The Schwinger effect, a non-perturbative mechanism for particle production in strong fields, plays a crucial role in understanding quantum vacuum decay and high-energy phenomena, including heavy-ion collisions (HIC). Although holographic quantum chromodynamics (QCD) models have been widely used to study this effect, most treatments assume isotropy or consider only a single type of anisotropy, neglecting the interplay between spatial and magnetic anisotropies that arise in realistic HIC scenarios. A unified framework accounting for both anisotropies is needed to accurately model particle production. We investigate the Schwinger effect in a twice anisotropic holographic QCD model incorporating both spatial and magnetic anisotropies. Using the anti-de Sitter/conformal field theory correspondence, we compute the total potential of a particle-antiparticle pair to quantify how these anisotropies influence pair production. Our results show that the magnetic field (parameterized by $c_B$ and $q_3$ ) enhances the Schwinger effect by lowering and narrowing the potential barrier, while increasing spatial anisotropy (controlled by $\nu$ ) suppresses the process by raising and widening the barrier. These findings demonstrate that magnetic and spatial anisotropies exert competing effects on particle production, emphasizing the necessity of treating both concurrently in holographic models. This work advances the theoretical description of the Schwinger effect in anisotropic environments, with implications for understanding non-equilibrium dynamics in HIC and other strongly coupled systems.

China

Wen-Bin Chang

Defu Hou

Schwinger effect in a twice anisotropic holographic model * Defu Hou's research is supported in part by the National Key Research and Development Program of China (2022YFA1604900). Additionally, Defu Hou receives partial support from the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Wen-Bin Chang is supported by the Ph.D. Research Startup Project at Hubei Minzu University (RZ2500000857)

We compute the phase of the Euclidean gravity partition function on manifolds of the form $\textit{S}$ × $\textit{M}$ . We find that the total phase is equal to the phase in pure gravity on $\textit{S}$ times an extra phase that arises from negative mass squared fields that we obtain when we perform a Kaluza-Klein reduction to $\textit{S}$ . The latter can be matched to the phase expected for physical negative modes seen by a static path observer in $\textit{dS}$ . In the case of $\textit{S}$ × $\textit{S}$ the answer can be interpreted in terms of a computation in the static patch of $\textit{dS}$ or $\textit{dS}$ . We also provide the phase when we have a product of many spheres. We clarify the procedure for determining the precise phase factor. We discuss some aspects of the interpretation of this phase.

United States

Victor Ivo

Juan Maldacena

Zimo Sun

Physical instabilities and the phase of the Euclidean path integral

Guided by the flipping principle, we propose a novel extension of the Standard Model based on a double right-handed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math> gauge symmetry. In this framework, all left-handed fermions are neutral, while right-handed fermions of the third generation carry charges distinct from those of the first two generations. This structure provides an explanation for the observed Standard Model fermion mass hierarchy; the heavy masses of the third generation are generated at tree level, while the lighter masses of the first and second generations arise radiatively at the one-loop level. For the active neutrino sector, the tiny masses are generated through a combination of tree-level and two-loop seesaw mechanisms. Crucially, this approach successfully reproduces the observed neutrino mass hierarchy, with the atmospheric mass-squared difference generated at tree level and the solar neutrino mass squared difference emerging at the two-loop level. These hierarchical patterns stem from the interplay between gauge invariance and a residual parity symmetry that survives the spontaneous breaking of the extended gauge group. The same residual symmetry stabilizes a viable scalar singlet dark matter candidate, which we show can reproduce the observed relic abundance while remaining consistent with current direct detection bounds. After addressing constraints from electroweak precision tests and flavor-changing neutral currents, we explore the discovery prospects for the new neutral bosons at existing and future colliders, including the LEP, LHC, and a future ILC.

Duong Van Loi

A.E. Cárcamo Hernández

N.T. Duy

D.T. Binh

Cao H. Nam

Physical implications of a double right-handed gauge symmetry

In this study, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in the signal while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

Bingxuan Liu

Yuxuan Shen

Yuanshunzi Sui

Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm * Bingxuan Liu is supported by Shenzhen Campus of the Sun Yat-sen University under project 74140-12255011, and by the Young Scientists Fund (C Class) of the National Natural Science Foundation of China (12405122). Both Yuxuan Shen and Yuanshunzi Sui are supported by College Students’ Innovative Entrepreneurial Training Plan Program

We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

We report a search for ultraheavy dark matter (UHDM) with the CDEX-10 experiment at the China Jinping Underground Laboratory. Using a Monte Carlo framework that incorporates Earth shielding effects, we simulated UHDM propagation and energy deposition in p-type point-contact germanium detectors. Analysis of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>205.4</mn><mtext> </mtext><mtext> </mtext><mi>kg</mi><mo>·</mo><mi>day</mi></mrow></math> exposure in the 0.16–4.16 keVee range showed no excess above background. Our results exclude the spin-independent UHDM-nucleon scattering with two cross section scales, with the UHDM mass from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>6</mn></msup></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>11</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, and provide the most stringent constraints with solid-state detectors below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>8</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>.

Y.F. Wang

L.T. Yang

Q. Yue

K.J. Kang

Y.J. Li

H.P. An

Greeshma C.

