The neutrino mass generation via conventional seesaw mechanism is realized at high scales around $O({10}^{14})\mathrm{GeV}$ with natural Yukawa couplings of $O(1)$, making the test of the neutrino seesaw a great challenge. It is intriguing to note that the neutrino seesaw scale is typically around the upper range of the cosmological inflation scale. In this work, we propose a new framework incorporating inflation and the neutrino seesaw in which the inflaton primarily decays into right-handed neutrinos after inflation. This decay process is governed by the inflaton interaction with the right-handed neutrinos that respects the shift symmetry. Through the neutrino seesaw mechanism, fluctuations of the Higgs field can modulate the inflaton decays and contribute to the curvature perturbation. We investigate the induced non-Gaussian signatures and demonstrate, for the first time, that such signatures provide an important means to directly probe the high scale of natural neutrino seesaw. We further analyze the interplay of the non-Gaussianity signatures with the low-energy neutrino experiments, and their interplay with the Higgs self-coupling measurements at the LHC and future colliders.

The recent detection of the ultrahigh-energy neutrino event KM3-230213A ($\sim 220\mathrm{PeV}$) by KM3NeT telescope poses a challenge to conventional astrophysical models, particularly in light of the absence of similar $\gtrsim 100\mathrm{PeV}$ events in IceCube data, despite its larger exposure. We propose a novel mechanism in which binary black hole mergers act as transient neutrino sources via gravitationally induced electroweak vacuum instability. In this scenario, the extreme spacetime curvature near the horizons during the final inspiral phase destabilizes the Higgs vacuum, triggering nucleation of true-vacuum bubbles. Collisions between these bubbles produce microscopic black holes that rapidly evaporate via Hawking radiation, emitting intense, short-lived bursts of neutrinos with energies exceeding 100 PeV. The resulting neutrino fluence follows a heavy-tailed distribution, allowing rare but highly luminous sources to account for events like KM3-230213A while remaining consistent with IceCube’s nondetections. This framework links gravitational wave sources to ultrahigh-energy neutrino production and suggests that future multimessenger observations may detect electromagnetic signatures from microscopic black hole evaporation.

Lattice Monte Carlo simulations and the functional renormalization group (RG) are powerful approaches that allow for quantitative studies of nonperturbative phenomena such as bound-state formation, spontaneous symmetry breaking, and phase transitions. While results from both methods have recently shown remarkable agreement for many observables, e.g., in quantum chromodynamics, an analysis of deviations in certain quantities turns out to be challenging. This is because calculations with the two methods are based on different approximations, regularizations, and scale fixing procedures. In the present work, we present a framework for a more direct comparison by formulating the functional RG approach on a finite spacetime lattice. This removes all ambiguities of regularization, finite-size, and scale fixing procedures in concrete studies. By investigating the emergence of spontaneous symmetry breaking and phase transitions in a $Z(2)$ scalar theory in $d=1$, 2, and 3 spacetime dimensions, we demonstrate at the example of the local potential approximation how this framework can be used to evaluate and compare the systematic errors of both approaches.

We consider a Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion model extended with two right-handed neutrino fields to realize the minimal type-I seesaw. In this $\nu \mathrm{DFSZ}$ scheme we systematically determine the simplest quark and lepton flavor patterns compatible with masses, mixing, and charge-parity violation data, realized by flavored U(1) Peccei-Quinn (PQ) symmetries. We discuss axion dark matter production in pre- and postinflationary cosmology in this context, and predictions for the axion couplings to photons and fermions. In particular, helioscopes and haloscopes are able to probe our models via their distinct axion-to-photon couplings, while in the quark sector the most stringent constraints on axion-fermion couplings are set by $K^{+}\to {\pi }^{+}+a$. Flavor-violating constraints in the lepton sector are not as relevant as those stemming from red giants and star cooling SN1987a that restrict the diagonal $ee$ and $\mu \mu$ axion couplings to charged leptons, respectively. We also obtain axion mass bounds for the most interesting models and discuss how minimal flavored PQ symmetries provide a natural framework to suppress flavor-violating couplings.

In this paper, we employ a bottom-up holographic QCD model to investigate the dissociation of charmonium states moving in a rotating medium by calculating their quasinormal modes. We begin by reviewing the holographic quarkonium spectrum at zero temperature. Then, we derive the equations of motion for heavy vector mesons propagating in a rotating plasma, separating the analysis into longitudinal and transverse directions relative to the wave vector. Additionally, we compute the charge diffusion constant in the rotating background and analyze the pole-skipping phenomenon, which emerges in the retarded Green’s function. Finally, we investigate the impact of rotation on the spin alignment of the $J/\psi$ state in the helicity frame, utilizing the spectral function obtained from the holographic framework.

