Thu·Mar 19, 2026Thursday·March 19, 2026

1. 01*

   Opening up baryon-number-violating operators

   Julian Heeck🇺🇸 · Diana Sokhashvili🇺🇸 · Anil Thapa🇺🇸

   Baryon number violation is our most sensitive probe of physics beyond the Standard Model. Its realization through heavy new particles can be conveniently encoded in higher-dimensional operators that allow for model-agnostic analyses. The unparalleled sensitivity of nuclear decays to baryon number violation makes it possible to probe effective operators of very high mass dimension, far beyond the commonly discussed dimension-six operators. To facilitate studies of this ginormous and scarcely explored testable operator landscape we provide the exhaustive set of tree-level UV completions consisting of scalars, fermions, and vectors for non-derivative baryon-number-violating operators in this Standard Model effective field theory up to mass dimension 15, which corresponds roughly to the border of sensitivity. In addition to the known Standard Model fields we also include right-handed neutrinos in our operators. Our public code can be used to UV-complete any non-derivative operator and match it onto an operator basis.

   hep-ph6 citations
2. 02*

   SMEFT operators in rare multi-top processes

   A. Aleshko🇷🇺 · E .Boos🇷🇺 · V. Bunichev🇷🇺 · L. Dudko🇷🇺

   Nowadays, the Standard Model Effective Field Theory (SMEFT) provides a standard framework to parameterize potential deviations from the Standard Model and to combine information from multiple processes in global analyses. This review summarizes dedicated studies that constrain dimension-six Wilson coefficients using three top-quark and four top-quark production processes. We highlight the complementarity of these channels, as well as summarize the main problems and prospects in the area. A concise introduction to the SMEFT formalism and a discussion of the problem of potential perturbative unitarity violation are also provided.

   hep-ph0 citations
3. 03*

   Multi-Component Dark Matter as a Solution to the Galactic Center GeV Excess

   Farinaldo S. Queiroz🇧🇷 · Clarissa Siqueira🇧🇷 · Carlos E. Yaguna🇨🇴

   The Galactic Center Excess (GCE) is a compelling signature of dark matter annihilation, but its spectral morphology is difficult to reconcile with the traditional paradigm of a single particle species. In this work, we perform a systematic investigation of multi-component dark matter sectors, exploring scenarios with two ($N=2$) and three ($N=3$) distinct particle species while considering both exclusive and mixed annihilation channels. Using the Akaike Information Criterion (AIC) to rigorously penalize model complexity, we find that the GCE data statistically favors an $N=2$ scenario where each dark matter component annihilates exclusively into a single final state. Our results reveal that the preferred solutions naturally follow a light-plus-heavy mass hierarchy, and that specific final states such as $t\bar{t}$, $ZZ$, and $hh$, which are individually unable to explain the excess are effectively ``resurrected'' by the improved morphological fit provided by the multi-component framework. Furthermore, we show that these scenarios may mitigate the tension with current constraints, reaching compatibility within existing uncertainties. Our results suggest that the GCE may be the first evidence of a diverse dark sector, favoring a multi-scale solution over the minimal WIMP paradigm.

   hep-phastro-ph.COastro-ph.HEhep-th1 citation
4. 04*

   Hadronic Lorentz violation in chiral perturbation theory

   Matthias R. Schindler🇺🇸

   Lorentz violation in hadronic systems is related to Lorentz-violating operators of quarks and gluons. Due to the nonperturbative nature of quantum chromodynamics (QCD) at low energies, establishing these relationships is complex. Chiral perturbation theory (ChPT) is an effective theory that provides one method of connecting quark- and gluon-level operators to those at the hadronic level, which can be used to calculate hadronic observables.

   hep-ph0 citations
5. 05*

   Impact of New Physics on the JUNO-Long-Baseline Synergy in Neutrino Mass Ordering Determination

