Wed·Oct 15, 2025Wednesday·October 15, 2025

1. 01*

   Dynamically generated tilt of isocurvature fluctuations

   Saarik Kalia🇺🇸

   Light scalar fields acquire isocurvature fluctuations during inflation. While these fluctuations could lead to interesting observable signatures at small scales, they are strongly constrained on large scales by cosmic microwave background observations. When the mass of the scalar is much lighter than the inflationary Hubble scale, $m\ll H_I$, the spectrum of these fluctuations is flat. Meanwhile, if $m\gg H_I$, the fluctuations are suppressed. A blue-tilted isocurvature spectrum which exhibits enhanced structure on small scales but avoids observational constraints on large scales therefore requires a coincidence of scales $m\sim H_I$ for a free massive scalar. In this work, we show that if a scalar field possesses a nontrivial potential, its inflationary dynamics naturally cause this condition to be satisfied, and so a blue-tilted spectrum is generically expected for a large class of potentials. Specifically, if its potential $V$ exhibits a region which satisfies the slow-roll condition $V^{\prime \prime }<3H_I^2$, the scalar condensate will spend most of inflation close to the boundary of this region, so that its effective mass is typically close to $H_I$. The resulting blue tilt is inversely proportional to the number of $e$-folds of inflation prior to horizon crossing. If the scalar is long-lived, this mechanism leads to an attractor prediction for its relic abundance, which is insensitive to initial conditions of the scalar. In particular, a scalar field with quartic self-interactions can achieve the correct abundance to constitute all of the dark matter for a wide range of masses. We compute the relationship between the mass and self-coupling of quartic dark matter predicted by this mechanism.

   hep-phastro-ph.COgr-qchep-thPRD(2026)·4 citations
2. 02*

   Modeling the TMD shape function in $J/\psi$ electroproduction

   Miguel G. Echevarria🇪🇸 · Raj Kishore🇪🇸 · Samuel F. Romera🇪🇸

   The next-to-leading order hard function for quarkonium electroproduction is calculated within the framework of transverse-momentum-dependent (TMD) factorization in the low-transverse-momentum regime. The structure of the TMD shape function in quarkonium leptoproduction is analyzed through its operator-level definition. Particular attention is given to the convolution of the unpolarized TMD gluon distribution with the TMD shape function, thereby illustrating the latter's phenomenological role. Building on this framework, we provide predictions for the unpolarized differential cross-section of $J/\psi$ electroproduction at the future Electron-Ion Collider in the region of small transverse momentum.

   hep-phJHEP(2026)·6 citations
3. 03*

   A SHIFT of Perspective: Observing Neutrinos at CMS and ATLAS

   Alfonso Garcia-Soto🇪🇸 · Jeremi Niedziela🇩🇪

   The SHIFT@LHC proposal introduced a novel shifted gaseous fixed-target concept at the LHC to search for exotic particles. In this letter, we explore an entirely different physics opportunity enabled by this setup: the observation of neutrinos in general-purpose LHC detectors. Using simulations of proton-gas collisions, hadron propagation, and neutrino interactions, we estimate that $O(10^4)$ muon-neutrino and $O(10^3)$ electron-neutrino interactions, with energies from 20 GeV to 1 TeV, would occur in the CMS and ATLAS detectors with 1% of the LHC Run 4 integrated luminosity ($\approx 4\cdot 10^{25}$ protons-on-target). This unique configuration provides access to hadron production in the pseudorapidity range $5<\eta <8$, complementary to existing LHC detectors. If realized, this would mark the first detection of neutrinos in a hadron collider detector, demonstrating the feasibility of such measurements in this experimental environment.

   hep-phhep-exPRD(2026)·0 citations
4. 04*

   New Tests of Low-Scale Quantum Gravity with Cosmic-Ray Collisions

   Manuel Ettengruber🇫🇷 · Gonzalo Herrera🇺🇸

   Cosmic ray collisions at high center of mass energy could enable graviton and black hole production as expected in theories of low-scale quantum gravity, such as extra-dimensions, many species, or some versions of string theory. Here we propose three novel phenomenological tests of these theories. We first consider the collision of cosmic rays with ambient protons, electrons and photons in Active Galactic Nuclei (AGN), finding that high-energy neutrino data from the blazar TXS 0506+056 places a constraint on the fundamental scale of gravity of $M_f\gtrsim 0.3$ TeV, and future high-energy neutrino data could raise this bound to $M_f\gtrsim 200$ TeV. We then point out that collisions of pairs of cosmic rays could occur at a sizable rate in AGN where the accelerated cosmic rays are not collimated, or on supermassive black hole binaries. This consideration could potentially let us test unprecedented large fundamental scales of $M_f\gtrsim 2$ PeV. We further compute the corresponding thermal neutrino emission arising from the Hawking evaporation of black holes produced in cosmic ray collisions, finding a spectrum that clearly differs from that expected in meson decays. Finally, we speculate with an scenario which would produce high-energy neutrino and gamma-ray emission from regions in the sky where no multi-wavelength counterparts would be expected, via graviton propagation from a different brane, which then decays in our Universe.

