The internal structure of the light scalar state $ a_0(1450) $ has not been definitively determined; it may comprise multiple possible configurations. Among these, it may be regarded as a $ q\bar{q} $ state. Based on this possibility, we use QCD light-cone sum rules to study the semileptonic decay process $ D \to a_0(1450)\ell \nu_\ell $ with $ \ell=(e, \mu) $ and to test this hypothesis. First, we construct two twist-2 light-cone distribution-amplitude schemes based on the light-cone harmonic-oscillator model, and present their moments $ \langle\xi^{n}\rangle |_{\mu} $ and Gegenbauer moments $ a_{n}(\mu) $ at $ \mu_0=1\; {\rm{GeV}} $ and $ \mu_k= 1.4\; {\rm{GeV}} $ for $ n=(1,3,5) $ . In the large-recoil region, we obtain the transition form factors (TFFs): $ f_+^{({\rm{S}}1)}(0) = $ $ 0.836_{-0.119}^{+0.116} $ , $ f_+^{({\rm{S}}2)}(0)=0.767_{-0.105}^{+0.106} $ , and $ f_-(0)=0.630_{-0.077}^{+0.078} $ . A simplified series expansion $ z(q^2, t) $ is used to extrapolate the TFFs to the entire physical $ q^2 $ region. For $ q^2=10^{-5} \; {\rm{GeV}}^2 $ , we compute the angular distribution of the differential decay width ${{\rm d}\Gamma}/{{\rm d}\cos\theta_\ell }$ over the range $ \cos\theta_\ell \in [-1,1] $ . Subsequently, we obtain the differential decay widths and branching fractions for $ D^0 \to a_0(1450)^- \ell^+ \nu_\ell $ and $ D^- \to a_0(1450)^0 \ell^- \bar{\nu}_\ell $ , with branching fractions of order $ 10^{-6} $ . Finally, we analyze three angular observables for the semileptonic decay process $ D^- \to a_0(1450)^0 \ell^- \bar{\nu}_\ell $ : the forward–backward asymmetry $ {\cal{A}}_{\rm{FB}} $ , the lepton polarization asymmetry $ {\cal{A}}_{\lambda_\ell} $ , and the $ q^2 $ -differential flat term $ {\cal{F}}_{\rm{H}} $ .

China

Ya-Lin Song

Yin-Long Yang

Ye Cao

Xue Zheng

Hai-Bing Fu

Searching the possibility of $\textit{a}$ $_{0}$(1450) scalar state being a q q state structure via charmed meson semileptonic decays * Supported in part by the National Natural Science Foundation of China (12265010), and the Guizhou Provincial Department of Science and Technology (MS[2025]219, CXTD[2025]030)

In this work, we investigate neutron stars (NSs) in the strong field regime within the framework of symmetric teleparallel $\textit{f}$($\textit{Q}$) gravity, considering three representative models: linear, logarithmic, and exponential. While Bayesian studies of NS observations are well established in general relativity and curvature based modified gravity theories, such analyses in $\textit{f}$($\textit{Q}$) gravity remain largely unexplored. For the first time we perform a Bayesian inference analysis by confronting theoretical NS mass-radius predictions with NICER observations of PSR J0030+0451, PSR J0740+6620, PSR J0437+4715, and PSR J0614+3329 in the background of nonmetricity based gravity. The dense matter equation of state is fixed to DDME2 in order to isolate the effects of modified gravity on NS structure. Our results indicate a statistical preference for the exponential $\textit{f}$($\textit{Q}$) model over the linear and logarithmic cases, as supported by the Bayes-factor analysis, and show that its parameters are comparatively well constrained. For this model, we obtain a radius and tidal deformability at $$1.4\,M_\odot $$ of $$R_{1.4} = 11.27^{+0.53}_{-0.36}\,\textrm{km}$$ and $$\varLambda _{1.4} = 156.95^{+84.02}_{-41.73}$$ , respectively, consistent with current observational constraints. The median values of the maximum mass are found to be around $$M_{\max }\approx 2.3M_\odot $$ for all three constrained models. However, the upper parts of the 95% credible regions of the mass-radius relations extend beyond $$2.5M_\odot $$ and approach $$\sim 3M_\odot $$ within the adopted framework. This indicates the possibility of comparatively massive stable compact configurations in the Bayesian constrained parameter space. These results highlight the potential of NSs as powerful probes of symmetric teleparallel gravity in the strong field regime. We note that these results are conditional on the use of a fixed DDME2 equation of state and the coincident-gauge formulation adopted in this work.

