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.

Spain

Mar Bastero-Gil

Portugal

Paulo B. Ferraz

António Torres Manso

Slovenia

Italy

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

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)

Hadron-hadron interactions, being nonperturbative in nature, play a significant role in addressing phenomenological questions in particle physics. Femtoscopy is a powerful tool in heavy-ion collision experiments, enabling the extraction of hadron-hadron interactions via momentum-correlation functions (CFs). These CFs are typically expressed as a convolution of source functions and hadron-hadron wave functions, with the latter encoding information about the interactions. However, source functions remain poorly constrained and are commonly approximated by a Gaussian form. Reconstructing source functions from experimental correlation data constitutes an 'inverse problem.' To address this, we propose a toy model based on Tikhonov regularization. Using a square-well potential with four distinct strengths, we calculate the CFs for inputs of single Gaussian source functions and mixed Gaussian source functions. The resulting CFs are then used to reconstruct the source functions via Tikhonov regularization. Our results show that the Gaussian source function can be successfully reconstructed, highlighting the potential of this approach for extracting realistic source functions from hadron pairs of interest.

Ao-Sheng Xiong

Qi-Wei Yuan

Ming-Zhu Liu

Fu-Sheng Yu

Zhi-Wei Liu

Li-Sheng Geng

Solving the inverse source problem in femtoscopy with a toy model * Supported in part by the Fundamental and Interdisciplinary Disciplines Breakthrough Plan of the Ministry of Education of China (JYB2025XDXM204) and the National Natural Science Foundation of China (W2543006, 12435007). Ming-Zhu Liu acknowledges support from the National Natural Science Foundation of China (12575086). Zhi-Wei Liu acknowledges support from the National Natural Science Foundation of China (12405133) and from the Shenzhen Science and Technology Program (ZDSYS20230626091501002). Fu-Sheng Yu and Ao-Sheng Xiong acknowledge support from the Scientific Research Innovation Capability Support Project for Young Faculty (ZYGXQNJSKYCXNLZCXM-P2) and from the Fundamental Research Funds for the Central Universities (lzujbky-2023-stlt01, lzujbky-2024-oy02, lzujbky-2025-eyt01)

We study the implications for $$B_s - \bar{B}_s$$ mixing and the neutron electric dipole moment (EDM) in a light dark matter model with sizable invisible rare meson decays to accommodate the recent possible deviations from Standard Model (SM) predictions observed in $$B^+\rightarrow K^+\nu \bar{\nu }$$ by Belle II and $$K^+\rightarrow \pi ^+\nu \bar{\nu }$$ by NA62. Given that the neutrinos in these decays escape detection, they can be replaced by other invisible final states. Based on effective operator analysis, it has been proposed that branching ratios for $$B^+\rightarrow K^+ +\text{ invisible }$$ and $$K^+\rightarrow \pi ^+ +\text{ invisible }$$ can naturally be larger than the SM predictions due to the emission of light dark matter pairs. We demonstrate that this scenario can be realized within a UV-complete two-Higgs-doublet model (2HDM) where neutral Higgs bosons mediating dark matter interactions induce significant low-energy effects especially for $$B_s-\bar{B}_s$$ mixing and neutron EDM. Within the allowed parameter space, we find non-negligible contributions to $$B_s - \bar{B}_s$$ mixing. For the neutron EDM, there is a cancellation due to the exchange of neutral spin-zero particles, but QCD renormalization group evolution will lift this cancellation which in fact is generally true for any neutral Higgs contribution. However, we demonstrate that such a cancellation does not occur for charged scalar contributions. Ultimately, the allowed CP-violating phases in the Yukawa sector can generate a neutron EDM at a level consistent with the current experimental bound.

