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.

China

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)

We ask whether two classical time-machine geometries, the Ori (2005) compact-vacuum-core metric and the Ahmed (2018) four-dimensional generalisation of Misner space, remain admissible exact solutions when the gravitational sector is enlarged to the recently proposed $$f(R,\mathcal {L}_{m},\Phi ,X)$$ class, an extension of $$f(R,\mathcal {L}_{m})$$ that couples curvature, the matter Lagrangian density, a scalar field $$\Phi $$ , and its kinetic invariant $$X = g^{\mu \nu }\nabla _{\mu }\Phi \nabla _{\nu }\Phi $$ . Working with the explicit model $$f = R + \mathcal {L}_{m} + (\lambda /2)\,X$$ and a vanishing scalar potential, we compute the curvature invariants, the modified field equations, and the effective stress-energy components produced by the harmonic scalar profile $$\Phi (x,y) = a(x^{2}-y^{2})/2$$ in both backgrounds. The Ricci scalar vanishes for the Ori metric and obeys $$R = e^{f}(f_{,xx}+f_{,yy})$$ for the Ahmed metric; the kinetic invariant takes the explicit forms $$X = a^{2}(x^{2}+y^{2})$$ and $$X = a^{2}e^{f}(x^{2}+y^{2})$$ , respectively. Both metrics solve the field equations of the modified theory with anisotropic matter sources, and the chronology-violating regions $$g_{zz}<0$$ (Ori) and $$g_{\psi \psi }<0$$ (Ahmed) survive the modification. Energy-density profiles measured by a closed-timelike-curve observer match those measured by a static observer outside the chronology horizon, so the additional scalar degree of freedom in $$f(R,\mathcal {L}_{m},\Phi ,X)$$ gravity does not enforce a chronology-protection mechanism in either background. The conclusion mirrors the parallel result for the Li time-machine and supplies a consistency test for scalar-extended modified gravity in non-globally-hyperbolic settings.

India

Faizuddin Ahmed

Jordan

Ahmad Al-Badawi

Türkiye

İzzet Sakallı

Are Petrov type-N and D spacetimes admitting CTCs valid in $$f(R,\mathcal {L}_m,\Phi ,X)$$ gravity?

In this study, within the framework of <math altimg='si3.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> modified gravity, we investigate the influence of coupling parameter ( <italic>&#955;</italic>), magnetic field and anisotropy parameter on the neutron star structure. This work employs an accurate equation of state (EoS), derived from realistic microscopic calculations based on the AV18 nucleon-nucleon potential, to compute the structure of this compact object. Here, determination of Schwarzschild radius, compactness, gravitational surface redshift and Kretschmann scalar within the <math altimg='si3.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity, confirms that our theoretical results are consistent with the observational constraints. While established physical EoSs within the framework of Einstein gravity have successfully characterized a broad range of compact objects, they remain inadequate in explaining certain massive objects residing within the mass gap ( <math altimg='si82.svg'><mrow><mn>2.5</mn><mo linebreak='goodbreak'>&#8722;</mo><mn>5</mn><msub><mi>M</mi><mo>&#8857;</mo></msub></mrow></math>). We show that some compact objects residing in the mass gap can be interpreted as candidates of neutron stars within the framework of <math altimg='si3.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity. Motivated by the observation of objects within this mass range, we employ a framework that simultaneously incorporates <math altimg='si83.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo><mo>=</mo><mi mathvariant='script'>R</mi><mo linebreak='goodbreak'>+</mo><mn>2</mn><mi>&#955;</mi><mi>T</mi></mrow></math> gravity and Bowers-Liang anisotropy model. Our study concludes that an increase in the star&#8217;s surface magnetic field (which dominates the softening of the EoS) leads to a reduction in the maximum masses and corresponding radii. Furthermore, at a fixed <italic>&#955;</italic>, larger values of the anisotropy parameter <italic>&#946;</italic> result in increased masses and radii. Conversely, for fixed <italic>&#946;</italic>, a decrease in <italic>&#955;</italic> yields an increasing trend in both masses and radii. Finally, we compare our results with the observational data from LIGO/Virgo/KAGRA and NICER, setting the parameters of the <math altimg='si3.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> theory and anisotropy to successfully reproduce the masses and radii of the GW170817, PSR J0952-0607 and PSR J0740+6620 and the masses of the secondary components of GW190814 ( <math altimg='si84.svg'><mrow><msub><mi>m</mi><mn>2</mn></msub><mo linebreak='goodbreak'>=</mo><mn>2</mn><mo>.</mo><msubsup><mn>59</mn><mrow><mo>&#8722;</mo><mn>0.09</mn></mrow><mrow><mo>+</mo><mn>0.08</mn></mrow></msubsup><msub><mi>M</mi><mo>&#8857;</mo></msub></mrow></math>) and GW200210-092254 ( <math altimg='si85.svg'><mrow><msub><mi>m</mi><mn>2</mn></msub><mo linebreak='goodbreak'>=</mo><mn>2</mn><mo>.</mo><msubsup><mn>83</mn><mrow><mo>&#8722;</mo><mn>0.42</mn></mrow><mrow><mo>+</mo><mn>0.47</mn></mrow></msubsup><msub><mi>M</mi><mo>&#8857;</mo></msub></mrow></math>).