   hep-phastro-ph.HEgr-qchep-th2 citations
5. 05*

   Spectroscopy of charmonium-like mesons, heavy-light mesons with charm, AdS/QCD, and configurational entropy

   A. E. Bernardini🇵🇹 · W. de Paula🇧🇷 · R. da Rocha🇧🇷

   Heavy-light-flavor meson resonances with charm, in the $D^0$ and $D^{\ast }$ families, and charmonium-like states, in the ${\eta }_c$ and ${\chi }_{c1}$ families, are explored and discussed in the AdS/QCD model with four quark flavors. The differential configurational entropy is computed and analyzed for these four charmed meson families, also combining 4-flavor AdS/QCD to experimental data for the $D^0$, $D^{\ast }$, ${\eta }_c$, and ${\chi }_{c1}$ meson families. It makes it possible to predict the mass spectrum of unexplored heavier charmed meson resonances and to identify further charmed meson states reported in PDG.

   hep-phhep-thAnnals Phys.(2025)·0 citations
6. 06*

   Gravitational Wave Signatures from Lepton Number Breaking Phase Transitions with Flat Potentials

   Gabriela Barenboim🇪🇸 · Yeji Park🇰🇷 · Liliana Velasco-Sevilla🇰🇷

   Extensions of the Standard Model typically contain ``flaton fields" defined as fields with large vacuum expectation values and almost flat potentials where scalar self-coupling is small or vanishes at tree level. Such potentials have been used to drive a secondary inflationary epoch after a primary phase of inflation, in what are called thermal inflation models. Although the primordial, high-scale inflationary epoch can solve the horizon and flatness problems, it does not always resolve difficulties associated with late-time relics produced in extensions of the Standard Model. These relics typically decay too late, injecting entropy and energetic particles that spoil successful predictions like Big Bang Nucleosynthesis. It is here that thermal inflation plays a crucial role: diluting unwanted relics by many orders of magnitude without erasing the baryon asymmetry or the large-scale structure set up by the earlier phase of inflation. The preferred scale for this phenomenon is in the range $10^6-10^8$ GeV if one considers supergravity, but without it, any scale above the EW scale is valid. We investigate a typical form of these potentials and determine what are the conditions for the potentials to develop a barrier such that when the flatons settle to the true minimum, the associated Gravitational Waves can be observed, focusing on first-order phase transitions from spontaneous lepton number breaking.

   hep-phastro-ph.COJHEP(2026)·1 citation
7. 07*

   Jet quenching without energy loss

   Liliana Apolinário🇵🇹 · Chiara Le Roux🇸🇪 · Korinna Zapp🇸🇪

   The onset of jet quenching, i.e. the suppression of high transverse momentum particles and jets, is an important question in the context of understanding the onset of collective behaviour and small collision systems. We investigate a minimal scenario where a hard parton experiences a single soft re-scattering that leaves the kinematics unmodified, but the colour exchange leads to a loss of colour coherence that is observable in the final distribution of fragments. In particular, the formation time of the first splitting as reconstructed at hadron level from jets using the formation time clustering algorithm is sensitive the loss of colour coherence. Moreover, it can distinguish the coherence loss scenario from a corresponding energy loss scenario, since small energy loss effects leave the formation time distribution unchanged.

   hep-ph2 citations
8. 08*

   First simultaneous global QCD analysis of kaon and pion parton distributions with lattice QCD constraints

   P. C. Barry🇺🇸 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸 · N. Sato🇺🇸 · Fernanda Steffens🇩🇪

   We perform the first simultaneous global QCD analysis of pion and kaon parton distribution functions (PDFs), constrained by pion- and kaon-induced Drell-Yan (DY) and leading neutron electroproduction data, together with lattice QCD data on pion and kaon PDF moments. The analysis indicates a softer valence $\bar{u}$ distribution in the $K^{-}$ than in the ${\pi }^{-}$, and a significantly more peaked valence $s$-quark density in $K^{-}$ compared with the $\bar{u}$. The effective exponent governing the high-$x$ behavior of the PDF is found to be larger for $\bar{u}$ in the kaon, ${\beta }_{\bar{u}}^{K^{-}}=1.6(2)$, than in the pion, ${\beta }_{\bar{u}}^{{\pi }^{-}}=1.16(4)$, in the range $0.7\le x\le 0.95$. From the gluon momentum fractions we find the pion's gluon content accounts for $\approx 1/3$ of the mass budget of the pion at $\mu =2\mathrm{GeV}$, but only $\approx 1/4$ for the kaon.

