HEP Phenomenology·hep-ph

Wed·Aug 26, 2026Wednesday·August 26, 2026

31 papers—17 primary·14 cross-listed

01
Operational quantum estimation theory for neutrino oscillations: identifiability, attainability, and spectral precision bounds
Jianlong Lu🇸🇬
Quantum Fisher information (QFI) bounds state-encoded precision before measurement choice but does not establish identifiability, joint attainability, or detector sensitivity. We develop an operational framework for three-flavor oscillations that separates state, measurement, and reconstructed-event information. At fixed baseline, energy, source flavor, and matter profile, the propagated state is a pure qutrit, so its six-coordinate QFI has rank at most four. Resolved broadband components can restore rank because the aggregate kernel equals the intersection of their active kernels. We analyze joint attainability using quantum curvature, exact pure-state Holevo costs, and numerical primal-dual brackets, and propagate information through flavor projection, detector response, Poisson sampling, and nuisance profiling. An independent implementation of the public DUNE GLoBES configuration reproduces the reference spectra to relative error $3.87 \times 1 0^{- 16}$ and the profiled likelihood curvature to $3.26 \times 1 0^{- 6}$ . Under the declared scaling and tolerance, its 264-bin event information has numerical rank six at all 176 documented physics points, whereas any four retained rule totals have rank at most four. The weakest record has effective rank five at the declared practical threshold. A conditional likelihood pilot also shows finite-grid overcoverage and dependence on the auxiliary-measurement ensemble. The framework identifies when local quantum or Fisher bounds do not support global experimental-sensitivity claims.
hep-ph0 citations
02
When the HL-LHC is blind, LISA is deaf (but not vice versa): 2HDM collider-cosmology synergies
Stefano Moretti🇬🇧 · André Pousette🇸🇪 · Carlo Tasillo🇸🇪
Extensions of the Standard Model scalar sector can render the electroweak phase transition first-order and thereby provide the departure from thermal equilibrium required for electroweak baryogenesis, while at the same time sourcing a stochastic gravitational wave (GW) background in the milli-Hertz range. In this work, we investigate electroweak phase transitions in the CP-conserving type-I two-Higgs-doublet model (2HDM), focusing on the interplay between collider constraints at the HL-LHC and the projected sensitivity of LISA. We compute the expected GW background due to strong first-order electroweak phase transitions and perform extensive Monte Carlo scans over the collider-viable model parameter space. We find that GW signals within reach of LISA arise almost exclusively in regions of parameter space that necessarily predict observable deviations at the HL-LHC, in particular through the $H \to Z Z$ decay channel of the heavy CP-even and neutral Higgs state with $m_{H} ≃ 180 - 250 GeV$ . Our results highlight the decisive complementarity between collider and GW probes and show that the largest parts of the 2HDM parameter space relevant for phase transition signals at LISA can already be tested by HL-LHC. A possible future discovery of 2HDM states at the HL-LHC, however, would not allow conclusive statements about LISA being able to find a GW background due to the amount of parameter tuning required for an observable GW signal. In order to evaluate possible caveats of this statement we study the theoretical uncertainties related to the GW predictions in a two-fold approach using both state-of-the-art tools, BSMPT and TransitionListener, and also allow for model realizations in which the electroweak symmetry is not restored in the high-temperature limit, which are the ones combining the loudest GW signals with the weakest collider coverage.
hep-phastro-ph.CO0 citations
03
Testing New Scalar Interactions in Few-Electron Highly Charged Ions
M. Moretti🇩🇪 · C. de Jonge🇩🇪 · J. Jaeckel🇩🇪 · C. H. Keitel🇩🇪 · Z. Harman🇩🇪
We investigate how a hypothetical scalar boson mediating an interaction between electrons as well as between electrons and nucleons would affect the g factor of lithium-like highly charged ions. In such ions, the strong nuclear Coulomb fields enhance electron-electron interactions, making them ideal systems for detecting subtle new physics signatures. Exceptionally accurate quantum electrodynamic predictions and experimental data in such few-electron systems allow for sensitive probes, thereby enabling bounds on the boson's coupling strength. Exploiting the enhanced sensitivity of highly charged ions to short-range interactions, we combine g-factor measurements and quantum electrodynamic theory predictions of lithium- and hydrogen-like ions with the free-electron magnetic moment and an isotope-shift measurement to constrain simultaneously the electron-proton, electron-neutron, and electron-electron coupling combinations as functions of the scalar mass. We find that precision g-factor spectroscopy provides competitive constraints on scalar interactions over a broad mass range and, in particular, yields bounds on electron-electron interactions from bound-state QED observables.
hep-ph0 citations
04
Soft Scale Symmetry Breaking with Laguerre Explicit Regulators
A. R. Vieira🇧🇷
In this work, we search for explicit regulators that do not spuriously break scale invariance starting from conditions established by implicit regularization. There is a family of regulator functions that obeys the conditions and leads to soft breaking terms of the dilatation current. This family of functions is shown to be related to the Laguerre polynomials. We apply this approach by revisiting quadratic divergences in the context of the naturalness problem of the Standard Model and show that the quadratic dependence of the Higgs mass on the cutoff is not required by consistency of scale-symmetry breaking and can be removed within this class of regulators.
