We introduce a class of polytopes that concisely capture the structure of UV and IR divergences of general Feynman integrals in Schwinger parameter space, treating them in a unified way as worldline segments shrinking and expanding at different relative rates. While these polytopes conventionally arise as convex hulls—via Newton polytopes of Symanzik polynomials—we show that they also have a remarkably simple dual description as cut out by linear inequalities defining the facets. It is this dual definition that makes it possible to transparently understand and efficiently compute leading UV and IR divergences for any Feynman integral. In the case of the UV, this provides a transparent geometric understanding of the familiar nested and overlapping divergences. In the IR, the polytope exposes a new perspective on soft/collinear singularities and their intricate generalizations. Tropical geometry furnishes a simple framework for calculating the leading UV/IR divergences of any Feynman integral, associating them with the volumes of certain dual cones. As concrete applications, we generalize Weinberg’s theorem to include a characterization of IR divergences, and classify space-time dimensions in which general IR divergences (logarithmic as well as power-law) can occur. We also compute the leading IR divergence of rectangular fishnet diagrams at all loop orders, which turn out to have a surprisingly simple combinatorial description.

The loss of time-translational invariance caused by a time-dependent external agent leads to particle creation effects in quantum field theory. This phenomenon results in ambiguities when selecting the quantum vacuum of the canonical quantization. In this work we analyze how the time evolution of the number of created particles depends on these ambiguities when external agents are spatially homogeneous. In particular, we generalize the standard quantum Vlasov equation in order to accommodate in its formulation the possibility of having different choices of vacuum, including adiabatic vacua. This study leads us to propose a new physical criterion stronger than the unitary implementation of the dynamics in order to reduce the quantization ambiguities.

Recently, a novel emergent phase can occur from thermodynamic consideration of the asymptotically flat Reissner-Nordström black hole (RN-AF) using Rényi statistics. We present an analysis of the thermodynamical and mechanical stabilities of the RN-AF in both the Gibbs-Boltzmann (GB) and the alternative Rényi statistics when charge $q$ and electrostatic potential $\varphi$ are treated as pressure and volume, respectively. Interestingly, the emergent phase of the RN-AF can be both thermodynamically and mechanically stable in some range of parameters in the framework of Rényi thermodynamics. With the construction of the Maxwell equal area law in $q-\varphi$ plane, the coexistence line between the near-extremal black hole phase and the emergent phase can be found in some values of charge which can be associated as the vapor pressure at which the liquid and gas phases coexist. In the aspect of thermodynamic geometry, the microscopic interaction between the black hole microstructures can be repulsive in the Rényi description. This implies that a novel correlation between the microstates of a self-gravitating system could be emerged via the nonextensive nature of long-range interaction systems. Finally, we also investigate the critical phenomena of the RN-AF in Rényi statistics compared to that of the van der Waals (vdW) fluid and find that the critical exponents of the relevant physical quantities of both systems are identical. This implies that both systems are in the same universality class of the phase transition.

Despite their potential role as massive seeds for quasars, in dwarf galaxy feedback, and in tidal disruption events, the observational evidence for intermediate-mass black holes (IMBHs) is scarce. LISA may observe stellar-mass black hole binaries orbiting galactic IMBHs and reveal the presence of the IMBH by measuring the Doppler shift in the gravitational waveform induced by the binary’s radial velocity. We estimate the number of detectable Doppler shift events from the Milky Way globular clusters (assuming they host IMBHs), and we find that it decreases with the IMBH mass. A few galactic globular clusters (including M22 and $\omega$ Centauri) may produce at least one event detectable by LISA. Even in more pessimistic scenarios, one could still expect $\sim 1$ event overall in the Milky Way. We also estimate the number of Doppler shift events for IMBHs wandering in the Milky Way as a result of the disruption of their parent clusters. If there is at least one binary black hole orbiting around each wandering IMBH, LISA may detect up to a few tens of Doppler shift events from this elusive IMBH population. Under more pessimistic assumptions, LISA may still detect $\sim 1$ wandering IMBH that would hardly be observable otherwise.

