High-precision regression of physical parameters from black hole images generated by General Relativistic Ray Tracing (GRRT) is essential for investigating spacetime curvature and advancing black hole astrophysics. However, owing to limitations in observational resolution, high observational costs, and imbalanced distributions of positive and negative samples, black hole images often suffer from data scarcity, sparse parameter spaces, and complex structural characteristics. These factors pose significant challenges to conventional regression methods based on simplified physical models. To overcome these challenges, this study introduces the Multiscale Adaptive Network (MANet), a novel regression framework grounded in deep learning. MANet integrates an Adaptive Channel Attention (ACA) module to selectively enhance features in physically informative regions. Meanwhile, a Multiscale Enhancement Feature Pyramid (MEFP) is employed to capture fine-grained spatial structures, such as photon rings and accretion disks, while alleviating information loss due to downsampling. Experimental evaluations on GRRT-simulated datasets demonstrate that MANet substantially improves parameter estimation accuracy and generalization capability in high-dimensional parameter spaces, outperforming existing baseline approaches. This framework presents a promising avenue for high-precision parameter regression in Event Horizon Telescope (EHT) data analysis and broader astrophysical imaging applications characterized by sparse and noisy data.

China

Jialei Wei

Ao Liu

Dejiang Li

Cuihong Wen

Physical parameter regression from black hole images using a multiscale adaptive neural network * Supported by the Natural Science Foundation of Hunan Province under grant No. 2023JJ30384; the National Natural Science Foundation of China under Grants No. 12374408; the University Students' Innovation and Entrepreneurship Training Program Project

Wilson line operators in the rank $\textit{k}$ totally symmetric tensor representation of $$\mathcal{N}=4 \text{U}(N)$$ sypersymmetric Yang-Mills theories are expected to be realized as D3-branes expanded in $\textit{AdS}$ . Although there is a mismatch between the corresponding line operator indices even in the large $\textit{N}$ and large $\textit{k}$ limit, it is possible to calculate the finite $\textit{k}$ correction on the AdS side as the contribution from D1-branes. We analyze D1-brane fluctuation modes and calculate the leading finite $\textit{k}$ correction to the line operator index on the AdS side.

Japan

Yosuke Imamura

Akihiro Sei

D1-brane correction to a line operator index

We employ the Poincaré section, fast Lyapunov indicator, recurrence analysis, bifurcation diagram and basins of attraction to investigate the dynamical behaviors of the motion of particles around a new dyonic Kerr–Newman black hole immersed in the Melvin-swirling universe presented in (Di Pinto et al. in J High Energy Phys 06:150, 2025). We note that the swirling parameter $\textit{j}$ and magnetic field strength $\textit{B}$ make the equations of motion for particles nonseparable, and confirm the presence of chaotic behavior in the motion in this dyonic Kerr–Newman–Melvin-swirling spacetime and its sub-cases by removing the conical singularities and removing both the conical singularities and the Dirac strings. We observe that both the number of chaotic orbits and the chaotic region increase with the increase of the parameters $\textit{j}$ and $\textit{B}$, but decrease as the electric charge $\textit{Q}$, magnetic charge $\textit{H}$ or spin parameter $\textit{a}$ increases. Moreover, we find that the presence of $\textit{j}$ changes the ranges of $\textit{B}$, $\textit{Q}$, $\textit{H}$ and $\textit{a}$ where the chaotic motion appears for particles. The swirling parameter together with the magnetic field strength, electric charge, magnetic charge and spin parameter yields richer physics in the motion of particles for the spacetime of a dyonic Kerr–Newman black hole immersed in the Melvin-swirling universe.

Deshui Cao

Lina Zhang

Songbai Chen

Qiyuan Pan

Jiliang Jing

Chaotic motion of particles around a dyonic Kerr–Newman black hole immersed in the Melvin-swirling universe

We demonstrate that a pseudo-Nambu-Goldstone boson (pNGB) with an initial misalignment angle can drive successful spontaneous baryogenesis and serve as a dark matter (DM) candidate, provided the corresponding global symmetry is nonrestored at high temperature. A key feature of this mechanism is the presence of a slowly sliding phase in the pNGB’s motion, during which it traverses rapidly diminishing potential barriers, generating and freezing the baryon asymmetry, while transitioning into the kination phase and then an oscillatory phase. Just before the would-be oscillation temperature, parametric resonance effectively fragments the homogeneous mode into fluctuations that ultimately constitute the final DM abundance. By considering a dimension-five explicit breaking operator, we find that the predicted pNGB mass and decay constant are approximately 5 eV and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, respectively, while the radial mode has a light mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> and a small mixing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo stretchy="false">)</mo></math> with the Higgs boson. Applied to the Majoron in the type-I seesaw model, this scenario requires the heaviest right-handed neutrino to be as light as 0.1 to 100 GeV. These predictions can be tested through kaon experiments, heavy neutral lepton searches, the LHC, and future colliders.

