Mon·Mar 16, 2026Monday·March 16, 2026

1. 01*

   Elliptic Anisotropy from Quantum Diffraction

   Erik Carrió🇪🇸 · Daniel Pablos🇪🇸

   The surprising manifestation of collectivity in small collision systems, such as nucleon-nucleon and nucleon-nucleus collisions, is perhaps even more striking when discussed at higher momenta. In larger systems, high-$p_T$ elliptic anisotropy is understood as a selection bias effect due to the smaller energy loss experienced along the shorter direction that aligns with the event plane. However, in small systems the amount of energy loss appears insufficient to reproduce the sizable angular anisotropy observed experimentally. In this work, we explore a new mechanism generating preferred orientations for energetic particles without the need of energy loss. We exploit a simple model that is based on two basic although inalienable ingredients: geometry and quantum mechanics. Our findings suggest that this sum-over-paths mechanism can provide a relevant contribution to so-called flow coefficients of energetic particles traversing deconfined media of any size.

   hep-phnucl-thPRD(2026)·5 citations
2. 02*

   Factorization Beyond Coherence

   Thomas Becher🇨🇭 · Patrick Hager🇨🇭 · Matthias Neubert🇺🇸 · Dominik Schwienbacher🇨🇭

   We derive a novel factorization theorem for $N$-jettiness at hadron colliders, which incorporates coherence-violating effects induced by Glauber gluons and several new momentum modes. Their interplay generates coherence-violating logarithms (CVLs) starting at four-loop ($N\ge 1$) or five-loop order ($N=0$). We calculate the anomalous dimensions required for the resummation of CVLs and establish a general framework for the systematic treatment of coherence violation. Our findings imply that most existing factorization formulas for global LHC observables must be revised.

   hep-phhep-th10 citations
3. 03*

   Testing the unitarity of the light neutrino mixing matrix

   E. Gabrielli🇮🇹 · A. Lind🇮🇹 · L. Marzola🇪🇪 · K. Müürsepp🇪🇪 · E. Nardi🇪🇪

   We propose a novel test of the unitarity of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix at collider experiments. Our approach exploits the incomplete cancellation between $t$-channel neutrino exchange and $s$-channel gauge-boson contributions that arises in the presence of violation of the flavor-diagonal PMNS unitarity conditions in weak boson pair production, leading to an anomalous growth of the cross section with energy. Such effects are generic in extensions of the Standard Model in which light neutrinos mix with heavier states, and can manifest at colliders as long as the characteristic energy of the process remains below the mass threshold of the new degrees of freedom. After briefly reviewing these scenarios, we employ our strategy to derive model-independent bounds on flavor diagonal unitarity-violating effects using LEP~II data. We then present sensitivity projections for future lepton and hadron colliders, demonstrating that they are well suited to probe the unitarity of the neutrino mixing matrix with this method.

   hep-phhep-exPRD(2026)·2 citations
4. 04*

   Quarkonium spectra with magnetically induced anisotropic confinement

   Ahmad Jafar Arifi🇯🇵 · Kei Suzuki🇯🇵

   Strong magnetic fields modify the force that confines quarks inside hadrons and make it direction-dependent. Using quark-antiquark potentials obtained from lattice simulations as inputs to a quark potential model, we investigate how the anisotropic confinement affects the mass spectrum of quarkonium. In the strong-field regime, we find downward mass shifts induced by a softening of the confining potential along the field direction. In particular, the mass shifts of radially excited states are more significant than that of the ground state. For the longitudinal spin eigenstates, the excited-state spectrum strongly depends on the magnetic-field strength, in contrast to the spectrum with conventional isotropic confinement, which is insensitive to the field strength. This provides a clean probe of magnetically induced confinement anisotropy that can be confirmed in future lattice simulations.

   hep-phhep-latnucl-thPRD(2026)·1 citation
5. 05*

   Axial-anomaly effects and chiral phase structure in holographic QCD

   Xin-Yi Liu🇨🇳 · Yue-Liang Wu🇨🇳 · Zhen Fang🇨🇳

   We study the impact of axial-anomaly effects on the chiral phase structure in a $U(3)$-extended soft-wall holographic QCD model. Including the pseudoscalar singlet sector allows for a dynamical description of the $\eta$-${\eta }^{\prime }$ system through a determinant interaction with a holographic-coordinate-dependent strength. Vacuum pseudoscalar observables, particularly the ${\eta }^{\prime }$ mass and the $\eta$-${\eta }^{\prime }$ mixing pattern, constrain the overall magnitude of the anomaly contribution but leave its holographic profile largely undetermined. We then examine how different anomaly profiles consistent with vacuum phenomenology affect the finite-temperature chiral transition. Constructing the Columbia plot within this framework, we find that the predicted phase structure depends sensitively on the anomaly implementation: some profiles yield crossover/second-order behavior across the entire quark-mass plane, while others generate a first-order region in the light-quark corner. These results highlight the strong sensitivity of the holographic QCD phase structure to the modeling of axial-anomaly effects.

   hep-ph3 citations
6. 06*

   Possible ${\bar{D}}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ and ${\Xi }_{cc}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ molecules as superflavor partners of $T_{cc}$