hep-phhep-th0 citations
05
Femtoscale imaging of the proton with Ioffe-time distributions
Robert G. Edwards🇺🇸 · Joe Karpie🇺🇸 · Christopher Monahan🇺🇸 · Kostas Orginos🇺🇸 · Anatoly Radyushkin🇺🇸 · David Richards🇺🇸 · Eloy Romero🇺🇸 · Savvas Zafeiropoulos🇫🇷
Mapping how strongly interacting constituents are distributed within protons is a key goal of nuclear physics and a major direction of the future Electron Ion Collider program. We propose a novel space-time description of hadron structure in terms of impact-parameter Ioffe-time distributions, relating spatial density in the plane transverse to the proton momentum and the time between the probe's absorption and the product's emission in the longitudinal direction. Using lattice Quantum Chromodynamics, we perform the first calculation of the Ioffe-time-dependent mean squared proton radii and compare our results with estimates in the Goloskokov-Kroll model. We derive a relationship between the experimentally measurable Compton form factor and the generalized Ioffe-time distribution, which allows us to perform the first extraction of the Compton form factor from lattice calculations.
hep-phhep-latnucl-th0 citations
06
Neuro-dispersive extractions of light-meson resonances
Wyatt A. Smith🇺🇸 · Arkaitz Rodas🇺🇸 · Marius D. Thomas🇺🇸 · César Fernández-Ramírez🇪🇸 · Giorgio Foti🇮🇹 · Lin Qiu🇺🇸 · Adam P. Szczepaniak🇺🇸 · Alessandro Pilloni🇮🇹
We present the first dispersive extraction of resonant poles from analytically continued neural networks. We use S-matrix informed neural networks (SINNs) trained to respect unitarity, analyticity, and crossing symmetry, without fixing a specific amplitude parametrization. The SINN framework controls representation dependence, enables constrained data selection, and enforces first principles. A large ensemble of networks trained on $π π$ scattering data propagates correlated uncertainties to all derived observables. We obtain robust determinations of the $σ / f_{0} (500)$ , $ρ (770)$ , and $f_{0} (980)$ poles of $π π$ scattering. Scattering lengths are determined alongside the amplitudes, while Adler zeroes emerge as predictions of the analytic structure. The results are stable against variations of the network architecture, and our approach can easily be adjusted for analysis of other reactions relevant to New Physics searches.
hep-phnucl-th0 citations
07
S-matrix informed neural networks for amplitude analysis
Wyatt A. Smith🇺🇸 · Arkaitz Rodas🇺🇸 · Marius D. Thomas🇺🇸 · César Fernández-Ramírez🇪🇸 · Giorgio Foti🇮🇹 · Lin Qiu🇺🇸 · Adam P. Szczepaniak🇺🇸 · Alessandro Pilloni🇮🇹
Reconstructing scattering amplitudes from finite, noisy, and mutually inconsistent measurements is an ill-posed inverse problem common to many reactions relevant to particle physics. We introduce S-matrix informed neural networks (SINNs), and demonstrate their ability to learn scattering amplitudes directly from data while respecting first principles. We further develop a novel data selection procedure, which uses the response of constrained neural network ensembles to identify a set of experiments compatible with first principles, and with each other. We apply this framework to $π π$ scattering, producing reusable amplitudes and correlated uncertainties without relying on a fixed functional form. We validate our results against residual model dependencies and training biases through closure tests and ablations. We find negligible impact of model architecture on our results. Our workflow unifies physics-constrained representation learning, data selection, and uncertainty quantification. Our strategy is transferable to other scattering processes, and other constrained physics problems limited by inconsistent data.
hep-phcs.LGnucl-th0 citations
08
Photon and gluon gravitational form factors of proton in QCD
Z. Asmaee🇮🇷 · K. Azizi🇮🇷
The energy-momentum tensor provides a unique insight into the internal gravitational structure of the proton by revealing how energy, momentum, and mechanical properties are distributed among its different QCD components. The gravitational form factors associated with different components of the QCD energy-momentum tensor allow us to investigate the individual contributions of these sectors to the gravitational properties of the proton. In this work, we calculate the photon and gluon gravitational form factors of the proton within the framework of QCD sum rules. Using the photon and gluon components of the QCD energy-momentum tensor, we derive the corresponding sum rules for four independent gravitational form factors. Their momentum transfer dependence is analyzed within the validity region of the method and extrapolated to zero momentum transfer using a multipole parametrization. The resulting parametrizations of the form factors are used to extract the mass and scalar radii associated with the photon and gluon sectors. Our results indicate that the gluon mass radius is smaller than the photon mass radius, suggesting a more localized gluonic energy distribution inside the proton. These findings provide new nonperturbative information on the gravitational structure of the proton and offer complementary theoretical results for future lattice QCD calculations and phenomenological studies.
