Several key observables of the high-precision physics program at future lepton colliders will critically depend on the knowledge of the absolute machine luminosity. The determination of the luminosity relies on the precise knowledge of some reference process, which is, in principle, not affected by unknown physics, so that its cross section can be computed within a well-established theory, like the Standard Model. Quantifying the uncertainties induced by possible new physics effects on such processes is, therefore, crucial. We present an investigation of light and heavy new physics contributions to the small-angle Bhabha process at future $e^{+}{e}^{-}$ colliders, and we discuss possible strategies to remove the contamination due to heavy degrees of freedom by relying on observables that are independent of the absolute luminosity.

Comagnetometers offer unique advantages in measuring exotic spin-dependent interactions by suppressing magnetic noise. Understanding the frequency response to exotic interactions is essential for evaluating and improving the sensitivity of comagnetometers, as the signals often exhibit distinct spectral features. We conduct theoretical and experimental studies on the frequency response of a differential comagnetometer. We derive analytical expressions for the frequency response of the differential comagnetometer to both magnetic field and exotic couplings, along with the conversion relationship between them. Based on this, we revise the method for determining the axion-nucleon coupling strength with comagnetometers. Furthermore, we introduce a light-shift-based calibration protocol to verify the response to exotic interactions. This work helps predict the sensitivity of comagnetometers in detecting exotic fields and advances the exploration of dark matter.

In this work we investigate the spontaneous symmetry breaking (SSB) induced by a classical background spacetime’s curvature, via the two particle irreducible (2PI) nonperturbative effective action formalism. We use the standard Schwinger-DeWitt local expansion of the Feynman propagator, appropriate to probe the effect of spacetime curvature on the local or short scale physics. Recently it was shown using perturbative computations that such SSB is possible with a scalar with a quartic self interaction, positive rest mass squared, and positive nonminimal coupling. Here we confirm in the two loop Hartree approximation that curvature can indeed induce SSB for such a theory. SSB for such a model is not possible in a flat spacetime. The 2PI technique does not only resum the self-energy resulting in mass generation, but also resums, as we have discussed, curvature terms through such mass generation. We have explicitly discussed our results in the context of the de Sitter spacetime, although our calculations are valid for any nonsingular curved spacetime. We show that, in contrast to the perturbative results, SSB is possible with a vanishing nonminimal coupling. These results are further extended to the case of an $O(N)$ symmetric scalar field theory. Restoration of the broken symmetry in the thermal case is also briefly discussed.

We investigate tree-level scattering processes involving quarks ($q$) and gluons ($g$) mediated by graviton exchange in the framework of agravity, a dimensionless and renormalizable theory of quadratic quantum gravity. Focusing on the ultra-Planckian regime, characterized by the Mandelstam variable $s=(p_1+p_2{)}^2$, which corresponds to the total energy squared in the center-of-momentum frame, being much larger than any particle mass scale, we compute the squared amplitudes and analyze the differential cross sections for the processes $gg\to gg$, $gg\to q\overline{q}$, $gq\to gq$, and $qq\to qq$. We demonstrate that all amplitudes scale as $1/s$ at high energies, in agreement with expectations for a UV-complete theory of gravity. In addition, we explore the issue of unitarity in the presence of higher-derivative ghost modes by analyzing the positivity properties of the squared amplitudes. While IR divergences appear in the forward scattering of massless particles, we show that these are regularized by finite quark masses. Our findings support the viability of agravity as a perturbatively unitary and UV-complete extension of general relativity, capable of consistently describing gravitational interactions among elementary matter fields at trans-Planckian energies.

We simulate the formation of fuzzy dark matter (FDM) cores in the presence of a black hole (BH) to explore whether BHs can serve as seeds for FDM core condensation. Our analysis is based on the core-condensation via the kinetic relaxation process for random initial conditions of the FDM. In a generic scenario the BH merges with a precollapsed minicluster formed in a random location, once they share location the core-condensation starts with the FDM density centered at the black hole that during the process acquires a profile consistent with that of the stationary solution of the $\mathrm{FDM}+\mathrm{BH}$ eigenvalue problem. These results indicate that BHs can indeed act as focal points for FDM core condensation. Furthermore, we find that the central density of the resulting FDM core depends on the mass of the BH, which due to its permanent motion relative to the FDM core during the evolution, produces a smaller core density for bigger BH masses; in this way the BH mass is a parameter leading to a new diversity of central FDM core densities. As a collateral result, for our analysis we revised the construction of stationary solutions of $\mathrm{FDM}+\mathrm{BH}$ and found a phenomenological formula for the FDM density that can be used to fit FDM cores around BHs.

