We consider a braneworld scenario in which a flat 4D brane, embedded in $M^{3,1}\times S^1$, is moving on or spiraling around the $S^1$. Although the induced metric on the brane is 4D Minkowski, the would-be Lorentz symmetry of the brane is broken globally by the compactification. As recently pointed out, this means causal bulk signals can propagate superluminally and even backwards in time according to brane observers. Here we consider the effective action on the brane induced by loops of bulk fields. We consider a variety of self-energy and vertex corrections due to bulk scalars and gravitons and show that bulk loops with nonzero winding generate UV-finite Lorentz-violating terms in the 4D effective action. The results can be accommodated by the Standard Model extension, a general framework for Lorentz-violating effective field theory.

We show via both analytical calculation and numerical simulation that the optimal cross-correlation statistic (OS) for stochastic gravitational-wave-background (GWB) searches using data from pulsar timing arrays follows a generalized chi-squared (GX2) distribution—i.e., a linear combination of chi-squared distributions with coefficients given by the eigenvalues of the quadratic form defining the statistic. This observation is particularly important for calculating the frequentist statistical significance of a possible GWB detection, which depends on the exact form of the distribution of the OS signal-to-noise ratio $\widehat{\rho }\equiv {\widehat{A}}_{\mathrm{gw}}^2/{\sigma }_0$ in the absence of GW-induced cross correlations (i.e., the null distribution). Previous discussions of the OS have incorrectly assumed that the analytic null distribution of $\widehat{\rho }$ is well approximated by a zero-mean unit-variance Gaussian distribution. Empirical calculations show that the null distribution of $\widehat{\rho }$ has “tails” which differ significantly from those for a Gaussian distribution but which follow (exactly) a GX2 distribution. Thus, a correct analytical assessment of the statistical significance of a potential detection requires the use of a GX2 distribution.

We study the linear polarization from the accretion disk around weakly and strongly naked Janis-Newman-Winicour singularities. We consider an analytical toy model of a thin magnetized fluid ring orbiting in the equatorial plane and emitting synchrotron radiation. The observable polarized images are calculated and compared to the Schwarzschild black hole for physical parameters compatible with the radio source M87. For small inclination angles the direct images of the weakly naked singularities closely mimic the Schwarzschild black hole. The deviation in the polarization properties increases if we consider larger inclination angles or higher order images as for indirect images the polarization intensity grows several times in magnitude compared to black holes. Strongly naked singularities produce significant observational signatures already in the direct images. They create a second image of the fluid ring with more than three times larger polarization intensity and characteristic twist of the polarization direction. Due to this additional structure they can be distinguished in polarimetric experiments.

All the magnetically charged ultrastatic and spherically symmetric spacetime solutions in the framework of linear/nonlinear electrodynamics, with an arbitrary electromagnetic Lagrangian density $\mathcal{L}(\mathcal{F})$ depending only of the electromagnetic invariant $\mathcal{F}=F_{\alpha \beta }{F}^{\alpha \beta }/4$, minimally coupled to Einstein-scalar-Gauss-Bonnet gravity [EsGB-$\mathcal{L}(\mathcal{F})$], are found. We also show that a magnetically charged ultrastatic and spherically symmetric EsGB-$\mathcal{L}(\mathcal{F})$ solution with invariant $\mathcal{F}$ having a strict global maximum value ${\mathcal{F}}_0$ in the entire domain of the solution, and such that ${\mathcal{L}}_0=\mathcal{L}({\mathcal{F}}_0)>0$, can be interpreted as an ultrastatic wormhole spacetime geometry with throat radius determined by the scalar charge and the quantity ${\mathcal{L}}_0$. We provide some examples, including Maxwell’s theory of electrodynamics (linear electrodynamics) ${\mathcal{L}}_{\mathrm{LED}}=\mathcal{F}$, producing the magnetic dual of the purely electric Ellis-Bronnikov EsGB Maxwell wormhole derived in [P. Cañate, J. Sultana, D. Kazanas, Phys. Rev. D 100, 064007 (2019)]; and the nonlinear electrodynamics (NLED) models given by Born-Infeld ${\mathcal{L}}_{\mathrm{BI}}=-4{\beta }^2+4{\beta }^2\sqrt{1+\mathcal{F}/(2{\beta }^2)}$, and Euler-Heisenberg in the approximation of the weak-field limit ${\mathcal{L}}_{\mathrm{EH}}={\mathcal{L}}_{\mathrm{LED}}+\gamma {\mathcal{F}}^2/2$. With those NLED models, two novel magnetically charged ultrastatic traversable wormholes (EsGB Born-Infeld and EsGB Euler-Heisenberg wormholes) are presented as exact solutions without exotic matter in EsGB-$\mathcal{L}(\mathcal{F})$ gravity, and we show that these solutions have in common the property that in the weak electromagnetic field region the magnetically charged Ellis-Bronnikov EsGB Maxwell wormhole is recuperated.