   Gustavo F. S. Alves🇧🇷 · Hiroshi Nunokawa🇧🇷 · Renata Zukanovich Funchal🇧🇷

   The determination of the neutrino mass ordering is one of the flagship goals in particle physics. A well-known and powerful synergy emerges when combining high-precision measurements of the effective atmospheric mass-squared splitting from electron antineutrino disappearance in reactor experiments with that from muon (anti)neutrino disappearance in accelerator-based long-baseline experiments. To fully exploit this synergy, percent-level precision in the atmospheric mass splitting is required-a target that JUNO is expected to achieve within a few months of data taking. This motivated the formulation of a mass ordering sum rule for neutrino disappearance channels, which shows that by combining data from T2K and NOvA with JUNO after one year of operation, the neutrino mass ordering can be determined at the $3\sigma$ confidence level. Since JUNO has recently started taking data, it is timely to ask whether this sum rule remains robust in the presence of new physics. We identify the necessary conditions for new physics to affect the sum rule and demonstrate that, in some cases, such effects could lead to an incorrect inference of the mass ordering. As concrete examples, we consider Scalar Non-Standard Interactions (SNSI) and neutrinos coupled to an ultralight scalar field. We find that, for SNSI, current constraints render any modification of the sum rule negligible, whereas in the latter case, the inference of the ordering requires caution. Nevertheless, these effects can be disentangled, illustrating how the sum rule can also be used to search for new physics.

   hep-phPRD(2026)·4 citations
6. 06*

   Ultralight Scalar Dark Matter with Off-Diagonal Flavor Couplings

   Jinhui Guo🇨🇳 · Jia Liu🇨🇳 · Chenhao Peng🇨🇳 · Xiao-Ping Wang🇨🇳 · Hang Zhao🇨🇳

   Ultralight dark matter can behave as a coherent background field and induce time-dependent modifications of Standard Model parameters. We study a scenario in which a real ultralight scalar $\varphi$ couples off-diagonally to down-type quarks, linking ultralight dark sectors to flavor physics. Working within an effective field theory, we diagonalize the quark mass matrix in a coherent $\varphi$ background and derive analytic expressions for oscillatory shifts in down-type quark masses and CKM parameters. These effects lead to signatures in both the classical regime, where $\varphi$ acts as a background field, and the quantum (particle) regime, where it contributes through on-shell production or off-shell mediation. Using precision flavor measurements, nuclear $\beta$ decays, atomic clocks, pulsar timing, and meson observables, we derive constraints on the flavor-violating couplings ${\lambda }_{ij}$ for $m_{\varphi }\sim 10^{-24}$--$10^{-12}\mathrm{eV}$, highlighting the complementarity of time-domain and flavor probes of ultralight dark sectors.

   hep-phPRD(2026)·1 citation
7. 07*

   Lepton flavor violating ${\tau }^{-}\to {\ell }_i^{-}{\ell }_i^{-}{\ell }_j^{+}$ (${\ell }_i\ne {\ell }_j$) decays induced by $S_1$ and $R_2$ scalar leptoquarks

   G. Hernández-Tomé🇲🇽 · J. P. Hoyos-Daza · O. G. Miranda🇲🇽 · R. Sánchez-Vélez🇲🇽

   Charged lepton flavor violation provides a clear experimental signature in the search for physics beyond the Standard Model. In this work, we study the flavor-violating three-body tau decays ${\tau }^{-}\to {\ell }_i^{-}{\ell }_i^{-}{\ell }_j^{+}$ (${\ell }_i\ne {\ell }_j$) induced by the scalar leptoquarks $R_2$ and $S_1$, focusing on flavor structures dominated by top- or charm-quark contributions. We compute the one-loop contributions to these processes and derive analytical expressions for the corresponding branching ratios. The phenomenological implications are analyzed for leptoquark masses at the TeV scale, taking into account current constraints from the anomalous magnetic moment of the muon, radiative lepton-flavor-violating decays, and the process ${\mu }^{-}\to e^{-}{e}^{-}{e}^{+}$. Within the allowed parameter space, the predicted branching ratios for ${\tau }^{-}\to {\ell }_i^{-}{\ell }_i^{-}{\ell }_j^{+}$ can approach the sensitivities expected in near-future experiments. These results highlight the potential of three-body $\tau$ decays as probes of lepton-flavor violation and as complementary tests of scalar leptoquark scenarios.

