We constrain the Hu–Sawicki and Starobinsky $\textit{f}$($\textit{R}$) gravity models utilizing current electromagnetic (PantheonPlus + cosmic chronometers [PP+CC], Planck, and DESI2) datasets and simulate standard siren (SS) catalogs based on the resulting best-fit parameters. We demonstrate that the simulated SS data provide complementary sensitivity to the modified gravitational wave propagation friction term, thereby enhancing the discriminating power between $\textit{f}$($\textit{R}$) gravity and the $$\varLambda $$ CDM model. However, we note that standard sirens do not offer a viable resolution to the Hubble tension in this analysis, as the inferred constraints are predominantly driven by the fiducial cosmologies adopted in the simulations. Regarding the specific models, we find that for the Hu–Sawicki scenario, several data combinations favor $$F_{RR0}<0$$ , implying potential theoretical instabilities. And, for the Starobinsky model, while electromagnetic-only constraints are nearly symmetric between the two parameter branches ( $$b<0$$ and $$b>0$$ ), the inclusion of SS constraints introduces mild asymmetries, revealing the sensitivity of SS observables to the curvature dependence of the theory. Future truly independent standard siren observations would be crucial for a definitive assessment of $\textit{f}$($\textit{R}$) gravity as an alternative to $$\varLambda $$ CDM.

China

Yi Zhang

Xuanjun Niu

Xianfu Su

Dong-Ze He

The standard siren tests of viable $\textit{f}$($\textit{R}$) cosmologies

The strong coupling $\textit{α}$ is determined with high precision from fits to lattice QCD simulations on the static energy. Our theoretical setup relies on R-improving the three-loop fixed-order prediction for the static energy by removing its $\textit{u}$ = 1/2 renormalon and summing up the associated large (infrared) logarithms which, in combination with radius-dependent renormalization scales (called profile functions) extends the validity of perturbation theory to distances up to ~ 0.5 fm. Furthermore, we resum large ultrasoft logarithms to N LL accuracy using renormalization group evolution. We have checked that the standard four-loop R-evolution treats N LL and higher remnants in a non-symmetric way, hence we also account for this potential bias. Our estimate of the perturbative uncertainty is based on a random scan over the parameters specifying the profile functions and the treatment of R-evolution. We also devise a method to statistically combine into a single dataset results from independent simulations which use different lattice spacing and cover various ranges, which can be used to carry out fits in a much faster way. We explore the dependence of the extracted $\textit{α}$ value on the smallest and largest distances included in the dataset, on how R-evolution is treated, on how the fit is performed, and on the accuracy of ultrasoft resummation. From our final analysis, after evolving to the $\textit{Z}$-pole we obtain $$ {\alpha}_s^{\left({n}_f=5\right)}\left({m}_Z\right)=0.1170\pm 0.0009 $$ , compatible with the world average with the same incertitude.

Spain

Jose Mena-Valle

Vicent Mateu

Pablo Ortega

A precise $\textit{α}$ $\textit{s}$ determination from the R-improved QCD static energy

The processes of $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ are studied within the effective Lagrangian approach. In addition to the “background” contribution from the $\textit{u}$-channel nucleon pole term, the contribution from the $ \Sigma(1660) $ resonance with spin-parity $ J^P=1/2^+ $ is also considered. For the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the $ \Sigma(1660) $ intermediate resonance decaying into $ \pi^0 \Lambda(1405) $ with $ \Lambda(1405) $ decaying into $ \pi^0 \Sigma^0 $ . With our model parameters, the available experimental data on both the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ reactions can be fairly well reproduced. It is shown that the contribution from the $ \Sigma(1660) $ resonance is necessary, and that these experimental measurements could be used to determine some properties of the $ \Sigma(1660) $ resonance.

Xing-Yi Ji

Si-Wei Liu

Wen-Tao Lyu

De-Min Li

En Wang

Ju-Jun Xie

Role of Σ(1660) in the $\textit{K}$ $^{−}$ $\textit{p}$ → $\textit{π}$ $^{0}$ $\textit{π}$ $^{0}$Σ$^{0}$ reaction * Supported by the National Key R&D Program of China (2023YFA1606703, 2024YFE0105200), the National Natural Science Foundation of China (12435007, 12475086, 12192263, 12361141819, 1252200936), the Natural Science Foundation of Henan (232300421140, 252300423951) and the Zhengzhou University Young Student Basic Research Projects (PhD students) (ZDBJ202522)