Dynamical Chern-Simons (dCS) gravity is a four-dimensional parity-violating extension of general relativity. The standard mechanism to obtain this extension predicts negligible observational effects due to a large decay constant $f$ close to the scale of grand unified theories. Here, we present two constructions of dCS that permit much smaller decay constants, ranging from sub-eV to Planck scales. That is, we show that, in the same manner as axions, dCS gravity can arise from both spontaneous and dynamical symmetry breaking. In either case, the angular part of a complex scalar field develops a pseudoscalar Yukawa interaction with a set of fermions. In the former case, the complex scalar field is a fundamental particle, and in the latter case, it is a bound state of short-wavelength fermion modes arising from strong four-Fermi self-interactions. Due to the Yukawa interaction, loop corrections with gravitons then realize a linear coupling between the angular pseudoscalar and the gravitational Chern-Simons term. The strength of this coupling is set by the Yukawa coupling constant divided by the fermion mass. Therefore, since fermions with small masses are ideal, we identify neutrinos as promising candidates. For example, if a neutrino has a mass $m_{\nu }\lesssim \mathrm{meV}$ and the Yukawa coupling is order unity, the dCS decay constant can be smaller than $f\sim {10}^3{m}_{\nu }\lesssim \mathrm{eV}$. We discuss other potential choices for fermions and give two examples of four-Fermi UV completions.

Every signal propagating through the Universe is at least weakly lensed by the intervening gravitational field. In some situations, wave-optics phenomena (diffraction, interference) can be observed as frequency-dependent modulations of the waveform of gravitational waves (GWs). We will denote these signatures as wave-optics features (WOFs) and analyze them in detail. Our framework can efficiently and accurately compute WOF in the single-image regime, of which weak lensing is a limit. The phenomenology of WOF is rich and offers valuable information; the dense cusps of individual halos appear as peaks in Green’s function for lensing. If resolved, these features probe the number, effective masses, spatial distribution and inner profiles of substructures. High signal-to-noise GW signals reveal WOFs well beyond the Einstein radius, leading to a fair probability of observation by upcoming detectors such as LISA. Potential applications of WOF include reconstruction of the lens’ projected density, delensing standard sirens and inferring large-scale structure morphology and the halo mass function. Because WOF are sourced by light halos with negligible baryonic content, their detection (or lack thereof) holds promise to test dark matter scenarios.

Primordial black hole (PBH) formation from first-order phase transitions (FOPTs) combines two prevalent elements of beyond the Standard Model physics with wide-ranging consequences. We elaborate on a recently proposed scenario in which inhomogeneities in vacuum energy decay seed the overdensities that collapse to PBHs. In this scenario, the PBH mass is determined by the Hubble mass as in conventional formation scenarios, while its number density is determined by the nucleation dynamics of the FOPT. We present a detailed study of the formation probability including parameter dependencies. In addition, we generate populations in the open mass window as well as for the HSC and OGLE candidate microlensing events. This mechanism inevitably creates PBHs in generic FOPTs, with significant populations produced in slow and moderately strong phase transitions.

Bulk flow velocities are typically estimated in the idealized picture where observers are moving within a perfectly homogeneous and isotropic spacetime. This picture is consistent within standard perturbation theory up to relativistic effects that lead to correction terms of order $vz$, where $z$ is the redshift of observation and $v$ is the amplitude of the bulk flow. The dominant relativistic contributions at scales $z\lesssim 1$ are caused by gravitational redshift and time evolution of the velocity field. We include these effects within a broadly applicable weak-field approximation and provide a cosmographic formula for estimating bulk flows at a high precision. Based on this formula, we judge that recent bulk flow estimates are biased toward larger values by $\sim 10\%$. This theoretical bias surpasses the measurement biases of the same estimates, and it will become still more important to account for the relativistic effects as the scales at which bulk flows are estimated to increase.