   hep-ph0 citations
8. 08*

   Exploring the $t\bar{t}$ threshold at an electron-positron collider

   Leyan Li🇨🇳 · Yuming Lin🇨🇳 · Xiaohu Sun🇨🇳 · Yajun Mao🇨🇳 · Zhan Li🇨🇳 · Kaili Zhang🇨🇳 · Shudong Wang🇨🇳 · Gang Li🇨🇳 · Hongbo Liao🇨🇳 · Yaquan Fang🇨🇳

   Future electron-positron colliders offer a unique opportunity for high-precision measurements of the top-quark mass, width, strong coupling constant, and top-quark Yukawa coupling via a scan of the $t\bar{t}$ threshold. We present the first prospect study of the simultaneous determination of these parameters, incorporating the latest reference detector design for the Circular Electron-Positron Collider (CEPC). We find that the precision of the top-quark mass measurement can reach a few MeV excluding the theoretical uncertainty on the cross-section, which is nearly two orders of magnitude better than the high-luminosity LHC (HL-LHC) projections. The current theoretical uncertainty of the cross-section calculation is the limiting factor.

   hep-ph0 citations
9. 09*

   A Continuum Schwinger Method to Study the Pion's Generalized Parton Distribution

   J.M. Morgado-Chávez🇪🇸 · J. Segovia🇪🇸 · F. de Soto🇪🇸 · J. Rodríguez-Quintero🇪🇸 · V. Bertone🇫🇷 · M. Defurne🇫🇷 · C. Mezrag🇫🇷 · H. Moutarde🇫🇷

   Generalised Parton Distributions (GPDs) provide multidimensional insight into hadron structure and are particularly relevant for the pion, whose dynamics are intimately linked to chiral symmetry breaking. We introduce a novel modelling strategy for pion GPDs that satisfies all QCD constraints by construction: support, polynomiality, positivity, and the soft-pion theorem. The approach is illustrated with a simple algebraic model, which is evolved and used to compute deeply virtual Compton scattering (DVCS) Compton Form Factors at next-to-leading order. Our results indicate that gluons dominate the pion response at the Electron Ion Collider kinematics.

   hep-phhep-exhep-latnucl-ex+1Acta Phys.Polon.Supp.(2026)·0 citations
10. 10*

    Pseudoscalar and vector toponia in a Dyson--Schwinger--Bethe--Salpeter framework

    H.-R. Zhang🇨🇳 · Z.-F. Cui🇨🇳 · J. Segovia🇪🇸

    We study the pseudoscalar ($J^{PC}=0^{-+}$) and vector ($1^{--}$) top--antitop (toponium) systems within the rainbow--ladder truncation of the Dyson--Schwinger and Bethe--Salpeter equations, employing the Qin--Chang effective interaction. After validating the framework in the charmonium and bottomonium sectors, we extend it consistently to the top sector, incorporating renormalisation-group running of the current quark mass and a careful treatment of the number of active flavours. We compute masses and leptonic decay constants for $N_f=5$ and $6$, then analyse their dependence on the renormalisation scale in the range $\mu =400-800\text{GeV}$. The resulting toponium masses lie near $344-346\text{GeV}$ with hyperfine splittings below $0.14-0.17\text{GeV}$, while the decay constants are large, $6-7\text{GeV}$, and exhibit the expected heavy-quark scaling behaviour. We find only mild sensitivity to the renormalisation point and a systematic reduction of binding when increasing $N_f$. Although the physical top quark decays weakly before hadronisation, our results demonstrate that, within a Poincaré-covariant nonperturbative framework, quantum chromodynamics (QCD) generates tightly correlated pseudoscalar and vector toponium systems in that extreme heavy-quark limit.

    hep-phhep-exhep-latnucl-ex+1PRD(2026)·2 citations
11. 11*

    Dynamical Determination of the Cut-off Scale in Loop-Induced Neutrino Mass Models with Non-Invertible Symmetry

