Fri·Dec 19, 2025Friday·December 19, 2025

1. 01*

   Fifty shades of grayness: parametrizations of spectral distortions and applications in cosmology

   Gabriela Barenboim🇪🇸 · Julien Froustey🇪🇸 · Cyril Pitrou🇫🇷 · Héctor Sanchis🇪🇸

   Thermal distribution functions can only be of the Fermi-Dirac or Bose-Einstein types, whereas distorted spectra encompass any possible deviations from these shapes. It is fruitful to devise parametrizations of these distortions with only a few parameters which depend on the physical system considered. A method proposed by Stebbins consists in describing a distorted spectrum as a sum of thermalized spectra with a distribution of temperatures, the moments of which are the parameters of interest. After revisiting and extending this approach by working at the level of the number density distribution instead of the standard spectrum, we build another method which consists in describing the distorted spectrum by a polynomial modulating a reference thermalized spectrum. The distortion parameters are then the coefficients of a decomposition on a suitable orthonormal polynomial basis. We advocate that the latter is computationally easier and allows to describe a wide range of distortions. With this formalism, we efficiently describe the standard distortions of the cosmological backgrounds of neutrinos and photons, and we obtain model-independent constraints on nonstandard distortions of these cosmological relics.

   hep-phastro-ph.COPRD(2026)·2 citations
2. 02*

   Energy-Energy Correlators in $e^{+}{e}^{-}$ and Deep Inelastic Scattering

   Yuxun Guo🇺🇸 · Werner Vogelsang🇩🇪 · Feng Yuan🇺🇸 · Wenbin Zhao🇺🇸

   We study energy-energy correlators (EECs) in $e^{+}{e}^{-}$ annihilation and deep inelastic lepton-hadron scattering (DIS), focusing on aspects of nonperturbative physics in these observables. We introduce the EEC jet functions and investigate the infrared (IR) behavior of both small-angle EECs and angle-integrated EECs by performing explicit one-loop calculations. The factorization and universality of the EECs in these processes are demonstrated. A matching scheme is proposed to smoothly connect kinematic regions where different scaling behaviors with jet energy are observed. In combination with the next-to-leading order correction, this matching provides a good description of the EEC data and PYTHIA simulations in high-energy $e^{+}{e}^{-}$ annihilation. Predictions for DIS processes for future electron-ion collider kinematics are also presented.

   hep-phhep-exnucl-thPRD(2026)·8 citations
3. 03*

   Deconstructive Composite Dark Matter Detection

   Yilda Boukhtouchen🇨🇦 · Joseph Bramante🇨🇦 · Christopher Cappiello🇺🇸 · Melissa Diamond🇨🇦

   We investigate the detection of composite dark matter that disassembles into a cascade while crossing the Earth. This occurs for loosely bound composite dark matter, where the binding energy per constituent is small, such that scattering with Standard Model nuclei typically imparts enough energy to dissociate a constituent from its composite. Trajectories and cascade profiles are found for dissociated constituents that are further diverted by scattering through the Earth. Such scattering cascades are a common feature of TeV-scale weakly-interacting dark matter loosely bound in composites. We identify underground detector signatures of constituent cascades that depend on composite characteristics; these signatures include non-collinear multiple scatters in detectors, parameter-dependent timing separation of multiscatter events, and regions of parameter space where a dark matter cascade would leave a coincident signature in different underground laboratories.

   hep-phhep-ex4 citations
4. 04*

   Investigation of Nuclear Modification Factor from RHIC to LHC energies using Boltzmann Transport equation in conjunction with q-Weibull distribution

   Rohit Gupta🇮🇳

   The study of nuclear modification factor is crucial in advancing our knowledge of the hot and dense nuclear matter created during high energy heavy-ion collision. In this direction, we have developed a theoretical model for the nuclear modification factor using the Boltzmann Transport equation in relaxation time approximation with the q-Weibull distribution as the final state distribution and studied the experimental data of nuclear modification factor of charged hadrons as well as identified particles at various energies ranging from 7.7 GeV measured at RHIC upto the maximum value of 5.44 TeV studied in LHC. We observed a good agreement between the model and the experimental data as can be quantified using the ${\chi }^2$/NDF values. We have also studied the mass dependence of different fit parameters that appears in the theoretical model and observe a linear mass dependence of some parameters.

   hep-phnucl-thPRD(2026)·0 citations
5. 05*

   Visible and Invisible Pseudoscalar Meson Decays from Anomaly Sum Rules

   Xurong Chen🇨🇳 · Sergey Khlebtsov🇷🇺 · Armen Oganesian🇷🇺 · Oleg Teryaev🇷🇺

   The decays of pseudoscalar mesons to real and virtual photons as well as neutrino-antineutrino pairs are considered in the framework of the dispersive method based on Anomaly Sum Rules. The contribution of singlet channel involving the new non-perturbative gluon form factor of virtual photon $B(q^2)$ is systematically taken into account. The detailed analysis of its dependence on photon virtuality $q^2$ relying on the available data for meson transition fomfactors is performed. It is shown that B has quite a nontrivial structure at $q^2\sim 1Ge{V}^2$ which may be a signal of the existence of pseudoscalar glueball with a mass about 1.5-2 GeV. The calculation of the decay to $\nu \bar{\nu }$ pairs leads to the compatibility with the result of Arnellos, Marciano and Parsa of 1982, when pion decay is considered neglecting the mixing effects. The account for these effects results, however, in the enhancement of pion branching ratio by a factor of 3, while that for eta decay is larger by several orders of magnitude. It is stressed, that dependence on the pair invariant mass is entirely defined by QCD and coincides with that of the meson transition form factor. The role of obtained results for the physics at HHaS detector at HIAF is discussed.

   hep-ph0 citations
6. 06*

   Fatjet Signatures of Quintuplet Fermions at the LHC

   Sourabh Dube🇮🇳 · Nilanjana Kumar🇮🇳 · Shriyansh Ranjan

   This paper explores a simplified extension of the standard model featuring a neutral fermion quintuplet and a scalar quadruplet, which together generate neutrino masses through tree and loop level mechanisms. The quintuplet fermions decay into standard model gauge bosons via the scalars, producing unique collider signatures at the LHC characterized by multilepton and multijet final states. The study focuses on the pair production of quintuplet fermions in the 700-1200 GeV mass range, where their decays produce highly boosted W and Z bosons identifiable as fatjets. Emphasis is placed on the production and decay of doubly charged fermions due to their higher cross section. Advanced jet substructure and kinematic techniques are applied to enhance sensitivity by reducing standard model backgrounds. A detailed analysis of signal significance is performed in the two lepton, two fatjet and three lepton, one fatjet channels for different masses of the fermion and the scalars, optimizing selection cuts to maximize signal efficiency over standard model backgrounds. The study found that both channels exhibit excellent performance, with significance exceeding $5\sigma$ under realistic conditions including a 50\% background uncertainty at integrated luminosity up to 3000 fb${}^{-1}$.

   hep-ph0 citations
7. 07*

   Fermion (non)reheating with a quartic inflaton potential

   Nabeen Bhusal🇩🇪 · Ernesto Chávez M.🇲🇽 · Marcos A. G. Garcia🇲🇽 · Adriana G. Menkara🇩🇪 · Mathias Pierre🇩🇪