Gravitational wave observations have great potential to reveal new information about the fundamental nature of gravity, but extracting that information can be difficult. One popular technique is the parametrized inspiral test of general relativity (a realization of the parametrized post-Einsteinian framework), where the gravitational waveform, as calculated in Einstein’s theory as a series expansion in the orbital velocity, is parametrically deformed at a given set of orders in velocity. However, most current approaches usually only analyze the data while considering a single, specific modification at a time. Are then constraints placed with a single modification robust to our ignorance of higher post-Newtonian order corrections? We show here that for a wide class of theories, specifically those that admit a post-Newtonian expansion, single-parameter tests are indeed robust. In particular, through a series of full Bayesian parameter estimation studies on several different sets of synthetic data, we show that single-parameter constraints are not degraded but rather are improved by the inclusion of multiple parameters, provided one includes information about the mathematical structure of the series. We then exemplify this with a specific theory of gravity, shift-symmetric scalar Gauss-Bonnet theory, where the waveform has been calculated to higher post-Newtonian orders than leading. We show that the inclusion of these higher order terms strengthens single-parameter constraints, instead of weakening them, and that the strengthening is very mild. This analysis therefore provides strong evidence that single-parameter post-Einsteinian tests of general relativity are robust to ignorance of high post-Newtonian order terms in the general relativistic deformations.

We numerically explore the structure of quasinormal (QN) frequencies of the five-dimensional small and large Kerr-anti–de Sitter (Kerr-${\mathrm{AdS}}_5$) black hole with equal and unequal rotations. Our investigation also covers low and high Hawking temperatures. We then study the stability of the Kerr-${\mathrm{AdS}}_5$ black hole and the structure of highly damped QN modes, which would reflect the thermodynamic property of the Kerr-${\mathrm{AdS}}_5$ black hole. We find that the highly damped complex QN frequencies of a nearly maximally spinning Kerr-${\mathrm{AdS}}_5$ black hole have the periodic separation of the surface gravity at the horizon in the imaginary part while the real part converges to the superradiant frequency, which may be relevant to the pole structure of the thermal Green’s function in the corresponding conformal field theory on the Kerr-${\mathrm{AdS}}_5$ boundary. Finally, we discuss a relation between the QN modes of the Kerr-${\mathrm{AdS}}_5$ black hole and the Hod’s conjecture on the horizon area quantization along with the analysis of the horizon topology of the Kerr-${\mathrm{AdS}}_5$ black hole. We show that in general, an ultraspinning Kerr-${\mathrm{AdS}}_5$ black hole, whose spin parameter is infinitesimally close to the AdS curvature radius, has its noncompact horizon, and based on the Hod’s conjecture, we argue that the horizon area may be continuous, that is, the unit area of the horizon vanishes in the ultraspinning regime.

We consider the Penrose process near the naked singularity in the Reissner-Nordström metric. Particle 0 falls from infinity and decays to two fragments at some point $r_0$. We show that the energy extraction due to this process can be indefinitely large in the limit $r_0\to 0$. In doing so, the value of the particle charge can remain bounded, in contrast to the previously known examples of the Penrose process in the electric field with unbounded energy extraction. The effect persists even in the limit of the flat space-time. Uhbounded energy gain is obtained in the standard (not collisional) Penrose process and does not require fine-tuning of particle parameters or characteristics of space-time.

White dwarfs (WDs) and neutron stars (NSs) are among the most magnetized astrophysical objects in the universe, with magnetic fields that can reach up to ${10}^9\mathrm{G}$ for WDs and up to ${10}^{15}\mathrm{G}$ for NSs. The galaxy is expected to be populated with approximately one hundred million of double WD and millions of NS-WD binaries. Throughout the duration of the mission, the Laser Interferometer Space Antenna (LISA) will observe gravitational waves (GWs) emitted simultaneously by more than ten thousand of such galactic binaries. In this paper, we investigate the effect of the magnetic dipole-dipole interaction on the GW signal emitted by magnetic galactic binaries. We derive the secular equations governing the orbital and rotational motion of these objects. Then, we integrate these equations both numerically and analytically. We conclude that the overall visible effect is an additional secular drift of the mean longitude. This drift is proportional to the product of the magnetic moments and is inversely proportional to the $7/2$ power of the semimajor axis. Finally, we show that, at zeroth-order in eccentricity, the magnetic dipole-dipole interaction shifts the main frequency of the gravitational strain measured by LISA.