India

Sneha Pradhan

N. Patra

Kai Zhou

P. Sahoo

Bayesian inference of neutron star properties in $\textit{f}$($\textit{Q}$) gravity using NICER observations

While $\textit{CP}$ models with analytic potentials are known to support finite-energy compact Q-ball and Q-shell solutions, their behavior in more complex Lagrangian frameworks remains a subject of active research. This work explores these non-topological structures within an extended Skyrme-Faddeev-type model that incorporates quartic derivative terms. In this context, harmonic time dependence and the presence of quartic terms constitute two independent stabilization mechanisms that allow the configurations to circumvent Derrick’s scaling argument. We investigate the necessary conditions for the existence of these solutions and analyze the influence of quartic terms on the resulting compactons. Specifically, we examine the scaling relationship between energy and Noether charge, expressed as $\textit{E}$($\textit{Q}$) ~ |$\textit{Q}$| . Our numerical analysis demonstrates that $\textit{n}$ < 1, which supports the stability of these solutions against spontaneous fission.

Brazil

E. Colaço

P. Klimas

Poland

L. Livramento

Japan

N. Sawado

S. Yanai

Compact Q-balls and Q-shells within a $\textit{CP}$ $\textit{N}$ Skyrme-Faddeev type model

We employ the island formula to investigate the entanglement entropy of the Hawking radiation in an asymptotically AdS black hole background within the framework of <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> gravity. Through an analysis based on the Euclidean action, we find that the area term of the generalized entropy must be modified, which in turn leads to a modification of the island formula. Using the modified formula to compute the radiation entropy for an eternal asymptotically AdS black hole reveals that, the result diverges as the cutoff surface is moved outward, indicating the breakdown of the <italic>s</italic>-wave approximation. A possible reason is that we have neglected the gravitational back-reaction. For a collapsing asymptotically AdS black hole, the radiation entropy is dominated by the area term, with a correction proportional to the logarithm of the event horizon area, which is consistent with the predictions of quantum gravity. Both the radiation entropy and the Page time are ultimately influenced by the choice of the <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> model, implying that the information regarding the underlying gravitational model is encoded in the final radiation.

Yipeng Liu

Wei Xu

Baocheng Zhang

Radiation entropy in asymptotically AdS black holes within <math altimg='si1.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> gravity

We develop a unified framework for studying superposed coherent states in coupled nonlinear bosonic systems using a <italic>q</italic>-deformed Kerr oscillator model. A quantitative measure, termed catability, is introduced to quantify robustness and structural coherence of Schr&#246;dinger-cat-like states under nonlinear and deformation effects within the framework. Within the <italic>q</italic>-deformed bosonic algebra, we analyze the dynamics of two coupled Kerr oscillators to demonstrate that the deformation parameter governs coherence redistribution and nonlinear coupling-induced state transformation. Establish local cat states emerge from the relation between Kerr nonlinearity and <italic>q</italic>-deformed interactions, coherence transfer between subsystems becomes sensitive to the deformation strength. In this case, construct a phase diagram of catability, revealing distinct regimes of quantum behavior, identifying coupling-driven quantum phase transitions in a deformed algebraic structure system. The generalized analysis extended the covariant formulation and graphene-inspired catability operators generalized curved space-time backgrounds, establishing a connection between nonlinear quantum optics, condensed matter analog systems, relativistic quantum structures framework. In this context, results explain complete description deformation-controlled quantum coherence and establish new directions for engineered nonclassical states in complex quantum systems.