   Any viable inflationary model must account for reheating of the universe prior to the onset of primordial nucleosynthesis. In this work, we study the (p)reheating mechanism for an inflaton field with a quartic minimum of the T-model kind with coupling $\lambda$, prior to and post fragmentation, making a clear distinction between the two regimes. We assume that the main particle production channel corresponds to the decay into a pair of spin 1/2 fermions via Yukawa-like interactions. On top of its decays, we also consider the self-interaction of the inflaton, which sources the resonant growth of inflaton inhomogeneities, possibly leading to its eventual fragmentation. By means of a combination of non-perturbative (Heisenberg/Bogoliubov) and perturbative (Boltzmann) methods, we find that for Yukawa couplings that seemed to be intuitively perturbative, such as $y\gtrsim 10^{-8}$ ($y^2/\lambda \gtrsim 3\times 10^{-5}$), parametric resonance, kinematic blocking, and Pauli suppression effects cannot be ignored. Additionally, we show that achieving ${\rho }_{\varphi }\sim {\rho }_{\psi }$ prior to fragmentation requires large couplings, $y\gtrsim 0.2$ ($y^2/\lambda \gtrsim 10^{10}$), which needs a detailed study of backreaction and radiative corrections. Thus the rest of our work constitutes studying post-fragmentation fermion production where we conclude that, in general, reheating in this setup is not possible and thus we conclude that in order to successfully reheat, one must invoke a coupling to a integer- and/or 0-spin particle like a scalar boson.

   hep-phJCAP(2026)·6 citations
8. 08*

   Long-lived particle production through the PRISM

   Kevin J. Kelly🇺🇸 · Mudit Rai🇺🇸

   Accelerator-based neutrino experiments offer a competitive environment to search for long-lived particles with sub-GeV masses. Yet, many theoretical models involving such particles predict very similar phenomenology and nearly identical final-state signatures. In view of this, we study the capabilities of upcoming experiments -- specifically the DUNE near detectors -- to distinguish between different classes of long-lived particles and the mechanisms by which they are produces. We expound how the experiment's excellent energy resolution, combined with the possibility to move the detector off-axis (the DUNE-PRISM concept), work in tandem to improve the discrimination power.

   hep-phPRD(2026)·0 citations
9. 09*

   Neutrino Propagation in Quantum Field Theory at Short and Long Baselines

   Vadim A. Naumov🇷🇺 · Dmitry S. Shkirmanov🇷🇺

   In a quantum field approach to neutrino oscillations, the neutrino is treated as a propagator, while the external initial and final particle states are described by covariant wave packets. For the asymptotic behavior on short and long macroscopic baselines, the wave packet modified neutrino propagator is expressed through asymptotic series in powers of dimensionless Lorentz and rotation invariant variables. In both regimes, leading-order corrections violate the classical inverse-square law and lead to a decrease in the neutrino-induced event rate. The possibility that the so-called reactor antineutrino anomaly can, at least partially, be explained within this approach is discussed.

   hep-phhep-thquant-ph0 citations
10. 10*

    Entropy of Schwinger pair production in time-dependent Sauter pulse electric field

    Zhi-Hang Yao🇨🇳 · Hong-Hao Fan🇨🇳 · Lie-Juan Li🇨🇳 · Hai-Bo Sang🇨🇳 · Bai-Song Xie🇨🇳

    We investigate entropy of electron-positron pair production in time-dependent Sauter pulse electric field. Both cases of pair longitudinal momentum only and full momentum consideration are examined. We further examine three types of entropy, one is the usual entanglement entropy $S_{\text{E}}$, the other two extensions are thermal distribution entropy $S_{\text{Th}}$, and that with the chemical potential correction, $S_{\text{Th,CP}}$. For short pulse, $S_{\text{E}}$ is higher than $S_{\text{Th}}$ and vice versa for long pulse. The chemical potential causes the single-particle average thermal distribution entropy $\frac{S_{\text{Th,CP}}}{N}$ to exhibit non-monotonic behavior, similar to the single-particle average entanglement entropy $\frac{S_{\text{E}}}{N}$ in the short-pulse range. In the full momentum case, we calculate the thermal distribution entropy $S_{\text{Th, U}}$ via introducing the Unruh temperature as the local effective temperature. We find that both $S_{\text{Th, U}}$ and $S_{\text{E}}$ saturate asymptotically to the constant while the former has a larger asymptotic value. The results presented in this study reveals that the different entropies have some delicate relationships among them.

    hep-phquant-ph0 citations
11. 11*

    Generalized CP from non-invertible selection rules

    Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵

    We study a framework in which fields are labeled by basis elements of a fusion algebra with non-invertible fusion rules. In particular, we consider the case where fields are labeled by conjugacy classes of a finite group rather than its irreducible representations. When the fusion rules possess a ${\mathbb{Z}}_2$ symmetry identified with charge conjugation, a CP-invariant system can be consistently defined together with parity transformation. Furthermore, it is found that combining group-based flavor symmetries underlying non-invertible selection rules with CP symmetry naturally leads to a generalized CP transformation. We also demonstrate the possibility of spontaneous CP violation in this framework and discuss its implications for Yukawa textures.

    hep-phhep-th11 citations
12. 12*

    Compactified 2HDM under the Non-SUSY AdS instability conjecture

    M. A. Rbah🇲🇦 · S. Saoud🇲🇦 · R. Sammani🇲🇦 · E. H. Saidi🇲🇦 · R. Ahl Laamara🇲🇦

    We investigate how extra-dimensional dynamics influence Higgs-sector phenomenology by compactifying a Two-Higgs-Doublet Model (2HDM) coupled to 4D gravity on a circle \(S^1\). The resulting effective potential includes tree-level 2HDM interactions, one-loop Coleman--Weinberg corrections from the Kaluza--Klein towers, and an effective radion stabilization contribution inspired by the broader modulus-stabilization literature. We derive the corresponding 3D effective action and show that, for the observed Higgs mass \(m_h=125\,\mathrm{GeV}\), the compactified potential admits a stabilized configuration with near-zero vacuum energy. By imposing the non-supersymmetric AdS instability conjecture as a quantum-gravity consistency requirement, we obtain a constraint within our numerical setup on the heavy Higgs sector, finding that the additional scalar states must satisfy approximately \(M_H \gtrsim 680\,\mathrm{GeV}\) in order to avoid perturbatively stable non-supersymmetric AdS\(_3\) minima. Our results demonstrate how Swampland-inspired constraints can yield phenomenologically relevant predictions for extended Higgs sectors.

    hep-ph0 citations
13. 13*

    CHIC: Caley-Hamilton, Invariants and Constants for Neutrino Oscillation Probabilities and Gradients

    Pablo Fernández-Menéndez🇪🇸

    We use the Caley-Hamilton theorem to derive analytical solutions for the three-flavor neutrino propagation amplitude in a constant-density medium and their derivatives with respect to the mixing parameters. This approach avoids the diagonalization of the Hamiltonian and exploits precomputed matrix invariants to separate the dependence of oscillation probabilities on neutrino energy and propagation baseline. The results are implemented in the CHIC software, which provides simple, fast and efficient computation of oscillation probabilities and their derivatives. Finally, we demonstrate the value of probability gradients for neutrino data analyses and introduce a complementary visualization, the oscillograds, to probe underlying features of neutrino mixing.

