Thu·Jul 3, 2025Thursday·July 3, 2025

1. 01*

   QED positronium and the exact renormalization group

   Guillermo Hansen · Roberto Trinchero

   Quantum electrodynamics (QED) is studied in the framework of the exact (functional) renormalization group (ERG). This is done using an approach to these equations which employs dimensional regularization. Simultaneous solutions of the ERG equations and Ward identities are considered. An approach to the study of bound states at long distances in the ERG is employed to describe the positronium. This is done by introducing a real scalar field which describes that bound state. The flow equations are studied using an effective action ansatz and a low-momentum expansion.

   hep-phhep-th0 citations
2. 02*

   New avenues for the neutrino dipole portal exploration at the energy frontier

   Natascia Vignaroli🇮🇹

   We present a comprehensive and gauge-invariant study of the neutrino dipole portal at the energy frontier. Assuming negligible active-sterile mixing, we analyze sterile neutrino production via dimension-6 dipole operators coupling to the electroweak field strengths. The analysis incorporates both single- and double-gauge-boson effective interactions. We investigate novel collider signatures at the HL-LHC, the FCC-hh -- studied here in this context for the first time -- and a 10 TeV muon collider. Particular emphasis is placed on electroweak boson-initiated processes, which dominate in the high-mass regime above $\sim$1 TeV. At the muon collider, these VBF-like topologies enable production even when the dipole couples to non-muonic flavors, offering a unique and sensitive probe for different flavor scenarios. We derive sensitivity projections for various theoretical benchmarks, reaching dipole couplings down to $d_{\gamma }\sim 6\times 10^{-7}$ GeV${}^{-1}$ at FCC-hh and $d_{\gamma }\sim 2\times 10^{-7}$ GeV${}^{-1}$ at the muon collider.

   hep-phastro-ph.HEhep-exJHEP(2025)·6 citations
3. 03*

   Constraining four-heavy-quark operators with top-quark, Higgs, and electroweak precision data

   Stefano Di Noi🇩🇪 · Hesham El Faham🇬🇧 · Ramona Gröber🇮🇹 · Marco Vitti🇩🇪 · Eleni Vryonidou🇬🇧

   We establish constraints on the dimension-six four-heavy-quark operators in the Standard Model Effective Field Theory (SMEFT) by synthesising LHC measurements of top-quark and single-Higgs production with electroweak precision observables. We scrutinise the choice of the ${\gamma }_5$ scheme in single-Higgs calculations, demonstrating its non-negligible impact on SMEFT fits.

   hep-phJHEP(2026)·19 citations
4. 04*

   Beyond the Standard Model Higgs physics: Hunting $h\to bs$ with Higgs-strahlung at CEPC and FCC-ee

   M. A. Arroyo-Ureña🇲🇽 · Diego Carreño · A. I. García-Gutierrez🇲🇽 · M. G. Villanueva-Utrilla🇲🇽 · T. A. Valencia-Pérez🇲🇽

   The next generation of circular electron-positron colliders, such as the Circular Electron Positron Collider and the Future Circular Collider, will provide an unprecedented level of precision in probing the properties of the Higgs boson. In this study, we examine the flavor-changing neutral Higgs decay $h\to bs$ produced via the Higgs-strahlung process within the framework of the Two-Higgs-Doublet Model Type III. We identify regions of the parameter space that remain viable after applying stringent constraints from current experimental data. By employing a multivariate analysis based on Boosted Decision Trees, we project that a signal significance of $5\sigma$ can be achieved, even after accounting for irreducible backgrounds and systematic uncertainties. Our findings show that these future colliders could offer a unique avenue for discovering signatures of physics beyond the standard model.

   hep-phJHEP(2026)·2 citations
5. 05*

   A Frequentist Simulation-Based Inference Treatment of Sterile Neutrino Global Fits

   Joshua Villarreal🇺🇸 · Julia Woodward🇺🇸 · John Hardin🇺🇸 · Janet Conrad🇺🇸

   A critical challenge in particle physics is combining results from diverse experimental setups that measure the same physical quantity to enhance precision and statistical power, a process known as a global fit. Global fits of sterile neutrino searches, hunts for additional neutrino oscillation frequencies and amplitudes, present an intriguing case study. In such a scenario, the key assumptions underlying Wilks' theorem, a cornerstone of most classic frequentist analyses, do not hold. The method of Feldman and Cousins, a trials-based approach which does not assume Wilks' theorem, becomes computationally prohibitive for complex or intractable likelihoods. To bypass this limitation, we borrow a technique from simulation-based inference (SBI) to estimate likelihood ratios for use in building trials-based confidence intervals, speeding up test statistic evaluations by a factor $>10^4$ per grid point, resulting in a faster, but approximate, frequentist fitting framework. Applied to a subset of sterile neutrino search data involving the disappearance of muon-flavor (anti)neutrinos, our method leverages machine learning to compute frequentist confidence intervals while significantly reducing computational expense. In addition, the SBI-based approach holds additional value by recognizing underlying systematic uncertainties that the Wilks approach does not. Thus, our method allows for more robust machine learning-based analyses critical to performing accurate but computationally feasible global fits. This allows, for the first time, a global fit to sterile neutrino data without assuming Wilks' theorem. While we demonstrate the utility of such a technique studying sterile neutrino searches, it is applicable to both single-experiment and global fits of all kinds.

   hep-phhep-exMach.Learn.Sci.Tech.(2025)·5 citations
6. 06*

   Flux of Extragalactic Dark Matter in Direct Detection Experiments

   Shokhruz Kakharov · Abraham Loeb🇺🇸

   We calculate the contribution of extragalactic dark matter to the local dark matter density and flux in the Milky Way. By analyzing the Galactic escape velocity as a function of direction, we establish the criterion for separating dark matter particles bound to the Milky Way and those originating from the Local Group environment. Our analysis reveals that approximately 25% of dark matter particles in the Solar neighborhood have an extragalactic origin, contributing nearly 38% of the total mass flux. The directional dependence of this extragalactic component shows significant anisotropy across the sky, with implications for direct detection experiments. We provide quantitative predictions for detection rates and signatures that could help identify the extragalactic dark matter component in current and future experiments.