The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target. The measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with geant4 and fluka simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE’s cosmic-ray flux measurements.

The Belle II Collaboration reported the first measurement on $\mathrm{Br}(B^{+}\to K^{+}\nu \overline{\nu })$, which lies $2.7\sigma$ away from the Standard Model expectation. This result may be manifestation of new physics beyond the Standard Model. In present work, motivated by the Belle II measurement, we investigate the effect of a dark photon/dark $Z$ on the rare $B$ meson decay $B^{+}\to K^{+}\nu \overline{\nu }$ and show that the $\mathrm{Br}(B^{+}\to K^{+}\nu \overline{\nu })$ excess from Belle II over the Standard Model expectation explained by the appearance of the dark $Z$ especially in resonances. We also derive constraints on various parameters of the two-Higgs-doublet model extended with a dark Abelian gauge group, in light of the measurement of the $\mathrm{Br}(B^{+}\to K^{+}\nu \overline{\nu })$ by the Belle-II Collaboration as well as the upper bound on $\mathrm{Br}(B^0\to K^{*0}\nu \overline{\nu })$ decay, set by the Belle data. Our results indicate that there exists a common region where both experimental results are satisfied for a dark $Z$ mass around 4.5 GeV with suitable values of the other parameters.

We formalize energy-scaling arguments in the standard model effective field theory (SMEFT) to estimate the effects of operators up to dimension ten. Our approach relies on weakly coupled UV completions with no presumed large hierarchies between the Wilson coefficients. We introduce a classification based on the number of external legs and an energy-counting parameter. We establish a dual expansion in $v/\mathrm{\Lambda }$ and $E/\mathrm{\Lambda }$. Extending to four-, five-, and six-particle vertices, our framework highlights energy-enhanced operators that dominate high-energy processes at the High Luminosity-Large Hadron Collider. This organization streamlines experimental analyses to only include operators with energetic impact in their analyses and enhances the discoverability of new physics within the SMEFT framework.

Recent work introduced a new framework for analyzing correlation functions with improved convergence and signal-to-noise properties, as well as rigorous quantification of excited-state effects, based on the Lanczos algorithm and spurious eigenvalue filtering with the Cullum-Willoughby test. Here, we extend this framework to the analysis of correlation-function matrices built from multiple interpolating operators in lattice quantum chromodynamics (QCD) by constructing an oblique generalization of the block Lanczos algorithm, as well as a new physically motivated reformulation of the Cullum-Willoughby test that generalizes to block Lanczos straightforwardly. The resulting block Lanczos method directly extends generalized eigenvalue problem (GEVP) methods, which can be viewed as applying a single iteration of block Lanczos. Block Lanczos provides qualitative and quantitative advantages over GEVP methods analogous to the benefits of Lanczos over the standard effective mass, including faster convergence to ground- and excited-state energies, explicitly computable two-sided error bounds, straightforward extraction of matrix elements of external currents, and asymptotically constant signal-to-noise. No fits or statistical inference are required. Proof-of-principle calculations are performed for noiseless mock-data examples as well as two-by-two proton correlation-function matrices in lattice QCD.

IceCube has observed a diffuse astrophysical neutrino flux over the energy region from a few TeV to a few PeV. At PeV energies, the spectral shape is not yet well measured due to the low statistics of the data. This analysis probes the gap between 1 and 10 PeV by using high-energy downgoing muon neutrinos. To reject the large atmospheric muon background, two complementary techniques are combined. The first technique selects events with high stochasticity to reject atmospheric muon bundles whose stochastic energy losses are smoothed due to high muon multiplicity. The second technique vetoes atmospheric muons with the IceTop surface array. Using 9 yrs of data, we found two neutrino candidate events in the signal region, consistent with expectation from background, each with relatively high signal probabilities. A joint maximum likelihood estimation is performed using this sample and an independent 9.5-yr sample of tracks to measure the neutrino spectrum. A likelihood ratio test is done to compare the single power-law (SPL) vs $\mathrm{SPL}+\mathrm{cutoff}$ hypothesis; the $\mathrm{SPL}+\mathrm{cutoff}$ model is not significantly better than the SPL. High-energy astrophysical objects from four source catalogs are also checked around the direction of the two events. No significant coincidence was found.