    hep-phhep-exJ.Phys.G(2026)·2 citations
14. 14*

    Learning holographic QCD with unflavored meson spectra

    Mathew Thomas Arun🇮🇳 · Ritik Pal🇮🇳

    We develop a data-driven neural network framework to reconstruct the five-dimensional background geometry, the dilaton potential, and the chiral-symmetry-breaking scalar potential of holographic QCD from hadron mass spectra. Framed as an inverse problem, the model is trained using a discretized form of the Schrödinger-like equation, which resembles a linear moose in ``deconstructed" 5 dimensions with Dirichlet boundary conditions, in contrast to the AdS/DL with ``emergent" space-time. Using the masses of the unflavored mesons $\rho$, $a_1$, $a_2$, and $f_0$ and their excitations as training data, the model learns confining effective potentials and computes a dilaton profile that satisfies the null energy condition. The network predicts that the dilaton's IR behavior will be much steeper than its quadratic form. Moreover, the symmetry-breaking bulk potential of the scalar field, $V(X)\sim k_1{X}^3+k_2{X}^4$, was computed, and the parameters $k_1$ and $k_2$ predicted to be $\sim -4$ and $\sim 9$ respectively. The deep-learned parameters, metric, and the dilaton profile were then used to predict the pion mass and its spectrum with good accuracy. A Python code, along with the trained models, is provided to facilitate further studies\footnote{Available at Github, https://github.com/rp-winter/NN-AdS-QCD

    hep-phcond-mat.dis-nnhep-thJHEP(2026)·3 citations
15. 15*

    Coherence from Randomness: Sub-keV Dark Matter Scattering off Random, Heterogeneous Materials

    Zhi-Han Liu🇨🇳 · Shigeki Matsumoto🇯🇵 · Jie Sheng🇯🇵 · Chuan-Yang Xing🇨🇳

    The sub-keV mass range has long posed a challenge for the direct detection of dark matter via elastic scattering. In this Letter, we propose a new mechanism in which dark matter, assumed to be quadratically coupled to SM particles, scatters from random heterogeneous materials with intrinsic density fluctuations, yielding an enhanced coherent response. This effect can substantially increase the total scattering rate and induce measurable accelerations of the target. Using this idea, we derive new constraints from the MICROSCOPE mission that extend into previously unexplored parameter space for sub-keV dark matter, probing cross sections down to $\sim 4\times 10^{-38}\mathrm{c}{\mathrm{m}}^2$.

    hep-ph3 citations
16. 16*

    Unveiling Light-Quark Yukawa Flavor Structure via Dihadron Fragmentation at Lepton Colliders

    Qing-Hong Cao🇨🇳 · Xin-Kai Wen🇨🇳 · Bin Yan🇨🇳 · Shu-Tao Zhang🇨🇳

    Directly probing light-quark Yukawa couplings and their flavor structure remains a major challenge due to their smallness and overwhelming QCD backgrounds. In this Letter, we propose a theoretical framework to access these couplings at lepton colliders through transverse spin dependent azimuthal modulations in dihadron fragmentation. These modulations arise from the interference between Higgs mediated and standard model amplitudes in $e^{-}{e}^{+}\to q\bar{q}Z$, producing angular structures that are linearly sensitive to the Yukawa couplings $y_q$, in contrast to conventional observables that scale as $y_q^2$. By combining channels with an identified accompanying single hadron, $h^{\prime }={\pi }^{\pm },K^{\pm }$, and $p/\bar{p}$, this approach cleanly disentangles the up- and down-quark Yukawa contributions, yielding typical limits at the $\mathcal{O}(10^{-4}\sim 10^{-3})$ level and establishing fragmentation dynamics as a novel and complementary probe of the Higgs flavor structure.

    hep-phhep-exnucl-exnucl-thPRL(2026)·6 citations
17. 17*

    The Nontrivial Vacuum Structure of an Extended $t\bar{t}$ BEH (Higgs) Bound State

    Christopher T. Hill🇺🇸

    In a recent reformulation of top-quark condensation for the Brout-Englert-Higgs boson we introduced an extended internal wave-function, $\varphi (r)$. We show how this leads to a manifestly Lorentz invariant formalism, where the absence of ``relative time'' is a gauge invariance of the bilocal field theory. This dictates a novel and nontrivial Lorentz invariant vacuum structure for the BEH boson, the relativistic generalization of a condensed matter state analogous to a BCS condensate.

    hep-phhep-th1 citation
18. 18*

    Chiral magnetic effect amplified baryogenesis at first-order phase transitions

    Hui Liu🇨🇳 · Ligong Bian🇨🇳

    In this study, we show that, in the background of the primordial magnetic field, the chiral magnetic effect effect can significantly amplify the chiral chemical potential sourced by the CP violation near the bubble walls during the first-order electroweak phase transition. This effect can lift the generated baryon asymmetry by several orders, and make it possible to explain the baryon asymmetry of the Universe with a CPV in the fermion sector far beyond the limitation of the electron dipole moment.

    hep-phastro-ph.COhep-th3 citations
19. 19*

    Supercooling exit from charge supersaturation

    Pietro Baratella🇸🇮

    Systems that feature a scalar field $\varphi$ with a quasi scale invariant potential, metastable at $\varphi =0$, can remain trapped, during cosmic evolution, in the `wrong' vacuum because the process of bubble nucleation to the true vacuum is inefficient. If $\varphi$ carries a conserved charge $Q$, the presence in the system of a non-zero chemical potential for $Q$ offers the possibility of escaping eternal supercooling: when a species decouples from the plasma the balance among the stabilising effect of temperature and the destabilising effect of chemical potential can change in favour of the latter, so that $\varphi$ condenses and triggers the transition to the stable phase.

    hep-phPRD(2026)·1 citation
20. 20*

    Condensation of slow $\gamma$-quanta in strong magnetic fields

    Leah Folkerts🇩🇪 · Reinhold Egger🇩🇪 · Carsten Müller🇩🇪 · Selym Villalba-Chávez🇩🇪

    The implications of the root singularity of the vacuum polarization tensor near the first pair creation threshold on blackbody radiation are investigated for magnetic fields above the characteristic scale of quantum electrodynamics. We show that the vacuum birefringence in such a strong background leads to an anisotropic behavior of the Planck radiation law. The thermal spectrum is characterized by a resonance that competes with the Wien maximum, causing a crossover in the low $\gamma$-spectrum of the heat radiation. A light state resembling a many-body condensate with slow motion is linked to the high-temperature phase. This novel state of radiation may coexist with nuclear or quark matter in a neutron star's core, increasing its compactness and influencing its stability.

    hep-phcond-mat.otherquant-ph0 citations
21. 21*

    Probing Excited $q\bar{q}$ Mesons via QCD Sum Rules

    Shuang-Hong Li🇨🇳 · Wei-Yang Lai🇨🇳 · Hong-Ying Jin🇨🇳

    We present a systematic study of the masses of light excited $q\bar{q}$ mesons using QCD sum rules at next-to-leading order (NLO). To probe excited states, we construct several interpolating currents with covariant derivatives inserted. The calculation is carried out up to dimension-8 condensates, including NLO perturbative and $m⟨\bar{q}q⟩$ corrections. Employing Gaussian sum rules, we obtain several $J^P=2^{\pm }$ nonets with masses that agree well with experiments. Several $J=0,1$ states compatible with experiments are also obtained using both Gaussian and Laplace sum rules. In particular, the $J^{PC}=2^{++}$ current couples to two distinct $2^{++}$ resonances. This work demonstrates the efficacy of operators with covariant derivatives for studying excited hadrons.

