We consider the correlator of two concentric circular Wilson loops with equal radii for arbitrary spatial and internal separation at strong coupling within a defect version of $\mathcal{N}=4$ SYM. Compared to the standard Gross-Ooguri phase transition between connected and disconnected minimal surfaces, a more complicated pattern of saddle points contributes to the two-circles correlator due to the defect’s presence. We analyze the transitions between different kinds of minimal surfaces and their dependence on the setting’s numerous parameters.

We consider a multiscalar field theory either with short-range or long-range free action and with quartic interactions that are invariant under $O(N_1)\times O(N_2)\times O(N_3)$ transformations, of which the scalar fields form a trifundamental representation. We study the renormalization group fixed points at two loops at finite $N$ and in various large-$N$ scaling limits for small $\epsilon$, the latter being the deviation either from the critical dimension or from the critical scaling of the free propagator. In particular, for the homogeneous case $N_i=N$ for $i=1$, 2, 3, we study the subleading corrections to previously known fixed points. In the short-range model, for $\epsilon N^2\gg 1$, we find complex fixed points with nonzero tetrahedral coupling that at leading order reproduce the results of Giombi et al. [Phys. Rev. D 96, 106014 (2017).]; the main novelty at next-to-leading order is that the critical exponents acquire a real part, thus allowing a correct identification of some fixed points as IR stable. In the long-range model, for $\epsilon N\ll 1$, we find again complex fixed points with nonzero tetrahedral coupling that at leading order reproduce the line of stable fixed points of Benedetti et al. [J. High Energy Phys. 06 (2019) 053]; at next-to-leading order, this is reduced to a discrete set of stable fixed points. One difference between the short-range and the long-range cases is that in the former the critical exponents are purely imaginary at leading order and gain a real part at next-to-leading order, while for the latter the situation is reversed.

We propose a gravity dual description of the path integral optimization in conformal field theories [Caputa et al., Phys. Rev. Lett. 119, 071602 (2017)], using Hartle-Hawking wave functions in anti–de Sitter spacetime. We show that the maximization of the Hartle-Hawking wave function is equivalent to the path integral optimization procedure. Namely, the variation of the wave function leads to a constraint, equivalent to the Neumann boundary condition on a bulk slice, whose classical solutions reproduce metrics from the path integral optimization in conformal field theories. After taking the boundary limit of the semiclassical Hartle-Hawking wave function, we reproduce the path integral complexity action in two dimensions, as well as its higher- and lower-dimensional generalizations. We also discuss an emergence of holographic time from conformal field theory path integrals.

We study the effect of cubic and tidal interactions on the spectrum of gravitational waves emitted in the inspiral phase of the merger of two nonspinning objects. There are two independent parity-even cubic interaction terms, which we take to be $I_1={R^{\alpha \beta }}_{\mu \nu }{R^{\mu \nu }}_{\rho \sigma }{R^{\rho \sigma }}_{\alpha \beta }$ and $G_3=I_1-2{{{R^{\alpha }}_{\mu }}^{\beta }}_{\nu }{{{R^{\mu }}_{\rho }}^{\nu }}_{\sigma }{{{R^{\rho }}_{\alpha }}^{\sigma }}_{\beta }$. The latter has vanishing pure graviton amplitudes but modifies mixed scalar/graviton amplitudes which are crucial for our study. Working in an effective field theory setup, we compute the modifications to the quadrupole moment due to $I_1$, $G_3$ and tidal interactions, from which we obtain the power of gravitational waves radiated in the process to first order in the perturbations and leading order in the post-Minkowskian expansion. The $I_1$ predictions are novel, and we find that our results for $G_3$ are related to the known quadrupole corrections arising from tidal perturbations, although the physical origin of the $G_3$ coupling is unrelated to the finite-size effects underlying tidal interactions. We show this by recomputing such tidal corrections and by presenting an explicit field redefinition. In the post-Newtonian expansion our results are complete at leading order, which for the gravitational-wave flux is 5PN for $G_3$ and tidal interactions and 6PN for $I_1$. Finally, we compute the corresponding modifications to the waveforms.

