Wed·Apr 8, 2026Wednesday·April 8, 2026

1. 01*

   Gravitational Waves from Matter Perturbations of Spectator Scalar Fields

   Marcos A. G. Garcia🇲🇽 · Angel Garcia-Vega🇲🇽 · Sarunas Verner🇺🇸

   We compute the stochastic gravitational wave background sourced at second order by a spectator scalar field $\chi$ coupled to the inflaton $\varphi$ through a portal interaction $\sigma {\varphi }^2{\chi }^2$ and with quartic self-interaction ${\lambda }_{\chi }{\chi }^4/4!$. In the large portal coupling regime ($\sigma /\lambda \gg 1$, with $\lambda$ the inflaton normalization), parametric resonance during reheating amplifies the spectator power spectrum by many orders of magnitude near the resonance band until Hartree backreaction from the quartic coupling detunes the instability, while the large inflationary effective mass suppresses superhorizon power and ensures compatibility with CMB isocurvature bounds. We focus on the direct field-gradient source ${\partial }_a\chi {\partial }_b\chi$ in the second-order Einstein equations and derive a master formula that factorizes into a spectral integral over the frozen, vacuum-subtracted spectator spectrum and a time integral encoding the post-inflationary expansion history. For our benchmark reheating history we obtain analytic scaling relations, including a peak amplitude ${\Omega }_{\mathrm{GW}}\propto T_{\mathrm{reh}}^{8/3}$, strong dependence on the portal strength, and weak sensitivity to $m_{\chi }$. We validate the framework against nonlinear lattice simulations, demonstrating complementarity: the Hartree treatment captures superhorizon evolution inaccessible to the lattice, while the lattice resolves rescattering and fragmentation near the spectral peak. For $\sigma /\lambda \simeq 10^4$ and $T_{\mathrm{reh}}=2\times 10^{14}\mathrm{GeV}$, the signal reaches ${\Omega }_{\mathrm{GW}}{h}^2\sim 10^{-11}$ at $f\sim 10^7$-$10^8\mathrm{Hz}$. Increasing ${\lambda }_{\chi }$ at fixed $\sigma$ has a non-monotonic effect: small values enhance the signal via rescattering, whereas larger values suppress it by detuning the resonance.

   hep-phastro-ph.COgr-qc1 citation
2. 02*

   Probing Gluon TMD Models with Drell--Yan Structure Functions

   Jan Ferdyan🇵🇱

   We compute structure functions for the Drell--Yan process in proton-proton collisions at the center of mass energy $\sqrt{S}=8\mathrm{TeV}$ both parity conserving and parity breaking. For this calculation, we use the high-energy factorization formalism. The hard scattering matrix elements used in our derivation consist of two channels -- $q_{\mathrm{val}}{g}^{\ast }\to q{V}^{\ast }$ and $g^{\ast }{g}^{\ast }\to q\overline{q}{V}^{\ast }$, both at the tree level. We consider four types of gluon TMD models: Gaussian, Weizsäcker--Williams (WW), Kimber--Martin--Ryskin (KMR), and Jung--Hautmann (JH). We also consider the models with phenomenological adjustments to improve the data description. We derive and compare the structure functions calculated for different gluon TMD models with the ATLAS 2016 data. Based on this comparison, we calculate ${\chi }^2$ per number of degrees of freedom for each of the predictions. This assessment shows clear differences between the predictions obtained with different TMD models, both in the description of the full data set and in the case of individual structure functions. The best description of the structure functions data is obtained with one of the modified WW models. Our analysis can serve to identify the features of the TMD model that should be considered in future gluon TMD fits.

   hep-ph0 citations
3. 03*

   $b\to c$ semileptonic sum rule: SU(3)${}_{\mathrm{F}}$ symmetry violation

   Syuhei Iguro🇯🇵

   To clarify possible deviations in $b\to c\tau \overline{\nu }$ processes, the $b\to c$ semileptonic sum rule provides a valuable tool. This relation, derived based on heavy quark symmetry (HQS), offers a powerful consistency check among experimental results. In this work, we extend the previously proposed sum rule for $\{B\to D^{(\ast )}l\overline{\nu },{\Lambda }_b\to {\Lambda }_{c}l\overline{\nu }\}$ to include $\{B_s\to D_s^{(\ast )}l\overline{\nu },{\Xi }_b\to {\Xi }_{c}l\overline{\nu }\}$, thereby enabling more useful cross-checks. Although the relation is supported by HQS and SU(3) flavor symmetry, both symmetries are broken in reality, and the size of the violation needs to be quantified to assess the validity of the sum rule. While the violation is expected to be moderate based on chiral perturbation theory, we perform a numerical evaluation and compare it with future experimental sensitivities. We find that the violation remains smaller than the expected experimental uncertainty. Therefore another new physics agnostic and predictive sum rules are constructed to check the consistency.

   hep-phhep-ex3 citations
4. 04*

   Reply to "Comment on `Unified neutrino mixing and approximate $\mu -\tau$ reflection symmetry'[arXiv:2603.00885]''

