We construct the exact lens equation proposed by Frittelli et al. for the electrically charged static black hole spacetime of the Einstein-Euler-Heisenberg (EEH) theory, which is a nonlinear electromagnetic generalization of the Reissner-Nordström (RN) solution. We study the trajectories of light by means of the effective Plebański pseudometric. We compare the EEH exact lens equation with the thin-lens equations, as well as with the corresponding equations for the RN solution. The shadow of the black hole, the angular-diameter distance to the sources, and the time delay of arrival of the images are also calculated and discussed.

Spin precession in compact binaries is intricately tuned to the multipole structure of the underlying bodies. For black holes, violations of the no-hair theorems induced by modifications to general relativity correct the precession dynamics, which in turn imprints onto the amplitude and phase modulations of the gravitational waves emitted by the binary. Recently, the spin precession equations were derived up to second order in spin for dynamical Chern-Simons (dCS) gravity, a parity-violating modified theory of gravity. We here solve these equations and construct, for the first time, analytic expressions for the time- and frequency-domain gravitational waves emitted in the quasicircular inspiral of spin-precessing black hole binaries in a modified theory of gravity using the post-Newtonian approximation. Working within the small coupling approximation and using multiple scale analysis, we show that the corrections to the nutation phase enter at relative first post-Newtonian (1PN) order, and the corrections to the precession angle and Thomas phase enter at relative 0PN order. Making use of the stationary phase approximation and shifted uniform asymptotics, we find that the Fourier phase of the waveform is characterized by three modifications: two due to the backreaction of the precession dynamics onto the spin-orbit and spin-spin couplings that enter at 1.5PN and 2PN orders, and a 2PN modification due to the emission of dipole radiation. We also find that backreaction of the precession dynamics forces the dCS corrections to the Fourier amplitude to enter at 0PN order, as opposed to 2PN order, as expected for spin-aligned binaries. Our work lays the first foundational stones to build an inspiral-merger-ringdown phenomenological model for spin-precessing binaries in a modified theory of gravity.

In Horndeski theories containing a scalar coupling with the Gauss-Bonnet (GB) curvature invariant $R_{\mathrm{GB}}^2$, we study the existence and linear stability of neutron star (NS) solutions on a static and spherically symmetric background. For a scalar-GB coupling of the form $\alpha \xi (\varphi )R_{\mathrm{GB}}^2$, where $\xi$ is a function of the scalar field $\varphi$, the existence of linearly stable stars with a nontrivial scalar profile without instabilities puts an upper bound on the strength of the dimensionless coupling constant $|\alpha |$. To realize maximum masses of NSs for a linear (or dilatonic) GB coupling ${\alpha }_{\mathrm{GB}}\varphi R_{\mathrm{GB}}^2$ with typical nuclear equations of state, we obtain the theoretical upper limit $\sqrt{|{\alpha }_{\mathrm{GB}}|}<0.7\mathrm{km}$. This is tighter than those obtained by the observations of gravitational waves emitted from binaries containing NSs. We also incorporate cubic-order scalar derivative interactions, quartic derivative couplings with nonminimal couplings to a Ricci scalar besides the scalar-GB coupling, and show that NS solutions with a nontrivial scalar profile satisfying all the linear stability conditions are present for certain ranges of the coupling constants. In regularized four-dimensional Einstein-GB gravity obtained from a Kaluza-Klein reduction with an appropriate rescaling of the GB coupling constant, we find that NSs in this theory suffer from a strong coupling problem as well as Laplacian instability of even-parity perturbations. We also study NS solutions with a nontrivial scalar profile in power-law $F(R_{\mathrm{GB}}^2)$ models, and show that they are pathological in the interior of stars and plagued by ghost instability together with the asymptotic strong coupling problem in the exterior of stars.

