Mon·Feb 16, 2026Monday·February 16, 2026

1. 01*

   Precise QCD Predictions for Hadron-in-jet Production in $e^{+}{e}^{-}$ Collisions

   Leonardo Bonino🇨🇭 · Aude Gehrmann-De Ridder🇨🇭 · Thomas Gehrmann🇨🇭 · Alexander Huss🇨🇭 · Francesco Merlotti🇨🇭 · Giovanni Stagnitto🇮🇹

   The production of identified hadrons inside jets in $e^{+}{e}^{-}$ annihilation allows for detailed studies of parton-to-hadron fragmentation functions in a clean environment. We compute hadron-in-jets production cross sections for $e^{+}{e}^{-}\to 2\mathrm{jets}$ and $e^{+}{e}^{-}\to 3\mathrm{jets}$ to next-to-next-to-leading order (NNLO) in perturbative QCD. By comparing with data from the ALEPH experiment, we demonstrate the implications of the newly computed theory predictions for precision phenomenology.

   hep-phPRL(2026)·4 citations
2. 02*

   Precision Physics with Muons : A Decade of Theoretical and Experimental Advances

   Bertrand Echenard🇺🇸 · Alexey A. Petrov🇺🇸

   The muon has been instrumental in establishing the Standard Model of particle physics and continues to play a key role in exploring the nature of New Physics. A global program is underway to enhance the discovery potential of a wide range of muon probes, with significant increases in sensitivity anticipated over the next decade. In this review, we examine recent experimental advancements in the study of muon decays, the determination of the muon magnetic and electric dipole moments, and the search for charged lepton flavor violating transitions. We explore the implications for scenarios of physics beyond the Standard Model, focusing on models involving light new particles, such as axions or hidden sectors. Opportunities from novel experimental concepts and proposal for new muon facilities are also discussed.

   hep-phhep-exnucl-ex2 citations
3. 03*

   Probing the Scalar Sector: Discovery Reach for Heavy Higgs Pairs at a $\sqrt{s}=6$ TeV Muon Collider in the 2HDM Alignment Limit

   Ijaz Ahmed🇵🇰 · M. Umar Farooq🇵🇰 · Farzana Ahmad🇰🇷 · Jamil Muhammad🇰🇷

   This study provides a comprehensive phenomenological investigation into the discovery potential of heavy Higgs boson pairs ($HH,HA,AA,H^{+}{H}^{-}$) at a $\sqrt{s}=6$~TeV Muon Collider. Utilizing the Two-Higgs-Doublet Model (2HDM) Type-I within the alignment limit ($\sin (\beta -\alpha )\approx 1$), we evaluate two primary benchmarks with degenerate scalar masses of 1000~GeV (BP1) and 2000~GeV (BP2). Theoretical calculations performed reveal that Type-I branching fractions to third-generation fermions remain uniquely independent of $\tan \beta$, providing a stable signal across the investigated parameter space. We demonstrate that the Muon Collider environment allows for the precise identification of high-multiplicity hadronic final states. A key finding of this research is that the signal processes yield distinctive topological signatures: an 8-jet state ($4j+4b$) for charged pairs and a highly complex 12-jet state ($8j+4b$) for neutral pairs ($HA/AA$). These signatures, combined with hard transverse momentum distributions and central pseudorapidity ($|\eta |\le 3$), allow for nearly absolute suppression of Standard Model backgrounds like $t\bar{t}$, $W^{+}{W}^{-}Z$, and $ZZZ$. At an integrated luminosity of 10~ab${}^{-1}$, we report a staggering statistical significance of 104,000 for the $H^{+}{H}^{-}$ channel and 3343 for the $HA$ channel in the BP1 scenario. Furthermore, total selection efficiencies were found to increase from approximately 20\% at BP1 to 47\% at BP2, suggesting that the decay products of heavier scalars are kinematically easier to resolve. We conclude that a 6~TeV Muon Collider offers an unparalleled discovery reach for the extended scalar sector, providing a definitive facility for probing physics beyond the Standard Model.

   hep-ph0 citations
4. 04*

   Towards a complete scheme of cosmological neutrino self-interactions: Collision term for a wide range of mediator masses