   Yuta Hyodo🇯🇵 · Teruyuki Kitabayashi🇯🇵

   Huang and Li [arXiv:2603.00885] have raised the following two points regarding our previous work [arXiv:2502.18029]:(1) The real-value conditions associated with $\mu$-$\tau$ reflection symmetry were overlooked. (2) Inverted Ordering (IO) remains viable when the latest experimental data are taken into account. As they have pointed out, we overlooked an important real-value condition. However, with regard to point (2), we believe that there may be a misunderstanding. In our original study, we excluded IO based on the constraint on the sum of neutrino masses, $\sum m_{\nu }$. In contrast, they argue that IO remains viable when considering the effective neutrino mass, $|M_{ee}|$. While IO may indeed remain allowed in light of the latest $|M_{ee}|$ data, it is still in tension with the experimental bounds on $\sum m_{\nu }$ under approximate $\mu -\tau$ symmetry within the discussed model parameter space.

   hep-ph0 citations
5. 05*

   Gamma-Ray Signatures of Thermal Misalignment Dark Matter

   Koichi Hamaguchi🇯🇵 · Ryoichiro Hayakawa🇯🇵 · Hiroki Takahashi🇯🇵

   Thermal misalignment is a viable dark matter scenario where the misalignment of a dark matter scalar, feebly coupled to the Standard Model particles, is generated through thermal effects from the primordial plasma. In this framework, the scalar is generically metastable, and its decay can leave observable signatures. In this work, we focus on the case in which the scalar $\varphi$ is coupled to photons through $\varphi F^{\mu \nu }{F}_{\mu \nu }$, and examine its observational signatures. We find that current gamma-ray constraints place a robust upper bound on the scalar mass of $\mathcal{O}(1)\mathrm{GeV}$. We also find that future observations can further probe the parameter region, particularly in the MeV--GeV range, an energy band expected to be explored by various gamma-ray observatories in the coming decades.

   hep-ph0 citations
6. 06*

   Rare B meson decays in the Minimal R-symmetric Supersymmetric Standard Model

   Ke-Sheng Sun🇨🇳 · Kui-Wen Guan🇨🇳 · Hao-Yi Liu🇨🇳 · Jin-Lei Yang🇨🇳 · Tie-Jun Gao🇨🇳

   Taking into account the constraints imposed by experimental data on the parameter space, we analyze the lepton flavor violating decays of B meson in the scenario of the minimal R-symmetric supersymmetric standard model. The prediction of the branching ratios is strongly affected by $\tan \beta$ and the off-diagonal entries in the slepton and squark mass matrices. The off-diagonal entries in the slepton mass matrix are constrained by the experimental limits of radiative two body decays of leptons. The off-diagonal entries in the squark mass matrix are constrained by the experimental limits of low energy observables related to B meson physics. The branching ratio of $B_d^0\to \mu \tau$ is predicted to be four orders of magnitude below the future experimental sensitivity and the decay $B_d^0\to \mu \tau$ has a higher chance of being observed in the future.

   hep-ph0 citations
7. 07*

   Towards Testable Type-III Leptogenesis in Non-Standard Early Universe Scenarios

   Simran Arora🇮🇳 · Devabrat Mahanta🇮🇳

   Leptogenesis is an elegant way to explain the baryon asymmetry of the Universe in connection to the neutrino mass and mixing. Although leptogenesis from the decay of a heavy Majorana neutrino has been the minimal set up, it is also motivating to look for leptogenesis from the decay of triplet fermion as it can have detectable signatures in the experiments. However, due to strong gauge annihilations and constraints from neutrino sector, the triplet fermions have to be as heavy as $10^{10}$ GeV or more to generate the observed baryon asymmetry. While this prediction is based on the standard radiation dominated history of the early Universe, it is also possible to have a non-standard expansion history of the Universe prior to the big-bang nucleosynthesis. In this work we study triplet leptogenesis in two non-standard cosmological scenarios, where the Universe expands faster than radiation and a scalar tensor theory of gravity. We show that it is possible to have successful leptogenesis with a few TeV triplet fermion for fast expanding Universe and a few hundered TeV for a scalar tensor gravity theory.

   hep-ph0 citations
8. 08*

   Gauge coupling unification and doublet-triplet splitting via GUT dynamical breaking

   Isabella Masina🇮🇹 · Mariano Quiros🇪🇸

   An interesting framework to achieve gauge coupling unification consists in adding to the Standard Model Lagrangian non-renormalizable operators of $d\ge 5$, which affect the kinetic term of gauge fields. We first review the phenomenology related to this framework in the context of $SU(5)$, identifying which are the most interesting representations for the sake of achieving coupling unification. Secondly, we point out that in the case of a dynamical breaking pattern, it is possible to relate gauge coupling unification with the doublet-triplet splitting problem. We show that condensates of fermions in the $5$ representation do not lead to viable models because of proton decay constraints. At difference, we point out that successful models can be obtained by considering condensates of fermions in the $10$, as well as in the $24$ representations.

