Papers

Recent observations by IceCube and KM3Net of PeV-scale ultra-high-energy (UHE) neutrinos, together with detections of TeV-PeV photons from various sources such as the Crab Nebula, the Galactic Center, and gamma-ray burst by ground-based observatories including Tibet AS$\gamma$, MAGIC, Carpet-3, and LHAASO, point to the existence of extreme astrophysical environments capable of accelerating particles to ultra-high energies. These findings motivate investigations of possible connections between UHE neutrinos and photons in such environments. Theoretically, dense regions surrounding compact objects can efficiently produce UHE neutrinos. In this work, we calculate the production of UHE photons from neutrino-nucleon interactions, and note that if these interactions occur in the outer, optically thin regions of dense environments, the resulting photons could potentially be observed. In our model, an incident neutrino scatters off a nucleon, generating secondary partons that hadronize into pions and subsequently decay into UHE photons. We calculate the resulting photon energy spectra and find that for incident (anti)neutrinos with energies above 1 PeV, the probability of producing photons with energies exceeding 1 TeV is greater than 13%. As a concrete application, we show that this mechanism can quantitatively account for the preburst TeV photons observed in GRB 221009A, providing a natural explanation for both their energies and lead times. These findings establish a plausible mechanism linking UHE neutrino events to gamma-ray observations, providing new insights into hadronic processes in extreme astrophysical environments and supporting multi-messenger astronomy studies.

Quantum algorithms for simulating quantum chromodynamics (QCD) have matured steadily since the pioneering work of Byrnes and Yamamoto [PRA 73, 022328 (2006)]. The most popular strategies for Hamiltonian simulation involve product-formula decompositions. However, the application of product-formula methods to SU($N_c$) lattice gauge theories by Byrnes and Yamamoto leads to $O(\Lambda^{8(N_c^2-1)})$ gate complexity per Trotter step, where $\Lambda$ is the bosonic cutoff in the electric (i.e., irreducible-representation) basis. A seminal work by Kan and Nam [arXiv:2107.12769 (2021)] significantly improves over such an undesirable cost and reports an $O\big(\Lambda \text{polylog}(\Lambda)\big)$ scaling, yet it still calls for an unrealistically large number of quantum gates. Here, we illuminate one of the reasons behind this high cost estimate and show that a factor of size $O(2^{4(N_c^2-1)})$ can be removed from the per-Trotter-step cost estimate by Kan and Nam. We specifically show that, by using methods developed in our past works [PRD 112, 014508 (2025); Quantum 7, 1213 (2023)], exponentiated-Hamiltonian decomposition—a necessary step in the application of product-formula algorithms—can be performed far more efficiently than previously thought. Our method reduces the T-gate cost estimate of QCD simulations using a second-order product formula by a factor of nearly $10^{14}$, independent of simulation parameters and sizes. Focusing on simulations in the electric basis, we further contrast our results with other methods: the local-multiplet basis approach of Ciavarella, Klco, and Savage [PRD 103, 094501 (2021)] and the near-optimal algorithm of Rhodes, Kreshchuk, and Pathak [PRX Quantum 5, 040347 (2024)]. This work highlights the importance of continued algorithmic improvement to bringing the quantum-simulation cost of QCD within reach of realistic quantum computers.

The experimental observation of large CP violation in charm-meson hadronic decays remains theoretically unexplained within the Standard Model. The data-driven approach which accounts for the rescattering between the final-state pion and kaon pairs provides predictions that fall short of the experimental values. However, it relies on a set of inputs that exhibit large uncertainties. In this work, we make optimal use of the available information on branching ratios and of only one strong-scattering input parameter that is well determined. We find that it remains unlikely to explain the experimental signal within this approach and obtain predictions for sum rules that constrain CP asymmetries of the pion and kaon channels.

We investigate the impact of high-energy QCD resummation on Higgs-boson production processes relevant for Higgs-pair studies at the Large Hadron Collider. We present the first dedicated study of Higgs boson production in association with a bottom-quark pair and two additional hard jets in the gluon-fusion channel at high energies as a background to vector-boson-fusion Higgs-pair production. The resummation can significantly modify the QCD contribution in VBF-like regions of phase space, indicating that fixed-order calculations overestimate the contamination from gluon-fusion backgrounds. We then extend existing High Energy Jets (HEJ) predictions for Higgs boson production in association with jets by including quark-pair resummation effects for the first time.

