HEP Phenomenology·hep-ph

Fri·Oct 9, 2026Friday·October 9, 2026

53 papers—30 primary·23 cross-listed

01
On the leptonic decays of the $τ$
Martin Hoferichter · Alberto Lusiani · Yannick Ulrich
In view of potential future improvements in the branching fractions of leptonic $τ$ decays $τ \to ℓ ν_{τ} ν ˉ_{ℓ}$ , $ℓ = e, μ$ , it is timely to derive the corresponding Standard-Model predictions beyond next-to-leading order. We provide such benchmark values for the fully inclusive decay widths, profiting from higher-order corrections that have been studied in the $MS$ scheme up to three-loop order in the case of muon decay. To obtain complete next-to-next-to-leading-order results, we perform a numerical calculation of the two-loop coefficients in the on-shell scheme, including an evaluation of the hadronic effects, and compare the leptonic results to the known $MS$ coefficients where available. Our final results are presented in the $MS$ scheme, to be able to also include an estimate of the three-loop contribution. In addition, we comment on radiative and rare decays, whose consideration is critical for the conversion between $MS$ and on-shell results.
hep-phhep-exnucl-th
02
Matter-Antimatter Asymmetry from Dirac-Majorana Flip-Flop
Debasish Borah · Arnab Dasgupta · Debalina Nandy · Indrajit Saha · Harman Singh
The observed matter-antimatter asymmetry can be generated dynamically via leptogenesis, where a non-zero lepton asymmetry is generated first and then gets converted into baryon asymmetry via sphalerons. Creation of non-zero lepton asymmetry typically requires lepton number violation (LNV) which, within the seesaw framework, results in the Majorana nature of light neutrinos. With no signs of LNV at terrestrial experiments, we propose a novel leptogenesis scenario where LNV occurs at high temperatures while zero-temperature physics is consistent with the pure Dirac nature of neutrinos. In a concrete model of this "Dirac-Majorana flip-flop", the right chiral parts of Dirac neutrinos initially acquire a large Majorana mass in the early Universe when a singlet scalar field with two units of lepton number acquires a non-zero vacuum expectation value (VEV), thereby facilitating leptogenesis from out-of-equilibrium decay of heavy Majorana fermions. At lower temperatures, the VEV of the scalar singlet gets restored to zero to be consistent with lepton number conservation. A first-order VEV-restoring phase transition can lead to observable gravitational waves, while light Dirac neutrinos can generate detectable dark radiation at cosmic microwave background experiments.
hep-phastro-ph.CO
03
Effective field theory for strong phase transitions
Oliver Gould · Farbod-Sayyed Rassouli · Paul M. Saffin
We show how to construct perturbative effective field theories for strong phase transitions, where the standard tools of high-temperature dimensional reduction fail. By identifying the relevant power counting relations for the couplings, masses and background fields, we construct a controlled perturbative expansion adapted to this regime. We find that the order parameter field remains light at the transition, so that there is a controlled derivative expansion, even though large external fields need to be resummed. The resulting effective field theories for strong phase transitions live in three dimensions and have nonpolynomial field dependence. Applying our framework to a two-scalar model, we verify renormalisation scale cancellation through next-to-next-to-leading order and find decreasing corrections to the latent heat as the perturbative order is increased. Extending to include fermions and gauge fields, we identify a broad class of models in which strong-transition thermodynamics are systematically improvable.
hep-ph
04
A Texture of Leptons for the Koide and Alikhanov relations
Alessandro Strumia
Koide and Alikhanov proposed intriguing empirical relations among charged-lepton masses and neutrino mass splittings, respectively. We present mass-matrix textures that realise these relations and can jointly account for the observed lepton mixing angles, while yielding predictive correlations among them and the neutrino CP phases.
hep-phhep-th
05
The Silence of the Dipoles: Accidental Symmetries in Lepton Flavor
Andrea Di Lecce · Majid Ekhterachian · Marko Pesut · Stefan Stelzl
Upcoming experiments are set to dramatically improve the search for charged lepton flavor violation, with the sensitivity to the rates of $μ \to eee$ decay and $μ N \to e N$ conversion expected to improve by four orders of magnitude in the near future. We study how these measurements reshape our understanding of fundamental interactions and their implications for the Higgs hierarchy problem. We consider the framework of Strongly Interacting Light Higgs with partial compositeness. In generic models of partial compositeness, the existing constraints from $μ \to e γ$ and the electric dipole moment (EDM) of the electron require the scale of Higgs compositeness to be above $\sim O (100)$ TeV. These mass scales lie beyond the direct reach of the LHC and envisioned future colliders and are comparable to, or higher than, those accessible to future $μ \to 3 e$ and $μ N \to e N$ searches. We show, however, that models where the strongly coupled sector has an accidental $U (3) \times CP$ or $U (2) \times U (1) \times CP$ symmetry, broken by the elementary--composite mixings, can substantially relax these constraints. In the $U (3)$ case, these symmetries (1) lead to an accidental alignment of the Yukawa and dipole couplings at leading order, suppressing $μ \to e γ$ and the electron EDM, allowing the compositeness scale to lie in the few-TeV range; (2) are probed by the upcoming $μ \to eee$ and $μ N \to e N$ experiments; and (3) provide a direct target for current and future collider experiments. In the $U (2) \times U (1)$ case, $μ \to e γ$ and the electron EDM remain important constraints, while upcoming searches for $μ \to eee$ , $μ N \to e N$ and flavor-violating $τ$ decays provide complementary probes. We discuss how these accidental symmetries can arise in the infrared compatibly with the dynamical generation of flavor hierarchies in the ultraviolet.
hep-phhep-ex
06
pyAmpliCol: fast tree-level matrix elements
Rikkert Frederix · Valentin Hirschi · Lucien Huber · Shahriar Iravanian · Ben Ruijl · Timea Vitos
Tree-level matrix elements sit at the heart of collider event generation, but their cost rises rapidly just where additional resolved radiation becomes most important. We present pyAmpliCol, a public generator aimed at extending the practical reach of colour-resolved matrix elements to higher multiplicities. It builds on the colour-ordered, off-shell-current strategy of AmpliCol, providing fast access to individual leading-colour flows while retaining the option of next-to-leading or exact full colour. The latter introduces its own high-multiplicity bottleneck: the dense interference of factorially many colour orderings. pyAmpliCol addresses this contraction with a fast Fourier transform on the symmetric group, preserving the exact colour result while avoiding the direct pairwise sum. Representative full-colour benchmarks demonstrate substantial speedups over the reference calculations considered here. It supports Standard Model processes and a broad class of UFO models, selected or summed helicities, vectorised evaluation and controllable numerical precision. It further provides colour- and spin-correlated Born quantities and tree-level colour connections at arbitrary perturbative order, opening the same framework to local subtraction and other higher-order applications. Together, these capabilities connect high-multiplicity matrix elements to their use in event generation, merging, parton showers and precision calculations within a single generator.
hep-phhep-th
07
Hot and dense QED at N $^{3}$ LO: infrared sector
Tyler Gorda · Swastik Majumder
We determine the infrared-sensitive contribution to the pressure of hot and dense massless quantum electrodynamics (QED) at $O (e^{6})$ in the electric charge $e$ , obtaining a representation valid across the crossover between the thermally dominated and degenerate regimes. This contribution arises from a hard-thermal-loop (HTL) resummed soft photon dressed by either the one-loop power correction or the two-loop next-to-leading-order photon self-energy. After separating the static and nonstatic sectors, we obtain the static contribution in closed form and perform the nonstatic Matsubara sum analytically in terms of the digamma function, reducing the remaining finite coefficient to a one-dimensional numerical integral. The finite-temperature HTL counterterm cancels the factorization divergence before expansion; at strictly zero temperature $T$ , this divergence instead cancels against the hard four-loop contribution. At vanishing chemical potential, the static sector reproduces the complete known $O (e^{5})$ pressure. Taking the cold limit of the dimensionally regulated, unsubtracted nonstatic contribution reproduces the correct cold mixed result. Crucially, at any fixed $T > 0$ , the nonstatic result remains analytic in $e^{2}$ . The zero-temperature $O (e^{6} ln e)$ term in QED arises only in the nonuniform limit $T / m_{E} \to 0$ where $m_{E}$ is the electric screening mass, demonstrating that the weak-coupling and zero-temperature limits do not commute.