Algeria

Azerbaijan

Abdelmalek Bouzenada

q-deformed catability in coupled Kerr, graphene, and quantum phase transitions

We investigate the late-time dynamics of cosmic expansion within a torsion-free formulation of <italic>f</italic>( <italic>Q</italic>) gravity in a spatially flat Friedmann-Robertson-Walker universe. Adopting a specific non-metricity model that reduces to standard cosmology at early times, we explore whether accelerated expansion can emerge purely from geometric effects without introducing a cosmological constant. To probe the dynamical behavior of dark energy, three redshift-dependent parameterizations of the equation of state are considered. The resulting cosmological evolution is analyzed through a comprehensive set of diagnostics, including the effective equation of state, deceleration parameter, <italic>O</italic>m diagnostic and higher-order cosmographic quantities such as the jerk, lerk, and time parameter. These indicators consistently reveal a transition from decelerated to accelerated expansion and demonstrate clear deviations from the standard &#923;CDM scenario, highlighting the dynamical nature of the underlying models. Furthermore, the thermodynamical viability of the framework is examined by testing the generalized second law of thermodynamics, Gibbs free energy ( <italic>G</italic>) and heat capacity <italic>C</italic>. The positivity of the total entropy variation throughout the relevant redshift range confirms the thermodynamic consistency of the models. Moreover, the thermodynamical stability of the system is also confirmed by obtaining <italic>C</italic>&#8239;&gt;&#8239;0 and <italic>G</italic>&#8239;&lt;&#8239;0.

Nageen Pervaiz

Pakistan

Nadeem Azhar

Jin-Zeng Li

Kazakhstan

Abdul Jawad

Nurgissa Myrzakulov

Saken Toktarbay

Uzbekistan

Sanjar Shaymatov

Aray Muratkhan

Late-time cosmic acceleration in torsion-free <italic>f</italic>( <italic>Q</italic>) gravity: Dynamical and thermodynamical analysis

In this paper, we put forward and discuss a proposal for a Quantum Spectral Curve (QSC) describing the planar spectrum of the holographic CFT dual to strings on AdS × S × S × S , a theory with global symmetry 𝔡(2$\textit{,}$ 1; $\textit{α}$) . We focus mainly on the case when the radii of the two spheres are the same, i.e. $\textit{α}$ = 1$\textit{/}$2, where the symmetry reduces to 𝔬𝔰𝔭(4|2) . In this case, our proposal is based on two copies of an 𝔬𝔰𝔭(4|2) Q-system, glued through the branch cuts of the Q-functions in a minimal way. We study in detail the ensuing analytic properties of the Q-functions in this proposal. Focusing on purely massive excitations, we consider the large worldsheet limit in which the QSC leads to a set of Asymptotic Bethe Ansatz (ABA) equations, yielding strong constraints on the (so-far unfixed) dressing factors of the worldsheet S-matrix. In a ℤ -symmetric sector, our proposal is consistent with all previous results on the worldsheet S-matrix. However, in the non-symmetric case, we found a subtle incompatibility between the analytic constraints arising from the proposed QSC, the crossing equations present in the literature, and braiding unitarity. We discuss possible explanations for this mismatch: either our minimal QSC proposal does not hold beyond the symmetric sector, or the crossing unitarity equations receive a nontrivial correction that needs to be understood.

Italy

Andrea Cavaglià

Rouven Frassek

Nicolò Primi

Roberto Tateo

On the quantum spectral curve for AdS3 $\textit{×}$ S3 $\textit{×}$ S3 $\textit{×}$ S1 strings and the 𝔡(2$\textit{,}$ 1; $\textit{α}$) Q-system

We study the cosmological dynamics of the quadratic symmetric teleparallel gravity model <math altimg='si8.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>Q</mi><mo linebreak='goodbreak'>+</mo><mi>&#945;</mi><msup><mi>Q</mi><mn>2</mn></msup><mo linebreak='goodbreak'>+</mo><mi>&#946;</mi></mrow></math>, which introduces an <italic>H</italic> <sup>4</sup> correction to the Friedmann equation due to <italic>Q</italic>&#8733; <italic>H</italic> <sup>2</sup>. Using the exact algebraic solution for <italic>H</italic>( <italic>z</italic>), we reconstruct the effective dark-energy sector and compare the background evolution with &#923;CDM using Type Ia supernovae, BAO, and cosmic-chronometer data. At the perturbative level, the model modifies the Poisson equation through a time-dependent effective gravitational coupling <math altimg='si9.svg'><mrow><msub><mi>G</mi><mrow><mi>e</mi><mi>f</mi><mi>f</mi></mrow></msub><mrow><mo>(</mo><mi>z</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>G</mi><msup><mrow><mo stretchy='true'>[</mo><mn>1</mn><mo>+</mo><mstyle scriptlevel='0' displaystyle='false'><mfrac><mn>2</mn><mn>3</mn></mfrac></mstyle><mi>A</mi><msup><mi>E</mi><mn>2</mn></msup><mrow><mo>(</mo><mi>z</mi><mo>)</mo></mrow><mo stretchy='true'>]</mo></mrow><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></math>, where <math altimg='si10.svg'><mrow><mi>A</mi><mo linebreak='goodbreak'>=</mo><mn>18</mn><mi>&#945;</mi><msubsup><mi>H</mi><mrow><mn>0</mn></mrow><mn>2</mn></msubsup></mrow></math>. For <italic>&#945;</italic>&#8239;&gt;&#8239;0 this produces a weakened gravitational interaction, suppressing the linear growth factor <italic>D</italic>( <italic>z</italic>), the growth rate <italic>f</italic>( <italic>z</italic>), and the RSD observable <italic>f&#963;</italic> <inf>8</inf>( <italic>z</italic>). In the nonlinear regime, the reduced gravitational strength increases the spherical-collapse threshold and suppresses the halo mass function, leading to a lower predicted value of <math altimg='si11.svg'><mrow><msub><mi>S</mi><mn>8</mn></msub><mo linebreak='goodbreak'>=</mo><msub><mi>&#963;</mi><mn>8</mn></msub><msqrt><mrow><msub><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mi>m</mi></msub><mo linebreak='badbreak'>/</mo><mn>0.3</mn></mrow></msqrt></mrow></math>. Thus, the quadratic <italic>f</italic>( <italic>Q</italic>) extension can reproduce mild deviations from &#923;CDM at the background level while naturally alleviating the <italic>S</italic> <inf>8</inf> tension, offering a viable modified-gravity explanation for recent observational hints of dynamical dark energy.