   Manato Sakai🇯🇵 · Yasuhiro Yamaguchi🇯🇵

   The doubly charmed tetraquark $T_{cc}$ has been reported by the LHCb experiment in 2022, and a lot of theoretical studies has been conducted. The small binding energy measured from $D^{\ast +}{D}^0$ threshold indicates that $T_{cc}$ is a $D{D}^{\ast }$ molecule. On the other hand, the superflavor symmetry, which relates heavy antiquarks to heavy diquarks, provides a useful framework for predicting the existence of partner exotic hadrons associated with $T_{cc}$. By replacing ${\bar{D}}^{(\ast )}$ with ${\Xi }_{cc}^{(\ast )}$ within this symmetry, ${\bar{D}}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ and ${\Xi }_{cc}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ are expected to form partner structures of $T_{cc}$. In this paper, we investigate bound and resonant states of ${\bar{D}}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ and ${\Xi }_{cc}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ based on the one boson exchange potential, where $\pi$, $\rho$, $\omega$ and $\sigma$ are considered as bosons. The cutoff parameter and the coupling constants for ${\bar{D}}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ and ${\Xi }_{cc}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ are taken to be the same as those for $T_{cc}$ due to superflavor symmetry. We also discuss the $\sigma$ coupling constant, which is uncertain, dependence of these mass spectra. A lot of bound and resonant states with some quantum numbers are obtained for each $\sigma$ coupling constant, but these mass spectra depend on the $\sigma$ coupling constant significantly.

   hep-phPRD(2026)·1 citation
7. 07*

   Purely Baryonic Weak Decays of Heavy Baryons in Skyrme Model

   Chao-Qiang Geng🇨🇳 · Chao Han🇨🇳

   Purely baryonic weak decays of heavy baryons are investigated within the framework of the Skyrme model. These decays belong to a new class of unobserved decay channels, which would help us to test the standard model, particularly potential sources of CP violation in the baryonic sector. By interpreting the heavy baryon as a bound state of a heavy meson and a baryon (Skyrmion), a direct calculation of the decay process ${\Lambda }_b\to p\bar{p}n$ is performed. The resulting branching fraction is of $\mathcal{O}(10^{-6})$, in agreement with previous estimates.

   hep-phPRC(2026)·1 citation
8. 08*

   Quantum entanglement and Bell nonlocality in top-quark pair production at a photon linear collider

   Seong Youl Choi🇰🇷 · Dong Woo Kang🇰🇷 · Jae Sik Lee🇰🇷 · Chan Beom Park🇰🇷

   A photon linear collider, the two-photon collision mode of an $e^{+}{e}^{-}$ linear collider, uses high-energy laser photons backscattered off the incoming electrons and positrons. The colliding-photon polarization is fully controllable through the polarizations of the initial electron and positron beams and laser photons. We investigate the impact of colliding-photon polarization on the observability of quantum entanglement in top-quark pair production at a photon linear collider. Constructing the spin density matrix of the $t\bar{t}$ two-qubit system from the helicity amplitudes, we demonstrate that a photon linear collider is an ideal machine to probe quantum entanglement and Bell nonlocality across the broad phase space of the process.

   hep-phhep-ex7 citations
9. 09*

   Not So Minimal Warm Inflation

   Mar Bastero-Gil🇪🇸 · Pedro García Osorio🇪🇸 · António Torres Manso🇵🇹

   An axion-like inflaton coupled to non-Abelian gauge bosons provides a compelling microphysical framework for warm inflation. Starting even from cold initial conditions, in these systems, sphaleron heating may generate thermal friction sufficient to sustain finite temperatures throughout the inflationary epoch. Insisting on shift-symmetric potentials, in this work we revisit the viability of these scenarios under the designation of Minimal Warm Inflation. We examine both observational constraints and model-building limitations on models with a hierarchy between the decay constants appearing in the friction rate and in the inflaton potential. We conclude that the popular clockwork mechanism cannot generate the required hierarchy; however, partial-wave unitarity bounds admit effective descriptions that remain consistent with observations.

   hep-phastro-ph.COgr-qchep-thJCAP(2026)·3 citations
10. 10*

    Ward identity preserving local ultraviolet counterterms for photoproduction at two loops in QCD

    Charalampos Anastasiou🇨🇭 · Julia Karlen🇨🇭 · Roshni Sahoo🇨🇭 · George Sterman🇺🇸 · Matilde Vicini🇨🇭

    We review the construction of locally finite two-loop amplitude integrands for photoproduction via quark annihilation, presented in arXiv:2509.07805. Building on established techniques for off-shell colorless production, we extend this local subtraction framework to handle transient singularities arising from real outgoing photons. These singularities manifest only at the integrand level, yielding finite contributions upon integration. In these proceedings, we provide the explicit construction of ultraviolet counterterms that satisfy necessary Ward identity cancellations, ensuring that the integrand is rendered integrable. This work provides a locally finite amplitude integrand that is ready for numerical integration in momentum space. Furthermore, it establishes the foundation for extending local subtraction frameworks to processes involving final-state jets.

    hep-ph0 citations
11. 11*

    A basic model for high energy cosmic ray interactions

    Sergey Ostapchenko🇩🇪 · Tanguy Pierog🇩🇪 · Günter Sigl🇩🇪

    A Monte Carlo generator of high energy cosmic ray interactions, relying on a very basic and transparent theoretical formalism, in the framework of the Reggeon Field Theory, is presented. The main motivation for our work is to provide a new cosmic ray interaction model characterized by relatively transparent physics, sufficient parameter freedom, and a high computational efficiency, which can be easily managed by external users, including a re-tuning of the model parameters. Such a model can be used for studying potential modifications of the interaction treatment, necessary for describing particular sets of data on extensive air showers initiated by high energy cosmic rays, at a microscopic level, thereby keeping a consistency with general restrictions, like the unitarity, energy-momentum and charge conservation, Lorentz and isospin invariance. Importantly, this should allow one to study a compatibility of such modifications with relevant accelerator data. The model results for particle production and for basic extensive air shower characteristics are presented and discussed.