hep-ph
08
The dipole ellipse from vector-like leptons at next-to-leading order
Kilian Möhling
We consider the SM extended by a 4th generation of vector-like leptons. This model generates strongly correlated contributions to the lepton masses, Higgs couplings and dipole moments. At leading order the Higgs coupling restricts the magnetic and electric dipole moments to an ellipse. Here we compute the one-loop corrections to the Higgs coupling and two-loop corrections to the dipole moments to obtain the correlation at next-to-leading order using the framework of SMEFT. In addition we resum the leading logarithmic corrections from SM couplings through the SMEFT renormalisation group equations. With these results we compute the RG improved correlation at NLO and discuss the implications for the muon, electron and tau correlations. Specifically, for the muon we find that the corrections contract the ellipse such that a larger part of parameter space becomes compatible with the updated SM value of the muon magnetic moment.
hep-ph
09
Probing CP violation in dark scalar decays at the SHiP experiment
Mayumi Aoki · Takashi Shimomura
We investigate CP violation in the decays of a GeV-scale dark scalar boson into mesons, muons and photons. Both scalar and pseudoscalar couplings to the SM fermions are considered to study how the CP structure of the dark scalar boson can be probed through its decays. The scalar and pseudoscalar interactions predominantly induce decays into two-meson and three-meson final states, respectively. We propose the simultaneous observation of these two classes of decay modes as a probe of CP violation in the dark scalar sector. The expected signal rates at the SHiP and FASER2 experiments are evaluated based on the dark scalar production from heavy-meson decays. We find that the ratio of three-meson to two-meson decay events at SHiP has the potential to probe a wide range of the CP-violating parameter space for dark scalar masses around the GeV scale. We also show that the two-muon and di-photon channels can provide complementary information for the CP violation search.
hep-ph
10
Systematic Uncertainties in Ultralight Boson Constraints from Superradiance
P.S. Aswathi · Ling Sun
Ultralight bosons are well-motivated candidates for physics beyond the Standard Model and may constitute part or all of the dark matter. Black-hole superradiance provides a powerful means of probing these particles through their gravitational interaction with rotating black holes. This mechanism has motivated a growing body of constraints from electromagnetic measurements of black-hole spins and, more recently, gravitational-wave observations. Gravitational-wave probes draw on several distinct signatures: the spins of merging binary black holes, gravitational radiation emitted by boson clouds, and potential imprints of cloud-induced changes to binary dynamics. The interpretation of these probes depends on method-specific astrophysical and theoretical assumptions, including black hole formation, natal spin, age, accretion history, population priors, and boson self-interactions. In this paper, we review the principal electromagnetic and gravitational-wave constraints derived from black-hole superradiance, with particular emphasis on their underlying assumptions and systematic uncertainties. The distinct observational signatures and systematic uncertainties of these approaches offer complementary perspectives on the viability of ultralight-boson models. In particular, their overlapping coverage around boson masses of $1 0^{- 13}$ - $1 0^{- 12}$ eV makes this region particularly informative for comparing constraints, with attention to the assumptions underlying each result.
hep-phastro-ph.HE
11
Quantum Magic and the Strong Coupling Constant
Qiaofeng Liu · Ian Low · Zhewei Yin
The three gauge couplings of the Standard Model (SM) can be parameterized as the fine structure constant $α$ , the weak mixing angle $sin^{2} θ_{w}$ , and the strong coupling $α_{s}$ . They are fundamental constants whose values remain unexplained. Previously we showed that minimizing magic production in charged-lepton scattering reproduces $sin^{2} θ_{w}$ with great precision. Here we study magic production in the six flavor-diagonal color-singlet channels $q q ˉ \to q q ˉ$ at tree level, including photon, gluon, $W / Z$ , and Higgs exchange. Varying only $α_{s}$ , with all other inputs fixed at each center-of-mass energy, we find that the finite- $α_{s}$ magic minimum in the top channel reproduces the $MS$ value of $α_{s}$ to within $5%$ from $1$ TeV to $1 0^{9}$ GeV. Higgs exchange involving the large top Yukawa coupling is essential for this agreement. All six channels produce near-minimal magic at the SM couplings, and reducing $α_{s}$ toward $α$ increases their magic production, potentially explaining why the strong interaction is ``strong.'' To understand why minimizing magic reproduces both $sin^{2} θ_{w}$ and $α_{s}$ , we conjecture that the parameters of fundamental interactions among color singlets reflect a principle of quantum computational efficiency, with the physical universe emerging from a quantum simulation subject to constrained resources.
hep-phhep-thnucl-thquant-ph
12
Analysis of p-Wave Sommerfeld Resonance Behavior in Finite-Size Dark Matter
Wu-Long Xu · Jin Min Yang · Rui Zhu
Different stages of cosmic evolution impose different requirements on the dark matter annihilation cross section. Sommerfeld enhancement provides a possible way to accommodate them. However, in the point-like dark matter scenario, satisfying these requirements with either $s$ -wave or $p$ -wave Sommerfeld enhancement can strongly constrain the dark matter and mediator masses and their coupling. A finite dark matter size introduces an additional parameter and may relax these constraints. Motivated by this possibility, in this work we study the $p$ -wave Sommerfeld resonances of finite-size dark matter (like proton or neutron) without specifying its internal structure. We find that the $p$ -wave contribution can exceed the $s$ -wave contribution. Nevertheless, the finite-size $p$ -wave resonances are weaker than those in the point-like case. Despite this suppression, their velocity dependence remains similar to that of point-like dark matter. We then extend our analysis to nugget dark matter composed of a small number of constituents. In this case, the $p$ -wave Sommerfeld enhancement exhibits behavior similar to that of point-like dark matter.
hep-phastro-ph.HEhep-th
13
Implications of tachyonic phase transition in classically scale invariant general $U (1)_{X}$ models
Arindam Das · Katsuya Hashino · Yuta Orikasa · Masanori Tanaka
We investigate the complementarity between collider searches and gravitational-wave (GW) observations in the classically scale-invariant general $U (1)_{X}$ extension of the Standard Model. The $U (1)_{X}$ scale is generated radiatively through the Coleman-Weinberg mechanism, while the electroweak scale is induced through the Higgs portal, without explicit mass terms in the scalar potential. Three right-handed neutrinos are introduced to ensure anomaly cancellation and acquire Majorana masses upon $U (1)_{X}$ symmetry breaking, which also generates the mass of the neutral gauge boson $Z^{'}$ . In the strongly supercooled regime, a tachyonic $U (1)_{X}$ phase transition can produce a stochastic GW background. Assuming three heavy Majorana neutrinos, we study their effects on the phase-transition dynamics and reheating, and estimate the resulting GW signals. We identify the regions of the $U (1)_{X}$ gauge coupling and $Z^{'}$ mass accessible to future GW observatories, including LISA and DECIGO, and compare them with existing LEP and LHC constraints. We find that GWs from tachyonic phase transitions can probe regions with small gauge couplings and heavy $Z^{'}$ bosons that are difficult to access through collider searches, demonstrating the complementarity of these probes.
hep-phastro-ph.CO
14
Quantifying TMD factorization breaking at tree level
Jian Zhou
Rogers and Mulders identified color entanglement as a mechanism that breaks transverse-momentum-dependent (TMD) factorization in nearly back-to-back dijet production. Using the double-Sivers asymmetry in their model, we quantify the contribution of color entanglement in the intermediate region $Λ_{QCD} ≪ q_{T} ≪ P_{T}$ , where $q_{T}$ is the transverse-momentum imbalance of the dijet and $P_{T}$ is the hard transverse momentum. We compare the collinear twist-three result with the TMD-factorization prediction, expressing both in terms of the Qiu--Sterman functions. In the absence of color entanglement, the factorized prediction would involve the Sivers functions of semi-inclusive deep-inelastic scattering (SIDIS). Diagrams without crossed attachments reproduce the hard coefficient obtained from the perturbative tails of these Sivers functions. Crossed diagrams, in which each coherent gluon attaches to the other hadron's quark line, contribute an extra term equal to $4/ (N_{c}^{2} - 1)$ times this coefficient.