   hep-phastro-ph.CO3 citations
7. 07*

   Gravitational waves from a dilaton-induced, first-order QCD phase transition

   Aleksandr Chatrchyan🇸🇪 · M.C. David Marsh🇸🇪 · Charalampos Nikolis🇸🇪

   We show that a `QCD dilaton' field, whose vacuum expectation value sets the strong coupling, can render the Quantum Chromodynamic (QCD) confinement transition first-order. The QCD dilaton is cosmologically attracted to a false vacuum at weak coupling in the early universe. Quantum tunnelling towards the true vacuum triggers prompt chiral symmetry breaking and confinement of QCD, leading to detonating bubbles of the hadronic phase. We find that plasma sound waves produced by this dilaton-induced, first-order QCD phase transition generate a stochastic gravitational wave signal strikingly similar to the recently detected gravitational wave background from Pulsar Timing Arrays. We briefly comment on how this theory can be probed through collider experiments and cosmology.

   hep-phastro-ph.COhep-thPRL(2026)·8 citations
8. 08*

   Lepton flavor violating decay of true muonium: $({\mathbf{\mu }}^{+}{\mathbf{\mu }}^{-})\to {\mathbf{\mu }}^{\pm }{\mathbf{e}}^{\mp }$

   Ryotaro Minato🇯🇵 · Akira Sato🇯🇵 · Ryosuke Suda🇯🇵 · Masato Yamanaka🇯🇵

   We propose a new channel for probing charged lepton flavor violation (CLFV): the decay of true muonium into a lepton pair of different flavor, $({\mu }^{+}{\mu }^{-})\to {\mu }^{\pm }{e}^{\mp }$. This purely leptonic two-body decay provides a clean experimental signature in the form of energetic, oppositely charged leptons. It is sensitive not only to photonic dipole interactions but also to four-fermion contact interactions, and is free from hadronic uncertainties in theoretical predictions. We evaluate the branching ratios induced by scalar-, vector-, and dipole-type CLFV operators. Our results show that the branching ratio can reach up to $\mathcal{O}(10^{-20})$ within current experimental bounds. This decay mode may be discovered as an early-stage physics opportunity of the muon collider program by utilizing the large number of muons produced at its front end.

   hep-ph1 citation
9. 09*

   Study of $\tau \to e{M}^{+}{M}^{-}$ decays in the N-B-LSSM

   Rong-Zhi Sun🇨🇳 · Shu-Min Zhao🇨🇳 · Shuang Di🇨🇳 · Xing-Xing Dong🇨🇳

   Within the framework of the next to the minimal supersymmetric (SUSY) extension of the Standard Model (SM) with a local B-L gauge symmetry (N-B-LSSM), we study lepton flavor violating (LFV) $\tau \to e{M}^{+}{M}^{-}$ decays: $\tau \to e{\pi }^{+}{\pi }^{-}$,~$\tau \to e{\pi }^{+}{K}^{-}$,~$\tau \to e{K}^{+}{K}^{-}$. According to the latest experimental data, the influence of different sensitive parameters on the branching ratios is considered. It can be seen from the numerical analysis that the main sensitive parameters and LFV sources are non-diagonal elements corresponding to the initial and final leptons. This work can provide a basis for discovering the existence of new physics (NP).

   hep-phCPC(2025)·0 citations
10. 10*

    The electromagnetic form factors of $\Sigma$ and ${\Sigma }^0\to \Lambda$ transition in the timelike region

    Cheng Chen🇨🇳 · Bing Yan🇨🇳 · Bing-Wei Long🇨🇳 · Ju-Jun Xie🇨🇳

    We investigate the $e^{+}{e}^{-}\to \Sigma \bar{\Sigma }$ and $e^{+}{e}^{-}\to \Lambda {\bar{\Sigma }}^0$ reactions within the extended vector meson dominance model. In addition to the ground state mesons $\rho$ and $\omega$, we consider the contributions of the excited states $\rho (3D)$, $\omega (3D)$, $\varphi (3D)$, and $\rho (6D)$. It is found that the current experimental data on the $\Sigma$ electromagnetic form factors in timelike region can be well reproduced. And the $\varphi (3D)$ resonance is essential to the near threshold enhancement of the cross section for the $e^{+}{e}^{-}\to \Sigma \bar{\Sigma }$ reaction. Furthermore, in the $e^{+}{e}^{-}\to \Lambda {\bar{\Sigma }}^0$ reaction, the $\rho (3D)$ is important to get a good fit for the experimental results.

    hep-phChin.Phys.Lett.(2025)·1 citation
11. 11*

    Axion-like particle production in SUSY DFSZ-like model at the ILC and LHeC

    Bui Thi Ha Giang🇻🇳 · Dang Van Soa🇻🇳

    We present an analysis of axion-like particle (ALP) production in SUSY DFSZ-like model at the ILC and LHeC. We calculate the differential and total cross-sections in ${\gamma }^{\ast }{e}^{-}$ and $e^{-}{e}^{+}$ collisions including the effect of the scattering angle, the polarization coefficients, the energy and the ALP mass. From that, we compare the total cross-sections at the LHeC to those at the ILC. To predict the existence of ALP signals, we evaluate the significance level of the final state followed by ALP decaying di-photon at the LHeC and the ILC.

    hep-ph0 citations
12. 12*

    The axion signature of strange quark star in SGR 0501+4516

    C.R. Das🇷🇺

    We study the axion effects on quark matter and quark-matter cores in strange quark magnetars using a three-flavor Nambu-Jona-Lasinio model to represent the charge-parity violating effects through the axion field. Here, axions decay to gamma rays in a very strong magnetic field, which the Fermi Large Area Telescope (Fermi-LAT), Imaging X-ray Polarimetry Explorer (IXPE), and XMM-Newton will be able to detect.

    hep-phastro-ph.HEAdvances in Nuclear Science and Applicati…·0 citations
13. 13*

    Parton-shower and fixed-order QCD effects in Higgs-boson production in weak-boson fusion and its decays to bottom quarks

    Arnd Behring🇩🇪 · Kirill Melnikov🇩🇪 · Ivan Novikov🇩🇪 · Giulia Zanderighi🇩🇪

    Recently, it was observed [arXiv:2407.09363] that an aggressive cut on the $b$-jets' transverse momenta applied to Higgs-boson production in weak-boson fusion followed by the decay $H\to b\bar{b}$, leads to very large QCD corrections to the fiducial cross section. In this paper we show that these corrections are caused by soft and collinear QCD radiation and, therefore, can be efficiently treated by a parton shower. We combine the parton-shower description of the decay $H\to b\bar{b}$ with NNLO QCD corrections to Higgs production in weak-boson fusion and its subsequent decay, and demonstrate that the quality of the theoretical prediction is markedly improved even if $b$-jets with rather high transverse momenta are selected. The remaining uncertainty of the theoretical prediction, mainly driven by imprecise modelling of $H\to b\bar{b}$ decay, is estimated to be of the order of $\mathcal{O}(5-7\%)$.

