Fri·Apr 3, 2026Friday·April 3, 2026

1. 01*

   Q-balls across dimensions

   Dusty Aiello🇺🇸 · Julian Heeck🇺🇸

   Scalars carrying a conserved global charge $Q$ can form stable localized field configurations composed of a large number of particles. These non-topological solitons are spherically symmetric and are called Q-balls. While usually analyzed in three spatial dimensions, these solitons can be straightforwardly generalized to $d$ spatial dimensions. For $d=1$, we can analytically solve the non-linear differential equation for an important class of single-field potentials; for $d>1$, we can analytically approximate the solutions in the thin-wall or large Q-ball regime, including the first sub-leading correction consistently. Since the underlying differential equations have the same form as vacuum-decay bounce solutions, our results find applications there, too.

   hep-phhep-thPRD(2026)·1 citation
2. 02*

   Constraints on High-Frequency Gravitational Waves from Graviton-Photon Conversion in the M87 Galaxy

   Aman Gupta🇮🇳 · Pratik Majumdar🇮🇳 · Sourov Roy🇮🇳 · Pratick Sarkar🇮🇳

   High-frequency gravitational waves, particularly in the range $f\gtrsim 10^{10}\mathrm{Hz}$, represent a compelling probe of physics beyond the Standard Model. Due to the absence of direct detection methods in this frequency regime, alternative strategies may be pursued. One promising approach involves the conversion of gravitons into photons in the presence of magnetic fields, a process known as the inverse Gertsenshtein effect. In this study, we explore such graviton-to-photon conversions occurring within the magnetic field environment of the M87 galaxy, utilizing realistic models for the galactic magnetic field and plasma density structure. We use the broadband electromagnetic spectrum of M87, ranging from millimeter to TeV gamma rays, to search for hidden contributions from graviton-photon conversions. In the well-constrained frequency range $10^{10}$-$10^{27}\mathrm{Hz}$, the lack of excess emission allows us to place improved bounds on the gravitational wave strain amplitude $h_c$ or on spectral energy density ${\Omega }_{\mathrm{gw}}{h}^2$. We find that our results from M87 yield substantially stronger constraints compared to existing bounds derived from Milky Way magnetic field considerations, with improvements ranging from one to five orders of magnitude depending on the frequency band, thereby enhancing the prospects for probing high-frequency gravitational wave backgrounds through indirect electromagnetic signatures.

   hep-phastro-ph.HEPRD(2026)·2 citations
3. 03*

   Supermassive Primordial Black Holes from a Catalyzed Dark Phase Transition for Little Red Dots

   Jinhui Guo🇨🇳 · Jia Liu🇨🇳 · Masanori Tanaka🇨🇳 · Xiao-Ping Wang🇨🇳 · Huangyu Xiao🇺🇸

   JWST has revealed an abundant population of compact, low-metallicity "Little Red Dots" (LRDs) at high redshift, challenging conventional scenarios in which supermassive black holes (SMBHs) grow from stellar-mass seeds. We consider a scenario in which the SMBHs are instead supermassive primordial black holes (SMPBHs), formed directly in a decoupled, subdominant dark sector undergoing a first-order phase transition. Unlike conventional stochastic phase transitions, our mechanism is based on the catalysis by domain walls (DWs): most of the Universe completes the transition rapidly, while rare long-lived false-vacuum domains survive because of DW statistics and collapse into PBHs. This mechanism naturally yields SMPBH seeds with masses up to $M_{\mathrm{PBH}}\sim \mathcal{O}(10^{10})M_{\odot }$, whose abundance can account for the observed LRD population. It also avoids the usual tensions with phase transition completion, $\Delta N_{\mathrm{eff}}$, and large curvature perturbations. The dark phase transition simultaneously generates an ultra-low-frequency stochastic gravitational-wave background peaking near the pulsar-timing-array range, providing a test of this dark-sector origin of LRDs.