hep-phhep-exhep-lat0 citations
09
Topics in the phenomenology of axions: the cases of cosmic strings and superradiance
Antonios Kyriazis🇺🇸
Originally proposed as a solution to the strong CP problem and later understood to be a good dark matter candidates, axions have appeared in a variety of beyond-the-standard-model theories and are imbued with rich phenomelogical consequences. In this dissertation, we will examine two of these consequences: the emission of axions from cosmic strings and the superradiant mechanism in black hole physics. The spontaneous symmetry breaking of a global symmetry in the early universe can give rise to a network of cosmic strings, which emit ultra light, axion-like particles that can contribute to the dark matter density. We will discuss how the associated density fluctuations of these particles can be computed from first principles by treating them as a collection of plane waves. We will then calculate the density power spectrum and compare it to well-established cosmological observables, as well as to observables from future surveys, to derive constraints on the mass of the particles and the symmetry breaking scale. These light axion-like particles can also form a gravitational atom around a spinning black hole through the superradiance process. Considering the black hole to be part of a binary system, the tidal potential of the companion periodically perturbs the gravitational atom such that an atomic transition occurs between two of its energy states. Gravitational waves are emitted by the cloud during this transition. We will derive the analytical formulae of both the strain waveform and frequency spectrum of the signal and identify the systems that would be the most promising for detecting it in future, space-based gravitational wave observatories.
hep-phastro-ph.CO0 citations
10
SU(9) grand unified model with rank-reducing discrete boundary conditions on $T^{2} / Z_{4}$
Yoshiharu Kawamura🇯🇵 · Kentaro Kojima🇯🇵 · Toshifumi Yamashita🇯🇵
We study a six-dimensional SU(9) grand unified model with rank-reducing discrete boundary conditions and continuous Wilson line phases on the orbifold $T^{2} / Z_{4}$ . We show that the model can realize grand unification of the Standard Model gauge interactions and electroweak symmetry breaking via the Hosotani mechanism. The model has several attractive features. Two Higgs doublets arise as zero modes of the extra-dimensional components of the gauge field, and the leptons and quarks in each generation are separately embedded into two bulk multiplets, in the $36$ and $84$ representations of SU(9), respectively, without exotic matter. Furthermore, proton decay processes mediated by the gauge bosons in the bulk are absent, because the leptons and quarks belong to different bulk multiplets.
hep-ph0 citations
11
Searching for Solar-Basin Axionlike-Particle Decay with XMM-Newton Blank-Sky Observations
Bo Zhang🇨🇳 · Chi Zhang🇨🇳 · Lei Lei🇨🇳 · Yang Yu🇨🇳 · Guan-Shen Wang🇨🇳 · Bing-Yu Su🇨🇳 · Lei Feng🇨🇳
Axion-like particles (ALPs) bound in the solar gravitational field form the so-called ALP solar-basin. Since the two-photon decay of non-relativistic particles is approximately isotropic, this population can be searched for using observations in the anti-solar direction. In this work, we propose a search strategy for narrow decay-line signals from the ALP solar basin using \textit{XMM-Newton} blank-sky observations (XMM-BSOs) stacked spectra data taken in directions opposite to the Sun. By jointly fitting the signal and background model, we obtain limits on $g_{aγ γ}^{95}$ in the mass range $m_{a} = 1.4 - 16 keV$ , with typical sensitivities of $g_{aγ γ} \sim 1 0^{- 10} - 1 0^{- 11} GeV^{- 1}$ . We have implemented the first anti-solar search for the solar basin, demonstrating that this strategy can exploit the stacked exposure of a large number of X-ray observations and provide a scalable analysis framework for future searches.
hep-phastro-ph.HE0 citations
12
Exclusive Determination of $∣ V_{c b} ∣$ from Semileptonic Decays $B \to D^{(*)} ℓ ν_{ℓ}$
Xue-Wen Chen🇨🇳 · Bo-Yan Cui🇨🇳 · Jia-Wei Zhang🇨🇳 · Xue-Chen Zhao🇨🇳 · Ya-Hui Chen🇨🇳
We present an updated exclusive determination of the CKM matrix element $|V_{cb}|$ from the semileptonic decays $B\to D^{(*)}\ell\bar{\nu}_{\ell}$. Our analysis combines the latest Belle II measurements, updated lattice-QCD calculations of the $B\to D^{(*)}$ form factors at small hadronic recoil, and correlated large-recoil SCET sum-rule predictions incorporating next-to-leading-order QCD corrections and several power-suppressed contributions. We consider three fit scenarios with progressively enlarged input sets and find that the inclusion of the large-recoil sum-rule constraints substantially reduces the form-factor uncertainties. From the full global fit, we obtain$|V_{cb}|=(39.18 \pm0.47)\times10^{-3}$. Using the combined lattice-QCD and LCSR fit, we predict $R(D)=0.3069\pm0.0080,\qquad R(D^*)=0.2548\pm0.0043$, and provide differential decay distributions in the momentum transfer and angular variables for both the muon and tau channels. Comparisons of the individual and correlated predictions for $R(D)$ and $R(D^*)$ with the experimental averages reveal a persistent tension. In particular, our theoretical 68\% confidence region shows little overlap with the experimental average. All correlations among the fitted parameters are retained in the uncertainty propagation. Our results therefore provide updated Standard Model benchmarks for tests of lepton-flavor universality. Improved lattice-QCD calculations, sum-rule predictions, and Belle II measurements will be essential for determining whether the remaining discrepancies originate from theoretical systematic uncertainties or from physics beyond the Standard Model.