    hep-phPRD(2025)·2 citations
14. 14*

    A Factorized Mass Structure of Fermions and Its Fit

    Qingfeng Cao🇨🇳 · Ying Zhang🇨🇳

    The structure of the mass matrix, a challenging problem in the Standard Model, is closely related to flavor phenomenology and the understanding of the Yukawa interaction. We derive a factorized mass structure based on observed fermion mass hierarchies, investigating the role of $SO(2{)}^f$ family symmetry in explaining the approximate degeneracy of light quark generations and its connection to flavor mixing. Our calculation includes the slightest modification from the lightest fermions by $\mathcal{O}(h^2)$ hierarchy corrections. Using this model-independent framework, we systematically analyze all mass patterns and perform comprehensive fits to both quark CKM and lepton PMNS mixing data with extended normal-ordered Dirac neutrinos. The results demonstrate this framework's capacity to unify flavor phenomena while simultaneously providing new insights into the fundamental nature of Yukawa interactions.

    hep-phNPB(2025)·1 citation
15. 15*

    Gluon Distributions in the Pion

    Satvir Kaur🇨🇳 · Chandan Mondal🇨🇳

    We formulate a light-front model for the pion that explicitly incorporates the gluonic degree of freedom. In this framework, high-energy scattering off the pion is described by an active gluon, while the remaining constituents are treated as a spectator system with an effective mass. The mass spectrum and light-front wave functions (LFWFs) of the pion are determined by solving two Schrödinger-like equations derived from quantum chromodynamics: the light-front holographic equation in the chiral limit and the 't~Hooft equation. Using the resulting LFWFs, we compute the gluon distributions within pion, including the parton distribution functions in comparison with the available global fits, generalized parton distributions, and transverse momentum-dependent distributions. The present analysis is restricted to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) domain of the pion's gluon GPD, without explicit construction of the Efremov-Radyushkin-Brodsky-Lepage (ERBL) region. Consequently, the polynomiality condition for full Mellin moments is not satisfied by construction. Furthermore, we demonstrate that the obtained LFWFs provide a good description of the gravitational form factors of pion when compared with the recent lattice QCD results.

    hep-phPRD(2025)·9 citations
16. 16*

    Searching for gluon saturation effects in the momentum transfer dependence of coherent charmonium electroproduction off nuclei

    J. Nemchik🇨🇿 · J. Óbertová🇨🇿

    We study for the first time the transverse momentum transfer distributions $d\sigma /dt$ in coherent production of charmonia in nuclear ultra-peripheral and electron-ion collisions within the QCD color dipole approach based on a rigorous Green function formalism. This allows us to treat properly the color transparency effects, as well as the higher and leading-twist shadowing corrections associated with the $|Q\bar{Q}⟩$ and $|Q\bar{Q}nG⟩$ Fock components of the photon. While the multi-gluon photon fluctuations represent the dominant source of nuclear shadowing at kinematic regions related to the recent LHC and its future upgrade to LHeC, the upcoming electron-ion collider at RHIC will additionally require the proper incorporation of reduced quark shadowing. The latter effect leads to a significant decrease in the differential cross sections $d\sigma /dt$ compared to standard calculations based on the eikonal form for the dipole-nucleus amplitude. The leading-twist shadowing corrections, corresponding to a non-linear QCD evolution of a partial dipole-nucleus amplitude, reduce substantially charmonium $t$-distributions in the LHeC energy range. We predict a non-monotonic energy dependence of $d\sigma /dt$ suggesting so possible gluon saturation effects with increased onset at larger $t$-values. In addition to shadowing corrections, we study how the color transparency effects affect the shape of $t$-dependent nuclear modification factor. We also briefly discuss several aspects that can modify the charmonium production rate and thus may have a large impact on the search for gluon saturation effects.

    hep-phhep-thPRD(2025)·2 citations
17. 17*

    Symmetries of Hot SM, Magnetic Flux & Baryogenesis from Helicity Decay

    Yuta Hamada🇯🇵 · Kyohei Mukaida🇯🇵 · Fumio Uchida🇯🇵

    We revisit the electroweak crossover of the Standard Model (SM) in the early Universe, focusing on the interplay between generalized global symmetries, magnetic flux dynamics, and baryogenesis. Employing the dimensionally reduced 3d effective field theory of the SM at high temperature, we identify the symmetry structure -- including higher-form and magnetic symmetries -- and analyze their spontaneous breaking patterns across the crossover. We further define a gauge-invariant mixing angle that interpolates between $\mathrm{U}(1{)}_Y$ and $\mathrm{U}(1{)}_{\mathrm{em}}$ magnetic fields. Based on this framework, we examine baryogenesis via decaying magnetic helicity and identify three key effects: the baryon asymmetry is modified by an $\mathcal{O}(1)$ factor due to (1) the gauge-invariant definition of the mixing angle and (2) the approximate conservation of the unconfined magnetic flux; (3) a novel non-perturbative process in the presence of magnetic flux, which has been overlooked in previous analyses. Our findings suggest that the previous estimation of baryon asymmetry from the magnetic helicity decay may have sizable uncertainties, and we caution against relying on it, calling for further investigation.

    hep-phastro-ph.COhep-thJHEP(2026)·11 citations
18. 18*

    Bayesian Analysis of Non-extensive Parameters in Au-Au Collisions

    Randy Dobler🇨🇭 · Juliana O. Costa🇧🇷 · Marcelo D. Alloy🇧🇷 · Débora P. Menezes🇧🇷

    In this work, a Bayesian statistical framework is employed to analyze particle yield ratios in Au-Au collisions, utilizing Non-Extensive Statistics (NES). Through Markov Chain Monte Carlo (MCMC) sampling, we systematically estimate key parameters, including the non-extensive factor $q$, temperature $T$, and chemical potential $\mu$. Our analysis confirms previous findings highlighting the suitability and robustness of Bayesian methods in describing heavy-ion collision data. A subsequent Bayes factor analysis does not provide definitive evidence favoring an Excluded Volume Hadron Resonance Gas (EV-HRG) model over the simpler NES approach. Overall, these results suggest that combining NES with Bayesian inference can effectively model particle distributions and improve parameter estimation accuracy, demonstrating the potential of this approach for future studies on relativistic nuclear interactions.

    hep-phIJMPE(2026)·0 citations
19. 19*

    Precision determination of ${\alpha }_{\text{s}}$ from Dijet Cross Sections in the Multi-TeV Range