We study the generalized cusp anomalous dimension, or quark-antiquark potential on the three-sphere, in the presence of a large $\textit{R}$-charge $\textit{L}$ and at strong coupling. Considering the insertion of a local scalar operator of charge $\textit{L}$ on a cusped Wilson loop, we investigate the general solution of the dual string configuration for any value of cusp angles, paying particular attention to the different ranges of the physical parameters and obtaining a unified description that simultaneously captures the near BPS, the antiparallel lines and the large-$\textit{L}$ regimes. We observe, in the limit of small separation between the lines, a non-analytic change in the behavior of the cusp anomaly at a critical value of $\textit{L}$: one crosses from a region dominated by the familiar Coulomb-like singularity to a “deconfined” situation describing the leading Lüscher corrections at large $\textit{L}$ of the generalized cusp anomalous dimension. We derive the equations for small fluctuations around the classical string solution, generalizing previous analysis of the uncharged case, and we study the behavior of the spectrum near the transition region. Finally, we speculate on the field theory origin of the transition and on its implications for the fusion of Wilson lines.

Germany

Davide Bonomi

Valentina Forini

Iceland

Valentina Puletti

Italy

Luca Griguolo

Domenico Seminara

Probing the dynamics of stringy flux tubes with large $\textit{R}$-charge

The $\textit{μ}$-$\textit{e}$ conversion process is one of the most powerful ways to test lepton-flavor-violating (LFV) interactions involving charged leptons. The standard model with massive neutrinos predicts an extremely low rate for $\textit{μ}$-$\textit{e}$ conversion, making this process an excellent probe for testing LFV arising from new physics. Among many theoretical models that can induce LFV, the Supersymmetric model with R-parity violating interactions is one of the most studied for $\textit{μ}$-$\textit{e}$ conversion. In this work, we revisit trilinear $\textit{R}$-parity violating interactions for $\textit{μ}$-$\textit{e}$ conversion, considering renormalization group (RG) running effects from high to low energy scales. The $\textit{μ}$-$\textit{e}$ conversion, $\textit{μ}$ → $\textit{eγ}$, and $\textit{μ}$ → $\textit{eee}$ experimental data are compared to give upper limits on the relevant 15 combinations of the trilinear $\textit{λ′}$ couplings and 6 combinations of the $\textit{λ}$ couplings, certain of which are underexplored in previous studies. We find that RG running effects influence the limits by no more than 30% in most cases, but can improve constraints by ~80% in certain combinations, which cannot be neglected. In the near future, COMET and Mu2e are expected to begin data-taking and aim to provide the most stringent constraints on $\textit{μ}$-$\textit{e}$ conversion. These next-generation $\textit{μ}$-$\textit{e}$ experiments have the ability to give much more comprehensive examinations on most trilinear coupling combinations than the $\textit{μ}$ → $\textit{eγ}$ and $\textit{μ}$ → 3$\textit{e}$ decay experiments. The $\textit{μ}$-$\textit{e}$ experiments will not only deepen our understanding of LFV but also provide a crucial way to examine the underlying new physics contributions.

Yu-Qi Xiao

Xiao-Gang He

Hong-Yi Niu

Rong-Rong Zhang

Revisiting $\textit{μ}$-$\textit{e}$ conversion in $\textit{R}$-parity violating SUSY

<p>We study the discovery prospects for a doubly charged Higgs boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup></math> in the 2-Higgs doublet model with type-II seesaw at future <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> colliders. Focusing on the three-body channels <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup><msup><mi>W</mi><mo>∓</mo></msup></math>, we scan the model parameter space subject to theoretical consistency as well as current collider, flavor, and electroweak precision observables. We find that these <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mo stretchy="false">→</mo><mn>3</mn></math> production modes can exceed the conventional pair production rate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mrow><mo>+</mo><mo>+</mo></mrow></msup><msup><mi>H</mi><mrow><mo>−</mo><mo>−</mo></mrow></msup></math>, followed by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup><msup><mi>W</mi><mo>±</mo></msup></math> decays, over wide regions, particularly above the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup><msup><mi>W</mi><mo>±</mo></msup></math> thresholds, reaching cross sections up to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mn>2</mn></msup><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>fb</mi></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>500</mn><mi>–</mi><mn>1500</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. A detector-level analysis of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><mo>ℓ</mo><mo>+</mo><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></math> signature, including dominant multiboson and top quark backgrounds, shows that discovery sensitivity is achievable for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>1000</mn><mi>–</mi><mn>1500</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with integrated luminosities in the few <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>ab</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> range, even in the presence of realistic systematic uncertainties.</p>