    hep-phastro-ph.HEPRD(2026)·3 citations
12. 12*

    Probing the chiral and $U(1)$ axial symmetry restoration via meson susceptibilities in holographic QCD

    Hiwa A. Ahmed🇮🇶 · Danning Li🇨🇳 · Mamiya Kawaguchi🇺🇸 · Mei Huang🇨🇳

    We investigate the restoration patterns of chiral and $U(1)$ axial symmetries at finite temperature using a soft-wall holographic QCD model. The study employs two distinct parameter sets (Case I and Case II), both calibrated to reproduce a pseudocritical temperature $T_{\mathrm{pc}}\sim 155$ MeV and the physical pion mass. The temperature dependence of the light and strange quark condensates confirms a smooth chiral crossover transition, with pseudocritical temperatures of $T_{\mathrm{pc}}=0.157$ GeV and $T_{\mathrm{pc}}=0.154$ GeV for Cases I and II, respectively. The screening masses of chiral partner mesons ($\pi$-$\sigma$ and $\eta$-$a_0$) become degenerate near $T_{\mathrm{pc}}$, providing a clear signature of chiral symmetry restoration. Analysis of the corresponding meson susceptibilities further supports this conclusion. However, the indicator for $U(1)$ axial symmetry restoration, ${\chi }_{\pi }-{\chi }_{a_0}$, vanishes at a temperature $T\sim 0.190$ GeV, which indicates a distinct restoration scale with chiral symmetry restoration scale within the present holographic framework. The temperature-dependent topological susceptibility ${\chi }_{\mathrm{top}}^{1/4}$ is also computed, showing a sharp drop near $T_{\mathrm{pc}}$ and a subsequent slight decrease. While the model qualitatively captures established features of the chiral transition, the results highlight a limitation in the qualitative description of the $U(1)$ axial anomaly compared to LQCD in our work.

    hep-phhep-lathep-thnucl-thPRD(2026)·1 citation
13. 13*

    Active-sterile neutrino mixing in the ISS(p,q) inverse seesaw models

    M.N. Dubinin🇷🇺 · E.Yu. Fedotova🇷🇺 · D.M. Kazarkin🇷🇺

    A class of models with inverse seesaw (ISS) mechanism is considered for arbitrary numbers p and q of new neutral fermions for each generation of leptons. The models containing a candidate particle for the role of warm dark matter are sorted using the inversion technique of an arbitrary block matrix in terms of Schur complement. Studies of the neutrino mass hierarchies and active-sterile neutrino mixing scenarios in the ISS parameter space for the general case of Casas-Ibarra diagonalization make it possible to identify a class of models that satisfy the last strong constraints from NuSTAR, XMM-Newton, and eROSITA experiments for keV-scale sterile neutrino dark matter particles.

    hep-ph0 citations
14. 14*

    The Migdal effect in Semiconductors for the Effective Field Theory of Dark Matter Direct Detection

    Kim V. Berghaus🇺🇸 · Rouven Essig🇺🇸 · Megan H. McDuffie🇺🇸

    The Migdal effect in semiconductors, prompt ionization from a primary nuclear scattering event, can be described across all kinematic regimes using an effective field theory that encodes the complex vibrational and electronic degrees of freedom of the crystal in measurable structure factors. Simultaneously, general dark matter-nucleus interactions can be systematically described using non-relativistic effective field theory operators. We combine these two effective field theory frameworks to calculate the Migdal effect in semiconductors for all ten dimension-six non-relativistic operators. From the effective Hamiltonian, we find that DM-nucleus scattering factorizes from the ionization and vibrational excitation signal as it does in the free-atom case. Using data from EDELWEISS that was taken with a germanium detector, we derive new experimental bounds on each operator and compare these limits to other direct-detection constraints in the literature. We find the accessible parameter space to be disfavored by bounds on heavy mediators contained in simple UV completions that generate the effective operators.

    hep-phastro-ph.COhep-ex7 citations
15. 15*

    CP Violation in $B_{(s)}\to \varphi K$ Decays: Standard Model Benchmarks and Isospin-Breaking New Physics

    Robert Fleischer🇳🇱 · Jelle Groot🇳🇱 · K. Keri Vos🇳🇱

    The penguin loop-suppressed $B\to \varphi K$ decays are highly sensitive to contributions of hypothetical heavy new particles. Particularly interesting probes for testing the Standard Model and revealing such phenomena are provided by CP violation in the $B_d^0\to \varphi K_{\mathrm{S}}$ decay. Standard-Model estimates for the corresponding CP-violating observables are theoretically limited by doubly Cabibbo-suppressed penguin contributions. We study these effects using a factorization approach, and provide predictions for CP asymmetries, to be contrasted with future measurements. To gain additional insight into these hadronic effects, we propose the $B_s^0\to \varphi K_{\mathrm{S}}$ decay as a new channel. We predict the observables for this decay for which currently no measurements exist. By comparing $B_d^0\to \varphi K_{\mathrm{S}}$ and $B^{+}\to \varphi K^{+}$, we further derive state-of-the-art constraints on isospin observables within the Standard Model. The same framework enables probing of possible New-Physics contributions, including general effects and those with non-trivial isospin structure. Interesting prospects arise for the high-precision era of flavour physics ahead.