    João Pires🇵🇹

    In this talk we present a determination of the strong coupling constant ${\alpha }_{\text{s}}$ and its energy-scale dependence based on a next-to-next-to-leading order (NNLO) QCD analysis of dijet production. Using the invariant mass of the dijet system to probe ${\alpha }_{\text{s}}$ at different scales, we extract a value of ${\alpha }_{\text{s}}(m_{\text{Z}})=0.1178\pm 0.0022$ from LHC dijet data. The combination of various LHC datasets significantly extends the precision and scale reach of the analysis, enabling the first determination of ${\alpha }_{\text{s}}$ up to 7 TeV. By incorporating dijet cross sections from HERA, we further probe ${\alpha }_{\text{s}}$ at smaller scales, covering a kinematic range of more than three orders of magnitude. Our results are in excellent agreement with QCD predictions based on the renormalization group equation, providing a stringent test of the running of the strong coupling across a wide energy range.

    hep-phhep-ex0 citations
20. 20*

    Extending the sensitivity of heavy sterile neutrino searches with solar neutrino experiments

    Yutao Zhu🇨🇳 · Haoyang Fu🇨🇳 · Wentai Luo🇨🇳 · Shaomin Chen🇨🇳 · Litao Yang🇨🇳 · Zhicai Zhang🇨🇳

    A sensitivity study of the search for heavy sterile neutrinos (${\nu }_H$) in the MeV mass range using solar neutrino experiments is presented. ${\nu }_H$, with masses ranging from a few MeV up to around 15 MeV, can be produced in the Sun through ${}^8$B decay and subsequently decay into ${\nu }_e{e}^{+}{e}^{-}$. Its flux and lifetime strongly depend on the mixing parameter $|U_{eH}{|}^2$ and mass $m_{{\nu }_H}$. The ${\nu }_H$ signal can be detected via its decay products, either the $e^{+}{e}^{-}$ pair or ${\nu }_e$, depending on whether ${\nu }_H$ decays inside or outside the detector. Expected signal yields for both detection methods (detecting $e^{+}{e}^{-}$ or ${\nu }_e$ signal) are presented across the full $|U_{eH}{|}^2$ and $m_{{\nu }_H}$ parameter space. These two methods are found to be complementary in different regions of the $|U_{eH}{|}^2$ and $m_{{\nu }_H}$ phase space. By combining both approaches, we anticipate observing at least a handful of signal events across most of the parameter space of $10^{-6}<|U_{eH}{|}^2<1$ and 2 MeV $<m_{{\nu }_H}<$ 14 MeV, assuming a 500-ton solar neutrino experiment operating for one year. Key variables, such as the energy spectra and opening angle of ${\nu }_e$ or $e^{+}{e}^{-}$ and the solar angle of ${\nu }_e$ and its scattered electron, are also discussed to help distinguish signal from major backgrounds, such as solar neutrino events.

    hep-phhep-ex0 citations
21. 21*

    Charge quantisation, monopoles and emergent symmetry in the Standard Model and its embeddings

    Rodrigo Alonso🇬🇧 · Despoina Dimakou🇬🇧 · Yunji Ha🇬🇧 · Valentin V. Khoze🇬🇧

    This work studies the connection of the global properties of the SM gauge group to 1-form discrete symmetries, the possible non-Abelian embeddings of the SM group, and electric and magnetic charge quantisation. Building on previous work, we introduce indexes to characterise the group choices, connect the concept of compositeness degree to emergent electric 1-form symmetry, introduce a new model to fill in the $p=1$ gap, and analyse the magnetic spectrum while connecting its UV and IR realisations.

    hep-phhep-thJHEP(2025)·8 citations
22. 22*

    Pentaquarks made of light quarks and their admixture to baryons

    Nicholas Miesch🇺🇸 · Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸

    This paper is a continuation of our studies of multiquark hadrons. The anti-symmetrization of their wavefunctions required by Fermi statistics is nontivial, as it mixes orbital, color, spin and flavor structures. In our previous papers we developed a method to find them based on the representations of the permutation group, and derived the explicit wave functions for baryons excited to the first and second shells $(L=1,2)$, tetraquarks $qq\bar{q}\bar{q}$ and hexaquarks ($6q$). Now we apply it to light pentaquarks ($qqqq\bar{q}$), in the S- and P-shells ($L=0,1$). Using Jacobi coordinates, one can use the hyperdistance approximation in 12-dimensional space. We further address the issue of ``unquenching" of baryons, by considering their mixing with pentaquarks, via two channels, through the addition of $\sigma$-like or $\pi$-like $\bar{q}q$ pairs. This mixing is central for understanding of the observed flavor asymmetry of the antiquark sea, the amount of orbital motion issue as well as other nucleon properties.

    hep-phnucl-thPRD(2025)·2 citations
23. 23*

    ${\Lambda }_b\to {\Lambda }^{(\ast )}\nu \bar{\nu }$ decays and the recent Belle-II $B^{+}\to K^{+}\nu \bar{\nu }$ data

    Diganta Das🇮🇳 · Dargi Shameer🇮🇳 · Ria Sain🇨🇳

    The Belle-II experiment has recently reported the first measurement of $B^{+}\to K^{+}\nu \bar{\nu }$ decay which exceeds the Standard Model prediction by approximately 2.7$\sigma$. The deviation may indicate the presence of new physics beyond the Standard Model in the $b\to s\nu \bar{\nu }$ sector. Under this assumption, we study the hadronic ${\Lambda }_b\to \Lambda (\to p\pi )\nu \bar{\nu }$ and ${\Lambda }_b\to {\Lambda }^{\ast }(\to N\bar{K})\nu \bar{\nu }$ decays within both the Standard Model and beyond. We work in a low energy effective field theory framework with additional light right-handed neutrinos. We calculate the differential branching ratios of these decay modes and explore the implications of the Belle-II results through various observables.

    hep-phPRD(2025)·3 citations
24. 24*

    Spin hydrodynamics -- recent developments

    Samapan Bhadury🇵🇱 · Zbigniew Drogosz🇵🇱 · Wojciech Florkowski🇵🇱 · Valeriya Mykhaylova🇵🇱

    After briefly touching on relativistic hydrodynamics, we provide a detailed description of recent developments in spin hydrodynamics. We discuss the theory of perfect spin hydrodynamics within two different approaches, which lead to identical generalized thermodynamic relations. We also indicate the applicability range of the theory, finding it compatible with the conditions existing in the late stages of heavy-ion collisions. Finally, we discuss the near-equilibrium dynamics.