In this paper, we continue our study of the motion of spinning test bodies orbiting Kerr black holes. Nonspinning test bodies follow geodesics of the spacetime in which they move. A test body’s spin couples to the curvature of that spacetime, introducing a “spin-curvature force” which pushes the body’s worldline away from a geodesic trajectory. The spin-curvature force is an important example of a postgeodesic effect which must be modeled carefully in order to accurately characterize the motion of bodies orbiting black holes. One motivation for this work is to understand how to include such effects in models of gravitational waves produced from the inspiral of stellar mass bodies into massive black holes. In this paper’s predecessor, we describe a technique for computing bound orbits of spinning bodies around black holes with a frequency-domain description which can be solved very precisely. In that paper, we present an overview of our methods, as well as present results for orbits which are eccentric and nearly equatorial (i.e., the orbit’s motion is no more than $\mathcal{O}(S)$ out of the equatorial plane). In this paper, we apply this formulation to the fully generic case—orbits which are inclined and eccentric, with the small body’s spin arbitrarily oriented. We compute the trajectories which such orbits follow, and compute how the small body’s spin affects important quantities such as the observable orbital frequencies ${\mathrm{\Omega }}_r$, ${\mathrm{\Omega }}_{\theta }$ and ${\mathrm{\Omega }}_{\varphi }$.

Very large mass ratio binary black hole systems are of interest both as a clean limit of the two-body problem in general relativity, as well as for their importance as sources of low-frequency gravitational waves. At lowest order, the smaller body moves along a geodesic of the larger black hole’s spacetime. Accurate models of such systems require postgeodesic corrections to this motion. Postgeodesic effects that drive the small body away from the geodesic include the gravitational self-force, which incorporates the backreaction of gravitational-wave emission, and the spin-curvature force, which arises from coupling of the small body’s spin to the black hole’s spacetime curvature. In this paper, we describe a method for precisely computing bound orbits of spinning bodies about black holes. Our analysis builds off of pioneering work by Witzany which demonstrated how to describe the motion of a spinning body to linear order in the small body’s spin. Exploiting the fact that in the large mass-ratio limit spinning-body orbits are close to geodesics (in a sense that can be made precise) and using closed-form results due to van de Meent describing precession of the small body’s spin along black hole orbits, we develop a frequency-domain formulation of the motion which can be solved very precisely. We examine a range of orbits with this formulation, focusing in this paper on orbits which are eccentric and nearly equatorial (i.e., the orbit’s motion is $\mathcal{O}(S)$ out of the equatorial plane), but for which the small body’s spin is arbitrarily oriented. We discuss generic orbits with general small-body spin orientation in a companion paper. We characterize the behavior of these orbits, contrasting them with geodesics, and show how the small body’s spin shifts the frequencies ${\mathrm{\Omega }}_r$ and ${\mathrm{\Omega }}_{\varphi }$ which affect orbital motion. These frequency shifts change accumulated phases which are direct gravitational-wave observables, illustrating the importance of precisely characterizing these quantities for gravitational-wave observations.

Hot, ionized gas leaves an imprint on the cosmic microwave background via the thermal Sunyaev-Zel’dovich (tSZ) effect. The cross-correlation of gravitational lensing (which traces the projected mass) with the tSZ effect (which traces the projected gas pressure) is a powerful probe of the thermal state of ionized baryons throughout the Universe and is sensitive to effects such as baryonic feedback. In a companion paper (Gatti et al. Phys. Rev. D 105, 123525 (2022)), we present tomographic measurements and validation tests of the cross-correlation between Galaxy shear measurements from the first three years of observations of the Dark Energy Survey and tSZ measurements from a combination of Atacama Cosmology Telescope and Planck observations. In this work, we use the same measurements to constrain models for the pressure profiles of halos across a wide range of halo mass and redshift. We find evidence for reduced pressure in low-mass halos, consistent with predictions for the effects of feedback from active Galactic nuclei. We infer the hydrostatic mass bias ($B\equiv M_{500c}/M_{\mathrm{SZ}}$) from our measurements, finding $B=1.8\pm 0.1$ when adopting the Planck-preferred cosmological parameters. We additionally find that our measurements are consistent with a nonzero redshift evolution of $B$, with the correct sign and sufficient magnitude to explain the mass bias necessary to reconcile cluster count measurements with the Planck-preferred cosmology. Our analysis introduces a model for the impact of intrinsic alignments (IAs) of galaxy shapes on the shear-tSZ correlation. We show that IA can have a significant impact on these correlations at current noise levels.