hep-ph
15
Thermal photon production rate from QGP at finite density: Analytic cutoff independence
Sourav Duari · Nilanjan Chaudhuri · Sourav Sarkar · Pradip Roy
We compute the thermal photon production rate from a hot and dense quark-gluon plasma. While the mutual cancellation of the intermediate momentum cutoff $k_{c}$ between the hard and soft regimes in the presence of finite baryon density has been previously established only numerically, we demonstrate here, for the first time, that this cutoff independence can be shown analytically even in the presence of a nonzero quark chemical potential $μ$ . This resolves a long-standing issue addressed in Ref.[1]. The final expression for the photon rate can be treated as a generalization of the results obtained in Refs.[2,3] in the presence of $μ$ and can be implemented directly in the space-time evolution of a hot and dense QGP medium using relativistic hydrodynamics.
hep-ph
16
Photon evolution through light-particle conversion in stochastic magnetic fields: Kramers--Kronig relations and universality
Wataru Chiba · Ryusuke Jinno · Kimihiro Nomura
We study photon conversion into light particles, such as dilatons, axions, and gravitons, induced by background magnetic fields, and formulate the resulting evolution in terms of the Stokes parameters. We show that photon conversion reduces to an effective non-unitary evolution of the photon sector. In the perturbative regime, the Hermitian and anti-Hermitian parts of the effective photon Hamiltonian are related through Kramers--Kronig relations, revealing that the changes in the Stokes parameters are not independent. We apply this general framework to photon evolution in Gaussian stochastic magnetic fields with possible helicity, and derive the ensemble-averaged evolution of the Stokes parameters. We find that two nonzero contributions arise even in the absence of magnetic helicity, which respectively correspond to the overall attenuation of all the Stokes parameters and to an irrelevant overall phase. We also find that magnetic helicity gives rise to two additional contributions, one of which changes the circular polarization while the other induces a rotation of linear polarization. These contributions form two Kramers--Kronig pairs. In particular, photon conversion induced by magnetic helicity is accompanied by both circular-polarization and birefringent responses. The same structure appears in dilaton-photon, axion-photon, and graviton-photon systems, revealing universality of photon conversion in magnetic fields.
hep-phgr-qchep-th
17
Selected open-charm decays of the narrow $P_c$ states: Quark-interchange predictions and pion-exchange sensitivity
Vandan Patel · Ajay Kumar Rai
The proximity of the narrow $P_{c} (4312)$ , $P_{c} (4440)$ , and $P_{c} (4457)$ structures to the $Σ_{c} D ˉ^{(*)}$ thresholds motivates their interpretation as hadronic molecules. We treat the $P_{c} (4312)$ as an $S$ -wave $Σ_{c} D ˉ$ state with $J^{P} = 1/ 2^{-}$ and examine both $J^{P} = 1/ 2^{-}$ and $3/ 2^{-}$ $Σ_{c} D ˉ^{*}$ assignments for each heavier peak. The selected $S$ -wave open-charm transitions to $Λ_{c} D ˉ^{(*)}$ are calculated at Born order in the quark-interchange model, including the prior and post rearrangement diagrams and their color, flavor, spin, and spatial matrix elements. Across the input variations considered, the quark-interchange widths robustly favor $Λ_{c} D ˉ^{*}$ over $Λ_{c} D ˉ$ for every $J^{P} = 1/ 2^{-}$ assignment. At either heavier peak mass, the $Λ_{c} D ˉ^{*}$ width for $J^{P} = 3/ 2^{-}$ is suppressed by approximately one order of magnitude relative to $J^{P} = 1/ 2^{-}$ , providing a potential decay-based discriminator of the spin assignments. The large channel hierarchies arise from spatial overlaps and interference between spin-independent and hyperfine contributions and are not universal heavy-quark-spin-symmetry ratios. We also explore a retarded one-pion-exchange transition at first Born order. It affects $P_{c} (4312) \to Λ_{c} D ˉ^{*}$ most strongly, while the coherent widths remain sensitive to the cutoff, energy-transfer prescription, short-distance subtraction, and unresolved relative matching sign. The quark-interchange hierarchies are therefore the central predictions, whereas the pion-exchange results quantify matching sensitivity. Measurements of the $Λ_{c} D ˉ^{*}$ modes can directly test these patterns.
hep-ph
18
Flavour decomposition of the nucleon tensor multipole moments
U. Özdem
We compute the chiral-odd form factors $H_{T}$ , $E_{T}$ and $\hT$ of the nucleon in light-cone QCD sum rules, separately for the $u$ and $d$ quarks, and organise them into the tensor monopole, dipole and quadrupole moments $g_{T}$ , $κ_{T}$ and $Q_{T}$ . The quadrupole moment, with no chiral-even counterpart at leading twist, and the isoscalar channel, whose sum rules were derived but never evaluated, are new in this framework. The form factors are read from a Lorentz basis independent only after canonical ordering of the Dirac strings; three of the eight surviving structures give the three form factors separately, and the one usually used for the tensor charge is not among the eight. Two exact results follow analytically. The $d$ -quark contributions to $E_{T}$ and $\hT$ are equal and opposite in the chiral limit, broken in proportion to the quark mass and the twist-six amplitude $V_{6}$ , so the $d$ -quark sector carries a single independent function; and the isoscalar tensor charge receives no leading-twist contribution, its twist-three terms cancelling between the flavours. Neither is visible without resolving the flavours. At $μ^{2} = 1$ ~GeV $^{2}$ the two distribution-amplitude sets give $g_{T}^{u - d} = 1.27 (7)$ , $1.08 (6)$ , $κ_{T}^{u - d} = 1.35 (62)$ , $1.58 (59)$ , $Q_{T}^{u - d} = - 4.40 (83)$ , $- 4.20 (73)$ and $g_{T}^{u + d} = 0.39 (7)$ , $0.38 (6)$ , $κ_{T}^{u + d} = 4.47 (62)$ , $4.32 (59)$ , $Q_{T}^{u + d} = 2.41 (53)$ , $1.56 (30)$ . The mean-field relation $2 \hT^{u - d} = - E_{T}^{u - d}$ , tested without any large- $N_{c}$ assumption, holds in sign and order of magnitude, with ratio $0.64 (16)$ and $0.67 (15)$ against the predicted unity. In the impact-parameter plane the moments displace the two flavour distributions in opposite transverse directions by nearly equal amounts, $⟨ b_{y} ⟩ = 0.37$ and $- 0.37$ ~fm, and elongate both across the polarisation axis, the $d$ quark some five to six times more strongly
hep-phhep-exhep-latnucl-th
19
Minimally Modified Frampton--Glashow--Yanagida Ansatz and Its Leptogenesis Consequences: In Light of Recent JUNO's Result
Xing-Yu Wang · Zhen-hua Zhao
Motivated by the recent JUNO indication favoring normal neutrino mass ordering, we study two realizations of the minimally modified Frampton--Glashow--Yanagida (MMFGY) framework in the minimal type-I seesaw with two right-handed neutrinos. Both retain one exact Yukawa texture zero, supplemented by either a single physical CP-violating phase or a remnant CP symmetry. The explicit-CP realization yields twelve high-energy Yukawa configurations that reduce to three low-energy classes, with correlated CP phases and predictions for neutrinoless double-beta decay. In both realizations, a strongly suppressed second Yukawa entry can emerge, although the full-matrix hierarchy remains moderate in the quasi-degenerate regime. We analyze leptogenesis for a non-degenerate benchmark, quasi-degenerate TeV-scale right-handed neutrinos, and lower masses where coherent production, oscillations, and electroweak sphaleron freeze-out become important. Successful leptogenesis is obtained across a broad range of the scanned benchmarks, with increased sensitivity to the initial right-handed-neutrino abundance at the lowest mass scale. Requiring successful leptogenesis restricts the allowed phases while preserving the possibility of an approximate second zero. The two realizations exhibit distinct approximate-zero patterns and leptogenesis predictions, demonstrating how different restrictions on the high-energy Yukawa structure affect baryogenesis.