Iran

M. Savari

G.H. Bordbar

J. Sedaghat

A. Sheykhi

Structure of anisotropic magnetized neutron stars in <math altimg='si3.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity with realistic equation of state

In a spin-1 hadron, tensor-polarized parton distribution functions (PDFs) exist. The twist-2 function is <italic>f</italic> <inf>1<italic>LL</italic></inf> and a twist-3 one is <italic>f<inf>LT</inf></italic>. Because an experiment is under preparation at the Thomas Jefferson National Accelerator Facility (JLab) to measure the cross section of electron-deuteron deep inelastic scattering with the tensor-polarized deuteron target, these PDFs need to be understood theoretically. Especially, measurements will be done in a relatively low- <italic>Q</italic> <sup>2</sup> region at JLab, so that twist-3 contributions could become sizable in the cross section. In a previous work, a twist-2 relation was derived for <italic>f<inf>LT</inf></italic> in terms of <italic>f</italic> <inf>1<italic>LL</italic></inf> by using a nonlocal operator, and it corresponds to the Wandzura-Wilczek (WW) relation between <italic>g</italic> <inf>1</inf> and <italic>g</italic> <inf>2</inf>. In addition, another relation similar to the Burkhardt-Cottingham (BC) sum rule was obtained. It is known that a formal way to derive the WW relation and the BC sum rule is to use the operator product expansion (OPE) with local operators. In this work, the WW-like relation and the BC-like sum rule for <italic>f<inf>LT</inf></italic> are derived by using the local OPE method as a reliable independent way to establish these relations.

Japan

S. Kumano

Kenshi Kuroki

Twist-2 relations for the twist-3 tensor-polarized distribution function <italic>f<inf>LT</inf></italic> of a spin-1 hadron by the operator-product-expansion method

We investigate the interplay of the Weak Gravity Conjecture (WGC) and the Weak Cosmic Censorship Conjecture (WCCC) in $\textit{F}$($\textit{R}$)-Euler-Heisenberg black holes in Anti-de Sitter and de Sitter backgrounds. The solution is characterized by the electric charge $\textit{q}$, the $\textit{F}$($\textit{R}$) deviation $$ {f}_{R_0} $$ , the Euler-Heisenberg coupling $\textit{λ}$, and the constant scalar curvature $\textit{R}$ . We establish a universal entropy-extremality relation that provides thermodynamic evidence for the WGC independently of $$ {f}_{R_0} $$ and $\textit{R}$ . Photon sphere analysis from both geodesic and topological perspectives confirms the simultaneous compatibility of the WGC and WCCC, with the Euler-Heisenberg coupling restoring photon spheres in the naked singularity regime. Gravitational lensing in the strong- and weak-deflection limits reveals that the photon sphere radius is independent of the cosmological background while the critical impact parameter nearly doubles in de Sitter. Black hole shadow images under isotropic accretion are constructed. Within the Barrow entropy framework, we uncover van der Waals-type phase transitions and analyze Joule-Thomson expansion, identifying the small black hole phase as the WGC-compatible thermodynamic regime accessible via isenthalpic cooling.

Saeed Noori Gashti

Erdem Sucu

Mohammad Alipour

Ankit Anand

Mohammad Afshar

Azerbaijan

Behnam Pourhassan

Jafar Sadeghi

Testing the weak gravity conjecture via gravitational lensing, black hole shadows, and Barrow thermodynamics in F(R)-Euler-Heisenberg (A)dS black holes

In the present work, we studied the $$T_{\bar{c}\bar{s}1}^f(2750)$$ state production through the meson loop mechanism in the $$B^+$$ meson decays, where $$T_{\bar{c}\bar{s}1}^f(2750)$$ is considered as a $$\bar{D}K^*$$ molecular state with $$J^P=1^+$$ . By employing the effective Lagrangian approach, we estimated the branching ratio of the $$B^+ \rightarrow D^+ T_{\bar{c}\bar{s}1}^{f}(2750)$$ and $$B^+ \rightarrow D^{*+} T_{\bar{c}\bar{s}1}^f(2750)$$ processes and found them to be on the order of $$10^{-5}\sim 10^{-4}$$ . The fit fraction of $$T_{\bar{c}\bar{s}1}^f(2750)$$ in different processes was also estimated. We propose to search for $$T_{\bar{c}\bar{s}1}^f(2750)$$ in the $$B^+ \rightarrow D^{*+}\bar{D}^{*-}K^+$$ process, which should be accessible to the Belle II and LHCb Collaborations.