The electron Parton Distribution Functions (PDFs) are essential components in the calculations of cross sections within a collinear-factorisation framework at lepton colliders. We compute them at the next-to-next-to-leading order (NNLO) in QED by working in two different factorisation schemes, namely the standard $\overline{\rm MS}$ one and the so-called $\Delta$ scheme, which was originally defined at the next-to-leading order, and which we generalise in this work by extending its definition to all orders. We present analytical results relevant to the large-$z$ behaviour of the PDFs in both factorisation schemes, and thus show how the soft-logarithm enhancement of the $\overline{\rm MS}$ electron PDF is completely absent in the $\Delta$ scheme. The latter therefore constitutes a natural choice that helps significantly reduce the complexity not only of numerical simulations in phenomenological applications, but also that of analytical computations necessary to achieve the soft resummation of physical observables. We argue that NNLO PDFs are necessary to attain relative-precision targets of $10^{-4}$ or better, for colliders whose centre-of-mass energies are in the hundred-GeV range.

In a recent paper \cite{Chu:2026dhx}, the quantum stability of the fuzzy sphere was established at large but finite $N$, where a tadpole was also identified for the scaling fluctuation mode of the matrix geometry. Here we show that this tadpole generates a positive area-conjugate microscopic response, which in isolation energetically favors contraction of the fuzzy sphere. However, when the horizon is coupled to gravity, the tadpole requires the bulk geometry to adjust according to the junction condition of general relativity. Taking the exterior geometry to be Schwarzschild, we show that the junction condition requires a positive interior cosmological constant. Imposing a static, spherically symmetric, regular vacuum interior then selects pure de Sitter space. The matching further determines a soldering relation between the interior de Sitter time and the exterior Schwarzschild time, with a relative lapse growing as $C = O(N)$. We also propose a matrix realization of the de Sitter interior in which fuzzy-sphere representation sizes determine the angular geometry while condensates of off-diagonal link fields determine the emergent radial metric. This provides a concrete consistency test for spacetime emergence from the matrix degrees of freedom. Potential cosmological implications are discussed.

Heavy-flavor jets and their substructure provide a unique window into the role of quark mass on QCD radiation and its modification in nuclear matter. In this work, we investigate heavy-quark energy-energy correlators (EECs) that are explicitly sensitive to mass effects, focusing on angular distributions, energy flow, and the dead-cone effect. We demonstrate how the finite mass of charm and bottom quarks reshapes the intra-jet radiation pattern, leading to characteristic suppression at small angles and measurable deviations from massless jet expectations. Using effective field theory analysis, we extend the calculation of these observables to reactions with nuclei to show that medium-induced radiation competes with vacuum mass suppression, resulting in a nontrivial modification of jet substructure. Specifically, we identify regimes where EECs are dominated by the heavy quark mass, leading to qualitatively and quantitatively different behavior of this observable in QCD matter. We discuss the charm and bottom jet energy-energy correlators modification in reactions with nuclei, and further demonstrate how the formalism can be tested in small collision system at current facilities.

We consider the R-parity violating Minimal Supersymmetric Standard Model (RPV-MSSM) with its wide range of signatures as a test model for the coverage of beyond the Standard Model searches at the LHC. Here we present a systematic study of the phenomenological and experimental status of specifically the R-parity violating $LQ\bar D$ operators, as the third study in the ABC of RPV series, following our previous analyses of the $LL\bar E$ and $\bar U\bar D\bar D$ operators. We classify the distinct collider signatures for all possible LSPs and for eight representative $LQ\bar D$ couplings, considering both direct LSP production and production through gauge cascades. Assuming one non-zero $LQ\bar D$ coupling at a time, we assess the current LHC coverage using ATLAS and CMS searches implemented in $\texttt{CheckMATE 2}$, and identify recent searches relevant for future recasting. We find substantial sensitivity to the colored sector, while gaps remain for wino- and higgsino-like LSPs for couplings involving $\tau$ leptons, when the LSP is the only sparticle within the LHC kinematic limit. Slepton LSPs remain unconstrained in their direct production at the LHC, although some sensitivity is found for slepton NLSPs with a bino-like LSP. These results highlight gaps in the $\texttt{CheckMATE 2}$ search database, as well as the need for targeted LHC searches for specific $LQ\bar D$ signatures.