hep-ph
20
Searching for Charged Lepton Flavor Violation
Lorenzo Calibbi · Kaori Fuyuto · Matthias Heinz · Jure Zupan
Searches for Charged Lepton Flavor Violation (CLFV) are powerful tools to probe physics beyond the Standard Model (BSM). This chapter provides a comprehensive survey of CLFV theory, focusing primarily on low-energy muon and tau transitions while outlining complementary searches from high-energy colliders. Grounded in the Effective Field Theory (EFT) framework, we systematically review key observables including radiative and purely leptonic decays of muon and tau as well as $μ \to e$ conversion in nuclei and $τ$ hadronic decay channels. CLFV involving light new physics particles is also discussed. This review captures the modern synergy between EFTs, novel light-mediator scenarios, and hadronic and nuclear physics in the ongoing hunt for BSM signals.
hep-ph
21
Electromagnetic isospin breaking in hadronic vacuum polarization within a VMD model
Volodymyr Biloshytskyi
One of the challenging components of modern lattice-QCD computations of the leading hadronic vacuum polarization contribution to the muon $(g - 2)_{μ}$ is the isospin-breaking correction due to electromagnetism. Dominated by long distances, this correction suffers from severe signal-to-noise issues and finite-volume effects. To provide infinite-volume benchmarks for various quark-level Wick contractions, we estimate their sizes phenomenologically at the physical point, using a previously developed vector-meson-dominance model. The pion contributions in this model sum to around $- 7.1 \times 1 0^{- 10}$ , dominated by the electromagnetic pion mass shift. The ultraviolet-finite (2+2)a ("dumbbell") contraction accounts for approximately two thirds of this model sum; for both, about 30% comes from Euclidean times beyond 2.8 fm.
hep-phhep-lat
22
Warm-Inflation: a software for first-principles integration of warm inflation power spectra
Alica Rogelj
As part of a PhD thesis entitled `Scalar perturbations in warm inflation and during reheating' we present a software for computing warm inflation observables. In particular, our Mathematica implementation computes the power spectrum, spectral tilt, and tensor-to-scalar ratio for a given momentum scale. Compared with other implementations, we start in a Bunch-Davies state deep inside the horizon, ideally at a time when thermal noise is exponentially suppressed. We integrate gauge-invariant equations for three curvature perturbations across horizon exit. We continue deep enough outside of horizon so that all curvature perturbations agree. Results are illustrated for Standard Model embedded warm inflation, and we also provide notebooks for several other popular potentials and friction coefficients. The theoretical foundations for the code can be found in the main part of the thesis or in earlier papers [1,2]. Specifically, part II derives gauge-invariant, model-agnostic evolution equations, as well as the noise autocorrelator interpolating between quantum and classical domains. Part III presents the general ideas behind the numerical implementation, while part IV presents selected results. The code is described, line-by-line, in Appendix A. The published PhD thesis is available at https://doi.org/10.48620/101166 while the notebooks can be downloaded from https://github.com/alicarogeljblackhole/Warm-Inflation.
hep-ph
23
Reassessing the $X (2370)$ in $J / ψ \to γ K_{S}^{0} K_{S}^{0} π^{0}$ beyond the one-dimensional mass projections
Xiang-Kun Dong · Teng Ji · Meike Küßner · Ulf-G. Meißner
The BESIII Collaboration recently extracted the properties of the $X (2370)$ from a fit to the one-dimensional $K_{S}^{0} K_{S}^{0} π^{0}$ invariant-mass spectrum in $J / ψ \to γ K_{S}^{0} K_{S}^{0} π^{0}$ . The intermediate two-body structures visible in the mass correlations, including the $K_{0}^{*} (1430)$ bands, require a coherent treatment of cross-channel interference when interpreting the enhancement near 2.3 GeV. We reassess the need for an additional $X (2370)$ contribution by fitting the published data using an effective coupled-channel framework. The three-body parent amplitude is parameterized by a $K$ -matrix as the scattering among several quasi-two-body channels. The seven- and eight-bare-state models give similar mass distributions. Adding the eighth bare state lowers the Poisson deviance by 1.26% and produces an additional pole at $E = (2424 - i 149)$ MeV, substantially broader than the $X (2370)$ mass-width reference. This pole is model-dependent, and its identification with the $X (2370)$ is not clear. The present analysis does not establish the need for an additional $X (2370)$ contribution in $J / ψ \to γ K_{S}^{0} K_{S}^{0} π^{0}$ , thereby weakening the flavor-singlet argument based on the suppression of $K^{*} K ˉ$ relative to the total $K K ˉ π$ contribution. A more comprehensive experimental amplitude analysis, incorporating coherent interference, mass and angular correlations, and detector effects across related decay channels, is needed to establish the role and decay properties of the $X (2370)$ .
hep-phhep-exhep-lat
24
Constructing $S U (N)$ strongly coupled dark sectors by extending the Standard Model: mixed representations, flavor structure, global symmetries and various portals
Yi Chung
Motivated by the potential existence of a dark QCD sector, we construct a $S U (N)$ strongly coupled dark sector by extending the Standard Model (SM) gauge group to an enlarged $S U (N + 5) \times S U (N + 1) \times U (1)$ , under which the dark quark candidates naturally arises from the same multiplets as the SM fermions. The dark QCD sector from the extension inherits the rich structure of the SM, featuring three distinct properties: (1) Mixed representations: There are dark quarks of three different representations, including fundamental ( $χ_{f}$ ), antisymmetric ( $χ_{a}$ ), and symmetric ( $χ_{s}$ ), which can be traced back to the chiral structure of the SM. (2) Flavor: Each representation features three generations, with their flavor structures and Yukawa interactions directly related to those of the SM. (3) Global symmetries: Alongside the conventional dark baryon number $D$ , we identify an exotic dark baryon number $D$ from a conserved $(B - L) - D$ symmetry. These features provide novel perspectives on the structure of dark QCD sectors. Furthermore, the extension of the scalar and gauge sectors introduces various portals between the dark QCD sector and the SM sector. We systematically study these portals, including quark portal, lepton portal, Higgs and $Z$ portal, heavy $Z^{'}$ portal, kinetic mixing portal, dipole portal, and dark pion/axion portals. With a concrete UV model, their origin become robust, providing additional guidance for experimental searches of the dark sector.
hep-ph
25
Minimal-Length Corrections to Hyperon Polarization in Rotating Quark Gluon Plasma
Behnam Pourhassan · Sameer Ahmad Mir
Hyperon polarization in relativistic heavy-ion collisions sensitively probes thermal vorticity and the operator structure of local equilibrium. We investigate an isotropic generalized uncertainty principle (GUP) via a spin-independent scalar deformation of the one-particle phase-space density of states in the local rest frame (LRF). We employ the Belinfante-Rosenfeld local-equilibrium operator, the standard on-shell dispersion relation, and the Pauli-Lubanski/axial-Wigner representation of the spin- $1/2$ observable, retaining terms linear in the GUP coefficient and in hydrodynamic gradients. The same scalar GUP factor appears in the scalar and axial phase-space contributions and cancels from the local mean-spin ratio at fixed spacetime point and momentum. Thus, the leading GUP contribution to an experimentally relevant polarization observable arises through the Cooper-Frye freeze-out integrals and can be expressed as a covariance between the LRF momentum invariant and the local spin kernel. This cancellation is a consequence of the scalar density-of-states modification within a fixed pseudogauge and does not imply pseudogauge independence of the polarization observable. For $Λ$ hyperons, a Maxwell-Boltzmann thermal estimate shows that the dependence on freeze-out temperature and fluid-dynamical correlations is substantially larger than the Fermi-Dirac correction, which remains negligible over the temperature range considered. Present LHC precision corresponds only to a formal linear sensitivity of order $10$ - $30 GeV^{- 2}$ . Since this interval lies beyond the domain in which the linear GUP expansion is reliable, no exclusion limit is inferred. Differential measurements of hyperon polarization as functions of momentum, rapidity, collision centrality, and azimuthal harmonic structure provide the most direct experimental avenue for testing the predicted covariance dependence.