Thomas-Whitehead (TW) gravity is a projectively invariant model of gravity over a d-dimensional manifold that is intimately related to string theory through reparametrization invariance. Unparametrized geodesics are the ubiquitous structure that ties together string theory and higher dimensional gravitation. This is realized through the projective geometry of Tracy Thomas. The projective connection, due to Thomas and later Whitehead, admits a component that in one dimension is in one-to-one correspondence with the coadjoint elements of the Virasoro algebra. This component is called the diffeomorphism field ${\mathcal{D}}_{ab}$ in the literature. It also has been shown that in four dimensions, the TW action collapses to the Einstein-Hilbert action with cosmological constant when ${\mathcal{D}}_{ab}$ is proportional to the Einstein metric. These previous results have been restricted to either particular metrics, such as the Polyakov 2D metric, or were restricted to coordinates that were volume preserving. In this paper, we review TW gravity and derive the gauge invariant TW action that is explicitly projectively invariant and general coordinate invariant. We derive the covariant field equations for the TW action and show how fermionic fields couple to the gauge invariant theory. The independent fields are the metric tensor $g_{ab}$, the fundamental projective invariant ${{\mathrm{\Pi }}^a}_{bc}$, and the diffeomorphism field ${\mathcal{D}}_{ab}$.

Scalar fields around compact objects are of interest for scalar-tensor theories of gravity and dark matter models consisting of a massive scalar, e.g., axions. We study the behavior of a scalar field around a Kerr black hole with nontrivial asymptotic boundary conditions—both nonzero density and nonzero angular momentum. Starting from an initial radially homogeneous configuration, a scalar cloud is accreted, which asymptotes to known stationary configurations over time. We study the cloud growth for different parameters including black hole spin, scalar field mass, and the scalar field density and angular momentum far from the black hole. We characterize the transient growth of the mass and angular momentum in the cloud, and the spatial profile of the scalar around the black hole, and relate the results of fully nonlinear simulations to an analytic perturbative expansion. We also highlight the potential for these accreted clouds to create monochromatic gravitational wave signals—similar to the signals from superradiant clouds, although significantly weaker in amplitude.

Axially symmetric spacetimes play an important role in the relativistic description of rotating astrophysical objects like black holes, stars, etc. In gravitational theories that venture beyond the usual Riemannian geometry by allowing independent connection components, the notion of symmetry concerns, not just the metric, but also the connection. As discovered recently, in teleparallel geometries, axial symmetry can be realized in two branches, while only one of these has a continuous spherically symmetric limit. In the current paper, we consider a very generic $f(T,B,\varphi ,X)$ family of teleparallel gravities, whose action depends on the torsion scalar $T$ and the boundary term $B$, as well as a scalar field $\varphi$ with its kinetic term $X$. As the field equations can be decomposed into symmetric and antisymmetric (spin connection) parts, we thoroughly analyze the antisymmetric equations and look for solutions of axial spacetimes which could be used as ansätze to tackle the symmetric part of the field equations. In particular, we find solutions corresponding to a generalization of the Taub-NUT metric, and the slowly rotating Kerr spacetime. Since this work also concerns a wider issue of how to determine the spin connection in teleparallel gravity, we also show that the method of “turning off gravity” proposed in the literature, does not always produce a solution to the antisymmetric equations.

Taking QED effect into account, we investigate the shadows of a static black hole with magnetic monopoles and neutral black holes in magnetic fields through the numerical backward ray-tracing method. For a static black holes with a magnetic monopole, we obtain the relation between the shadow radius and the coupling constant. For neutral black holes in uniform magnetic fields, we find that the shadow curves deviate very little from the ellipses for an equatorial observer, and we read the linear relation between the eccentricity and the coupling constant. For ${\theta }_o\ne \pi /2$, we find that the shadow curves can be well approximated by ellipses in most cases, except when the magnetic field is very strong and the observer sits around the angle ${\theta }_o=\pi /4$ or $3\pi /4$. Moreover, we extend our investigation to a neutral static black hole surrounded by a current loop.

An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. The behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet’s angular momentum is dominated by atomic electron spins and is predicted to exhibit macroscopic gyroscopic behavior. If such a ferromagnetic gyroscope is sufficiently isolated from the environment, rapid averaging of quantum uncertainty via the spin-lattice interaction enables readout of the ferromagnetic gyroscope dynamics with sufficient sensitivity to measure both the Lense-Thirring (frame dragging) and de Sitter (geodetic precession) effects due to the Earth.

We construct models of Einstein and $f(R)$ gravity with two scalar fields, which admit analytical solutions describing time-varying dynamical black holes. Their thermodynamics is investigated in the adiabatic approximation. In addition to the Misner-Sharp-Hernandez quasilocal mass, we provide time-dependent thermodynamical quantities, including the Hawking temperature, Helmholtz free energy, entropy, and thermodynamical energy. The latter does not always coincide with the Misner-Sharp-Hernandez mass at the horizon, although they coincide in the static limit. For Schwarzschild-type (i.e., $g_{tt}{g}_{rr}=-1$) black holes in Einstein gravity, one of the two scalars is always a ghost with negative kinetic energy. We show that this ghost can be avoided in $f(R)$ gravity.