   hep-phhep-exhep-latnucl-thPRD(2026)·19 citations
9. 09*

   A Solution to the Hierarchy Problem with Non-Linear Quantum Mechanics

   David E. Kaplan🇺🇸 · Surjeet Rajendran🇺🇸

   We argue that the hierarchy problem of the standard model of particle physics can be solved by adding a state-dependent term to the Higgs sector. We present an example of a scalar field with a Higgs-like potential with an additional term proportional to the expectation value of the squared Higgs field operator. We show that the mass can be parametrically lighter than the theory's energy-momentum cutoff without fine tuning. We find the Higgs mass can be technically natural, even with a Planck-scale cutoff. The simplest version of the theory may not be distinguishable from the standard model at colliders, but other versions might. In addition, some aspects of cosmological evolution can be different in this model, in some cases radically.

   hep-phhep-th0 citations
10. 10*

    Gradient-flowed operator product expansion without IR renormalons

    Martin Beneke (TU Munich)🇩🇪 · Hiromasa Takaura (Kyoto University)🇯🇵

    A long-standing problem concerns the question how to consistently combine perturbative expansions in QCD with power corrections in the context of the operator product expansion (OPE), since the former exhibit ambiguities due to infrared renormalons, which are of the same order as the power corrections. We propose to use the gradient flow time $1/\sqrt{t}$ as a factorization scale and to express the OPE in terms of IR renormalon-free subtracted perturbative expansions and unambiguous matrix elements of gradient-flow regularized local operators. We show on the example of the Adler function and its leading power correction from the gluon condensate that this method dramatically improves the convergence of the perturbative expansion. We employ lattice data on the action density to estimate the gradient-flowed gluon condensate, and obtain the Adler function with non-perturbative accuracy and significantly reduced theoretical uncertainty, enlarging the predictivity at low $Q^2$. When applied to the hadronic decay width of the tau lepton, the method resolves the long-standing discrepancy between the fixed-order and contour-improved approach in favour of the fixed-order treatment.

    hep-phhep-lathep-thJHEP(2026)·9 citations
11. 11*

    Improved perturbative QCD study of the decay $B_c^{+}\to {\eta }_c{L}^{+}$

    Wen-Jing Zhang🇨🇳 · Xin Liu🇨🇳

    We perform an improved perturbative QCD study of the decays $B_c^{+}\to {\eta }_c{L}^{+}$,where $L$ denotes the light ground-state pseudoscalar, vector mesons and the corresponding $p$-wave scalar, axial-vector, and tensor ones, and predict their branching ratios (BRs) associated with relative ratios at leading order in the strong coupling ${\alpha }_s$. Our results $\mathrm{BR}(B_c^{+}\to {\eta }_c{\pi }^{+})=(2.03_{-0.41}^{+0.53})\times 10^{-3}$ and $\mathrm{BR}(B_c^{+}\to {\eta }_c{\pi }^{+})/\mathrm{BR}(B_c^{+}\to J/\psi {\pi }^{+})=1.74_{-0.50}^{+0.66}$ are consistent with several available predictions in different approaches within uncertainties. Inputting the measured ${\eta }_c\to p\bar{p}$ and ${\eta }_c\to {\pi }^{+}{\pi }^{-}({\pi }^{+}{\pi }^{-},K^{+}{K}^{-},p\bar{p})$ BRs with $p$ here being a proton, we derive the multibody $B_c^{+}\to {\eta }_c(\pi ,\rho {)}^{+}$ BRs through secondary decay chains via resonance ${\eta }_c$ under the narrow-width approximation, which might facilitate the (near-)future tests of $B_c\to {\eta }_c$ decays. Under the $q\bar{q}$ assignment for light scalars, different to $B_c$ decaying into $J/\psi$ plus a scalar meson and other $B_c^{+}\to {\eta }_c{L}^{+}$ modes, surprisingly small $\Delta S=0$ BRs around $\mathcal{O}(10^{-7}-10^{-9})$ and highly large ratios near $\mathcal{O}(10^2)$ between the $\Delta S=1$ and $\Delta S=0$ BRs are found in the $B_c$ decays to ${\eta }_c$ plus light scalars, with $S$ being strange number. Many large BRs and interesting ratios presented in this work could be tested by the Large Hadron Collider experiments, which would help us to examine the reliability of this improved perturbative QCD formalism for $B_c$-meson decays and further understand the QCD dynamics in the considered decay modes, as well as in the related hadrons.

    hep-phhep-exPRD(2026)·1 citation
12. 12*

    Constraining Heavy Neutral Leptons Coupled to the Tau-Neutrino Flavor at the Large Hadron Collider