    Hiroshi Okada🇨🇳 · Jia-Jun Wu🇨🇳

    We propose our framework as an effective field theory valid below the cut-off scale $\Lambda$, in which we explain the tiny scale of neutrino masses by integrating a non-invertible symmetry with the dynamical determination of the cut-off scale. In our model, we introduce three families of SU(2)${}_L$ quintet fermions (${\Sigma }_R$) and a quartet scalar (${\varphi }_4$), both of which are charged under the Fibonacci fusion rule (FFR). A central feature of this construction is that the vacuum expectation value (VEV) $v_4$ of ${\varphi }_4$ is induced at the one-loop level via dynamical symmetry breaking. To resolve the inherent arbitrariness of the cut-off scale $\Lambda$ in loop-induced VEV models, we identify $\Lambda$ with the scale at which the SU(2)${}_L$ gauge coupling $g_2$ encounters the renormalization group evolution (RGE) of $g_2$, naturally fixing the physical cut-off within the range of approximately $10^5$ to $10^7$ GeV. Quantitatively, this framework yields $v_4\sim 0.07-0.1$ GeV, which in turn leads to neutrino Yukawa couplings on the order of $10^{-3}$. This result provides a significantly more natural explanation for the neutrino mass hierarchy compared to standard seesaw models, which typically require couplings as small as $10^{-6}$ or less. Notably, our approach maintains a relatively simple particle content and does not necessitate additional (gauge) bosons for symmetry breaking.

    hep-phPRD(2026)·4 citations
12. 12*

    Inclusive heavy meson photoproduction in $pPb$ and $PbPb$ collisions

    Victor P. Goncalves🇧🇷 · Luana Santana🇧🇷 · Wolfgang Schäfer🇵🇱

    The inclusive photoproduction of heavy mesons in ultraperipheral $pPb$ and $PbPb$ collisions at the LHC energies is investigated considering the color dipole $S$-matrix formalism and assuming distinct models for the unintegrated gluon distribution, based on different assumptions for the description of the QCD dynamics. In particular, predictions for the $B^0$-meson photoproduction are presented here for the first time. The study of the $D^0$-meson photoproduction is revisited by estimating the impact of the treatment of the heavy charm fragmentation on the predictions and extended for $pPb$ collisions. Moreover, the contribution associated with the $b\to D^0$ transition is estimated. Our results indicate that a future experimental analysis of the heavy meson photoproduction will provide important constrains on the description of the hadronic structure at high energies.

    hep-phhep-exnucl-exnucl-thPRD(2026)·0 citations
13. 13*

    On probing self interacting dark matter models through the absorption of gravitational waves

    Víctor Fonoll🇪🇸

    In the forthcoming years, the study of the fundamental interactions between gravitational waves (GWs) and matter will be crucial in order to understand what the new generations of GWs detectors will tell us. We present the inverse bremsstrahlung (IB) absorption of GWs as a novel approach to GWs physics that can help set constraints on different physical models. We study the absorption of GWs in scattering processes of interacting dark matter. The observation of GWs of a given frequency sets constraints on its absorption efficiency. In the case of interacting dark matter, this can translate to constraints on its mass-coupling space, or in its temperature. For this, we parametrize the absorption of GWs in DM halos and in IGM, at low and very high redshifts. We find the arising constraints to be less stringent than existing ones.