We assess the prospects for detecting the moving lens effect using cosmological surveys. The bulk motion of cosmological structure induces a small-scale dipolar temperature anisotropy of the cosmic microwave radiation, centered around halos and oriented along the transverse velocity field. We introduce a set of optimal filters for this signal and forecast that a high significance detection can be made with upcoming experiments. We discuss the prospects for reconstructing the bulk transverse velocity field on large scales using matched filters, finding good agreement with previous work using quadratic estimators.

The cosmic microwave background (CMB) is gravitationally lensed by large-scale structure, which distorts observations of the primordial anisotropies in any given direction. Averaged over the sky, this important effect is routinely modeled with the lensed CMB power spectra. This accounts for the variance of this distortion, where the leading variance effect is quadratic in the lensing deflections. However, we show that if bright extragalactic sources correlated with the large-scale structure are masked in a CMB map, the power spectrum measured over the unmasked area using a standard pseudo-$C_{\ell }$ estimator has an additional linear lensing effect arising from correlations between the masked area and the lensing. This induces a scale-dependent average demagnification of the unlensed distance between unmasked pairs of observed points and a negative contribution to the CMB correlation function peaking at $\sim 10\mathrm{arcmin}$. We give simple analytic models for point sources and a threshold mask constructed on a correlated Gaussian foreground field. We demonstrate the consistency of their predictions for masks removing radio sources and peaks of Sunyaev-Zeldovich and cosmic infrared background emissions using realistic numerical simulations. We discuss simple diagnostics that can be used to test for the effect in the absence of a good model for the masked sources and show that by constructing specific masks the effect can be observed on Planck data. For masks employed in the analysis of Planck and other current data sets, the effect is likely to be negligible, but may become an important subpercent correction for future surveys if substantial populations of resolved sources are masked.

Coherent forward scattering processes by neutrino-scalar nonstandard interactions (SNSI) induce an effective neutrino mass. In the early Universe, a large neutrino effective mass restricts the production of neutrinos. The SNSI effect is modulated by two effective couplings; these account for the coupling between neutrinos and electrons or positrons, $G_{\mathrm{eff}}$, and the neutrino self-interaction $G_{\mathrm{S}}$. These parameters are directly related to the effective number of relativistic species, and nonzero values imply a smaller than expected $N_{\mathrm{eff}}$. We employ big bang nucleosynthesis to constraint the SNSI effect. We find that $G_{\mathrm{eff}}<1.2{\mathrm{MeV}}^{-2}$ and $G_{\mathrm{S}}<2.0\times {10}^7{\mathrm{MeV}}^{-2}$ at 68% C.L. For a scalar mass in the range ${10}^{-15}\mathrm{eV}\lesssim m_{\varphi }\lesssim {10}^{-5}\mathrm{eV}$, our neutrino-scalar coupling constraint is more restrictive than any previous result.

We investigate in detail a family of quintessential inflation models in the context of $R+R^2$ Palatini modified gravity. We find that successful inflation and quintessence are obtained with an inflaton scalar potential that is approximately quadratic in inflation and inverse quartic in quintessence. We show that corrections for the kination period due to Palatini modified gravity are subdominant, while the setup does not challenge constraints on modified gravity from Solar System observations and microscopic experiments, in contrast to the metric case. We obtain concrete predictions regarding primordial tensors to be probed in the near future.

We apply machine learning methods to build a time-domain model for gravitational waveforms from binary black hole mergers, called mlgw. The dimensionality of the problem is handled by representing the waveform’s amplitude and phase using a principal component analysis. We train mlgw on about $\mathcal{O}({10}^3)$ teobresums and seobnrv4 effective-one-body waveforms with mass ratios $q\in [1,20]$ and aligned dimensionless spins $s\in [-0.80,0.95]$. The resulting models are faithful to the training sets at the $\sim {10}^{-3}$ level (averaged on the parameter space). The speed up for a single waveform generation is a factor of 10–50 (depending on the binary mass and initial frequency) for teobresums and approximately an order of magnitude more for seobnrv4. Furthermore, mlgw provides a closed form expression for the waveform and its gradient with respect to the orbital parameters; such an information might be useful for future improvements in gravitational wave (GW) data analysis. As demonstration of the capabilities of mlgw to perform a full parameter estimation, we reanalyze the public data from the first GW transient catalog (GWTC-1). We find broadly consistent results with previous analyses at a fraction of the cost, although the analysis with spin-aligned waveforms gives systematic larger values of the effective spins with respect to previous analyses with precessing waveforms. Since the generation time does not depend on the length of the signal, our model is particularly suitable for the analysis of the long signals that are expected to be detected by third-generation detectors. Future applications include the analysis of waveform systematics and model selection in parameter estimation.