   hep-phhep-thPRD(2026)·0 citations
9. 09*

   Cosmological collider signals of modular spontaneous CP breaking

   Shuntaro Aoki🇯🇵 · Alessandro Strumia🇮🇹

   We consider a modular-invariant extension of the Standard Model. Assuming that the modulus is the inflaton, the CP-violating phases of the Yukawa couplings evolve during inflation. This dynamics favours a Higgs condensate, so that Standard Model fermions mediate a one-loop cosmological collider signal enhanced by chemical potentials. The effect appears too small for next-generation experiments. We provide precise expressions for Dirac fermions with chemical potentials in de Sitter.

   hep-phastro-ph.COhep-th6 citations
10. 10*

    Non-universality of color transparency onset in pion and kaon electroproduction

    Byung-Geel Yu🇰🇷 · Tae Keun Choi🇰🇷 · Kook-Jin Kong🇰🇷

    A combined analysis of the Jefferson Lab data on nuclear transparency in $A(e,e^{\prime }{\pi }^{+})$ and $A(e,e^{\prime }{K}^{+})$ shows that the onset of color transparency (CT) is not universal across meson flavors. The pion transparency is well reproduced by the standard quantum diffusion model (QDM) with $\Delta M_{\pi }^2\simeq 0.7$ GeV${}^2$, whereas the kaon data favor the quadratic expansion of the naive parton model (NPM) with the natural hadronic scale $R_K\sim \sqrt{{\sigma }_{KN}/\pi }$. This dichotomy cannot be repaired by physically motivated parameter choices: the pion slope excludes the quadratic expansion with any physical radius, and the kaon slope requires a QDM excitation scale far below the range conventionally used in pion transparency analyses. A microscopic interpretation, in which the diffusive evolution of the pion appears as an exceptional consequence of its Goldstone-boson nature while the kaon follows the generic ballistic expansion, is discussed.

    hep-phnucl-th0 citations
11. 11*

    Pion Parton Distribution Functions in the Light-Cone Quark Model and Experimental Constraints

    Hari Govind P · Satyajit Puhan🇮🇳 · Abhishek K.P · Reetanshu Pandey🇮🇳 · Harleen Dahiya🇮🇳 · Arvind Kumar🇮🇳 · Suneel Dutt🇮🇳

    In this work, we investigate the valence quark parton distribution functions (PDFs) of the pion within the light-cone quark model. The initial quark PDFs are calculated by solving the quark-quark correlation function for the pseudoscalar mesons. The initial quark PDFs have been evolved to higher energy scales through the Dokshitzer,Gribov,Lipatov,Altarelli,Parisi (DGLAP) evolution equations. We also find that our calculated evolved PDFs match experimental and available theoretical extraction data. For the first time, we have also predicted the $F_2$ structure function at next-to-leading (NLO) order accuracy. The calculated $F_2$ structure function has been compared with the available ZEUS and H1 experimental data at DESY-HERA over a wide range of energy scales. Additionally, we display the forward pion production cross-section for the Drell-Yan process caused by pions using the pion PDFs that were calculated and the target nucleon PDFs from the LHAPDF nucleus datasets. The evolved $F_2$ structure function of the pion have been studied at the upcoming electron-ion collider energy kinematics. Overall, it was observed that the quark PDFs of pions computed using the light-cone quark model consistent with the experimental results.

    hep-phPRD(2026)·2 citations
12. 12*

    Scalar axion field of toroidal electromagnetic pulses

    Wangke Yu🇸🇬 · Nikitas Papasimakis🇬🇧 · Nikolay I. Zheludev🇸🇬 · Yijie Shen🇸🇬

    Axion electrodynamics extends Maxwell's theory by postulating a hypothetical pseudoscalar axion field sourced by a scalar product of electric and magnetic fields. In this work, we demonstrate that a superposition of toroidal electromagnetic pulses propagating in free space naturally exhibits localized regions, where $\mathbf{E}\cdot \mathbf{B}\ne 0$. As a consequence of axion electrodynamics, these structured light pulses generate a space-time localized pseudoscalar field co-propagating with the pulses. This result should not be interpreted as a mechanism for generating axion particles by light, but rather as a consequence of adopting the axion electrodynamics extension to Maxwell's equations.

    hep-phphysics.class-phphysics.optics0 citations
13. 13*

    Thermodynamic and Transport Properties of Quark-Gluon Plasma at Finite Chemical Potential with a DNN framework

    Rishabh Kumar Tiwari🇮🇳 · Kangkan Goswami🇮🇳 · Suraj Prasad🇮🇳 · Captain R. Singh🇮🇳 · Raghunath Sahoo🇮🇳 · Mohammad Yousuf Jamal🇨🇳

    The characteristics of a thermal system depend strongly on its response to thermal gradients and the underlying microscopic interactions among constituents. In the present study, we investigate the thermodynamic and transport properties of the quark-gluon plasma (QGP) at finite baryon chemical potential within a deep-learning-assisted quasi-particle model (DLQPM). The temperature ($\mathrm{T}$) and baryon chemical potential (${\mu }_B$)-dependent thermal masses of quasi-particles are estimated using neural networks trained to reproduce lattice QCD (lQCD) results for the equation of state, obtained via a Taylor-like expansion around vanishing baryon chemical potential. The trained model acts as an effective emulator, enabling us to estimate the thermodynamic and transport properties at finite ${\mu }_B$. We compute the speed of sound, specific heat, viscosity, and conductivity of the deconfined medium. Our findings are in good agreement with available lattice calculations and other phenomenological models. The present study demonstrates that a DNN-based approach provides an efficient framework for studying the properties of the QGP at finite baryon density.