    hep-phPRD(2026)·4 citations
22. 22*

    The Physics of Herwig 7

    J. Bellm🇸🇪 · G. Bewick🇬🇧 · S. Ferrario Ravasio🇮🇹 · S. Gieseke🇩🇪 · D. Grellscheid🇳🇴 · S. Kiebacher🇩🇪 · P. Kirchgaeßer🇩🇪 · F. Loshaj🇩🇪 · M.R. Masouminia🇬🇧 · G. Nail🇬🇧 · A. Papaefstathiou🇺🇸 · S. Plätzer🇦🇹 and 14 other authors

    We present the physics foundations and recent developments of Herwig 7, the modern successor of the original HERWIG and Herwig++ series. Herwig 7 provides a flexible and systematically improvable framework for the simulation of high-energy lepton and hadron collisions, with particular emphasis on QCD and EW effects. Hard scattering processes are generated within the automated Matchbox framework, which integrates external amplitude providers, supports tree-level, next-to-leading-order (NLO) and loop-induced matrix elements, and implements subtraction schemes, multi-channel phase-space sampling, dynamic scale choices and both POWHEG- and MC@NLO-type matching algorithms. Consistent multijet merging at LO and NLO is provided, enabling precise predictions across a wide range of SM processes. Parton radiation is simulated using two complementary showers: an angular-ordered shower incorporating QCD coherence and the heavy-quark dead-cone effect, and a dipole shower optimised for NLO matching and multijet merging. Higher-order corrections are included through matrix-element corrections and dedicated reweighting techniques, while QED and EW radiation are treated using a YFS formalism and EW showering algorithms. The modelling of non-perturbative physics employs an advanced cluster hadronization framework with improved cluster formation, fission and decay, as well as colour reconnection models, heavy-quark effects and interfaces to alternative hadronization schemes. An extended eikonal multiple-partonic-scattering model, incorporating semi-hard and soft components together with diffractive interactions, enables realistic descriptions of minimum-bias and underlying-event data. Herwig 7 thus represents a versatile event generator, providing a coherent, modular and extensible platform for Standard Model and beyond-the-Standard-Model collider phenomenology at current and future facilities.

    hep-ph28 citations
23. 23*

    Scalar damping in cosmological phase transitions

    Andreas Ekstedt🇸🇪 · Thomas Konstandin🇩🇪 · Jorinde van de Vis🇨🇭

    We outline how to calculate the scalar damping term during a cosmological phase transition from kinetic theory. We determine the scalar damping rate from top quarks and weak gauge bosons in a Standard Model-like theory. We find that the convergence of the bosonic contributions hinges on how the soft modes are treated. We discuss the validity of the phenomenological friction term employed in hydrodynamical simulations. We find that for a Standard Model particle content, this approximation is (marginally) justified. We also test the hypothesis that the pressure from a runaway wall acts as an upper bound on the pressure from the local friction term. We find that next-to-leading order contributions in terms of velocity and mass are negative and that in the regime of validity, the local damping term indeed cannot surpass the pressure from runaway bubbles.

    hep-phJCAP(2026)·8 citations
24. 24*

    Enhanced di-Higgs production from TeV-scale heavy neutral leptons at future lepton colliders

    Jonathan Kriewald🇸🇮 · Emanuelle Pinsard🇨🇭 · Ana M. Teixeira🇫🇷

    Within the context of heavy neutral lepton extensions of the Standard Model, we consider the rare di-Higgs production mode ${\ell }^{+}{\ell }^{-}\to hh$ at future high-energy lepton colliders. As a concrete example, we study the impact of a low-scale Inverse Seesaw realisation on the prospects for di-Higgs production. Our results show that the presence of TeV-scale heavy neutral leptons can enhance the cross-section by up to factor 60. We further comment on the interplay with electroweak precision observables, showing that bounds on the di-Higgs production cross-section at future high-energy lepton colliders could serve as complementary probes of low-scale seesaw scenarios.

    hep-ph1 citation
25. 25*

    On Non-Minimal Couplings to Gravity and Axion Isocurvature Bounds

    Claire Rigouzzo🇬🇧 · Sebastian Zell🇩🇪

    For axions present during inflation, it has been shown that a non-minimal coupling ${\xi }_{\sigma }$ of the inflaton to gravity worsens isocurvature bounds, while a non-minimal coupling ${\xi }_{\rho }$ of the radial Peccei-Quinn field can alleviate them. We analyze the simultaneous presence of both couplings and determine when one effect dominates the other, in both the metric and Palatini formulations of gravity. The two tendencies interpolate smoothly, but introducing a non-minimal inflaton coupling reduces the viable interval of ${\xi }_{\rho }$ in which isocurvature bounds can be alleviated while avoiding backreaction on the inflationary dynamics. We illustrate our findings in Palatini Higgs inflation and Starobinsky inflation.

    hep-phastro-ph.COgr-qchep-thPRD(2026)·4 citations
26. 26*

    Consistent Excesses in the LHC Electroweak SUSY Searches: GUT-based Singlino/Higgsino Interpretation in the NMSSM

    Emanuele Bagnaschi🇮🇹 · Manimala Chakraborti🇬🇧 · Sven Heinemeyer🇪🇸 · Ipsita Saha🇮🇳

    The search for supersymmetric models remains one of the main items on the BSM search program at the LHC, with EW SUSY partners still allowed with masses as low as a few hundred GeV. Over the last years, searches for the "golden channel", $pp\to {\tilde{\chi }}_2^0{\tilde{\chi }}_1^{\pm }\to {\tilde{\chi }}_1^0{Z}^{(\ast )}{\tilde{\chi }}_1^0{W}^{\pm (\ast )}$ show consistent excesses between ATLAS and CMS in the 2~soft-lepton and 3~soft-lepton plus missing-$E_T$ searches, assuming $m_{{\tilde{\chi }}_2^0}\approx m_{{\tilde{\chi }}_1^{\pm }}\gtrsim 200$ GeV and $\Delta m_{21}:=m_{{\tilde{\chi }}_2^0}-m_{{\tilde{\chi }}_1^0}\approx 20$ GeV. We interpret these excesses in the framework of the Next-to-Minimal Supersymmetric Standard Model. We assume a singlino dominated lightest neutralino as a Dark Matter (DM) candidate. The second and third lightest neutralinos are higgsino like, with the higgsino mixing parameter $\mu$ being smaller than the soft SUSY-breaking bino and wino masses, $M_1$ and $M_2$. We furthermore assume the approximate GUT relations $M_1\sim M_2/2\sim M_3/6$, with the implication for our scenario of a gluino mass $m_{\tilde{g}}\sim M_3\gtrsim 3$ TeV. Scalar masses are assumed to heavy and do not play a role in our analysis. We find that this scenario is in agreement with all relevant experimental constraints, comprising the LHC searches for SUSY particles and additional Higgs bosons, the LHC Higgs-boson rate measurements, the DM direct detection limits and the upper limit on the DM relic density. We demonstrate that this scenario gives an excellent description of the observed excesses in the search for 2~and 3~soft-leptons plus \ETmiss, with $m_{{\tilde{\chi }}_2^0}\sim m_{{\tilde{\chi }}_3^0}\sim m_{{\tilde{\chi }}_1^{\pm }}$ and $\Delta m_{21}\sim 20$ GeV. This constitutes the first explanation of the soft-lepton excesses in a model with GUT relations among the soft SUSY-breaking parameters.

