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.

China

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)

In this work, we investigate the internal structure and physical features of compact stars in the background of modified gravity, specifically within <italic>f</italic>( <italic>R, G</italic>) gravity, where <italic>R</italic> represents the Ricci scalar and <italic>G</italic> denotes the Gauss&#8211;Bonnet invariant. The interior spacetime of the stellar configuration is described by the Kohler&#8211;Chao metric, which provides a suitable geometric representation for dense compact objects. Our analysis considers ten well-known compact star candidates, namely Her X-1, SAX J1808.4-3658, SMC X-1, LMC X-4, Cen X-3, 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, and PSR J1614-2230. To incorporate higher-curvature effects, the functional form of <italic>f</italic>( <italic>R, G</italic>) is decomposed into two independent contributions, <italic>f</italic> <inf>1</inf>( <italic>R</italic>) and <italic>f</italic> <inf>2</inf>( <italic>G</italic>), representing the Ricci scalar and Gauss&#8211;Bonnet sectors, respectively. For the <italic>R</italic>-dependent part, we adopt the Hu&#8211;Sawicki type model, while three different models, namely logarithmic and power-law models, are considered for the Gauss&#8211;Bonnet contribution. This reconstruction gives three distinct modified gravity models used to study the different features of compact stellar configurations. Using these models, we study the physical viability of the stellar structures by examining anisotropic pressure content, equilibrium scenario through the Tolman&#8211;Oppenheimer&#8211;Volkoff equation, energy conditions, and stability conditions. The obtained results demonstrate that the energy density, radial pressure, tangential pressure, and anisotropy remain well-behaved throughout the stellar interior for all considered stars. The analysis indicates that the proposed <italic>f</italic>( <italic>R, G</italic>) models together with the Kohler&#8211;Chao interior solution provide physically consistent and stable configurations for compact stars within the modified gravity framework.

Saudi Arabia

Ahdab K. Althukair

Azerbaijan

Pakistan

M. Ilyas

Greece

Russia

Euaggelos E. Zotos

Kohler-Chao interior solutions for compact stellar objects in <italic>f</italic>( <italic>R, G</italic>) gravity

We study the holographic realization of the SO(6) R-symmetry of $$ \mathcal{N} $$ = 4 super Yang-Mills with unitary gauge group. Focusing on 1/2 BPS states in the [0, $\textit{J}$, 0] representation of SO(6) , it is known that depending on the scaling of $\textit{J}$ with $\textit{N}$, these are best described holographically in terms of gravitational waves ($\textit{J}$ ≪ $\textit{N}$) or D3 brane giant gravitons ($\textit{J}$ ~ $\textit{N}$). These two descriptions are bridged by the dielectric effect, as the D3 giant can be regarded as a puffed-up configuration of gravitational waves. The natural non-BPS branes for symmetry operators are either 4-branes or non-BPS Kaluza-Klein monopoles. We show that the former can be regarded as a dielectric expansion of the latter, in parallel to the charged operators. We also propose symTh and symTFT candidates for the SO(6) symmetry, whose operators at the boundary must correspond to the non-BPS branes.

Spain

Francesco Mignosa

Diego Rodriguez-Gomez

Non-Abelian R-symmetry and dielectric branes

We assess the impact of measuring deeply virtual Compton scattering (DVCS) off protons using the planned detector at the Electron-Ion Collider in China (EicC), which is proposed as an upgrade to the High Intensity Heavy-Ion Accelerator Facility (HIAF). We develop a neural-network architecture to flexibly parameterize Compton form factors (CFFs), reliably extrapolate into unmeasured kinematic regions, and provide robust uncertainty estimates using the replica method. The framework is fitted to available worldwide DVCS data using the $ {\mathrm{Gepard}}$ software. We find a significant reduction in the uncertainties of all CFFs after incorporating pseudo-data from single and double polarization asymmetries at the EicC, with particularly strong improvements in the sea-quark region.