    Edis D. Tireli🇩🇰 · Rikke S. Klausen🇩🇰 · Oleg Ruchayskiy🇩🇰

    Displaced vertex (DV) signatures at colliders offer a powerful probe of new long-lived particles beyond the Standard Model. Among the best-motivated candidates are heavy neutral leptons (HNLs) - heavier counterparts of Standard Model neutrinos - which can account for the origin of neutrino masses and potentially produce di-leptonic DV signatures. In this study, we demonstrate how existing DV searches at the LHC can be extended to probe HNLs that couple predominantly to the tau-neutrino flavor. While current search strategies rely on identifying a prompt lepton alongside a displaced vertex, we show that analyzing events without a prompt lepton enables sensitivity to the process $pp\to W\to \tau N$, where the tau decays hadronically and the HNL subsequently decays to a lepton pair and a neutrino. We perform detailed Monte Carlo simulations of this process with HNLs decaying to ${\mu }^{+}{\mu }^{-}$ or $e^{+}{e}^{-}$ final states, apply ATLAS-inspired selection criteria, and optimize signal sensitivity. In particular, we demonstrate that appropriate cuts in the plane of di-lepton invariant mass and DV radial position significantly enhance signal visibility. We propose several such optimized strategies and show that even with Run 2 data $139{\text{fb}}^{-1}$ , existing bounds can be improved by more than an order of magnitude. Future high-luminosity runs may strengthen sensitivity by up to three orders of magnitude compared to current limits.

    hep-phhep-exPRD(2026)·1 citation
13. 13*

    Search for the $D^{\ast }{\bar{D}}^{\ast }$ Molecular State $X_2(4013)$ in $K^{-}p$ and $pp$ Collisions

    Min Yuan🇨🇳 · Bo Nan Zhang🇨🇳 · Yin Huang🇨🇳

    Motivated by the interpretation of $X(3872)$ as a $D{\bar{D}}^{\ast }$ molecular state, heavy-quark spin symmetry predicts a spin-2 partner, $X_2(4013)$, which can be regarded as a $D^{\ast }{\bar{D}}^{\ast }$ molecule with quantum numbers $J^{PC}=2^{++}$. Its experimental confirmation, however, remains elusive. In this work, we investigate the production mechanisms of $X_2(4013)$ in the reactions $K^{-}p\to {\Lambda }_c^{+}{D}_s^{-}{X}_2(4013)$ and $pp\to {\Lambda }_c^{+}{\Lambda }_c^{+}{X}_2(4013)$ within an effective Lagrangian framework. The production processes are modeled via $t$-channel $D/{\bar{D}}^{\ast }$ meson exchanges, while initial-state interactions (ISI) mediated by Pomeron and Reggeon exchanges are also taken into account. Our calculations indicate that the total cross sections can reach the pb level, suggesting that $X_2(4013)$ may be accessible at current and future experiments such as AMBER@CERN and LHCb. Inclusion of ISI enhances the cross sections by nearly one order of magnitude. The differential distributions show distinct angular behaviors for the two reactions: the $K^{-}p$ reaction exhibits a forward-peaked distribution, whereas the $pp$ reaction shows a dip near central angles. This study provides a quantitative theoretical benchmark for future experimental searches of $X_2(4013)$ and highlights the importance of initial-state interactions (ISI) in high-energy particle investigations.

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

    Constraining neutrino electromagnetic properties with recent low-energy electron recoil data at dark matter direct detection experiments

    M. Demirci🇹🇷 · H. I. Sezer🇹🇷 · M. F. Mustamin🇹🇷 · A. B. Balantekin🇺🇸

    Neutrinos that are elastically scattered off atomic electrons provide a unique opportunity to investigate the Standard Model (SM) and beyond SM physics. In this work, we explore the new physics effects of neutrino electromagnetic properties through elastic neutrino-electron scattering using solar neutrinos at the low energy range of PandaX-4T and XENONnT experiments. The properties of interest include the neutrino magnetic moment, millicharge, and charge radius, all of which are natural consequences of non-zero neutrino masses. We investigate their effects by incorporating each property into the Standard Model (SM) framework, given the measured the solar neutrino flux. By analyzing the latest Run 0 and Run 1 datasets from the PandaX-4T experiment, together with recent results from XENONnT, we derive new constraints on each electromagnetic property of neutrino. We present both flavor-independent results, obtained using a common parameter for all three neutrino flavors, and flavor-dependent results, derived by marginalizing over the three neutrino flavor components. Bounds we obtained are comparable or improved compared to those reported in the previous studies.