hep-phJ. Phys. G: Nucl. Part. Phys. 53 (2026) 0…
26
Bubble nucleation with thermal higher-dimensional operators
Fabio Bernardo · Maciej Kierkla · Nicholas Leister · Philipp Schicho · Pedro Schwaller
We quantify the impact of higher-dimensional operators in the effective theory for bubble nucleation, focusing on supercooled phase transitions in the classically conformal Abelian-Higgs model. While high-temperature dimensional reduction organizes hard thermal corrections into a tower of operators in a three-dimensional effective field theory, recent results show that dimension-six terms can dominate over higher-loop corrections to the equilibrium thermodynamics of the strongest transitions. To assess their effect on the nucleation rate and the derived near-equilibrium phase-transition observables, we develop a perturbative framework that includes them in the full one-loop nucleation rate. Including higher-dimensional operators both in the bounce action and in the fluctuation determinants, we solve the resulting Sturm-Liouville problem without a derivative expansion, using a modified Gel'fand-Yaglom method. For strongly supercooled transitions, we find that higher-dimensional operators only marginally affect the nucleation rate and the resulting observables. As a byproduct, we delineate the regime of validity of the high-temperature nucleation effective theory in supercooled phase transitions.
hep-phhep-th
27
Bosonic Contribution to Parity-Violating Møller Scattering at NNLO
Lisong Chen · Jens Erler · Ayres Freitas · Juhun Kwak
We calculate the dominant bosonic two-loop virtual electroweak corrections to parity-violating Møller scattering at low energies. The electron effective weak charge is extracted from the polarization asymmetry, retaining all contributions that are enhanced by $(1 - 4 sin^{2} θ_{W})^{- 1}$ or $ln^{2} (M_{W, Z}^{2} / Q^{2})$ relative to the tree-level contribution. Analytical results are obtained using the expansion by regions method in the low-energy limit $Q^{2} ≪ M_{W, Z}^{2}$ . Within this approximation, the dominant two-loop bosonic corrections shift the electron effective weak charge (or equivalently the polarization asymmetry) by $0.3%$ . We examine the origin of the leading contributions to this result and assess the remaining theoretical uncertainty from purely bosonic contributions for the MOLLER experiment to about 0.1%.
hep-phnucl-ex
28
Machine Learning Meets High-Energy Nuclear Physics: From Pattern Recognition to Physics-Integrated Discovery
Xun Chen · Weiyao Ke · Yu-Gang Ma · Long-Gang Pang · Kai Zhou
Machine learning (ML) in high-energy nuclear physics (HENP) is entering a new stage in which physical knowledge is incorporated more directly into data analysis, simulation, and physics inference. This mini-review focuses on developments that have matured in the past several years. Whereas earlier applications emphasized event classification, pattern recognition, and surrogate models for selected observables, recent work has moved toward physics-integrated workflows: calibrated Bayesian extraction of QCD matter properties, dense-matter equation-of-state inference from heavy-ion and neutron-star data, generative event modeling, neural unfolding of weak physical signals, differentiable inverse solvers, gauge-equivariant and diffusion-based lattice-field samplers, and neural reconstruction of model functions in holographic QCD. We survey recent applications of ML in heavy-ion collisions, neutron-star physics, lattice QFT, and holographic or continuum QCD. The emphasis is not on ML architectures alone, but on how they enter concrete physics workflows, how physical constraints such as symmetries, conservation laws, causality, thermodynamic stability, and topology are imposed, and how uncertainty quantification and validation determine whether an AI-assisted result can support a reliable physics conclusion.
hep-phcs.AIhep-lathep-th+1
29
LFV in flavourful SMEFT: Dimension-Six Running versus Dimension-Eight Mixing
Md Isha Ali · Siddhartha Karmakar · N Rajeev · Sudhir K. Vempati
We study how charged-lepton flavour violation (CLFV) generated in the $τ$ sector propagates into the $μ \to e$ sector within the Standard Model Effective Field Theory (SMEFT). Assuming that new physics at a scale $Λ ≫ v$ produces only dimension-6 operators that mediate $τ \to e$ and $τ \to μ$ transitions, we identify and compare the three mechanisms that induce $μ \to e$ observables. All three originate from double insertions of the two $τ \to ℓ$ operators and scale as $C_{6}^{τ e} C_{6}^{τ μ} / Λ^{4}$ . (T1) Renormalization-group mixing misaligns the charged-lepton mass matrix, and the rotation to the mass basis generates dimension-6 $μ \to e$ operators. (T2) A finite, non-logarithmic remainder, which we find to be negligible. (T3) The overall divergence renormalizes dimension-8 operators, contributing after electroweak symmetry breaking. Since T1 and T3 carry no relative power of $Λ$ , neither can be neglected at any scale, and only their comparison reveals which mechanism, and hence which $μ \to e$ observable, most strongly probes a given operator pair. Surveying the Warsaw-basis operators, we classify representative $(τ \to e, τ \to μ)$ pairs into T1-dominated, T3-dominated, and T1--T3-comparable regimes, and explain the hierarchy through the underlying mixing chains. Translating current $μ \to e γ$ , $μ \to eee$ and $μ \to e$ conversion limits into bounds on products of $τ \to ℓ$ Wilson coefficients, we find that they exceed the direct $τ$ -decay constraints by factors of ten to several hundred. Excluding either T1 or T3 would miss these limits by orders of magnitude for some pairs, and shift them by factors of two to three in others. Interpreting $μ \to e$ data as a probe of $τ$ flavour violation therefore requires both the dimension-6 RG running and the dimension-8 mixing contributions.
hep-phhep-exhep-th
30
A scalar-extended $U (1)_{L_{μ} - L_{τ}}$ explanation of the LUX-ZEPLIN 248 keV excess
Dipankar Pradhan · Abhik Sarkar
The recently observed dark matter (DM) nuclear recoil event at an energy of $248 \pm 23 (stat.) \pm 23 (syst.) keV$ at the LUX-ZEPLIN (LZ) experiment, favoring an inelastic scattering interpretation, has motivated various beyond the Standard Model (BSM) scenarios aimed at explaining the observed excess. In particular, this provides an opportunity to probe models that naturally accommodate inelastic DM scattering. In this work, we explore one such possibility by extending the $U (1)_{L_{μ} - L_{τ}}$ model with two complex scalar fields, $Φ$ and $S$ , carrying charges $- 1$ and $+ 2$ , respectively, under the $U (1)_{L_{μ} - L_{τ}}$ gauge symmetry. These charge assignments allow a trilinear interaction between the two scalar fields, which is crucial for generating the DM mass splitting. Following the spontaneous breaking of the $U (1)_{L_{μ} - L_{τ}}$ symmetry, with $S$ acquiring a vacuum expectation value and generating a mass for the BSM gauge boson $Z_{μτ}$ , the real and imaginary components of $Φ$ acquire a mass splitting. This naturally gives rise to an inelastic DM scattering scenario that can accommodate the LZ excess. We perform a likelihood-based assessment of the sensitivity of the model parameters to the observed event while consistently accounting for other relevant phenomenological constraints. Finally, we discuss the prospects for probing the viable parameter space at future experiments.
hep-phastro-ph.COhep-ex
31
Cosmic Birefringence from Large Lepton Asymmetry
Kentaro Kasai🇯🇵 · Ippei Obata🇯🇵
Cosmic birefringence, the rotation of the polarization plane of CMB photons, provides an intriguing probe of physics beyond the Standard Model. In this paper, we investigate a vector Chern-Simons coupling between the neutrino current and photons as a possible origin of isotropic cosmic birefringence. Firstly, we perform the first analysis of anisotropic cosmic birefringence induced by the neutrino current. We find that the anisotropic signal sourced by lepton-number isocurvature fluctuations can be important on large scales, whereas on small scales, the anisotropic signal induced by gravitational effects becomes dominant comparing with the axion-like particle (ALP) scenario. Secondly, we show that a large lepton asymmetry generated through the Affleck-Dine mechanism can successfully account for the observed isotropic birefringence, and discuss its possible connection to the recently reported low helium-4 abundances in Subaru EMPRESS and Atacama Cosmology Telescope (ACT).