    hep-phhep-exhep-latnucl-ex+12 citations
14. 14*

    Doubly charged Higgs production within the Higgs triplet model at future electron-positron colliders

    Shu-Xiang Li🇨🇳 · Ren-You Zhang🇨🇳 · Ming-Hui Liu🇨🇳 · Xiao-Feng Wang🇨🇳 · Zhong-Yuan Liu🇨🇳 · Yi Jiang🇨🇳 · Liang Han🇨🇳 · Qing-hai Wang🇨🇳

    We investigate in detail the discovery potential of the doubly charged Higgs boson at the Compact Linear Collider in $e^{-}{e}^{-}$, $e^{-}\gamma$, $\gamma \gamma$, and $e^{+}{e}^{-}$ collision modes, within the Higgs triplet model at two extreme benchmark points as representatives of the Yukawa-like and gauge-like regions. In the Yukawa-like region, the most promising production mechanism is the single production via $e^{-}{e}^{-}$ and $e^{-}\gamma$ collisions. Given the subsequent decay of the doubly charged Higgs into a same-sign lepton pair, CLIC can achieve statistical significance well beyond the discovery threshold, within the parameter space permitted by experimental constraints. In the gauge-like region, with the ${\ell }^{\pm }{\ell }^{\pm }+\ge 3j$ final state, CLIC exhibits robust discovery potential for the doubly charged Higgs boson, up to a mass of approximately $1.2\mathrm{TeV}$. We also investigate the search for doubly charged Higgs at the HL-LHC. Our results demonstrate that CLIC possesses greater advantages and offers superior discovery potential for the doubly charged Higgs boson, compared to the HL-LHC.

    hep-ph1 citation
15. 15*

    Monte-Carlo Event Generation for X-Ray Thomson Scattering Analysis

    Uwe Hernandez Acosta🇩🇪 · Thomas Gawne🇩🇪 · Jan Vorberger🇩🇪 · Hannah Bellenbaum🇩🇪 · Anton Reinhard🇩🇪 · Simeon Ehrig🇩🇪 · Klaus Steiniger🇩🇪 · Michael Bussmann🇩🇪 · Tobias Dornheim🇩🇪

    A key diagnostic in warm-dense matter (WDM) experiments is X-ray Thomson scattering (XRTS), but its interpretation is often limited by complex instrument effects and the high computationally expensive combinations of microscopic models with detector simulations. We present a proof-of-principle implementation of an event-driven approach to XRTS modelling, inspired by particle physics event-generators. Instead of computing the spectra via forward models, individual scattering events are sampled from the differential cross section and sent through a spectrometer simulation. This provides a statistically consistent representation that preserves full kinematic information and enables flexible and geometry-aware analysis. We demonstrate the feasibility and physical consistency of the method for non-resonant XRTS in a synthetic setup. By decoupling event generation from detector-level analysis, the framework allows efficient reuse of the sampled events and reduces computational overhead associated with repeated evaluations. The method is model-agnostic and establishes a new connection between particle-physics event generation techniques and WDM diagnostics, providing a scalable foundation for advanced XRTS analysis and inference.

    hep-phphysics.plasm-ph0 citations
16. 16*

    Quarkyonic Meson Matter for Finite Isospin Density

    Larry McLerran🇺🇸

    QCD at finite isospin density is considered for a large number of colors $N_c$. A linear sigma model is used to model the meson content of the theory at low density. At isospin chemical potential ${\mu }_I<<{\Lambda }_{QCD}$, this matter forms a Bose condensate. For ${\mu }_I>>\sqrt{N_c}{\Lambda }_{QCD}$, unlike QCD remains confined, but the degrees of freedom of the system are mesons and Cooper pairs bound on size scales small compared to the QCD size scale determined by the superfluid gap. For most purposes this matter may be analyzed using weak coupling methods. For ${\Lambda }_{QCD}\le {\mu }_I\le \sqrt{Nc}{\Lambda }_{QCD}$, we argue that meson matter is quarkyonic, with quarks bound into mesons on a size scale of order ${\Lambda }_{QCD}$ corresponding to a filled Fermi sea of quarks, with possible Bose condensation at the Fermi surface and/or Cooper pairs with finite width of the surface of order ${\Lambda }_{QCD}$.

    hep-phActa Phys.Polon.B(2026)·1 citation
17. 17*

    The SUSY reach of Higgs Factories in the most challenging scenario: scalar $\tau$-leptons with lowest cross section and small mass differences

    Maria Teresa Núñez Pardo de Vera (1)🇩🇪 · Mikael Berggren (1)🇩🇪 · Jenny List (1) ((1) DESY, Hamburg, Germany)🇩🇪