    hep-phPRD(2025)·4 citations
15. 15*

    Initial-state geometry and multiplicity distributions in pp and pPb collisions

    R. Terra🇧🇷 · A. V. Giannini🇵🇹 · F. S. Navarra🇧🇷

    This work investigates the possibility of accessing the initial geometric shape of the proton in proton-proton and proton-nucleus collisions at the LHC. In particular, we look for manifestations of the configuration in which the proton is made of three quarks linked by a Y-shape gluon string, called baryon junction. This initial state spatial configuration has been used in the past to describe data on baryon rapidity distributions, diffractive $J/\psi$ production and multiplicity distributions in pp collisions. In spite of its success in explaining the data, the evidence of the baryon junction still needs confirmation. Further studies will be undertaken at the electron-ion collider. In this work we study multiplicity distributions measured in pp and pPb collisions. Different initial state geometries are used as input in a Monte Carlo event generator which implements the $k_T$-factorization formalism of the CGC with KLN unintegrated gluon distributions. The results show that the data on multiplicity distributions are good enough to discriminate between different initial state geometries. Moreover, they indicate that it is crucial to take into account the intrinsic fluctuations of the saturation scale.

    hep-phnucl-thPRD(2026)·3 citations
16. 16*

    Complementarity of gravitational wave analyses and di-Higgs production in the exploration of the Electroweak Phase Transition dynamics in the RxSM

    Johannes Braathen🇩🇪 · Sven Heinemeyer🇪🇸 · Carlos Pulido Boatella🇪🇸 · Alain Verduras Schaeidt🇩🇪

    The real singlet extension of the Standard Model (SM), RxSM, is one of the simplest Beyond-the-Standard Model (BSM) theories that can accommodate a strong first-order electroweak phase transition (SFOEWPT). We survey the possible thermal histories of the early Universe in the RxSM, and find that a SFOEWPT can occur in this model as single- or two-step phase transitions. We investigate complementary approaches to probe such scenarios experimentally: either via searches for a stochastic background of gravitational waves (GWs) or via searches for di-Higgs production processes at future collider experiments: the HL-LHC, or a possible high-energy $e^{+}{e}^{-}$ collider. For these analyses we consistently include one-loop corrections to the trilinear Higgs couplings. We find that entirely different phenomenological signals are possible, depending on how the SFOEWPT occurs. In scenarios where such a transition is driven by the Higgs doublet direction in field space, BSM deviations in properties of the detected Higgs boson, particularly in the trilinear scalar coupling, typically lead to observable signals at colliders, while the regions of parameter space with detectable GW signals are very narrow. On the other hand, if the SFOEWPT is triggered by the singlet field direction, the detected Higgs boson is very SM-like and no signs of BSM physics would appear in di-Higgs production processes. However, strong GW signals could be produced for significant parts of the RxSM parameter space with singlet-driven SFOEWPT. This work highlights the crucial importance of exploiting complementary experimental directions to determine the dynamics of the electroweak phase transition and access the shape of the Higgs potential realised in Nature.

    hep-phJHEP(2026)·14 citations
17. 17*

    High-energy photons from Gamma-Ray Bursts, but no neutrinos

    A. De Rújula (Instituto de Física Teórica (UAM/CSIC), Univ. Autónoma de Madrid, Spain and Theory Division, CERN, CH 1211 Geneva 23, Switzerland)🇪🇸

    The Cannon-Ball model of Gamma-Ray Bursts and their afterglows--described in the text and in innumerable previous occasions--is extremely successful and predictive. In a few intrinsically bright GRBs, gamma-rays with energies in the TeV range have been observed. The CB model, I argue, has no difficulty in describing the origin and approximate properties of these high-energy gamma rays and the extreme difficulty of observing their accompanying neutrinos.

    hep-phastro-ph.HE0 citations
18. 18*

    Dark Matter Boosted by Terrestrial Collisions

    Zamiul Alam🇺🇸 · Christopher V. Cappiello🇺🇸 · Francesc Ferrer🇺🇸

    Inelastic dark matter (IDM) models feature an energy threshold for scattering with Standard Model particles, which enables their consistency with the increasingly stringent limits placed by direct detection experiments. In a typical construction, elastic scattering is absent at tree level, and a lighter dark matter state must first upscatter into a heavier state in order to interact with the nuclei in the detector. We model the excitation of IDM in the Earth followed by its downscattering inside a detector, and we show that considering this process markedly enhances the sensitivity of existing detectors. In particular, current limits based on XENON100 and XENON1T data can be extended to significantly larger mass splittings.

    hep-phPRD(2026)·2 citations
19. 19*

    New Spallation Background Rejection Techniques to Greatly Improve the Solar Neutrino Sensitivity of JUNO