    hep-ph1 citation
16. 16*

    Determination of Nuclear PDFs using Markov Chain Monte Carlo Methods

    N. Derakhshanian🇵🇱 · P. Risse🇺🇸 · T. Jezo🇩🇪 · M. Klasen🇩🇪 · K. Kovarik🇩🇪 · A. Kusina🇵🇱

    Global QCD analyses of nuclear parton distribution functions (nPDFs) have traditionally relied on the Hessian method for uncertainty estimation. However, the inherent Gaussian approximation and reliance on local curvature often prove insufficient for nPDF fits, which are frequently characterized by limited data constraints and non-Gaussian likelihoods. In this paper, we present the first nPDF determination based on Markov Chain Monte Carlo (MCMC) techniques, implemented within the nCTEQ framework using an adaptive Metropolis-Hastings algorithm. The MCMC approach enables a direct mapping of the posterior distribution and reveals a highly non-trivial parameter-space structure, including multiple modes and pronounced non-Gaussian behavior, particularly for the valence PDFs. We perform the first single-nucleus global analysis of lead PDFs using exclusively lead data and compare it to a multi-nuclei fit employing a standard analytic A dependence. The inclusion of lighter nuclei reduces quark uncertainties and modifies the shape of the lead PDFs, while leaving the gluon distribution largely unaffected. A complementary Hessian analysis exposes systematic limitations of the Gaussian approximation. Our results demonstrate that MCMC methods provide a more reliable framework for uncertainty quantification in nPDF determinations.

    hep-phPRD(2026)·3 citations
17. 17*

    Radiative return meets GVMD

    Pau Petit Rosàs🇬🇧 · Olga Shekhovtsova🇺🇦 · William J. Torres Bobadilla🇬🇧

    We improve the description of pion-photon interactions in the radiative return process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma$ at the next-to-leading order by including the pion form factor in the Feynman rules. We present a general calculation of the new amplitudes, and provide an implementation easy to interface with any Monte Carlo generator. We incorporate this framework into the event generator $\text{Phokhara}$ and study several experimental configurations. Overall, we find percent-level effects appearing in angular differential cross section distributions at colliders whose centre-of-mass energies lie near the peak of the pion form factor. By contrast, total cross sections and distributions in charge-even variables show effects only at the permille level, or no visible differences at all. Finally, we compare the new predictions with KLOE measurements of the forward-backward asymmetry in order to assess the predictive power of the modifications.

    hep-phhep-thPLB(2026)·7 citations
18. 18*

    Axion search with telescope for radio astronomy (ASTRA): forecast for observations between 0.5 and 4~GHz

    Utkarsh Bhura🇬🇧 · David J. E. Marsh🇬🇧 · Bradley R. Johnson🇺🇸 · Karl van Bibber🇺🇸 · Mallory Helfenbein🇺🇸 · Bradley J. Kavanagh🇪🇸 · Matthew Nelson🇺🇸 · Ciaran A. J. O'Hare · Giovanni Pierobon🇦🇺 · Gray Rybka🇺🇸 · Luca Visinelli🇮🇹

    Axion dark matter (DM) is predicted to convert into radio waves in neutron star magnetospheres. We assess the detectability of this signal using a 5 m radio telescope to be installed at the Fan Mountain Observatory, operating in the UHF, L- and S-bands from 0.5 to 4~GHz. We demonstrate that such a telescope can search new parameter space for axion-like particles over a broad range from $2\mu \text{eV}<m_a<17\mu \text{eV}$ for axion-photon couplings $g_{a\gamma \gamma }\gtrsim 2\times 10^{-12}{\text{ GeV}}^{-1}$ with a three year observing period assuming the standard halo model -- improving neutron star observations by more than an order of magnitude. The search is broadband and is thus complementary to other techniques in the same frequency range. We describe in detail our neutron star population model, noise model, and proposed observing strategy. Most constraining power comes from neutron stars at the Galactic centre, where the smooth DM halo is densest. If a DM spike exists at the Galactic centre, the search is sensitive in the QCD axion model band. UHF and L-band observations (0.5 to 2~GHz) represent the pathfinder phase of a wider program we call ``Axion Search with Telescope for Radio Astronomy'' (ASTRA). Future higher mass searches aimed at discovery potential for the post-inflation axion require further hardware development to cover S, C, X and Ku bands (2 to 18~GHz).

    hep-phastro-ph.COastro-ph.GAhep-ex4 citations
19. 19*

    Ultralight Dark Matter: Undergraduate Physics in Modern Cosmology

    Timothy D. Wiser🇺🇸

    Ultralight dark matter is a hypothetical class of particle with a number of interesting theoretical and experimental properties, many of which are best understood by direct analogy with or application of undergraduate physics. We present a series of exercises and discussions which may inspire the reader to bring contemporary research on ultralight dark matter into the undergraduate classroom.

    hep-phastro-ph.COphysics.ed-ph0 citations
20. 20*

    Strangeness neutrality and the QCD phase diagram

    Wei-jie Fu🇨🇳 · Chuang Huang🇩🇪 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇩🇪 · Rui Wen🇨🇳 · Shi Yin🇩🇪