The appearance of hyperons in the core of neutron stars generally softens the equation of state (EOS), posing a longstanding challenge to the existence of observed two-solar-mass compact stars. We investigate whether repulsive interactions mediated by a dark-sector vector portal can provide an additional source of high-density pressure and thereby modify the structure of hyperonic compact stars. The baryonic sector is described within the modified quark-meson coupling (MQMC) model, in which the octet baryons are treated as confined relativistic constituent-quark systems interacting self-consistently through the $\sigma$, $\omega$, and $\rho$ fields within a mean field approximation. The dark sector consists of a fermionic dark matter coupled to baryonic matter through a neutral vector mediator $Z^\prime$, generating an additional repulsive contribution to the dense-matter EOS. We investigate the resulting equation of state, mass–radius relation, tidal deformability, and moment of inertia. The resulting mass–radius relations satisfy the observational bounds from massive pulsars, including PSR J0740 + 6620, with maximum neutron star masses reaching approximately $2 M_{\odot}$. The resulting changes in tidal and rotational observables provide additional avenues for testing the dark-sector interaction through multimessenger observations.

A common approach to studying the multiquark states is to solve the few-body Schrödinger equation within a quark potential model. The multiquark states may contain quarks with several different flavors and have richer color structures than ordinary hadrons. The reliability of such an investigation requires that the underlying quark potential model can simultaneously describe the meson and baryon spectra across all flavor sectors, including orbital and radial excitations, with a single parameter set. At present, no quark potential model fully satisfies this requirement. We construct a simple nonrelativistic constituent quark potential model that includes spin–orbit and tensor interactions. We refit the model parameters to the latest experimental data. The excited light hadrons and several exotic hadron candidates are excluded from the fit. The resulting parameter set reproduces the spectra across all fitted sectors. The vast majority of deviations are below 20 MeV, while the largest deviations remain of the order of several tens of MeV, which is the typical accuracy of nonrelativistic quark potential models. Using the same parameters, we predict the spectra and internal structures of the orbitally and radially excited heavy baryons, which await further experimental determination. The excited light baryons are calculated with the same parameters. The calculated excited light baryon spectra deviate substantially from experimental values. Our refitted model does not resolve these longstanding discrepancies. The results delimit the range of validity of the nonrelativistic constituent quark potential model. By treating mesons and baryons across all flavor sectors, including both orbital and radial excitations within a unified framework, the model provides a controlled starting point for few-body calculations of multiquark states. We also urge experimental searches for the predicted states.

The triangle singularity interpretation of the \replyhe{$a_1(1420)$} observed by the COMPASS Collaboration has been widely accepted. In this work, we investigate the triangle mechanism in the decay $B^0 \to D^- \pi^+ a_0(980)(\pi^0 \eta)$, where the $a_0(980)$ is treated as a dynamically generated state. The $\bar{K}^{*0}$-$K^+$-$K^-$ triangle loop originates from the decay $B^0 \to D^- K^+ \bar{K}^{*0}$, which has been observed by the Belle Collaboration, followed by the subsequent decay $\bar{K}^{*0} \to K^- \pi^+$. The triangle amplitude develops a pronounced peak around 1420 MeV, which is reflected in the invariant mass spectrum of the $\pi a_0(980)$ system. The differential decay width is calculated and exhibits a narrow peak around $980~\mathrm{MeV}$ in the $\pi^0 \eta$ invariant mass distribution. Furthermore, the invariant mass distribution of the $\pi^+ \pi^0 \eta$ system shows a clear peak around $1420~\mathrm{MeV}$, which further \replyhe{confirms} the triangle singularity explanation of the \replyhe{$a_1(1420)$}. We expect that the proposed $B^0$ decay mode could provide a potential platform for further exploring the triangle-singularity nature of the \replyhe{$a_1(1420)$} and could be tested in future experiments such as LHCb, BESIII, and Belle~II.