↳ astro-ph.COhep-ph0 citations
32
Closed Universe, Quantum Entanglement and Observers
Hao Geng
It has been argued that in quantum gravity the Hilbert space associated with any closed universe is trivially one-dimensional. To reconcile this argument with the richness of our own universe, it was suggested that a nontrivial Hilbert space will emerge once an ``observer" is included. Such an ``observer" has been modeled in different ways. There are three concrete classes of models: $1)$ The ``observer" is modeled by a term in the full Hamiltonian of the system which is linear in a phase space variable; $2)$ The ``observer" is modeled in the quantum circuit model of holography as a subsystem in the closed universe which is entangled with an external non-gravitational system; $3)$ The ``observer" is argued to be described by the emergent Goldstone bosons when the diffeomorphisms are spontaneously broken. In fact, the third class was discovered by an attempt to physically realize the first class. In this paper, we will show that the second class can also be unified into the third class. Our result indicates that the emergence of the ``observer" is a manifestation of the $Massive Islands$ paradigm. It demonstrates that the graviton mass is a feature of the quantum state. One should think of the islands as closed universes and the Goldstone boson associated with the graviton mass as the ``observer", which is exactly the case at late-times for evaporating black holes. An implication of this work is that the ``observer" can ``observe" global symmetries in quantum gravity.
↳ hep-thgr-qchep-ph
33
Prescriptive Master Integrals of Maximal Weight at Two Loops
Jacob L. Bourjaily
We describe the construction of a spanning set of individually pure, planar master integrals involving massless particles in four dimensions which include all maximal-weight contributions at two loops. In this basis, every independent region associated with infrared divergence is individually matched by specific masters, with all other masters being manifestly finite in four dimensions.
↳ hep-thhep-ph
34
Interpretation of Nanohertz Gravitational Waves via Cosmic Strings in Post-BBN Matter and Kination Domination
Raymond T. Co · Siu Cheung Lam · Taegyu Lee
Recent pulsar timing array (PTA) observations have reported evidence for a common low frequency signal consistent with a stochastic gravitational wave background. In this work, we investigate the cosmic string interpretation of this signal in a non-standard cosmological history between big bang nucleosynthesis and recombination, featuring an early matter-dominated era followed by a kination phase. Previous studies have shown that kination can significantly modify the cosmic-string-induced gravitational wave spectrum, generating characteristic features in the nanohertz range and producing a shape consistent with current PTA data. Building on this, we perform separate Bayesian analyses of the NANOGrav 15-year and EPTA DR2 New+ datasets to quantify the extent to which such a cosmological history is favored by the data. We find substantial evidence for a transient period of matter and kination domination over the standard cosmological history within a cosmic-string interpretation of the gravitational-wave signal, with a Bayes factor $3.6 3_{- 0.21}^{+ 0.22}$ from the NANOGrav 15-year dataset, while leaving the inferred cosmic-string tension nearly unchanged. This cosmic-string-dominated scenario is particularly relevant if the contribution from supermassive black hole binaries (SMBHBs) is small, as hinted at by astrophysical population simulations. Compared with a scenario where gravitational waves are produced purely by SMBHBs, cosmic-string interpretations with and without an additional contribution from SMBHBs, across both expansion histories and datasets, reveal no significant preference.
↳ astro-ph.COhep-ph
35
Primordial black holes as a natural consequence of scale-invariance
TaeHun Kim · Wan-Il Park
We show that a scale-invariant $U (1)$ gauge theory can naturally realize large curvature perturbations around the end of thermal inflation, seeding the formation of primordial black holes (PBHs). The allowed nonminimal gravitational interaction $ξ$ of the Higgs field induces a Hubble-scale negative mass-squared term for positive $ξ \sim O (1)$ , and triggers a second order phase transition that ends thermal inflation while keeping the extra $e$ -folds small. This sharp contrast to the minimally coupled case allows the gauge coupling to be much smaller than unity. It turns out that field fluctuations are dominated by thermal fluctuations around the onset of the phase transition, and sufficiently amplified to produce an appreciable amount of PBHs with a wide range of possible masses. The associated scalar-induced gravitational waves (GWs) are accompanied by cosmic-string induced GWs coming from the breaking of the $U (1)$ symmetry. As a result, the generated PBH population can have a correlated GW signature relevant to pulsar timing arrays, space-based interferometers, or ground-based detectors.
↳ astro-ph.COhep-ph
36
Neutrino flavor conversion alters the lepton-emission self-sustained asymmetry in core-collapse supernovae
Noah Roux · Irene Tamborra · Maryna Mesiura
We solve the neutrino equations of motion in a half annulus, accounting for two spatial dimensions. At any location in the annulus, the neutrino momentum is characterized by a polar-angle distribution, two effective azimuthal angles, and an energy distribution. We explore how neutrinos change their flavor while decoupling from matter in the presence of the neutrino-driven hydrodynamical instability LESA (i.e., the Lepton-number Emission Self-sustained Asymmetry) during the stalled-shock phase of a core-collapse supernova. In our setup, LESA is responsible for an excess of $ν_{e}$ 's ( $ν ˉ_{e}$ 's) in the Northern (Southern) region of the annulus. Crossings in the $ν_{e}$ - $ν ˉ_{e}$ angular distributions appear in the ELN-depleted Southern region of the annulus, while crossings in the energy distributions of $ν_{e}$ - $ν_{x}$ and $ν ˉ_{e}$ - $ν ˉ_{x}$ are present throughout the annulus. We find that collisional instabilities drive flavor conversion just before neutrino decoupling, fast instabilities are prominent in the Southern region of the annulus, and slow instabilities dominate otherwise. Flavor conversion is most efficient in the Southern region and is responsible for a $5$ - $10%$ enhancement of the LESA dipole, independent of the neutrino-mass ordering. Our findings suggest that direction-dependent flavor conversion can have implications for the development of global neutrino asymmetries and hydrodynamical instabilities in core-collapse supernovae.
↳ astro-ph.HEhep-ph
37
Covariant BCFW for All Masses
Jacob L. Bourjaily · Michael Plesser
We use the massive spinor-helicity formalism to describe a novel construction for massive spinors which allows one to connect the many choices of bases useful in the representation of amplitudes involving massive particles, and we use this to derive a new formulation for the general BCFW shift that is valid regardless whether or which of the particles involved are massive or massless. This formalism should help facilitate a more coherent implementation of on-shell recursion for computing amplitudes involving massive particles in four dimensions.
↳ hep-thhep-ph
38
The Origin of the Fermi Halo-like Emission: A New Model of the Fermi Bubbles
Ilias Cholis · Leo Qiyuan Hu · Yi-Ming Zhong
We study the gamma-ray sky at high latitudes for energies between 0.3 and 900 GeV. We search for a contribution in the high-latitude sky and in the region of the Galactic Stellar Halo that would be beyond known astrophysical emissions, i.e., the galactic diffuse emission, the isotropic mostly extragalactic gamma-ray background, the Fermi Bubbles, Loop I, the contribution from the Galactic Center Excess, and the known point and extended gamma-ray sources detected by the Fermi-LAT Collaboration. We perform a sequence of template fits to the Fermi gamma-ray data, testing different regions of interest of the galactic sky, utilizing a large set of alternative galactic diffuse emission models, and implementing alternative fitting schemes to assess the impact of increased modeling complexity of the gamma-ray sky. We find that the halo-like emission recently reported by Totani (2025) is real, but it is likely due to emission from the Fermi Bubbles rather than dark matter annihilation in the Galactic halo. We provide new templates for the Fermi Bubbles, including an updated model for the Flat Bubbles and a detailed model of their substructures, the Cocoons and the Inner Bubbles. In combination, these components account for the previously reported halo-like emission. We also estimate the associated fluxes and spectral properties of the Flat Bubbles, the Inner Bubbles, and the Cocoons. This updated model for the Fermi Bubbles provides new input toward understanding their origin.
↳ astro-ph.HEastro-ph.COhep-ph
39
Scattering entanglement entropy between one particle species and the others
Yuan-Hao Zheng · Jiayin Gu
We construct the entanglement entropy of a general scattering process between one particle species (denoted as $A$ ) and the rest of the final state. Assuming a pure initial momentum eigenstate, we show that the reduced density matrix in particle $A$ 's Fock space is block-diagonal in zero-, one- and multi-particle states, and is diagonal in the momentum basis for the one-particle state. As a result, we could write down the Von Neumann entropy of particle $A$ , $S_{A}$ , in terms of scattering probabilities and differential cross sections, assuming no more than one particle $A$ is produced in the final state. $S_{A}$ contains the information of both the total scattering probabilities (or cross sections) and the differential distributions --- the latter depends on a phase-space resolution factor as a result of the infinite-dimensional momentum Hilbert space. Our result is general and model-independent since we consider the full final state from time evolution ( $S ∣ i ⟩$ ) rather than a specific outcome, and is applicable as long as the probability for producing multiple particle $A$ is subleading. We also obtain the $n \geq 2$ Tsallis and Rényi entropies in our framework and find out that, at the leading order, they are proportional to the total scattering probability and carry no differential information.