   Ivan Pérez-Castro🇲🇽 · Josue De-Santiago🇲🇽 · Gabriela Garcia-Arroyo🇲🇽 · Jorge Venzor🇲🇽 · Abdel Pérez-Lorenzana🇲🇽

   Neutrino self-interactions (NSI) offer a potential pathway to address anomalies in standard cosmology and explain existing cosmological tensions. In this work, we present a novel framework to obtain the neutrino--neutrino collision term within the Boltzmann hierarchy, incorporating both neutrino and mediator masses as free parameters. Our calculations encompass both Dirac-like and Majorana neutrinos and distinguish between two neutrino mass eigenstates. This work provides a valuable tool for future analyses, should a NSI signal be detected. Remarkably, our results show a smooth transition from the light to the heavy mediator approximation as the Universe cools down for non-resonant cases. Thus, for the widely studied heavy mediator, our new scheme eliminates the need to approximate at high redshifts when the temperature increases above the mediator mass, and it provides the tools to test the threshold of validity of the heavy mediator paradigm. While this work focuses on NSI mediated by a scalar particle, the presented framework could be adapted to a broader range of neutrino NSI and possibly to warm dark matter self-interacting scenarios.

   hep-phastro-ph.COJCAP(2026)·5 citations
5. 05*

   NNLL${}^{\prime }$ resummation of azimuthal decorrelation for boosted top quark pair production at the LHC

   Qian-Shun Dai🇨🇳 · Ming-Jun Liu🇨🇳 · Ding Yu Shao🇨🇳

   The precision program of the Large Hadron Collider (LHC) increasingly relies on the boosted regime, where top quark properties are probed at the TeV scale. However, the simultaneous presence of heavy quark mass effects and large logarithmic corrections from soft radiation poses a significant challenge for theoretical predictions. In this work, we develop a transverse momentum dependent (TMD) factorization and resummation framework for boosted top quark pair production in the back-to-back limit at the LHC. By employing a two step matching procedure, matching QCD through $\mathrm{SCET}+\mathrm{HQET}$ onto $\mathrm{SCET}+\mathrm{bHQET}$, we systematically resum large logarithms associated with both the top quark mass and the azimuthal decorrelation. A key component of our formalism is the first extraction of the two-loop ultra-collinear function, obtained via the refactorization of the fully differential massive soft function. This result completes the set of perturbative ingredients required to achieve ${\mathrm{NNLL}}^{\prime }$ accuracy for the azimuthal decorrelation distribution. Our framework establishes a new benchmark for heavy-quark TMD resummation in the boosted limit at hadron colliders.

   hep-phhep-exnucl-exnucl-thJHEP(2026)·1 citation
6. 06*

   Probing the isospin structure and low-lying resonances in ${\Lambda }_c^{+}\to n{\bar{K}}^0{\pi }^{+}$ decays

   Meng-Yuan Li🇨🇳 · Guan-Ying Wang🇨🇳 · Neng-Chang Wei🇨🇳 · De-Min Li🇨🇳 · En Wang🇨🇳

   The Cabibbo-favored decay ${\Lambda }_c^{+}\to n{\bar{K}}^0{\pi }^{+}$ offers a unique window to explore unresolved puzzles in the low-energy baryon spectroscopy and the isospin dynamics of the $\bar{K}N$ system. Recent experimental results present a, for now, contradiction: LHCb and Belle analyses of ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ suggest the $p{K}^{-}$ ($I=0$) component dominates, while the Beijing Spectrometer III (BESIII) hints at significant contributions from both isospin $0$ and $1$ in the $n{\bar{K}}^0$ system of ${\Lambda }_c^{+}\to n{K}_S^0{\pi }^{+}$. Furthermore, the measured branching fraction of ${\Lambda }_c^{+}\to n{K}_S^0{\pi }^{+}$ exceeds SU(3) symmetry predictions by a factor of 3-4, signaling strong contributions from low-lying resonances. In this work, we provide a theoretical analysis of ${\Lambda }_c^{+}\to n{\bar{K}}^0{\pi }^{+}$ within the coupled-channel chiral unitary approach, where the $N(1535)$ and $\Lambda (1670)$ can be dynamically generated. Our calculations show a narrow peak from $N(1535)$ in the ${\pi }^{+}n$ invariant mass spectrum and a distinct dip from $\Lambda (1670)$ in the ${\bar{K}}^{0}n$ spectrum. The dip structure is qualitatively consistent with the $\Lambda (1670)$ manifestation in $\bar{K}N\to \bar{K}N$ scattering, supporting its molecular interpretation. This study not only connects the experimental observations but also highlights ${\Lambda }_c^{+}\to n{\bar{K}}^0{\pi }^{+}$ as a crucial process to disentangle the nature of $N(1535)$ and $\Lambda (1670)$. Future precise measurements of this decay channel by the BESIII, Belle II, LHCb, and the proposed Super Tau-Charm Factory are strongly encouraged.