    hep-phPoS(2026)·0 citations
14. 14*

    Neutrino mass variables in 3 active and 2 sterile neutrino scenario

    Srubabati Goswami🇮🇳 · Hemanth M.🇮🇳 · Debashis Pachhar🇮🇳 · N Rajeev🇮🇳

    The three-flavor framework of neutrino oscillations successfully explains most experimental results, but persistent anomalies at short- and long-baseline experiments hint at the existence of additional light sterile states. In particular, eV-scale sterile neutrinos are motivated by LSND and MiniBooNE results, while sub-eV sterile states with mass-squared differences at the $10^{-2}$ and $10^{-5}$~eV${}^2$ scales have been proposed to address the T2K--NO$\nu$A tension and the absence of the expected upturn in the solar neutrino energy spectrum, respectively. Such sterile states are singlets under the Standard Model gauge group and mix only through their admixture with active neutrinos. In this work, we investigate the phenomenology of the $3+2$ scenario, incorporating one eV-scale sterile neutrino together with a sub-eV state, and analyze their impact on absolute-mass related observables: the sum of neutrino masses $\Sigma$ constrained by cosmology, the effective electron neutrino mass $m_{\beta }$ from beta decay, and the effective Majorana mass $m_{\beta \beta }$ probed in neutrinoless double beta decay. We demonstrate that the presence of two sterile states can significantly modify the allowed parameter space compared to the three-flavor and $3+1$ frameworks, with some mass-ordering schemes already disfavored by current cosmological and laboratory limits. Finally, we assess the implications of upcoming sensitivities from KATRIN, Project~8, and LEGEND-1000, highlighting the complementary role of sub-eV sterile neutrinos in probing physics beyond the minimal three-flavor paradigm.

    hep-phPRD(2026)·1 citation
15. 15*

    Deep learning topological inference-guided $T_{cc}^{+}$ pole parameter extraction

    Julius B. Pagayon🇵🇭 · Klarence Tomas R. Cervantes🇵🇭 · Denny Lane B. Sombillo🇵🇭

    We perform a data-driven study of the doubly charmed tetraquark candidate $T_{cc}^{+}$. An ensemble of deep neural network classifiers, trained on synthetic amplitudes with controlled analytic structures, identifies a dominant pole topology characterized by an isolated pole on the $[bt]$ Riemann sheet which is robust against left-hand cut effects. A subsequent pole parameter extraction was performed via the uniformized $\mathcal{S}$-matrix and a complementary $\mathcal{K}$-matrix parameterization, which respectively provides a model-independent baseline and dynamical insight on the pole position and trajectory of the resonant state. Using this two-pronged approach, we submit that the $T_{cc}^{+}$ is a shallow $D^0{D}^{\ast +}$ bound state in the second Riemann sheet of the complex plane.

    hep-phPRD(2026)·1 citation
16. 16*

    On the size of gluon occupancies in saturation

    A. H. Mueller🇺🇸

    The size of gluon occupancies, or equivalently the nuclear gluon TMD, at gluon transverse momentum $k_{\perp }\le Q_s(Y)$ is evaluated. Without Sudakov corrections the occupations can become arbitrarily large while Sudakov effects lead to maximum occupancies of size $(1/\alpha {)}^{3/2}$. Results are the same for running coupling and fixed coupling dynamics. The coherent (elastic) TMD and inelastic gluon TMD are the same in the gluon saturation region. The saturated gluons in the light cone wavefunction seem to have little or no interaction among themselves.

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

    Universal scaling of transport coefficients near the liquid-gas critical point

    Johannes V. Roth🇩🇪 · Yunxin Ye🇩🇪 · Sören Schlichting🇩🇪 · Lorenz von Smekal🇩🇪

    We employ a novel real-time formulation of the functional renormalization group (FRG) to compute universal scaling functions of the thermal diffusivity and the shear viscosity in the vicinity of the liquid-gas critical point, i.e., for the dynamic universality class of Model H from the Halperin-Hohenberg classification. We map out the universal dependence of the transport coefficients on temperature, external magnetic field, and wavenumber, and provide a detailed comparison with the Kawasaki approximation, which is here obtained from a perturbative one-loop approximation to our real-time FRG flow. In contrast to the Kawasaki approximation, the non-perturbative scaling functions from the full real-time FRG flow show a mild dependence on the thermodynamic path towards the critical point. We further compare our FRG results for the universal wavenumber and temperature dependence of the thermal diffusivity with experimental data from critical fluids.

    hep-phcond-mat.stat-mechnucl-th2 citations
18. 18*

    Embedding light dark matter and small neutrino mass in the flipped standard model