We work out the junction conditions for the Palatini $f(\mathcal{R},T)$ extension of general relativity, where $f$ is an arbitrary function of the curvature scalar $\mathcal{R}$ of an independent connection, and of the trace $T$ of the stress-energy tensor of the matter fields. We find such conditions on the allowed discontinuities of several geometrical and matter quantities, some of which depart from their metric counterparts, and in turn extend their Palatini $f(\mathcal{R})$ versions via some new $T$-dependent terms. Moreover, we also identify some “exceptional cases” of $f(\mathcal{R},T)$ Lagrangians such that some of these conditions can be discarded, thus allowing for further discontinuities in $\mathcal{R}$ and $T$ and, in contrast with other theories of gravity, they are shown to not give rise to extra components in the matter sector, e.g., momentum fluxes and double gravitational layers. We discuss how these junction conditions, together with the nonconservation of the stress-energy tensor ascribed to these theories, may induce nontrivial changes in the shape of specific applications such as traversable thin-shell wormholes.

Fuzzy dark matter (FDM) is a well-motivated candidate for dark matter (DM) as its tiny mass and large de-Broglie wavelength suppress small-scale matter fluctuations, thereby solving some of the small-scale discrepancies in $\mathrm{\Lambda }\mathrm{CDM}$. Although it has been ruled out as the single component of DM by several observables, there is still a region in the FDM parameter space (the “FDM window,” ${10}^{-25}\mathrm{eV}\lesssim m_{\mathrm{FDM}}\lesssim {10}^{-23}\mathrm{eV}$) where FDM is allowed to comprise a large portion of the total DM. In this work, for the first time, we study the signature of FDM (comprised of ultralight axions) in fractions less than unity on the 21-cm signal and its detectability by 21-cm interferometers such as HERA, taking into account the degeneracy with both astrophysical and cosmological parameters, using a new pipeline that combines modified versions of the camb and 21-cmfast codes. Our forecasts imply that HERA in its design performance will be sensitive to FDM fractions as small as 1% in the FDM window, and improve over existing bounds for other masses by up to an order of magnitude.

The Rayleigh scattering of cosmic microwave background (CMB) photons off the neutral hydrogen produced during recombination effectively creates an additional scattering surface after recombination that encodes new cosmological information, including the expansion and ionization history of the universe. A first detection of Rayleigh scattering is a tantalizing target for next-generation CMB experiments. We have developed a Rayleigh scattering forecasting pipeline that includes instrumental effects, atmospheric noise, and astrophysical foregrounds (e.g., Galactic dust, cosmic infrared background, or CIB, and the thermal Sunyaev-Zel’dovich effect). We forecast the Rayleigh scattering detection significance for several upcoming ground-based experiments, including $\mathrm{SPT}\text{−}3\mathrm{G}+$, Simons Observatory, CCAT-prime, and CMB-S4, and examine the limitations from atmospheric and astrophysical foregrounds as well as potential mitigation strategies. When combined with Planck data, we estimate that the ground-based experiments will detect Rayleigh scattering with a significance between 1.6 and 3.7, primarily limited by atmospheric noise and the CIB.

Parity-violating physics in the early universe can leave detectable traces in late-time observables. While vector- and tensor-type parity violation can be observed in the $B$-modes of the cosmic microwave background, scalar-type signatures are visible only in the four-point correlation function (4PCF) and beyond. This work presents a blind test for parity violation in the 4PCF of the baryon oscillation spectroscopic survey (BOSS) CMASS sample, considering galaxy separations in the range $[20,160]h^{-1}\mathrm{Mpc}$. The parity-odd 4PCF contains no contributions from standard $\mathrm{\Lambda }\mathrm{CDM}$ physics and can be efficiently measured using recently developed estimators. Data are analyzed using both a nonparametric rank test (comparing the BOSS 4PCFs to those of realistic simulations) and a compressed ${\chi }^2$ analysis, with the former avoiding the assumption of a Gaussian likelihood. These find similar results, with the rank test giving a detection probability of 99.6% ($2.9\sigma$). This provides significant evidence for parity violation, from either cosmological sources or systematics. We perform a number of systematic tests: although these do not reveal any observational artifacts, we cannot exclude the possibility that our detection is caused by the simulations not faithfully representing the statistical properties of the BOSS data. Our measurements can be used to constrain physical models of parity violation. As an example, we consider a coupling between the inflaton and a $U(1)$ gauge field and place bounds on the latter’s energy density, which are several orders of magnitude stronger than those previously reported. Upcoming probes such as DESI and Euclid will reveal whether our detection of parity violation is due to new physics, and strengthen the bounds on a variety of models.