   hep-phastro-ph.COastro-ph.GA4 citations
4. 04*

   Bipartite Solution to the Lithium Problem

   Sougata Ganguly🇰🇷 · Tae Hyun Jung🇰🇷 · Tae-Sun Park🇰🇷 · Chang Sub Shin🇰🇷

   The primordial lithium problem remains a persistent motivation for new-physics modifications of Big Bang nucleosynthesis, yet the precision of the observed deuterium abundance now places strong constraints on such attempts. This indicates that the challenge is not simply to reduce ${}^7\mathrm{Li}$, but to realize the correlated shifts among light-element abundances required to do so without spoiling deuterium. We investigate this issue in a concrete two-step decay scenario involving two unstable particles undergoing sequential late decays. In the first stage, a majoron with lifetime ${\tau }_J\sim 10\text{–}10^4\sec$ decays predominantly into neutrinos, increasing the neutron abundance and thereby reducing the primordial ${}^7\mathrm{Li}+{}^7\mathrm{Be}$ yield. This mechanism, however, simultaneously drives deuterium above the observationally allowed range. In the second stage, an axion-like particle with a longer lifetime ${\tau }_{\varphi }\gtrsim 10^5\sec$ decays into photons, inducing late-time photodissociation that compensates the excess deuterium without erasing the earlier reduction of lithium, while further amplifying the depletion of ${}^7\mathrm{Li}+{}^7\mathrm{Be}$. Although the setup is model-dependent, it serves as an explicit proof of concept that the lithium abundance can be lowered consistently with current deuterium constraints. More broadly, our analysis highlights that a viable resolution may require a nontrivial combination of decay channels and decay epochs, and clarifies the pattern of abundance response that successful late-decay scenarios must achieve.

   hep-phastro-ph.CO0 citations
5. 05*

   A model independent method for measurement of $B^{\pm }$ and $B^0$ meson production fractions at ${\rm Y}(4S)$

   Murad Yasaveev🇷🇺 · Pavel Pakhlov🇷🇺 · Nikolai Peters🇷🇺 · Alena Mufazalova🇷🇺

   This paper presents a detailed description of a model-independent method for the direct measurement of the ${\rm Y}(4S)\to B^{+}{B}^{-}$ and ${\rm Y}(4S)\to B^0{\bar{B}}^0$ production fractions at $B$ factories. The method is based on counting single- and double-inclusive charmed meson production at the ${\rm Y}(4S)$ resonance, providing statistical tagging of $B^0{\bar{B}}^0$ and $B^{+}{B}^{-}$ events. A feasibility study indicates that a precision comparable to the current world average can be achieved without making any underlying assumptions, as the calculations rely solely on event yields.

   hep-phJHEP(2026)·0 citations
6. 06*

   Quark masses and mixing from Modular $S_4^{\prime }$ with Canonical Kähler Effects

   Ivo de Medeiros Varzielas🇵🇹 · Manuel Paiva🇵🇹

   We propose a quark flavor model based on modular $S_4^{\prime }$ with a general CP symmetry. CP violation in the quark sector is entirely realized by the modulus $⟨\tau ⟩$. We show that the canonical normalization induced by the Kähler metric plays a crucial role in reproducing the observed hierarchies, while maintaining coupling constants of order $\mathcal{O}(1)$. The minimal model achieves a great fit to the quark sector data, which we take as the PDG 2024 data extrapolated to the GUT scale.

   hep-phJHEP(2026)·1 citation
7. 07*

   New physics in multi-lepton tau decays

   Yohei Ema🇨🇭 · Patrick J. Fox🇺🇸 · Matheus Hostert🇺🇸 · Tony Menzo🇺🇸 · Maxim Pospelov🇺🇸 · Anupam Ray🇨🇦 · Jure Zupan🇺🇸

   Dark particles with lepton-flavor-violating couplings to the tau lepton can induce rare neutrinoless $\tau$ decays with large final state multiplicities. We study models where transitions of the type ${\tau }^{\pm }\to {\ell }^{\pm }\varphi$, with $\varphi$ a light new particle, initiate a chain of decays in the dark sector that terminate with decays into electrons, muons, or pions. These decay cascades appear as rare five or even seven-body $\tau$ decays with multiple reconstructable resonances. We survey several representative models: kinetically mixed dark photon, gauged $L_i-L_j$ models, and other more exotic charge assignments such as chiral $U(1{)}^{\prime }$ extensions of the Standard Model. The main new ingredient is the possibility of flavor violation at very high scales. In these models, a number of channels that have not yet been searched for experimentally, such as $\tau \to 5\mu$, $\tau \to 3\mu 2e$, $\tau \to \mu 4e$, and hadronic channels like $\tau \to \mu 4\pi$, typically dominate over the previously-considered signatures such as $\tau \to 3\mu$. While some of the models, such as the gauged $L_i-L_j$ ones, also contain more challenging channels with missing energy due to decays to neutrinos, they can still be searched for via fully visible channels.