Xuan Hong

Xiao-Gang He

Ming-Wei Li

A light DM model for large $$B \rightarrow K + \text{ invisible }$$ and $$K \rightarrow \pi + \text{ invisible }$$ decays and its implications for $$B_s-\bar{B}_s$$ mixing and neutron EDM

We build a technique to generate rotation from arbitrary static solutions that asymptote to four- or five-dimensional Minkowski spacetime based on Clément’s approach [$\textit{Phys. Rev. D}$ (1998) 4885]. The method is purely algebraic and does not require solving Einstein equations. It proceeds by transforming the static solution to AdS×S asymptotics, performing a coordinate shift to a uniformly rotating frame, and then transforming the solution back to asymptotically flat spacetime. We implement this construction in five-dimensional minimal supergravity, although it applies more broadly to any framework admitting AdS×S geometries and relevant sigma-model transformations. As a first application, we recover simply the Kerr and Myers-Perry black holes directly from Schwarzschild black holes. We then apply the method to the linear class of static Weyl solutions and obtain the first linear ansatz describing an arbitrary number of non-extremal rotating and charged sources. This approach provides a systematic and simple route to constructing non-extremal rotating geometries in four and five dimensions.

India

United States

Soumangsu Chakraborty

Pierre Heidmann

Gela Patashuri

Generating rotation in a snap

<p>Standard calculations of cosmological first-order phase transitions usually assume critical bubbles to nucleate on a homogeneous symmetric vacuum background. However, this assumption can fail in weak transitions, where thermal fluctuations trigger subcritical bubbles before the standard nucleation temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>n</mi></msub></math>. Motivated by this possibility, we systematically examine whether the homogeneous nucleation background approximation is self-consistent. By evolving the Gelmini-Gleiser subcritical bubble kinetics and comparing it with the standard critical bubble nucleation picture, we identify the parameter regions in which the background becomes apparently mixed. A detailed scan of these regions shows that sizable subcritical volume fractions arise when the two phases are nearly degenerate at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>n</mi></msub></math>, the potential barrier is low, the difference of free energy between the symmetric and broken phases is moderate and the transition strength is weak. Within this simplified phenomenological kinetic framework, this scan further calibrates a practical reference criterion, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>log</mi><mn>10</mn></msub><msub><mover accent="true"><mi>f</mi><mo stretchy="false">^</mo></mover><mi>ξ</mi></msub><mo stretchy="false">(</mo><msub><mi>T</mi><mi>n</mi></msub><mo stretchy="false">)</mo><mo>≃</mo><mo>−</mo><mn>1.95</mn></math>, for percent level subcritical bubble volume fractions. Parameter points above this boundary should be treated as mixed background candidates rather than as ordinary homogeneous bounce points.</p>

Guangshang Chen

Yang Xiao

Jin Min Yang

Yang Zhang

Subcritical bubble prehistory in a weak first-order phase transition

<p>We investigate the strong decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><msup><mi>ρ</mi><mo>+</mo></msup><msup><mi>ρ</mi><mo>−</mo></msup><mi>ω</mi></math> and the radiative decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msup><mi>ρ</mi><mn>0</mn></msup><mi>ω</mi></math>, taking into account the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-wave <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi><mi>ω</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi><mi>ϕ</mi></math> final-state interactions, which dynamically generate the scalar meson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>1710</mn><mo stretchy="false">)</mo></math>. Our results demonstrate that a clear peak structure emerges around 1.8 GeV in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ρ</mi><mo>+</mo></msup><mi>ω</mi></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ρ</mi><mo>−</mo></msup><mi>ω</mi></math>) invariant mass distribution of the strong decay, which can be associated with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>1710</mn><mo stretchy="false">)</mo></math> resonance. Similarly, a distinct peak is predicted in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ρ</mi><mn>0</mn></msup><mi>ω</mi></math> invariant mass distribution of the radiative decay. Our results indicate that clear signals of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>1710</mn><mo stretchy="false">)</mo></math> production could be observed in future measurements of these processes at BESIII, Belle II, and the planned Super Tau-Charm Facility, thereby helping to determine its mass and width more precisely.</p>

Wen-Tao Lyu

Luis Roca

Eulogio Oset

Role of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>1710</mn><mo stretchy="false">)</mo></math> in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><msup><mi>ρ</mi><mo>+</mo></msup><msup><mi>ρ</mi><mo>−</mo></msup><mi>ω</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msup><mi>ρ</mi><mn>0</mn></msup><mi>ω</mi></math> reactions