South Korea

Eung Jin Chun

Suruj Jyoti Das

Minxi He

Tae Hyun Jung

Jin Sun

Cogenesis by a sliding pseudo-Nambu-Goldstone boson with symmetry nonrestoration

Inspired by the experimental discoveries of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover><mi>q</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math>) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mrow><mi>c</mi><mi>c</mi></mrow></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover><mi>c</mi><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover></math>), we systematically study their orbitally excited strange partners, i.e., the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><msub><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>q</mi><mover accent="true"><mi>s</mi><mo stretchy="false">¯</mo></mover><mi>s</mi><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover></math>) system, which may be related to the recently observed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1855</mn><mo stretchy="false">)</mo></math>, and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><msub><mi>K</mi><mn>1</mn></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>q</mi><mover accent="true"><mi>s</mi><mo stretchy="false">¯</mo></mover><mi>q</mi><mover accent="true"><mi>s</mi><mo stretchy="false">¯</mo></mover></math>) system. Within the framework of an accurate few-body calculation method, we employ the chiral quark model to investigate both the molecular and diquark structures of these two multiquark systems in addition to channel coupling effects. Our results show that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><msub><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub></math> system remains a scattering state, although we have considered two different sets of parameters in our calculations to avoid the influence of parameters. On the other hand, due to the presence of a good-diquark structure in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><msub><mi>K</mi><mn>1</mn></msub></math> system, we obtain a very shallow bound state in the coupled-channel calculation, where the one-gluon, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi></math>-meson, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mn>0</mn></msub></math>-meson, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>σ</mi></math>-meson exchanges play crucial roles. The interquark distance and component analysis also suggest that it is a loosely bound molecular state.

Yue Tan

Yu-Heng Wu

Qi Huang

Xiaoyun Chen

Xiaohuang Hu

Youchang Yang

Jialun Ping

Absence of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1855</mn><mo stretchy="false">)</mo></math> and its exotic partner candidate in a chiral quark model

We investigate the dynamics of neutral spinning test particles in the charged black-bounce spacetime described by the Reissner–Nordström–Simpson–Visser metric, which interpolates between a Reissner–Nordström black hole and a traversable wormhole via the Simpson–Visser parameter $\textit{l}$. Utilizing the Mathisson–Papapetrou–Dixon equations with the Tulczyjew spin-supplementary condition, we derive the equations of motion, effective potential, and conserved quantities for particles in the equatorial plane. The spin-curvature coupling introduces significant deviations from geodesic motion, affecting stable circular orbits and the innermost stable circular orbit. We analyze the superluminal bound, ensuring physically valid timelike trajectories, and find that the spin parameter $\textit{s}$, electric charge $\textit{Q}$, and $\textit{l}$ critically influence orbital stability and dynamics. Additionally, we study particle collisions, computing the critical angular momentum and center-of-mass energy, which reveal conditions for high-energy astrophysical processes, particularly in the black hole regime. Numerical results highlight the interplay between spin, electromagnetic effects, and the black-bounce geometry, with implications for accretion disks and gravitational wave signatures.

Uzbekistan

Shokhzod Jumaniyozov

Javlon Rayimbaev

Yunus Turaev

Dynamics of spinning particles around a charged black-bounce spacetime

We present a comprehensive tensor network study of staggered, Wilson, and twisted mass fermions in the Hamiltonian formulation, using the massive two-flavor Schwinger model as a benchmark. Particular emphasis is placed on twisted mass fermions, whose properties in this context have not been systematically explored before. We confirm the expected <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mi>a</mi><mo stretchy="false">)</mo></math> improvement in the free theory and observe that this improvement persists in the interacting case. By leveraging an electric-field-based method for mass renormalization, we reliably tune to maximal twist and establish the method’s applicability in the two-flavor model. Once mass renormalization is included, the pion mass exhibits rapid convergence to the continuum limit. Finite-volume effects are addressed using two complementary approaches: dispersion relation fits and finite-volume scaling. Our results show excellent agreement with semiclassical predictions and reveal a milder volume dependence for twisted mass fermions compared to staggered and Wilson discretizations. In addition, we observe clear isospin-breaking effects, suggesting intriguing parallels with lattice QCD. These findings highlight the advantages of twisted mass fermions for Hamiltonian simulations and motivate their further exploration—particularly in view of future applications to higher-dimensional lattice gauge theories.