↳ hep-thhep-phquant-ph
40
The hidden sunrise in the energy-energy correlator
Matthew D. Schwartz · Xiaoyuan Zhang
The energy-energy correlator (EEC) is one of a handful of collider observables that can be computed analytically to high orders. As an energy-weighted cross-section, it exposes features of quantum field theory that scattering amplitudes do not, and it can be compared directly to data. As with scattering amplitudes, the analytic expressions require special functions beyond polylogarithms. In Henn et al., the EEC was computed to next-to-next-to-leading order (NNLO) for $N = 4$ super Yang-Mills (SYM) theory, and the result is expressed in terms of both harmonic polylogarithms (HPLs) and one two-fold integral, which contains elliptic curves. In this work, we report a complete result including the remaining elliptic sector, which is closely related to the sunrise Feynman integrals. We find the $j$ -invariants of the EEC and the sunrise agree identically under a Möbius map, and thus the elliptic sector in the EEC lives on the $Γ_{1} (6)$ modular curve of the sunrise integral. We then express the answer in terms of iterated Eisenstein integrals, which can be evaluated to high precision quickly. The analytic form also allows a first study of the EEC Landau bootstrap, and the understanding of its function space in $N = 4$ SYM offers a concrete handle on the elliptic sector of the EEC in QCD. Many of the technical results in this paper were completed with AI under human supervision.
↳ hep-thhep-phnucl-th
41
Primordial black holes
V.I. Dokuchaev · Yu.N. Eroshenko · V.V. Nikulin · K.A. Postnov · S.G. Rubin · V.D. Stasenko
Primordial black holes, whose formation in the early Universe was first hypothesized by Ya.B.~Zel'dovich and I.D.~Novikov in 1966 (the text of this pioneering article is provided in Appendix II to this review), have attracted increasing attention in recent years. Modern astronomical data across the electromagnetic spectrum, together with observations of gravitational waves and cosmic neutrinos, have revealed a number of unique astrophysical phenomena that may be related to primordial black holes formed in the pre-stellar cosmological epoch. This review describes various models of primordial black hole formation, as well as methods for testing these models with astronomical and astrophysical observations. In particular, we discuss in detail the formation of primordial black holes and their clusters through the collapse of closed domain walls and through effects associated with extra spatial dimensions of the Universe.
↳ astro-ph.COgr-qchep-ph
42
Observational Signatures of Dyonic Black Holes in Non-Linear Electrodynamics
Sobhan Kazempour · Sichun Sun · Zhiqing He · Chengye Yu
We study the observational features of thin-disk accretion and emission spectra for static, spherically symmetric dyonic black holes in non-linear electrodynamics (NLED). In contrast to classical Maxwell theory, where electromagnetic duality assumes equal charges, the coupling parameters in NLED introduce a new gravitational potential and modify the geometry in the strong-field regime. We also study the kinematic characteristics of particles on circular orbits, such as their angular velocity, specific energy, and specific angular momentum. It is found that modifications of NLED lead to a shrinkage of the ISCO radius, resulting in a shift of the radiation spectrum thermal maximum towards smaller radii and, consequently, an increase in the local effective temperature in comparison with the standard Schwarzschild and Reissner-Nordström solutions. Additionally, we compute null-geodesic orbits to determine the optical edge of both the photon sphere and the black hole shadow. In order to assess the observational validity of the aforementioned alternatives, we carry out a $χ^{2}$ goodness-of-fit test through the angular diameter constraints at the horizon scale collected by the Event Horizon Telescope (EHT) concerning Sagittarius A* ( $Sgr A^{*}$ ). We prove that both these dyonic NLED and purely magnetic models have good statistical agreement with experimental data.
↳ gr-qcastro-ph.HEhep-ph
43
Quantum Localization Limit of Transport-Based Femtoscopy
Jiaxing Zhao · Joerg Aichelin · Elena Bratkovskaya
Femtoscopic correlations in proton-proton and heavy ion collisions are commonly calculated using emission sources from microscopic transport models, where emitted particles are represented by classical phase-space points with simultaneously specified positions and momenta. This point-emitter picture neglects the finite phase-space localization required by quantum mechanics, which can become relevant when the localization scale approaches the femtoscopic source size, particularly in small collision systems. We formulate a quantum treatment by replacing each transport phase-space point with a minimum-uncertainty Gaussian phase-space distribution. Finite localization then induces both spatial and momentum smearing; in the presence of coordinate-momentum correlations, the latter produces a nontrivial modification of the emission source. Using proton--proton collisions at $s = 7 TeV$ simulated with the microscopic Parton--Hadron--String Dynamics transport approach, we show that this effect significantly modifies the proton-pair source and its momentum correlation. Our results expose a quantum localization effect overlooked in transport-based femtoscopy and establish the regime in which the classical point-emitter approximation is valid.
↳ nucl-thhep-ph
44
Massive de Sitter Correlators as Finite Mellin-Barnes Integrals
Amara McCune
Using the Mellin-Barnes representation of de Sitter propagators, we reduce tree-level heavy-particle exchange to finite integrals that converge at physical kinematics on mass-independent contours, and one-loop diagrams to the same integrand times a flat-space momentum factor. We evaluate the triple-exchange bispectrum without analytic continuation and compute the complete one-loop triangle at general mass. These give cosmological collider predictions, the oscillatory signatures of heavy particles during inflation, for multiple exchanges and loops at arbitrary masses.
↳ hep-thastro-ph.COhep-ph
45
Hamiltonian framework for Chiral Gauge Theories on a Disk Boundary
Srimoyee Sen
I propose a Hamiltonian framework for chiral gauge theories (CGT) based on a Euclidean formulation which uses 2n dimensional chiral fermions on the boundary of a 2n+1 dimensional disk. In the original Euclidean formulation, boundary gauge fields were extended into the bulk using $2 n + 1$ dimensional gauge field equations of motion (EOM) which creates a bottleneck for constructing a Hamiltonian. I present an alternate proposal for extending the gauge fields into the bulk that is compatible with both a Hamiltonian framework and a Euclidean path integral. Applying this to Abelian gauge fields produces exact expressions of interior fields as a functional of the boundary fields, which can be directly used in a Hamiltonian formulation. Euclidean analysis of the new gauge field extension shows that it can preserve the non-perturbative content of the original construction, including the behavior of topological charge, associated chiral fermion zero modes and an absence of the strong CP problem when applied to the Standard Model. This construction opens up a route to a Hamiltonian treatment and future quantum simulation of CGTs on a disk boundary.
↳ hep-lathep-phhep-thnucl-th
46
Neutrino oscillations inside ultrarelativistic matter: on the role of the Tolman VI spacetime
Daniele Gregoris
While both neutrino propagation in photons and ultrarelativistic plasmas and neutrino oscillations in curved spacetimes have been studied extensively, their combination in a self-gravitating geometry appears not to have been considered previously. In this paper, we will investigate neutrino oscillations inside a static spherically symmetric spacetime, derived self-consistently from Einstein's equations, supported by ultrarelativistic matter. By relying on the geodesic motion and geometrical symmetries of the configuration, we will compute analytically the neutrino eikonal and spinoptics phase oscillations. Next, we will relate resonance phenomena to the physical interpretation of the background material inside which neutrinos travel for disentangling gravitational versus electroweak effects. We will inspect the effects of the pure gravitational and pure matter fields, and of the temperature in the neutrino oscillations; we will explain why our results are not coordinate artifacts, and we will certify our heuristic method by comparing with the asymptotic behaviours predicted by thermal field theory approaches. We will raise awareness on the relevance of the spinoptics phase shift entering the flavor conversion probability, should the neutrinos hit a curvature singularity. Theoretically, we will scrutinize the separate roles of geometrical symmetries versus physical features of the configuration, while astrophysically we will qualitatively discuss neutrino oscillations inside stars and in the Cosmic Microwave Background at different temperature and density conditions. Our research puts forward, in the context of the Tolman VI metric, an observational method for identifying naked singularities in our Universe: neutrinos would simultaneously be physically overlapped, in flavor-equilibrium and quantum-mechanically scrambled.