hep-ph0 citations
13
Hyperfine Mixing and Final-Spin Redistribution in Inclusive $Ξ_{b c} \to H_{cc} + X$
Ishtiaq Ahmed🇵🇰
In this work, we study the effect of hyperfine mixing on the inclusive weak decay $Ξ_{b c} \to H_{cc} + X$ , which has been proposed as a useful channel for searching for the beauty-charmed baryons. Starting from the inclusive heavy-diquark framework, we include the mixing between the scalar and axial-vector $b c$ configurations and decompose the final doubly charmed system into the $J_{f} = 1/2$ and $J_{f} = 3/2$ spin sectors. Within a minimal scalar-to-axial current model, we find that the interference between the scalar and axial components is large in each spin sector but cancels after summing over the two members of the ground-state $cc q$ spin multiplet, $Γ_{A S}^{1/2} = - Γ_{A S}^{3/2}$ . As a consequence, the inclusive branching fraction remains close to the original estimate when feed-down from the spin-excited $Ξ_{cc}^{*}$ sector is included. However, the direct ground-state contribution is strongly spin selective: $Ξ_{b c}^{(1)}$ dominantly feeds the $J_{f} = 1/2$ $Ξ_{cc}$ channel, whereas $Ξ_{b c}^{(2)}$ dominantly feeds the $J_{f} = 3/2$ $Ξ_{cc}^{*}$ sector. We also test the stability of the aforementioned conclusion under variations of the mixing angle, scalar-current normalization, and recoil-shape choice. It is found that hyperfine mixing is hidden in the total inclusive rate, but can be exposed through the final-spin composition.
hep-ph0 citations
14
Electron and Muon $g - 2$ Constraints on Light Vector Bosons: Dark Photons and the $X_{17}$ Boson
Raoul Serao🇮🇹 · Antonio Capolupo🇮🇹
We combine the current experimental muon $g - 2$ world average, which incorporates the final Fermilab result, with the latest electron $g - 2$ determinations based on cesium and rubidium measurements to set 95\% CL exclusion contours for a pure vector mediator coupled to leptons. We explicitly test the assumption that the electron and muon coupling magnitudes are equal by comparing this restricted case with the case of independent electron and muon couplings and quantify the impact on the allowed parameter space. In the minimal visible dark-photon model, both leptons constrain the same kinetic mixing and are analyzed through a combined $χ^{2}$ analysis. We compare the resulting $g - 2$ bounds with existing accelerator direct-search exclusions and model-dependent astrophysical and cosmological constraints. From the accelerator comparison, we identify a region in the $(m_{A^{'}}, ∣ ϵ ∣)$ parameter space near $17$ ~MeV, close to the reported $X_{17}$ mass, that remains allowed by the direct-search contours displayed here but is excluded by the cesium-based electron $g - 2$ constraint. The rubidium-based fit does not exclude this interval. For an $X_{17}$ boson with independent lepton couplings, we constrain the electron and muon couplings separately. Electron-only direct searches leave two disconnected allowed regions near the reported $X_{17}$ mass: a newly reopened low-coupling interval and a higher-coupling region above the NA64 excluded band. The cesium-based electron $g - 2$ constraint closes the higher-coupling region, while the rubidium-based constraint reduces its extent; neither affects the newly reopened low-coupling interval. Using the current experimental muon $g - 2$ world average, we obtain a new $g - 2$ -based exclusion region for the muon coupling, with no significant preference for a nonzero coupling.
hep-ph0 citations
15
Resummed Power Corrections in Nuclear DVCS
John Terry🇺🇸
Generalized Parton Distributions (GPDs) encode the three-dimensional structure of hadrons, yet their modification in nuclear matter remains largely unconstrained. We report the first derivation of resummed QCD power corrections to deeply virtual Compton scattering on nuclei. Extending techniques from inclusive deep inelastic scattering, we identify the nuclear-enhanced higher-twist contributions generated by coherent final-state scattering of the struck quark in the medium and resum them to all orders. The corrections are enhanced by an effective nuclear size $A_{eff}^{1/3}$ and result in an exclusive analogue of dynamical nuclear shadowing. The shift is controlled by a parameter already fixed by inclusive nuclear data, so no new nonperturbative input enters. We present quantitative predictions for nuclear modifications of beam-spin observables at the Electron--Ion Collider.
hep-phnucl-exnucl-th0 citations
16
Discovery Potentials for the Cosmic Neutrino Background using Single Arm Interferometer
Chrisna Setyo Nugroho🇹🇼
We study the interaction between light and non-relativistic cosmic neutrino background (CNB). We propose single arm laser interferometry with coherent laser source and two distinct squeezing operators to probe such interaction. We analyze the induced phase shift in four distinct quantum regimes of the interferometer operation: the standard quantum limit (SQL), the Heisenberg limit, super-Heisenberg limit with $N^{3/2}$ enhancement, and super-Heisenberg limit with $N^{2}$ enhancement where $N$ is the number of photons in the interferometer. We demonstrate that the $N^{2}$ super-Heisenberg enhancement has the potential to probe the magnetic moment down to $1 0^{- 25} μ_{B}$ where $μ_{B}$ is the Bohr magneton. If the CNB and photons interact via its magnetic moment, this interaction could be revealed in single arm interferometer operating at super-Heisenberg limit with $N^{2}$ enhancement.