The breakdown of Newtonian dynamics at galactic scales poses a fundamental question regarding the macroscopic behavior of gravity. In this work, we approach this anomaly as an inverse problem, performing a rigorous numerical deconvolution of the gravitational field using high-fidelity kinematic data from the SPARC database. Our analysis reveals that the effective gravitational interaction is characterized by a non-local, damped Helmholtz-like propagator of the form $$G\left( r \right) {\propto }e^{-{\upalpha }r}\cos \left( kr+c \right) /r$$ . This analytical kernel consistently yields correlation coefficients exceeding 0.99 across a morphologically diverse sample of galaxies. To establish a first-principles foundation, we mathematically derive this propagator as an emergent geometric consequence of embedding the observable 3-brane into a multidimensional space-lattice. Notably, this factorized framework provides a natural ultraviolet (UV) regularization of the gravitational potential at the origin, effectively eliminating the classical 1/$\textit{r}$ singularity. Furthermore, we demonstrate that a density-driven geometric screening suppresses extra-dimensional excitations in high-density environments, rigorously ensuring consistency with stringent Solar System constraints. Ultimately, this data-driven, non-local extension of the gravitational propagator offers a robust theoretical alternative to the dark matter hypothesis. It suggests that galactic kinematics are deterministically governed by macroscopic spatial resonances and higher-order geometric degrees of freedom inherent to the cosmic fabric.

Vietnam

Phan Phuc

Signature of a multidimensional space lattice: higher derivative gravity and evidence from galactic dynamics

We present a compact and reproducible matrix level pseudospectral audit of Schwarzschild perturbations designed to quantify sensitivity beyond eigenvalue convergence for semi discrete evolution operators. From the tortoise coordinate master equation we construct a first order formulation and a finite difference generator with outgoing boundary enforcement. We compute the smallest singular value field $$\sigma _{\min }(A_N-sI)$$ on a prescribed complex $\textit{s}$ plane window and extract nested $$\varepsilon $$ pseudospectrum bands for the Regge Wheeler axial gravitational sector $$(\ell =2)$$ and a massless scalar sector $$(\ell =1)$$ . The reported bands, pseudospectral abscissae, and migration radii refer specifically to the stated state variables, Euclidean matrix norm, finite interval, resolution, and penalty implementation; they are not asserted to be invariants of the continuum Schwarzschild quasinormal mode operator. The standard bands provide unstructured matrix perturbation bounds and are not interpreted as direct physical uncertainty intervals. We also evolve a compact initial pulse, extract a detector waveform, report the Euclidean state norm evolution for that pulse, and resolve time frequency content with a short time Fourier transform spectrogram. The results exhibit matrix resolvent sensitivity and time localized transient structure not summarized by eigenvalues alone, together with sector dependent differences consistent with effective barrier structure.

Anirudh Pradhan

Iran

K. Ghaderi

Saudi Arabia

M. Zeyauddin

Error budgets from pseudospectra for black hole ringdown: a Schwarzschild baseline

We present (EvaLuator of tunnElliNg Actions), an open-source Python package designed to compute the full evolution of first-order phase transitions in the early Universe generated by particle physics models, taking into account several refinements that go beyond commonly assumed simplifications. The core of is based on a vectorized implementation of the tunnelling potential formalism, making it the first and only public code to compute finite-temperature tunnelling actions within this framework. This allows for a fast computation of the finite-temperature tunnelling action. This, in turn, enables the sampling of the full range of temperatures where two phases coexist and the use of integral expressions that track the complete evolution of the transition, providing a comprehensive picture of it. In addition, provides all the tools to compute the resulting stochastic gravitational waves spectrum, allowing for the full chain of computations – from the Lagrangian parameter inputs to the final gravitational waves spectrum – in a fast and self-contained implementation.

Czechia

Francesco Costa

Poland

Jaime Hoefken Zink

Michele Lucente

Silvia Pascoli

Salvador Rosauro-Alcaraz

ELENA: a software for fast and precise computation of first order phase transitions and gravitational waves production in particle physics models