We study Nelson–Barr models with a discrete $Z_N$ symmetry that solve the strong CP problem through spontaneous CP violation, and show that they naturally predict a light axion-like particle (ALP) without introducing any additional ingredients. Unlike the QCD axion, this ALP is anomaly-free: its couplings to photons and gluons are highly suppressed, rendering it naturally long-lived. Instead, it couples to quarks through flavor-violating interactions whose structure is dictated by the CKM matrix. These interactions induce rare meson decays, providing a unique probe of the Nelson–Barr mechanism. We study the cosmological production of the ALP through both freeze-in and misalignment mechanisms. We show that the parameter space in which the observed relic abundance is explained by the freeze-in mechanism is subject to stringent constraints from precision flavor experiments and stellar cooling bounds from SN1987A, leaving only a small viable region that will be comprehensively tested by future structure-formation observations such as the Vera Rubin Observatory and next-generation X-ray missions like Athena, GECCO and THESEUS. In contrast, misalignment production remains a robust and viable mechanism for explaining the observed dark matter abundance over a broad region of parameter space. Our results demonstrate that precision flavor measurements, cosmological observations, and X-ray searches provide complementary probes of this anomaly-free ALP and, consequently, of the Nelson–Barr solution to the strong CP problem.

An introductory review is provided for those who are interested in exploring applications of qubits and other quantum excitations to the detection of dark matter (and any other physics beyond the Standard Model). Topics covered include the fundamental properties of qubits, the excitation mechanism of qubits due to the electric field induced by dark matter (with attention to the effects of the coherence of dark matter), the dynamics of coupled qubit-cavity systems modeled by the Jaynes-Cummings framework, and the influence of noise and decoherence (especially Markovian noise described by the Lindblad equation). In addition, the article introduces essential concepts in quantum sensing, including the operator-sum representation and positive operator-valued measures, the Cramér-Rao bound, the standard quantum limit and the Heisenberg limit, and the potential enhancement of sensitivity to dark matter achievable with entangled states. Throughout, these topics are discussed with particular emphasis on their application to the detection of wave-like dark matter.

The dielectric formalism for light dark matter–electron scattering in semiconductors has, to date, employed only the longitudinal dielectric function $\epsilon_L$, with the transverse response $\epsilon_T$ universally neglected on qualitative grounds. A complete derivation and quantitative evaluation of $\epsilon_T$ in this context has been lacking. We provide this derivation within the random phase approximation for a homogeneous electron gas. For silicon, we find that the transverse energy loss function is $4--6$ orders of magnitude below the longitudinal one in the bulk plasmon regime, providing the first rigorous justification for the conventional longitudinal approximation. The sizable transverse corrections appear for deposited energies $\omega\lesssim1\,\mathrm{eV}$, which lies below the energy required to reliably produce one electron-hole pair in silicon detectors. Our results provide a quantitative error assessment for existing longitudinal calculations and identify kinematic regimes where transverse corrections ought to be included for relativistic dark-matter interpretations.

The mass splitting between the doubly and singly charged members of the Higgs triplet of the type-II seesaw model is usually treated as a free parameter in the collider literature. Electroweak loops fix it to $767$ to $841$~MeV over the mass range considered here once the quartic coupling $\lambda_4$ is set to zero at the renormalization scale $\overline\mu = M_{H^{\pm\pm}}$. Moving that scale by a factor of two in either direction moves the loop value by $208$~MeV at $200$~GeV, falling to $42$~MeV at $1$~TeV. At the reference splitting of $852$~MeV, the transition $H^{\pm\pm} \to H^\pm W^{\pm(*)}$ takes $40\%$ ($7\%$) of the total width at the crossover triplet vacuum expectation value for a doubly charged Higgs mass of $200$~GeV ($500$~GeV). That splitting is also where the partonic counting of that rate fails. Evaluated from hadronic data, the counting overestimates the rate by a factor $1.46 \pm 0.05$ at a splitting of $852$~MeV and underestimates it by a factor $4.87 \pm 0.09$ at $200$~MeV. Whether the mixed same-sign topology survives is then a condition on $\lambda_4$. The same channel moves the two published exclusion boundaries in opposite directions, by $-1.4\%$ and $+24.5\%$, at the level of branching ratios and at fixed experimental acceptance.