The purely gravitational evidence supporting the need for dark matter (DM) particles is compelling and based on Galactic to cosmological scale observations. Thus far, the promising weakly interacting massive particles scenarios have eluded detection, motivating alternative models for DM. We consider the scenarios involving the superheavy dark matter (SHDM) that potentially can be emitted by primordial black holes (PBHs) and can decay or annihilate into ultrahigh-energy (UHE) neutrinos and photons. The observation of a population of photons with energies $E\ge 10^{11}\mathrm{G}\mathrm{e}\mathrm{V}$ would imply the existence of completely new physical phenomena, or shed some light on DM models. Only the ultrahigh-energy cosmic-ray observatories have the capabilities to detect such UHE decay products via the measurements of UHE photon-induced extensive air showers. Using the upper bound on the flux of UHE cosmic rays beyond ${10}^{11.3}\mathrm{GeV}$ implying $J(>{10}^{11.3}\mathrm{GeV})<3.6\times {10}^{-5}{\mathrm{km}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{yr}}^{-1}$, at the 90% C.L. reported by the Pierre Auger Observatory, we obtain global limits on the lifetime of the DM particles with masses ${10}^{15}\le M_X\le {10}^{17}\mathrm{GeV}$. The constraints derived here are new and cover a region of the parameter space not yet explored. We compare our results with the projected constraints from future POEMMA and JEM-EUSO experiments, in order to quantify the improvement that will be obtained by these missions. Moreover, assuming that an epoch of early PBHs domination introduces a unique spectral break, $f_{*}$, in the gravitational wave spectrum, the frequency of which is related to the SHDM mass, we map potential probes and limits of the DM particles masses on the $f_{*}-M_X$ parameter space.

We present the results of studying the accretion disk vs jet power for a large fraction of all the blazars detected by the Fermi Gamma-Ray Space Telescope. The disk power is inferred from the emission line luminosities obtained from published results. As indicators of jet power, we use low frequency radio luminosity from the extended jet, maximum speed of radio knots observed in the VLBA monitoring of the pc-scale jets, kinetic energy of electrons in the jet deduced from the best-fit theoretical models of their spectral energy distribution, and $\gamma$-ray luminosity with and without beaming correction. We obtain a significant correlation in most of those cases. However, we find that the correlations are often driven by the common redshift dependence of the compared quantities. In order to remove the redshift bias and probe the intrinsic correlation between the disk and jet power, we compute the partial correlation coefficient as well as the correlation in small redshift bins and find that the intrinsic disk-jet correlation is still present but weaker. In the cases, in which the common redshift dependence does not affect the result, we find that blazars do not exhibit high jet power for low disk luminosities while there are both high and low jet power for high disk luminosities. This result indicates that a powerful disk is a necessary but not sufficient condition to produce a powerful jet.

We investigate the optimization of the photon polarization to increase the yield of the Breit-Wheeler pair production in arbitrarily polarized plane wave backgrounds. We show that the optimized photon polarization can improve the positron yield by more than 20% compared to the unpolarized case, in the intensity regime of current laser-particle experiments. The seed photon’s optimal polarization is the result of the polarization coupling with the polarization of the laser pulse. The compact expressions of the coupling coefficients in both the perturbative and nonperturbative regimes are given. Because of the evident difference in the coupling coefficients for the linear- and circular-polarization components, the seed photon’s optimal polarization state in an elliptically polarized laser background deviates considerably from the orthogonal state of the laser polarization.

