We investigate the frame dependence of distribution functions within the framework of generalized chiral kinetic theory. Based on the derived transformation rules governing the choice of frame, we analytically obtain the global equilibrium solutions in the presence of vorticity and electromagnetic fields. Our results show that, under the assumption of varying electromagnetic fields, these equilibrium solutions can be uniquely determined.

China

Shu-Xiang Ma

Jian-Hua Gao

Frame dependence in generalized chiral kinetic theory * Supported in part by the National Natural Science Foundation of China (12575147, 12321005, 12175123)

Systems containing objects with negative mass (NMOs) are considered. Such a system consists of one object with positive mass and one NMO, where a bound state exists even though the force exerted by the NMO on the object with positive-mass is repulsive. Unlike standard binaries composed of positive-mass objects, the emitted gravitational waves exhibit decreasing frequency and amplitude over time. We propose a model that removes the ghost appearing in the construction of the Ellis–Bronnikov wormhole, a candidate for a NMO. Furthermore, we perform numerical simulations to obtain the optical appearance of such NMOs. The observed luminosity is also compared with the Schwarzschild black hole and with the Simpson–Visser wormhole, revealing clear differences in the photon ring substructure around the central object.

Japan

Shin’ichi Nojiri

Spain

Sergei Odintsov

Brazil

Diego Sáez-Chillón Gómez

Observational signatures of negative mass wormholes through their shadows

We extend the baryo-charmonium picture of pentaquarks – a color-octet $$c\bar{c}$$ core bonded to a color-octet light-quark cloud – to the doubly-strange sector $$c\bar{c} ssq$$ . The mass splittings are set entirely by the light cloud, so the only new inputs are the strange–strange couplings $$J^{ss}$$ , fixed by a second application of the chromomagnetic scaling, and an additive strange-mass increment taken from the observed $$P_c\!\rightarrow \!P_{cs}$$ shift. We obtain two negative-parity triplets, one produced with a kaon and one with an antiproton, the lowest kaon-associated $$\tfrac{1}{2}^{-}$$ state near 4.60 GeV and the antiproton-associated triplet some 120 MeV below. The robust, distinctive prediction is that the upper two kaon-associated states form a near-degenerate doublet, in sharp contrast to the well-separated triplets of the lighter sectors – a sparse, fixed-spacing pattern that sets the scheme apart from the molecular and diquark alternatives. The internal splittings follow without adjustment from the measured $$P_c$$ and $$P_{cs}$$ spectra; the absolute scale relies on the additive strange-mass ansatz, the main assumption of the extrapolation. The predicted masses agree with recent molecular coupled-channel and QCD sum-rule results.

Türkiye

Halil Mutuk

Doubly-strange hidden-charm pentaquarks from the Fermi statistics of the light-quark cloud

The investigation of nonclassical correlations in curved spacetimes offers key insights into the intersection of quantum information theory and gravitational physics. This paper studies two nonlocal correlation measures, non local advantage of quantum coherence (NAQC) and Bell nonlocality (BN) in a $\textit{d}$-dimensional spherically symmetric Einstein–Gauss–Bonnet (EGB) black hole spacetime. We consider two observers (Alice and Rob) initially sharing a maximally entangled Bell state: Alice freely falls into the black hole (inertial Kruskal frame), while Rob accelerates outside the horizon (non-inertial Schwarzschild-like frame). The Unruh–Hawking effect modifies Rob’s field modes, requiring Bogoliubov transformations to relate the two frames. We derive the mixed bipartite density matrix for fermionic fields and analytical expressions for NAQC and BN, which depend on Hawking temperature (itself governed by $$\alpha $$ , $\textit{d}$, and $$r_h$$ ). Our results show both correlations degrade monotonically with increasing Hawking temperature, confirm the NAQC-BN hierarchical relationship persists in EGB spacetime, and highlight higher-curvature corrections’ impact on quantum resources.

Yifei Xu

Yanjun Chen

Qi Xiao

Xiaolong Gong

Nonlocal correlations of fermionic entanglement in the spacetime of Einstein–Gauss–Bonnet black hole

