Mon·Feb 9, 2026Monday·February 9, 2026

1. 01*

   Probing Extended Higgs Sectors via Multi-Top Events from Higgs Pair Decays in 2HDM Type-I at the HL-LHC

   Ijaz Ahmed🇵🇰 · M.Ibad🇵🇰 · Farzana Ahmad🇰🇷 · Jamil Muhammad🇰🇷

   This study investigates the production of multi-top quark events final states containing up to four top quarks as a probe for new physics beyond the Standard Model (SM) within the framework of the Two Higgs Doublet Model (2HDM) Type-I. Focusing on the High-Luminosity Large Hadron Collider (HL-LHC) at a center-of-mass energy of $\sqrt{s}=14$TeV, we analyze associated production processes including $pp\to t\bar{t}H$, $pp\to t\bar{t}A$, $pp\to HA$, $pp\to H{H}^{\pm }$, and $pp\to A{H}^{\pm }$. The simulation pipeline incorporates theoretical constraints and branching ratios. By targeting these high-multiplicity final states, the research aims to establish the sensitivity of the HL-LHC to an extended Higgs sector, utilizing the top quark's unique coupling to the scalar field as a primary discovery channel. The analysis is centered on two benchmark points characterized by a degenerate mass spectrum ($m_H=m_A=m_{H^{\pm }}=500$GeV) in the alignment limit ($\sin (\beta -\alpha )\to 1$), with $\tan \beta$ varied between 1 and 3. Event selection was performed with stringent cuts on jet multiplicity to suppress dominant SM backgrounds, such as $t\bar{t}W$, $t\bar{t}Z$, and $WWZ$. Our results indicate that signal significance improves substantially as the integrated luminosity increases from $3000f{b}^{-1}$ to $4000f{b}^{-1}$, with all investigated channels exceeding the $5\sigma$ discovery threshold.

   hep-ph0 citations
2. 02*

   Transeverse-Momentum Subtraction for Semi-Inclusive Deep-Inelastic Scattering

   Jun Gao🇨🇳 · Hai Tao Li🇨🇳 · Hua Xing Zhu🇨🇳 · Yu Jiao Zhu🇩🇪

   Semi-Inclusive Deep-Inelastic Scattering provides unique access to the three-dimensional momentum and spin structure of the proton, enabling precise studies of parton dynamics and hadronization in QCD. We present a transverse-momentum subtraction approach applied to the detected hadron that enables efficient and precise calculation of higher-order QCD corrections to identified hadron production in Semi-Inclusive Deep-Inelastic Scattering. We demonstrate the success of the method through a next-to-next-to-leading order QCD calculation and provide fully differential phenomenological applications, which provide important ingredients for global analyses of fragmentation functions. Our method is applicable to next-to-next-to-next-to-leading order QCD corrections for both unpolarized and polarized semi-inclusive deep-inelastic scattering.

   hep-phhep-ex3 citations
3. 03*

   CoLLM: AI engineering toolbox for end-to-end deep learning in collider analyses

   W. Esmail🇩🇪 · A. Hammad🇯🇵 · M. Nojiri🇯🇵

   Recent improvements in large language models have opened new opportunities for accelerating and automating scientific workflows. In parallel, modern collider analyses are becoming increasingly complex and demand substantial programming and deep learning expertise. \coll alleviates this workload by using pretrained large language models to generate physically consistent analysis code for event selection. Additionally, it automates subsequent deep learning analyses. To further reduce reliance on programming or deep learning experience, \coll provides a graphical user interface that allows users to perform end-to-end analyses through an interactive interface. The main motivation behind \coll is to lower the coding burden and simplify the technical complexity of collider analyses, which increasingly depend on sophisticated event selections and advanced deep learning methods.

   hep-ph13 citations
4. 04*

   CP violation angles from H$\to \tau \tau$ decays at FCC-ee

   Sofia Giappichini🇩🇪 · Markus Klute🇩🇪 · Matteo Presilla🇩🇪

   Measuring charge-parity (CP) violation in Higgs-fermion interactions is a key target of future precision Higgs programs. The decay $H\to \tau \tau$ is particularly sensitive to the CP structure of the Higgs Yukawa coupling via $\tau$ spin correlation, while the clean environment of $e^{+}{e}^{-}$ collisions at the Future Circular Collider (FCC) enables accurate reconstruction of CP-sensitive observables. In this letter, we study the sensitivity of FCC-ee to the Higgs CP state using $H\to \tau \tau$ events produced in associated $ZH$ production at $\sqrt{s}=240$ GeV. In the anomalous-coupling parametrization, we project a precision of $\Delta {\varphi }_{\tau \tau }=\pm 2.5^{\circ }$ at 68 % CL, with the dominant contribution arising from one-prong hadronic $\tau$ decays. We further interpret the analysis in the Effective Field Theory framework, deriving expected limits on the CP-odd operators, and compare them with electron and magnetic dipole moment measurements and the anomalous-coupling approach.