We study the impact of out-of-equilibrium, dissipative effects on the dynamics of inspiraling neutron stars. We find that modeling dissipative processes (such as those from the stars internal effective fluid viscosity) requires that one introduce a new tidal deformability parameter—the dissipative tidal deformability—which modifies the phase of gravitational waves emitted during the inspiral phase of a neutron star binary. We show that the dissipative tidal deformability corrects the gravitational-wave phase at 4 post-Newtonian order for quasicircular binaries. This correction receives a large finite-size enhancement by the stellar compactness, analogous to the case of the tidal deformability. Moreover, the correction is not degenerate with the time of coalescence, which also enters at 4 post-Newtonian order, because it contains a logarithmic frequency-dependent contribution. Using a simple Fisher analysis, we show that physically allowed values for the dissipative tidal deformability may be constrained by measurements of the phase of emitted gravitational waves to roughly the same extent as the (electric-type, quadrupolar) tidal deformability. Finally, we show that there are no out-of-equilibrium, dissipative corrections to the tidal deformability itself. We conclude that there are at least two relevant tidal deformability parameters that can be constrained with gravitational-wave phase measurements during the late inspiral of a neutron star binary: one which characterizes the adiabatic tidal response of the star, and another which characterizes the leading-order out-of-equilibrium, dissipative tidal response. These findings open a window to probe dissipative processes in the interior of neutron stars with gravitational waves.

The gravitational wave (GW) and neutrino signals from core-collapse supernovae (CCSNe) are expected to carry pronounced imprints of the standing accretion shock instability (SASI). We investigate whether the correlation between the SASI signatures in the GW and neutrino signals could be exploited to enhance the detection efficiency of GWs. We rely on a benchmark full-scale three-dimensional CCSN simulation with zero-age main sequence mass of $27M_{\odot }$. Two search strategies are explored: 1. the inference of the SASI frequency range and/or time window from the neutrino event rate detectable at the IceCube Neutrino Observatory; 2. the use of the neutrino event rate to build a matched filter template. We find that incorporating information from the SASI modulations of the IceCube neutrino event rate can increase the detection efficiency compared to standard GW excess energy searches up to 30% for nearby CCSNe. However, we do not find significant improvements in the overall GW detection efficiency for CCSNe more distant than 1.5 kpc. We demonstrate that the matched filter approach performs better than the unmodeled search method, which relies on a frequency bandpass inferred from the neutrino signal. The improved detection efficiency provided by our matched filter method calls for additional work to outline the best strategy for the first GW detection from CCSNe.

Production of electron-positron pairs by a high-energy $\gamma$ photon and a bichromatic laser wave is considered where the latter is composed of a strong low-frequency and a weak high-frequency component, both with circular polarization. An integral expression for the production rate is derived that accounts for the strong laser mode to all orders and for the weak laser mode to first order. The structure of this formula resembles the well-known expression for the nonlinear Breit-Wheeler process in a strong laser field, but includes the dynamical assistance from the weak laser mode. We analyze the dependence of the dynamical rate enhancement on the applied field parameters and show, in particular, that it is substantially higher when the two laser modes have opposite helicity.

The production and subsequent rescattering of secondary pions produced in proton beam dumps provide additional opportunities for the production of light new particles such as dark photons. This new mechanism has been overlooked in the past but can extend the mass reach of the SpinQuest experiment and its proposed DarkQuest upgrade. We use chiral perturbation theory to calculate the production of kinetically mixed dark photons through bremsstrahlung off secondary charged pions. We find that the reach of SpinQuest/DarkQuest can be pushed further into the multi-GeV mass range compared to estimates based only on primary dark photon production through meson decay or proton bremsstrahlung. Our analysis can be regarded as the first of several steps to include secondary pion contributions. In an upcoming analysis we will extend our calculation into the high-momentum-transfer regime through the use of pion parton distribution functions and including hadronic resonances, which will further increase the estimated mass reach.

The measurement of lepton universality parameters $R_{K^{(*)}}$ was updated by LHCb in December 2022, which indicated that the well-known anomalies in flavor-changing neutral current (FCNC) processes of $B$ meson decays have faded away. However, does this mean that all new physics possibilities related to $b\to s{\ell }^{+}{\ell }^{-}$ have been excluded? We aim to answer this question in this work. The state-of-the-art effective Hamiltonian is adopted to describe $b\to s$ transition, while BSM (beyond the Standard Model) new physics effects are encoded in Wilson coefficients (WCs). Using around 200 observables in leptonic and semileptonic decays of $B$ mesons and bottom baryons, measured by LHCb, CMS, ATLAS, Belle, and BABAR, we perform global fits of these Wilson coefficients in four different scenarios. In particular, lepton flavors in WCs are specified in some of the working scenarios. To see the change of new physics parameters, we use both the data before and after the 2022 release of $R_{K^{(*)}}$ in two separate sets of fits. We find that in three of the four scenarios, $\mathrm{\Delta }{C}_9^{\mu }$ still has a deviation around or more than $4\sigma$ from the Standard Model. The lepton flavor in WCs is distinguishable for $\mathrm{\Delta }{C}_9$ at the $1\sigma$ level, but at the $2\sigma$ level all the operators are flavor identical. We demonstrate numerically that there is no chirality for muon type of scalar operator and it is kept at the $1\sigma$ level for their electron type dual ones, while chiral difference exists for ${\mathcal{O}}_9^{\mu }$ at least at the $2\sigma$ level. Moreover, it can be deduced that the scalar operators ${\mathcal{O}}_{S,P}^{{(}^{\prime })\mu }$ become null if new physics emerges in terms of Standard Model effective field theory (SMEFT) up to dimension-6.