Zhuo Yu

Qi Wu

Zi-Li Yue

Dian-Yong Chen

$$T_{\bar{c}\bar{s}1}^f(2750)$$ production in the $$B^+$$ decays processes

We consider four-derivative superinvariants of five-dimensional $$ \mathcal{N} $$ = 2 supergravity coupled to $\textit{n}$ ≤ 2 vector multiplets, which we obtain from both the superconformal tensor calculus approach and dimensional reduction. For the minimal case, with no vector multiplets, it is known that there is a unique four-derivative superinvariant. However, for the case of one vector multiplet, after field redefinitions, we find that there are three independent superinvariants, one of which is a vector superinvariant that does not contain any curvatures and takes the form of a supersymmetrization of $\textit{F}$ . Similarly, for the two vector multiplet case, corresponding to the STU model, we find three gravitational superinvariants and two $\textit{F}$ -type vector superinvariants. Moreover, we find that these vector superinvariants do not affect the two- and three-charge static BPS black hole solutions. We further consider the rigid limit to $$ \mathcal{N} $$ = 2 super-Yang-Mills and use this to conjecture a family of vector superinvariants for five-dimensional $$ \mathcal{N} $$ = 2 supergravity coupled to an arbitrary number of vector multiplets.

United States

Yide Cai

Sabarenath Jayaprakash

James Liu

Yi Pang

Robert Saskowski

New $\textit{F}$ 4 invariants in five-dimensional supergravity

<p>Recent measurements of charmed-baryon semileptonic decays signal large tensions between experiment and theory, including <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><msub><mo stretchy="false">)</mo><mi>F</mi></msub></math> analyses and lattice-quantum chromodynamics simulations. Possible sources of the discrepancy include the experimental normalization mode <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Ξ</mi><mi>c</mi><mn>0</mn></msubsup><mo stretchy="false">→</mo><msup><mi mathvariant="normal">Ξ</mi><mo>−</mo></msup><msup><mi>π</mi><mo>+</mo></msup></math>. Using lattice-quantum chromodynamics inputs in an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><msub><mo stretchy="false">)</mo><mi>F</mi></msub></math> analysis including first-order symmetry breaking, we predict <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi mathvariant="normal">Ξ</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub><mo stretchy="false">)</mo><mo>/</mo><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi mathvariant="normal">Ξ</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi mathvariant="normal">Ξ</mi><mn>0</mn></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>2.6</mn><mo>±</mo><mn>0.3</mn><mo stretchy="false">)</mo><mo>%</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi mathvariant="normal">Ξ</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><mi mathvariant="normal">Λ</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub><mo stretchy="false">)</mo><mo>/</mo><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi mathvariant="normal">Ξ</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi mathvariant="normal">Ξ</mi><mn>0</mn></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>1.1</mn><mo>±</mo><mn>0.1</mn><mo stretchy="false">)</mo><mo>%</mo></math>, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>+</mo></msup><mo>=</mo><mo stretchy="false">(</mo><msup><mi>e</mi><mo>+</mo></msup><mo>,</mo><msup><mi>μ</mi><mo>+</mo></msup><mo stretchy="false">)</mo></math>. These ratios provide normalization-independent tests and may help clarify the origin of the present tension.</p>

Chao-Qiang Geng

Chia-Wei Liu

Sheng-Lin Liu

Puzzles in charmed baryon semileptonic decays with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><msub><mo stretchy="false">)</mo><mi>F</mi></msub></math> flavor symmetry and lattice inputs

We investigate thick-brane configurations in five-dimensional $$f(T,T_G)$$ modified teleparallel gravity. In five dimensions, the torsional Gauss–Bonnet invariant $$T_G$$ contributes dynamically, leading to genuinely new effects even at linear order. Within a warped geometry supported by a scalar field, we construct explicit solutions and show that the $$T_G$$ sector significantly modifies the brane structure. In particular, the coupling parameter controls the deformation of the warp factor and energy density; for sufficiently negative values it can induce a genuine two-peak internal structure. We further analyze the localization of spin-1/2 fermions via a Yukawa coupling. For odd Yukawa functions the system admits a normalizable chiral zero mode, while the opposite chirality remains delocalized. The massive Kaluza–Klein spectrum is strongly affected by the torsional Gauss–Bonnet term, which modifies the effective potentials and leads to the appearance of resonant quasi-localized states. Our results show that $$f(T,T_G)$$ gravity provides a richer framework for braneworld models, where torsional higher-order corrections play a key role in shaping both geometry and field localization.

Brazil

A. Moreira

F. Belchior

Mexico

Shi-Hai Dong

Greece

Chile

E. Saridakis

Thick branes and fermion localization in five-dimensional $$f(T,T_G)$$ gravity