    D. T. Huong🇻🇳 · Phung Van Dong🇻🇳 · A. E. Carcamo Hernandez🇨🇱

    We revisit the flipped standard model where a $U(1{)}_N$ gauge group is added, determining a dark charge through the weak isospin such as $D=T_3+N$, analogous to the electric charge and hypercharge relation. We find %discover that neutrino masses are appropriately generated by a radiative inverse seesaw mechanism mediated by dark fields. Dark matter candidate is a naturally light fermion with the mass radiatively induced at the keV scale. The residual $Z_2$ parity arising from $U(1{)}_N$ symmetry breaking both stabilizes the dark matter candidate and prevents its potential mixing with neutrinos. Such residual $Z_2$ parity also guarantees the radiative nature of the inverse seesaw mechanism responsible for light active neutrino mass generation. It is noted that the keV dark matter may be thermally produced in the early Universe as decoupled but being still relativistic and typically overpopulated due to $U(1{)}_N$ portal interactions. To achieve the correct abundance, the excessive thermal production is counterbalanced by sufficient late-time entropy generation from the decay of long-lived particles. The parameter space under consideration can simultaneously accommodate the observational data from cosmic inflation and keV dark matter.

    hep-phhep-th0 citations
19. 19*

    Decay and structure of heavy flavour

    Stefan Groote🇪🇪 · Arpan Chatterjee🇪🇪 · Maria Naeem🇪🇪

    In accordance to the aim of the constituing meeting of the COST action CA24159 ``Structure and Spectroscopy of Hadrons Research Project'' to introduce the different groups to the action, in this talk we give an overview over the subjects dealt with by the working group in Tartu related to hadron physics. We deal with the production and the nonleptonic decays of charmed baryons in the framework of the current algebra approach in terms of tensor invariants and explain how this approach can be used to approach CP violation via long distance effects in rescattering. New physics effects can be even seen in the classical neutron beta decay, but the helicity approach used here is also useful for e.g.\ calculating first order electroweak radiative corrections to the decay of the polarised $W$ boson. Identical particle and mass effects are seen in the Higgs decay into four leptons of the same type. The second main part starts with indications for the intrinsic charm mechanism, explaining the discrepancy between the results of SELEX and LHCb. The solution offered here is valid only if one considers nonlocal field operators. The nonlocal extension of the Nambu--Jona-Lasinio model, derived directly from QCD and combined with the relativistic Faddeev approach, allows for the description of hadronic states. We conclude by presenting open questions to the action.

    hep-ph0 citations
20. 20*

    Phasing out Dark Matter Isocurvature with Thermal Misalignment

    Brian Batell🇺🇸 · Akshay Ghalsasi🇺🇸 · Subhajit Ghosh🇺🇸 · Mudit Rai🇺🇸

    Thermal misalignment provides an alternative to the standard misalignment mechanism for the cosmological production of scalar dark matter. In this framework, feeble couplings to particles in the thermal bath generate a finite-temperature potential that drives the scalar towards large field values early in the radiation era, dynamically inducing the misalignment before the onset of scalar oscillations. As a result, the relic abundance is controlled primarily by particle masses and couplings rather than the initial field value. As a light spectator field, the scalar acquires inflationary fluctuations that are uncorrelated with the adiabatic curvature mode, generically sourcing isocurvature perturbations. We show that, unlike standard misalignment, where light scalars are strongly constrained by cosmic microwave background bounds on dark matter isocurvature for high-scale inflation, thermal misalignment can naturally suppress the isocurvature signal. This occurs through a novel late-time phase offset between the background zero mode and the superhorizon perturbations, which reduces the final dark matter density contrast. Thermal misalignment therefore provides a new and generic route to isocurvature-safe scalar dark matter.

    hep-phastro-ph.CO4 citations
21. 21*

    Vector Resonances at Muon and Wakefield Colliders

    Massimo Cipressi🇮🇹 · Kevin Langhoff🇺🇸 · Toby Opferkuch🇮🇹

    We explore the potential of future high-energy lepton colliders to probe heavy vector resonances. At wakefield colliders, intense beam-beam interactions produce radiation, called beamstrahlung, which redistributes luminosity from the nominal energy across a broad spectrum of lower collision energies. We show that this effect, conventionally viewed as a drawback, dramatically enhances sensitivity to resonances by effectively scanning a wide range of center-of-mass energies. We present projections for a benchmark scenario of a heavy kinetically mixed $Z^{\prime }$.