    The direct pair-production of the $\tilde{\tau }$, is one of the most interesting channels to search for SUSY in: the $\tilde{\tau }$ is likely to be the lightest of the scalar leptons, and the signature of $\tilde{\tau }$ pair production is one of the experimentally most difficult ones, making it the ``worst'' possible scenario for SUSY searches. The current limit on $\tilde{\tau }$ production in the general MSSM comes from LEP. Limits obtained at LHC do extend to higher masses, but they are only valid under strong assumptions. Future $e^{+}{e}^{-}$ colliders will be powerful for SUSY searches, offering advantages with respect to previous $e^{+}{e}^{-}$ colliders as well as to hadron machines. In order to quantify their capabilities, the ``worst-case'' scenario for $\tilde{\tau }$ searches has been studied, taking into account the effect of the $\tilde{\tau }$ mixing on both $\tilde{\tau }$ production cross section and on detection efficiency. To evaluate the latter, the ILD detector concept, originally developed for the International Linear Collider (ILC), and the ILC beam conditions at a centre-of-mass energy of $500$\,GeV have been used for detailed simulations, including for the first time the effect of bunch-crossings containing no hard $e^{+}{e}^{-}$ interaction, but only low-$P_T$ hadrons from $\gamma \gamma$ interactions and $e^{+}{e}^{-}$ pairs from beamstrahlung. Still, the obtained exclusion and discovery reaches extend nearly up to the kinematic limit even in the worst-case scenario. This remains true also when the $\tilde{\tau }$ and the lightest SUSY particle are quite close in mass. The results of the detailed study are extrapolated to centre-of-mass energies, integrated luminosities and beam polarisations of other proposed Higgs factory projects and discussed in view of their respective experimental environments, in particular addressing the case of FCCee.

    hep-ph0 citations
18. 18*

    Hamiltonian Constraints on Spontaneous Lorentz Symmetry Breaking in the Bumblebee Model

    Jie Zhu🇨🇳 · Hao Li🇨🇳 · Zhi Xiao🇨🇳

    This study demonstrates that the common practice of determining spontaneous Lorentz violation via the minimum of a Lagrangian potential is generally incorrect. By analyzing the Hamiltonian structure and constraints of vector fields, we show that the true vacuum must be derived from the Hamiltonian density. We prove that the standard quadratic potential cannot consistently generate a vacuum expectation value (VEV), identifying a cubic potential as the simplest viable alternative. Furthermore, we prove that smooth potentials only support stable timelike or lightlike VEVs. These conclusions extend to higher-rank tensor fields and impose rigorous consistency constraints on higher-rank tensor fields and Lorentz-violating effective field theories.

    hep-phgr-qchep-th4 citations
19. 19*

    Mesonic modes in confining model at finite temperature

    A.E. Radzhabov🇷🇺 · X.L. Shang🇨🇳

    The mass spectrum of pseudoscalar and scalar meson modes at finite temperature is studied in the framework of a nonlocal quark model. The model implements quark confinement via the modification of the Laplace transform of the quark propagator. In order to synchronize the confining and deconfining phases, a modification of the transform is proposed. The behavior of the screening masses of mesons is studied in a wide region of temperatures, while the pole masses are described up to the deconfining phase transition.

    hep-phhep-thPRD(2026)·0 citations
20. 20*

    Experimental predictions of the $E_8\times \omega E_8$ octonionic unification program : A falsification-oriented catalogue for quantum foundations, particle physics, gravitation, and cosmology

    Tejinder P. Singh🇮🇳

    The $E_8\times \omega E_8$ octonionic unification programme makes empirical claims across quantum foundations, particle physics, gravitation, and cosmology. This catalogue assembles them as possible failure modes rather than a success list, classified by logical strength and distinctiveness. Standing entries include collapse in time with an attosecond cutoff, $m_{\tau }/m_{\mu }=m_s/m_d$, the first-generation $1:4:9$ pattern, and ${\alpha }_s(M_Z)/{\alpha }_{\mathrm{em}}(0)=16$. Version~2 upgrades every sector to the dedicated 2026 papers. Neutrinos: the v1 maximal leptonic phase, a removable-rephasing artifact, is corrected to conditional CP conservation, ${\delta }_{CP}^{\ell }\in \{0,\pi \}$; the minimal Majorana branch commits to inverted ordering with masses $(49.1,49.8,0.76)$~meV, $\Sigma m_{\nu }\simeq 0.10$~eV, $m_{\beta \beta }=18.2\pm 1.2$~meV; the three right-handed neutrinos become diluted $\sim 40$~eV relics closing the matter budget, with a two-epoch dark-radiation fingerprint ($\Delta N_{\mathrm{eff}}\simeq 0.19$ at BBN, $0.05$ at recombination). The second Higgs becomes a full electroweak quartet in a CP-conserving 2HDM near alignment, mass undetermined. Gravitational parity-blindness is derived via three screening theorems, residual violation confined to a quantified operator basket, with CMB TB/EB correlations observable if $r\gtrsim \text{few}\times 10^{-3}$ and a Galactic-supernova triple-timing test at $3\times 10^{-9}$. CKM: two of four degrees of freedom parameter-free ($|V_{us}|=0.237$, $|V_{cb}|=0.042$), the remainder one complex bridge element, fragilities disclosed. The Tsirelson-bound violation is recorded as mechanism-and-sign with magnitude underived, hence not yet falsifiable.