   hep-phPRD(2026)·2 citations
5. 05*

   Chiral phase transition with primordial black holes: Distinct phase structure and catalysis

   Masanori Tanaka🇨🇳 · Jun-Chen Wang🇨🇳 · Jing-Jun Zhang🇨🇳

   We study the impact of primordial black holes (PBHs) on the chiral phase transition and its associated stochastic gravitational-wave (GW) signals. Using the three-flavor Nambu-Jona-Lasinio model, we construct the chiral effective potential in a Schwarzschild spacetime background. We find that PBHs promote chiral symmetry restoration and induce a nontrivial local phase structure in the vicinity of the event horizon simultaneously. In particular, this structure exhibits a novel chiral symmetry breaking pattern involving both second- and first-order phase transitions, a feature absent in flat spacetime. We further demonstrate that PBHs act as genuine catalysts for the chiral phase transition by analyzing the bounce solution in curved spacetime. The presence of PBHs substantially enhances the inverse duration parameter $\beta /H$ while leaving the overall transition strength comparable to that in flat spacetime. As a consequence, even a small population of PBHs can induce $\mathcal{O}(1)$ shifts in both the peak frequency and the peak amplitude of the GW spectrum generated by the first-order dark chiral phase transition.

   hep-phastro-ph.HEgr-qc4 citations
6. 06*

   Return of the CHAMPs: A clockwork portal to charged dark matter

   Debajyoti Choudhury🇮🇳 · Vineet K. Jha🇮🇳 · Suvam Maharana🇮🇳

   While Dark Matter (DM) is conventionally assumed to be chargeless, the possibility of a charged massive particle (CHAMP) as the DM particle remains alive. With phenomenological constraints on the charge being very severe, such a scenario is often sought to be dismissed, citing naturalness. Moreover, the establishment of the correct relic density is often a concern. We demonstrate here that such a (mini)charged DM can yet be realized within the clockwork paradigm, without the need to invoke unnaturally small parameters. The model is examined against constraints, theoretical and experimental, and the phenomenologically admissible parameter space is delineated. Several intriguing tests, at the LHC as well as at future direct and indirect detection experiments, are pointed out.

   hep-phhep-thJHEP(2026)·0 citations
7. 07*

   C-parity and Regge Intercepts

   Vladimir A. Petrov🇷🇺

   In this work, we obtain constraints on the intercepts of the leading Regge pole trajectories- Pomeron and Odderon- implies by C-parity and based on the heuristic argument that C-even exchanges correspond to attractive forces be tween hadrons undergoing elastic scattering, and C-odd exchanges correspond to attractive forces in the case of particle-antiparticle scattering and repulsive forces in the case of particle-particle scattering. In addition, the case of secondary degenerate trajectories is also considered and a lower bound for their intercept is obtained

   hep-ph2 citations
8. 08*

   Physics of strong electromagnetic fields in relativistic heavy-ion collisions

   Koichi Hattori🇨🇳

   I discuss several roles of the strong electromagnetic fields created by relativistic heavy-ion collisions. These phenomena call for theoretical and experimental developments to understand dynamics of quark-gluon plasma (QGP) as well as purely electromagnetic processes in the ultraperipheral collisions.

   hep-phnucl-thJ.Subatomic Part.Cosmol.(2026)·0 citations
9. 09*

   Spin Light of neutrino in polarized matter

   Alexander Grigoriev🇷🇺 · Alexei Ternov🇷🇺

   The Spin Light of neutrino ($SL\nu$) is an electromagnetic radiation of the neutrino magnetic moment emitted when neutrino moves in external conditions (fields or matter). The effect can be of significance in the extremely dense matter of compact astrophysical objects such as neutron stars (NS). If detected, this radiation could provide a fair opportunity to study the properties of neutrinos and the medium through which they move, since the properties of the radiation depend on both. Motivated by the possibility of the nuclear matter spin-polarization, in this paper, we study the new properties to $SL\nu$ obtained under the influence of net matter polarization. We demonstrate that the polarization can enhance or completely suppress the radiation. Also, it introduces a characteristic asymmetry into the total radiation from the compact object, which could be an observable feature dependent on the matter polarization and the magnetic field inside the stellar (if the field is connected to the stellar matter polarization). The research may have implications for the physics of NS and magnetars, bringing us closer to the possibility of studying their internal structure.