    hep-phnucl-thJ.Subatomic Part.Cosmol.(2025)·4 citations
25. 25*

    Final state interaction in the ${\Lambda }_b\to D^{+}{D}^{-}\Lambda ,D^0{D}_s^{-}p,D_s^{+}{D}_s^{-}\Lambda$ reactions

    Jing Song🇨🇳 · Melahat Bayar🇪🇸 · Eulogio Oset🇪🇸

    We study the three-body decays \(\Lambda_b \to D^+ D^- \Lambda,~D^0D_s^- p,~D_s^+D_s^-\Lambda\), considering both internal and external emission mechanisms that produce various meson-baryon final states. Using a unitarized coupled-channel approach based on the local hidden gauge formalism, we analyze final state interactions in the exotic anticharm systems with strangeness \(S=-1\) and \(S=-2\). Significant threshold enhancements appear in both pseudoscalar and vector meson-baryon channels, indicating strong final state interactions and the possible formation of molecular exotic states below threshold. These features remain stable under variations of model parameters. Our results provide valuable insights into heavy hadron decay dynamics and offer theoretical guidance for future experimental searches of open-charm strange exotic hadrons.

    hep-phPRD(2025)·1 citation
26. 26*

    Freeze-In Dark Matter and Leptogenesis: a ${\psi }^{\prime }$SM route

    Adeela Afzal🇷🇺 · Rishav Roshan🇬🇧

    We investigate the possibility of \emph{freeze-in} dark matter production and baryogenesis via leptogenesis in a ${\psi }^{\prime }$SM model, which is an $E_6$ extension of the Standard Model, featuring a residual $U(1{)}_{{\psi }^{\prime }}$ gauge symmetry. This symmetry arises from a linear combination of $U(1{)}_{\chi }$ and $U(1{)}_{\psi }$, both of which are subgroups of the $E_6$. The spontaneous breaking of $U(1{)}_{{\psi }^{\prime }}$ symmetry governs the dynamics of a singlet fermion, which serves as a freeze-in dark matter candidate. The dark matter mass arises from dimension-five operators, and a discrete symmetry ensures its stability. We show that freeze-in production from scalar decay can yield the correct relic abundance for dark matter masses between a few MeV to a few hundred GeV. Simultaneously, heavy right-handed neutrinos generate light neutrino masses via the type-I seesaw and produce the observed baryon asymmetry via leptogenesis.

    hep-phastro-ph.COgr-qchep-thEPJC(2026)·1 citation
27. 27*

    Probing CP and flavor violation in neutral kaon decays with ALPs

    Reuven Balkin🇺🇸 · Stefania Gori🇺🇸 · Christiane Scherb🇺🇸

    We analyze the three-body decays of the long-lived neutral kaon $K_L\to \pi \pi a$, where $a$ is an axion-like particle (ALP), and compare them to the two-body decay $K_L\to {\pi }^{0}a$. While the latter requires both flavor violation (FV) and $CP$ violation (CPV), the former can proceed via FV alone, allowing the ratio of decay rates to serve as a probe of CPV of the underlying UV theory. We emphasize the importance of weak-interaction-induced contributions, often neglected in recent calculations. We explore both minimal and non-minimal flavor-violating scenarios, and identify classes of models where ALP production from neutral three-body decays is comparable to - or even dominates over - the two-body decay, despite its reduced phase space. Finally, we discuss the phenomenological implications of our results and show how these decays can provide complementary probes of ALP couplings beyond those accessible via charged kaon channels.

    hep-phhep-exJHEP(2026)·3 citations
28. 28*

    Sub-keV dark matter can strongly ionize molecular clouds

    Pedro De la Torre Luque🇪🇸 · Pierluca Carenza🇸🇪 · Thong T. Q. Nguyen🇸🇪

    We show that the ionization of dense molecular clouds can be used to set strong constraints on dark matter models producing UV/X-ray photons in their annihilation or decay. We place robust and competitive constraints on various dark matter models, such as axion-like particles, scalars and sterile neutrinos, for masses between $\sim 30$~eV and $10$~keV, and project forecasts to illustrate the potential of this target. We discuss how these constraints can be significantly improved by considering a more refined sample of molecular clouds near the Galactic Center and above the Galactic plane, a detailed modeling of the cosmic-ray ionization contribution and, potentially, a more refined analysis of the gas density in clouds through dust extinction maps. Thus, ionization of molecular clouds emerges as one of the most powerful tools for probing sub-keV dark matter.

    hep-phastro-ph.COastro-ph.GAastro-ph.HEPRD(2026)·9 citations
29. 29*

    Neural simulation-based inference of the Higgs trilinear self-coupling via off-shell Higgs production

    Aishik Ghosh🇺🇸 · Maximilian Griese🇩🇪 · Ulrich Haisch🇩🇪 · Tae Hyoun Park🇩🇪

    One of the forthcoming major challenges in particle physics is the experimental determination of the Higgs trilinear self-coupling. While efforts have largely focused on on-shell double- and single-Higgs production in proton-proton collisions, off-shell Higgs production has also been proposed as a valuable complementary probe. In this article, we design a hybrid neural simulation-based inference (NSBI) approach to construct a likelihood of the Higgs signal incorporating modifications from the Standard Model effective field theory (SMEFT), relevant background processes, and quantum interference effects. It leverages the training efficiency of matrix-element-enhanced techniques, which are vital for robust SMEFT applications, while also incorporating the practical advantages of classification-based methods for effective background estimates. We demonstrate that our NSBI approach achieves sensitivity close to the theoretical optimum and provide expected constraints for the high-luminosity upgrade of the Large Hadron Collider. While we primarily concentrate on the Higgs trilinear self-coupling, we also consider constraints on other SMEFT operators that affect off-shell Higgs production.

    hep-phhep-exphysics.data-anstat.MLEPJC(2026)·10 citations
30. 30*

    Probing Top Quark-Electron Interactions at Future Colliders

    Luigi Bellafronte🇺🇸 · Sally Dawson🇺🇸 · Pier Paolo Giardino🇪🇸 · Hongkai Liu🇺🇸

    Top quark interactions offer a window into possible new high scale physics and many models of new physics predict that the top quark interactions will deviate significantly from those predicted by the Standard Model (SM). We present an analysis of the experimental restrictions on anomalous 4-fermion $e^{+}{e}^{-}t\overline{t}$ operators that is accurate to next-to-leading order (NLO) in both the electroweak and QCD interactions within the Standard Model Effective Field Theory framework. At NLO, there is sensitivity to an extended set of anomalous interactions beyond those probed at leading order. A comparison of current limits from electroweak precision observables, along with expected future limits from Drell-Yan and $t\overline{t}{e}^{+}{e}^{-}$ production at the high luminosity LHC, from deep inelastic scattering at the EIC, and from projected sensitivities at the future FCC-ee and CEPC machines demonstrates that each of these programs extends the precision understanding of the interactions of top quarks.