    Obada Nairat🇺🇸 · John F. Beacom🇺🇸 · Shirley Weishi Li🇺🇸

    While the potential of the Jiangmen Underground Neutrino Observatory (JUNO) to measure solar neutrinos is known, realizing this potential requires new techniques to reduce detector backgrounds. One of the most serious backgrounds is due to the beta decays of unstable nuclei produced through muon breakup (spallation) of nuclei. This background is much more significant in JUNO compared to Super-Kamiokande due to JUNO's shallower depth and its lack of directional information. We present the first detailed theoretical calculations of spallation backgrounds in JUNO, showing the underlying physical processes and new ways to cut backgrounds while preserving signals. A key point is showing the importance of neutron tagging to identify hadronic showers, which are rare but produce almost all of the dangerous isotopes. With our new techniques, JUNO will be able to reduce deadtime (signal loss) by a factor of about 4.5 and to reduce the running time needed to meet sensitivity goals by a factor of two. This will give JUNO greatly improved sensitivity to ${}^8$B and $hep$ solar neutrinos, as we will explore in a separate paper.

    hep-phastro-ph.HEhep-exnucl-ex+2PRD(2026)·3 citations
20. 20*

    Dark Matter-Electron Interactions Alter the Luminosity and Spectral Index of M87

    Abdelaziz Hussein🇺🇸 · Gonzalo Herrera🇺🇸

    We investigate the possibility that cosmic-ray electron cooling through dark matter-electron scatterings contributes to the low radiative efficiency observed in radio-loud galaxies such as M87. Light dark matter can scatter efficiently off electrons in M87, lowering the observed bolometric luminosity compared to astrophysical expectations. This consideration allows us to probe previously unexplored regions of the parameter space of dark matter-electron interactions. We further model the cosmic-ray electron distribution by numerically solving a diffusion equation along the jet and find that efficient dark matter-electron interactions can induce a flattening of the spectral index at different distances from the central supermassive black hole, in better alignment with radio observations from M87.

    hep-phastro-ph.COastro-ph.HE4 citations
21. 21*

    Gravity and the Hierarchy Problem

    Thede de Boer🇩🇪 · Jisuke Kubo🇩🇪 · Manfred Lindner🇩🇪 · Markus Reinig🇩🇪

    We propose a mechanism where the dynamical generation of the Planck mass in scale invariant gravity leads to Einstein gravity, successful inflation and an explanation of the hierarchy problem of the Standard Model. We will discuss the scale generation by dynamical symmetry breaking and phenomenological consequences.

    hep-phastro-ph.COgr-qchep-th2 citations
22. 22*

    Universality of the chiral soliton lattice and its interaction with quark matter

    Fabrizio Canfora🇨🇱 · Nicolás Grandi🇦🇷 · Marcela Lagos🇨🇱 · Luis Urrutia-Reyes🇨🇱 · Aldo Vera🇨🇱

    In this paper, we show that the chiral soliton lattice (ChSL) is, in a precise sense, a universal feature of the low-energy limit of QCD minimally coupled to Maxwell theory. Here, we disclose that not only can the ChSL be obtained from the gauged Skyrme model in $3+1$ dimensions, including the back-reaction of the Maxwell $U(1)$ gauge field, we also demonstrate that the ChSL remains unchanged when higher-order terms arising from QCD, specifically the sub-leading corrections in the 't Hooft large $N_c$ expansion, are included. By considering a suitable ansatz adapted to describe topological solitons at finite baryon density in a constant magnetic field, the generalized Skyrme model coupled to the Maxwell theory is reduced to the effective Lagrangian of the ChSL phase, which describes a lattice of domain walls made of hadrons. One of the key points in this construction is the fact that even when the usual topological charge density vanishes, the presence of the Callan-Witten term in the topological charge density allows for a non-vanishing baryon number. In the present approach, the magnetic field can be external, as is usually assumed for the ChSL, or it can be self-consistently generated by the hadronic layers themselves. Finally, we show how our formulation allows us to study the coupling of the ChSL with quark matter. In particular, we derive the exact analytical spectrum of the Dirac equation in the high-density limit, providing a microscopic characterization of the fermionic excitations within the inhomogeneous hadronic background provided by the ChSL. The comparison of the present spectrum of the Dirac operator within the ChSL with the spectrum of the usual Dirac operator in a constant magnetic field discloses the fundamental role of both the quark-Skyrmion coupling and the hadronic profile in opening a gap and generating a shift in the spectrum itself.

    ↳ hep-thhep-phnucl-th3 citations
23. 23*

    Causal Bounds on EFTs with anomalies with a Pseudoscalar, Photons, and Gravitons

    Ziyu Dong🇮🇹 · Jaehoon Jeong🇰🇷 · Alex Pomarol🇪🇸

    Theories with pseudoscalars that couple through anomalies (such as axion models) are of particular phenomenological interest. We carry out a comprehensive analysis of all bounds obtainable from bootstrapping the amplitudes when a pseudoscalar couples to photons and gravitons. This allows us to find new cutoff scales of theories with anomalies that are more restrictive than those obtained from naive perturbative analysis. Our results are especially relevant for holographic models, as the bounds determine the allowed region of the five-dimensional EFTs, for example, by imposing strong bounds on Chern-Simons terms. We also consider modifications of General Relativity in photon--graviton couplings and show that current experiments are sensitive to these effects only if new physics appears at $\sim 10^{-10}$ eV.