Egypt

G.G.L. Nashed

Russia

P.V. Tretyakov

Saudi Arabia

A. Eid

Late-time cosmology and structure formation in quadratic <italic>f</italic>( <italic>Q</italic>) gravity

The common eigenfunctions of the twisted Cherednik operators can be first analyzed in the limit of <math altimg='si3.svg'><mrow><mi>q</mi><mo>&#10230;</mo><mn>1</mn></mrow></math>. Then, the polynomial eigenfunctions form a simple set originating from the symmetric ground state of non-vanishing degree and excitations over it, described by non-symmetric polynomials of higher degrees and enumerated by weak compositions. This pattern is inherited by the full spectrum at <italic>q</italic>&#8239;&#8800;&#8239;1, which can be considered as a deformation. The whole story looks like a typical NP problem: the Cherednik equations are difficult to solve, but easy to check the solution once it is somehow found.

A. Mironov

A. Morozov

A. Popolitov

Twisted Cherednik spectrum as a <italic>q, t</italic>-deformation

We present a generalized phenomenological parameterization of the deceleration parameter $\textit{q}$($\textit{z}$) that incorporates an effective radiative component (ERC) in addition to a localized late-time contribution. The proposed framework extends previous two-parameter $\textit{q}$($\textit{z}$) reconstructions by explicitly regulating the high-redshift behavior while preserving the late-time transition dynamics. We constrain the free parameters $$(h, q_0, z_c, z_e)$$ using late-time observational data from cosmic chronometers (CC), Pantheon+ Type Ia supernovae (SNIa), H galaxies (HIIG), and intermediate-luminosity quasars (QSO). For the full data combination (CC+SNIa+HIIG+QSO), we obtain $$q_0 = -0.25^{+0.04}_{-0.04}$$ and a transition redshift $$z_T \simeq 0.80$$ , indicating a currently accelerating Universe with a transition occurring earlier than in the $$\Lambda $$ CDM model. Within the redshift range probed by the data, the reconstructed $\textit{q}$($\textit{z}$) deviates from the $$\Lambda $$ CDM trend, suggesting a possible reduction of the late-time acceleration. Furthermore, the reconstruction favors a relatively high value of the Hubble parameter, $$h = 0.729 \pm 0.006$$ . The ERC remains weakly constrained by late-time data but ensures a smooth and monotonic evolution of $\textit{q}$($\textit{z}$), $\textit{j}$($\textit{z}$), and $$w_\textrm{eff}(z)$$ across a wide redshift range. Within the observed interval, the model effectively reproduces the late-time behavior of the previous parametrization, while providing a controlled extension toward early epochs. Our results show that current low- and intermediate-redshift data are compatible with a reduced late-time acceleration.

Mexico

Tomás Verdugo

Alberto Hernández-Almada

Miguel García-Aspeitia

Chile

Juan Magaña

Verónica Motta

Reconstructing the cosmic expansion with a generalized q(z) parameterization: a decelerating Universe from late-time constraints