↳ gr-qchep-ph
47
Neutron star cooling with $Δ$ dUrca processes
Yogeesh N · Monika Sinha · Vishal Parmar
The cooling of neutron stars (NSs) provides insight into their composition and equation of state. However, a complete understanding of this phenomenon is still an open question. The early stage of NS cooling is dominated by neutrino emission from the core, which rapidly cools the star. Urca processes are one such mechanism where neutrinos escape from the core, carrying away most of the heat. Nucleonic and hyperonic direct Urca processes are known rapid cooling mechanisms. The possible appearance of $Δ$ baryons in dense matter introduces additional weak-interaction channels, including $Δ$ direct Urca processes. Although such processes have been discussed in the context of $Δ$ -admixed NS matter, their neutrino emissivities and impact on NS cooling have not been systematically investigated. In this work, for the first time we incorporate the neutrino emissivities of the relevant $Δ$ direct Urca processes into NS cooling simulations. We investigate the thermal evolution of $Δ$ -admixed NSs and assess the impact of these additional neutrino emission channels on their cooling behavior. We find that $Δ$ direct Urca processes can provide an efficient neutrino-cooling mechanism and significantly accelerate the thermal evolution of NSs. Our results demonstrate that $Δ$ baryons and their associated weak-interaction processes can play an important role in explaining NSs with unusually low surface temperatures and provide a new connection between the composition of dense matter and NS cooling observations.
↳ astro-ph.HEhep-ph
48
Quantum Gravity in Asymptotically Flat Spacetimes from Unstable D-Branes
Roji Pius
We present a non-perturbative formulation of quantum gravity in asymptotically flat spacetimes using Witten's cubic open string field theory (OSFT) on unstable D-branes. Given that the massless spin-2 sector of the closed string spectrum inherently encodes the degrees of freedom of quantum gravity, we establish this connection by mapping on-shell closed string excitations directly to gauge-invariant operators in OSFT, realizing a concrete flat-space analogue of the AdS/CFT correspondence. By evaluating the OSFT correlation functions of these operators perturbatively around the tachyon vacuum, we systematically reproduce the all-orders genus expansion of the closed string S-matrix for the associated states. This demonstrates that closed string theory-and thus quantum gravity-emerges dynamically from the open string tachyon vacuum, establishing Witten's OSFT as a fully calculable, non-perturbative framework for flat-space quantum gravity.
↳ hep-thgr-qchep-phmath-ph+1
49
Mass quench in interacting finite-size quantum field system
Grachik A Simonian · Alexey G. Mikhaylenko · Andrew G. Semenov
In this work, we theoretically investigate the non-equilibrium evolution of the correlation functions of a quantum scalar field following a mass quantum quench in a finite-size system. The self-consistent equation for the Keldysh (statistical) correlation function is solved numerically in the one-loop approximation. A specific spatio-temporal effect is observed: at a point in time approximately equal to half the system size, the effective mass experiences a strong disturbance. It is shown that this effect is driven by the interference of counter-propagating wave fronts of fluctuations that propagate within the light cone and is induced by periodic boundary conditions.
↳ hep-thcond-mat.stat-mechhep-phquant-ph
50
An updated model of neutrino emission from proto-neutron stars
Matteo Ballelli · Federica Pompa · Christoph Ternes · Marco Drago · Giulia Pagliaroli
We present an improved parametric model for neutrino emission from core-collapse supernovae that directly connects neutrino luminosity and average energy to stellar properties during emission. Our model incorporates two critical physical processes: convection within the proto-neutron star and the evolution of the neutrinosphere radius during the early emission phase. Using simulated datasets of supernova neutrino events in the Super-Kamiokande detector, we assess the sensitivity to astrophysical properties in the event of a future detection. We show that the neutrino mass ordering plays a crucial role in determining which parameters can be constrained by the observed neutrino data.
↳ astro-ph.HEastro-ph.SRhep-ph
51
Asymptotic Safety in Gauge Theories beyond Four Dimensions: Perturbative Tests and Fixed-Point Mergers
Aldo Deandrea · Jie Liu · Roman Pasechnik · Zhi-Wei Wang · Yu-Bo Zhao
Non-Abelian gauge theories above four dimensions may admit an interacting ultraviolet fixed point through the competition between canonical scaling and gauge-field antiscreening. Using the four-loop $MS$ beta function continued to $D = 4 + 2 ϵ$ , we determine the largest dimension $D_{pt} = 4 + 2 ϵ_{pt}$ below which successive loop corrections to the fixed point remain hierarchically ordered under a specified ratio criterion, and map $D_{pt}$ over color and flavor numbers for fermions in the fundamental representation of $S U (N)$ . At $D = 5$ , we construct rational anomalous dimensions with a fixed, pole-regularized denominator inspired by the functional renormalization group (fRG). Matching to the $MS$ series through one, two, and three loops produces progressively smaller shifts in the critical flavor number and coupling at the ultraviolet--infrared merger (the point where the infrared and ultraviolet fixed points coincide), yielding $N_{f}^{cr} ≃ 2.09 N$ at large $N$ in the three-loop construction. This low-order stabilization, together with qualitative evidence from fRG flows including higher gauge operators, suggests a potential merger scenario that bounds the candidate asymptotically safe region in flavor number. The resulting color--flavor map provides guidance for five-dimensional model building by displaying both the baseline perturbative-control boundary and the candidate three-loop merger boundary. Four-loop matching, however, retains an interacting ultraviolet fixed point beyond the three-loop merger boundary, with no merger found for integer $2 \leq N \leq 15$ and $0 \leq N_{f} / N \leq 11/2$ . The sensitivity of the fixed-point structure to higher-order terms leaves both scenarios open, highlighting fixed-point annihilation as a potential constraint on five-dimensional asymptotic safety.
↳ hep-thgr-qchep-lathep-ph
52
Wave packets asymptotics in $κ$ -minkowski space
Adith A · A. Bhagwat
In this paper, we study the nature of wave packets and their decay behavior in the $κ$ -Minkowski space. We employ techniques from singularity theory throughout our analysis. Specifically, we use methods from the theory of Lagrangian singularities and caustics to study the topology of the energy-level manifold. The Newton polyhedron method from the theory of oscillatory integrals is applied to analyze the decay behavior of wave packets. We find that for a generic Hamiltonian in the $κ$ -Minkowski space, the associated wave packets exhibit different decay rates depending on the control parameter of the system. When the control parameter takes values on the cusp, the system exhibits decay of order $t^{- 1/4}$ ; otherwise, it exhibits decay of order $t^{- 1/2}$ . This distinctive behavior of wave packets in the $κ$ -Minkowski makes it fundamentally different from commutative spacetime.
↳ math-phgr-qchep-phhep-th+2
53
A Pairwise Surrogate for Gravitational-Wave Spectra from Highly Relativistic Vacuum Bubble Collisions
Malte Buschmann · Toby Opferkuch
Gravitational waves from vacuum first-order phase transitions probe the nonlinear dynamics of relativistic bubble collisions. Predicting their spectrum requires resolving Lorentz-contracted scalar bubble walls throughout a volume containing many bubbles, making the large-boost regime prohibitively expensive for direct lattice simulations. We develop a simulation-based pairwise surrogate that separates the microscopic collision dynamics from the geometry of the multi-bubble transition. This utilizes symmetry-reduced $(1 + 1)$ -dimensional scalar-field simulations to build a library of two-bubble gravitational-wave spectra, including the nonlinear post-collision evolution. These spectra are combined with geometric weights that account for screening by other bubbles. We test the two-bubble spectra and the reconstructed spectra of three- and many-bubble systems against full $(3 + 1)$ -dimensional lattice simulations. Not only can the surrogate be orders of magnitude cheaper computationally, but it also provides access to highly relativistic collisions beyond the practical reach of direct many-bubble simulations. This provides a route to studying how the spectral amplitude and shape depend on the collision boost and scalar potential.
↳ gr-qcastro-ph.COhep-ph

Affiliations

first authorsco-authorsvia INSPIRE