We investigate the low-lying baryon spectrum using three $N_f=2+1+1$ ensembles simulated with physical values of the quark masses and lattice spacings of 0.080, 0.069 and 0.057 fm. The ensembles are generated using twisted mass clover-improved fermions and the Iwasaki gauge action. The spatial length is kept approximately the same at about 5.1 fm to 5.5 fm fulfilling the condition $m_{\pi }L>3.6$. We investigate isospin splitting within isospin multiples and verify that for most cases the isospin splitting for these lattice spacing is consistent with zero. In the couple of cases, for which there is a nonzero value, in the continuum limit, the mass splitting goes to zero. The baryon masses are extrapolated to the continuum limit using the three $N_f=2+1+1$ ensembles and are compared to other recent lattice QCD results. For the strange and charm quark masses we find, respectively, $m_s(2\mathrm{GeV})=99.2(2.7)\mathrm{MeV}$ and $m_c(3\mathrm{GeV})=1.015(39)\mathrm{GeV}$. The values predicted for the masses of the doubly charmed ${\mathrm{\Xi }}_{cc}^{\star }$, ${\mathrm{\Omega }}_{cc}$ and ${\mathrm{\Omega }}_{cc}^{\star }$ baryons are 3.676(55) GeV, 3.703(51) GeV and 3.803(50) GeV, respectively, and for the triply charmed ${\mathrm{\Omega }}_{ccc}$ baryon is 4.785(71) GeV.

This paper, which is part of a series, is devoted to several technical issues. In the first part of the paper, we discuss the usual wave functions in the center of mass frame for baryons, by clarifying the representations of the three-quark permutation group $S_3$. We extend the analysis for up to five “spinors” with $\rho$, $\lambda$-symmetry, and derive explicitly the totally symmetric wave functions modulo color. They are explicitly used to describe the excited nucleons $N^{*}$ states, in the P- and D-shell. We also show how to use symbolic operations in Mathematica, in spin-tensor notations to make explicit these states. For the S- and P-shells, the totally antisymmetric wave functions are given, and the pertinent matrix elements for the spin-dependent operators calculated, including the mixing between states with different total spin $S$. In the second part of the paper we turn to the light front wave functions, with an emphasis on the longitudinal wave functions, with a novel basis set. We also discuss their symmetries under permutations, and select the proper combinations for the transverse and longitudinal excitations for $N^{*}$ on the light front.

We present a strategy to obtain equations of general relativity for an irrotational dust continuum within a flow-orthogonal foliation of spacetime from the equations of Newtonian gravitation, and vice versa, without employing a weak field expansion or a limiting process on the speed of light. We argue that writing Newton’s equations in a Lagrangian frame and relaxing integrability of vector gradients is sufficient to obtain equations that are identical to Einstein’s equations in ($3+1$)-form when respecting the Lorentzian signature of the time parametrization. We discuss implications and provide an outlook on how to extend the obtained correspondence to more general spacetimes.

The QCD axion offers a natural resolution to the strong-$CP$ problem and provides a compelling dark matter candidate. If the QCD axion constitutes all the dark matter, the simplest models pick out a narrow range of masses around $100\mathrm{\mu }\mathrm{eV}$. We point out a natural production mechanism for QCD axion dark matter at masses up to existing astrophysical bounds [$\mathcal{O}(20\mathrm{meV})$ for the most minimal models and $\mathcal{O}(1\mathrm{eV})$ for nucleophobic models]. If the QCD axion mixes with a sterile axion, the relative temperature dependence of their potentials can lead to an avoided level crossing of their mass eigenstates. This leads to a near-total transfer of energy density from the sterile axion to the QCD axion, resulting in a late-time QCD axion abundance sufficient to make up all of present-day dark matter. Our result provides additional theoretical motivation for several direct detection experiments that will probe this part of parameter space in the near future.

We calculate the Debye screening mass in thermal, dense, and magnetized QCD matter in the frame of resummed perturbation theory. In the limit of zero temperature, when the Landau energy level and Fermi surface of quarks match each other ${\mu }_q^2=2n|qB|$, where $q$, ${\mu }_q$, and $B$ are respectively the quark electric charge, baryon chemical potential, and external magnetic field, the screening mass diverges and the system is in the state of weakly interacting parton gas, which is very different from the known result of strongly interacting quark-gluon plasma at high temperature. The divergence disappears in the thermal medium, but the screening mass oscillates with clear peaks at the matched magnetic field.