   hep-phastro-ph.HE0 citations
10. 10*

    Cavity, lumped-circuit, and spin-based detection of axion dark matter: differences and similarities

    Deniz Aybas🇹🇷 · Hendrik Bekker🇩🇪 · Dmitry Budker🇩🇪 · Wei Ji🇩🇪 · On Kim🇺🇸 · Younggeun Kim🇩🇪 · Derek F. Jackson Kimball🇺🇸 · Jia Liu🇨🇳 · Xiaolin Ma🇨🇳 · Chiara P. Salemi🇺🇸 · Yannis K. Semertzidis🇰🇷 · Alexander O. Sushkov🇺🇸 and 3 other authors

    Axions and axion-like particles are compelling candidates for ultralight bosonic dark matter, forming coherent oscillating fields that can be probed by experiments known as haloscopes. A broad range of haloscope concepts has been developed, including resonant cavity haloscopes, lumped-element circuit detectors, and spin-based experiments, each sensitive to different axion couplings and mass ranges. Rather than attempting an exhaustive survey of all existing approaches, this comparative review provides a unified framework for the major haloscope classes, establishing a common language for the descriptions of signal generation, noise properties, data analysis, and scanning strategies. Key properties of ultralight bosonic dark matter relevant for detection are summarized first, including coherence time, spectral linewidth, and stochasticity under the standard halo model. The discussion then compares cavity, Earth-scale, lumped-element, and spin haloscopes, focusing on expected signal shapes, dominant noise sources, and statistical frameworks for axion searches. Particular emphasis is placed on consistent definitions of signal-to-noise ratio and on how detector bandwidth, axion coherence, and noise characteristics determine optimal scan strategies. By systematically comparing operating principles and performance metrics across these detector families, this framework clarifies shared concepts as well as the essential differences that govern sensitivity in different mass and coupling regimes. The resulting perspective synthesizes current search methodologies and offers guidance for optimizing future haloscope experiments.

    hep-phhep-exUniverse(2026)·4 citations
11. 11*

    Direct Detection and Cosmological Constraints of Dark Matter with Dark Dipoles

    Takumi Kuwahara🇨🇳 · Jun-Chen Wang🇨🇳 · Shu-Run Yuan🇨🇳

    We study a fermionic dark matter candidate that couples to the standard model particles exclusively through electric and magnetic dipole operators mediated by a massive dark photon. Such dipole portals naturally arise in dark sectors where the dark matter is neutral under a hidden $U(1{)}_D$, and they lead to phenomenology distinct from conventional vector-current interactions. We consider the direct-detection signals arising from dark matter-nucleus scattering including the Migdal effect, dark matter-electron scattering, and semiconductor targets, which allow sensitivity to sub-GeV dark matter masses, together with the cosmological bounds from such as thermal relic abundance, cosmic microwave background, big-bang nucleosynthesis, and cosmic-rays. We find that the dark dipole coupling can be largely constrained by direct detection (in particular, electric dipole coupling). However, the cosmological observations have already constrained most of the parameter space, in particular for magnetic dipole interactions of $U(1{)}_D$ for sub-GeV dark matter. For the dark matter mass below 10 MeV, the semiconductor (in particular, using skipper-CCD) experiments can play a crucial role in probing the dark dipole interactions: future low-threshold experiments utilizing the semiconductor targets can further extend the constraints. Our results have demonstrated that the sub-GeV dark matter with dark dipole interactions can be still safe from the direct-detection constraints, and the future low-threshold semiconductor experiments may play a significant role in constraining the dark dipole interactions.

    hep-phJHEP(2026)·1 citation
12. 12*

    Study of $B\to K_0^{\ast }(1430){\ell }^{+}{\ell }^{-}$ decay in the standard model and scalar leptoquark scenario

