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.

China

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)

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.

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

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.

Greece

Azerbaijan

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

We review the recent work by T.F. Dabash, M. Emam, and L. Schöppner (Eur. Phys. J. C 85, 1341, 2025) and identify an essential error in their analysis.

South Africa

Chile

Andronikos Paliathanasis

Comment on: “Symmetry and conserved quantities in $$f\left( R\right) $$ -gravity: Mei vs. Noether approaches”

The <italic>R</italic> 2 and the single-field-like regime of <italic>R</italic> 2-Higgs inflation are disfavored by the observed high spectral index <italic>n<inf>s</inf></italic> from the combined cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements at the &#8239;&#8764;&#8239;2 <italic>&#963;</italic> level. The addition of a dimension-six <italic>R</italic> 3 term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high <italic>n<inf>s</inf></italic> also induces rapid Goldstone and Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed <italic>n<inf>s</inf></italic>.

India

Tanmoy Modak

Echoes of <italic>R</italic> 3 modification and Goldstone preheating in the CMB-BAO landscape

This work investigates the viability of marginally deformed ( <italic>R</italic> 2) inflation within the framework of the swampland program. The analysis focuses on the Further Refined de Sitter Swampland Conjecture (FRDSSC), the Scalar Weak Gravity Conjecture (SWGC), and its strong extension, the Strong Scalar Weak Gravity Conjecture (SSWGC). By confronting theoretical predictions with observational constraints, the study examines how variations in the model parameters influence its consistency with these conjectures. The results indicate that the model remains compatible with the FRDSSC across a broad region of the parameter space and aligns well with current cosmological observations, supporting its viability as an inflationary framework. Moreover, the comparison between the SWGC and SSWGC reveals that the compatibility of the model is highly sensitive to changes in the coupling parameters, with the SSWGC generally allowing a wider range of consistency than the SWGC. This finding suggests that the stronger conjecture encompasses a broader domain of theoretical validity. Overall, the marginally deformed ( <italic>R</italic> 2) inflation model satisfies all considered swampland criteria, reinforcing its theoretical robustness and its potential as a compelling inflationary scenario within the landscape of quantum gravity-compatible models.

Iran

Saeed Noori Gashti

Mohammad Reza Alipour

Canada

Mohammad Ali S. Afshar

Behnam Pourhassan

Jafar Sadeghi

From theory to observation: Swampland conjectures and ACT constraints on marginally deformed <italic>R</italic> 2 inflation

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

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

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