    hep-phgr-qcquant-ph3 citations
21. 21*

    Uncool soft-wall transitions and gravitational waves

    Ameen Ismail🇺🇸 · Lian-Tao Wang🇺🇸

    Theories with warped extra dimensions, like the Randall-Sundrum (RS) model, exhibit a holographic phase transition from a hot, deconfined black brane phase to a cool, confined phase. The standard picture of a first-order, strongly supercooled phase transition is expected to change in variations where the extra dimension is smoothly cut off by a soft-wall curvature singularity, as opposed to a hard brane. To understand this situation, we consider a simple ansatz for the warped geometry which allows us to obtain analytical results while maintaining the essential behavior of a soft wall. Unlike RS with the usual Goldberger-Wise stabilization, the hot, black brane phase only exists above a minimum temperature, which is not much smaller than the critical temperature. We explore the dynamics of the phase transition across the range of possibilities for the asymptotic geometry of a soft wall. This involves calculating an effective 4D action for the location of the black brane horizon. Using the effective action, we show that the phase transition completes rapidly ($\beta /H$ of $10^{3\text{-}4}$ is typical) and with only slight supercooling. We compute the resulting gravitational wave signal for a TeV-scale transition, finding that it is accessible to future space-based interferometers.

    hep-phhep-thJHEP(2026)·2 citations
22. 22*

    Dark Matter on a Slide

    Hsin-Chia Cheng🇺🇸 · Xu-Hui Jiang🇨🇳 · Lingfeng Li🇨🇳 · Ennio Salvioni🇪🇸

    We present a scenario for GeV-scale thermal dark matter that can only be tested with accelerator experiments. Dark matter is composed of dark pions arising from a confining strong interaction in the dark sector. The thermal relic density is obtained through the interplay of up-scatterings of dark pions to heavier dark mesons (the dark counterparts of the kaons and $\eta$), and decays of the unstable dark $\eta$ to Standard Model particles. This mechanism is analogous to a playground slide, where one climbs up first and then slides down with a release of energy. We illustrate the scenario with a minimal model based on the SU(3)/SO(3) coset, where dark matter is stabilized by a U(1) flavor symmetry. The correct relic density is obtained with dark meson mass splittings of 10% to 50% and a dark-$\eta$ lifetime shorter than $10^3\mathrm{m}/c$. Direct and indirect dark matter searches are mostly ineffective, as a consequence of the charge conjugation symmetry of the stabilizing U(1). The most striking signals arise at the LHC, from the production of dark showers containing long-lived dark $\eta$'s that decay to visible final states. These signatures crucially depend on the portal interaction connecting the dark sector to the Standard Model. We show that several well-known portals can complete the scenario above the weak scale, and outline the expected signals in each case.

    hep-phhep-ex1 citation
23. 23*

    Parametrized quasinormal modes, greybody factors and their correspondence

    Georgios Antoniou🇵🇹

    We present a detailed study of quasinormal modes and greybody factors in the context of the parametrized quasinormal mode framework, in which modifications to general relativity are introduced as small corrections in the potential. We deduce the QNMs' and GBFs' dependence on the order of the modifications and their polynomial power. We also test the validity of the recently proposed QNM-GBF correspondence in the pQNM framework by inspecting the regime at which it breaks down.

    ↳ gr-qchep-phhep-thClass.Quant.Grav.(2026)·2 citations
24. 24*

    A generic ${\omega }_b$ tension in early-time solutions to the Hubble tension

    Cara Giovanetti🇺🇸

    I show that early-time (pre-recombination) solutions to the Hubble tension are generically expected to increase the preferred baryon density ${\omega }_b$. This puts these models in tension with Big Bang Nucleosynthesis (BBN), as measurements of primordial deuterium constrain ${\omega }_b$ at percent level. I show that existing analyses are in tension with the BBN determination of ${\omega }_b$, and that including a likelihood component for primordial deuterium deters two representative models from recovering a high $H_0$.

    ↳ astro-ph.COhep-phJCAP(2026)·10 citations
25. 25*

    The double-logarithmic four-graviton Regge sector as a rank-two twisted period system

    Agustín Sabio Vera (Universidad Autónoma de Madrid, Instituto de Física Teórica UAM-CSIC)🇪🇸

    We study the double-logarithmic four-graviton Regge sector in $N$-extended supergravity. Its Mellin-space solution is already known in terms of parabolic-cylinder functions. We show that the same answer can be organized as a rank-two twisted period system, meaning that two closely related weighted integrals determine the full Mellin partial wave. These functions satisfy a simple pair of first-order differential equations and a recursion as the number of supersymmetries $N$ changes. This gives a uniform description of the full supergravity family, clarifies the relation between the positive-ray Euler integral and the earlier contour representation, and reproduces the same reduction rule through intersection theory. The reformulation also makes the special cases with four and six supersymmetries particularly transparent and yields a simple Hermite-polynomial construction for the low-even theories.