   hep-phhep-ex0 citations
8. 08*

   Phase-space integrals through Mellin-Barnes representation

   Taushif Ahmed🇩🇪 · Syed Mehedi Hasan🇩🇪 · Andreas Rapakoulias🇩🇪

   We compute angular phase-space integrals with three and four denominators analytically, working within dimensional regularisation via the Mellin-Barnes (MB) representation. The approach converts multifold MB integrals into real parametric integrals and expresses all results in terms of Goncharov polylogarithms (GPLs). For three denominators, all-massless results are obtained to $\mathcal{O}({ϵ}^2)$ and the single-massive case to $\mathcal{O}(ϵ)$; for four denominators, both the massless and single-massive cases are solved to $\mathcal{O}({ϵ}^0)$. Integrals with multiple massive momenta follow from a partial fraction decomposition reducing them to the single-massive case. Recursion relations relating integrals with higher denominator powers to master integrals are derived. These are essential ingredients to solving full phase-space integrals.

   hep-phhep-th0 citations
9. 09*

   Vacuum bubbles from cosmic ripples

   Zi-Yan Yuwen🇰🇷 · Rong-Gen Cai🇨🇳 · Shao-Jiang Wang🇨🇳

   We investigate vacuum decays in the early Universe in the presence of curvature perturbations. For sufficiently large perturbations associated with over-densities, we find that the bounce solution develops an oscillating middle stage near the bubble wall. For small perturbations, we analytically show within the thin-wall approximation that an over- (under-) density would enhance (suppress) the vacuum decay rate with a smaller (larger) initial bubble radius. By numerically solving for the bounce solutions and evaluating the corresponding Euclidean action, we further confirm this behaviour in thick-wall cases. Our results indicate that over-densities can generically trigger vacuum decay at an earlier moment.

   hep-phastro-ph.COgr-qcJHEP(2026)·1 citation
10. 10*

    Higgs production in association with a Z boson at TeV-scale lepton colliders

    Hiroyuki Furusato🇯🇵 · Satsuki Hosoya🇯🇵 · Kentarou Mawatari🇯🇵 · Shouta Suzuki🇯🇵

    We study the $l^{-}{l}^{+}\to \nu \bar{\nu }Zh$ process for future lepton colliders, whose cross section becomes larger than that for $l^{-}{l}^{+}\to Zh$ in the energy region above a few TeV. We classify the amplitudes into three main groups based on the topology of each Feynman diagram; vector boson scattering, $l^{-}{W}^{+}$ scattering, and $W^{-}{l}^{+}$ scattering, and study the interference patterns among the amplitudes. We show that subtle gauge cancellation among the amplitudes at high energies in the unitary gauge is absent in the recently proposed Feynman-diagram gauge, and the physical distributions can be interpreted by the contributions from each subgroup. We also find that the interference patterns in kinematical distributions of the Z boson can be understood by those in the $l^{-}{l}^{+}\to \nu \bar{\nu }Z$ process.

    hep-phEur.Phys.J.Plus(2026)·0 citations
11. 11*

    Exclusive semileptonic and nonleptonic $J/\psi$ decays

    V. O. Galkin🇷🇺 · I. S. Sukhanov🇷🇺

    Exclusive semileptonic and nonleptonic $J/\psi$ decays are investigated in the framework of the relativistic quark model based on the quasipotential approach and quantum chromodynamics. The form factors parameterizing the hadronic matrix element of the weak current are calculated with the complete account of the relativistic effects. These form factors are expressed as the overlap integrals of the meson wave functions and are determined in the whole accessible kinematic range. On this basis the semileptonic decay branching fractions are evaluated for decays involving both electrons and muons. The nonleptonic decays are considered in the factorization approximation in the limit for the number of colors $N_c\to \infty$. The obtain branching fractions are found to be of the order $10^{-9}\sim 10^{-12}$. They are compared with the previous theoretical predictions and available experimental upper bounds.

    hep-phhep-exPRD(2026)·0 citations
12. 12*

    The scaling Pomeron

    R. Peschanski🇫🇷 · B. G. Giraud🇫🇷

    We examine the Regge theoretical properties for the scaling observed in pp elastic scattering differential cross-sections at the LHC. A positive signature amplitude (i.e. the Pomeron) with scaling properties has been derived. It is found to describe the dip-bump region of momentum transfer at LHC energies in agreement with data. We derive the analytic continuation in the whole plane of the t-channel partial waves of index $l_t$ specific to the Regge formalism. The analytic form of the amplitude exhibits a specific scaling property without singularities, except for a series of poles in the $l_t$ real axis at fractional values.