We present a tomographic measurement of the cross-correlation between thermal Sunyaev-Zel’dovich (TSZ) maps from Planck and the Atacama Cosmology Telescope and weak galaxy lensing shears measured during the first three years of observations of the Dark Energy Survey. This correlation is sensitive to the thermal energy in baryons over a wide redshift range and is therefore a powerful probe of astrophysical feedback. We detect the correlation at a statistical significance of $21\sigma$, the highest significance to date. We examine the TSZ maps for potential contaminants, including cosmic infrared background and radio sources, finding that cosmic infrared background has a substantial impact on our measurements and must be taken into account in our analysis. We use the cross-correlation measurements to test different feedback models. In particular, we model the TSZ using several different pressure profile models calibrated against hydrodynamical simulations. Our analysis marginalizes over redshift uncertainties, shear calibration biases, and intrinsic alignment effects. We also marginalize over ${\mathrm{\Omega }}_{\mathrm{m}}$ and ${\sigma }_8$ using Planck or DES priors. We find that the data prefer the model with a low amplitude of the pressure profile at small scales, compatible with a scenario with strong active galactic nuclei feedback and ejection of gas from the inner part of the halos. When using a more flexible model for the shear profile, constraints are weaker, and the data cannot discriminate between different baryonic prescriptions.

The anti–de Sitter (AdS) black hole plays an important role in the holographic principle. In this study, the upper bound in energy corresponding to the mass of the Schwarzschild black hole is modified to be that of the AdS black hole. Via the correspondence between the ultraviolet and infrared cutoffs, the constant term in the energy density of the holographic dark energy can be obtained from the negative cosmological constant from the black hole. Interestingly, the proposed dark energy model could drive the late-time expansion of the Universe without the causality violation. The cosmic evolution is investigated by choosing the Hubble and particle horizons as the IR length scales. It is found that the accelerated expansion at late time can be obtained for both cases. The likelihood analysis on the model parameters is also performed. This result may shed light on the connection between the AdS black hole and the de Sitter (dS) spacetime in the context of cosmology.

Cosmic flexion, like cosmic shear, is a correlation function whose signal originates from the large-scale structure of the Universe. Building on the observational success of cosmic shear, along with the unprecedented quality of large-scale cosmological datasets, the time is ripe to explore the practical constraints from cosmic flexion. Unlike cosmic shear, which has a broad window function for power, cosmic flexion is only measurable on small scales and therefore can uniquely place constraints on the small-scale matter power spectrum. Here, we present a full theoretical formalism for cosmic flexion, including both flexion-flexion and shear-flexion two-point correlations. We present forecasts for measuring cosmic flexion in the Dark Energy Survey (DES), a stage III cosmological survey, and comment on the future prospects of measuring these cosmological flexion signals in the upcoming era of stage IV experiments.

Primordial black holes (PBHs) can form as a result of primordial scalar perturbations at small scales. This PBH formation scenario has associated gravitational wave (GW) signatures from second-order GWs induced by the primordial curvature perturbation, and from GWs produced during an early PBH dominated era. We investigate the ability of next generation GW experiments, including BBO, LISA, and CE, to probe this PBH formation scenario in a wide mass range. Measuring the stochastic GW background with GW observatories can constrain the allowed parameter space of PBHs for masses ${10}^9–{10}^{27}\mathrm{g}$. We also discuss possible GW sources from an unconstrained region where light PBHs ($<{10}^9\mathrm{g}$) temporarily dominate the energy density of the universe before evaporating. We show how PBH formation impacts the reach of GW observatories to the primordial power spectrum and provide constraints implied by existing PBH bounds.