   hep-phPRD(2026)·2 citations
7. 07*

   Conservation laws and effective hadronization models

   Tony Menzo🇺🇸

   Hadronization models based on local string-breaking dynamics are typically Markovian by construction, yet the physical ensemble of final states is shaped by global constraints that couple the entire fragmentation trajectory. Recasting hadronization as a conditioned stochastic diffusion process provides a precise mathematical resolution to this tension. In particular, this language reveals explicitly that constraints stemming from conservation laws induce non-Markovian correlations between otherwise independent fragmentation steps, and that these correlations can be absorbed exactly into a renormalization of the local dynamics through a Doob $h$-transform. We develop this formalism for a $q\bar{q}$ string in the chiral limit, where the longitudinal-transverse factorization of the Lund kernel becomes exact, enabling systematic power counting and clean ultraviolet (UV)/infrared (IR) separation. The dynamics organize naturally into a tower of effective theories distinguished by the remaining string mass, spanning a UV fixed point with scale-invariant transport coefficients, an intermediate regime where transverse phase space induces controlled running, and an IR boundary layer where non-local effects enter at leading order. The tower exhibits genuine Wilsonian structure, including $\beta$-functions, anomalous dimensions, and systematic matching conditions. The resulting framework achieves a clean factorization of universal microscopic fragmentation dynamics from infrared constraint effects, and opens new directions for both the theoretical analysis and practical simulation of hadronization.

   hep-ph0 citations
8. 08*

   Resummation of threshold double logarithms in quarkonium fragmentation functions

   Hee Sok Chung🇰🇷 · U-Rae Kim🇰🇷 · Jungil Lee🇰🇷

   We develop a formalism for resumming threshold double logarithms that appear in fragmentation functions for production of heavy quarkonia. Threshold singularities appear in fixed-order calculations of quarkonium fragmentation functions in the nonrelativistic QCD factorization formalism due to radiation of soft gluons. Because of this, fixed-order quarkonium fragmentation functions are not positive definite, and can lead to unphysically negative cross sections. This problem can be resolved by resumming threshold logarithms to all orders in perturbation theory, which renders the fragmentation functions finite and ensures the positivity of cross sections. We present a detailed derivation of the resummation formalism and derive the formula for resummed quarkonium fragmentation functions, which can be computed entirely within perturbation theory without the need for nonperturbative model functions.

   hep-phPRD(2026)·2 citations
9. 09*

   Scale dependence of top-quark cross section at $e^{+}{e}^{-}$ colliders near production threshold at NNNLO

   Yuichiro Kiyo🇯🇵

   The top-quark threshold cross section at $e^{+}{e}^{-}$ colliders near production threshold is investigated. We study the scale dependence of the cross section for $\sigma (e^{+}{e}^{-}\to ttX$) near $\sqrt{s}\simeq 2m_t$ and discuss the theoretical accuracy of the NNNLO prediction. We report that a threshold scan at an $e^{+}{e}^{-}$ collider would allow a determination of the top-quark mass with an accuracy of order 30 MeV.