A search is presented for hadronic signatures of beyond the Standard Model (BSM) physics, with an emphasis on signatures of a strongly coupled hidden dark sector accessed via resonant production of a $Z^{\prime }$ mediator. The ATLAS experiment dataset collected at the Large Hadron Collider from 2015 to 2018 is used, consisting of proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ and corresponding to an integrated luminosity of $140{\mathrm{fb}}^{-1}$. The $Z^{\prime }$ mediator is considered to decay to two dark quarks, which each hadronize and decay to showers containing both dark and Standard Model particles, producing a topology of interacting and noninteracting particles within a jet known as “semivisible.” Machine learning methods are used to select these dark showers and reject the dominant background of mismeasured multijet events, including an anomaly detection approach to preserve broad sensitivity to a variety of BSM topologies. A resonance search is performed by fitting the transverse mass spectrum based on a functional form background estimation. No significant excess over the expected background is observed. Results are presented as limits on the production cross section of semivisible jet signals, parametrized by the fraction of invisible particles in the decay and the $Z^{\prime }$ mass, and by quantifying the significance of any generic Gaussian-shaped mass peak in the anomaly region.

We present a general formalism for computing the Hodge dual of differential forms in arbitrary dimensions subject to a spherical constraint. This problem arises naturally in Kaluza-Klein compactifications, where sphere reductions demand careful treatment of differential forms constrained to lie on embedded submanifolds. We derive an explicit expression for the Hodge dual of a $p$ form in the presence of such constraints and validate our general Ansatz through illustrative examples in three dimensions, including both flat and diagonal metric backgrounds. The resulting framework offers a systematic and practical tool for handling constrained Hodge duals, with direct applications to consistent truncations in supergravity and string theory compactifications.

We study regular self-gravitating nontopological soliton solutions of the $U(1)$ gauged nonlinear $O(3)$ sigma model with the usual kinetic term and a simple symmetry breaking potential in $3+1$ dimensional asymptotically flat. Both parity-even and parity-odd configurations with an angular node of the scalar field are considered. Localized solutions are endowed with an electric charge; spinning configurations are also coupled to the toroidal flux of magnetic field. We confirm that such solutions do not exist in the flat space limit. Similar to the usual boson stars, a spiral-like frequency dependence of the mass and the Noether charge of the gauged solutions is observed. Depending on the relative strength of gravity and the electromagnetic interaction, the resulting gauged $O(3)$ boson stars at the mass threshold either possess the usual Newtonian limit, or they are linked to a regular strongly gravitating critical configuration. We explore domain of existence of the solutions and investigate some of their physical properties.

We perform an in-depth analysis of rotating scalarized black holes in scalar-Gauss-Bonnet gravity, where scalarization is induced by the spacetime curvature. Our results show that even for very large spins, the scalar charge can reach values comparable to those in the static limit, meaning it is not significantly suppressed. Consequently, curvature-induced scalarization can lead to nongeneral relativity signatures of similar magnitude in both static and rapidly rotating cases. For certain coupling parameters, these scalarized black hole solutions remain within the regime of validity of the effective field theory, where the theory has well-posed formulations.

Einstein equations can be written in the so-called fully constrained formulation (FCF). This formulation has two different sectors: the elliptic sector, formed by the Hamiltonian and momentum constraints together with the equations derived from the gauge choice; and the hyperbolic sector, formed by the evolution of the rest of the spacetime metric variables, which encodes the gravitational radiation. In this work, we present a modification of both sectors that keeps local uniqueness properties of the elliptic system of equations and includes a hierarchical post-Newtonian structure of all the elliptic and hyperbolic equations. This reformulation can have potential applications in cosmology and relativistic astrophysics. Moreover, we show how initial stationary data can be computed numerically using this formulation without assuming a conformally flat spatial metric, with the illustrative example of a rotating neutron star.

In principle, global properties of solution of Einstein equations need to be addressed using the conformal Einstein equations, because this conformal compactification allows a clean definition of the “infinities” (spacelike, timelike, and null infinity) of general relativity. However, in numerical calculations often compactified coordinates in the physical space are used to reach these infinities. In this note, we discuss the conformal Einstein equations in spherical symmetry coupled to a massless scalar field and compare them with corresponding equations using a compactified coordinate in physical spacetime. The derivation of the field equations is based on metrics, in which the radial coordinate is an affine parameter along outgoing null rays. We show that the conformal equations within an affine-null metric formulation can be cast in a natural hierarchical form after the introduction of suitable auxiliary fields. The system of partial differential equations associated with the resulting (unphysical) conformal field equations proves to be identical to a system that employs a compactified coordinate in physical space along with well-constructed regularized fields. The reason for this equivalence is the introduction of new regularized fields in the physical spacetime after coordinate compactification to obtain a regular system of equations on the complete domain of the compactified coordinate. As part of this work, we also present the solution of the conformal field equations in affine-null coordinates near the conformal boundary, where the Bondi mass loss formula for a massless scalar field is recovered. The validity of the balance law of the mass loss at null infinity is demonstrated numerically.

