traversability of rotating wormhole geometries. Using a perturbative expansion around small curvature deviations, we derive the modified field equations for a stationary, axisymmetric metric and analyze the interplay between the Casimir-induced stress-energy tensor, thermal corrections, and the effective geometric contributions from $\textit{f}$($\textit{R}$) gravity. Our results show that the inclusion of curvature-induced terms can significantly reduce, and in some parameter regimes locally mitigate, the null energy condition (NEC) violation near the throat. We identify angular velocity profiles, particularly those with exponential damping, that are compatible with the modified gravitational dynamics and helping stabilize the wormhole configuration. A detailed linear perturbation analysis reveals that scalar modes associated with $\textit{f}$($\textit{R}$) gravity can enhance the stability of the wormhole under fluctuations. Furthermore, we evaluate the behavior of the weak, strong, and dominant energy conditions and assess tidal forces experienced by travelers, confirming that these wormholes can be traversable under physically reasonable conditions. This study highlights the potential of modified gravity to support stable, traversable wormhole solutions with reduced reliance on exotic matter.

Iran

Behnam Pourhassan

Rotating Casimir wormholes in $\textit{f}$($\textit{R}$) gravity: a modified gravity extension of exotic spacetime models

In this work, we study early-time inflation within a class of <math altimg='si9.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>&#981;</mi><mo>,</mo><mi>X</mi><mo>)</mo></mrow></math> gravity models under a constant-roll condition. Employing a generalized potential of the form <math altimg='si10.svg'><mrow><mi>V</mi><msup><mrow><mo>(</mo><mi>&#981;</mi><mo>)</mo></mrow><mi>&#963;</mi></msup></mrow></math>, we derive expressions for the spectral index <math altimg='si1.svg'><msub><mi>n</mi><mi>s</mi></msub></math> and tensor-to-scalar ratio <math altimg='si11.svg'><mi>r</mi></math>, demonstrating that the inflationary dynamics are primarily governed by the parameter <math altimg='si6.svg'><mi>&#963;</mi></math> and the shape of the potential. At the upper limit of <math altimg='si1.svg'><msub><mi>n</mi><mi>s</mi></msub></math>, we obtain a de Sitter-like phase, while at the lower limit, the model transitions to a quintessence-like phase through an effective oscillating equation of state parameter (EoS). Therefore, under the tuning parameter <math altimg='si12.svg'><mrow><mi>&#963;</mi><mo linebreak='goodbreak'>&lt;</mo><mn>1</mn></mrow></math>, the model exhibits a smooth transition from a de Sitter-like phase to a quintessence-like phase via the oscillating EoS parameter. The resulting predictions are consistent with recent observations from the Atacama Cosmology Telescope (ACT), combined with CMB lensing and DESI BAO data.

Türkiye

A.I. Keskin

Mehmet Yaşar

K. Kurt

Constant roll inflationary dynamics with generalized potentials in <math altimg='si9.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>&#981;</mi><mo>,</mo><mi>X</mi><mo>)</mo></mrow></math> gravity

We consider the inhomogeneous Morris–Thorne wormhole metric with matter tensors characterised by a novel linear equation of state in $\textit{f}$($\textit{R}$) gravity. Using the Einstein’s field equations in metric $\textit{f}$($\textit{R}$) gravity we model solutions for both wormhole as well as $\textit{f}$($\textit{R}$) gravity. We obtain four different wormhole models, two wormholes are characterised by solid angle deficit, three are not asymptotically extendible, while one is asymptotically flat with zero tidal force. These are supported by four different power law $\textit{f}$($\textit{R}$) models. The parameter space of the models can support both null energy conditions (NEC) satisfying as well as violating wormhole. In case of NEC satisfying matter, the associated $\textit{f}$($\textit{R}$) is ghost. The $\textit{f}$($\textit{R}$) models obtained have been independently substantiated for cosmological feasibility and valid parameter space was obtained corresponding to cosmologically viable $\textit{f}$($\textit{R}$). Suitable scalar-tensor representation of the corresponding $\textit{f}$($\textit{R}$) models have been presented using the correspondence of $\textit{f}$($\textit{R}$) gravity with Brans–Dicke (BD) theory of gravity. The robustness of the wormhole solutions were further analysed with the BD scalar fields in the hybrid metric-Palatini gravity, which showed excellent results. Lastly as an independent astrophysical probe for the wormhole we have obtained the location of their photon spheres and have connected them with the Herrera Complexity factor in $\textit{f}$($\textit{R}$). Our results show that the relation between the complexity factor and existence of photon spheres remains fundamentally unaltered in $\textit{f}$($\textit{R}$) as compared to Einstein’s gravity.

