This paper presents a high-precision gravitational redshift test using the China Space Station (CSS) Laser Time Transfer (CLT) system. We develop a comprehensive observation equation based on a $$c^{-3}$$ order relativistic model for space-ground clock comparison. While the CSS optical clock system is currently in the orbital debugging phase, our simulation using actual CSS orbit data achieves a gravitational redshift verification precision of $$\mathrm {(1.8\pm 47)}\times {10}^{-7}$$ – approximately one order of magnitude improvement better than previous experiments. Our work represents the first application of laser-based time transfer for gravitational redshift verification at such precision, and the first use of the CSS CLT link for testing this fundamental aspect of General Relativity. Unlike microwave-based methods, our laser approach avoids ionospheric effects and first-order Doppler shifts. Residual analysis identifies tropospheric delay variations and atmospheric turbulence as the primary remaining uncertainty contributors. The achieved precision enables gravitational potential difference measurements with 0.1 m $$^{\textrm{2}}$$ /s $$^{\textrm{2}}$$ precision – offering new capabilities for both fundamental physics investigations and geodetic applications including intercontinental height transfer. This work establishes a new benchmark for high-precision tests of relativistic physics and demonstrates the transformative potential of space-based optical time transfer.

China

Rui Xu

Wenbin Shen

Hok Fok

Pengfei Zhang

Lihong Li

Lei Wang

Kuangchao Wu

An Ning

Youchao Xie

Ziyu Shen

Lingxuan Wang

Yongqi Zhao

Kai Liu

Yuanjin Pan

Formulation of testing gravitational redshift based on Laser Time link between China Space Station and a ground station

<p>Scalars carrying a conserved global charge <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Q</mi></math> can form stable localized field configurations composed of a large number of particles. These nontopological solitons are spherically symmetric and are called Q-balls. While usually analyzed in three spatial dimensions, these solitons can be straightforwardly generalized to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi></math> spatial dimensions. For <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><mo>=</mo><mn>1</mn></math>, we can analytically solve the nonlinear differential equation for an important class of single-field potentials; for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><mo>&gt;</mo><mn>1</mn></math>, we can analytically approximate the solutions in the thin-wall or large Q-ball regime, including the first subleading correction consistently. Since the underlying differential equations have the same form as vacuum-decay bounce solutions, our results find applications there, too.</p>

United States

Dusty Aiello

Julian Heeck

Q-balls across dimensions

We present a rigorous theoretical and observational analysis of the Hybrid <italic>f</italic>( <italic>Q</italic>) class of models by including the late-time modifying 1/ <italic>Q</italic> term. After deriving strict viability conditions from the analytical expansion history, we show that preserving early-universe structure formation dictates that the linear coupling be exactly unity. This fixes the background of the Hybrid model into a geometric degeneracy with &#923;CDM which is confirmed explicitly through MCMC analysis with the latest background-only probes. The physical novelty of this model is manifest in the perturbation sector, where the geometric coupling breaks the background degeneracy and induces a late-time suppression of the effective gravitational constant <italic>G<inf>eff</inf></italic>&#8239;&lt;&#8239; <italic>G<inf>N</inf></italic>. Consequently, the inclusion of RSD data reveals an amplitude compensation mechanism, by which the matching of the signature <italic>f&#963;</italic> <inf>8</inf> of the data causes the clustering amplitude <italic>&#963;</italic> <inf>8</inf> to inflate under weaker gravity. Statistical model comparison through AIC/DIC demonstrates that incorporating growth data yields a moderate to weak preference for the Hybrid model keeping the background cosmology intact. This provides a physically bounded alternative to &#923;CDM with a falsifiable signature in the large scale structure, directly testable by the next generation of galaxy surveys.

India

Ameya Kolhatkar

P.K. Sahoo

Beyond the cosmological constant: Breaking the geometric degeneracy of <italic>f</italic>( <italic>Q</italic>) cosmology via redshift-space distortions

We establish a new PBW basis for <math altimg='si1.svg'><msub><mi mathvariant='script'>A</mi><mi>q</mi></msub></math>, the alternating central extension of the <italic>q</italic>-Onsager algebra. Terwilliger showed that the alternating generators form a PBW basis in the block order <math altimg='si2.svg'><mrow><mi mathvariant='script'>G</mi><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup><mo linebreak='goodbreak'>&lt;</mo><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover></mrow></math>. We prove that they also form a PBW basis in the different block order <math altimg='si3.svg'><mrow><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mo linebreak='goodbreak'>&lt;</mo><mi mathvariant='script'>G</mi><mo linebreak='goodbreak'>&lt;</mo><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup></mrow></math>. Consequently, multiplication induces a vector-space isomorphism <display><formula id='ueq0001'><math altimg='si4.svg'><mrow><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mi>&#8855;</mi><mi mathvariant='script'>G</mi><mi>&#8855;</mi><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover><mi>&#8855;</mi><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup><mo>&#10230;</mo><msub><mi mathvariant='script'>A</mi><mi>q</mi></msub><mo>,</mo></mrow></math></formula></display>thereby confirming a conjecture of Terwilliger.

Singapore

Haoran Zhu

A new PBW basis for the alternating central extension of the <italic>q</italic>-Onsager algebra

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}} $ .

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.

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