hep-ph0 citations
17
Probing Dirac Dark Matter in Composite Higgs Models with Xenon and Argon targets
M. G. Belyakova🇷🇺 · R. Nevzorov🇷🇺
Recent advancements in direct detection (DD) experiments stimulate the investigation of the interactions of dark matter (DM) with nucleons and nuclei. In the framework of Composite Higgs Models (CHMs) the lightest Dirac composite particle (LDCP) can be stable composing a significant fraction \xi of the observed DM relic abundance. We consider the elastic scattering of the LDCP on nucleons as well as on xenon (Xe) and argon (Ar) nuclei within the CHMs in which the LDCP magnetic moment, its mass and its coupling to the Higgs doublet are suppressed by an approximate U(1) symmetry. The LDCP with non-zero magnetic dipole moment can result in a substantial enhancement of the differential event rate in the DD experiments at low recoil energies of nuclei. Assuming \xi\ge 0.1, we identify the region of the parameter space where such enhancement may be potentially observable. In addition we specify some observables that can be useful in discriminating between the DM fermions with non-zero magnetic moment and other types of dark matter particles which don't have similar electromagnetic properties.
hep-phgr-qchep-exhep-lat+10 citations
18
Bound and Resonant Spectra of Few-Lepton Coulomb Systems
Liang-Zhen Wen🇨🇳 · Yao Ma🇨🇳 · Zhi-He Shen · Shi-Lin Zhu🇨🇳
We present a unified calculation of bound and resonant states in purely leptonic Coulomb systems: $e^{-} e^{-} e^{+}$ ( $Ps^{-}$ ), $μ^{+} e^{-} e^{-}$ ( $Mu^{-}$ ), $μ^{+} μ^{+} e^{-}$ ( $Mu_{2}^{+}$ ), $e^{+} e^{+} e^{-} e^{-}$ ( $Ps_{2}$ ), and $μ^{+} μ^{+} e^{-} e^{-}$ ( $Mu_{2}$ ). Using an extended stochastic variational method combined with the complex scaling method, we resolve the natural-parity $S$ - and $P$ -wave spectra. Near their respective $n = 2$ thresholds, all three trilepton systems exhibit Gailitis--Damburg sequences generated by $2 S$ and $2 P$ Stark mixing and the resulting inverse-square attraction. Although microscopically distinct from the Efimov effect, this mechanism produces the same inverse-square asymptotics and geometric scaling. The $Ps^{-}$ and $Mu^{-}$ systems exhibit resonance sequences of comparable density, whereas the $Mu_{2}^{+}$ produces a much denser spectrum, with 20 resolved members in the $^{3} P^{o}$ channel. In $Mu_{2}^{+}$ , the deeper states follow molecular Born--Oppenheimer configurations, while the near-threshold spectrum is governed by the atomic $Mu (2) + μ^{+}$ structure. In $Ps_{2}$ , coupling between threshold-degenerate configurations is essential for a near-threshold bound state. In $Mu_{2}$ , the Born--Oppenheimer organization of the resonance spectrum is channel dependent.
↳ physics.atom-phhep-exhep-phnucl-ex0 citations
19
Non-perturbative news from the conformal window
Álvaro Pastor-Gutiérrez🇯🇵
Dynamical symmetry breaking plays a crucial role in mass and scale generation. In QCD-like theories, its dependence on the number of fermion flavours determines the phase structure and the transition to the conformal regime. In this work, we employ the functional renormalisation group and the generalised flow equation to compute non-perturbative corrections, including momentum dependencies and field invariants essential for an adequate realisation of the global symmetry. As a consequence, the critical gauge coupling required for dynamical chiral symmetry breaking acquires a strong dependence on the number of flavours and increases sharply at $N_{f}^{crit} ≃ 7.30$ for $N_{c} = 3$ . This establishes a new picture of the conformal phase transition that challenges Miransky/BKT scaling and the existence of walking regimes, favours a first-order quantum phase transition, and points towards a critical region with exotic dynamics and symmetric fermion mass gaps.
↳ hep-thhep-lathep-ph0 citations
20
Wilsonian Cosmology: de Sitter (in)Stability
Jean Alexandre🇬🇧 · Lucien Heurtier🇬🇧 · Silvia Pla🇩🇪
We develop a (Wilsonian) functional-renormalisation-group framework for scalar cosmology in which quantum fluctuations of a scalar field are coarse-grained on cosmological spacelike hypersurfaces. Integrating out quantum fluctuations with wavelengths smaller than the Hubble radius $H (t)^{- 1}$ , we obtain an effective scalar potential $U (ϕ (t), H (t))$ that evolves in time. We derive a non-perturbative flow equation for this potential, together with the coupled set of (modified) Friedmann equations. We then apply this formalism to the simplest possible case of a de Sitter vacuum when the scalar field is at rest, in two situations which satisfy exactly our flow equation: $(i)$ A flat potential, for which we find that the only pure de Sitter solution is unstable and corresponds to a saddle point. $(ii)$ A quadratic potential with curvature $m^{2} > 0$ , for which we find that the presence of the mass term stabilises the system. The latter case leads to a de Sitter attractor either at the Hubble scale when the mass is larger than the Hubble scale at initial time, or by introducing a new attractor located at $H = m$ in the case the mass is smaller, which may be particularly relevant to the phenomenological study of dark energy and inflation theories.