The LIGO-Virgo collaboration reported in their third run the coalescence event GW190814 involving a $2.6M_{\odot }$ object with a $23M_{\odot }$ black hole. In this article we study the conditions under which Thorne-Żytkow objects (TŻOs) can be connected to that type of event. We evaluate first the rate of appearance of TŻOs in the local Universe. Under the assumption that TŻOs eventually become low mass gap black holes we evaluate how those black holes end up in binaries with other stellar mass black holes and compare to the reported rate for GW190814-type of events ($1–23{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$). We find that TŻOs in dense stellar clusters can not explain the LIGO-Virgo rate without a TŻO population in the field providing a dominant contribution. We also find that TŻOs formed within hierarchical triple systems in the field with the third more distant star being the progenitor of a stellar mass black hole may be able to give a rate comparable to that of GW190814-type events. In that case, future observations should discover mergers between stellar mass and low mass gap black holes, with the lower mass spanning the entire low mass gap range.

The detection of ultra-high-energy (UHE, $\ge 10\mathrm{PeV}$) neutrinos via detectors designed to utilize the Askaryan effect has been a long-time goal of the astroparticle physics community. The Askaryan effect describes radio-frequency radiation from high-energy cascades. When a UHE neutrino initiates a cascade, cascade properties are imprinted on the radiation. Thus, observed radiation properties must be used to reconstruct the UHE neutrino event. Analytic Askaryan models have three advantages when used for UHE neutrino reconstruction. First, cascade properties may be derived from the match between analytic function and observed data. Second, analytic models minimize computational intensity in simulation packages. Third, analytic models can be embedded in firmware to enhance the real-time sensitivity of detectors. We present a fully analytic Askaryan model in the time domain for UHE neutrino-induced cascades in dense media that builds upon prior models in the genre. We then show that our model matches semianalytic parametrizations used in Monte Carlo simulations for the design of IceCube-Gen2. We find correlation coefficients greater than 0.95 and fractional power differences $<5\%$ between the fully analytic and semianalytic approaches.

It has been suggested that there is possibly a class of stellar-mass black holes (BHs) residing near (distance $\le {10}^{3}M$) the galactic center massive black hole, Sgr A*. Possible formation scenarios include the mass segregation of massive stellar-mass black holes and/or the disk migration if there was an active accretion flow near Sgr A* within $\mathcal{O}(10)\mathrm{Myr}$. In this work, we explore the application of this type of objects as sources of space-borne gravitational wave detectors, such as Laser Interferometer Space Antenna (LISA). We find it is possible to probe the spin of Sgr A* based on the precession of the orbital planes of these stellar-mass black holes moving around Sgr A*. We also show that the dynamical friction produced by accumulated cold dark matter near Sgr A* generally produces small measurable phase shift in the gravitational waveform. In the case that there is an axion cloud near Sgr A*, the dynamical friction induced modification to gravitational waveform is measurable only if the mass of the axion field is in a narrow range of the mass spectrum. Gravitational interaction between the axion cloud and the stellar-mass black holes may introduce additional precession around the spin of Sgr A*. This additional precession rate is generally weaker than the spin-induced Lense-Thirring precession rate, but nevertheless may contaminate the spin measurement in a certain parameter regime. At last, we point out that the multibody gravitational interaction between these stellar-mass black holes generally causes negligible phase shift during the LISA lifetime.

Squeezed vacuum states are now employed in gravitational-wave interferometric detectors, enhancing their sensitivity and thus enabling richer astrophysical observations. In future observing runs, the detectors will incorporate a filter cavity to suppress quantum radiation pressure noise using frequency-dependent squeezing. Interferometers employing internal and external cavities decohere and degrade squeezing in complex new ways, which must be studied to achieve increasingly ambitious noise goals. This paper introduces an audio diagnostic field (ADF) to quickly and accurately characterize the frequency-dependent response and the transient perturbations of resonant optical systems to squeezed states. This analysis enables audio field injections to become a powerful tool to witness and optimize interactions such as intercavity mode matching within gravitational-wave instruments. To demonstrate, we present experimental results from using the audio field to characterize a 16-m prototype filter cavity.