    ↳ hep-thhep-phJHEP(2026)·0 citations
26. 26*

    Species-dependent viscous corrections at particlization: A novel relaxation time approximation approach

    I. Aguiar🇧🇷 · T. Nunes da Silva🇧🇷 · G. S. Denicol🇧🇷 · M. Luzum🇧🇷 · G. S. Rocha🇧🇷 · C. Shen🇺🇸

    We assess the effects of a recently proposed generalized relaxation time approximation (RTA) for multi-species relativistic gases within a realistic numerical hybrid framework and study its phenomenological consequences in p-Pb and Pb-Pb collisions. The novel approximation introduces counter-terms to the collision kernel, allowing for momentum-dependent relaxation times ${\tau }_i(p)$ while preserving local energy-momentum conservation. As a consequence, the resulting first-order viscous corrections $\delta f_i$ to the phase-space distribution functions depend explicitly on the particle species mass $m_i$. We systematically investigate the impact of these species-dependent corrections on particle production at particlization, focusing on identified hadron yields and transverse momentum ($p_T$) spectra obtained from Cooper-Frye sampling. We find that the yields and spectra of light hadrons ($\pi ,K,p$) are significantly affected, leading to modifications of relative particle yields such as the $K/\pi$ and $p/\pi$ ratios. We show that these effects persist, albeit with reduced magnitude, after the inclusion of the hadronic cascade stage. In contrast, the impact on inclusive charged-particle observables is strongly reduced due to compensating enhancements and suppressions among different species. This controlled deformation of identified hadron observables, which selectively modifies flavor-sensitive quantities, makes the new prescription particularly well suited for Bayesian inference, as it introduces new sensitivity directions without spoiling existing constraints. Overall, our results demonstrate that species-dependent viscous corrections arising from the generalized RTA can leave significant and observable imprints on identified hadron production and relative yields, while remaining fully consistent with the successful description of bulk collective flow observables.

    ↳ nucl-thhep-ph0 citations
27. 27*

    Constraints on the Injection of Radiation in the Early Universe

    Melissa Joseph🇺🇸 · Jason Kumar🇺🇸 · Pearl Sandick🇺🇸

    We consider the generic injection of radiation (both dark and electromagnetic) during the epoch between big bang nucleosynthesis (BBN) and recombination. The contribution of the additional radiation to the number of effective neutrinos may be quite small in this scenario, since dark radiation and electromagnetic radiation provide contributions of opposite sign. However, the injection of electromagnetic radiation dilutes the baryon-to-entropy ratio, which is measured both at BBN and at recombination. As a result, this scenario is expected to be tightly constrained. Indeed, performing a numerical study, we find that the allowed amount of extra radiation may be no more than $\sim 25\%$ greater than in the case where it is assumed to be entirely dark radiation.

    ↳ astro-ph.COhep-ph1 citation
28. 28*

    Equilibrated fraction of QCD matter in high-energy oxygen--oxygen collisions

    Naoya Ito🇯🇵 · Tetsufumi Hirano🇯🇵

    We quantify to what degree the QCD matter created in high-energy oxygen--oxygen ($\mathrm{O}+\mathrm{O}$) collisions at $\sqrt{s_{NN}}=5.36$ TeV reaches a locally equilibrated state. For this purpose, we employ a novel framework based on the core--corona picture that describes the dynamics of both locally equilibrated fluids (the core) and nonequilibrium particles (the corona). Contributions from the core become larger than those from the corona above charged-particle multiplicity at midrapidity, $⟨d{N}_{\mathrm{ch}}/d\eta {⟩}_{|\eta |<0.5}\approx 20$. We also find that nonnegligible contributions from the corona still remain even in central $\mathrm{O}+\mathrm{O}$ collisions. The yield ratios of strange baryons to charged pions exhibit an increasing behavior with increasing multiplicity at midrapidity. However, these ratios are smaller than those obtained when assuming that QCD matter has reached complete chemical equilibrium. These results demonstrate that a purely hydrodynamic approach is insufficient and that the inclusion of a corona component is essential for describing the dynamics of intermediate-size systems such as $\mathrm{O}+\mathrm{O}$ collisions.

    ↳ nucl-thhep-phnucl-exPRC(2026)·2 citations
29. 29*

    Probing the chiral magnetic effect via transverse spherocity event classification in relativistic heavy-ion collisions

    Somdeep Dey🇮🇳 · Abhisek Saha🇨🇳

    We present the first study of the Chiral Magnetic Effect (CME) using transverse spherocity as an event-shape classifier in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV, simulated with the A Multi-Phase Transport (AMPT) model with a realistic CME implementation. Transverse spherocity separates events into jetty and isotropic topologies based on the geometric distribution of transverse momentum. Unlike traditional event shape engineering methods, which use the flow vector as an event classifier that is itself contaminated by the very backgrounds it is intended to suppress, spherocity provides a cleaner, geometry-driven classification that avoids this circular limitation. CME inclusion shifts the spherocity distribution toward more isotropic events, confirming its sensitivity to CME-induced charge separation. The charge-dependent azimuthal correlator $\Delta \gamma$ and correlated background coupled with elliptic flow are consistently higher in jetty events. The scaled ratio $\Delta \gamma /v_2$ shows enhanced values for isotropic events, confirming effective background suppression after elliptic flow scaling. Our results demonstrate that isotropic event selection via transverse spherocity provides a cleaner and more reliable environment for CME searches by simultaneously suppressing flow-driven and resonance-decay backgrounds, making it a powerful complementary method to existing flow-vector-based methods.