    hep-phhep-thActa Phys.Polon.B(2026)·0 citations
13. 13*

    Tetraquark-Jet Systems at the High-Luminosity LHC

    Francesco Giovanni Celiberto🇪🇸

    We investigate the high-energy production of tetraquark-jet systems at the LHC and its forthcoming High-Luminosity upgrade. In this review, we examine the leading-power fragmentation of fully heavy tetraquarks ($T_{4Q}$) in hadronic collisions, highlighting their relevance as novel probes of multiquark dynamics in QCD. Our analysis relies on the hadron-structure-oriented TQ4Q1.1 fragmentation functions, built within a nonrelativistic QCD framework that incorporates both gluon- and heavy-quark-initiated channels. Threshold-consistent DGLAP evolution is performed through the HF-NRevo scheme, enabling a unified treatment of mass thresholds and scale variations. We also provide a systematic discussion of uncertainties arising from color-composite long-distance matrix elements (LDMEs) and from perturbative hard- and fragmentation-scale inputs (H- and F-MHOUs). Phenomenological predictions are obtained using the (sym)Jethad framework at NLL/NLO${}^{+}$ accuracy for semi-inclusive tetraquark-jet production at the LHC and beyond. This review connects the emerging spectroscopy of fully heavy exotics with modern fragmentation-based approaches to hadron structure and high-energy QCD.

    hep-phhep-exhep-thnucl-ex+1Universe(2026)·7 citations
14. 14*

    Heavy-Flavor Fragmentation: The QCD Portal to Exotic Matter

    Francesco Giovanni Celiberto🇪🇸

    We investigate the core dynamics behind exotic matter formation via the TQ4Q1.1 set of collinear fragmentation functions for fully charmed or bottomed tetraquarks in three quantum configurations: scalar ($0^{++}$), axial vector ($1^{+-}$), and tensor ($2^{++}$). We adopt leading-power single-parton fragmentation within a nonrelativistic QCD framework tailored to tetraquark Fock states. Initial-scale inputs are constructed from updated gluon- and heavy-quark channels, and evolved through threshold-consistent DGLAP within HF-NRevo. We present the first systematic propagation of uncertainties from color-composite long-distance matrix elements governing tetraquark hadronization. This study advances the connection between hadronic structure, precision QCD, and exotic matter.

    hep-phhep-exhep-thnucl-ex+1Acta Phys.Polon.Supp.(2026)·4 citations
15. 15*

    Triply Heavy $\Omega$ Baryons with JETHAD: A High-Energy Viewpoint

    Francesco Giovanni Celiberto🇪🇸

    We investigate the leading-power fragmentation of triply heavy $\Omega$ baryons in high-energy hadronic collisions. Extending our previous work on the ${\Omega }_{3c}$ sector, we release the full OMG3Q1.0 family of collinear fragmentation functions by completing the description of the charm channel and delivering the novel ${\Omega }_{3b}$ functions. These hadron-structure-oriented functions are constructed from improved proxy-model calculations for heavy-quark and gluon fragmentation, matched to a flavor-aware DGLAP evolution based on the HF-NRevo scheme. For phenomenological applications, we employ the (sym)JETHAD multimodular interface to compute and analyze NLL/NLO${}^{+}$ semi-inclusive ${\Omega }_{3Q}$ plus jet distributions at the HL-LHC and FCC. This work consolidates the link between hadron structure, rare baryon production, and resummed QCD at the energy frontier.

    hep-phhep-exhep-thnucl-ex+1Symmetry(2026)·9 citations
16. 16*

    The Axion Helical Misalignment Mechanism

    Wei Chao🇨🇳 · Chang-Jie Dai🇨🇳

    Understanding axion production in the early Universe remains a pivotal challenge, given the axion as a compelling cold dark matter candidate. Conventional misalignment scenarios often overlook the possibility that a large initial axion velocity can fundamentally reshape the subsequent evolution of the axion field. In this letter, we provide a comprehensive analysis of how primordial magnetic fields impact the axion relic abundance. By accounting for the axion coupling to the Chern-Simons term of the hypercharge gauge field, the equation of motion of the axion is recast as a driven oscillator equation. This modification effectively shifts the onset of axion oscillations, leading to a significant reevaluation of the final relic abundance, a novel effect we term the axion helical misalignment mechanism. Furthermore, in the presence of primordial chiral asymmetries, the chiral magnetic effect (CME) emerges as a critical driver of axion dynamics. The interplay between the axion field and the CME not only profoundly influences the evolution of Standard Model chiral fermions but also provides a viable pathway for generating the observed baryon asymmetry of the Universe.