    M. Dadashzadeh🇮🇷 · K. Azizi🇮🇷

    This study examines the rare decay $B\to K_0^{\ast }(1430){\ell }^{+}{\ell }^{-}$ as a possible probe for new physics beyond the standard model (SM). We first analyze this channel within the SM and then include scalar leptoquark (LQ) contributions. We provide predictions for key observables, like differential decay rate, branching ratio, ratio of branching fractions at different channels, forward-backward asymmetry and different lepton polarizations, and assess their sensitivity to leptoquark scenarios, highlighting $q^2$ regions less affected by the long-distance charmonium effects. The results can be useful for future Belle II and LHCb measurements.

    hep-phhep-exhep-latPRD(2026)·0 citations
13. 13*

    MadSpace -- Event Generation for the Era of GPUs and ML

    Theo Heimel🇧🇪 · Olivier Mattelaer🇧🇪 · Ramon Winterhalder🇮🇹

    MadSpace is a new modular phase-space and event-generation library written in C++ with native GPU support via CUDA and HIP. It provides a unified compute-graph-based framework for phase-space construction, adaptive and neural importance sampling, and event unweighting. It includes a wide range of mappings, from the standard MadGraph multi-channel phase space to optimized normalizing flows with analytic inverse transformations. All components operate on batches of events and support end-to-end on-device workflows. A high-level Python interface enables seamless integration with machine-learning libraries such as PyTorch.

    hep-ph11 citations
14. 14*

    QED Effects in PDFs -- A Les Houches Comparison Study

    Thomas Cridge🇧🇪 · Juan Cruz Martinez🇪🇸 · Joey Huston🇺🇸

    In the last decade, and even more so in the last few years, our knowledge of the internal structure of the proton has become more accurate and precise thanks to the large amount of data available and developments in theory and methodology. The reduction of the uncertainties associated to these developments has brought previously neglected effects into focus as their typical magnitude are competitive with the size of the uncertainties. One such effect is the inclusion of QED into PDF fits. Typically this is a percent effect, and thus while theoretically important, it has had a relatively limited impact on phenomenological studies up to this point. In this proceeding we study some of the effects which, while peripheral to the inclusion of QED in the proton, can considerably change the relative size and shape of the QCD+QED fit with respect to the QCD only determination. These may become important in the future as precision continues to increase. After a comparison of the QCD+QED PDFs with the QCD only PDFs of various global PDF fitting groups, we focus largely upon NNPDF4.0, which shows the biggest effect when including QED. Focusing largely on a single set of PDFs also enables more subtle effects to be analysed, making it an ideal candidate for this study.

    hep-ph2 citations
15. 15*

    Parametric-Resonance Production of QCD Axions

    Pirzada🇨🇳 · Yu Gao🇨🇳 · Qiaoli Yang🇨🇳

    Dark matter axion production can be significantly enhanced through a generic cosmological mechanism: primordial temperature fluctuations periodically modulate the axion mass during the QCD phase transition, thereby triggering parametric resonance in axion field evolution. This interplay between the resonance and the misalignment mechanism moves the predicted axion mass window for the observed dark matter abundance to $10^{-4}-10^{-3}\text{eV}$, shifting the preferred mass to previously unexplored higher ranges.

    hep-phastro-ph.COhep-exPLB(2026)·9 citations
16. 16*

    Revisiting the Electroweakino Sector of the Baryon Number Violating MSSM at the HL-LHC with Deep Neural Networks