    We map out the phase structure of $N_f=2+1$ flavour QCD at strangeness neutrality with functional QCD. We find a critical end point at $(T_{\mathrm{CEP}},{\mu }_{B,\mathrm{CEP}}){|}_{n_S=0}=(92,696)$\,MeV. The computation is done with the functional renormalisation group, and we systematically improve on previous works, hence reducing the systematic error significantly. Our results pass relevant QCD benchmarks: they agree well with and corroborate the QCD phase structure from functional QCD results at vanishing strangeness chemical potential. Moreover, they agree well with lattice QCD results at vanishing chemical potential. Specifically, the ratio of the second order curvature coefficient ${\kappa }_2$ agrees with that obtained from lattice computations, ${\kappa }_2(n_S=0)/{\kappa }_2({\mu }_S=0)=0.897(20)$.

    hep-phhep-exnucl-exnucl-th14 citations
21. 21*

    Blazar Constraints on Axions through New Spectral Modulation Searches in 1ES 1959+650 & B2 1811+31

    Andrea Giovanni De Marchi🇮🇹 · Orion Ning🇺🇸 · Tianzhuo Xiao🇺🇸

    Blazars are unique astrophysical environments whose high-energy $\gamma$-ray spectra are susceptible to modulations in the presence of ultralight axions. We search for these modulations, induced by axion-photon mixing, in Fermi-LAT spectral data of previously unexplored blazar targets, focusing in particular on blazars 1ES 1959+650 and B2 1811+31, whose flare states provide a clean testbed for axion activity. In both cases, we find no evidence for axions, and set exclusion regions on the axion-photon coupling for masses between $10^{-9}$ eV $\lesssim$ $m_a$ $\lesssim$ $10^{-8}$ eV, with sensitivities typically reaching $g_{a\gamma \gamma }\sim 10^{-11}-10^{-10}$ GeV${}^{-1}$ depending on the assumed blazar modeling choices. We examine the broad impact of modeling uncertainties, finding that the resulting constraints can vary substantially across plausible configurations. We discuss the implications of these systematic effects and their relevance for similar blazar-like searches in the future.

    hep-phastro-ph.HE1 citation
22. 22*

    Reheating with Axion-SU(2) and Gravitational Chern-Simons Couplings

    Tatsuya Daniel🇨🇦 · Vahid Kamali🇨🇦

    We study the early stages of an oscillatory reheating phase in an inflaton plus spectator axion-SU(2) system, including both an axion-gauge Chern-Simons coupling $\chi F\tilde{F}$ and a gravitational Chern-Simons coupling $\chi R\tilde{R}$. Assuming an isotropic SU(2) background configuration of chromo-natural type and quadratic potentials, we numerically solve the coupled background and tensor perturbation equations during the first e-fold of reheating. The gravitational Chern-Simons term induces a helicity-dependent modification of the tensor kinetic coefficient, yielding a chiral enhancement of the tensor power spectrum on the order of tens of percent for a representative benchmark. We illustrate how such an early-time enhancement can map to a narrow feature in the present-day stochastic gravitational wave spectrum, potentially relevant for upcoming and proposed space-based detectors, while a fully self-consistent determination of the peak scale requires scanning comoving wavenumbers and specifying the reheating history.

    ↳ astro-ph.COgr-qchep-phhep-th0 citations
23. 23*

    Robustness of Neural Networks for CMB Polarization Foreground Removal

    Luca Gomez Bachar · Cora Dvorkin🇺🇸 · Alberto Daniel Supanitsky🇦🇷

    The detection of Cosmic Microwave Background primordial $B$-mode polarization would constitute a ``smoking gun" signal of primordial gravitational waves. However, this measurement requires accurate removal of polarized Galactic foregrounds to avoid systematic biases when estimating the tensor-to-scalar ratio. Methods based on Machine Learning techniques (ML), such as Convolutional Neural Networks (CNNs), have recently been proposed as alternative foreground cleaning techniques, but their applicability to real data relies on their ability to generalize beyond the models assumed during training. In this work, we focus on a variety of foreground models (FMs) used for training and conduct a systematic study of the generalization properties of a CNN-based method. We train various CNN architectures on simulations generated from different Galactic FMs, and test their performance on models not used during the training. By characterizing the statistical properties of the FMs using variance, skewness, and Shannon entropy, we define a statistical complexity hierarchy among them. We show that training on the more complex FMs reduces bias and improves precision when testing on unseen FMs, whereas training on the simplest model could introduce systematic errors. These results evidence that a lack of generalization is a relevant source of systematic uncertainty, and emphasize the importance of understanding the impact of the models assumed during training in ML-based methods before applying them to real data.