We show that the expressions for the matter Lagrangian $$L_m$$ and the metric variation $$\delta T_{\mu \nu }$$ of a perfect fluid obtained in previous studies appear to be inconsistent with the standard energy-momentum tensor under general conditions. Consequently, a large number of studies in astrophysics and cosmology relying on these expressions may need to be re-examined. By performing a series of straightforward calculations directly on the standard energy-momentum tensor $$T_{\mu \nu } = (\epsilon + P) u_\mu u_\nu - P g_{\mu \nu }$$ together with the particle number conservation condition, we derive an expression for $$\delta T_{\mu \nu }$$ that is independent of the choice of $$L_m$$ . Applying this result to $$f(R,T)$$ gravity, we obtain the exact form of the tensor $$\Theta _{\mu \nu } = g^{\sigma \rho } \frac{\delta T_{\sigma \rho }}{\delta g^{\mu \nu }}$$ , which remains an important yet long-standing controversial quantity. This expression is shown to hold also for radiation, regardless of whether particle number is conserved. A major result is that if the energy-momentum tensor $$T_{\mu \nu }$$ of the Universe consists solely of standard components with EOS $$P = \omega \epsilon $$ where $$\omega = 0$$ , $$1/3$$ , or $$-1$$ (baryonic/cold dark matter, radiation, and the cosmological constant), then $$f(R,T)$$ gravity satisfies the conservation law $$\nabla _\mu T^{\mu \nu } = 0$$ for any function $$f(R,T)$$ . This contrasts with previous studies, which found that the conservation law holds only for a restricted class of $$f(R,T)$$ functions. Applying the same formalism to stellar interiors, we derive a class of functions that preserve the conservation law. We construct a specific $$f(R,T)$$ model that is consistent at both cosmological scales and in high-density objects such as neutron stars. Remarkably, the same parameter set in this model simultaneously alleviates the Hubble tension and reproduces the observed mass-radius (M–R) relation of neutron stars.

Vietnam

Pham Ky

Metric variation of the energy-momentum tensor of a perfect fluid and its applications to cosmology and neutron stars

We show that pre-geometric gravity à la Mac Dowell–Mansouri predicts the topological quantization of the cosmological constant. In this framework, spacetime emerges from the spontaneous breaking of a de Sitter gauge symmetry, and a gravitational $$\theta $$ -term relates the vacuum energy to a periodic topological angle. The discrete periodicity of this angle forces the cosmological constant to take only quantized values, with the observed dark energy density selecting a vacuum labeled by a topological index $$k \sim 10^{120}$$ . We derive Golden Equations linking the cosmological constant, Planck mass, Gauss–Bonnet coupling, Immirzi parameter, and $$\theta $$ -angle, showing that the Immirzi parameter emerges as the ratio of two topological couplings. The pre-geometric Higgs potential is periodic, with minima separated by Planck-scale barriers that exponentially suppress vacuum decay. The de Sitter entropy is itself quantized and equals the topological index, providing a holographic interpretation of the vacuum selection.

Italy

Andrea Addazi

Topological quantization of the vacuum energy from pre-geometric gravity

We investigate the mass and strong decay properties of the $\Omega(2012)$ resonance using QCD sum rules, assuming it to be an $\textit{S}$-wave $\Xi(1530)\bar{K}$ molecular pentaquark state with $I(J^{P})= 0({3}/{2}^{-})$ . A unified interpolating current is constructed, and the two-point and three-point correlation functions are calculated up to dimension-13 and dimension-10 condensate terms in the OPE series, respectively. The negative-parity contribution is isolated by employing parity-projected sum rules. The two-body strong decays into $\Xi^0 K^-$ and $\Xi^- \bar{K}^0$ are studied using the corresponding three-point correlation functions. Our analysis yields a mass of $2.02 \pm 0.12~\mathrm{GeV}$ and a total two-body decay width of $\Gamma = 0.96^{+0.79}_{-0.41}~\mathrm{MeV}$ for the $\Xi(1530)\bar{K}$ molecular state. The ratio of the two-body decay branching fractions is obtained as $\mathcal{R}^{\Xi^- \bar{K}^0}_{\Xi^0 K^-} = 0.85$ . These results are compatible with the experimental data for the $\Omega(2012)$ within uncertainties and support its interpretation as a $\Xi(1530)\bar{K}$ molecular pentaquark state.

Xiang Yu

Jin-Peng Zhang

Xu-Liang Chen

Ding-Kun Lian

Qi-Nan Wang

Wei Chen

Interpretation of Ω(2012) as a Ξ(1530) ${\bar{\boldsymbol K}}$ molecular state * Supported by the National Natural Science Foundation of China (12575153)

We study classical background electric fields and the Schwinger effect in de Sitter space. We show that a constant electric field in de Sitter requires the photon to have a tachyonic mass proportional to the Hubble scale. This has physical implications for the induced Schwinger current that affect its IR behaviour. To study this, we recompute the Schwinger current in de Sitter space for charged fermions and minimally coupled scalars, imposing a physically consistent renormalization condition. We find a $\textit{finite and positive}$ Schwinger current even in the massless limit. This is in contrast to previous calculations in the literature, which found a negative IR divergence. We also obtain the first result for the Schwinger current of a non-minimally coupled scalar, including the conformally coupled case, which we find exhibits behaviour very similar to that of the fermion current. Our results may have physical implications for both magnetogenesis and inflationary dark matter production.