    hep-phhep-exPRL(2025)·11 citations
31. 31*

    From Fluctuation to Polarization: Imprints of $O(1-10){\mathrm{Mpc}}^{-1}$ Curvature Perturbations in CMB B-modes from Scalar-Induced Gravitational Waves

    Aurora Ireland🇺🇸 · Kuver Sinha🇺🇸 · Tao Xu🇺🇸

    Probing primordial curvature perturbations on small scales, beyond those accessible using cosmic microwave background (CMB) primary anisotropies and Lyman-$\alpha$ forest data, remains a major open challenge. Current constraints on the scalar power spectrum at these scales are either weak or rely heavily on model-dependent assumptions about small-scale structure. In this work, we propose a novel method to probe the small-scale primordial power spectrum using scalar-induced tensor perturbations, which are inevitably sourced by curvature perturbations at second order in cosmological perturbation theory. While induced tensor modes have traditionally been studied in the context of the stochastic gravitational wave background, we highlight a complementary observable: the distinctive pattern of B-mode polarization they imprint on the CMB. We compute the angular spectrum of these B-modes arising from enhanced scalar perturbations and show that the resulting signal can be competitive with inflationary predictions for values of the tensor-to-scalar ratio targeted in upcoming CMB experiments, most notably CMB-Stage 4. We map the region of the scalar power spectrum to which these future B-mode experiments will be sensitive and compare with existing constraints, finding it to exceed current sensitivities at $k\sim O(1-10){\mathrm{Mpc}}^{-1}$. In addition to providing a new CMB-based probe of the small-scale power spectrum, this work also motivates dedicated B-mode searches at higher multipoles ($\ell \gtrsim 100$).

    hep-phastro-ph.COgr-qcJCAP(2025)·4 citations
32. 32*

    Enabling Thermal Dark Matter within the Vanilla $L_{\mu }$-$L_{\tau }$ Model

    Nicolás Bernal🇦🇪 · Jacinto P. Neto🇧🇷 · Javier Silva-Malpartida🇵🇪 · Farinaldo S. Queiroz🇧🇷

    Thermal dark matter is a compelling setup that has been probed by a multitude of experiments, mostly in the GeV-TeV mass range. The thermal paradigm in the sub-GeV range is about to experience the same experimental test with the next generation of low-energy accelerators and light dark matter detectors. Motivated by this, we investigate thermal dark matter in the $L_{\mu }-L_{\tau }$ and assess how the introduction of a matter-dominated era impacts the parameter that yields the correct relic density. Interestingly, we show that the projected experiments, such as MuSIC, FCC-ee, and LDMX, will probe a large region of the viable parameter space that yields the correct relic density. In the GeV-TeV mass regime, the usual large-scale detectors push the sensitivity. Our work highlights the rich interplay between early-universe dynamics, dark matter phenomenology, and the discovery potential of next-generation experiments.

    hep-phPRD(2025)·12 citations
33. 33*

    Stacking the Deck: Gambling on a Light QCD Axion

    Abhishek Banerjee🇺🇸 · Manuel A. Buen-Abad🇺🇸 · Anson Hook🇺🇸

    We consider axions lighter than what their QCD couplings might otherwise suggest. Starting with a ${\mathbb{Z}}_N$-axion, we introduce a small explicit ${\mathbb{Z}}_N$ symmetry-breaking coupling between the Standard Model Higgs boson and a reheaton. This small explicit breaking allows us to populate a large portion of the light axion $m_a$-$f_a$ plane, removes the $1/N$ tuning in the ${\mathbb{Z}}_N$-axion, and explains why only our sector was reheated. Due to finite temperature effects, axions of this sort undergo either ``rigged" misalignment, where the axion misalignment angle is effectively $\pi$ regardless of its initial value; or ``shuffled" misalignment, where the initial angle is effectively randomized.

    hep-phPRD(2025)·12 citations
34. 34*

    Cosmic Backgrounds in the Gravitational Standard-Model Extension

    C. M. Reyes🇨🇱 · C. Riquelme🇨🇱 · M. Schreck🇧🇷 · A. Soto🇬🇧

    We consider background fields within the gravitational sector of the Standard-Model Extension (SME) in a cosmological setting. Our analysis is divided into two parts. The first part addresses the consistency of nondynamical backgrounds in scenarios where diffeomorphism invariance is explicitly broken. Focusing on gravitational systems that admit Killing vector fields and possess a priori symmetries, we demonstrate that potential discrepancies between Riemannian geometry and dynamical equations can be avoided. The second part presents a direct application of various techniques developed by decomposing the modified Einstein equations along normal and tangential directions of the (3+1) decomposition. We show that nondynamical backgrounds can lead to accelerated cosmological expansion without requiring a cosmological constant, thereby opening new avenues for interpreting dark energy.

    ↳ gr-qchep-ph0 citations
35. 35*

    Impact of shape fluctuations on nuclear Schiff moments in heavy octupole-deformed nuclei

    E. F. Zhou · J. M. Yao🇨🇳 · J. Engel🇺🇸 · J. Meng🇨🇳

    Permanent electric dipole moments (EDMs) are among the most sensitive probes of CP violation beyond the Standard Model. In diamagnetic atoms, the EDM is determined primarily by the nuclear Schiff moment, whose uncertainty limits the interpretation of current and future EDM searches. For the experimentally most promising octupole-deformed nuclei, however, existing Schiff-moment calculations have largely relied on the rigid-shape approximation. Here we report the first fully microscopic beyond-mean-field study of Schiff moments in the heavy octupole-deformed nuclei ${}^{225}$Ra, ${}^{229}$Th, and ${}^{229}$Pa, based on multireference covariant density functional theory (MR-CDFT) with symmetry restoration and quadrupole--octupole shape mixing. The results show that collective shape fluctuations reduce the Schiff moments by factors of two to four. Furthermore, the Schiff moments of ${}^{229}$Th and ${}^{229}$Pa are predicted to exceed that of ${}^{225}$Ra by more than an order of magnitude, largely due to the near-degenerate parity doublets predicted by MR-CDFT. This work establishes a microscopic framework for calculating Schiff moments in heavy octupole-deformed nuclei, providing essential nuclear-structure input for ongoing and future EDM searches.