    ↳ hep-thhep-phJHEP(2026)·13 citations
24. 24*

    Importance of being nonminimally coupled: Scalar Hawking radiation from regular black holes

    Marco Calzà🇮🇹 · Massimiliano Rinaldi🇮🇹 · Sunny Vagnozzi🇮🇹

    In curved space-time, a scalar field $\varphi$ is generically expected to couple to curvature, via a coupling of the form $\xi {\varphi }^{2}R$. Yet in the study of Hawking emission from regular black holes (RBHs), where scalar fields are often introduced as simple probes of the geometry, and the Ricci scalar is generically non-zero, this non-minimal coupling is almost always ignored. We revisit this assumption by studying scalar Hawking emission from four representative RBHs (the Bardeen, Hayward, Simpson-Visser, and D'Ambrosio-Rovelli space-times), within two benchmark cases: the conformal case $\xi =1/6$, and a large negative value $\xi =-10^4$ motivated by Higgs inflation. We compute the graybody factors and emission spectra, showing that the latter can be either enhanced or suppressed, even by several orders of magnitude. A crucial role is played by the sign of the term $\xi fR$, with $f(r)=-g_{tt}$ in Schwarzschild-like coordinates, as it determines whether the non-minimal coupling suppresses or enhances the geometric potential barrier. For the D'Ambrosio-Rovelli case with large negative $\xi$, the low-energy emission spectrum is enhanced by up to five orders of magnitude, since $\xi fR<0$ throughout the space-time, leading to a deep potential well which broadens the transmissive window. The deviations we find can be particularly relevant in the case where primordial RBHs are dark matter candidates, given the impact of the non-minimal coupling on their evaporation history.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2025)·26 citations
25. 25*

    Transport properties of stochastic fluids

    Chandrodoy Chattopadhyay🇺🇸 · Josh Ott🇺🇸 · Thomas Schaefer🇺🇸 · Vladimir V. Skokov🇺🇸

    We study heat conduction and momentum transport in the context of stochastic fluid dynamics. We consider a fluid described by model H in the classification of Hohenberg and Halperin. We study both non-critical and critical fluids, and we investigate transport properties in two as well as three dimensions. Our results are based on numerical simulations of model H using a Metropolis algorithm, and we employ Kubo relations to extract transport coefficients. We observe the expected logarithmic divergence of the shear viscosity in a two-dimensional non-critical fluid. At a critical point, we find that the transport coefficients exhibit power-law scaling with the system size $L$. The strongest divergence is seen for the thermal conductivity $\kappa$ in two dimensions. We find $\kappa \sim L^{x_{\kappa }}$ with $x_{\kappa }=1.6\pm 0.1$. The divergence is weaker in three dimensions, $x_{\kappa }=1.25\pm 0.3$, and the scaling exponent for the shear viscosity, $x_{\eta }$, is significantly smaller than $x_{\kappa }$ in both two and three dimensions.

    ↳ nucl-thcond-mat.quant-gashep-phPRD(2025)·3 citations
26. 26*

    Alleviating the $H_0$ tension through the interacting dark energy model from quantum gravitational field theory in light of DESI DR2

    Yi-Min Zhang🇺🇸 · Tian-Nuo Li🇺🇸 · Guo-Hong Du🇺🇸 · Sheng-Han Zhou🇺🇸 · Li-Yang Gao🇨🇳 · Jing-Fei Zhang🇺🇸 · Xin Zhang🇺🇸

    Recent DESI DR2 data has shown a significant preference for dynamical dark energy, yet this has further exacerbated the $H_0$ tension. In this work, we explore the potential of interacting dark energy models ($\tilde{\Lambda }$CDM and $e\tilde{\Lambda }$CDM) within the asymptotic-safety framework of quantum gravitational field theory to alleviate the $H_0$ tension. We perform observational constraints using the latest baryon acoustic oscillation data from DESI DR2, cosmic microwave background (CMB) data from Planck and ACT, and type Ia supernova data from DESY5 and PantheonPlus, as well as the SH0ES data. From our analysis, we observe the dynamical scale parameter of the cosmological constant, ${\delta }_{\Lambda }=-0.270\pm 0.100$, in the $e\tilde{\Lambda }$CDM model using the CMB+DESI+SH0ES data, which deviates from $\Lambda$CDM at the $2.7\sigma$ level. Simultaneously, we find $H_0=70.84\pm 0.74\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$, reducing the $H_0$ tension to $1.7\sigma$. This increase in the inferred $H_0$ is due to the anti-correlation between ${\delta }_{\Lambda }$ and $H_0$, whereby a negative ${\delta }_{\Lambda }$ leads to a higher $H_0$ value. Furthermore, for the CMB+DESI+SH0ES combination, we obtain $\Delta {\chi }_{\min }^2=-14.14$ and $\Delta \mathrm{DIC}=-9.18$, favoring the $e\tilde{\Lambda }$CDM model over $\Lambda$CDM. Overall, the $e\tilde{\Lambda }$CDM model can improve the fit and ease the $H_0$ tension, especially for the data combinations that provide the strongest statistical support.