    hep-phastro-ph.CO0 citations
17. 17*

    Localized Steps toward ACT-Favored Inflation

    Kai-Ge Zhang🇨🇳 · Chengjie Fu🇨🇳 · Jian-Feng He🇨🇳 · Zong-Kuan Guo🇨🇳

    Recent ACT measurements favor a scalar spectral index larger than the Planck value, posing a challenge to many single-field slow-roll inflation models. We show that a smooth, localized step in the inflaton potential can shift the predicted scalar spectral index and tensor-to-scalar ratio by displacing the field value at which the CMB pivot scale exits the horizon. This mechanism can move monomial and, in particular, plateau-like attractor models toward the ACT-favored region, whereas the induced shift remains insufficient in natural inflation. We derive semi-analytical expressions for the step-induced remapping and quantify the associated effective e-fold shift, finding that it can be comparable to, and in some cases exceed, the shift allowed by conservative reheating uncertainties.

    hep-phastro-ph.CO4 citations
18. 18*

    Many Wrongs Make a Right: Leveraging Biased Simulations Towards Unbiased Parameter Inference

    Ezequiel Alvarez🇦🇷 · Sean Benevedes🇺🇸 · Manuel Szewc🇦🇷 · Jesse Thaler🇺🇸

    In particle physics, as in many areas of science, parameter inference relies on simulations to bridge the gap between theory and experiment. Recent developments in simulation-based inference have boosted the sensitivity of analyses; however, biases induced by simulation-data mismodeling can be difficult to control within standard inference pipelines. In this work, we propose a Template-Adapted Mixture Model to confront this problem in the context of signal fraction estimation: inferring the population proportion of signal in a mixed sample of signal and background, both of which follow arbitrarily complex distributions. We harness many biased simulations to perform data-driven estimates of each process distribution in the signal region, substantially reducing the bias on the signal fraction due to the domain shift between simulation and reality. We explore different methodological choices, including model selection, feature representation, and statistical method, and apply them to a Gaussian toy example and to a semi-realistic di-Higgs measurement. We find that the presented methods successfully leverage the biased simulations to provide estimates with well-calibrated uncertainties.

    hep-phhep-exphysics.data-anstat.ME1 citation
19. 19*

    Search for dark photons at future e${}^{+}$e${}^{-}$ colliders

    Mikael Berggren (1) ((1) DESY, Hamburg, Germany)🇩🇪

    In a class of theories, dark matter is explained by postulating the existence of a `dark sector', which interacts gravitationally with ordinary matter. If this dark sector contains a U(1) symmetry, and a corresponding `dark' photon ($A_D$) , it is natural to expect that this particle kineticly mix with the ordinary photon, and hence become a `portal' through which the dark sector can be studied. The strength of the mixing is given by a mixing parameter $(ϵ)$. This same parameter governs both the production and the decay of the $A_D$ back to SM particles, and for values of $ϵ$ not already excluded, the signal would be a quite small, and quite narrow resonance: If $ϵ$ is large enough to yield a detectable signal, its decay width will be smaller than the detector resolution, but so large that the decay back to SM particles is prompt. For masses of the dark photon above the reach of Belle II, future high energy e${}^{+}$e${}^{-}$ colliders are ideal for searches for such a signal, due to the low and well-known backgrounds, and the excellent momentum resolution and equally excellent track-finding efficiency of the detectors at such colliders. This contribution will discuss a study investigating the dependency of the limit on the mixing parameter and the mass of the $A_D$ using the $A_D\to {\mu }^{+}{\mu }^{-}$ decay mode in the presence of standard model background, using fully simulated signal and background events in the ILD detector at the ILC Higgs factory. In addition, a more general discussion about the capabilities expected for generic detectors at e${}^{+}$e${}^{-}$ colliders operating at other energies will be given.