Inspired by the recent determination of the $W$-boson mass by the CDF collaboration, we revisit an $SO(10)$ axion model in which a scalar $SU(2{)}_L$ triplet field with zero hypercharge is known to acquire a nonzero vacuum expectation value (VEV) through its mixing with the Standard Model Higgs doublet. The triplet VEV provides a sizable contribution to the $W$ mass, which helps in significantly lowering the $7\sigma$ discrepancy between the Standard Model prediction and the higher CDF value for $m_W$. We show that the relatively light triplet mass ($\sim (1–50)\mathrm{TeV}$) is compatible with gauge coupling unification and observable proton decay. An unbroken $Z_2$ gauge symmetry, coupled with the presence of two fermionic 10-plets required to resolve the axion domain wall problem means that both axions and a stable intermediate mass ($\sim {10}^9–{10}^{10}\mathrm{GeV}$) fermion are plausible dark matter candidates. We also display the gravitational wave spectrum from the intermediate scale topologically stable cosmic strings predicted by the model.

A Higgsino in supersymmetric standard models can play the role of a dark matter particle. In conjunction with the naturalness criterion, the Higgsino mass parameter is expected to be around the electroweak scale. In this work, we explore the potential of probing the nearly degenerate light Higgsinos with machine learning at the LHC. By analyzing jet images and other jet substructure information, we use the convolutional neural network to enhance the signal significance. We find that our deep learning jet image method can improve the previous result based on the conventional cut flow by about a factor of 2 at the High-Luminosity LHC.

Quantum information observables, such as entanglement measures, provide a powerful way to characterize the properties of quantum states. We propose to use them to probe the structure of fundamental interactions and to search for new physics at high energy. Inspired by recent proposals to measure entanglement of top quark pairs produced at the LHC, we examine how higher-dimensional operators in the framework of the Standard Model effective field theory modify the Standard Model expectations. We explore two regions of interest in the phase space where the Standard Model produces maximally entangled states: at threshold and in the high-energy limit. We unveil a nontrivial pattern of effects, which depend on the initial state partons, $q\overline{q}$ or $gg$, on whether only linear or up to quadratic Standard Model effective field theory contributions are included, and on the phase space region. In general, we find that higher-dimensional effects lower the entanglement predicted in the Standard Model.

We propose a new model-agnostic search strategy for physics beyond the standard model (BSM) at the LHC, based on a novel application of neural density estimation to anomaly detection. Our approach, which we call classifying anomalies through outer density estimation (cathode), assumes the BSM signal is localized in a signal region (defined e.g., using invariant mass). By training a conditional density estimator on a collection of additional features outside the signal region, interpolating it into the signal region, and sampling from it, we produce a collection of events that follow the background model. We can then train a classifier to distinguish the data from the events sampled from the background model, thereby approaching the optimal anomaly detector. Using the LHC Olympics R&D dataset, we demonstrate that cathode nearly saturates the best possible performance, and significantly outperforms other approaches that aim to enhance the bump hunt (cwola hunting and anode). Finally, we demonstrate that cathode is very robust against correlations between the features and maintains nearly optimal performance even in this more challenging setting.

The recent measurement by the CDF Collaboration of the $W$-boson mass is in significant tension with the Standard Model expectation, showing a discrepancy of seven standard deviations. A larger value of $m_W$ affects the global electroweak fit, particularly the best-fit values of the Peskin-Takeuchi parameters $S$, $T$ (and perhaps $U$) that measure oblique corrections from new physics. To meet this challenge, we propose some simple models capable of generating non-negative $S$ and $T$, the latter of which faces the greatest upward pressure from the CDF measurement in scenarios with $U=0$. Our models feature weak multiplets of scalars charged under $\mathrm{SU}(3{)}_{\mathrm{c}}\times \mathrm{U}(1{)}_Y$, which cannot attain nonzero vacuum expectation values but nevertheless produce, e.g., $T\ne 0$ given some other mechanism to split the electrically charged and neutral scalars. We compute the oblique corrections in these models and identify ample parameter space supporting the CDF value of $m_W$.