   hep-phJ.Subatomic Part.Cosmol.(2026)·0 citations
10. 10*

    Meson Form Factors

    Johan Bijnens (Lund)🇸🇪

    We give an introduction to and a short overview of light meson form factors. We first discuss the classical picture and how it then fits in with amplitudes in quantum field theory. We give a short overview of the main theoretical methods and then discuss pion, kaon, eta and eta' form factors.

    hep-phnucl-th0 citations
11. 11*

    Big Bang Nucleosynthesis and the Neutrino-Extended Standard Model Effective Field Theory

    Pieter Braat🇳🇱 · Jordy de Vries🇳🇱 · Jelle Groot🇳🇱 · Julian Y. Günther🇩🇪 · Juraj Klarić🇳🇱

    We study the impact of light GeV-scale heavy neutral leptons (HNLs) on Big Bang nucleosynthesis (BBN) in the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). We show that, based on very general considerations, BBN constraints complement laboratory searches at colliders, beam dumps, and neutrinoless double beta decay, by providing an upper bound on the cut-off scale of the effective field theory for HNL masses above $\sim$100 MeV. We identify target regions for future laboratory probes of the $\nu$SMEFT parameter space that is bounded from above and below.

    hep-phastro-ph.COhep-ex4 citations
12. 12*

    State-of-the-art cross sections for $t\bar{t}H$: NNLO+NNLL+EW predictions

    Anna Kulesza🇩🇪

    The most precise theoretical predictions for the total cross section for the associated production of a Higgs boson with a top-antitop quark pair at the LHC, first presented in \cite{Balsach:2025tth}, are reported. The calculation combines NNLO QCD corrections that include an approximation of the two-loop virtual contribution, with soft-gluon resummation at NNLL accuracy in two independent frameworks (SCET and direct QCD), and complete NLO electroweak corrections.

    hep-phJ.Subatomic Part.Cosmol.(2026)·0 citations
13. 13*

    Higher-order structure of Hamiltonian truncation effective theory

    Andrea Maestri🇮🇹 · Simone Rodini🇮🇹 · Barbara Pasquini (Pavia U. and INFN-Pavia)🇮🇹

    We study the Hamiltonian truncation for the two-dimensional $\lambda {\varphi }^4$ theory within the framework of Hamiltonian truncation effective theory, where truncation artifacts are mitigated through a systematic inclusion of corrective terms organized in inverse powers of the ultraviolet energy cut-off $E_{\max }$. Building on the leading-order matching program, we develop two complementary extensions. First, we derive compact all-order expressions for the local matching corrections to the mass and quartic coupling by resumming infinite classes of diagrams sharing fixed topologies within the local approximation. Second, we extend the non-local sector by computing the next-to-next-to-local corrections contributing at $\mathcal{O}(E_{\max }^{-4})$, following a continuum-first matching procedure, in which the effective corrections are computed in infinite volume and the spatial direction is subsequently re-compactified to obtain a discrete basis of free-Hamiltonian eigenstates on which the truncated operator construction is implemented. Our results show that an increasingly rich operator basis is necessary to describe the theory beyond leading order.

    hep-phhep-lathep-thPRD(2026)·2 citations
14. 14*

    Rotating synchrotron radiation: Photon emission from magnetized and rotating quark-gluon plasma

    Matteo Buzzegoli🇷🇴 · Sergiu Busuioc🇷🇴 · Jonathan D. Kroth🇺🇸 · Nandagopal Vijayakumar🇺🇸 · Kirill Tuchin🇺🇸

    This paper investigates the production of non-prompt photons originating from rotating synchrotron radiation (RoSyRa), specifically the emission of photons by a rigidly rotating quark-gluon plasma in thermal equilibrium, in the presence of an external magnetic field. We compute the non-prompt photon spectrum and its elliptic flow ($v_2$) at mid-rapidity. In particular, we investigate the finite volume effects. We find that at low transverse momentum, the magnetic field induces a significant $v_2$, while the plasma rotation boosts the synchrotron radiation of negatively charged quarks. These findings make RoSyRa a viable candidate mechanism to resolve the "direct photon puzzle."