    hep-phEur.Phys.J.Plus(2026)·0 citations
20. 20*

    Highly suppressed detection probability of the primordial antimatter in the present-day universe

    Yi Yang🇹🇼 · Wai Bong Yeung🇹🇼

    We show that the matter-antimatter asymmetry in the present-day universe is mainly due to the highly suppressed detection probability for the primordial antimatter, which is a direct result of the Dirac-Feynman-Stueckelberg interpretation of antimatter and the extremely time asymmetric expansion of the primordial universe.

    hep-phChin.J.Phys.(2022)·0 citations
21. 21*

    The Holographic QCD Axion in Five Dimensions

    Csaba Csáki🇺🇸 · Eric Kuflik🇮🇱 · Wei Xue🇺🇸 · Taewook Youn🇺🇸

    We present a holographic construction of the QCD axion based on a warped 5D model. A key ingredient of our setup is the introduction of a bulk scalar field $\theta$, which is holographically dual to the topological operator of QCD. This makes the relation among the axion, the ${\eta }^{\prime }$, and the anomalies transparent. We identify the bulk modes corresponding to the ${\eta }^{\prime }$ and axion states, and show that an adjustment analogous to that of the usual 4D axion takes place. We identify the origin of the axion quality problem in this framework and show that a large degree of axion compositeness is needed to solve it. We also find that, in the limit of a high quality axion, the physical axion state is predominantly contained in the bulk gauge field.

    hep-phhep-th8 citations
22. 22*

    The Black Hole Mass Gap as a New Probe of Millicharged Particles

    Damiano F. G. Fiorillo🇩🇪 · Giuseppe Lucente🇺🇸 · Jeremy Sakstein🇺🇸 · Edoardo Vitagliano🇮🇹 · Matteo Cantiello🇺🇸

    We investigate the impact of millicharged particles (MCPs) on massive stars undergoing pulsational pair-instability supernovae and on the location of the lower edge of the black hole mass gap. We find that energy losses due to MCP emission weaken the pulsations, allowing the star to retain more mass and thereby shifting the lower edge of the mass gap to higher black hole masses. The mass gap is sensitive to a region of MCP parameter space with masses $35\mathrm{keV}\lesssim m_{\chi }\lesssim 200\mathrm{keV}$ and charges $10^{-10}\lesssim q\lesssim 10^{-9}$, which remains unconstrained by existing astrophysical probes. If confirmed, recent gravitational wave observations placing the lower edge of the mass gap near $45{\mathrm{M}}_{\odot }$ would translate directly into bounds on this parameter space.

    hep-phastro-ph.COastro-ph.HE3 citations
23. 23*

    Generative models on phase space

    Zachary Bogorad🇺🇸 · Ibrahim Elsharkawy🇨🇦 · Yonatan Kahn🇨🇦 · Andrew J. Larkoski🇺🇸 · Noam Levi🇮🇱

    Deep generative models such as diffusion and flow matching are powerful machine learning tools capable of learning and sampling from high-dimensional distributions. They are particularly useful when the training data appears to be concentrated on a submanifold of the data embedding space. For high-energy physics data, consisting of collections of relativistic energy-momentum 4-vectors, this submanifold can enforce extremely strong physically-motivated priors, such as energy and momentum conservation. If these constraints are learned only approximately, rather than exactly, this can inhibit the interpretability and reliability of such generative models. To remedy this deficiency, we introduce generative models which are, by construction, confined at every step of their sampling trajectory to the manifold of massless N-particle Lorentz-invariant phase space in the center-of-momentum frame. In the case of diffusion models, the "pure noise" forward process endpoint corresponds to the uniform distribution on phase space, which provides a clear starting point from which to identify how correlations among the particles emerge during the reverse (de-noising) process. We demonstrate that our models are able to learn both few-particle and many-particle distributions with various singularity structures, paving the way for future interpretability studies using generative models trained on simulated jet data.

    hep-phcs.AI3 citations
24. 24*

    Millicharged Particle Production During Late-Stage Stellar Evolution

    Damiano F. G. Fiorillo🇩🇪 · Giuseppe Lucente🇺🇸 · Jeremy Sakstein🇺🇸 · Edoardo Vitagliano🇮🇹