Germany

Tim Schwägerl

Cyprus

Karl Jansen

Stefan Kühn

Fermion discretization effects in the two-flavor lattice Schwinger model: A study with matrix product states

We study a dark energy model composed of a bare negative cosmological constant and a single ultralight axion, motivated by the string axiverse. Assuming that intelligent observers arise and observe, as in our Universe, the onset of dark-energy-driven acceleration following matter domination, and that this acceleration persists to the present, we derive nontrivial constraints on both the axion mass and the bare cosmological constant. The axion mass is bounded from above to avoid fine-tuning of the initial misalignment angle near the hilltop, and from below because too light axions cannot achieve accelerated expansion due to their limited energy budget. As a result, the anthropically allowed axion mass range typically lies around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>m</mi><mo>=</mo><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo><msub><mi>H</mi><mn>0</mn></msub></math> for a decay constant close to the Planck scale, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>H</mi><mn>0</mn></msub></math> is the observed value of the Hubble constant. In this framework, the dark energy equation-of-state parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>w</mi><mn>0</mn></msub></math> generically deviates from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>−</mo><mn>1</mn></math> by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>0.1</mn><mo stretchy="false">)</mo></math>, providing a natural explanation for why <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>w</mi><mo>≠</mo><mo>−</mo><mn>1</mn></math> may be expected. We also find that, for a decay constant slightly smaller than the Planck scale, the peak value of dark energy density is significantly smaller than the anthropic bound on the cosmological constant and can be close to the observed value. These outcomes are intriguingly consistent with recent DESI hints of time-varying dark energy, and offer a compelling anthropic explanation within the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi><mo>+</mo></math> axion framework.

Kai Murai

Fuminobu Takahashi

Anthropic selection in a model with negative <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi></math> plus axion dark energy

The directed flow ( $$v_1$$ ) of charged hadrons ( $$h^{\pm }$$ ) in symmetric collision systems (O + O, Cu + Cu, Zr + Zr, Ru + Ru, Au + Au, and U + U) at $$\sqrt{s_{\textrm{NN}}} =$$ 200 GeV using string-melting version of A Multiphase Transport (AMPT-SM) model is reported. The $$v_1$$ as a function of pseudo-rapidity ( $$\eta $$ ) is obtained for transverse momentum ( $$p_{\textrm{T}}$$ ) ranges of 0.2 $$-$$ 2.0 GeV/$\textit{c}$ and 2.0 $$-$$ 5.0 GeV/$\textit{c}$. The dependence of $$v_1$$ -slope ( $$dv_1/d\eta $$ ) at mid-rapidity on $$p_{\textrm{T}}$$ range, collision centrality, and system size are discussed particularly in the context of the hard-soft asymmetry in the flow profiles of produced particles. In the AMPT-SM model, a system size independence of the magnitude of $$dv_1/d\eta $$ between Cu + Cu and Au + Au collisions at low- $$p_\textrm{T}$$ is observed, and this finding is similar to the observation from the STAR experiment at $$\sqrt{s_{\textrm{NN}}} =$$ 200 GeV. In contrast, a strong centrality and system size dependence, with the opposite sign of $$dv_1/d\eta $$ , is found for the high- $$p_{\textrm{T}}$$ charged hadrons. The AMPT-SM model demonstrates a clear violation of the expected scaling of charged hadrons $$(dv_1/d\eta )/A^{1/3}$$ across different colliding systems.

India

Kishora Nayak

Chile

Vipul Bairathi

System size dependence of charged hadrons directed flow at $$\sqrt{s_{NN}}$$ = 200 GeV using a multi-phase transport model

Within the framework of the next-to-minimal supersymmetric (SUSY) extension of the Standard Model (SM) with a local B-L gauge symmetry (N-B-LSSM), we study lepton flavor violating (LFV) $ \tau\rightarrow e M^+ M^- $ decays: $ \tau \rightarrow e \pi^+\pi^- $ , $ \tau \rightarrow e \pi^+K^- $ , and $ \tau \rightarrow e K^+K^- $ . Based on the latest experimental data, the influence of different sensitive parameters on the branching ratios is considered. It can be seen from the numerical analysis that the main sensitive parameters and LFV sources are non-diagonal elements corresponding to the initial and final leptons. This work can provide a basis for discovering the existence of new physics (NP).

Rong-Zhi Sun

Shu-Min Zhao

Shuang Di

Portugal

Xing-Xing Dong

Study of ${\boldsymbol\tau\rightarrow {\boldsymbol e M^+ M^-}}$ decays in N-B-LSSM * Supported by National Natural Science Foundation of China (NNSFC) (12075074), Natural Science Foundation of Hebei Province (A2023201040, A2022201022, A2022201017, A2023201041), Natural Science Foundation of Hebei Education Department (QN2022173), Post-graduate's Innovation Fund Project of Hebei University (HBU2024SS042), the Project of the China Scholarship Council (CSC) (202408130113). X. Dong acknowledges support from Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the projects CFTP FCT Unit (UIDB/00777/2020, UIDP/00777/2020)