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 constructed a four-Higgs-doublet model (4HDM) invariant under $\textit{D}$ $_{5}$ symmetry and investigated its complete neutral vacuum structure in detail. Assuming explicit CP conservation in the scalar potential, we examined whether CP symmetry can be spontaneously broken. We provided a complete list of all possible real and complex vacua, along with the constraints on the potential parameters required for each vacuum solution to exist. We also discussed the positive-definiteness conditions that the Hessian must satisfy for each vacuum to be a local minimum of the potential. The results show that, after spontaneous symmetry breaking, some complex vacua lead to spontaneous CP violation in the potential, whereas the remaining complex vacua still preserve CP conservation. Among these CP-violating complex vacua, one can be regarded as the most general form. Furthermore, we discussed the relationship between real and complex vacua.

China

Dong-Ping Fu

Michihisa Takeuchi

Spontaneous CP violation in the $\textit{D}$ $_{5}$-symmetric four-Higgs-doublet models * Supported by the Fundamental Research Funds for the Central Universities, the One Hundred Talent Program of Sun Yat-sen University, China, and the Guangdong Natural Science Foundation (2026A1515012641)

In this work, we investigate three representative new-physics resonances that couple to Standard Model (SM) quarks through flavor-changing interactions involving the top quark. We identify the possible SMEFT operators at the electroweak scale and analyze their phenomenology.

Min Huang

Yandong Liu

Hao Zhang

Exploring new resonances with direct top flavor changing interactions * Min Huang and Hao Zhang is supported in part by the National Science Foundation of China (12575114, 12235001, 12075257)

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)

The <italic>&#947;d</italic>&#8239;&#8594;&#8239; <italic>K</italic> 0&#923; <italic>p</italic> reaction has been studied to search for a <math altimg='si30.svg'><mrow><mover accent='true'><mi>K</mi><mo>&#175;</mo></mover><mi>N</mi><mi>N</mi></mrow></math> quasi-bound state using the LEPS2 solenoid spectrometer at SPring-8. A localized enhancement concentrated at low <italic>q</italic> is observed in the ( <italic>M</italic> <inf>&#923;<italic>p</italic></inf>, <italic>q</italic>) distribution below the <math altimg='si8.svg'><mrow><msup><mi>K</mi><mo>&#8722;</mo></msup><mi>p</mi><mi>p</mi></mrow></math> mass threshold, where <italic>M</italic> <inf>&#923;<italic>p</italic></inf> is the &#923; <italic>p</italic> invariant mass and <math altimg='si31.svg'><mrow><mrow><mi>q</mi><mo>&#8801;</mo><mo>|</mo></mrow><msub><mover accent='true'><mi>p</mi><mo>&#8594;</mo></mover><mi>&#947;</mi></msub><mo linebreak='goodbreak'>&#8722;</mo><msub><mover accent='true'><mi>p</mi><mo>&#8594;</mo></mover><msup><mi>K</mi><mn>0</mn></msup></msub><mrow><mo>|</mo><mo>=</mo><mo>|</mo></mrow><msub><mover accent='true'><mi>p</mi><mo>&#8594;</mo></mover><mrow><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle><mi>p</mi></mrow></msub><mrow><mo>|</mo></mrow></mrow></math> is the momentum transfer. A two-dimensional ( <italic>M</italic> <inf>&#923;<italic>p</italic></inf>, <italic>q</italic>) fit demonstrates that the enhancement near the threshold is statistically significant, yielding a local significance of 7.3&#8201; <italic>&#963;</italic>. The enhancement is characterized by effective shape parameters including the Breit&#8211;Wigner mass <italic>M</italic> and width &#915;, and a Gaussian form-factor momentum scale <italic>Q</italic>: <math altimg='si32.svg'><mrow><mi>M</mi><mo linebreak='goodbreak'>=</mo><mn>2.354</mn><mo>&#177;</mo><mn>0.011</mn><msubsup><mrow><mo>(</mo><mrow><mtext>stat</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mrow><mo>&#8722;</mo><mn>0.005</mn></mrow><mrow><mo>+</mo><mn>0.009</mn></mrow></msubsup><mrow><mo>(</mo><mrow><mtext>syst</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mspace width='0.33em' /><mtext>GeV</mtext><mo linebreak='goodbreak'>/</mo><msup><mi>c</mi><mn>2</mn></msup></mrow></math>, <math altimg='si33.svg'><mrow><mstyle mathvariant='normal'><mi>&#915;</mi></mstyle><mo linebreak='goodbreak'>=</mo><mn>0.055</mn><mo>&#177;</mo><mn>0.023</mn><msubsup><mrow><mo>(</mo><mrow><mtext>stat</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mrow><mo>&#8722;</mo><mn>0.009</mn></mrow><mrow><mo>+</mo><mn>0.031</mn></mrow></msubsup><mrow><mo>(</mo><mrow><mtext>syst</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mspace width='0.33em' /><mtext>GeV</mtext><mo linebreak='goodbreak'>/</mo><msup><mi>c</mi><mn>2</mn></msup></mrow></math>, and <math altimg='si34.svg'><mrow><mi>Q</mi><mo linebreak='goodbreak'>=</mo><mn>0.350</mn><mo>&#177;</mo><mn>0.041</mn><msubsup><mrow><mo>(</mo><mrow><mtext>stat</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mrow><mo>&#8722;</mo><mn>0.010</mn></mrow><mrow><mo>+</mo><mn>0.035</mn></mrow></msubsup><mrow><mo>(</mo><mrow><mtext>syst</mtext><mo>.</mo></mrow><mo>)</mo></mrow><mspace width='0.33em' /><mtext>GeV</mtext><mo linebreak='goodbreak'>/</mo><mi>c</mi></mrow></math>. The obtained results support the existence of a <math altimg='si30.svg'><mrow><mover accent='true'><mi>K</mi><mo>&#175;</mo></mover><mi>N</mi><mi>N</mi></mrow></math> quasi-bound state in photoproduction.