↳ hep-thastro-ph.COgr-qchep-ph1 citation
21
Primordial spectra from modified Bekenstein-Hawking entropy law
Marco de Cesare🇮🇹 · Giulia Gubitosi🇮🇹 · Varun Kushwaha🇩🇪
Many approaches to quantum gravity predict logarithmic corrections to the Bekenstein-Hawking entropy. Within the spacetime-thermodynamic description of gravity, such corrections lead to modified gravitational field equations. We study their effect on primordial perturbations during standard single-field slow-roll inflation. We derive the evolution equation for the comoving curvature perturbation and show that it retains the standard Mukhanov--Sasaki form, with the quantum-gravity correction entering through the time-dependent effective frequency. We compute the scalar and tensor primordial spectra at next-to-next-to-next-to-leading order ( $N^{3} LO$ ) in the Hubble-flow parameters, keeping the leading contribution from the logarithmic correction. The scalar spectrum remains nearly scale invariant, but the quantum-gravity correction shifts its tilt and runnings. Free tensor modes still propagate as in general relativity, although on the quantum-gravity-corrected background. This different response of the two sectors shifts both the tensor-to-scalar ratio and the single-field consistency relation, which provide the starting point for tracing the model's signatures through the post-inflationary evolution and into the CMB.
↳ gr-qchep-phhep-th0 citations
22
Direct lattice QCD calculation of the $θ$ -induced CP-violating pion-nucleon coupling
Chuan-Yang Li🇨🇳 · Jun Hua🇨🇳 · Jian Liang🇨🇳 · Keh-Fei Liu🇺🇸 · Long-cheng Gui🇨🇳 · Jun Shi🇨🇳 · Nan Wang🇨🇳
We present the first direct lattice QCD determination of the $θ$ -induced CP-violating pion-nucleon-nucleon coupling $g ~_{π N N}$ . Using overlap valence fermions on three $2 + 1$ -flavor domain-wall ensembles at a single lattice spacing, we calculate the forward proton matrix element of the isovector pseudoscalar density in the $θ$ -vacuum to first order in $θ ˉ$ . The parity-mixing effect in the external nucleon states is included in the extraction. The cluster-decomposition error-reduction method is used to improve the statistical precision. A simultaneous extrapolation in the valence- and sea-pion masses, with model averaging over 7 forms based on the Akaike information criterion, gives $g ~_{π N N} = 0.0306 (56) (124) θ ˉ$ at the physical point. The first uncertainty includes the statistical and matrix-element-fit systematic uncertainties, whereas the second reflects the spread among the extrapolation forms. Within these uncertainties, the result is consistent with the indirect determination based on the strong neutron-proton mass splitting. The present precision is limited primarily by the extrapolation from the relatively heavy sea-pion masses.
↳ hep-lathep-ph1 citation
23
Deuterium Production in an Effective Field Theory Constructed from On-Shell Amplitudes
Tim M.P. Tait🇺🇸
We compute the deuterium-production reaction $n + p \to d + γ$ in an effective field theory whose degrees of freedom are the nuclear states themselves: the amplitude is assembled from on-shell three-point vertices, glued across its factorization channels, and completed by the contact terms consistent with the symmetries. The deuteron enters through the $d$ - $n$ - $p$ vertex, normalized to the measured asymptotic normalization coefficient. Rescattering of the nucleon pair is resummed dispersively, leaving two short-distance constants, an isovector magnetic and an electric dipole contact interaction. A joint Bayesian fit to the thermal capture measurements and the SLEGS photodisintegration data finds both of natural size and determines the thermonuclear rate to 0.22-0.24% across the nucleosynthesis window, including systematics spanning the defensible treatments of the SLEGS data and of the $P$ -wave rescattering. Truncating the expansion is bounded separately at 0.12%, of which the next order of contact terms -- degenerate with the two fitted constants -- supplies 0.03%, for a total theory uncertainty of 0.25-0.27%. Propagated through a BBN network, the rate shifts the predicted primordial deuterium by -0.06% and cuts this reaction's contribution to the D/H uncertainty from 0.089% to 0.050%, retiring it from the primordial D/H error budget for practical purposes.
↳ nucl-thastro-ph.COhep-phhep-th0 citations
24
Beyond $w_{0} - w_{a}$ and Phantom Crossing: Testing Models of Coupled Dark Sector
Kaynan R. de O. Pompeu · João Rebouças · Rogerio Rosenfeld🇧🇷
The combination of cosmic microwave background (CMB) measurements with distance measurements from baryon acoustic oscillations (BAO) and type Ia supernovae (SNIa) suggests that dark energy is dynamical, with an equation of state crossing the phantom divide at low redshifts. This feature can not be described within canonically normalized, minimally coupled, self-interacting scalar field models. We investigate the possibility of achieving phantom crossing by introducing an interaction in the dark sector such that the dark matter particle mass is dependent on the dark energy field $ϕ$ as $m \propto ϕ^{α}$ . We consider a self-interacting potential of the inverse power-law form $V \propto ϕ^{- β}$ . We implement this model both at the background and perturbative levels in a Boltzmann solver and use a bayesian framework to constrain its parameters using using CMB, BAO and SNIa data. We find best-fits that have similar goodness-of-fits as the commonly used phenomenological $w_{0} - w_{a}$ parameterization, providing a more fundamental understanding of the dark sector.