Many scientific discovery problems require searching combinatorial hypothesis spaces under complex domain constraints. Reinforcement learning (RL) offers a promising approach, but existing methods rely on scalar rewards that provide limited information about why candidate solutions fail, leading agents to repeatedly explore invalid regions. We introduce Certification-Driven Reinforcement Learning (CDRL), a framework that leverages structured feedback from symbolic reasoning tools. When a candidate violates domain constraints, these tools produce certificates identifying the actions responsible for failure. CDRL converts these certificates into reusable constraints that eliminate classes of invalid solutions and guide exploration toward valid regions. We evaluate CDRL on neutrino flavor model discovery in theoretical particle physics, where the hypothesis space exceeds $10^{26}$ possible models, and compare it with the state-of-the-art RL approach previously used for this task. Across three theory spaces, CDRL achieves up to 1.95$\times$ higher valid model rates and up to 6.33$\times$ higher neutrino model rates while evaluating up to 4$\times$ fewer candidates. We further extract 40 interpretable rules from search trajectories using a post-hoc decision-tree framework and show that reusing them as soft constraints yields gains of up to 2$\times$ in valid model rates and 3$\times$ in neutrino model discovery across all three theory spaces. These results suggest that CDRL uncovers reusable structure in combinatorial search spaces and provides a general framework for scientific model discovery.

We consider a relativistic hydrogen-like model for meson mass spectra. The model is based on a Lagrangian with a new general Yang-Mills symmetry. The strong interactions involve a fourth-order field equation that generates a linear confining potential. Notably, this model for meson masses requires quarks to carry only a single `confining charge' $f_c$ rather than three color charges. We classify meson mass spectra into sub-spectra defined by isospin, G-parity, total angular momentum and parity. By applying a numerical solver to the Dirac Hamiltonians–incorporating two short-range confining potentials, we obtain energy eigenvalues in natural units. The model has three coupling constants and one parameter. It provides a robust fit of 31 pions and kaons masses (from $\approx 140 MeV$ to $\approx 2,300 MeV$) to within $\approx 18\%$ of relative percentage error. The model suggests that the confining charge $f_c$=0.045/MeV = 8.87 fm plays the role of the basic length in the quark interactions.

We realize the double seesaw mechanism within a non-holomorphic modular $A_4$ framework by extending the Standard Model with three generations of right-handed neutrinos (RHNs), three left-handed sterile neutrino fields, and an $A_4$-singlet scalar. The modular construction forbids a bare Majorana mass term for the RHNs and realizes the hierarchy required for the double seesaw, with RHN masses induced through the heavier sterile neutrino sector. A comprehensive scan of the modular parameter space yields viable normal ordering solutions consistent with current neutrino oscillation data. We further examine their testability at DUNE, T2HK, and JUNO. DUNE and T2HK strongly probe the atmospheric mixing parameters and constrain the allowed model space, while JUNO provides complementary precision sensitivity to the solar mixing angle and mass-squared splitting. The oscillation compatible points also determine the induced RHN spectrum and complex Yukawa textures relevant for thermal leptogenesis. For a representative unflavored benchmark in the strong-washout regime, numerical Boltzmann evolution including decays and inverse decays yields $Y_{\Delta B}\simeq8.11\times10^{-11}$, close to the observed baryon asymmetry. The allowed parameter space also admits an $N_1$-dominated two-flavor thermal leptogenesis realization with a hierarchical, non-resonant RHN spectrum. Our results establish the non-holomorphic modular $A_4$ double seesaw as a predictive framework linking low-energy neutrino phenomenology and thermal leptogenesis, with oscillation predictions directly testable at forthcoming precision neutrino experiments.