    hep-phEPJC(2026)·2 citations
27. 27*

    Next-to-Leading Order corrections to the Next-to-Eikonal DIS structure functions

    Tolga Altinoluk🇵🇱 · Guillaume Beuf🇵🇱 · Jules Favrel🇵🇱 · Michael Fucilla🇵🇱

    We compute next-to-leading order (NLO) corrections to next-to-eikonal (NEik) quark background contributions to DIS structure functions. Among NEik corrections, $t$-channel quark exchanges provide the lowest order contributions in ${\alpha }_s$, and can be represented as insertions of the quark background field of the target. At NLO, we compute NEik corrections induced by both quark and gluon background fields, and suppressed by an explicit factor of ${\alpha }_s$. We show that the NLO corrections to the NEik longitudinal structure function are finite, while those to the NEik transverse structure function exhibit rapidity and UV divergences. These divergences are analyzed, and the finite contributions are extracted.

    hep-phJHEP(2026)·12 citations
28. 28*

    Impact of Supercooling on Direct Searches for Dark Matter and Gravitational Wave Backgrounds

    Davide Racco🇨🇭 · Alfredo Stanzione🇮🇹

    An interesting feature of a cosmological phase transition can be a stage of exponential expansion (supercooling). The modified expansion history and the entropy injection at reheating, can affect the final energy fraction of dark matter. In this paper, we revisit the calculation of the freeze-out and freeze-in dynamics, showing additional effects on top of the standard dilution factor if the dark matter production is completed during the supercooling stage. We show for the first time how these effects can be particularly interesting for direct detection, as the parameter space for WIMP-like candidates shifts from excluded to allowed regions, and freeze-in candidates get closer to experimental reach. A phenomenological motivation to consider supercooling is the associated gravitational wave background. The implications of a finite-duration reheating stage, when the equation of state is close to matter-domination, are a peculiar low-frequency spectrum, and its shift to lower frequencies. These effects are a complementary test of the dynamics that we study for dark matter production, and remarkably can link direct detection of dark matter and gravitational wave astronomy.

    hep-phastro-ph.COhep-th5 citations
29. 29*

    Delayed Scaling of Multi-Type Cosmic F- and D-strings in VOS Models

    Kazuto Nakamura🇯🇵 · Masaki Yamada🇯🇵

    We investigate the velocity-dependent one-scale (VOS) model to the case of one cosmic F-string and two D-strings as color flux tubes in pure Spin($4N$) gauge theory. We analytically calculate the scaling string density as a function of the reconnection probabilities, and confirm our results with numerical calculations. We also determine the timescale at which the string density reaches the scaling regime, and find that for certain values of the reconnection probability, the scaling time can become extremely large, by many orders of magnitude. This leads to a characteristic suppression signature of the gravitational-wave signal at high frequencies, which may become observable in the frequency range of future interferometric gravitational-wave observations.

    hep-phastro-ph.COgr-qchep-thPRD(2026)·1 citation
30. 30*

    ggxy: NLO QCD corrections to loop induced gg initiated processes

    Daniel Stremmer🇩🇪

    We present the program package ggxy, which in its first version can be used to calculate partonic and hadronic cross sections to Higgs boson pair production at NLO QCD and it offers a direct interface to POWHEG-BOX. The 2-loop virtual amplitudes are implemented using analytical approximations in different kinematic regions, while all other parts of the calculation are exact. This implementation allows to freely modify all input parameter, such as the three Higgs coupling, the masses of the top quark and the Higgs boson, and the top-quark mass renormalization scheme.

    hep-phhep-exPoS(2026)·0 citations
31. 31*

    Multiple Axions in Laboratory Experiments

    Arturo de Giorgi🇬🇧 · Joerg Jaeckel🇩🇪 · Sebastian Monath🇩🇪 · Volodymyr Takhistov🇯🇵

    Axions and axion-like particles generically appear in extensions of the Standard Model. While many searches assume only a single axion species, there may exist a whole spectrum of multiple such fields. We develop general formulas for axion-photon oscillations in the presence of multiple axions and analyze the implications for experimental searches, including light-shining-through-a-wall experiments, helioscopes and haloscopes. We demonstrate that axion multiplicity can qualitatively alter observational signatures, particularly through coherence and interference effects. Multiple axions can not only enhance signals compared to single axion scenarios, but also suppress them. We show that variations of experimental parameters and searches allow identifying contributions of multiple axions and obtaining information about their properties.

    hep-phastro-ph.COhep-ex11 citations
32. 32*

    Exploring nuclear modification using one-point energy correlator at the electron-ion collider

    Yu Fu🇺🇸 · Zhong-Bo Kang🇺🇸 · Jani Penttala🇺🇸 · Yiyu Zhou🇮🇹

    We study the one-point energy correlator (OPEC) at both the back-to-back and collinear limits in electron-proton and electron-nucleus collisions. We provide the factorization formalism for the two types of OPEC and present phenomenological predictions in the kinematic region relevant for the future Electron-Ion Collider. Focusing on cold nuclear matter effects in electron-nucleus scattering, we demonstrate that the OPEC serves as a powerful probe of the transverse momentum dependent (TMD) physics and in characterizing the medium-induced transverse momentum broadening in cold nuclear matter.

    hep-phnucl-thJHEP(2026)·4 citations
33. 33*

    Gravity-assisted neutrino masses

    Stefan Antusch🇨🇭 · Salvador Centelles Chuliá🇪🇸 · Miguel Levy🇨🇭

    Gravity is generally expected to violate global symmetries, including lepton number. However, neutrino masses from the Planck-suppressed Weinberg operator are typically too small to account for oscillation data. We propose a new model-building approach to low-scale neutrino mass generation, in which an intermediate spontaneous symmetry-breaking scale generates masses and mixings in the heavy neutral lepton (HNL) sector, while leaving an unbroken residual symmetry $G_{\mathrm{res}}$ that forbids light-neutrino masses. The observed light-neutrino masses then arise because gravity breaks $G_{\mathrm{res}}$ via Planck-suppressed operators, inducing the small lepton-number violation required in low-scale seesaw constructions. The HNLs form pseudo-Dirac pairs, with masses potentially within reach of future colliders and complementary tests in precision searches such as charged lepton flavour violation (cLFV). As an illustration, we present a representative realisation of this class of models and show that, for $\mathcal{O}(1)$ operator coefficients, it predicts a region in the ($M_R$, ${\Theta }^2$)-plane that can be testable via displaced-vertex searches at the High-Luminosity (HL) LHC and the FCC-ee.

    hep-phPLB(2026)·1 citation
34. 34*

    Solving the Dirac equation on a GPU for strong-field processes in multidimensional background fields

    Greger Torgrimsson🇸🇪

    In this paper, we show how to solve the Dirac equation, $(i{\gamma }^{\mu }[{\partial }_{\mu }+ie{A}_{\mu }(t,\mathbf{x})]-m)\psi =0$, on a GPU. This is orders of magnitude faster than solving it on CPU and allows us to consider background fields, $A_{\mu }(t,\mathbf{x})$, that depend on $2+1$ or even $3+1$ coordinates. Our approach is conveniently implemented using the computational library JAX. We show how to obtain the probabilities of Schwinger and nonlinear Breit-Wheeler pair production from these solutions using a scattered-wave-function approach and compare the results with the worldline-instanton approximations.