↳ astro-ph.COhep-ph0 citations
25
Time-Dependent Tunneling in the Thin-Barrier Limit
Tanmay Vachaspati🇺🇸 · Frank Wilczek🇺🇸 · Zara Yu
The usual WKB analysis for quantum tunneling applies when the tunneling action is large, as it is for tall, wide potential barriers. In contrast we analyze tunneling when the action is small, as it is for tunneling across a tall, thin barrier. We develop a perturbative analysis where the control parameter is the inverse of the area under the potential barrier and apply our technique to several examples in $1 + 1$ dimensions. In resonant situations for bound particles we find that the tunneling probability grows with time as $\propto t^{2}$ , while in non-resonant situations it grows linearly with time. We evaluate not only the tunneling probability but also the time-dependent tunneling wavefunction for a particle that escapes to infinity, {\it i.e.} from a quasi-bound state to the continuum.
↳ quant-phcond-mat.otherhep-phhep-th0 citations
26
Note on arithmetic structure of modulus vacua in flux compactifications
Yukiya Furuta🇯🇵 · Tatsuo Kobayashi🇯🇵 · Tomoyasu Kori🇯🇵 · Shuhei Miyamoto🇯🇵 · Ryusei Nishida🇯🇵 · Hajime Otsuka🇯🇵
We study modulus stabilization by background fluxes. The supersymmetric minima satisfy a holomorphic quadratic equation. As concrete examples, we consider $T^{6} / (Z_{2} \times Z_{2}^{'})$ orientifold model and a simple Calabi-Yau compactification. The modulus values show specific patterns. For example, they show the Farey sequence. The void structure appears around modulus vacua with high degeneracies. We find a correlation between the degeneracy and the void area. The modulus vacua are related by discrete Abelian symmetries generated by the Gauss composition law, which includes the CP symmetry. Spontaneous CP violation is also discussed.
↳ hep-thhep-ph0 citations
27
The fate of chiral symmetry in two-flavor matrix adjoint QC $_{2}$ D
Nirmalendu Acharyya🇮🇳 · Prasanjit Aich🇮🇳 · Sayan Bhakta🇮🇳 · Ranita Mudi🇮🇳 · Sachindeo Vaidya🇮🇳
In the matrix model of two-flavor adjoint QC $_{2}$ D, we study the low-lying states and their properties in the intermediate-to-strong (Yang-Mills) coupling regime. The model has a classical $S U (2)_{R}$ chiral symmetry and the eigenstates of the Hamiltonian can be organized in its irreps. We construct the energy eigenstates in presence of a chiral chemical potential $c$ using the variational techniques. We find that when $c = 0$ , the ground state is always a $S U (2)_{R}$ singlet, irrespective of the coupling strength $g$ . However, as $g$ is tuned from intermediate to strong coupling, the system under goes a crossover from a unique to a doubly degenerate ground state. The degeneracy in the strong coupling regime spontaneously breaks the axial $Z_{8}$ , while preserving the chiral symmetry. When $c \neq = 0$ , we find that there can be level crossings which correspond to quantum phase transitions (QPTs). Depending on the ground state, there are three possible phases. The $S U (2)_{R}$ symmetry is spontaneously broken in only one of these phases, and this phase can only emerge for intermediate $g$ with moderate values of $c$ . In the $g - c$ plane this phase corresponds to a narrow window, outside which $S U (2)_{R}$ is always preserved.
↳ hep-thhep-lathep-ph0 citations
28
The Primordial power spectrum from the largest to smallest CMB scales
Debabrata Chandra🇮🇳 · Dhiraj Kumar Hazra🇮🇳 · Arman Shafieloo🇰🇷 · Tarun Souradeep🇮🇳
We reconstruct the primordial power spectrum (PPS) across the full range of cosmological scales accessible to Cosmic Microwave Background (CMB) observations. Using the Modified Richardson--Lucy algorithm, we perform free-form reconstructions through deconvolution of Planck PR3 and PR4, Atacama Cosmology Telescope (ACT) DR6, and South Pole Telescope 3G (SPT-3G) D1 data. Across different regularization schemes, we find no evidence for significant deviations from a power-law primordial spectrum. The reconstructed spectra show a strong correlation between Planck and ACT, even at the level of localized features over their overlapping range, $0.07 < k < 0.14 Mpc^{- 1}$ , demonstrating consistency between the two observations. Using a complementary parametric Bayesian reconstruction, we find that the previously discussed preference for a blueward tilt in the ACT data at small scales is preferred only at the $1 σ$ level.