    Rahool Kumar Barman🇯🇵 · Arghya Choudhury🇮🇳 · Subhadeep Sarkar🇮🇳

    We study the projected sensitivity of direct electroweakino production $pp\to {\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0$ at the HL-LHC in a simplified framework with wino-like, mass degenerate ${\tilde{\chi }}_1^{\pm }$ and ${\tilde{\chi }}_2^0$, and a bino-like lightest neutralino ${\tilde{\chi }}_1^0$, assuming R-parity violating~(RPV) through the baryon number violating ${\lambda }_{112}^{\prime \prime }{u}^c{d}^c{d}^c$ and ${\lambda }_{113}^{\prime \prime }{u}^c{d}^c{b}^c$ operators. We consider three channels with the ${\lambda }_{112}^{\prime \prime }{u}^c{d}^c{d}^c$ RPV operator: $Wh$ mediated $1\ell +2b+\mathrm{E}{/}_{\mathrm{T}}$, $Wh$ mediated $1\ell +(\ge 2j)+2\gamma +\mathrm{E}{/}_{\mathrm{T}}$, and $WZ$ mediated $3\ell +(\ge 2j)+\mathrm{E}{/}_{\mathrm{T}}$. In each channel, we train benchmark-specific multi-layer perceptrons (MLPs), analogous to signal-region classifiers, on the four-momenta of the final state particles along with a small set of higher-level observables to distinguish the signal from the dominant SM backgrounds. We find that the HL-LHC will be able to probe winos up to $\sim 900$GeV, $\sim 780$GeV, and $\sim 880$GeV in the $Wh$ mediated $1\ell +2b+\mathrm{E}{/}_{\mathrm{T}}$, $Wh$ mediated $1\ell +(\ge 2j)+2\gamma +\mathrm{E}{/}_{\mathrm{T}}$, and $WZ$ mediated $3\ell +(\ge 2j)+\mathrm{E}{/}_{\mathrm{T}}$ channels, respectively, for $m_{{\tilde{\chi }}_1^0}\sim 50$GeV, in the presence of ${\lambda }_{112}^{\prime \prime }{u}^c{d}^c{d}^c$ couplings, at $2\sigma$ sensitivity. In case the ${\lambda }_{113}^{\prime \prime }{u}^c{d}^c{b}^c$ operator is solely switched on, the projected sensitivity for winos reach up to $\sim 700$GeV for $Wh$ mediated $1\ell +(\ge 1b)+(\ge 1j)+2\gamma +\mathrm{E}{/}_{\mathrm{T}}$ and $\sim 850$GeV for the $WZ$ mediated $3\ell +(\ge 1b)+\mathrm{E}{/}_{\mathrm{T}}$ channel.

    hep-ph2 citations
17. 17*

    Hard thermal contributions to phase transition observables at NNLO

    Fabio Bernardo🇨🇭 · Mikael Chala🇪🇸 · Luis Gil🇪🇸 · Philipp Schicho🇨🇭

    To construct the high-temperature effective field theory of gauge-Higgs models up to $\mathcal{O}(g^6)$ in the gauge coupling, we integrate out hard modes to three-loop level and use the next-to-next-to-leading order effective potential. For the Abelian Higgs model, we quantify the impact of both higher-dimensional operators and higher-loop corrections on thermodynamic parameters relevant for gravitational-wave observables, finding that one-loop dimension-six effects typically dominate over two- and three-loop corrections to super-renormalizable parameters for the strongest transitions. We derive the three-loop scalar and Debye masses for the $\mathrm{U}(1)$ and $\mathrm{SU}(N)$ gauge-Higgs models, as well as the two-loop quartic couplings for the Abelian case, show gauge independence of physical parameters, and demonstrate that no new master integrals are required for the matching, while consistency of 4d and 3d renormalizability points to previously missing contributions in these master integrals. As a byproduct, we report a previously missing contribution to the three-loop QCD Debye mass.

    hep-phhep-thJHEP(2026)·11 citations
18. 18*

    Assessing the Impact of Fitting Methodology at aN${}^3$LO with FPPDF: an Open Source Tool for Extracting Parton Distribution Functions in the Hessian Approach

    J. M. Cruz-Martinez🇪🇸 · T. Giani🇮🇹 · L. A. Harland-Lang🇬🇧

    We present a new public code, FPPDF, to perform global fits of parton distribution functions (PDFs). The fitting methodology follows that implemented by the MSHT collaboration, namely applying a fixed polynomial parameterisation of the PDFs and Hessian approach to error propagation, while for data and theory settings the libraries used by the NNPDF collaboration are taken. This therefore complements the already publicly available NNPDF fitting code to enable fits with both neural network and fixed polynomial PDF parameterisations to be performed by the community, with otherwise identical theoretical and experimental inputs. As a first application, we use the new code to compare the PDFs found from fits at both NNLO and aN${}^3$LO perturbative orders, but applying these two fitting approaches. We assess the impact of the two different methodologies on the PDFs and their uncertainties, providing results that complement previous comparisons between published PDF sets at NNLO and aN${}^3$LO. We in particular find that the relative impact of going to the higher perturbative order and/or including missing higher order uncertainties is rather insensitive to which of these PDF parameterisation methodologies are used.