    ↳ nucl-thhep-phphysics.atom-ph7 citations
36. 36*

    Self-bound hybrid stars with strong phase transitions can relieve major compact star observation tensions

    Chen Zhang🇨🇳 · Juan M. Z. Pretel🇧🇷 · Renxin Xu🇨🇳

    Some recent pulsar observations cannot naturally fit into the conventional picture of neutron stars: the compact objects associated with HESS J1731-347 and XTE J1814-338 have too small radii in the low-mass regime, while the secondary component of GW190814 is too massive for neutron stars to be compatible with constraints from the GW170817 event. In this study, we demonstrate that all these anomalous observations and tensions, together with other conventional ones such as recent NICER observations of PSR J0740+6620, J0030+0451, and PSR J0437-4715, can be naturally explained simultaneously by a new general type of self-bound hybrid stars with large density discontinuities, and thus are radially stable in either the slow or rapid phase transition context. As a proof of concept, we use hybrid quark stars, inverted hybrid stars, and hybrid strangeon stars as benchmark examples to explicitly demonstrate the advantage and feasibility of self-bound hybrid stars with strong phase transitions in relieving all tensions related to compact stars' masses, radii, and tidal deformabilities.

    ↳ astro-ph.HEgr-qchep-phnucl-thPRD(2026)·13 citations
37. 37*

    Pion properties in isospin-asymmetric nuclear matter using in-medium chiral perturbation theory

    Kihong Kwon🇯🇵 · Yamato Suda🇯🇵 · Stephan Hübsch🇯🇵 · Daisuke Jido🇯🇵

    We compute the density dependence of in-medium pion properties, such as mass, wave function renormalization, and decay constant in the correlation function approach, and how they change under the influence of isospin-asymmetric nuclear matter. To this end, we use in-medium chiral perturbation theory to compute the relevant Feynman diagrams up to two-loop diagrams. Our results show that the isospin asymmetry of the nuclear matter splits these quantities into three separate values, corresponding to the three pions. Consequently, the tendency of each in-medium pion mass, wave function renormalization, and decay constant is dependent on the density and the neutron-to-proton ratio ${\rho }_n/{\rho }_p$ of nuclear matter. We also derive an in-medium Gell-Mann--Oakes--Renner relation which is valid for isospin-asymmetric nuclear matter and investigate to what extent it holds within our calculations.

    ↳ nucl-thhep-phPRC(2025)·1 citation
38. 38*

    Nuclear Physics Confronts Relativistic Collisions Of Isobars

    Giuliano Giacalone🇨🇭 · Jiangyong Jia🇺🇸 · Vittorio Somà🇫🇷 · You Zhou🇩🇰 · Anatoli Afanasjev🇺🇸 · Massimiliano Alvioli🇮🇹 · Benjamin Bally🇩🇪 · Federica Capellino🇩🇪 · Jean-Paul Ebran🇫🇷 · Hannah Elfner🇩🇪 · Fernando G. Gardim🇧🇷 · André V. Giannini🇧🇷 and 34 other authors

    High-energy collisions involving the $A=96$ isobars ${}^{96}$Zr and ${}^{96}$Ru have been performed in 2018 at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) as a means to search for the chiral magnetic effect in QCD. This would manifest itself as specific deviations from unity in the ratio of observables taken between ${}^{96}$Zr+${}^{96}$Zr and ${}^{96}$Ru+${}^{96}$Ru collisions. Measurements of such ratios (released at the end of 2021) indeed reveal deviations from unity, but these are primarily caused by the two collided isobars having different radial profiles and intrinsic deformations. To make progress in understanding RHIC data, nuclear physicists across the energy spectrum gathered in Heidelberg in 2022 as part of an EMMI Rapid Reaction Task Force (RRTF) to address the following question. Does the combined effort of low-energy nuclear structure physics and high-energy heavy-ion physics enable us to understand the observations made in isobar collisions at RHIC?

    ↳ nucl-exhep-exhep-phnucl-th27 citations
39. 39*

    Numerical treatment of annual modulation of relic neutrinos

    Fabian Zimmer🇳🇱 · Shin'ichiro Ando🇳🇱

    We present a numerical treatment of the annual modulation of relic neutrinos due to the Sun's gravitational influence. Extending our previously developed N-1-body simulation framework from Milky Way scales to solar system dynamics, we model how cosmic neutrino background densities might vary throughout Earth's orbital cycle. We validate our numerical approach against analytical expectations from previous studies that assumed idealized relic neutrino populations. Our results suggest that the prior gravitational history of neutrinos traversing asymmetric dark matter distributions can affect annual modulation patterns. While our simulations reproduce modulation amplitudes similar to analytical predictions for heavier neutrinos, we find that the amplitude can vary considerably depending on the specific morphology of dark matter halos. These findings highlight the importance of incorporating realistic structure formation effects when predicting potential observational relic neutrino signatures.

    ↳ astro-ph.COhep-phJCAP(2025)·3 citations
40. 40*

    Toward graviton detection via photon-graviton quantum state conversion

    Taiki Ikeda🇯🇵 · Youka Kaku🇯🇵 · Sugumi Kanno🇯🇵 · Jiro Soda🇯🇵

    A magnetic field enables the interconversion of photons and gravitons, yet the process is usually analysed only at the level of classical wave equations. We revisit photon-graviton conversion in a quantum field theoretic framework, allowing us to track the evolution of arbitrary quantum states. Treating the photons as squeezed coherent states and the gravitons as the squeezed vacuum expected for primordial gravitational waves, we derive analytic expressions for the conversion probability and show that it can be significantly enhanced compared to the conventional estimate. We further demonstrate that the conversion both swaps preexisting entanglement and generates genuinely new entanglement between the electromagnetic and gravitational sectors, which is impossible in any classical description. Detecting such nonclassical correlations would constitute compelling evidence for the quantization of gravity and offers a novel pathway toward graviton detection.

    ↳ quant-phgr-qchep-phhep-thPRD(2025)·11 citations
41. 41*

    Tidal Suppression of Fuzzy Dark Matter Heating in Milky Way Satellite Galaxies

    Yu-Ming Yang🇨🇳 · Zhao-Chen Zhang🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳

    Many previous studies have imposed stringent constraints on the particle mass of fuzzy dark matter (FDM) by analyzing observations of Galactic satellite galaxies, which show no significant evidence of the heating effect predicted by FDM. However, these analyses have generally neglected the tidal influence of the Milky Way, which can substantially suppress the FDM-induced heating effect in satellites. This oversight arises from computational challenges of accurately capturing the tidal effects in FDM simulations. In this study, we present a novel simulation framework that, for the first time, enables the simulation of an FDM-stellar system within an observationally motivated gravitational potential of the Milky Way. This framework incorporates the diverse Galactic components, including the gravitational influence of the Large Magellanic Cloud. Using the Fornax dwarf galaxy as a case study, we demonstrate that tidal effects significantly alleviate the tension between observational data and the predicted heating effect for an FDM particle mass of $m_a\sim 10^{-22}$ eV.