Yuan-Yuan Huang

Xu Cao

Taifu Feng

Croatia

Krešimir Kumerički

Yu Lu

Assessing the impact of the Electron-Ion Collider in China on deeply virtual Compton scattering * Supported by the National Key R&D Program of China (2023YFA1606703), the National Natural Science Foundation of China (12547111, 12235008, 12405105) and (PK.1.1.10.0004) co-financed by the European Union and through the European Regional Development Fund - Competitiveness and Cohesion Programme 2021-2027. TF also thanks the Hebei Natural Science Foundation (A2022201017, A2023201041) and Natural Science Foundation of Guangxi Autonomous Region (2022GXNSFDA035068)

<p>We make use of the improved K-matrix algorithm to obtain unitarized amplitudes in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi><mo>+</mo><mi>α</mi><msup><mi>R</mi><mn>2</mn></msup></math> gravity (the so-called Starobinsky model, of cosmological relevance). The procedure is of some complexity because infrared divergences are present and need to be properly regulated. We focus on the behavior of a bona fide scalar resonance, known to exist in this model, and compare it to an apparent resonance detected in previous studies, thus confirming that the latter seems to be an artifact due to the introduction of the infrared regulator. We analyze the existence of other dynamical resonances and dwell on the amplitudes made unitary by this procedure.</p>

Iñigo Asiáin

Antonio Dobado

Domènec Espriu

Unitarization of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi><mo>+</mo><mi>α</mi><msup><mi>R</mi><mn>2</mn></msup></math> gravity

The non-conservation of the energy-momentum tensor in $\textit{f}$($\textit{R}$, $\textit{T}$) gravity can be interpreted as an effective manifestation of dissipation. Motivated by this, we propose a new formulation of $\textit{f}$($\textit{R}$, $\textit{T}$) gravity based on the Herglotz variational principle, which extends the usual Hamilton variational principle to dissipative systems by allowing the Lagrangian to depend explicitly on the action. The resulting gravitational field equations extend those of $\textit{f}$($\textit{R}$, $\textit{T}$) gravity by including Herglotz contributions. In the Newtonian limit, these contributions modify the gravitational potential, allowing us to constrain the Herglotz vector through Mercury’s perihelion precession and the relativistic light deflection. The Herglotz corrections lead to a scaling law consistent with observations from the Cassini spacecraft. Examining two representative cosmological models, the Herglotz vector effectively reduces to a single function that, under suitable conditions, can play the role of a cosmological constant, providing an alternative mechanism for the Universe’s accelerated expansion. Within the Herglotz variational approach, the linear $$f(R,T)=R+\alpha T$$ model, previously ruled out in the standard formulation due to its fixed deceleration parameter, becomes consistent with observations for a certain choice of the Herglotz vector.

Romania

Marek Wazny

Lehel Csillag

Portugal

Miguel Pinto

Tiberiu Harko

Herglotz-type $\textit{f}$($\textit{R}$, $\textit{T}$) gravity

<p>I present a calculation of the ratio <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mfrac><msub><mi>σ</mi><mi>r</mi></msub><msub><mi>F</mi><mn>2</mn></msub></mfrac><mrow><mo>(</mo><mi>x</mi><mo>,</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>)</mo></mrow></mrow></math> in a momentum-space approach using the Block-Durand-Ha parametrization of the proton structure function <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>F</mi><mn>2</mn></msub><mrow><mo>(</mo><mi>x</mi><mo>,</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>)</mo></mrow></mrow></math>. The results are compared with the H1 data and extended to high inelasticity. I also examine the ratio <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mfrac><msub><mi>σ</mi><mi>r</mi></msub><msub><mi>F</mi><mn>2</mn></msub></mfrac><mrow><mo>(</mo><mfrac><msup><mi>Q</mi><mn>2</mn></msup><mi>s</mi></mfrac><mo>,</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>)</mo></mrow></mrow></math> obtained at a fixed <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mi>s</mi></msqrt></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math> to the minimum value of <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi></math> given by <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>Q</mi><mn>2</mn></msup><mo>/</mo><mi>s</mi></mrow></math>, comparing them with both the HERA data and the color dipole model bounds. These results and comparisons with HERA data demonstrate that the suggested method for the ratio <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><msub><mi>σ</mi><mi>r</mi></msub><msub><mi>F</mi><mn>2</mn></msub></mfrac></math> can be applied in analyses of the CERN Large Hadron Collider and Future Circular Collider projects. The effect of adding a simple higher twist term of the form <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>F</mi><mn>2</mn></msub><mo>*</mo><msub><mi>H</mi><mn>2</mn></msub><mo>/</mo><msup><mi>Q</mi><mn>2</mn></msup></mrow></math> to the description of the ratio <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mfrac><msub><mi>σ</mi><mi>r</mi></msub><msub><mi>F</mi><mn>2</mn></msub></mfrac><mrow><mo>(</mo><mfrac><msup><mi>Q</mi><mn>2</mn></msup><mi>s</mi></mfrac><mo>,</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>)</mo></mrow></mrow></math> at low-<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi></math> and low-<math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math> values for comparison with the color dipole bounds and the HERA data is investigated.</p>