    hep-phhep-thnucl-thPRD(2026)·3 citations
15. 15*

    Constraining ALP-Meson overlaps from $K\pi$ form factors

    Triparno Bandyopadhyay🇮🇳 · Subhajit Ghosh🇺🇸

    We present the first constraints on the overlaps between an Axion-like particle (ALP) and the ${\pi }^0$ and $\eta$ mesons from the analysis of the distortions to the $⟨K|\overline{s}{\gamma }^{\mu }u|\pi ⟩$ form factors. We demonstrate that these distortions can be tightly constrained by combining data from ${\tau }^{-}\to {\pi }^0{K}^{-}\nu$ and $K^{+}\to {\pi }^0{\ell }^{+}\nu$ decays, and go on to map the constraints to the ALP-meson overlaps. We establish that, in general, the ALP-meson and meson-ALP overlaps are different due to the presence of ALP-quark derivative couplings in the UV Lagrangian, and need to be treated separately. Using lattice results and BaBar, Belle, and NA48/2 data, we obtain exclusion limits on the overlaps and give projections for Belle II. Our techniques are independent of the branching ratios of the ALP, hence, robust against ALP decay channel assumptions. For masses of the ALP below 1 GeV, the bounds on the effective scale of the ALP physics extend to $\mathcal{O}$(TeV) for restricted regions of the parameter space for the ALP-$\pi$ and $\pi$-ALP overlaps. On the other hand, these bounds persist for extended regions of the parameter space for ALP-$\eta$ and $\eta$-ALP overlaps.

    hep-phhep-ex0 citations
16. 16*

    Profiling systematic uncertainties in Simulation-Based Inference with Factorizable Normalizing Flows

    Davide Valsecchi🇨🇭 · Mauro Donegà🇨🇭 · Rainer Wallny🇨🇭

    Unbinned likelihood fits maximize the information extracted from experimental data, yet their application in realistic high-dimensional analyses has been fundamentally bottlenecked by the prohibitive computational cost of profiling systematic uncertainties. Furthermore, current machine learning-based inference methods typically estimate scalar parameters, discarding complex high-dimensional correlations. To address this, we propose a general Simulation-Based Inference (SBI) framework that elevates the fit target from scalar parameters to a multivariate Distribution of Interest (DoI), a learnable, invertible transformation of the feature space. We employ Factorizable Normalizing Flows to model systematic variations as parametric deformations, preserving tractability without combinatorial explosion. Crucially, we develop an amortized training strategy that learns the conditional dependence of the DoI on nuisance parameters in a single optimization process, bypassing repetitive training during likelihood scans. To capture the finite-sample statistical variance of the neural network DoI, we introduce a Poisson-bootstrap ensemble, which we marginalize through an averaged likelihood to deliver a complete statistical-plus-systematic uncertainty budget within a single unbinned likelihood. Validated on a synthetic dataset emulating a high-energy physics measurement, our method demonstrates that rigorous, fully profiled unbinned measurements can now be extended to complete differential distributions. By turning the fit into a functional measurement, this approach offers a powerful, unifying framework for a broad range of tasks conventionally treated as distinct problems, from detector calibration and differential cross-sections to unfolding and continuous parameter estimation.

    hep-phphysics.data-anstat.ML3 citations
17. 17*

    Addressing the Hubble tension with Sterile Neutrino Dark Matter

    Debtosh Chowdhury🇮🇳 · Md Sariful Islam🇮🇳

    One of the promising dark matter (DM) candidates is a keV-scale sterile neutrino. In the early universe, the observed relic of the sterile neutrino DM is generated via the Dodelson-Widrow mechanism. However, this production scenario is severely constrained by various astrophysical observations. Many non-standard interactions between active (${\nu }_a$) and sterile (${\nu }_s$) neutrinos have been proposed to evade these astrophysical bounds. Here, we study sterile neutrinos in the context of a mass-varying scenario by coupling both active and sterile neutrinos to a scalar field. This novel mechanism opens up a new parameter space that generates the observed DM relic and addresses the Hubble tension. We find that the resulting parameter space can be fully probed by future X-ray missions.