J.P. Chang

H. Chen

Y.H. Chen

J.P. Cheng

J.Y. Cui

W.H. Dai

Z. Deng

Y.X. Dong

C.H. Fang

H. Gong

Q.J. Guo

T. Guo

X.Y. Guo

L. He

J.R. He

H.X. Huang

T.C. Huang

S. Karmakar

Y.S. Lan

H.B. Li

H.Y. Li

J.M. Li

J. Li

M.C. Li

Q.Y. Li

R.M.J. Li

X.Q. Li

Y.L. Li

Y.F. Liang

B. Liao

F.K. Lin

S.T. Lin

J.X. Liu

R.Z. Liu

S.K. Liu

Y.D. Liu

Y. Liu

Y.Y. Liu

H. Ma

Y.C. Mao

A. Mureed

H. Pan

N.C. Qi

J. Ren

X.C. Ruan

M.B. Shen

H.Y. Shi

M.K. Singh

T.X. Sun

W.L. Sun

C.J. Tang

Y. Tian

H.F. Wan

G.F. Wang

J.Z. Wang

L. Wang

Q. Wang

Y.X. Wang

H.T. Wong

Y.C. Wu

H.Y. Xing

K.Z. Xiong

R. Xu

Y. Xu

T. Xue

Y.L. Yan

N. Yi

C.X. Yu

H.J. Yu

X. Yu

M. Zeng

Z. Zeng

F.S. Zhang

P. Zhang

Z.Y. Zhang

M.G. Zhao

J.F. Zhou

Z.Y. Zhou

J.J. Zhu

Constraints on ultraheavy dark matter from the CDEX-10 experiment at the China Jinping Underground Laboratory

We revisit the renormalization of the gauge coupling in massless QED coupled to a scaleless quadratic theory of gravity. We compare two alternative prescriptions for the running of the electric charge: (i) the conventional <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi></math> running in minimal subtraction, and (ii) a physical running extracted from the logarithmic dependence of amplitudes on a hard scale <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Q</mi><mn>2</mn></msup></math> (e.g., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>p</mi><mn>2</mn></msup></math> or a Mandelstam invariant) after removing IR effects. At one loop, using dimensional regularization with an IR mass regulator <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>m</mi></math>, we compute the photon vacuum polarization. We find a clean separation between UV and soft logarithms: the former is gauge and process independent and fixes the beta function, whereas the latter encodes nonlocal, IR-dominated contributions that may depend on gauge parameters and must not be interpreted as UV running. In the quadratic-gravity sector, the photon self-energy is UV finite—the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>ln</mi><msup><mrow><mi>μ</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math> pieces cancel—leaving only <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ln</mi><mo stretchy="false">(</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>/</mo><msup><mi>m</mi><mn>2</mn></msup><mo stretchy="false">)</mo></math> soft (IR) logs, which do not contribute to the running of the coupling once IR effects are consistently removed. Consequently, quadratic gravity does not modify the one-loop UV coefficient and thus does not alter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>β</mi><mo stretchy="false">(</mo><mi>e</mi><mo stretchy="false">)</mo></math>. Therefore, the physical running coincides with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi></math> running in QED at one loop. Our analysis clarifies how to extract a gauge and process independent running in the presence of gravitational interactions and why soft logs from quadratic gravity should not contribute to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>β</mi><mo stretchy="false">(</mo><mi>e</mi><mo stretchy="false">)</mo></math>.

M. Gomes

A.C. Lehum

A.J. da Silva

Physical running of the electric charge in a dimensionless theory of gravity

We develop a fully consistent anisotropic extension of the Imran class ICG (Isotropic Compact Gravastar) model within general relativity. A geometry-coupled anisotropy is introduced at the exact equation level, ensuring regularity at the center, smooth matching to the exterior Schwarzschild spacetime, and the absence of thin shells. A controlled option enforces vanishing anisotropy at both the center and the surface. The resulting equilibrium configurations satisfy energy conditions, causality, compactness bounds, and stability diagnostics. The admissible mass–radius domain overlaps that of neutron star like compact objects, and the isotropic ICG solution is recovered smoothly in the zero-anisotropy limit. These results provide a robust anisotropic gravastar background for future rotational and tidal analyses.

M. Sakib

Wenxin Wang

Xiande Wu

Bangladesh

M. Hafez

M. Kauser

Relativistic formulation and physical viability of anisotropic analytic gravastars

We present the first principle calculation of charmed baryon decay constants employing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math> flavor gauge ensembles with lattice spacings ranging from 0.05 to 0.1 fm and pion masses between 136 and 310 MeV. Under SU(3) flavor symmetry, we construct the charmed baryon interpolating operators and compute the corresponding hadronic matrix elements to extract the bare decay constants for each ensemble. The nonperturbative renormalization is performed via the symmetric momentum-subtraction (SMOM) scheme. After performing systematic chiral and continuum extrapolations, we obtain the decay constants with a precision of 8%–16% from first principles. We further determine several ratios of decay constants among different charmed baryons, for which renormalization factors and part of the systematic uncertainties largely cancel, providing a cleaner probe of SU(3) flavor symmetry breaking. These ratios offer a quantitative, first-principles characterization of the SU(3)-breaking pattern in the charmed baryon sector.

Lei-Yi Li

Jie Ran

Mengchu Cai

Hao-Fei Gao

Yu Gu

Xue-Ying Han

Jun Hua

Jin-Xin Tan

Guang-Yu Wang

Wei Wang

Fanrong Xu

Yi-Bo Yang

Qi-An Zhang

Lattice QCD calculation of charmed baryon decay constants in the continuum limit and at physical mass

In addition to the well-known quantum chromodynamical theta angle, we show that the Standard Model has another theta angle which is invariant under arbitrary chiral rotations of quarks and leptons. The new theta angle can be identified with the quantum electrodynamical theta angle, which should be viewed as an independent parameter of the Standard Model, and may be observable in spacetime with non-simply connected features, either beyond the visible universe or in an effective background from a laboratory setup.