    hep-phhep-th2 citations
35. 35*

    Anomalous Dimension of a General Effective Gauge Theory II: Fermionic Sector

    Jason Aebischer🇨🇭 · Luigi C. Bresciani🇮🇹 · Nudzeim Selimovic🇮🇹

    The complete set of one-loop anomalous dimensions for general Effective Field Theories (EFTs) is derived using on-shell methods. Combined with previous findings for the bosonic sector, the obtained results conclude the computation of the complete set of leading order Renormalization Group Equations (RGEs) in arbitrary gauge EFTs containing scalar and fermion fields. Renormalization effects are consistently taken into account at the order $1/{\Lambda }^2$ in the new physics scale $\Lambda$ for all renormalizable and non-renormalizable couplings. The obtained template RGEs include operator mixing across different dimensions and are valid for arbitrary gauge groups.

    hep-phhep-th6 citations
36. 36*

    Probing scalar and pseudoscalar new physics using rare kaon decays

    G. D'Ambrosio🇮🇹 · A.M. Iyer🇮🇳 · F. Mahmoudi🇫🇷 · S. Neshatpour🇫🇷

    Rare kaon decays provide sensitive tests of new physics. In this work, we focus on scalar and pseudoscalar operators, analysing the $K\to \pi {\ell }^{+}{\ell }^{-}$ and $K\to {\ell }^{+}{\ell }^{-}$ decays. We highlight the complementary role of different modes: $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$, in particular the forward-backward asymmetry in the muon channel as a clean probe of scalar effects, the stringent constraints from $K_L\to {\mu }^{+}{\mu }^{-}$, and the discovery potential of future measurements of $K_S\to {\mu }^{+}{\mu }^{-}$ and $K_L\to {\pi }^0{\ell }^{+}{\ell }^{-}$. The interplay between charged and neutral modes underscores the complementarity of NA62, the LHCb upgrade, and KOTO-II.

    hep-phPLB(2026)·3 citations
37. 37*

    Uniqueness of the ${\square }^2$ Higher-Derivative Operator Class for Universal Vacuum-Energy Cancellations and Higgs Naturalness

    Masayuki Note🇯🇵

    Within the framework of local, Lorentz-invariant, and Hermitian field theories, we investigate the classification of dimension-6 operators that facilitate the dynamical cancellation of vacuum-energy divergences. We demonstrate that the operator class based on the ${\square }^2$ d'Alembertian is uniquely singled out by the requirement of universal power-divergence subtraction across all spin sectors. By explicitly evaluating the modified propagators and one-loop vacuum integrals, we show that only this structure consistently removes ${\Lambda }^4$ and $m^2{\Lambda }^2$ terms while preserving gauge covariance. Adopting the Real-Time Negative-Norm Prescription (RTNNP) as a consistent contour selection, we find that the higher-derivative Lee--Wick (HDLW) structure leads to a finite, calculable Higgs mass correction. Our results suggest a phenomenologically preferred scale of $M\approx 11.3$ TeV, offering a predictive and structurally motivated resolution to the hierarchy problem.

    hep-phhep-th0 citations
38. 38*

    Creation of spin-3/2 dark matter via cosmological gravitational particle production

    Edward W. Kolb🇺🇸 · Andrew J. Long🇺🇸 · Evan McDonough🇨🇦 · Jingyuan Wang🇺🇸

    We study the cosmological gravitational particle production (CGPP) of spin-3/2 particles during and after cosmic inflation, and map the parameter space that can realize the observed dark matter density in stable spin-3/2 particles. Originally formulated by Rarita and Schwinger, the relativistic theory of a massive spin-3/2 field later found a home in supergravity as the superpartner of the graviton, and in nuclear physics as baryonic resonances and nuclear isotopes. We study a minimal model realization, namely a free massive spin-3/2 field minimally coupled to gravity, and adopt the name raritron for this field. We demonstrate that CGPP of raritrons crucially depends on the hierarchy between the raritron mass $m_{3/2}$ and the Hubble parameter at the end of inflation $H_e$, with high-mass and low-mass cases distinguished by the evolution of the sound speed $c_s$ of the longitudinal (helicity-1/2) mode, which is approximately unity at all times for heavy (relative to Hubble) raritrons and can become small or vanish for lighter raritrons, leading to a dramatic enhancement of production of high momentum particles in the latter case. Assuming the raritrons are stable, this leads to a wide parameter space to produce the observed dark matter density. Finally, we consider a time-dependent raritron mass, which can be chosen to remove the vanishing sound speed of the longitudinal mode, but which nonetheless enhances the production relative to the constant high-mass case, and in particular does not necessarily tame the high momentum tail of the spectrum. We perform our calculations using the Bogoliubov formalism and compare, when applicable, to the Boltzmann formalism.

    hep-phastro-ph.COgr-qchep-thJHEP(2026)·4 citations
39. 39*

    The anomalous magnetic moment of the muon: status and perspectives

    David W. Hertzog🇺🇸 · Martin Hoferichter🇨🇭

    We review the status of the anomalous magnetic moment of the muon as a precision probe of physics beyond the Standard Model (SM) after the release of the final results from the Fermi National Accelerator Laboratory (FNAL) Muon $g-2$ experiment and the second White Paper of the Muon $g-2$ Theory Initiative. While the SM prediction requires further improvements by a factor of four to fully leverage the sensitivity achieved in experiment, the FNAL measurement will set the standard for many years to come, and we discuss a variety of features of the experimental campaign that made this achievement possible. In going forward, we discuss current efforts to improve the SM prediction, and imagine how an experiment would have to be devised to surpass 124 ppb in precision.

    hep-phhep-exhep-latnucl-ex+114 citations
40. 40*

    Measuring the Shape of Kerr Black Holes at the Photon Orbit

    Kiana Salehi · Avery Broderick🇨🇦

    The bright ring-like structures observed in the images of M87* and SgrA* captured by the Event Horizon Telescope strongly support the validity of general relativity. Lensed images of the emission region, often referred to as photon rings in this context, are a direct consequence of the unstable dynamics of null geodesics near the spherical photon orbit in the Kerr spacetime. The order of the lensed image can be characterized by the number of half-orbits the photons complete before reaching the observer, with higher-order photon rings produced by null geodesics that circle the black hole more times. However, low-order rings are significantly influenced by the astrophysical environment. Measuring the Lyapunov exponent requires probing the exponentially small differences between successive photon rings or between photon rings and the shadow. We investigate potential astrophysical sources of systematic error the estimation of Lyapunov exponent, including the location of the observed emission, and especially at low photon ring order. We show that it is nevertheless possible to measure this purely gravitational quantity to roughly 10% and 1% systematic uncertainty by resolving the n=2 and n=3 photon rings with the shadow size, respectively. Therefore, the forthcoming black hole imaging efforts to capture, even if indirectly, the n=2 photon ring can result in a measurement of the Lyapunov exponent that is not limited by astrophysical uncertainties.

    hep-phgr-qc0 citations
41. 41*

    Energy Correlators of Spinning Sources

    Marc Riembau🇨🇭 · Minho Son🇰🇷

    The $N$-point energy correlator measures the energy flux through $N$ detectors. We present a general framework that characterizes its full angular dependence in a series of \textit{spinning energy correlators}. These spinning correlators resurrect the angular momentum structure of both the source and the detector configuration, lost otherwise in inclusive measurements. We demonstrate that unitarity and energy positivity confine these correlators to a sharply bounded region, with the boundary realized by extremal correlators generated by pure spin states. We present a first calculation of spinning energy correlators in QCD as well as spinning energy-charge correlators. Their enhanced insensitivity to infrared dynamics opens up a new set of observables that directly probe the hard part of the scattering. Finally, we provide generalized sum rules, extended to spinning correlators and to conserved charges beyond energy.