    Stars are natural sources of feebly interacting particles, including putative particles with mass $m_{\chi }$ and electric charge $qe$. The emission of such millicharged particles (MCPs) causes an energy loss which can alter stellar evolution. While MCP production rates have been computed for different plasma parameters, they have yet to be derived for the conditions relevant to late stages of stellar evolution, in which the temperature can reach values $T\simeq 10-100\mathrm{keV}$ while the plasma frequency is ${\omega }_{\mathrm{pl}}\ll T$. In this paper, we compute the MCP energy-loss rates relevant for pre-supernova objects, finding three different regimes in which the dominant processes are respectively plasmon decay ($m_{\chi }<{\omega }_{\mathrm{pl}}/2$), Compton-like scattering ($m_{\chi }>{\omega }_{\mathrm{pl}}/2$, $T\lesssim 0.5\mathrm{MeV}$), and electron-positron annihilation. We obtain semi-analytical fits for the energy-loss rates suitable for implementation in stellar evolution codes.

    hep-phastro-ph.COastro-ph.HE1 citation
25. 25*

    Imprint of matter-antimatter asymmetry on collapsing domain walls

    Dipendu Bhandari🇮🇳 · Debasish Borah🇮🇳 · Indrajit Saha🇮🇳

    Spontaneous breaking of discrete symmetries play non-trivial role in many well-motivated particle physics models. However, it leads to a network of cosmologically unwanted domain walls (DWs) which can be made unstable by introducing a bias term in the scalar potential. In this letter, we provide a novel origin of such bias terms at finite temperature due to radiative corrections from a Dirac fermion with large asymmetry $\sim \mathcal{O}(0.1)$ in its number density. In addition to getting a new viable region of parameter space for collapsing DWs not explored previously and resulting gravitational waves (GWs) accessible at future experiments, the viability of the scenario crucially depends on the temperature of asymmetry generation too. This provides a unique way of probing both the amount of asymmetry and the corresponding temperature via future observations of GWs from collapsing DWs. The large asymmetry in the Dirac fermion can also have interesting implications for the observed baryon asymmetry as well as dark matter and large neutrino asymmetry.

    hep-phastro-ph.CO3 citations
26. 26*

    Nonperturbative suppression of beyond-General-Relativity effects in quadratic gravity

    Georgios Antoniou🇵🇹 · Leonardo Gualtieri🇮🇹 · Paolo Pani🇮🇹

    Quadratic gravity is a well-motivated extension of general relativity~(GR) wherein the Einstein-Hilbert action is augmented by quadratic curvature terms. This theory is equivalent to GR in an effective-field-theory framework, while the two theories are different at the non-perturbative level. As we have recently shown, black holes in quadratic gravity have a rich linear response, including extra scalar, vector, and tensor quasinormal modes that can be excited in physical processes, even when the stationary solution is the same as in GR. Here, by studying the gravitational-wave emission from point particles plunging into a Schwarzschild black hole in quadratic gravity, we show that observable deviations from GR are exponentially suppressed in the GR limit. This provides a nonperturbative realization of the equivalence between quadratic gravity and GR predicted in the effective-field-theory framework.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2026)·2 citations
27. 27*

    Smoluchowski Coagulation Equation and the Evolution of Primordial Black Hole Clusters

    Borui Zhang🇨🇳 · Wei-Xiang Feng🇨🇳 · Haipeng An🇨🇳

    In arXiv:2507.07171, we demonstrate that the high-redshift supermassive black holes in the so-called "little red dots" discovered by James Webb Space Telescope (JWST) can be explained by the primordial black hole (PBH) clustering on small scales. In this paper, we present a comprehensive simulation of the successive PBH mergers within a cluster by solving the Smoluchowski coagulation equation. We derive the coagulation kernel considering both cases with and without the effects of mass segregation. Then we employ the Monte Carlo method to solve the equation, implementing the full-conditioning scheme using the discrete inverse transformation method. Our simulations determine the runaway timescales of clusters and the mass population evolution of PBHs across a wide range of cosmic redshifts, depending on the number of PBHs within the cluster and the associated density.