    hep-ph4 citations
22. 22*

    High-Frequency Gravitational Waves from Phase Transitions in Nascent Neutron Stars

    Katarina Bleau🇩🇪 · Joachim Kopp🇨🇭 · Jiheon Lee🇰🇷 · Jorinde van de Vis🇨🇭

    Tentative evidence suggests that the cores of massive neutron stars consist of deconfined quark matter. We argue that the formation of such a quark matter core during a galactic supernova could be accompanied by the emission of gravitational waves in the MHz band. These signals constitute a new target for high-frequency gravitational wave detectors, demonstrating that such detectors may offer unique opportunities for testing quantum chromodynamics in an otherwise inaccessible regime.

    hep-phastro-ph.HEgr-qc5 citations
23. 23*

    Two-Component Dark Matter in the Type-I 2HDM

    Patricio Escalona🇧🇷 · Jacinto P. Neto🇧🇷 · M. J. Neves🇧🇷 · Camila Ramos🇧🇷 · David Suarez🇧🇷

    We investigate a two-component dark matter scenario in the type-I two-Higgs-doublet model. The dark sector contains a real scalar $s$ and a Dirac fermion $\chi$, whose stability is ensured by a $Z_4$ symmetry together with kinematic conditions. The scalar interacts with the visible sector through Higgs-portal couplings, while the fermion interacts with the scalar via Yukawa interactions. In this framework, we analyze the thermal freeze-out production of both candidates, accounting for annihilation, conversion, and semi-annihilation processes. A comprehensive scan over the multidimensional parameter space is performed in terms of physical masses, mixing angles, and portal couplings, imposing theoretical requirements such as perturbativity and vacuum stability. We confront the model with current experimental constraints, including the observed relic abundance, invisible Higgs decays, direct detection limits on spin-independent scattering cross sections, and electroweak precision observables. We find that viable regions of parameter space can satisfy all dark matter constraints, but collider bounds strongly constrain the scalar sector, narrowing the allowed regions and creating tension with those favored by dark matter phenomenology, particularly in the sub-TeV mass regime.

    hep-ph0 citations
24. 24*

    Natura Non Facit Saltum: An Analytical Model of Smooth Slow-Roll to Ultra-Slow-Roll Transition

    Diego Cruces🇨🇳 · Minxi He🇰🇷 · Shi Pi🇨🇳 · Jianing Wang🇯🇵 · Masahide Yamaguchi🇰🇷 · Yuhang Zhu🇰🇷

    In this letter, we propose a single-field inflation model that realizes a slow-roll-to-ultra-slow-roll transition while keeping the second slow-roll parameter smoothly varying throughout. The model is built through a minimal modification by introducing a simple time dependence in the effective mass term of the Mukhanov-Sasaki equation. We obtain fully analytical solutions for both the background evolution and the curvature perturbations, which makes the parameter dependence of the curvature power spectrum easy to track. To the best of our knowledge, this is the first analytical model that describes a smooth transition of this kind. We also compare its signatures with those of the corresponding sharp-transition counterpart.

    ↳ astro-ph.COgr-qchep-phhep-th5 citations
25. 25*

    Hydrodynamics of dilation and spin currents

    Zhong-Hua Zhang🇨🇳 · Xi-Hu Lv🇨🇳 · Xu-Guang Huang🇨🇳

    We formulate a relativistic hydrodynamic theory for fluids with spin and intrinsic dilation charges. Using an entropy-current analysis, we derive constitutive relations featuring a bulk viscosity and a dilation conductivity governing the relaxation and diffusion of dilation charge. Linear mode analysis reveals a gapped dilation excitation and the freeze-out of long-wavelength sound modes, similar to the superhorizon modes in cosmology. In the nonrelativistic limit, the theory reduces to that of microstretch fluids. Upon coupling to electromagnetic field, we show that the scale anomaly permits additional contributions in the electric current, dilation current, and energy-momentum tensor. Our theory naturally applies to nearly conformal fluids undergoing rapid expansion or contraction.