Can warped extra dimensions first appear at the intensity frontier rather than as TeV-scale resonances at colliders? We explore this possibility in extended warped models in which gravity propagates to a deep infrared region with warped scale $\Lambda_{\rm IR}\sim \mathcal{O}({\rm MeV})$, producing a densely spaced Kaluza-Klein (KK) graviton tower. We develop a benchmark photon-portal realization in which a visible vector sector reaches an intermediate GeV-scale brane, while the Higgs sector remains associated with a higher warped scale. The resulting graviton-photon couplings are controlled by wave-function overlap in the extra dimension, so the production rate is not governed simply by an independent mass and coupling as in conventional light-mediator simplified models. Instead, GeV-scale photons in beam-dump environments can preferentially produce heavier KK gravitons whose profiles probe the intermediate brane, after which the excited modes cascade down the tower. If decays into radion-like states are kinematically closed for the terminal mode, the lightest accessible KK graviton can be long-lived and decay visibly into a pair of photons. This leads to a distinctive intensity-frontier signature: heavy-mode production, intratower showering, and macroscopic electromagnetic decays. We present the model ingredients, derive the relevant overlap-controlled couplings, characterize the generic production and decay phenomenology, and discuss the theoretical and precision constraints on this class of low-scale warped scenarios.

We construct a non-relativistic Lagrangian that describes muon-proton electroweak interactions. We determine the leading order coefficients by matching onto the theory with non-relativistic nucleons and relativistic leptons. The most impactful $\mathcal{O}(\alpha)$ corrections to those coefficients are determined by matching the non-relativistic amplitudes for capture of a free muon on a proton to the corresponding relativistic one. We use our non-relativistic effective field theory framework to calculate the capture rate in muonic hydrogen, thereby including radiative corrections of order $\alpha$ and up to order $1/m_\mu$. Using results for the Fermi coupling previously derived in EFT, we obtain singlet and triplet capture rates of $\Gamma({}^1 S_0) = 724.07 \pm 5.45~\rm{s}^{-1}$ and $\Gamma({}^3 S_1) = 11.55 \pm 0.18~\rm{s}^{-1}$, respectively.

We present the first search for ultraheavy dark matter using a magnetically levitated particle. The POLONAISE experiment uses a milligram-scale ferromagnet levitated in a superconducting trap, admitting a force sensitivity of $0.07\,\mathrm{fN\,Hz^{-1/2}}$ and resolving impulses as small as $1\,\mathrm{TeV}/c$. Treating every candidate impulse as a possible dark matter event, we set optimum-interval upper limits on the neutron coupling $\alpha_n$ for dark matter interacting through a new light mediator. For dark matter masses $10^6\,\mathrm{GeV}/c^2\text{-}10^{15}\,\mathrm{GeV}/c^2$ and mediators lighter than $30\,\mathrm{meV}/c^2$, we exclude couplings as low as $\alpha_n = 3.2\times 10^{-9}$ at $95\%$ confidence level and set leading constraints on the dark matter-neutron cross section for composite dark matter. Our results extend levitated sensing beyond the mass reach of optical levitation by seven orders of magnitude into the ultraheavy dark matter frontier.

We present a model-independent calculation of $\pi N$ forward dispersion relations and their analytic continuation to the complex plane, using a revised set of $\pi^\pm p$ total cross-section data up to 3 GeV, and Regge asymptotics above. Up to that energy, we find four stable poles for each isospin combination. The lightest pole in the $I=3/2$ channel corresponds to the $\Delta(1232)$ resonance, while the lightest in the $I=1/2$ channel corresponds to the Roper resonance, even though the latter is imperceptible in the data. We extract their pole parameters and the parameter difference between the $\Delta^0$ and $\Delta^{++}$, without relying on a partial-wave analysis. The remaining poles cannot be identified with a single resonance each. They are not artifacts but the combined effect of multiple resonances unresolved by total cross-section data alone. Finally, we write sum rules relating the residues of these constituent resonances to the residues of the poles extracted from the dispersive representation.