    hep-phastro-ph.COhep-ex0 citations
18. 18*

    Lazarides-Shafi axion models as Dijkgraaf-Witten theories

    Motoo Suzuki🇮🇹 · Ryo Yokokura🇯🇵

    Axion models often face the domain wall problem, which threatens the standard big-bang cosmology. The Lazarides-Shafi mechanism attempts to resolve this by identifying degenerate vacua through a continuous gauge symmetry. We formulate a topological quantum field theory to isolate the essential structure of the mechanism and analyze its generalized symmetry structure, including higher-form symmetries and higher-group. This framework yields a master formula for computing the domain wall number and clarifies the higher-form symmetry conditions required for complete vacuum identification in a model independent way. Moreover, while a domain-wall-number-one scenario eliminates all higher-form global symmetries, the theory nevertheless exhibits a nontrivial four-group structure and realizes a symmetry-protected topological (SPT) phase.

    ↳ hep-thgr-qchep-phPRD(2026)·3 citations
19. 19*

    Sign-Switching Dark Energy: Smooth Transitions with Recent DESI DR2 Observations

    Beñat Ibarra-Uriondo🇪🇸 · Mariam Bouhmadi-López🇪🇸

    Sign-switching dark energy provides a novel mechanism for modifying the late-time expansion history of the Universe without invoking additional fields or finely tuned initial conditions. In this work, we investigate a class of background--level cosmological models in which the dark energy contribution changes sign at a transition redshift $z_{†}$, producing a sharp deviation from standard $\Lambda$CDM dynamics. We confront these models with a comprehensive set of cosmological observations, including Planck 18 cosmic microwave background (CMB) measurements, DESI DR2 Baryonic Acoustic Oscillation (BAO) data and the Pantheon+ $\&$ SH0ES Type Ia supernova sample (SN). Using a full Markov Chain Monte Carlo (MCMC) analysis, we find that the sign-switching scenario significantly alleviates the Hubble tension while obtaining better results when statistically comparing with $\Lambda$CDM, as quantified by the Akaike and Bayesian information Criteria. Although the model is explored only at the background level, the improvement in the inferred Hubble constant demonstrates that sign-switching dark energy offers a promising and physically economical pathway toward resolving late-universe discrepancies.

    ↳ astro-ph.COgr-qchep-phhep-thPhys.Dark Univ.(2026)·16 citations
20. 20*

    Symmetric teleparallel gravitational effects on solar neutrino oscillations

    Aysel Cetinkaya🇮🇩 · Muzaffer Adak🇮🇩 · Ozcan Sert🇮🇩 · Caglar Pala🇹🇷

    Neutrino oscillations probe the quantum gravity interface in unique ways. While gravitational effects on neutrinos are well studied in general relativity and torsion based geometries, the symmetric teleparallel regime where gravity stems solely from non-metricity, with zero curvature and torsion has remained uncharted. In this work, we perform the first analysis of neutrino oscillations in such a spacetime. Using the reduced Kerr metric in coincident gauge for the slowly rotating and weakly gravitating spherical Sun, we derive the Dirac Hamiltonian from the generalized Dirac equation and compute the accumulated phase of neutrino mass eigenstates. There are six free coupling constants in our model. Based on certain observational inputs, we inferred upper bounds on our arbitrary coupling constants. This allowed us to simplify the otherwise cumbersome calculations to some extent. Ultimately, we computed the phase differences that play a crucial role in solar neutrino oscillations and analyzed the contributions arising from our arbitrary coupling constants. Our results establish neutrino oscillations as a novel probe of non-metricity and open a new avenue for testing symmetric teleparallel gravity through astrophysical observations.