We present a study of the rare charm meson decays $D^0\to K^{+}{K}^{-}{e}^{+}{e}^{-}$, ${\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$, and $K^{-}{\pi }^{+}{e}^{+}{e}^{-}$ using a $942{\mathrm{fb}}^{-1}$ dataset collected by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We identify $D^0$ candidates via the charge of the pion from $D^{*+}\to D^0{\pi }^{+}$ decays and normalize the branching fractions to $D^0\to K^{-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ decays. The branching fraction for decay $D^0\to K^{-}{\pi }^{+}{e}^{+}{e}^{-}$ is measured to be $(39.6\pm 4.5(\mathrm{stat})\pm 2.9(\mathrm{syst}))\times {10}^{-7}$, with the dielectron mass in the $\rho /\omega$ mass region $675<m_{ee}<875\mathrm{MeV}/c^2$. We also search for $D^0\to h^{-}{h}^{(\prime )+}{e}^{+}{e}^{-}$ ($h^{(\prime )}=K$, $\pi$) decays with the dielectron mass near the $\eta$ and $\varphi$ resonances, and away from these resonances for the $K^{+}{K}^{-}{e}^{+}{e}^{-}$ and ${\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ modes. For these modes, we find no significant signals and set 90% confidence level upper limits on their branching fractions at the $\mathcal{O}({10}^{-7})$ level.

In this article, we extend the horizon brightened acceleration radiation (HBAR) framework, originally introduced by Marlan Scully et al. in [Proceedings of the National Academy of Sciences Vol. 115, pp. 8131 (2018)], to the causal diamond (CD) spacetime. We study a cloud of two-level atoms, injected at random times in the asymptotic past of the CD, freely falling toward its causal horizon and emitting scalar radiation via a weak dipole coupling to a quantum field. In the near-horizon region, an emergent conformal symmetry—captured by conformal quantum mechanics (CQM)—governs the field dynamics and allows analytic control of the emission process. We find that the radiation spectrum is thermal, with temperature $T_D=1/(\pi \alpha )$, and that the associated von Neumann entropy flux reproduces the entropy production of the radiation field. These results demonstrate that the causal horizons of the CD spacetime effectively act as a topological thermal reservoir, with thermal properties arising entirely from the global causal structure rather than from underlying microscopic degrees of freedom, highlighting that the validity of the HBAR framework is fundamentally tied to the existence of causal horizons, independent of the presence of a black hole.

We renormalize the Gross-Neveu-Yukawa model with an $O(N)$ symmetry to $\mathcal{O}({\epsilon }^5)$ in $d=4-\epsilon$ dimensions and determine the anomalous dimensions of the fermion and scalar fields, $\beta$ functions as well as the scalar field’s mass operator. These are used to construct several $N$-dependent critical exponents relevant for quantum transitions in semimetals and in particular those connected with graphene in three dimensions when $N=2$. Improved exponent estimates for scalar fermion transitions on a honeycomb lattice, when $N=1$, as well as for $N=5$ are also given to compare with results from other techniques such as the conformal bootstrap.

Analog gravity experiments, such as those realized in Bose-Einstein condensates, often aim at simulating cosmological pair production due to the dynamical expansion of the Universe. However, these experiments have a start and an end, which introduces unavoidable transitions out of and into static regimes that alter the intended expansion profile. We show that the resulting particle spectra can be overwhelmingly dominated by these transition periods, which calls for a careful interpretation of experimental outcomes. In prospective Schwinger effect experiments, by contrast, transition effects do not dominate particle production, and such a reinterpretation may not be necessary.

In this work, the dynamics of a dust shell in an effective theory of spherically symmetric gravity containing quantum corrections from loop quantum gravity is investigated. To provide a consistent framework for including the dust, we go beyond the standard formulation of the effective theory by introducing an action that includes not only the effective Hamiltonian constraint, but also the diffeomorphism constraint, along with appropriate gauge-fixing and boundary terms. By adding the dust shell action and substituting vacuum solutions for the interior and exterior regions, we derive a reduced action in which only the shell radius $\mathfrak{x}$ and the exterior black hole mass appear as dynamical variables. Varying the reduced action yields the evolution equation for $\mathfrak{x}$, which is then solved numerically to explore the dynamical properties of the dust shell and the continuity properties of the metric. Finally, our approach is compared with previous studies to highlight key differences and improvements.

One of the most important discoveries in cosmology is the accelerated expansion of the Universe. Yet, the accelerated expansion has only ever been measured indirectly. Redshift drift offers a direct observational probe of the Universe’s expansion history, with its sign revealing whether there has been acceleration or deceleration between source and observer. Its detection will mark a major milestone in cosmology, offering the first direct measurement of an evolving expansion rate. Given its epistemic importance, it is essential to understand how its measurements can be biased. One possibility of bias comes from cosmological structures. However, theoretical estimates of such effects are difficult to obtain because computing redshift drift in general inhomogeneous cosmologies is computationally demanding, requiring the solution of 24 coupled ordinary differential equations. In this work, we use Lemaitre-Tolman-Bondi Swiss-cheese models to show that only the two dominant contributions are needed to achieve percent-level accuracy up to $z=1$. This allows the reduction of the full system of 24 ODEs to the standard null geodesic equations, significantly simplifying the calculation. Although our analysis is based on idealized Swiss-cheese models with spherical structures, we expect that similar simplifications apply to more complex scenarios, including cosmological N-body simulations. Our analysis thus underpins a practical and robust framework for efficient redshift drift computations applicable to a wider range of inhomogeneous cosmologies.

Ever since the Planck satellite measured the cosmic microwave background (CMB) down to arcminute angular scales, the mismatch between the CMB-inferred value of the Hubble constant and the value inferred from the distance ladder (i.e., the Hubble tension) has been a growing concern and is currently at the $\sim 6\sigma$ level. There are a handful of proposed mechanisms operating in the early Universe which have shown some promise in resolving the Hubble tension. These mechanisms are expected to leave a measurable impact on the smallest-scale CMB anisotropy, deep in the damping tail. Using current CMB data, baryonic acoustic oscillation data, and the luminosities of type Ia supernovae as a baseline, we compute the predicted small-scale CMB power spectra for a characteristic set of these models. We find that near-future CMB data should be able to distinguish some but not all of the investigated models from the core cosmological model, $\mathrm{\Lambda }\mathrm{CDM}$.

High-precision astrometry offers a promising approach to detect low-frequency gravitational waves, complementing pulsar timing array (PTA) observations. We explore the response of astrometric measurements to a stochastic gravitational wave background (SGWB) in synergy with PTA data. Analytical, covariant expressions for this response are derived, accounting for the presence of a possible dipolar anisotropy in the SGWB. We identify the optimal estimator for extracting SGWB information from astrometric observations and examine how sensitivity to SGWB properties varies with the sky positions of stars and pulsars. Using representative examples of current PTA capabilities and near-future astrometric sensitivity, we demonstrate that cross-correlating astrometric and PTA data can improve constraints on SGWB properties, compared to PTA data alone. The improvement is quantified through Fisher forecasts for the SGWB amplitude, spectral tilt, and dipolar anisotropy amplitude. In the future, such joint constraints could play a crucial role in identifying the origin of SGWB signals detected by PTAs.

Gravitational-wave (GW) emissions from core-collapse supernovae (CCSNe) provide insights into the internal processes leading up to their explosions. Theory predicts that CCSN explosions are driven by hydrodynamical instabilities like the standing accretion shock instability or neutrino-driven convection, and simulations show that these mechanisms emit GWs at low frequencies ($\lesssim 0.25\mathrm{kHz}$). Thus, the detection of low-frequency GWs, or lack thereof, is useful for constraining explosion mechanisms in CCSNe. This paper introduces the dedicated-frequency framework, which is designed to follow up GW burst detections using bandpass analyses. The primary aim is to study whether low-frequency (LF) follow-up analyses, limited to $\le 256\mathrm{Hz}$, constrain CCSN explosion models in practical observing scenarios. The analysis dataset comprises waveforms from five CCSN models with different strengths of low-frequency GW emissions induced by standing accretion shock instability and/or neutrino-driven convection, injected into the Advanced LIGO data from the third observing run (O3). Eligible candidates for the LF follow-up must satisfy a benchmark detection significance and are identified using the coherent WaveBurst (cWB) algorithm. The LF follow-up analyses are performed using the BayesWave algorithm. Both cWB and BayesWave make minimal assumptions about the signal’s morphology. The results suggest that the successful detection of a CCSN in the LF follow-up analysis constrains its explosion mechanism. The dedicated-frequency framework also has other applications. As a demonstration, the loudest trigger from the SN 2019fcn supernova search is followed up using a high-frequency analysis, limited to $\ge 256\mathrm{Hz}$. The trigger has negligible power below 256 Hz, and the high-frequency analysis successfully enhances its detection significance.

We investigate the causality and stability of the relativistic theory of magnetohydrodynamics derived in [Phys. Rev. D 109, 096021 (2024)] to describe a locally neutral two-component plasma of massless particles. We show that this formalism is linearly causal and stable around global equilibrium, for any value of the magnetic field, and discuss its qualitative differences to the traditional Israel-Stewart formalism in the linear regime. Finally, we compare this framework with the magnetohydrodynamic model used in the study of astrophysical plasmas, in which only the longitudinal component of the shear-stress tensor is considered. We discuss the domain of applicability of this type of framework in the context of ultrarelativistic heavy-ion collisions.