Mar Bastero-Gil

Portugal

Paulo B. Ferraz

António Torres Manso

Slovenia

Lorenzo Ubaldi

Roberto Vega-Morales

Schwinger current in de Sitter space * This work has been partially supported by Junta de Andalucía Projects P21-00199 and A-FQM-472-UGR20 (FEDER funds); SRA (10.13039/501100011033) and ERDF (PID2022-139466NB-C21) (R.V.M.); PID2022-140831NB-I00, funded by MICIU/AEI/10.13039/501100011033 and FEDER, UE (M.B.G., A.T.M.); by FCT CERN (10.54499/2024.00252.CERN) (M.B.G., A.T.M., P.F.); FCT Grant No. SFRH/BD/151475/2021 and 10.54499/SFRH/BD/151475/2021 (P.F.). LU is supported by the Slovenian Research Agency under research core funding No. P1-0035 and by research grants J1-60026 and J1-4389. This article is based upon work from COST Action COSMIC WISPers CA21106, supported by COST (European Cooperation in Science and Technology). R.V.M. thanks the Mainz Institute for Theoretical Physics (MITP) of the Cluster of Excellence PRISMA$^{+}$ (Project ID 390831469) for its hospitality and partial support during the completion of this work

The weak decays of charmonium states such as $ J/\psi $ and $ \psi(2S) $ are instrumental in probing both nonperturbative QCD dynamics and the flavor structure of the Standard Model (SM). The extreme rarity of charmonium weak decays renders them highly sensitive to physics beyond the SM, particularly in channels that are heavily suppressed in the SM, such as flavor-changing neutral-current (FCNC) decays. This review highlights the critical role of the BESIII experiment, which leverages an unprecedented data sample of over $ 10^{10} $ $ J/\psi $ and $ 2.7\times10^{9} $ $ \psi(2S) $ events to achieve leading sensitivity in searches for charmonium weak decays. We present the latest and most stringent upper limits established by BESIII on various semileptonic, nonleptonic, and FCNC charmonium weak decay channels.

Xu-Ze Li

Kai-Xin Fan

Zheng-Yun You

Yu Zhang

Minggang Zhao

Mini-review of charmonium weak decays at BESIII * Supported in part by the National Key R&D Program of China (2023YFA1606000); the National Natural Science Foundation of China (NSFC) (12035009, 12175321, U1932101), and the National College Students' Science and Technology Innovation Project of Sun Yat-sen University

We investigate the direct $\rm CP $ violation in the decay $ D^\pm \to \pi^\pm \pi^+ \pi^- $ incorporating the $ a_0^0(980) $ - $ f_0(980) $ mixing mechanism. The integrated mixing intensities $ \overline \xi_{fa} $ and $ \overline \xi_{af} $ are calculated using meson masses and coupling constants extracted from various theoretical models and experimental data, yielding values of appreciable magnitude. We find that when the invariant mass of the $ \pi^+\pi^- $ pair lies near the $ f_0(980) $ resonance, this isospin-breaking mechanism can enhance the $\rm CP $ asymmetry. The enhancement is particularly pronounced when the $ f_0(980) $ carries a significant $ n\bar{n} $ quark component and the $ f_0(980) $ and $ \sigma(600) $ mixing angle is approximately $ 26^\circ $ . After accounting for non-factorizable effects, we find these corrections tend to partially cancel the leading-order contributions, resulting in a suppression of the $\rm CP $ violations relative to the naive factorization predictions. It is emphasized that the $ a_0^0(980) $ - $ f_0(980) $ mixing mechanism should be taken into account in both theoretical and experimental studies of $\rm CP $ violation in $\textit{B}$ or $\textit{D}$ meson decays.

Shi-Ji Cao

Jing-Juan Qi

Yi-Fan Zhao

Chao Wang

Zhen-Yang Wang

Xin-Heng Guo

Direct CP violation in ${ {\boldsymbol D}^{\bf\pm }\to {\boldsymbol\pi}^{\bf\pm} {\boldsymbol\pi}^{\bf +} {\boldsymbol\pi}^{\bf -}} $ with ${{\boldsymbol a}_{\bf 0}^{\bf 0}{\bf (980)-}{\boldsymbol f}_{\bf 0}{\bf (980)}} $ mixing * Supported by the National Natural Science Foundation of China (12405115, 12105149, 11805153, 12275024), and the High-Level Scientific Research Fund of Ningbo University (GJPY2026032)