    ↳ gr-qchep-phhep-thJ.Phys.Conf.Ser.(2026)·2 citations
21. 21*

    CMB Spectral Distortions from Resonant Conversions in Atomic Dark Sectors

    Duncan K. Adams🇺🇸 · Jared Barron🇺🇸 · Bryce Cyr🇺🇸 · Xiuyuan Zhang🇺🇸

    Dark sectors consisting of atomic constituents (electrons, protons, and photons) offer a well-motivated extension to the Standard Model while providing multiple avenues for phenomenological study. In this work, we explore the impact of conversions between the dark and Standard Model photons in the primordial CMB spectral distortion epoch ($10^3\lesssim z\lesssim 10^6$). These conversions are resonantly enhanced when the induced thermal masses of both photonic species are equal, thus leading to the possibility that sizeable distortions can be produced. To this end, we solve the Boltzmann equation at early times to determine the (irreducible) freeze-in or freeze-out abundance of dark photons. This procedure also allows us to update the limits on generic milli-charged dark sectors using the ACT DR6 bound on the number of effective radiative degrees of freedom ($N_{\mathrm{eff}}$). By then modeling the evolution of the thermal masses in both sectors, we compute the primordial CMB distortion using the Landau-Zener formalism. We find that when the dark electron and proton are roughly similar in mass (the positronium limit), current spectral distortion data from the COBE/FIRAS instrument is able to rule out novel regions of parameter space. We also forecast bounds from the proposed FOSSIL satellite, finding that spectral distortions can also be used to probe the ultra-low dark electric charge regions of parameter space, which are difficult to investigate by other means.

    ↳ astro-ph.COhep-phPRD(2026)·1 citation
22. 22*

    Physical Predictions in Closed Quantum Gravity

    Yasunori Nomura🇺🇸 · Tomonori Ugajin🇯🇵

    Recent developments in gravitational path integrals indicate that the nonperturbative physical Hilbert space of a closed universe is one-dimensional within each superselection sector. This raises a basic puzzle: how can a unique quantum-gravity state give rise to semiclassical physics, measurement outcomes, and classical probabilities? In this paper, we develop a framework in which nontrivial and statistically stable predictions emerge despite the one-dimensionality of the fully constrained Hilbert space. The key idea is to extract physical predictions in an enlarged, unconstrained Hilbert space by conditioning on observational data. We show that partial observability -- reflecting the limited access of observers to the degrees of freedom of the universe -- suppresses ensemble fluctuations associated with microscopic structure in the gravitational path integral, thereby restoring semiclassical predictability with exponential accuracy. We formulate the construction explicitly including contributions from the Hartle--Hawking no-boundary state, define a gauge-invariant Hilbert space for observations via a density operator, and generalize the formalism to conditioning on histories, clarifying the emergence of classical probabilities and an effective arrow of time. Finally, we explore whether this framework can support a realistic cosmology and identify assumptions that the underlying theory of quantum gravity must satisfy.

    ↳ hep-thastro-ph.COgr-qchep-ph7 citations
23. 23*

    Resonant Axion-Photon Conversion in the Early Inspiral of Neutron Star Binaries

    D. Suárez-Fontanella🇪🇸 · M. Ángeles Pérez-García🇪🇸 · C. Albertus🇪🇸

    We consider the early binary neutron star inspiral phase as a scenario to probe environmental axion--photon resonant conversion. For this we approximately model the merger site electromagnetic fields as the superposition of two rotating dipolar stellar magnetic fields at the thousand--km scale when both magnetospheres are not largely distorted. We capture the time-sliced near-zone magnetospheric geometry relevant for axion--photon mixing. Plasma effects are incorporated through an effective Goldreich--Julian charge density, used to determine the effective plasma frequency and the location of resonant conversion surfaces. Our results show that axion--photon resonant conversion in binary magnetospheres mostly occurs on extended peanut-shaped surfaces whose global geometry evolves as the binary inspiral evolves. As a consequence, the total electromagnetic power emitted through axion--photon conversion exhibits a characteristic dependence on axion mass and a slow temporal modulation correlated with the gravitational wave frequency emission. This feature is potentially detectable for $m_a\in [50,170]\mu \mathrm{eV}$ and set $g_{a\gamma }\lesssim 10^{-11}\mathrm{Ge}{\mathrm{V}}^{-1}$ as it lies within the sensitivity limits of current or planned radio observation missions. In light of our results we discuss the opportunity of binary neutron star inspirals as time-dependent, multimessenger probes of axion physics, and motivate coordinated searches combining gravitational wave observations with radio and millimeter wavelength electromagnetic measurements.

    ↳ astro-ph.HEhep-phApJ·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.