    ↳ astro-ph.COastro-ph.IMhep-ph0 citations
24. 24*

    Binding energy of the $T_{bb}$ tetraquark from lattice QCD with relativistic and nonrelativistic heavy-quark actions

    Jakob Hoffmann🇩🇪 · Stefan Meinel🇺🇸

    We present a new determination of the $\bar{b}\bar{b}ud$ ($J^P=1^{+}$, $I=0$) tetraquark binding energy using lattice QCD with domain-wall light quarks and a nonperturbatively tuned three-parameter anisotropic-clover ``relativistic'' action for the $b$ quarks. We also perform a direct comparison with a reanalysis of data generated in prior work using a lattice-NRQCD action for the $b$ quarks and otherwise identical parameters. Using the new data with relativistic $b$ quarks from seven different ensembles with multiple lattice spacings and pion masses, we perform combined chiral and continuum extrapolations and obtain $(m_{T_{bb}}-m_B-m_{B^{\ast }}{)}_{\mathrm{RHQ}}=(-76\pm 23)$ MeV. For the NRQCD data from five ensembles, we perform chiral-only extrapolations and obtain $(m_{T_{bb}}-m_B-m_{B^{\ast }}{)}_{\mathrm{NRQCD}}=(-74\pm 17\pm 10)$ MeV. The lower magnitude of the results obtained here, compared to the original analysis in Phys. Rev. D 100, 014503 (2019), is due to the use of the symmetric parts of the correlation matrices with local four-quark operators only.

    ↳ hep-lathep-phnucl-thPRD(2026)·0 citations
25. 25*

    Sound Speed Resonance in the Gravitational Wave Background as a probe for non-standard early universe cosmologies

    Igor de O. C. Pedreira🇨🇳 · Amara Ilyas🇨🇳 · Ziwei Wang🇨🇳 · Leila L. Graef🇧🇷 · Yi-Fu Cai🇨🇳

    Gravitational waves constitute a powerful probe of the underlying theory of gravity. In extensions of general relativity, additional degrees of freedom, such as scalar fields in the gravitational sector, can modify their propagation through changes in the effective friction term and propagation speed. These modifications may potentially induce resonant phenomena leading to distinctive signatures in the gravitational wave spectrum. One important aspect to be investigated is whether the resonances can be strong enough to enhance the underlying background of primordial tensor modes to levels detectable by upcoming gravitational wave detectors, such as LISA or the Einstein telescope. The characteristic peaks in the SBGW spectrum depend on the parameters of the resonant model as well as on the parameters of the primordial tensor spectrum, such as $r$ and $n_t$. Thus these resonance effects open a powerful pathway to explore physics of the very early Universe by amplifying otherwise feeble signals to experimentally detectable levels. Here we analyze how the signals of the primordial Universe can resonate in these scenarios, bringing the early universe physics into the realm of experimental access.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2026)·0 citations
26. 26*

    Shaving off soft hairs and the black hole image memory effect

    Shaoqi Hou🇨🇳 · Zong-Hong Zhu🇨🇳

    Soft hairs of black holes are the Noether charges associated with the generalized Bondi-Metzner-Sachs symmetries. In this work, the images of soft-haired Kerr black holes are studied. For an eternal black hole, the image is rotated, dilated, and drifting compared to that of the bald counterpart in the celestial plane. The rotation and the dilation are independent of time, while the drifting occurs at a constant speed and in a fixed direction. These effects all depend on angular directions. The soft hair of an astronomical black hole can change due to the emission of gravitational or electromagnetic waves from various physical processes occurring in the vicinity of the horizon. Then, the image roams in the observer's view, causing the image memory effect, the smoking gun for the existence of soft hair. The magnitude of the image memory effect of a huge, spinning black hole accompanied by a much smaller one is estimated. It turns out that this effect is proportional to the mass of the large black hole, increases with its spin, but decreases with the mass ratio. Due to the limited angular resolution of current and future detectors, this effect is hard to detect if the impact of cosmological expansion is ignored.

    ↳ gr-qchep-phhep-thPRD(2026)·0 citations
27. 27*

    Thermodynamics and null-geodesic of the Kerr-Newman black hole surrounded by quintessence and a cloud of string

    Aheibam Boycha Meitei🇮🇳 · Yenshembam Priyobarta Singh🇮🇳 · Telem Ibungochouba Singh🇮🇳 · Irom Ablu Meitei🇮🇳 · Kangujam Yugindro Singh🇮🇳

    In this paper, we study the effect of the modified dispersion relation (MDR) on the thermodynamics of the Kerr-Newman black hole surrounded by quintessence and a cloud of string. The thermodynamic properties of the Kerr-Newman black hole are shown to rely not only on the black hole's properties but also on the parameters associated with the modified dispersion relation, quintessence, and the cloud string. Additionally, the equation of state is impacted by these parameters. The remnant and the stability of the black hole are also discussed under the correction of MDR, quintessence, and a cloud of string. In addition, the null geodesic structure of the spacetime is studied using the Hamilton--Jacobi formalism. The effective potential for photon motion is obtained, and the radii of the prograde and retrograde circular photon orbits are determined. The instability of these circular photon orbits is further characterized by the Lyapunov exponent.

    ↳ gr-qchep-phEur.Phys.J.Plus(2026)·0 citations
28. 28*

    Kerr-Newman black hole surrounded by quintessence under quantum gravity effects and gravity's rainbow

    Aheibam Boycha Meitei🇮🇳 · Irom Ablu Meitei🇮🇳 · Telem Ibungochouba Singh🇮🇳 · Kangujam Yugindro Singh🇮🇳

    In this paper, we investigate the quantum gravity effects on the tunneling of particles and gravity's rainbow across the event horizon of Kerr-Newman black hole (KNBH) surrounded by the quintessence. The aspect of quantum gravity has been introduced by applying the Generalized Uncertainty Principle (GUP) to the Klein-Gordon equation and the Dirac equation of scalar and fermion particles. By solving the Generalized Klein-Gordon and Dirac equations obeyed by scalar and fermion particles, corrections to the Hawking temperature of the KNBH in the presence of quintessence is discussed. The tunneling of fermions is also examined using the modified Hamilton-Jacobi equation also known as modified Rarita-Schwinger equation, and the corrected Hawking temperature is determined. The corrected Hawking temperature of the KNBH surrounded by quintessence is found to be dependent not only on the properties of the black hole but also on the quantum numbers of the emitted particles and quintessence. Then, we explored the KNBH surrounded by quintessence within the framework of gravity rainbow using rainbow functions. In the context of rainbow functions in loop quantum gravity, we derive the Hawking temperature, heat capacity, equation of state parameters, and entropy for the KNBH surrounded by quintessence. It is found that these quantities are influenced by both the quintessence and the rainbow gravity.