Morocco

B. Ait-Ouazghour

France

A. Arhrib

R. Benbrik

Poland

M. Boukidi

M. Chabab

K. Goure

United Kingdom

Sweden

S. Moretti

Probing doubly charged Higgs bosons with three-body associated production at future <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> colliders

In this work, we investigate the structural and physical properties of anisotropic compact stars by incorporating the Einasto dark matter density profile within the <italic>f</italic>( <italic>R, T</italic>) gravity framework. The primary objective is to understand how the interplay between modified gravitational dynamics and dark matter influences the behavior of compact stellar systems. We construct physically viable stellar configurations by solving the modified field equations under appropriate boundary and matching conditions. The resulting models are analyzed using key physical criteria such as regularity, energy conditions, and stability requirements, including the behavior of the anisotropy factor and the adiabatic index. Our analysis, applied to five well-known compact star models, demonstrates that the proposed framework yields consistent and realistic solutions, offering deeper insights into the role of extended gravity theories and dark matter in astrophysical modeling.

India

H. Aruna Kumara

Chaitra Chooda Chalavadi

V. Venkatesha

Influence of the Einasto density profile on anisotropic compact stars in <italic>f</italic>( <italic>R, T</italic>) gravity

In this paper, we would like to investigate whether a generalized Einsteinian cubic gravity, in which three possible cubic interactions $$\mathcal{P}$$ , $$\mathcal{C}$$ , and $$\mathcal{C}'$$ are treated on an equal footing, admits a de Sitter solution as its stable cosmological solution. As a result, we are able to confirm the existence of the corresponding de Sitter solution for this gravity by solving analytically its field equations. Remarkably, only the cubic interaction $$\mathcal{P}$$ gives rise to the existence of the de Sitter solution. Then, we convert the field equations into the corresponding dynamical system for a stability analysis purpose. A fixed point of this dynamical system is found and shown to be equivalent to the obtained de Sitter solution. However, the perturbed dynamical system turns out to be incomplete, leaving undetermined information of the stability of the fixed point (or equivalently the de Sitter solution). Fortunately, we show that this loophole can be cured once the well-known Starobinsky term $$R^2$$ is introduced into the action of the generalized Einsteinian cubic gravity, despite the fact that it contributes nothing to the value of the de Sitter solution.

Vietnam

Tuan Do

Effect of $$R^2$$ on the stability of de Sitter solution of the generalized Einsteinian cubic gravity

A modified gravitational model whose action is given by an arbitrary function of the Ricci scalar, the matter Lagrangian density, a scalar field, and its kinetic term is investigated as an extension of the gravitational sector including an additional dynamical degree of freedom. Within this framework, the causal structure of rotating cosmological solutions is analyzed by considering Gödel and Gödel-type spacetimes as background geometries used as theoretical probes of the model consistency. Different matter sources are examined, including a perfect fluid and scalar-field configurations. It is found that the standard Gödel metric is not compatible with the scalar sector of the theory unless the model reduces to the General Relativity limit. In contrast, Gödel-type geometries admit a wider class of solutions whose causal properties depend on the model parameters and on the matter content. In particular, perfect-fluid sources may lead to either causal or noncausal configurations, whereas scalar-field configurations constrain the geometry to the causal limit, preventing the formation of closed timelike curves, highlighting that the scalar field plays a nontrivial dynamical role distinct from that of a cosmological constant.

Brazil

L. Evangelista

M. Silva

J. Moretti

A. Santos

Causality and its violation in $$f(R,\mathcal {L}_m,\phi ,g^{\mu \nu }\nabla _\mu \phi \nabla _\nu \phi )$$ gravity

In this paper we consider the localization of the gravitino field on a codimension-one thick brane within the framework of $\textit{f}$($\textit{R}$, $\textit{Q}$, $\textit{P}$) gravity. First, setting $$F(\phi ) = \phi $$ , we derive the potential functions for various parameters. Under appropriate coupling parameters, we can find the localized zero mode and some resonance states. Furthermore, we use these resonance states as initial data to investigate the evolution of the gravitino resonances. It can be observed that various parameters on the brane affect the evolution duration. We focus on comparing the localization behavior of the gravitino field on the brane for the cases with $$k=0$$ and $$k\ne 0$$ .

Xiang-Nan Zhou

Miao Wang

Zhi-Chao Duan

Localization of gravitino field on $\textit{f}$($\textit{R}$, $\textit{Q}$, $\textit{P}$) brane