    ↳ astro-ph.COgr-qchep-phphysics.comp-phJCAP(2026)·2 citations
28. 28*

    Interior geometry of black holes as a probe of first-order phase transition

    Zi-Qiang Zhao🇨🇳 · Zhang-Yu Nie🇨🇳 · Shao-Wen Wei🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    Traditional diagnostics of black hole phase transitions rely on thermodynamic quantities defined at the event horizon or asymptotic boundary. Here, we demonstrate that the near-singularity geometry offers a sharp, independent probe of both first-order phase transitions and supercritical crossover. For scalarized AdS black holes exhibiting a first-order phase transition, the Kasner exponent $p_t$, which characterizes the approach to the singularity, undergoes a dramatic transformation. On one side of the transition, $p_t$ oscillates strongly with temperature, reflecting violent interior dynamics. On the other side, it becomes a smooth, monotonically varying function. These two distinct behaviors converge as the critical point is approached. Beyond the critical point, in the supercritical region, $p_t(T)$ develops a distinct extremum, defining a Kasner crossover line that is entirely independent of traditional thermodynamic (Widom line) or dynamic (Frenkel line) criteria. Our work establishes the near geometry of singularity of scalarized black hole as a novel class of diagnostics for phase transitions, revealing that a change in the macroscopic thermodynamic state fundamentally reshapes the deepest interior structure of spacetime.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2026)·3 citations
29. 29*

    Tackling inverse problems for PDFs from lattice QCD

    Alexander Rothkopf🇰🇷

    In this kick-off presentation for the "Recent developments in QCD" session at Baryons 2025 I will tie together the recent progress made on the extraction of parton distribution functions (PDFs) in lattice QCD and the long standing efforts in solving the inverse problem in the form of spectral function reconstruction.

    ↳ hep-lathep-phnucl-thJ.Subatomic Part.Cosmol.(2026)·1 citation
30. 30*

    Gauge invariant momentum broadening of hard probes in glasma

    Margaret E. Carrington🇨🇦 · Bryce T. Friesen🇨🇦 · Stanislaw Mrowczynski🇵🇱

    We compute the transport coefficient $\hat{q}$ which quantifies the transverse momentum broadening of hard probes passing through the evolving glasma from the earliest stage of relativistic heavy-ion collisions. We use a proper-time expansion method which is designed to study the glasma at very early times. In our earlier calculations of $\hat{q}$ we used an approximation that greatly simplifies the complexity of the calculation but introduces a violation of gauge invariance. Based on these results we argued that the glasma plays an important role in jet quenching. In this paper we have used a gauge invariant formulation to calculate $\hat{q}$. The results for the momentum broadening coefficient are quantitatively very close to those of our previous simplified version of the calculation and confirm our earlier conclusion about the importance of the glasma contribution to jet quenching.

    ↳ nucl-thhep-phPRC(2026)·3 citations
31. 31*

    Fluid perturbations from expanding bubbles in first-order phase transitions

    Chiara Caprini🇨🇭 · Antonino S. Midiri🇨🇭 · Simona Procacci🇨🇭 · Alberto Roper Pol🇨🇭

    We study the power spectrum of the velocity field induced during a first-order phase transition occurring in the radiation-dominated era. We focus on the phase of bubble expansion, assuming that it ends with the onset of the sound-wave regime. The main result we present is a refined template for the velocity spectrum at the beginning of the sound-wave phase, which can be used for studying the resulting anisotropic stresses and gravitational wave production. In particular, we find that the breaks in the velocity spectrum are not associated to the bubble size and the sound shell thickness, as previously proposed, but to the position of the discontinuities. This distinction is particularly relevant for supersonic deflagrations, as it implies that the intermediate slope is more pronounced and the two breaks are more separated when the wall velocity approaches the Chapman-Jouget speed, instead of the sound speed. We also show that the asymptotic branches of the velocity power spectrum are determined by the integral over the single-bubble profiles at large scales, and by the discontinuities of the velocity profiles at small scales. Furthermore, we study the dependence of the two breaks and the intermediate slope on the distribution function of the times of bubble nucleation (exponential and simultaneous). All the results presented in this work have been included in the public Python package CosmoGW.

    ↳ gr-qchep-ph4 citations
32. 32*

    Recursive relations from diffeomorphism in the Randall-Sundrum model

    Haiying Cai🇨🇳 · Giacomo Cacciapaglia🇫🇷

    Models of gravity in warped extra dimensions enjoy invariance under diffeomorphism. We derive the nonlinear transformation rules for the metric perturbations in the unitary gauge. As an off-shell symmetry, the main consequence of diffeomorphism is a set of recursive relations linking consecutive orders in the field expansion of the effective Lagrangian. The physical consequences are briefly explored for the Randall-Sundrum model with hard branes.

    ↳ hep-thhep-ph0 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.