We study the one-point probability distribution function (PDF) for matter densities averaged with an arbitrary spherically symmetric window function. The PDF is analytically modeled within the path integral framework, enabling a non-perturbative description of large-scale structure. It contains a leading order contribution controlled by the spherically symmetric gravitational collapse dynamics, as well as an order-one factor arising from aspherical fluctuations. We develop a numerical pipeline to compute the leading spherical-collapse part of the PDF and apply it to a family of window functions interpolating between the TopHat and Gaussian filters in coordinate space, as well as to a window function with non-monotonic radial dependence. We find that the PDF weakly depends on the choice of the filter, provided the width of the filter is normalized to yield a fixed linear averaged density variance. For each filter and each value of the averaged density, our pipeline gives the most probable density profile. We find that these profiles vastly differ for different filters in the case of overdensities, but closely follow a universal curve at underdensities. We obtain a perturbative expression for the aspherical part of the PDF valid at small density contrasts. We find from it that all PDFs are equally sensitive to the effective field theory (EFT) corrections accounting for short-scale clustering, regardless of how smooth the filter's boundary is. We test our PDF model against the results of high-resolution N-body simulations. The agreement is excellent for filters with widths larger than 10 Mpc/h. Small discrepancies at a few percent level arise for narrower filters and are interpreted as higher-order perturbative corrections.

We study semiclassical tunneling in scalar field theories with slowly evolving homogeneous backgrounds. We formulate the problem by combining tadpole subtraction with an adiabatic expansion: the former maps the rolling system to an instantaneous multi-field tunneling problem, while the latter systematically tracks the slow evolution of the background. This formulation is particularly useful for tunneling during slow-roll inflation, where the tunneling direction may be transverse to the rolling inflaton direction. For a time-reflection-symmetric bounce on a fixed on-shell geometry, we show that the real tunneling exponent receives no direct correction linear in the rolling velocity. The tunneling rate nevertheless drifts along the rolling trajectory because the frozen tadpole-subtracted potential evolves. We also find that the exponent approaches a finite but nonanalytic limit as the tangential curvature vanishes, suggesting that a weakly tachyonic tangential direction can yield an exponent of the same order.

A tangle of line defects coarsens as the mean spacing $L$ between neighbouring lines grows. In a viscous medium the motion is overdamped, and the velocity-dependent one-scale (VOS) model predicts a late-time attractor $L^{2}=\mathcal{A}\,\ell_d\,t$, with $\ell_d=T/\Gamma$ the ratio of line tension to drag and $\mathcal{A}$ a dimensionless amplitude. The growth law $L\propto t^{1/2}$ holds for every value of the three model parameters—the momentum parameter $k\le1$, the sink coefficient $\tilde{c}$, and the curvature ratio $\lambda\equiv R/L$—since all three enter only through $\mathcal{A}=\kappa(\kappa+\tilde{c})$, $\kappa\equiv k/\lambda$. Thus, the exponent constrains none of them, and the amplitude is the only quantity a density history can deliver. We measure it from the disclination data of Chuang, Turok and Yurke on a nematic liquid crystal, whose companion measurement of loop collapse fixes $\ell_d$ on the same samples, canceling the 5CB material constants. Treating the unmatched per-quench $\ell_d$ as a nuisance parameter with a Gaussian prior and marginalizing it analytically, we obtain $\mathcal{A}=10.0^{+1.3}_{-1.1}$ from the three quenches in the $234~\mu$m cell; the fourth, the only one in the thinner $158~\mu$m cell, gives $\mathcal{A}=3.0^{+0.8}_{-0.6}$ and is fitted separately. Converting either into $\tilde{c}$ requires $\lambda$, which these data do not determine, so the result is a curve, $\tilde{c}(\lambda)=\mathcal{A}\lambda/k-k/\lambda$, not a number. At $\lambda=1$ with $k\le1$ they give $\tilde{c}\ge9.0$ and $\tilde{c}\ge2.0$, against $\tilde{c}=0.23$–$0.57$ from relativistic $U(1)$ simulations, values reached only at $\lambda\simeq0.33$–$0.35$ and $0.62$–$0.68$. We know of no VOS calibration for a cosmological $\mathbb{Z}_2$ network, so we cannot attribute the excess to topology, and we list what a repeat experiment must measure.

In this manuscript, we analyze the contribution of fragmentation mechanisms to the inclusive hadroproduction of heavy quarkonium pairs, taking into account both single- and double-hadron (dihadron) fragmentation channels. To estimate the contribution of the latter mechanism, we construct a microscopic perturbative model of the dihadron fragmentation function, which is valid in the limit of large invariant masses of the heavy quarkonium pair. Using the Color Glass Condensate framework to evaluate the $Q\bar{Q}$ production amplitude, we find that in LHC kinematics, the single fragmentation of heavy quarks into quarkonium is only a minor correction, whereas dihadron fragmentation can provide a sizable contribution, on par with the contributions of single- and double-parton scattering.