↳ astro-ph.COhep-phhep-th0 citations
29
CMB Birefringence from Axion String Networks Calibrated to an AMR Simulation
Mustafa A. Amin🇺🇸 · Mudit Jain🇬🇧 · Andrew J. Long🇺🇸 · Aden Pugsley · Moira Venegas🇺🇸 · Magdalena Whelley🇺🇸
A cosmological network of axion strings may exist in the Universe today. If axion-like particles couple to electromagnetism, such a network induces spatially varying birefringence in the polarization of the cosmic microwave background (CMB), which can be probed by current and next-generation CMB experiments. We calibrate a loop-crossing model against a large-scale adaptive-mesh-refinement (AMR) simulation of axion-string network dynamics in the early Universe and use the calibrated model to predict CMB birefringence from recombination to today. We find that the non-detection of anisotropic birefringence in CMB observations places a strong upper bound on the electromagnetic anomaly coefficient $A$ that enters the axion-photon coupling $g_{aγ γ} = - A α_{em} / π f_{a}$ . A joint analysis of available anisotropic birefringence measurements constrains $∣ A ∣ < 0.24$ at 95% C.L., which is independent of the Peccei-Quinn scale $f_{a}$ , assuming that the axions are hyperlight so that the network survives until today. This limit strongly restricts the high-energy embedding of hyperlight axions, excluding the minimal Grand Unified Theory prediction for the electromagnetic anomaly coefficient at high significance. In addition, we discuss the implications of an axion-string origin for the recently reported evidence of isotropic birefringence.
↳ astro-ph.COhep-ph0 citations
30
Testing the QGP Star Hypothesis: The oMEGACat BH-2 System as a Candidate Color-Superconducting Quark-Gluon Plasma Star
Herman J. Mosquera Cuesta🇪🇸
The recent discovery of a long-period binary system in the globular cluster $ω$ Centauri, oMEGACat BH-2 \citep{Whitaker2026}, provides an unprecedented opportunity to probe the true nature of compact dark objects. The system's massive, dark companion has been inferred to have a mass of $4.4 6_{- 1.01}^{+ 1.22} M_{⊙}$ , which places it in the ``mass gap'' between neutron stars and the canonical stellar-mass black holes. In this Letter, we explore the hypothesis that the oMEGACat BH-2 companion is not a classical black hole, but a stable, self-bound Quark-Gluon Plasma (QGP) star, as described by recent general relativistic models that incorporate Nonlinear Electrodynamics (NLED) and the asymptotic freedom of Quantum Chromodynamics (QCD) \citep{Mosquera2025}. We compare the inferred mass of the companion with the novel Mass-Radius ( $M$ - $R$ ) relation predicted by the QGP star model. We find that the inferred mass of the $ω$ Centauri object lies squarely within the wide mass spectrum predicted for hypermassive QGP stars ( $0$ to $> 7$ $M_{⊙}$ ). Although this consistency is not enough for claiming evidence, it suggests that oMEGACat BH-2 may be the first observed candidate for a QGP star, representing a stable, non-singular end-state of stellar collapse. We argue that future astrometric monitoring with JWST and radio-telescopes like FAST and SKA can further constrain the oMEGACat BH-2 orbital parameters. Meanwhile, gravitational-wave follow-ups for the $f$ and $g$ modes by observatories like LIGO, VIRGO, KAGRA, LISA, ET and CE can be crucial for distinguishing a classical black hole from the ``gravitational eternally collapsing `kompact' object'' (\GECKO) state of our QGP star model.
↳ astro-ph.HEgr-qchep-phnucl-th0 citations
31
Impact of Scale-dependent Primordial Non-Gaussianity on Scalar-induced Gravitational Waves
Alisha Marriott-Best🇬🇧 · Devanshu Sharma🇩🇪 · Anish Ghoshal🇬🇧 · Gianmassimo Tasinato🇬🇧
Scalar-induced gravitational waves (SIGWs) probe primordial curvature perturbations beyond cosmic microwave background scales, while primordial black holes (PBHs) probe the rare tail of the same statistics. We ask whether SIGW morphology can reveal scale-dependent primordial non-Gaussianity. We adopt the internal-leg separable kernel, $F_{NL} (k; q, k - q) = f ˉ_{NL} f (q) f (∥ k - q ∥)$ , and compute Gaussian, reducible, and connected contributions through $O (f ˉ_{NL}^{4})$ in the second-order tensor-source approximation. We compare persistent power-law running with a UV-matched tanh weight that saturates at high scalar momentum. Across narrow, finite-width, asymmetric, and multi-slope scalar spectra, running produces more than amplitude renormalization. Power-law running shifts the scalar support sampled by non-Gaussian convolutions, generating peak displacement, asymmetric shoulders, and persistent ultraviolet deformations. The tanh template instead produces a transition-localized modification and approaches a momentum-independent ultraviolet plateau. Analytical estimates of the perturbative hierarchy, weighted slopes, log-normal saddle displacement, peak shifts, and infrared scaling explain the trends and the enhanced sensitivity of the $O (f ˉ_{NL}^{4})$ sector. For localized sources with finite weighted moments, smooth running preserves the leading $k^{3}$ infrared behavior up to logarithmic corrections. Since the PBH mass scales as $M \propto k^{- 2}$ , preferential high-wavenumber weighting conditionally favors lower PBH masses in a narrow-support interpretation. Peak position, spectral curvature, shoulders, and ultraviolet slopes are diagnostics for PTAs, LISA, and third-generation observations, providing finite-order templates for primordial interactions on otherwise inaccessible scales.
↳ astro-ph.COhep-phhep-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE