We present the first experimental search for the $N$-naturalness tower of neutrinos using a global analysis of publicly available neutrino data. As a potential solution to the hierarchy problem, the $N$-naturalness model employs a varying Higgs mass parameter among $N$ dark sectors and encodes the required fine-tuning of the placement of the sectors in a parameter $r$. We report exclusion limits on the parameter space ($r$, $N$), for normal and inverted ordering and in case the neutrino is Majorana or Dirac. In the case of a Majorana neutrino, we can rule out $N\le {10}^4$ sectors with $r\ge 0.1$. This is particularly exciting as it shows that a gauge and gravitational unification around $M_{\mathrm{GUT}}$, which is a benchmark scenario of the $N$-naturalness framework with $N={10}^4$ without fine-tuning, is ruled out by neutrino experiments.

We present an $SU(12)\times SU(2{)}_L\times U(1{)}_R$ model unifying $SU(9)$ quark color-flavor with $SU(3)$ lepton flavor as a flavorful alternative to conventional theories of unification. We begin in the ultraviolet with a single Yukawa shared by the unified up-type quarks and neutrinos and no further new fermions. We show that gauged quark color-flavor and lepton-flavor instantons dynamically generate the bottom and tau Yukawas, which implements a massless quark solution to the strong $CP$ problem and sets up a flavored type-I seesaw mechanism. Only two new scalar irreps are needed for the symmetry-breaking steps, which include quark color-flavor deconstruction and then infrared reunification, and the Standard Model (SM) gauge group in this theory emerges as $G_{\mathrm{SM}}=\frac{SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y\times {\mathbb{Z}}_{18}^X}{{\mathbb{Z}}_3\times \mathrm{\Gamma }\times {\mathbb{Z}}_3}$, where $\mathrm{\Gamma }\in \{1,{\mathbb{Z}}_2\}$ is the electroweak global structure and there is a discrete gauge symmetry $X=B-3(L_i+L_j-L_k)$ which brings additional ${\mathbb{Z}}_3$ global structure to the SM. This gauge symmetry acts as a flavorful upgrade of the ${\mathbb{Z}}_{18}^{B+L}$ anomaly-free global symmetry of the SM and stabilizes the proton absolutely. Noninvertible chiral symmetry breaking is crucial to our model, and we discuss the rich spectrum of emergent generalized symmetries and topological defects appearing at various stages. In the infrared, the novel shared quotient between continuous and discrete groups links the one-form and two-form global symmetries of the Standard Model.

We revisit an anomaly-free extension of the Standard Model viz. the gauged $L_{\mu }-L_{\tau }$ model in the Dirac framework, where the local $U(1{)}_{L_{\mu }-L_{\tau }}$ symmetry breaks and gives rise to a new gauge boson $Z^{\prime }$ and corresponding gauge coupling $g_{\mu \tau }$. Three additional heavy vectorlike fermions, three light right-handed neutrinos and two heavy singlet scalars are added to complete the model framework for Dirac neutrinos. Another singlet vectorlike fermion is added with a new gauge charge, which serves as a viable dark matter (DM) candidate, and the correct relic abundance is obtained via the resonance effect. The resonance effect triggers early kinetic decoupling of the DM candidate, which significantly influences the cosmological sector of this study. The parameter space is considered after satisfying the current bounds on $M_{Z^{\prime }}$ and the gauge coupling $g_{\mu \tau }$. The influence of dark radiations coming from the additional light degrees of freedoms are studied in connection with the dark matter. After imposing the relevant theoretical and experimental constraints, the viable parameter space is found to be significantly restricted while remaining accessible to ongoing and near-future experiments. The framework provides a consistent setting in which neutrino masses, dark matter, and cosmological observables can be studied simultaneously. In particular, we identify viable regions of the parameter space that satisfy the constraints from neutrino masses, dark matter relic abundance, and cosmological observables.

Using forward matrix elements of local leading-twist operators, we present a determination of the isovector third Mellin moments $⟨x^2⟩$ of nucleon unpolarized, polarized, and transversity parton distribution functions. Two lattice QCD ensembles at the physical pion mass are used, which were generated using a tree-level Symanzik-improved gauge action and $2+1$ flavor tree-level improved Wilson clover fermions coupling via two-level HEX smearing. Leveraging a wide set of operators, two extraction methods for the matrix elements, and the automatic inclusion of model uncertainties via bootstrapped model averages, we extract values of the third Mellin moments. This is the first direct calculation of these observables performed at the physical pion mass.

We derive the pertinent chiral potentials for charmed vector meson interactions with light pseudoscalar bosons in a relativistic U(3) chiral effective field theory up to next-to-leading order. Predictions for the $S$- and $P$-wave scattering lengths are obtained for all the relevant elastic channels. A comparison with the most recent—and currently the sole—lattice QCD data on the $S$-wave $I=1/2$ $D^{*}\pi$ scattering length at a pion mass of 391 MeV reveals good agreement, thereby validating the estimation of low-energy constants via heavy quark spin symmetry. Within the relativistic formalism, we confirm that the $D_{s1}(2460)$ can be identified with a bound-state pole, while the $D_1(2430)$ corresponds to the interplay of two poles: a lower one on the second Riemann sheet and a higher one on the third Riemann sheet. We show that the $D_{s1}(2460)$ and the lower $D_1(2430)$ pole originate from the same flavor SU(3) triplet, whereas the higher $D_1(2430)$ pole belongs to the SU(3) sextet. All these states are not of $\overline{q}q$ nature, as they flow to complex infinity in the large $N_C$ limit. Our results provide quantitative benchmarks for future lattice QCD and experimental studies, particularly those using femtoscopy.

Employing a cutting-edge bootstrap method, we analytically compute the three-loop pentagonal Wilson loop with Lagrangian insertion in planar $\mathcal{N}=4$ super-Yang-Mills theory. Via a conjectured duality, this provides the first prediction for the maximally transcendental part of the four-loop five-point all-plus amplitude in pure Yang-Mills theory. Our starting point is an ansatz that encodes the known leading singularities of this object, as well as the relevant function space. The latter has become available only recently, thanks to an analytic computation of all three-loop five-point planar massless Feynman integrals. We determine the coefficients in the ansatz by imposing physical constraints. This includes a near-collinear expansion, which so far has not been applied to this quantity. Taken together, the constraints allow us to uniquely determine the symbol of the answer. We verify the symbol result by an independent integral reduction calculation, which moreover yields the full function-level answer.

Wave propagation in periodically time-dependent media can exhibit driven mode conversion that is absent in static or adiabatic descriptions. We show that coherent axion dark matter provides an intrinsic realization of this dynamics for photons propagating in a magnetic field. The background’s periodic birefringence continuously rotates the photon polarization and thereby drives magnetic photon-axion mixing. Using Floquet theory, we derive resonant photon-axion conversion when integer harmonics of the axion oscillation frequency compensate the dispersion mismatch, ${\mathrm{\Delta }}_{\gamma }-{\mathrm{\Delta }}_a\approx n{m}_a$ with $n\in \mathbb{Z}$. This resonance enables efficient mixing far from conventional level crossing and is lost when the periodic drive is averaged out of the propagation Hamiltonian. The resulting conversion is bounded and unitary, distinct from parametric instability or axion decay. Our framework describes photon propagation in coherent oscillating axion backgrounds and predicts characteristic polarization signatures, which we illustrate in a blazar environment.

In this paper, we present a strategy to decode decay amplitudes with different weak phases in two-body charmed baryon decays, addressing a long-standing challenge to understanding $CP$ violation in this sector. Using $SU(3)$ flavor symmetry, we disentangle the amplitudes defined through $M={\lambda }_s{A}_s+{\lambda }_b{A}_b$ (${\lambda }_i=V_{ui}{V}_{ci}^{*}$), enabling a data-driven determination of their relative hierarchy across Cabibbo-favored, singly, and doubly Cabibbo-suppressed modes. Applying this framework to current data, we find that the ratio $A_b/A_s$ is approximately 100 times larger than expectation of $\mathcal{O}(1)$ at $2.1\sigma$ level. This unexpected pattern may be accommodated by $SU(3)$ breaking effects, but it can also point to new physics. We further show that the Lee-Yang parameters provide an independent and complementary probe. To resolve this ambiguity in the origin of the enhancement, we propose a decisive discriminator using decay modes insensitive to large $SU(3)$ breaking, in particular ${\mathrm{\Xi }}_c^0\to p{K}^{-}$ and ${\mathrm{\Xi }}_c^0\to {\mathrm{\Sigma }}^{+}{\pi }^{-}$ as golden channels. Measurements of these modes will distinguish between symmetry breaking effects and new physics, establishing a clean pathway to probe $CP$ violation in the charm baryon sector.

Hawking radiation is a fundamental result of quantum field theory in curved spacetime, yet its direct observation remains beyond current experimental capabilities. Circuit quantum electrodynamics provides a practical platform for realizing analog systems where Hawking-like radiation may be studied under controlled laboratory conditions. In this work, we analyze two superconducting-circuit analogs of Schwarzschild black holes: a tunable dc-superconducting quantum interference device transmission line and a superconducting nonlinear asymmetric inductive element–based transmission line supporting solitonic solutions of the Korteweg–de Vries equation. We investigate the conditions under which these architectures can generate an observable Hawking temperature and study the impact of dissipation and thermal noise using an open quantum systems approach. To assess the observability of the Hawking signal, we propose complementing particle-number measurements with estimates of the Hilbert-Schmidt distance to the thermal bath. Our analysis establishes practical detectability thresholds and shows that Hawking temperatures above approximately 73 mK remain distinguishable under realistic experimental conditions. While the tunable transmission line architecture can reach temperatures of about 113 mK and therefore appears more viable, the solitonic model requires further optimization and more demanding experimental conditions.

We analyze entanglement generated by the Schwinger effect using a mode-by-mode formalism for scalar and spinor QED in constant backgrounds. Starting from thermal initial states, we derive compact, closed-form results for bipartite entanglement between particle-antiparticle partners in terms of the Bogoliubov coefficients. For bosons, thermal fluctuations enhance production but suppress quantum correlations: The logarithmic negativity is nonzero only below a (mode-dependent) critical temperature $T_c$. At fixed $T$, entanglement appears only above a critical field $E_{\text{entang}}$. For fermions, we observe a qualitatively different pattern: The fermionic logarithmic negativity is nonvanishing at finite temperature, and is monotonically suppressed by thermal noise. As a function of the electric field, it is nonmonotonic, featuring a temperature-independent optimal field strength $E_{*}$ and decreasing on both sides of the maximum. We give quantitative estimates for analog experiments, where our entanglement criteria convert directly into concrete temperature and electric-field constraints. These findings identify realistic regimes where the quantum character of Schwinger physics may be tested in the laboratory.

The Brown-York quasilocal energy is traditionally obtained from the Hamilton-Jacobi formulation of general relativity as the boundary contribution to the gravitational Hamiltonian. In the present work we investigate whether the same boundary geometry also appears in the dynamics of freely falling particles. Starting from the autoparallel equation, we derive the normal projection of the geodesic equation with respect to the Brown-York boundary foliation. The resulting expression naturally separates into a geometric contribution involving the combination $k-\mathrm{\Theta }$, a kinematical term associated with the particle motion, and a mixed observer/particle contribution determined by the foliation geometry. The combination $k-\mathrm{\Theta }$ is free of the reference-subtraction ambiguity inherent in integrated quasilocal energies. For a time-symmetric foliation $K_{ij}=0$, and for geodesic configurations stationary with respect to the observer congruence, ${\pounds }_u\beta =0$, the mixed observer/particle term vanishes. In Schwarzschild spacetime the remaining equation reproduces the Newtonian inverse-square law in the weak-field limit. The result may be interpreted geometrically as arising from the mismatch between the spatial embedding of a closed two-surface and the embedding of its timelike evolution in spacetime. We further derive the normal variation of the referenced Brown-York energy and show that, for Schwarzschild spheres, it satisfies the exact relation $-d{E}_{\mathrm{BY}}/ds=E_{\mathrm{BY}}N(1+N{)}^{-1}(k-\mathrm{\Theta })$, thereby relating the acceleration term entering the projected geodesic equation directly to the radial variation of the integrated quasilocal energy. The analysis does not derive the geodesic equation from the Brown-York energy functional. Rather, it demonstrates that the same boundary geometry underlying Brown-York quasilocal energy also governs the normal component of free-fall dynamics, thereby establishing a direct geometrical connection between Hamiltonian boundary geometry and geodesic motion.

We investigate the exceptional points (EPs) and their pseudospectra in black hole perturbation theory. By considering a Gaussian bump modification to the Regge-Wheeler potential with variable amplitude, position, and width parameters, $(ϵ,d,{\sigma }_0)$, a continuous line of EPs (exceptional line, EL) in this three-dimensional parameter space is revealed. Notably, the EL exhibits an anisotropic spectral response: parameters migrating along the EL direction leaves the coalesced QNM spectra nearly unchanged, while moving parameters away from the EL induces the characteristic ${\epsilon }^{1/2}$ scaling, highlighting the directional nature of spectral instability in exceptional structures. We find that the vorticity $\nu =\pm 1/2$ and the Berry phase $\gamma =\pi$ for loops encircling the EL, while $\nu =0$ and $\gamma =0$ for those do not encircle the EL. In the neighborhood of an eigenvalue, through matrix perturbation theory, we show that the $\epsilon$-pseudospectrum contour size scales as ${\epsilon }^{1/q}$ at an EP, where $q$ is the order of the largest Jordan block of the Hamiltonian-like operator associated with that eigenvalue, contrasting with the linear $\epsilon$ scaling at non-EPs. Numerical implements confirm this observation, demonstrating enhanced spectral instability at EPs for non-Hermitian systems including black holes.

The quasinormal modes of black holes play various important roles in gravitational wave theory, signal modeling, and data analysis; however, there remain open questions about their mathematical properties. Aspects of classical polynomial theory have been proposed as a framework to investigate quasinormal mode orthogonality and completeness. We have recently presented a class of polynomials that are “natural” to quasinormal modes in that they are restricted by the quasinormal mode boundary conditions, and exactly tridiagonalize Teukolsky’s radial equation. In turn, these polynomials may be useful for (i) better understanding the vector space properties of quasinormal mode solutions (ii) serving as a basis for spectral methods to solve the Teukolsky and confluent Heun equations. Here, we provide an overview of these polynomials’ basic analytic properties: their three-term recurrence relation, ladder operators, and governing differential equation. We demonstrate that the natural polynomials for Schwarzschild and Kerr black holes are Pollaczek-Jacobi polynomials with complex valued parameters. We verify that, despite being constrained to the real line, key results for Pollaczek-Jacobi polynomials hold for black hole polynomials. Along the way, we observe a novel property that is particular to Schwarzschild: the polynomials’ three-term recurrence relation always peaks at the physical overtone index. This work supports the broader application of these polynomials to spectral methods for solving the Teukolsky equation, and other instances of the confluent Heun equation.

We revisit quasinormal modes of Reissner–Nordström–de Sitter black holes, a classical and seemingly well-understood solution of Einstein-Maxwell theory with a positive cosmological constant. While previous studies have focused almost exclusively on the oscillatory photon-sphere branch, we show that two additional branches of non-oscillatory, purely imaginary modes—associated with the de Sitter horizon and with the regime of near-extremal charge (zero damped)—are essential for a complete description of the spectrum. These modes have so far remained largely unexplored for gravitational perturbations despite their relevance for late-time dynamics and stability. In particular, we derive accurate analytic expressions for the purely imaginary quasinormal frequencies in the slow-damping regime, providing a complete description of this sector of the spectrum.

We perform Bayesian model selection to test for the presence of the $(\ell =2,m=0)$ spherical harmonic mode in gravitational wave events that have previously been identified as binary black hole mergers. As our signal model we use the quasicircular, nonprecessing IMRPhenomTHM_20 waveform model, which includes the oscillatory and displacement memory contributions. Including the oscillatory component of the (2, 0) mode increases the signal-to-noise ratio and evidence for this mode, compared to testing only for the presence of gravitational wave memory. Our analysis thus constitutes a natural stepping stone toward detecting gravitational wave memory. We perform our analysis for the binary black hole signals identified in the GWTC-4.0 catalog, and for selected GWTC-5.0 events. In our Bayesian model comparison we find a cumulative ${\log }_{10}\mathcal{B}=1.38\pm 0.79$ in favor of the presence of the (2, 0) mode for the GWTC-4.0 catalog. We also stack the signal-to-noise ratio of the full (2, 0) mode and of its individual contributions, obtaining results consistent with previous studies and reaching ${\mathrm{SNR}}_{\text{memory}}=0.89_{-0.11}^{+0.29}$ after approximately 7.5 months of O4a observations. In addition, we study the precessing candidate GW241127_061008, and find no additional evidence for the (2, 0) mode when precession is included in IMRPhenomTPHM_20. Overall, our results provide an assessment of the observational support for the (2, 0) mode in current gravitational wave data and allow us to discuss prospects for its future detection. We find that decisive statistical evidence will likely require a larger catalog, with an optimistic estimated number of events of $N_{\text{events}}=166_{-55}^{+82}$, based on the specific assumptions adopted in this work. We also expect that decisive evidence will require a more extensive waveform systematics study.

Proca and Maxwell fields in $d$-dimensional Schwarzschild black holes with anti-de Sitter (AdS) asymptotics are investigated through their linear perturbations and associated quasinormal modes (QNMs) with Dirichlet boundary conditions at infinity. We begin by reviewing how the Proca field equations in $d$-dimensional spherically symmetric spacetimes reduce to three radial wavelike equations, one fully decoupled equation and two mutually coupled equations. We also demonstrate explicitly how the Maxwell equations emerge from the zero-mass limit of the Proca system. Several analytical properties of the corresponding QNM spectrum are examined. To compute the QNM frequencies, we employ two complementary numerical methods particularly suited to asymptotically AdS spacetimes. Using these techniques, we determine the QNMs modes of Proca field perturbations in four-, five-, six-, and seven-dimensional Schwarzschild-AdS backgrounds. As a new result, we find numerically that scalar-type Maxwell perturbations in large $d\ge 5$ Schwarzschild-AdS black holes exhibit purely imaginary low-frequency modes, analogous to those found in vector-type gravitational perturbations. The presence of such modes is especially relevant within the AdS/CFT correspondence, as they correspond to the linearized hydrodynamic regime in the dual conformal field theory. We further analyze the influence of the Proca mass on the QNM spectrum, also emphasizing how Maxwell modes are recovered in the massless limit. The dependence of the spectrum on the black hole radius is explored. In addition, analytic expressions for the QNM frequencies of vector-type and monopole Proca perturbations, as well as Maxwell modes, are derived for small $d$-dimensional Schwarzschild-AdS black holes by matching asymptotic expansions using an intermediate region. These analytic results show good agreement with the numerical findings, confirming, in particular, the existence of purely imaginary low-frequency scalar-type Maxwell modes in large $d\ge 5$ Schwarzschild-AdS spacetimes.

The ring wormhole is the zero-mass limit of the Kerr metric. Its geometry is locally flat, but the topology is nontrivial, with a throat connecting two asymptotic regions and a distributional curvature singularity on the ring encircling the throat. We construct stationary generalizations of this static wormhole that are different from Kerr and invariant under reflections across the wormhole throat. The problem reduces to solving the vacuum Ernst equations subject to the corresponding symmetry conditions. The slowly rotating perturbative solutions were constructed previously, while we now present a detailed analysis of nonperturbative solutions obtained within a numerical framework. For slow rotation, they exhibit the nonrelativistic relation $M\sim J^2$ between the mass and angular momentum, which transforms into the Regge relation $J=M^2$ in the fast-rotation regime, when $J\to \infty$ and the ring is stretched without bound by the centrifugal force. However, if the ring size in the static limit is sent to zero at the same time, then $M$ and $J$ remain bounded as the throat linear velocity approaches unity. The wormhole geometry then approaches the extremal Kerr solution, thus “mimicking” it. The wormholes carry a curvature singularity at the ring, but this can be removed by via simple “scalarization” procedure that promotes the vacuum solutions to regular wormholes with a phantom scalar field.

Extracting cosmological information from stage IV weak lensing surveys requires nonlinear modeling of the matter power spectrum that is accurate across a broad range of scales and redshifts and robust to baryonic feedback. We forecast the application of the two-loop effective field theory of large-scale structure (EFTofLSS) to Roman Space Telescope, carefully considering parametrization, scale cuts, and priors. We develop neural network emulators for the two-loop integrals, allowing rapid evaluation of the likelihood. Weak lensing demands a continuous-in-redshift description of the EFT, potentially introducing tens of nuisance parameters. We address this by calibrating the counterterm redshift evolution against the euclid emulator 2 and accounting for the residual freedom in redshift with spline functions. A principal component analysis of the free parameters reduces the dimensionality to a few degrees of freedom that the data can constrain. Next, we calibrate the priors on those degrees of freedom by using a suite of hydrodynamical simulations. We forecast the $S_8$ constraints as a function of scale cuts, showing that the two-loop EFT with Roman cosmic shear provides unbiased $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_{\mathrm{m}}/0.3}$ constraints with relative errors of about 0.9% and 1.4% when allowing for 5% and 1% contamination from ultraviolet modes, respectively. The two-loop EFT improves the scale reach beyond the one-loop EFT and nonlinear dark matter-only models when baryonic effects are included. This framework provides a robust path for extracting small-scale information from future cosmic shear data.

We present a novel framework for improving dark siren cosmology by applying a Gaussian process (GP) to the line-of-sight (LOS) reconstruction of incomplete galaxy catalogs. In the standard galaxy catalog method for inferring the Hubble constant $H_0$ from gravitational-wave (GW) dark sirens, missing galaxies are typically assumed to follow a uniform distribution in comoving volume, an assumption that discards galaxy redshift clustering information crucial for cosmological inference. We propose instead to model the LOS galaxy redshift distribution as a nonparametric function drawn from a GP realization, which is fitted to the observed incomplete catalog via a hierarchical Bayesian likelihood that explicitly accounts for the survey selection function. Applied to mock GW and galaxy catalogs extending up to redshift $z\le 0.4$, our method yields $H_0$ constraints that are on average 23% more precise than the standard homogeneous completion when using a 24%-complete galaxy catalog, and 37% more precise for an 8%-complete catalog. The largest improvement, reaching 66%, is obtained in configurations where the GP most effectively reconstructs the redshift over- and underdensity features that the homogeneous completion fails to capture.

Recent Atacama Cosmology Telescope (ACT) observations, combined with Planck, favor a scalar spectral index in tension with Starobinsky inflation. Two main strategies have been proposed to reconcile Starobinsky inflation with these data: (i) including higher-curvature operators in the gravitational action and (ii) modifying the postinflationary reheating dynamics. We critically reexamine both approaches. When higher-curvature corrections are included, dimensional-analysis arguments allow introducing a second mass scale suppressing higher-dimensional operators, resulting in a one-coupling, two-scale effective theory. We show that fitting the $\mathrm{Planck}+\mathrm{ACT}$ data drives this class of effective theories toward a regime of stronger sensitivity to UV physics, potentially implying fine-tuning of the inflationary observables. We illustrate our general point with two concrete models, namely, no-scale supergravity and metric-affine gravity, showing that they provide different realizations of the same underlying $f(R)$ theory. On the reheating side, requiring the CMB modes to reenter the horizon before recombination leads to stringent constraints on the reheating equation of state, and fitting the $\mathrm{Planck}+\mathrm{ACT}$ data favors an exotic reheating phase with ${\omega }_{\mathrm{reh}}>1/3$, incompatible with inflaton oscillations about the minimum of the standard Starobinsky potential. Finally, we explore the possibility that a phase of cosmological stasis, driven by a tower of decaying massive states, could play the role of the postinflationary epoch. We find that accommodating ACT-preferred $n_s$ in this setup requires a tower of states with negative energy density. Taken together, our results suggest that reconciling Starobinsky inflation with the $\mathrm{Planck}+\mathrm{ACT}$ data demands ingredients that are challenging to motivate from the perspective of UV-complete theories, undermining the minimality of the original Starobinsky model.