    ↳ astro-ph.COastro-ph.GAhep-phApJL·13 citations
42. 42*

    Superradiant Axionic Black-Hole Clouds as Seeds for Graviton Squeezing

    Panagiotis Dorlis🇬🇷 · Nick E. Mavromatos🇬🇷 · Sarben Sarkar🇬🇧 · Sotirios-Neilos Vlachos🇬🇷

    It is shown that both, standard general relativity (GR) and Chern-Simons (CS) gravity, the latter containing chiral gravitational anomaly terms, seed the production of pairs of entangled gravitons in a multi-mode squeezed state. This involves the interaction of gravitons with the axionic cloud surrounding a superradiant Kerr (rotating) black hole background. The order of magnitude of the squeezing effect, specifically the number of graviton excitations in the squeezed vacuum, is estimated in the non-relativistic limit, relevant for the superradiance process. It is found analytically that the squeezing from the GR process of annihilation of two axions into two gravitons, dominates, by many orders of magnitude, that coming from the axion decay into two gravitons, induced by the higher-derivative CS term. It is also shown that significant squeezing effects are produced in the case of long-lived axionic clouds, whose lifetimes are much longer than the timescale for which superradiance is effective. A brief discussion on current exclusion (for the first time) of very-long axion-cloud lifetimes, through comparison of our results with current LIGO data, as well as potential detection of such effects in future interferometers is also given

    ↳ gr-qchep-phhep-thquant-phPRL(2025)·20 citations
43. 43*

    Energy momentum tensor correlators in ${\varphi }^4$ theory II: The spin-two sector

    Nikos Irges🇬🇷 · Leonidas Karageorgos🇬🇷

    We extend the computation of the C_T charge of the 2-point function of the Energy-Momentum Tensor to 4-loops. We show that C_T decomposes into two sectors, the conformal sector, which encodes the value of the central charge at fixed points and an RG-sector that contains logarithmic and constant corrections proportional to the beta-function. This latter constitutes the main new result of this work and is inaccessible via CFT methods alone. Furthermore, we demonstrate that C_T satisfies an eigenvalue-like equation analogous to that of the spin-0 charge, as discussed in part I, though with a different in general eigenvalue. Finally we present three possible applications.

    ↳ hep-thhep-phNPB(2025)·0 citations
44. 44*

    Neutrino mass tension or suppressed growth rate of matter perturbations?

    William Giarè🇬🇧 · Olga Mena🇪🇸 · Enrico Specogna🇬🇧 · Eleonora Di Valentino🇬🇧

    Assuming a minimal $\Lambda$CDM cosmology with three massive neutrinos, the joint analysis of Planck cosmic microwave background data, DESI baryon acoustic oscillations, and distance moduli measurements of Type Ia supernovae from the Pantheon+ sample sets an upper bound on the total neutrino mass, $\sum m_{\nu }\lesssim 0.06$-$0.07$ eV, that lies barely above the lower limit from oscillation experiments. These constraints are mainly driven by mild differences in the inferred values of the matter density parameter across different probes that can be alleviated by introducing additional background-level degrees of freedom (e.g., by dynamical dark energy models). However, in this work we explore an alternative possibility. Since both ${\Omega }_{\mathrm{m}}$ and massive neutrinos critically influence the growth of cosmic structures, we test whether the neutrino mass tension may originate from the way matter clusters, rather than from a breakdown of the $\Lambda$CDM expansion history. To this end, we introduce the growth index $\gamma$, which characterizes the rate at which matter perturbations grow. Deviations from the standard $\Lambda$CDM value ($\gamma \simeq 0.55$) can capture a broad class of models, including non-minimal dark sector physics and modified gravity. We show that allowing $\gamma$ to vary significantly relaxes the neutrino mass bounds to $\sum m_{\nu }\lesssim 0.13$-$0.2$ eV, removing any tension with terrestrial constraints without altering the inferred value of ${\Omega }_{\mathrm{m}}$. However, this comes at the cost of departing from standard growth predictions: to have $\sum m_{\nu }\gtrsim 0.06$ eV one needs $\gamma >0.55$, and we find a consistent preference for $\gamma >0.55$ at the level of $\sim 2\sigma$. This preference increases to $\sim 2.5$-$3\sigma$ when a physically motivated prior $\sum m_{\nu }\ge 0.06$ eV from oscillation experiments is imposed.

    ↳ astro-ph.COgr-qchep-phPRD(2025)·35 citations
45. 45*

    Nonlinearities in Kerr Black Hole Ringdown from the Penrose Limit

    D. Perrone🇨🇭 · A. Kehagias🇬🇷 · A. Riotto🇨🇭

    We provide a fully analytical approach to calculate the nonlinearities of the gravitational waves in the ringdown of a Kerr black hole in the eikonal limit. The corresponding quasi-normal modes are associated to the orbits of a closed circular null geodesic and the problem can be analyzed by taking the Penrose limit around it. We calculate analytically the amplitude and the phase of the quadratic quasi-normal modes as well as its dependence on the black hole spin.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2025)·16 citations
46. 46*

    Universal lower bound on the axion decay constant from free streaming effects

    Keisuke Harigaya🇺🇸 · Wayne Hu🇺🇸 · Rayne Liu🇺🇸 · Huangyu Xiao🇺🇸

    We show that enhancement of the axion relic abundance compared to the standard misalignment contribution generically leads to the production of nonzero momentum axion modes, resulting in warm dark matter behavior and enhanced isocurvature perturbations. It leads to universal constraints on the axion parameter space that are independent of detailed model assumptions and cosmological history. For models enhancing relic abundance with gradient axion modes, observations of the Lyman-$\alpha$ forest impose a lower bound on the axion decay constant, $f_a\gtrsim 10^{15}\mathrm{GeV}(10^{-18}\mathrm{eV}/m_a)$, from the free-streaming effect. For models relying on the delay of coherent axion oscillations, we obtain a slightly weaker bound, $f_a\gtrsim 10^{14}\mathrm{GeV}(10^{-18}\mathrm{eV}/m_a)$. We make relatively conservative choices to establish these universal bounds but also provide scaling parameters that can be calibrated for stronger constraints in concrete models and updated as observations improve.

    ↳ astro-ph.COhep-phPRD(2025)·13 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.