Iran

G.R. Boroun

Investigation of the ratio <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mfrac><msub><mi>σ</mi><mi>r</mi></msub><msub><mi>F</mi><mn>2</mn></msub></mfrac><mrow><mo>(</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>/</mo><mi>s</mi><mo>,</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>)</mo></mrow></mrow></math> in the momentum-space approach

We explore black hole solutions in the context of Born-Infeld- <italic>f</italic>( <italic>R</italic>) gravity, a modified gravitational framework that extends both Born-Infeld and <italic>f</italic>( <italic>R</italic>) theories. By adopting a static, spherically symmetric spacetime ansatz, we derive an exact black hole solution and investigate its geometrical structure. We proceed to analyze the thermodynamic properties of the solution, including the Hawking temperature, entropy, and specific heat, with particular emphasis on their dependence on the model parameters. Our results reveal novel thermodynamic behavior that deviates significantly from the standard predictions of general relativity. A comparative study with the Schwarzschild-AdS black holes is also presented, showing how Born-Infeld- <italic>f</italic>( <italic>R</italic>) corrections alter black hole thermodynamics.

Türkiye

Salih Kibaroğlu

Born–Infeld- <italic>f</italic>( <italic>R</italic>) black holes

The ACT data have severely constrained the single scalar field models. Known models of inflation, like the Starobinsky model, the Higgs model and the <italic>a</italic>-attractors are at least 2 <italic>&#963;</italic> off the ACT data. In this work we aim to provide a top-to-bottom approach in single scalar field inflationary cosmology compatible with the ACT data. Specifically, inspired by the fact that the Starobinsky model, the Higgs model and the <italic>a</italic>-attractors, all being plateau potentials, result to the same attractor relation between the spectral index of scalar perturbations and the tensor-to-scalar ratio, which is of the form <math altimg='si7.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo linebreak='goodbreak'>&#8722;</mo><mi>&#945;</mi><msup><mi>r</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math>, in this work we seek for attractors of the form <math altimg='si8.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>f</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></math> that may lead to ACT-compatible inflation. Specifically, we fix the function <italic>f</italic>( <italic>r</italic>) to have a specific desirable form and then solve the differential equation <math altimg='si8.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>f</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></math> to find the potential which results to the relation <math altimg='si8.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>f</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></math>. We discovered analytically three classes of potentials which are variants of the general form <math altimg='si9.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>&#947;</mi><mo>&#177;</mo><mi>&#946;</mi><mi>r</mi><mo>&#177;</mo><msup><mi>r</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math> and all these models are found to be compatible with the ACT data.

V.K. Oikonomou

General scalar field inflation ACT attractors: Utilizing the <italic>n<inf>s</inf></italic>( <italic>r</italic>) relation

We systematically investigate the quasinormal modes of thick branes in $\textit{f}$($\textit{R}$) gravity by numerically solving the Schrödinger-like perturbation equation of gravitational perturbations. To ensure reliability of the results, we employ three complementary methods: the asymptotic iteration method, direct integration of the wave equation, and time-domain numerical evolution. We analyze how model parameters influence the shape of the effective potential of gravitational perturbations and find that the structure of the potential barrier plays a significant role in shaping the quasinormal frequency spectrum. The results obtained from the three methods exhibit strong consistency, thereby ensuring the reliability of the calculations. In particular, real parts of the quasinormal frequencies exhibit an approximately arithmetic progression, suggesting that quasi-localized states can be understood as resonances between the barriers.

Yu-Peng E.

Chun-Chun Zhu

Yu-Xiao Liu

Quasinormal modes of thick branes in $\textit{f}$($\textit{R}$) gravity