We explore higher-derivative terms in the low-energy effective action for the dilaton, the Goldstone boson of spontaneously broken scale invariance. Focusing on the simplest holographic realization of spontaneously broken scale invariance, the Randall-Sundrum (RS) scenario, we identify the nonlinear action for the RS dilaton by integrating out Kaluza-Klein graviton modes. The coefficient of a particular fourth-derivative dilaton self-interaction can be identified with the Weyl $a$-anomaly of the dual conformal field theory, which we use to verify anomaly matching arguments. We also find novel, $a$-dependent couplings of the dilaton to light matter fields. These anomalous interactions can have a significant effect on the collider phenomenology and the cosmology, potentially allowing us to probe the structure of the underlying conformal sector via low-energy physics. The dilaton effective theory also serves as an interesting scalar analog of gravity, and we study solutions to the equation of motion that parallel black holes and cosmologies.

Experimental hints for lepton flavor universality violation in beauty-quark decay both in neutral- and charged-current transitions require an extension of the Standard Model for which scalar leptoquarks (LQs) are the prime candidates. Besides, these same LQs can resolve the long-standing tension in the muon and the recently reported deviation in the electron $g-2$ anomalies. These tantalizing flavor anomalies have discrepancies in the range of $2.5\sigma -4.2\sigma$, indicating that the Standard Model of particle physics may finally be cracking. In this Article, we propose a resolution to all these anomalies within a unified framework that sheds light on the origin of neutrino mass. In this model, the LQs that address flavor anomalies run through the loops and generate neutrino mass at the two-loop order while satisfying all constraints from collider searches, including those from flavor physics.

Using a fully relativistic lattice fermion action, we compute the form factors of the semileptonic decay $B\to \pi \ell \nu$, which is required for the determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$. We employ the Möbius domain-wall fermion formalism for the generation of lattice ensembles with $2+1$ sea quark flavors as well as for the valence heavy and light quarks. We compute the form factors at various values of the lattice spacing and multiple light and heavy quark masses, and extrapolate the results to the physical point. We combine our lattice results with the available experimental data to obtain $|V_{ub}|=(3.93\pm 0.41)\times {10}^{-3}$.

We present results for the thermal photon emissivity of the quark-gluon plasma derived from spatially transverse vector correlators computed in lattice QCD at a temperature of 250 MeV. The analysis of the spectral functions, performed at fixed spatial momentum, is based on continuum-extrapolated correlators obtained with two flavors of dynamical Wilson fermions. We compare the next-to-leading-order perturbative QCD correlators, as well as the $\mathcal{N}=4$ supersymmetric Yang-Mills correlators at infinite coupling, to the correlators from lattice QCD and find them to lie within $\sim 10\%$ of each other. We then refine the comparison, performing it at the level of filtered spectral functions obtained model-independently via the Backus-Gilbert method. Motivated by these studies, for frequencies $\omega \lesssim 2.5\mathrm{GeV}$ we use fit Ansätze to the spectral functions that perform well when applied to mock data generated from the NLO QCD or from the strongly coupled SYM spectral functions, while the high-frequency part, $\omega \gtrsim 2.5\mathrm{GeV}$, is matched to NLO QCD. We compare our results for the photon emissivity to our previous analysis of a different vector channel at the same temperature. We obtain the most stringent constraint at photon momenta around $k\simeq 0.8\mathrm{GeV}$, for which we find a differential photon emission rate per unit volume of $\mathrm{d}{\mathrm{\Gamma }}_{\gamma }/{\mathrm{d}}^{3}k=({\alpha }_{\mathrm{em}}/(\exp (k/T)-1))\times (2.2\pm 0.8)\times {10}^{-3}\mathrm{GeV}$.

We discuss a novel approach to estimate the partition function in effective model frameworks when the effective potentials have multiple extrema, so that ascertaining a mean field becomes difficult. Using this approach we present a consistent model to study the thermodynamic properties of gluon quasiparticles as a function of temperature, both in the color confined and the color deconfined phases.