    hep-phhep-exJHEP(2026)·3 citations
19. 19*

    Holographic Charged Transport with Higher Derivatives

    Alex Buchel🇨🇦 · Sera Cremonini🇺🇸 · Mohammad Moezzi🇺🇸 · George Tringas🇺🇸

    We compute the first-order hydrodynamic transport coefficients (shear viscosity $\eta$, bulk viscosity $\zeta$, and charge conductivity $\sigma$) for a broad class of strongly coupled, four-dimensional charged relativistic gauge theory plasma with holographic gravitational duals containing higher-derivative corrections. The landscape of our holographic models captures non-conformal gauge theories with an arbitrary number of relevant coupling constants and a general scalar potential in the gravitational dual, allowing for a systematic exploration of charged transport along generic holographic RG flows. The leading-order higher-derivative corrections probe gauge theories with non-equal central charges $c\ne a$ at the ultraviolet fixed point, and enable the engineering of diverse temperature and charge density profiles for the viscosities and the conductivity. Our results establish the membrane paradigm in higher-derivative holographic models: all the transport coefficients are extracted from the black brane horizon values of the gravitational scalars, and various functions defining the gravitational holographic dual.

    ↳ hep-thcond-mat.str-elhep-phnucl-thJHEP(2026)·3 citations
20. 20*

    Primordial Black Hole signatures from femtolensing and spectral fringe of Gamma Ray Bursts

    Chang-Yu Dai🇹🇼 · Po-Yan Tseng🇹🇼

    Femtolensing of gamma-ray bursts (GRBs) is vastly studied to constrain primordial black holes lighter than $10^{-13}$ solar mass and may close the window for PBH dark matter. In this case, wave optics formalism is required and carefully implemented in our analysis. Incorporating the GRB observational data from Swift XRT, we perform the statistical analysis of PBH lensing, comparing it with the null hypothesis where the BAND model is used to parametrize the GRB spectrum. We found a few GRB data manifest the spectral fringe which characterizes the feature of femtolensing by PBHs, and the analysis shows moderate statistical preference in terms of goodness of fit. Conversely, since most of the fits to GRB spectral data do not improve with PBH lensing, we utilize this to obtain an upper bound on the PBH fractional abundance with respect to dark matter. However, the robust constraint cannot be achieved, unless the size of GRBs is smaller than $5\times 10^7$ m for PBH mass around $5\times 10^{-15}$ solar mass.

    ↳ astro-ph.HEhep-phJHEAp(2026)·0 citations
21. 21*

    Super-knee cosmic rays from interacting supernovae

    Nick Ekanger🇯🇵 · Shigeo S. Kimura🇯🇵 · Kazumi Kashiyama🇯🇵

    There is increasing evidence that, in the very late phase of stellar evolution before core collapse, massive stars have winds with large mass loss rates that give rise to a dense circumstellar medium (CSM) surrounding the progenitor star. After core collapse, a shock wave forms when the supernova ejecta interacts with this CSM. In such an interaction, the nuclei in the CSM can undergo diffusive shock acceleration and reach very high energies. We consider such a model, which includes magnetic field amplification from the non-resonant streaming instability, enhancement to the abundance of heavy-ions, and composition-dependent acceleration. Applying this to several supernova subclasses, we find that IIn supernovae can supply a dominant fraction of the observed super-knee cosmic-ray (CR) flux from $\sim \mathrm{few}\times 10^{15}\mathrm{eV}$ to $\sim \mathrm{few}\times 10^{17}\mathrm{eV}$ and is consistent with recent LHAASO measurements above the CR knee. This systematic model also explains the increasingly heavy nuclear composition in this energy range.

    ↳ astro-ph.HEhep-ph3 citations
22. 22*

    Quantum Effective Dynamics and Stability of Vacuum in Anti-de Sitter Spacetimes

    Shi-Yuan Li🇨🇳 · Chengwu Liu🇨🇳

    We investigate the details of the canonical quantization of effective quantum field theories in anti-de Sitter spacetime, emphasizing the stability of the quantum vacuum. We take the scalar and Maxwell fields as examples. For the non-minimally coupled massless real scalar field with \xi R\phi^2 term in the Lagrangian (mass can be introduced by shift of \xi), only when \xi \le 5/48, the quantized Hamiltonian is spontaneously non-negative and the vacuum is well defined. For \xi > 5/48, one has to assign the negative energy spectrum as that of the ghost particles, introducing anti-commutation relations to make the corresponding part of the Hamiltonian trivial, ensuring the Hamiltonian non-negative and the vacuum (and the Hilbert space) well defined. This method of ghost states is applicable once the proper radial boundary conditions guarantee the Hamiltonian self-adjoint. The resulting dynamics can be compared with those resulting from the positive self-adjoint extensions when the latter is available for \xi\le 9/48. For the Maxwell fields, the gauge invariant canonical energy momentum tensor straightforwardly leads to the gauge invariant non-negative Hamiltonian (well-defined vacuum). Hence the redundant gauge degree of freedom is irrelevant, and the 2-dimensional dynamical degrees of freedom are quantized in a concrete, e.g., temporal gauge. The energy momentum tensors for both quantized fields are renormalized to be finite at operator level, which renders the stable vacuum maximally symmetric. The back-reactions to the background spacetime by excited states via the semi-classical Einstein equations are also discussed.