Japan

R. Kobayakawa

South Korea

J.K. Ahn

S. Ajimura

Taiwan

W.C. Chang

M.L. Chu

S. Daté

T. Gogami

T.A. Hashimoto

T. Hotta

T. Ishikawa

H. Katsuragawa

H. Kohri

Y. Ma

M. Miyabe

K. Mizutani

N. Muramatsu

T. Nakano

Vietnam

T.H. Nam

M. Niiyama

Y. Nozawa

Y. Ohashi

H. Ohkuma

H. Ohnishi

T. Ohta

Canada

C. Rangacharyulu

S.Y. Ryu

Y. Sada

H. Shimizu

M. Sumihama

S. Suzuki

S. Tanaka

A.O. Tokiyasu

N. Tomida

K. Watanabe

T. Yorita

C. Yoshida

M. Yosoi

Evidence for a <math altimg='si30.svg'><mrow><mover accent='true'><mi>K</mi><mo>&#175;</mo></mover><mi>N</mi><mi>N</mi></mrow></math> quasi-bound state in the <italic>&#947;d</italic>&#8239;&#8594;&#8239; <italic>K</italic> 0&#923; <italic>p</italic> reaction

We introduce optimal transport (OT) as a physics-based intermediate event representation for weakly supervised anomaly detection. With only 0.5% injection of resonant signals in the LHC Olympics benchmark datasets, the OT-augmented feature set achieves nearly twice the significance improvement of the standard high-level observables using an idealized setup, while end-to-end deep learning on low-level four-momenta is less effective in this low-signal regime. The observed gains persist across signal types and classifiers considered in this study, suggesting that structured, physics-informed representations can provide a useful complement to existing approaches for anomaly detection.

Tianji Cai

United States

Aditya Bhargava

Benjamin Nachman

Optimal transport event representation for anomaly detection

We study how to recover timelike worldlines in AdS from CFT data as a toy model for holographically reconstructing realistic observers. We give a bulk extremization procedure that determines composite timelike-spacelike geodesics that connect timelike-separated boundary points. The total geodesic length matches the length extracted from CFT correlators at the timelike-separated points. We show agreement in Poincaré AdS, for generic boundary points in global AdS, and also for the Bañados-Teitelboim-Zanelli solution, in which the timelike segment probes behind the horizon. We refine related methods to compute timelike entanglement entropy in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>/</mo><msub><mrow><mi>CFT</mi></mrow><mn>2</mn></msub></mrow></math> and recover known results.

Hardik Bohra

Allic Sivaramakrishnan

Composite AdS geodesics for CFT correlators and timelike entanglement entropy

Previously, we proposed an infrared vacuum wave functional for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></math> Yang-Mills theory peaked at thin center vortices and showed that it yields an area law for the Wilson loop. In this work, we use this wave functional to calculate the spatial ’t Hooft loop, for which we find a perimeter law, in accordance with ’t Hooft’s criterion for confinement.

Brazil

Germany

D.R. Junior

L.E. Oxman

H. Reinhardt

’t Hooft loop in a center-vortex wave functional

We introduce accelerated sequential posterior inference via reuse (ASPIRE), a broadly applicable framework that transforms existing posterior samples and Bayesian evidence estimates into unbiased results under alternative models without rerunning the original analysis. ASPIRE combines normalizing flows with a generalized sequential Monte Carlo (SMC) scheme, enabling efficient updates of existing results and reducing total likelihood evaluations and wall times by factors of up to 5.8 and 5.5, respectively, with larger gains per posterior sample. This addresses a growing problem in gravitational-wave astronomy, where events must be repeatedly reanalyzed under different models or physical hypotheses. We show that ASPIRE reproduces full Bayesian results when switching waveform models or adding physical effects such as spin precession and orbital eccentricity. With this statistical robustness, ASPIRE turns repeated reanalyses into fast, reliable updates—paving the way for systematic studies of waveform systematics, scalable reanalyses across large event catalogs, and broadly applicable Bayesian reanalysis across other scientific domains.

United Kingdom

Michael J. Williams

Accelerated Sequential Posterior Inference via Reuse for Gravitational-Wave Analyses

Particle physics experiments rely on the (generalised) likelihood ratio test (LRT) for searches and measurements, which consist of composite hypothesis tests. However, this test is not guaranteed to be optimal, as the Neyman–Pearson lemma pertains only to simple hypothesis tests. Any choice of test statistic thus implicitly determines how statistical power varies across the parameter space. An improvement in the core statistical testing methodology for general settings with composite tests would have widespread ramifications across experiments. We discuss an alternate test statistic that provides the data analyzer an ability to focus the power of the test on physics-motivated regions of the parameter space. We demonstrate the improvement from this technique compared to the LRT on a Higgs $$\rightarrow \tau \tau $$ dataset simulated by the ATLAS experiment and a dark matter dataset inspired by the LZ experiment. We also employ machine learning to efficiently calibrate critical values for a family of tests, which are then inverted to obtain statistically valid confidence intervals.