We develop and test a spectral-density analysis method, based on the introduction of smeared energy kernels, to extract physical information from two-point correlation functions computed numerically in lattice field theory. We apply it to a $Sp(4)$ gauge theory with fermion matter fields transforming in distinct representations, with $N_{\mathrm{f}}=2$ Dirac fermions in the fundamental and $N_{\text{as}}=3$ in the 2-index antisymmetric representation. The corresponding continuum theory provides the minimal candidate model for a composite Higgs boson with partial top compositeness. We consider a broad class of composite operators, that source flavored mesons and (chimera) baryons, for several finite choices of lattice bare parameters. For the chimera baryons, which include candidate top-quark partners, we provide the first measurements, obtained with dynamical fermions, of the ground state and the lowest excited state masses, in all channels of spin, isospin, and parity. We also measure matrix elements and overlap factors, that are important to realize viable models of partial top compositeness, by implementing an innovative way of extracting this information from the spectral densities. For the mesons, among which the pseudoscalars can be reinterpreted to provide an extension of the Higgs sector of the Standard Model of particle physics, our measurements of the renormalized matrix elements and decay constants are new results. We complement them with an update of existing measurements of the meson masses, obtained with higher statistics and improved analysis. The analysis software is made publicly available, and can be used in other lattice studies, including application to quantum chromodynamics.

The data behavior of the pion-photon transition form factor (TFF) is discussed using a nonlinear mathematical model with two parameters $B$ and $C$. Analysis shows that the model’s inherent inhibition provides a precondition for the asymptotic saturation of the TFF in agreement with perturbative quantum chromodynamics (QCD). Integral to this derivation is the use of a novel fundamental relation between the half-saturated TFF and its asymptotic limit given by $B$. This helps avoid the determination of the location of the TFF at infinite momentum by estimating instead the maximum slope of the curve at $Q^2=C$. In conjunction with the $1\sigma (B,C)$ confidence ellipse, this framework provides an improved fit to the Belle data by setting stronger constraints on the fitting parameters and taking into account the sensitivity to third-party events below Belle’s kinematic coverage. Without inhibition, the slope of the TFF curve would continue to grow so that saturation toward the asymptotic QCD limit would not be achieved. In order to compare the key features of TFF fit models to upcoming high-precision data in a standardized way, a conformity protocol in terms of QCD-based criteria is worked out. Adopting a broader perspective, we show that the asymptotic saturation of an inhibited TFF fit curve is analogous to a mechanical system driven by a feedback-loop mechanism in control theory.

The substructure of jets in quantum chromodynamics (QCD) has garnered significant attention with the advent of infrared- and collinear-safe clustering algorithms and observables. A key question emerging from these studies is how in-jet emissions at soft and hard energy scales, across collinear and wide angles relative to the emitter, differ with the mass of the emitting parton. The Lund jet plane (LJP) is a perturbatively well-defined substructure observable that maps the radiation pattern of jets onto a plane, visually distinguishing emissions with different kinematic properties. Comparing LJP for jets containing hadrons of low versus high mass enables the testing of QCD splitting functions from first-principles calculations across both soft and hard regimes and at different radiation angles. This article presents the first measurement of the LJP for light-quark-enriched and beauty-initiated jets at a center-of-mass energy of 13 TeV at LHCb. This marks the first direct observation of the dead-cone effect in beauty-quark jets, measured in the collinear region of the LJP.

The finiteness of the entanglement entropies between disjoint subsystems enables us to show that the dynamical equation of the entanglement entropy in ${\mathrm{CFT}}_2$ is precisely the three-dimensional Einstein equation. We establish a profound relation between the cosmological constant and ${\mathrm{CFT}}_2$ entanglement entropy. Thus, entanglement entropies induce internal gravitational geometries in ${\mathrm{CFT}}_2$. Extracting the dual metric from an entanglement entropy becomes a straightforward procedure. Remarkably, we discover that the renormalization group equation is a geometric identity.

We compare LHCb measurements of $J/\psi$ and $\psi (2S)$ transverse-momentum distributions within jets with QCD calculations, which may be crucial in understanding the quarkonium production mechanism. Our theoretical calculations are based on the fragmenting jet function formalism, while the nonperturbative formation of quarkonia is described by the nonrelativistic QCD factorization formalism. We include the newest refinements in the perturbative calculation including resummation of threshold and Dokshitzer-Gribov-Lipatov-Altarelli-Parisi logarithms. We find that the $\psi (2S)$ data have the potential to discriminate between the different production mechanisms proposed in the literature.