    ↳ hep-thcond-mat.softhep-phnucl-th+11 citation
26. 26*

    Discrete Dyson-Schwinger equations

    Marco Frasca🇮🇹

    We develop the discrete set of Dyson-Schwinger equations for scalar fields and solve them for some cases. We show that their solutions are Gaussian in the continuum limit as expected from the theorems of Aizenman and of Aizenman and Duminil-Copin for $d\ge 4$. Extension to lower dimensionality fails, as it should, by observing that the triviality theorems used in our proof are not applicable in such cases.

    ↳ math-phhep-phhep-thmath.MPPRD(2026)·1 citation
27. 27*

    Asymptotics of superfluid Bjorken flow

    Alexander Soloviev🇸🇮 · Michał Spaliński🇫🇮

    We consider the dynamics of an expanding superfluid modeled by Mueller-Israel-Stewart theory coupled to a complex scalar field with a $U(1)$ symmetry that is spontaneously broken. This is a manageable theoretical setting for explorations of the chiral phase transition of expanding quark-gluon plasma. We study the late proper-time behavior of Bjorken flow in this physical system and find that asymptotic solutions can be expressed as a transseries of a novel form, which contains factors like ${\tau }^{-a\ln \tau }$. This transseries describes how the information encoded in the initial data is diluted in the course of dissipative evolution. These solutions retain memory of the symmetry-breaking transition and describe two qualitatively different late-time behaviors of the dynamical variables, depending on condensate relaxation rate: either a purely damped fall-off or damped oscillations. The possibility that such oscillations could be imprinted in the observed outcomes of heavy ion collision experiments is the main physical insight that follows from our analysis.

    ↳ hep-thhep-phnucl-thPRD(2026)·0 citations
28. 28*

    High-redshift physics from the acoustic scale

    Zachary J. Weiner🇨🇦

    We present a simplified and general description of the high-redshift information in acoustic scale measurements from the cosmic microwave background and large-scale structure. The transverse distance interval between photon--baryon decoupling and a late epoch in the matter era provides an analytically tractable summary statistic thereof and a general diagnostic of the current tension between the Dark Energy Spectroscopic Instrument and the CMB. We show that this "matter-era distance excess" is unlikely to be explained by modified dynamics at low redshift. We then analytically derive the matter-era distance interval's sensitivity to new physics at high redshift, including nonstandard recombination, nonminimal dark matter dynamics, and spatial curvature; in particular, we explain how this observable represents a direct geometric measurement of (and underlies the current incompatibility with) neutrino masses. Finally, we demonstrate that phenomenological models of dynamical dark energy mediate the matter-era distance excess in a manner reliant on their unphysical, extrapolated behavior at high redshift. Invoking alternative explanations of the excess removes the CMB's contribution to the evidence for these models; the residual preference of around $1.7\sigma$ mostly derives from DESI's two lowest-redshift measurements of the Alcock--Paczynski distortion, without which it drops to $0.5\sigma$.

    ↳ astro-ph.COhep-phJCAP(2026)·21 citations
29. 29*

    Branching Universes

    Anamaria Hell🇯🇵 · Tatsuya Daniel🇨🇦

    We propose the idea that our Universe is a realization among different possible branches, which can be observationally tested through the modified dispersion relation of the gravitational waves. We achieve this through a framework of spatially constrained vector fields. We show that the simplest realizations of such theories in flat and cosmological spacetimes do not introduce new propagating modes, but they give rise to tensor perturbations that differ from those of standard general relativity. We further show that such theories admit stealth black hole solutions, and we recover weak gravitational potentials, thus passing the solar system experiments. Finally, we discuss the implications of such theories and propose further generalizations.

    ↳ hep-thastro-ph.COgr-qchep-ph4 citations

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