    ↳ gr-qchep-ph0 citations
29. 29*

    Weak and Higgs physics from the lattice

    Sofie Martins🇩🇰 · Patrick Jenny🇦🇹 · Axel Maas🇦🇹 · Georg Wieland🇦🇹

    The manifestly gauge-invariant and non-perturbatively complete lattice formulation of the weak interactions and the Brout-Englert-Higgs effect is connected to the usual perturbative description in phenomenology via the Fröhlich-Morchio-Strocchi mechanism. However, slight differences between the two have been observed, which can potentially be accounted for by augmenting perturbation theory. We report on our ongoing lattice investigations of these additional effects using a setup with two generations of leptons coupled vectorially to the gauge-Higgs system. We explore the spectrum, inner structure in terms of weak (quasi-)PDFs, and spectral functions of the system to eventually compare cross sections to experimental results.

    ↳ hep-lathep-phPoS(2026)·2 citations
30. 30*

    Dispersive analysis of the ${\pi }^{+}{\pi }^{-}$ production at the CMD3 experiment and the compatibility with muon pair production measurement by KLOE2 and the pion form factor by JLAB

    Dimitrios Petrellis🇨🇿 · Vladimir Sauli🇨🇿

    The spectral function of the charged pion form factor was extracted from two data sets. The difference between the two sets is based on the presence or absence of the recent measurement of the ${\pi }^{+}{\pi }^{-}$ production by CMD-3 . Although the CMD-3 data are largely incompatible with other recent measurements, no excess was found when the data were used for analytical continuation to the spacelike region and compared to JLaB-$\pi$ experiment. Instead, both data sets provide a spacelike form factor that differs from the expected behavior known from perturbative analyses of quantum chromodynamics (QCD). A precise fit of the spectral functions is provided, either based on he bare form factor and the full $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ as well . Furthermore, the extracted pionic spectral functions were used to obtain the QED running charge. This was then compared with the KLOE-2 measurements.

    ↳ hep-exhep-ph0 citations
31. 31*

    MAXI J1820+070: A rapidly spinning black hole with mild disk truncation in the soft state and a warm corona

    Th. V. Papavasileiou · T. S. Kosmas🇬🇷 · O. Kosmas · I. Sinatkas

    Our study seeks to address the debate over the spin of MAXI J1820+070 through broadband spectral modeling of NuSTAR observations obtained during the soft state. We further compare our results with previous spin estimates and examine the source variability across the soft state. In addition, we investigate the origin of the soft X-ray excess, which we argue does not originate from the plunge region as previously suggested. To further investigate the origin of this excess, we calculate spin-dependent radial disk temperature profiles across all epochs. Our results indicate that the black hole in MAXI J1820+070 is rapidly spinning, with spin $a$ > 0.75, potentially powering the relativistic jets. Our analysis reveals a significant decline in the inner disk temperature midway through the soft state, accompanied by a modest increase in the inferred inner disk radius up to 3.5Rg. This behavior is consistent with slight disk truncation, possibly associated with a reduction in gas ionization and nonthermal processes. Furthermore, the soft excess emission below 10 keV is well described by a blackbody component with kT=0.5 keV, approximately 38% cooler than the inner disk. This suggests that the emission may originate from a warm corona layer located beyond 10Rg, analogous to warm Comptonization models proposed to explain the soft X-ray excess in active galactic nuclei.

    ↳ astro-ph.HEhep-ph0 citations
32. 32*

    Three-band dark-siren cosmology with intermediate mass black hole binaries: Synergy of Taiji, LGWA, and the Einstein Telescope

    Ji-Yu Song🇺🇸 · Yue-Yan Dong🇺🇸 · Shang-Jie Jin🇺🇸 · Si-Ren Xiao🇺🇸 · Jing-Fei Zhang🇺🇸 · Xin Zhang🇺🇸

    Gravitational-wave (GW) dark sirens provide an independent probe of the cosmic expansion history. Their cosmological constraining power, however, depends critically on precise luminosity-distance measurements and sky localizations for cross-matching with galaxy catalogs. Multiband GW observations can track GW events across different frequency bands and thus improve both. Motivated by this, we forecast the cosmological potential of intermediate-mass black hole binaries (IMBHBs) observed by a three-band GW detector network composed of Taiji (TJ), the Lunar Gravitational-wave Antenna (LGWA), and the Einstein Telescope (ET). We simulate detectable IMBHB populations and analyze them with a hierarchical Bayesian dark-siren framework that includes galaxy-catalog completeness and redshift uncertainties. We find that the TJ-LGWA-ET network outperforms all two-detector configurations considered here. In the $\Lambda$CDM model, it constrains the Hubble constant and matter density to $\sim 0.12\%$ and $\sim 0.6\%$, respectively. In the $w$CDM model, a 4-year dark-siren sample alone constrains the dark-energy equation-of-state parameter $w$ to $\sim 2.7\%$. Adding baryon acoustic oscillation (BAO) and Type Ia supernova (SNe Ia) data improves the $w$ constraint to $\sim 2.1\%$, slightly better than that from the current CMB+BAO+SNe Ia combination. We also show that the final constraints remain sensitive to IMBHB population assumptions and galaxy-catalog limitations, which highlights the need for deep galaxy surveys with precise redshift measurements.