The study investigates orbital motion of test particles near compact objects described by solutions involving massless scalar fields, electromagnetic fields, and nonlinear electrodynamics. Specifically, we analyze orbital dynamics in the Janis-Newman-Winicour, Janis-Newman-Winicour-Maxwell, Schwarzschild-Melvin, and Bonnor-Melvin spacetimes, comparing the results with those obtained for the Schwarzschild and Reissner-Nordström solutions. We examine the stability of circular orbits and the behavior of epicyclic frequencies under varying physical parameters. Our analysis shows that in certain cases the central object transitions into a naked singularity. Deviations from classical Schwarzschild and Reissner-Nordström solutions reveal conditions for the existence of multiple photon orbits or marginally stable orbits. In some instances, the geometry allows the presence of two photon orbits—one stable and one unstable—with an interesting connection to the region of stable orbits. We find that at lower intensities, the effects of the scalar field and electromagnetic fields are comparable and seemingly interchangeable. However, for a sufficiently strong scalar field, its influence becomes dominant, leading to the emergence of a distinct region of stable orbits near the naked singularity. These effects are illustrated within the framework of optical geometry using embedding diagrams.

Next-generation gravitational-wave observatories will reach farther into the Universe than currently possible, revealing black-hole mergers from early stellar binary systems such as Population III stars, whose properties are currently poorly constrained. We develop a method to infer the properties of their progenitor populations from gravitational-wave catalogs. Using Bayesian deep learning, we train an emulator for population-synthesis predictions of black-hole merger properties across redshift as a function of the initial stellar mass function, crucially accounting for systematic uncertainty due to the finite number of training simulations. Combined with a nonparametric model for star formation history, we analyze catalogs containing both Population I/II and III sources simulated with full Bayesian parameter estimation for a detector network of Cosmic Explorer and Einstein Telescope with one year of observing time. We demonstrate our ability to separate these two populations at high redshifts where both make comparable contributions to the black-hole merger rate, excluding a Population III merger rate of zero at nearly 100% credibility. Moreover, we can place meaningful constraints on the Population III progenitor distributions; in particular, we constrain the spectral index of the initial mass function to within roughly $\pm 0.5$ of the true value and the log of the star formation rate density to within $\sim 25\%$ over redshifts 10 to 20. By leveraging astrophysics-informed and astrophysics-agnostic models, we demonstrate the discriminative power of our combined inference approach and highlight the potential of next-generation gravitational-wave observatories to uncover the details of high-redshift stellar populations.

Extrasolar planetary systems commonly exhibit planets on eccentric orbits, with many systems located near or within mean-motion resonances, showcasing a wide diversity of orbital architectures. Such complex systems challenge traditional secular theories, which are limited to first-order approximations in planetary masses or rely on expansions in orbital elements—eccentricities, inclinations, and semimajor axis ratios—that are subject to convergence issues, especially in highly eccentric, inclined, or tightly packed systems. To overcome these limitations, we develop a numerical approach to second-order perturbation theory based on the Lie transform formalism. Our method avoids the need for expansions in orbital elements, ensuring broader applicability and more robust convergence. We first outline the Hamiltonian framework for the 3-body planetary problem and apply a canonical transformation to eliminate fast angle dependencies, deriving the secular Hamiltonian up to second order in the mass ratio. We then use the fast Fourier transform algorithm to numerically simulate, in an accurate way, the long-term evolution of planetary systems near or away from mean-motion resonances. Finally, we validate our methods against well-known planetary configurations, such as the Sun-Jupiter-Saturn system, as well as to exoplanetary systems like WASP-148, TIC 279401253, and GJ 876, demonstrating the applicability of our models across a wide range of planetary configurations.

We discuss a novel mechanism for the proto-neutron star acceleration assisted by the chiral separation effect, which induces an axial vector current in a dense medium. We consider the process of neutrinos scattering off the background axial vector current of electrons. We show that anisotropy of either magnetic field or density in momentum space is essential for nonzero recoil, and we call this mechanism the chiral anisotropy conversion. Assuming a strong magnetic field $B\simeq {10}^{12}\mathrm{T}$ and anisotropy by $\sim 10\%$, we find that the chiral anisotropy conversion can yield the velocity of order of typical pulsar kicks, i.e., $v_{\mathrm{kick}}\gtrsim 1000\mathrm{km}/\mathrm{s}$.