    ↳ nucl-exhep-phnucl-th0 citations
30. 30*

    Probing the Evolution of Dark Energy: A Joint Analysis of DESI DR2, Pantheon+, and Cosmic Chronometers

    Chanchal Kumari🇮🇳 · Dinesh Kumar🇮🇳

    We investigate several phenomenological dark energy parameterizations using a joint analysis of late-time cosmological observations, including cosmic-chromatometer measurements of the Hubble parameter, DESI DR2 baryon acoustic oscillation data, and the Pantheon+ Type Ia supernova sample. Our results show that allowing for a time-varying dark energy equation of state significantly improves the overall fit compared to $\Lambda$CDM. The present-day equation-of-state parameter departs from the standard cosmological constant value. In contrast, the evolution parameter in two-parameter models tends to be negative, indicating a possible time dependence of dark energy. However, the constraints on the evolution remain moderate, and current data cannot clearly distinguish the specific functional form of dark energy. Model comparison using information criteria suggests that dynamical dark energy models are favored over $\Lambda$CDM, with the most straightforward one-parameter extension emerging as the most parsimonious scenario. These findings indicate a mild preference for dark energy evolution, though future high-precision observations will be required for definitive conclusions.

    ↳ astro-ph.COhep-ph0 citations
31. 31*

    $\mathcal{N}=4$ supersymmetric Yang-Mills thermodynamics to order ${\lambda }^{5/2}$

    Margaret E. Carrington🇨🇦 · Gabor Kunstatter🇨🇦 · Ubaid Tantary🇸🇦

    We calculate the resummed perturbative free energy of $\mathcal{N}=4$ supersymmetric Yang-Mills in four spacetime dimensions (SYM${}_{44}$) to order ${\lambda }^{5/2}$ in the 't Hooft coupling at finite temperature and zero chemical potential. All infrared divergences cancel when we include contributions from SYM${}_{44}$ ring diagrams and the final result is both ultraviolet and infrared finite. Our result has special significance since order ${\lambda }^{5/2}$ is the highest order calculation that can be done with perturbation theory, because there are nonperturbative effects associated with the magnetic mass scale that come into play at order ${\lambda }^3$. We compare results obtained with regularization by dimensional reduction (RDR), which preserves supersymmetry, and canonical dimensional regularization (DR). We also compare with a generalized Padé approximant constructed by matching the weak coupling result at order ${\lambda }^2$ and the large $N_c$ strong coupling result at order ${\lambda }^{-3/2}$. Finally we make a comparison between our result and the QCD free energy and show that SYM${}_{44}$ has better convergence properties.

    ↳ hep-thhep-phnucl-thPRD(2026)·2 citations
32. 32*

    Background Fields Meet the Heat Kernel: Gauge Invariance and RGEs without diagrams

    Debanjan Balui🇮🇳 · Joydeep Chakrabortty🇮🇳 · Christoph Englert🇬🇧 · Subhendra Mohanty🇮🇳 · Tushar🇮🇳

    We introduce a new method that exploits the combination of the Heat Kernel (HK) and Background Field Method to compute gauge-invariant and gauge parameter-independent quantities such as the effective potential, anomalous dimensions, and renormalization group equations. In contrast to currently employed techniques, these results are obtained exclusively from the dynamics of the background fields, without relying on supplementary input from, e.g., traditional diagrammatic calculations. This is achieved by a consistent treatment of open and closed derivatives in the HK expansions. In this way, we compute the standard quantities such as $\beta$ functions and their gauge-parameter independence when background fields are on-shell. We demonstrate this formalism for instructive examples such as Scalar QED and Yukawa theory. Full results for the bosonic part of the Standard Model provide further validation of our approach.

    ↳ hep-thcond-mat.stat-mechhep-phPRD(2026)·3 citations
33. 33*

    Beam energy dependence of identified particle production in heavy-ion collisions using a parton-hadron string dynamics model

    Towseef Bhat🇮🇳 · Vipul Bairathi🇨🇱 · Lokesh Kumar🇮🇳 · Sonia Kabana🇨🇱

    We report predictions for the transverse momentum ($p_T$) spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$ in various collision centrality from Au + Au collisions at beam energies ($E_{lab}$) of 6.7, 8, 11, and 25 A~GeV using a parton-hadron string dynamics (PHSD) transport model. We studied the dependence of particle yields ($dN/dy$), mean transverse momenta ($⟨p_T⟩$), and particle ratios on collision energy and centrality to understand the underlying mechanisms of particle production. A comparison of the PHSD model results with available experimental measurements provides a qualitative description of these observables. Our results highlight the importance of baryon stopping, strangeness production, pair production, and baryon-antibaryon annihilation in the high baryon density region. These findings also provide theoretical insights relevant to the ongoing beam energy scan program at RHIC and the future heavy-ion programs at FAIR and NICA.

    ↳ nucl-thhep-exhep-phnucl-ex0 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.