    ↳ astro-ph.COgr-qchep-ph8 citations
33. 33*

    Challenging the Weak Cosmic Censorship with Phantom Fields

    Giovanni Caridi🇮🇹 · Fabrizio Corelli🇩🇪 · Paolo Pani🇮🇹

    Penrose's weak cosmic censorship conjecture asserts that spacetime singularities produced by gravitational collapse are generically hidden behind event horizons, thus preventing them from causally influencing distant observers and preserving the predictability of the exterior region. In this work, we probe this conjecture in a setup that deliberately violates one of its central assumptions - the dominant energy condition - by considering the spherical collapse of a phantom scalar field with negative energy density. In principle, such a field could produce a Schwarzschild geometry with negative mass and therefore no event horizon. Our aim is to assess whether, once the dominant energy condition is abandoned, the fully coupled evolution of matter and geometry can dynamically generate or expose naked singularities, thereby probing the robustness of cosmic censorship. To this end, we perform high-accuracy numerical relativity simulations based on fourth-order finite-difference schemes. Starting from smooth, asymptotically flat initial data representing regular phantom scalar wave packets, we follow their fully nonlinear evolution through collapse or dispersion. While an ordinary (positive-energy) scalar field exhibits the standard Choptuik critical behavior at the threshold of black-hole formation, the phantom field displays qualitatively different dynamics. For all amplitudes considered, we find no evidence for trapped surfaces, naked singularities, or alternative stationary end states. Instead, the phantom scalar field always disperses, suggesting that cosmic censorship remains dynamically preserved even in the presence of negative-energy matter.

    ↳ gr-qcastro-ph.HEhep-phhep-th0 citations
34. 34*

    A 2% determination of $N_{\mathrm{eff}}$ from primordial element abundance, cosmic microwave background, and baryon acoustic oscillation measurements

    Samuel Goldstein🇺🇸 · J. Colin Hill🇺🇸

    We present a new constraint on the effective number of relativistic species in the early universe, $N_{\mathrm{eff}}$, by combining recent primordial helium abundance measurements from the Large Binocular Telescope $Y_p$ Project with primordial deuterium abundance data, cosmic microwave background (CMB) observations from $Planck$, the Atacama Cosmology Telescope, and the South Pole Telescope, and baryon acoustic oscillation (BAO) data from the Dark Energy Spectroscopic Instrument, yielding $N_{\mathrm{eff}}=2.990\pm 0.070$ (68% C.L.). This is the tightest constraint on $N_{\mathrm{eff}}$ to date, and is in excellent agreement with the standard model prediction of $N_{\mathrm{eff}}=3.044$. Furthermore, we constrain excess contributions to $N_{\mathrm{eff}}$ beyond the three neutrino species, finding $\Delta N_{\mathrm{eff}}<0.107$ (95% C.L.). This bound nearly approaches the minimum contribution to $\Delta N_{\mathrm{eff}}$ from a light spin-3/2 particle that decoupled at any time after inflation ended. Our baseline analysis does not include large-scale $Planck$ polarization information, enabling a fully consistent combination of state-of-the-art CMB and BAO measurements. As a byproduct, we show that current $N_{\mathrm{eff}}$ bounds are essentially insensitive to the inclusion or exclusion of optical depth constraints inferred from large-scale CMB polarization data, making $N_{\mathrm{eff}}$ highly robust in this regard. Our constraints place stringent limits on light particles in the early Universe and on a broad range of models aimed at increasing the CMB-inferred value of the Hubble constant.

    ↳ astro-ph.COhep-phPRD(2026)·15 citations
35. 35*

    Critical slowing down and bulk viscosity in binary neutron star mergers

    Jamie M. Karthein🇺🇸 · Maneesha Sushama Pradeep🇮🇳 · Rachel Steinhorst🇺🇸

    Hydrodynamic simulations of neutron star mergers rely on the clear separation between the strong-interaction, weak-interaction, and hydrodynamic timescales. In this effective framework, weak Urca interactions are typically the slowest microscopic processes, and therefore the Urca rate determines the bulk-viscous dissipation. This assumed hierarchy of dissipative mechanisms can be decisively altered, without invalidating hydrodynamics, if the trajectory of the matter in a neutron star merger passes through the vicinity of a possible low temperature QCD critical point. The enhanced density fluctuations lead to critical slowing down and rapid growth of transport coefficients including bulk viscosity. While this growth is regulated by finite-time effects, finite-size effects, and the breakdown of hydrodynamic scale separation, which bound the correlation length, we demonstrate that the QCD contribution to bulk viscosity can rival the electroweak contribution in realistic conditions. Thus, critical dynamics could leave observable imprints on the hydrodynamic evolution of neutron star mergers.

    ↳ astro-ph.HEhep-phnucl-th2 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.