    ↳ gr-qchep-phhep-th0 citations
23. 23*

    Bayesian Constraints on the Neutron Star Equation of State with a Smooth Hadron-Quark Crossover

    Xavier Grundler🇺🇸 · Bao-An Li🇺🇸

    We perform a Bayesian inference of the dense-matter equation of state (EOS) within a unified framework that incorporates hadronic matter, quark matter, and a smooth hadron-to-quark crossover. The EOS is constrained using physical consistency conditions, gravitational wave data from GW170817, NICER mass versus radius measurements, and hypothetical future high-precision radius observations. In contrast to most previous studies that assume a sharp first-order phase transition or fix part of the EOS, we simultaneously infer hadronic, quark, and crossover parameters within a single statistical framework. We find that current observations strongly constrain the density dependence of the nuclear symmetry energy, particularly its slope and curvature. In contrast, the highest density hadronic parameters and quark-matter properties remain only weakly constrained. We further show that the trace anomaly exhibits a remarkably universal behavior across the accepted EOS ensemble and remains largely insensitive to current observational constraints. This indicates that the present data primarily probe the low to intermediate density EOS. At the same time, robust inference of quark matter and genuinely high-density physics will require next-generation precision radius measurements or complementary observables.

    ↳ nucl-thastro-ph.HEhep-phhep-th+1PRD(2026)·3 citations
24. 24*

    Primordial Black Hole Abundance from Reionization

    Ziwen Yin🇨🇳 · Hanyu Cheng🇨🇳 · Luca Visinelli🇮🇹

    We derive robust constraints on the initial abundance of evaporating primordial black holes (PBHs) using the reionization history of the Universe as a cosmological probe. We focus on PBHs that inject electromagnetic (EM) energy into the intergalactic medium (IGM) after recombination, in the mass range $3.2\times 10^{13}\mathrm{g}\lesssim M_{\mathrm{PBH}}\lesssim 5\times 10^{14}\mathrm{g}$. For each PBH mass, we compute the redshift-dependent energy injection from Hawking evaporation using \texttt{BlackHawk}, fully accounting for the time evolution of the PBH mass and the complete spectrum of emitted Standard Model particles and gravitons. The resulting photons and electrons are propagated through the primordial plasma using \texttt{DarkHistory}, which self-consistently models EM cascades and determines the fraction of injected energy deposited into ionization, excitation, and heating of the IGM. These modifications to the ionization and thermal histories are incorporated into a Gaussian Process reconstruction of the free-electron fraction based on low-$\ell$ CMB polarization data from the \textit{Planck} mission. This non-parametric approach allows for a statistically well-defined separation between exotic high-redshift energy injection and late-time astrophysical reionization, allowing PBH evaporation to be constrained through its contribution to the high-redshift optical depth. Requiring consistency with current CMB measurements, we obtain upper limits on the initial PBH abundance that are robust against reionization modeling uncertainties and systematically more conservative than existing bounds, reflecting the fully numerical and time-dependent treatment of Hawking evaporation and energy deposition. Our results demonstrate the power of reionization observables as a precision probe of PBH evaporation and other scenarios involving late-time energy injection.

    ↳ astro-ph.COhep-ph4 citations
25. 25*

    Proton-Size Resolution of the Hyperfine Puzzle in Hydrogen

    Gerald A. Miller🇺🇸

    Baym and Farrar (arXiv:2601.02300v1) have recently pointed out a puzzle in understanding the role of the hyperfine interaction in the ground state of a hydrogen atom. If one uses a variational wave function in which the Bohr radius, $a_0$ is replaced by a variational radius parameter, $R$, first-order perturbation theory can give a contribution to the energy proportional to $-1/R^3$. This raises the question of why the hyperfine interaction does not lead to collapse of hydrogen. I show that including the effects of the non-zero size of the proton leads to a resolution of the puzzle such that the variational procedure yields a value of $R$ that is indistinguishable from $a_0$.