The choice of hydrodynamic frame directly influences the numerical values of transport coefficients in relativistic dissipative hydrodynamics. We derive the exact transformation between the Eckart and Landau–Lifshitz frames and show that their thermal conductivities are related by an enthalpy-dependent factor. Using a baryon-rich relativistic fluid described by a Boltzmann nucleon gas equation of state, we find that the Landau–Lifshitz thermal conductivity is suppressed relative to the Eckart conductivity, with the difference increasing with temperature and baryon chemical potential. A linearized analysis of sound propagation demonstrates that the sound attenuation coefficient remains identical in both frames, confirming the frame invariance of physical observables. Our results show that the frame dependence of transport coefficients reflects only the different decomposition of dissipative effects into heat-flow and diffusion currents, while the underlying transport physics remains unchanged. These findings underscore the importance of specifying the hydrodynamic frame when comparing transport coefficients from heavy-ion collisions, lattice QCD, and kinetic-theory calculations.

Semi-inclusive deep-inelastic scattering (SIDIS) of leptons is a vital tool for probing the three-dimensional momentum space partonic structure of the nucleon. Reliable extraction of the intrinsic collinear or transverse momentum dependent parton distributions from SIDIS data requires careful treatment of QED radiative effects beyond the Born level. In this work we perform a detailed comparative analysis of QED effects in SIDIS using the traditional Bardin-Shumeiko approach, augmented by the electron structure function method, and a more recent factorized approach that treats QED and QCD radiation on equal footing. We compare analytical and numerical results of these approaches for the unpolarized $\pi^+$ electroproduction cross sections off the proton and the Collins and Sivers transverse single-spin asymmetries, and identify the sources of discrepancies between the calculations, which for the cross sections can reach up to $\approx 2\%$, $\approx 7\%$, and $\approx 5\%$ at Jefferson Lab, HERMES, and EIC kinematics, respectively. To provide a unified approach for reliably extracting partonic information from future SIDIS measurements, we propose a hybrid framework that employs the salient features of both frameworks in their respective regions of applicability.

Warm inflation in $F(\Phi)R$ scalar-tensor theories of gravity is investigated in the `defining' frame, where the theory and its parameter values are specified. Translating the resulting dynamics to the Einstein frame, we find that the dissipation ratio is suppressed by the modified-gravity effects. Thus, although the effective warm-inflation dynamics can be consistently analysed in either frame, the dissipative regimes need not coincide between them. In particular, we find that quantum perturbations can dominate over thermal fluctuations in the scalar power spectrum even in a high-temperature, strong-dissipation regime in the defining frame. Finally, we compute the scalar spectral index and tensor-to-scalar ratio for a non-minimal coupling function $F(\Phi) = 1+\xi (\Phi/m_{\rm P})^2$ with a quartic potential and both constant and quadratic field-dependent dissipation coefficients, and identify benchmark points compatible with current CMB constraints.

This work presents a modern extraction of deeply virtual Compton scattering (DVCS) amplitudes off the proton and off the neutron through a global analysis of experimental data. These amplitudes serve as a crucial intermediate quantity linking generalized parton distributions (GPDs) to experimental observables. The analysis relies on a novel extraction framework recently integrated into the PARTONS software ecosystem. We employ two distinct modelling approaches for the DVCS amplitudes, both utilizing machine learning techniques: one model-agnostic and the other theory-augmented. For the first time, we incorporate the extraction of helicity-flip amplitudes, which are particularly sensitive to higher-twist effects. Furthermore, we compare our extracted amplitudes to timelike Compton scattering (TCS) data using the established relations between DVCS and TCS, serving as an important test of universality of GPDs. We also extract the DVCS subtraction constant, for which ab initio predictions from lattice QCD have been obtained. This allows us to confront these predictions with DVCS data for the first time, initiating a new virtuous cycle between first-principles theory and phenomenology.