A promising probe to unmask particle dark matter is to observe its effect on neutron stars, the prospects of which depend critically on whether captured dark matter thermalizes in a timely manner with the stellar core via repeated scattering with the Fermi-degenerate medium. In this work we estimate the timescales for thermalization for multiple scenarios. These include: (a) spin-0 and spin-$\frac{1}{2}$ dark matter, (b) scattering on nonrelativistic neutron and relativistic electron targets accounting for the respective kinematics, (c) interactions via a range of Lorentz-invariant structures, (d) mediators both heavy and light in comparison to the typical transfer momenta in the problem. We discuss the analytic behavior of the thermalization time as a function of the dark matter and mediator masses, and the stellar temperature. Finally, we identify parametric ranges where both stellar capture is efficient and thermalization occurs within the age of the universe. For dark matter that can annihilate in the core, these regions indicate parametric ranges that can be probed by upcoming infrared telescopes observing cold neutron stars.

The observation of cosmic sub-PeV gamma rays from the Crab Nebula opens up the possibility of testing cosmic ray photon transparency at the multi-hundred-TeV scale. Assuming no deviation from a source gamma-ray emission due to accelerated electron inverse-Compton scattering, higher event energies can extend constraints on the effects of new physics; we consider oscillation between gamma rays and axions, plus attenuation effects from gamma-ray absorption in the case of dark photon dark matter. Combining the recent $\mathrm{AS}\gamma$ and HAWC sub-PeV data with earlier MAGIC and HEGRA data, axionlike particles are most constrained in the $2\times {10}^{-7}–6\times {10}^{-7}\mathrm{eV}$ mass range, where the coupling $g_{a\gamma \gamma }$ is constrained to be below $1.8\times {10}^{-10}{\mathrm{GeV}}^{-1}$. Direct scattering from dark photon dark matter limits kinetic mixing $\epsilon \lesssim {10}^{-3}$ for masses between 0.01 and 1 eV.

We present a detailed modeling and computation methodology to determine the optical Cherenkov signals produced by upward-moving extensive air showers (EASs) induced by $\tau$-leptons and muons, sourced from the interaction of high-energy astrophysical neutrinos interacting in the Earth. Following and extending the physics modeling and Cherenkov signal simulations performed in M. H. Reno et al. [Phys. Rev. D 100, 063010 (2019)], this scheme encompasses a new, state-of-the-art computation of the muon neutrino propagation inside the Earth and the contribution to the $\tau$-lepton muon decay channel. The modeling takes into account all possible $\tau$-lepton decay and muon energy loss channels that feed the optical Cherenkov emission, produced by both tau and muon initiated EASs. The EAS modeling uses the electron energy, angular, and lateral distributions in the EAS and their evolution as well as the wavelength dependence of the Cherenkov emission and its atmospheric attenuation. The results presented here are focused on the detection capabilities of suborbital (balloon-borne) and orbital (satellite) based instruments. The latter case was calculated for POEMMA [The Probe Of Extreme MultiMessenger Astrophysics] to compare to that presented in M. H. Reno et al. [Phys. Rev. D 100, 063010 (2019)], specifically including the muon-decay channel of $\tau$-leptons and the muonic EAS Cherenkov signal from muon neutrino interactions in the Earth. By detailing all these individual contributions to the optical Cherenkov emission and detection, we show how the ensemble that includes muonic channels provides a large detection capability for space-based, high-energy cosmic neutrino detection. Specifically, we show that for neutrino energies $\lesssim 10\mathrm{PeV}$, the upward-EAS sensitivity due to muon neutrino interactions in the Earth begin to dominate over that for tau neutrino interactions, effectively extending the neutrino sensitivity to lower energies.

Nonlinear Compton scattering is calculated for the collision of an electron with a plane-wave pulse. A midinfrared (IR) peak arises in the photon spectrum due to long-range interference associated with the pulse envelope. The case of a flattop pulse is studied as a toy model for pulse envelope effects and reduced to two final-state momentum integrations; the case of a sine-squared pulse is studied numerically. A perturbative expansion in charge-field coupling reveals that already at intermediate intensities, many orders are required to correctly capture the structure of the mid-IR peak. By regularizing the classical result, it is shown that the mid-IR peak is due to plane-wave ponderomotive effects from the pulse envelope. Finally, it is shown that the mid-IR peak can be isolated using energy, angle and polarization filters.

We propose a simple model in which dark matter particle exchanges mediate a new quantum force between muons and nucleons, resolving the proton charge radius puzzle. At the same time, the discrepancy between the measured anomalous magnetic moment of the muon and the Standard Model prediction can be accommodated, and thermal relic abundance of the dark matter candidate is consistent with observations. The dark matter particle mass is in the MeV range. We show that the model is consistent with a variety of experimental and observational constraints.