    hep-phJHEP(2026)·5 citations
42. 42*

    Fermion Thermal Field Theory for a Rotating Plasma (with Applications to Neutron Stars)

    Alberto Salvio🇮🇹

    This paper provides a systematic and complete study of thermal field theory with fermion fields of any kind for generic equilibrium density matrices, which feature arbitrary values not only of temperature and chemical potentials, but also average angular momentum. This extends a previous study that focused on scalar fields, to all fermion-scalar theories. Both Dirac and Majorana fermions and both Dirac and Majorana masses are covered. A general technique to compute ensemble averages is provided. Path-integral methods are developed to study thermal Green's functions (with an arbitrary number of points) in generic interacting fermion-scalar theories, which cover both the real-time and imaginary-time formalism. These general results are applied to physical situations typical of neutron stars, which are often quickly rotating: the Fermi surface and Fermi momentum, the average energy, number density and angular momentum for degenerate fermions and particle production (such as neutrino production from rotating neutron stars, e.g. pulsars). In particular, it is shown that the neutrino production rate due to the direct URCA (DU) processes grows indefinitely as the angular velocity approaches the inverse linear size of the plasma and, therefore, rotation can significantly increase this rate.

    hep-phastro-ph.HEhep-thJCAP(2026)·3 citations
43. 43*

    Shockwaves and Time Delays in Einstein-Maxwell Effective Field Theory

    Christophe Grojean🇩🇪 · Minyuan Jiang🇩🇪 · Pham Ngoc Hoa Vuong🇩🇪

    We derive the shockwave metric in four-dimensional Einstein-Maxwell effective field theory (EFT) by performing an ultra-relativistic boost of the charged black hole solution accompanied by a rescaling of its mass and charge, including leading order EFT corrections. In contrast to the neutral (Schwarzschild) case, where higher derivative operators leave the shockwave geometry unchanged, we show that electrically charged shockwaves receive nontrivial EFT corrections. We then compute the time delay experienced by a probe photon traversing the resulting charged shockwave. We find that two EFT contributions, the correction to the shockwave geometry and the backreaction induced by the probe photon, are both essential for obtaining a physical time delay that is invariant under field redefinitions of the metric.

    ↳ hep-thgr-qchep-phJHEP(2026)·1 citation
44. 44*

    Probing neutron star interiors and the properties of cold ultra-dense matter with the SKAO

    Avishek Basu · Vanessa Graber · Marcus E. Lower · Marco Antonelli · Danai Antonopoulou · Manjari Bagchi · Prasanta Char · Paulo C. C. Freire · Brynmor Haskell · Huanchen Hu · David I. Jones · Banibrata Mukhopadhyay and 10 other authors

    Matter inside neutron stars is compressed to densities several times greater than nuclear saturation density, while maintaining low temperatures and large asymmetries between neutrons and protons. Neutron stars, therefore, provide a unique laboratory for testing physics in environments that cannot be recreated on Earth. To uncover the highly uncertain nature of cold, ultra-dense matter, discovering and monitoring pulsars is essential, and the SKA will play a crucial role in this endeavour. In this paper, we will present the current state-of-the-art in dense matter physics and dense matter superfluidity, and discuss recent advances in measuring global neutron star properties (masses, moments of inertia, and maximum rotation frequencies) as well as non-global observables (pulsar glitches and free precession). We will specifically highlight how radio observations of isolated neutron stars and those in binaries -- such as those performed with the SKA in the near future -- inform our understanding of ultra-dense physics and address in detail how SKAO's telescopes unprecedented sensitivity, large-scale survey and sub-arraying capabilities will enable novel dense matter constraints. We will also address the potential impact of dark matter and modified gravity models on these constraints and emphasise the role of synergies between the SKA and other facilities, specifically X-ray telescopes and next-generation gravitational wave observatories.

    ↳ astro-ph.HEastro-ph.IMgr-qchep-ph+12 citations
45. 45*

    Thermodynamics from the S-matrix reloaded: emergent thermal mass

    Pietro Baratella🇸🇮 · Joan Elias Miro🇮🇹

    The formalism of Dashen, Ma and Bernstein (DMB) expresses the thermal partition function of a system in terms of the S-matrix operator, roughly $Z(\beta )\propto \int dE{e}^{-\beta E}\text{Tr}\ln S(E),$ where $S$ denotes the full scattering operator on the asymptotic Fock space -- i.e. including all multi-particle sectors -- defined via the Lippmann-Schwinger equation. Recently we have employed this formalism to compute the free energy of flux tubes (essentially a two-dimensional theory of derivatively coupled scalars) and the two-loop $O({\alpha }_s)$ QCD thermal free energy. Moving to higher orders, it is well known that at $O({\alpha }_s^2)$ in QCD, or e.g. at $O({\lambda }^2)$ in $\lambda {\varphi }^4$ theory, the free energy develops IR divergences. These IR divergences are resolved by the screening Debye mass. However, the DMB formalism expresses the free energy in terms of a trace of the S-matrix operator in the vacuum. How, then, does the Debye mass arise in this framework? In this work we address this question, thereby paving the way for higher-order applications of the DMB formalism in relativistic QFT.

    ↳ hep-thhep-phJHEP(2026)·3 citations
46. 46*

    Cosmology with non-linear barotropic Israel-Stewart fluid with causal relaxation time

    Vishnu A Pai🇮🇳 · Titus K Mathew🇮🇳

    We derive an extended expression for the relaxation time of a barotropic Israel-Stewart (IS) fluid using the non-linear causality constraint, and propose a new formulation for modeling causal viscous dissipation in barotropic fluids. With this generalized relaxation time, the non-linear IS equation simplifies to a first-order non-linear expression connecting bulk viscous pressure and energy density, which remains valid in any homogeneous and isotropic spacetime. In the case of spatially flat Friedmann universe, adopting this extended relation in the generalized non-linear IS theory, provides new class of analytical solutions in both, the linear, and the non-linear regimes. We also find that, the resulting effective equation of state in the linear regime naturally reproduces the generalized polytropic form which is often introduced phenomenologically in literature. Resulting dynamical implications are investigated and the constraints necessary for ensuring an acceptable evolutionary behavior for the fluid are determined. A detailed dynamical system analysis of the coupled Einstein-Israel-Stewart (EIS) system is also performed. Finally, we solve the coupled EIS equations numerically, and show that the model can support a transient Hubble slow-roll expansion phase with a smooth exit to a radiation-dominated universe, which is challenging to obtain in standard inflationary models.

    ↳ gr-qcastro-ph.COhep-phphysics.flu-dynPRD(2026)·0 citations
47. 47*

    Universal geometric framework for black hole phase transitions: from multivaluedness to classification

    Shi-Hao Zhang🇨🇳 · Zi-Yuan Li🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    Recent studies have revealed synchronized multivalued behavior in thermodynamic, dynamical, and geometric quantities during the black hole first-order phase transition, which enables a diagnosis from different perspectives, yet its fundamental origin has remained poorly understood. By constructing a unified geometric framework integrating real analysis and covering space theory, we reveal the universal mathematical mechanism behind this phenomenon. We prove that this multivaluedness originates from two non-degenerate critical points in the temperature function $T(r_{+})$, where $r_{+}$ is the horizon radius, which fold the parameter space into a three-sheeted covering structure. As a direct application, we propose that a black hole undergoes a first-order phase transition if and only if its $T(r_{+})$ curve has two extrema. Accordingly, we establish a classification scheme, denoted $A1$, $A2$, and $B$ for black holes. This scheme offers a complementary perspective to classifications based on global topological invariants. Our work provides a theoretical foundation for diagnosing phase transitions via multivaluedness and establishes a unified geometric perspective on black hole thermodynamics, chaotic dynamics, and spacetime structure during first-order phase transitions.