India

Subhasis Nalui

Subhra Bhattacharya

Designing wormholes in novel power-law $\textit{f}$($\textit{R}$): a mathematical approach with a linear equation of state

<list id='lst0002'><list-item id='lstitem0001'><label>&#8226;</label><para id='p0001'>Construction of anisotropic compact stellar models in <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></mrow></math> gravity using the Durgapal-Fuloria metric.</para></list-item><list-item id='lstitem0002'><label>&#8226;</label><para id='p0002'>Implementation of three viable <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></mrow></math> models combining the Hu-Sawicki <math altimg='si40.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow></math> function with logarithmic, power-law, and rational <math altimg='si41.svg'><mrow><mi>f</mi><mo>(</mo><mi>G</mi><mo>)</mo></mrow></math> extensions.</para></list-item><list-item id='lstitem0003'><label>&#8226;</label><para id='p0003'>Analysis of ten observed compact star candidates, confirming stability, causality, and physical acceptability.</para></list-item><list-item id='lstitem0004'><label>&#8226;</label><para id='p0004'>Junction conditions and energy conditions are satisfied, ensuring smooth matching to exterior spacetime and physical viability.</para></list-item><list-item id='lstitem0005'><label>&#8226;</label><para id='p0005'>Detailed comparison with GR predictions, showing that higher-order curvature terms extend the stability domain and allow more massive stars.</para></list-item></list>

Azerbaijan

M. Ilyas

Z. Yousaf

M.Z. Bhatti

Impact of anisotropy on compact stellar structures in Durgapal-Fuloria spacetime under <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></mrow></math> gravity

<p>Nucleon structure functions, as measured in lepton-nucleon scattering, have historically provided a critical observable in the study of partonic dynamics within the nucleon. However, at very large parton momenta, it is both experimentally and theoretically challenging to extract parton distributions due to the probable onset of nonperturbative contributions and the unavailability of high-precision data at critical kinematics. Extraction of the neutron structure and the d quark distribution have been further challenging because of the necessity of applying nuclear corrections when utilizing scattering data from a deuteron target to extract the free neutron structure. However, a program of experiments has been carried out recently at the energy-upgraded Jefferson Lab electron accelerator aimed at significantly reducing the nuclear correction uncertainties on the d quark distribution function at large partonic momentum. This allows leveraging the vast body of deuterium data covering a large kinematic range to be utilized for d quark parton distribution function extraction. In this Letter, we present new data from experiment E12-10-002, carried out in Jefferson Lab Experimental Hall C, on the deuteron to proton cross section ratio at large Bjorken <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>x</mi></mrow></math>. These results significantly improve the precision of existing data and provide a first look at the expected impact on quark distributions extracted from parton distribution function fits.</p>

United States

D. Biswas

F.A. Gonzalez

W. Henry

A. Karki

C. Morean

A. Nadeeshani

A. Sun

Canada

Z. Ahmed

Saudi Arabia

S. Alsalmi

W. Armstrong

A. Asaturyan

C. Ayerbe Gayoso

V. Berdnikov

H. Bhatt

D. Bhetuwal

P. Bosted

E. Brash

M.H.S. Bukhari

J.P. Chen

M. Chen

M.E. Christy

S. Covrig Dusa

K. Craycraft

S. Danagoulian

D. Day

M. Diefenthaler

M. Dlamini

J. Dunne

B. Duran

D. Dutta

R. Ent

H. Fenker

N. Fomin

E. Fuchey

D. Gaskell

T.N. Gautam

J.O. Hansen

F. Hauenstein

A.V. Hernandez

T. Horn

G.M. Huber

M.K. Jones

S. Joosten

M.L. Kabir

C. Keppel

A. Khanal

P.M. King

E. Kinney

M. Kohl

N. Lashley-Colthirst

S. Li

W.B. Li

A.H. Liyanage

D. Mack

S. Malace

P. Markowitz

J. Matter

D. Meekins

R. Michaels

Armenia

A. Mkrtchyan

H. Mkrtchyan

Z. Moore

S.J. Nazeer

S. Nanda

G. Niculescu

I. Niculescu

D. Nguyen

 Nuruzzaman

B. Pandey

S. Park

E. Pooser

A.J.R. Puckett

M. Rehfuss

J. Reinhold

B. Sawatzky

G.R. Smith

H. Szumila-Vance

A.S. Tadepalli

V. Tadevosyan

R. Trotta

S.A. Wood

C. Yero

J. Zhang

New Measurements of the Deuteron-to-Proton <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> Structure-Function Ratio