    ↳ astro-ph.COgr-qchep-phhep-th46 citations
27. 27*

    GEFF: The Gradient Expansion Formalism Factory - A tool for inflationary gauge-field production

    Richard von Eckardstein🇩🇪

    The GEFF - the Gradient Expansion Formalism Factory - is a new Python package designed to study gauge-field production during inflation. The package provides a framework to implement and use the gradient expansion formalism (GEF), a numerical technique devised to study the nonlinear dynamics associated with inflationary gauge-field generation. The GEF has already been applied in the context of axion inflation, and with the GEFF package, one can build on these results. The GEFF gives users access to ready-to-use model files for two scenarios of axion inflation: pure axion inflation, with the inflaton coupled to a pure Abelian gauge sector, and fermionic axion inflation, which assumes that the Standard Model (SM) hypercharge field is coupled to the inflaton, resulting in the production SM fermions via the Schwinger effect. The GEFF provides the user with methods to solve GEF equations, including an integrated error estimator and self-correction algorithm. Furthermore, users can implement their own GEF models, e.g., variations of axion inflation or related scenarios. The package also comes with tools to study the production of primordial gravitational waves induced by gauge fields. This is a starting guide for the GEFF, providing a high-level introduction to the GEF, installation instructions, and the basics for using this package.

    ↳ astro-ph.COgr-qchep-ph4 citations
28. 28*

    On the maximum compactness of neutron stars

    Luciano Rezzolla🇩🇪 · Christian Ecker🇩🇪

    The stellar compactness, that is, the dimensionless ratio between the mass and radius of a compact star, $\mathcal{C}:=M/R$, plays a fundamental role in characterising the gravitational and nuclear-physics aspects of neutron stars. Yet, because the compactness depends sensitively on the unknown equation of state (EOS) of nuclear matter, the simple question: ``how compact can a neutron star be?'' remains unanswered. To address this question, we adopt a statistical approach and consider a large number of parameterised EOSs that satisfy all known constraints from nuclear theory, perturbative Quantum Chromodynamics (QCD), and astrophysical observations. Next, we conjecture that, for any given EOS, the maximum compactness is attained by the star with the maximum mass of the sequence of nonrotating configurations. While we can prove this conjecture for a rather large class of solutions, its general proof is still lacking. However, the evidence from all of the EOSs considered strongly indicates that it is true in general. Exploiting the conjecture, we can concentrate on the compactness of the maximum-mass stars and show that an upper limit appears for the maximum compactness and is given by ${\mathcal{C}}_{\max }=1/3$. Importantly, this upper limit is essentially independent of the stellar mass and a direct consequence of perturbative-QCD constraints.

    ↳ gr-qcastro-ph.HEhep-phnucl-thSciPost Phys.(2026)·11 citations
29. 29*

    The String Theory Photoverse

    Thibaut Coudarchet🇩🇪 · Arthur Hebecker🇩🇪 · Joerg Jaeckel🇩🇪 · Jonathan Steiner🇩🇪

    String theory compactifications come with numerous $U(1)$ factors, implying the presence of many hidden photons in the low-energy EFT. One may call this the ``string photoverse''. We argue that, generically, these hidden photons are massless and do not couple to any light dark current such that, naively, kinetic mixing with the Standard Model is unobservable. The leading interactions of these ``superhidden'' photons are then dimension-6 dipole operators which couple them to quarks or leptons and the Higgs field. This induces magnetic and electric dipole moments with respect to both the superhidden photons as well as, through kinetic mixing, to the Standard Model photon. We derive these couplings by dimensionally reducing the fermionic action of 7-branes realizing the Standard Model: In the first step to 6d theories on intersection curves and then, in the presence of fluxes, to our 4d chiral EFT. We analyze how experiments and observations can employ this effect to place lower bounds on the string scale, which is relevant for compactifications with very large volumes. Finally, we briefly discuss how supersymmetry implies the presence of relatively light photinos and hence an accompanying ``photinoverse'', which may be observed via renormalizable mixing effects.

    ↳ hep-thhep-phJHEP(2026)·5 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.