    ↳ gr-qchep-phhep-thmath-ph+1EPJC(2026)·2 citations
48. 48*

    Explicit finite-time illustration of improper unitary evolution for the Klein--Gordon field in de Sitter space

    William T. Emond🇬🇧 · Christian Käding🇦🇹 · Peter Millington🇬🇧

    It is known that quantum field theories in curved spacetime suffer from a number of pathologies, including the inability to relate states on different spatial slices by proper unitary time-evolution operators. In this article, we illustrate this issue by describing the canonical quantisation of a free scalar field in de Sitter space and explicitly demonstrating that the vacuum at a given time slice is unitarily inequivalent to that at any other time. In particular, we find that, if both background and Hamiltonian dynamics are taken into account, this inequivalence holds even for infinitesimally small time steps and not only in the asymptotic time limits.

    ↳ hep-thgr-qchep-phquant-ph0 citations
49. 49*

    A finite temperature framework for quark matter with color-superconducting phases

    Hosein Gholami🇩🇪 · Marco Hofmann🇩🇪 · Débora Mroczek🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸

    Current observations of neutron stars and measurements of gravitational waves only provide constraints on the zero temperature ($T=0$) equation of state (EoS) of dense matter. The detection of the post-merger gravitational-wave signal from a binary neutron star merger would additionally provide access to finite-temperature properties of the EoS which contain more information about the composition and the interactions of dense matter than the cold EoS alone. In particular deconfined quark matter may be probed by its characteristic finite temperature effects. This is especially the case for color-superconducting phases, in which the quasiparticle contribution to the thermal pressure is exponentially suppressed at low temperatures. Here we develop a new finite $T$ framework to model the thermal EoS for dense quark matter based on the cold quark matter EoS which is useful for numerical relativity simulations. We test the validity of the framework against a three-flavor NJL mean-field calculation, both with and without diquark pairing. We find that even for the complicated phase diagram of the NJL model including multiple different phases the framework is accurate to the few percent level for temperatures up to $T\sim 50$MeV.

    ↳ astro-ph.HEgr-qchep-phnucl-th5 citations
50. 50*

    Dark energy and neutrinos along the cosmic expansion history

    Pietro Ghedini🇪🇸 · Rasmi Hajjar🇺🇸 · Olga Mena🇪🇸

    Recent cosmological measurements are hinting that dark energy may evolve, with its equation of state, $w_{\mathrm{DE}}$, even showing oscillatory patterns. In this work, we employ a model-independent approach to jointly reconstruct $w_{\mathrm{DE}}$ and the sum of neutrino masses, $\sum m_{\nu }$, adopting the PCHIP method with seven fixed nodes in which we allow the two parameters to vary. We employ CMB, Baryon Acoustic Oscillations and Supernovae Ia data to constrain the values of $w_{\mathrm{DE}}$ and $\sum m_{\nu }$ at each node. We conduct three different analyses in which we reconstruct $w_{\mathrm{DE}}$: one with fixed $\sum m_{\nu }=0.06\mathrm{eV}$; one in which we allow $\sum m_{\nu }$ to vary, and one in which we also reconstruct $\sum m_{\nu }$ using the PCHIP method. We find the dark energy equation of state to be consistent with the cosmological constant scenario, except when including DESI data and allowing for phantom crossing, where we find a $95\%$ CL deviation from $w_{\mathrm{DE}}=-1$ around $z\sim 1.2$. For neutrino masses, we obtain looser constraints when focusing on phantom dark energy, that show further early and late relaxation when reconstructing the mass via the PCHIP method.

    ↳ astro-ph.COhep-phPhys.Dark Univ.(2026)·7 citations
51. 51*

    Quasi-pole inflation in metric-affine gravity

    Antonio Racioppi🇪🇪

    We propose a new mechanism for inflationary model building in the framework of metric-affine gravity. Such a mechanism involves an inflaton non-minimally coupled with the Holst invariant. If the non-minimal coupling function has a zero point and it is very steep at that same point, the corresponding inflaton kinetic function will feature a quasi-pole behaviour, implying a canonically normalized potential featuring an exponential plateau, regardless of the shape of the original inflaton potential. The inflationary predictions in such a region are equivalent to the ones of Starobinsky inflation.

    ↳ gr-qcastro-ph.COhep-phGen.Rel.Grav.(2026)·7 citations
52. 52*

    Dilaton Effective Field Theory across the Conformal Edge

    Thomas Appelquist🇺🇸 · James Ingoldby🇬🇧 · Maurizio Piai🇬🇧

    Dilaton effective field theory (dEFT) can be employed to analyze lattice data in gauge theories that lie in close proximity of the lower edge of the conformal window. Under special conditions, we show that it can be used as a diagnostic tool to distinguish near-conformal, yet confining, theories from infrared conformal ones. We demonstrate this efficacy by analyzing two sets of lattice measurements taken from the literature. For the $SU(3)$ theory coupled to $N_f=8$ Dirac fermions transforming in the fundamental representation, our analysis favors confinement. For the $SU(2)$ theory with $N_f=1$ adjoint fermion, our fits favor infrared conformal behavior. We discuss future lattice measurements, and analysis refinements, that can further test this framework.

    ↳ hep-lathep-phPRD(2026)·3 citations
53. 53*

    Discovering gravitational waveform distortions from lensing: A deep dive into GW231123

    Juno C. L. Chan🇩🇰 · Jose María Ezquiaga🇩🇰 · Rico K. L. Lo🇩🇰 · Joey Bowman🇩🇰 · Lorena Magaña Zertuche🇩🇰 · Luka Vujeva🇩🇰

    Gravitational waves (GWs) are unique messengers as they travel through the Universe without alteration except for gravitational lensing. Their long wavelengths make them susceptible to diffraction by cosmic structures, providing an unprecedented opportunity to map dark matter substructures. Identifying lensed events requires the analysis of thousands to millions of simulated events to reach high statistical significances. This is computationally prohibitive with standard GW parameter estimation methods. We exploit DINGO-lensing, a deep-learning algorithm that accelerates the inference from CPU days to minutes to thoroughly reanalyze GW231123, the most promising lensing candidate to date. By performing more than 200,000 simulations with 3 different waveform models, we find that its statistical significance is below 4$\sigma$ and the event cannot be claimed as lensed. We observe that 8% of GW231123-like nonlensed simulations favor lensing, which could be explained by the self-similarity of short-duration signals. Still, 58% of GW231123-like lensed simulations have larger support for lensing, showing that higher detection statistics are possible. We show that analyzing simulations with different waveform models only lowers the significance, highlighting the relevance of waveform systematics. Although GW231123 exposes the challenges of claiming the first GW lensing detection, our deep-learning methods have demonstrated to be powerful enough to enable the upcoming discovery of lensed GWs.

    ↳ gr-qcastro-ph.COhep-phPRD(2026)·29 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.