    ↳ physics.atom-phhep-phnucl-th1 citation
26. 26*

    Gravitational Raman Scattering: a Systematic Toolkit for Tidal Effects in General Relativity

    Mikhail M. Ivanov🇺🇸 · Yue-Zhou Li🇺🇸 · Julio Parra-Martinez🇫🇷 · Zihan Zhou🇺🇸

    We present a framework for systematic computations of scattering amplitudes for gravitational Raman scattering, -- the inelastic scattering of massless fields off compact relativistic objects. We focus on the small-frequency (post-Minkowskian, PM) regime relevant for the study of tidal effects, which can be mapped onto gravitational wave observables during the inspiraling phase of a merger. We demonstrate that this setup is ideal for systematic studies of tidal effects, in a way that is free from coordinate, gauge, and field redefinition ambiguities. We use a combination of worldline effective field theory, the background field method, and advanced scattering amplitude techniques to derive phase shifts for scattering of spin-$0,1,2$ fields off generic compact objects at third PM order. We demonstrate that the inclusion of the recoil of the object is crucial for consistency of this calculation. Focusing on a particular case of black holes, we extract the leading static and dynamical Love numbers of the spin-0 field and the static Love number of the spin-1 field in four dimensions by matching our EFT amplitudes and calculations in General Relativity. We show, fully on-shell, that the leading static Love numbers vanish identically, while the dynamical Love numbers are not zero and run logarithmically. The latter resolves the ambiguities of previous off-shell matching calculations. We also extend our results to seven dimensions, where spin-2 Love numbers undergo a renormalization group running at 2PM, which we compute explicitly. In addition, we extract the leading static Love numbers of spin-0 and spin-1 fields in five dimensions, which also run.

    ↳ hep-thastro-ph.HEgr-qchep-ph21 citations
27. 27*

    Correlations of Feed-down Hadrons in a Thermal Model

    Claude Pruneau🇺🇸 · Victor Gonzalez🇺🇸 · Oveis Sheibani🇺🇸 · Chun Shen🇺🇸 · Yash Patley🇮🇳 · Basanta Nandi🇮🇳 · Ana Marin🇩🇪

    We examine the potential impact of strong decays on the magnitude of fluctuations of net quantum numbers and integrals of balance functions based on a thermal hadron gas model. The calculations are based on a comprehensive list of known hadrons with masses up to 2.5 GeV/$c^2$ and include all decays of these hadrons with known branching fractions. The calculations are performed at vanishing baryo-chemical potential for temperatures between 140 and 200 MeV. We show that the decays feed-down substantially impact the single yield of measurable ``stable particles" as well as those of correlated densities of these species. Decays can then potentially have large and non-trivial impacts on measurements of net quantum number cumulants and balance functions. These observations are particularly important in the context of the search for the QCD critical point at the RHIC Beam Energy Scan as well as efforts to determine chemical susceptibilities near the phase transition at RHIC or LHC energies. Results obtained in this work also shed light on the importance of feed-down in measurements of balance functions in elementary p-p and nucleus-nucleus collisions.

    ↳ nucl-thhep-phnucl-exPRC(2026)·0 citations
28. 28*

    Beyond Wigner: Non-Invertible Symmetries Preserve Probabilities

    Thomas Bartsch🇬🇧 · Yuhan Gai🇬🇧 · Sakura Schafer-Nameki🇬🇧

    In recent years, the traditional notion of symmetry in quantum theory was expanded to so-called generalised or categorical symmetries, which, unlike ordinary group symmetries, may be non-invertible. This appears to be at odds with Wigner's theorem, which requires quantum symmetries to be implemented by (anti)unitary -- and hence invertible -- operators in order to preserve probabilities. We resolve this puzzle for (higher) fusion category symmetries $\mathcal{C}$ by proposing that, instead of acting by unitary operators on a fixed Hilbert space, symmetry defects in $\mathcal{C}$ act as isometries between distinct Hilbert spaces constructed from twisted sectors. As a result, we find that non-invertible symmetries naturally act as trace-preserving quantum channels. Crucially, our construction relies on the symmetry category $\mathcal{C}$ being unitary. We illustrate our proposal through several examples that include Tambara-Yamagami, Fibonacci, and Yang-Lee as well as higher categorical symmetries.

    ↳ quant-phcond-mat.str-elhep-phhep-th+18 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.