We study the propagation of a massless scalar wave in de Sitter spacetime perturbed by an arbitrary central mass. By focusing on the late time limit, this probes the portion of the scalar signal traveling inside the null cone. Unlike in asymptotically flat spacetimes, the amplitude of the scalar field detected by an observer at timelike infinity does not decay back to zero but develops a spacetime constant shift—both at zeroth and at first order in the central mass $M$. This indicates that massless scalar field propagation in asymptotically de Sitter spacetimes exhibits both linear and nonlinear tail-induced memories. On the other hand, for sufficiently late retarded times, the monopole portion of the scalar signal measured at null infinity is found to be amplified relative to its timelike infinity counterpart, by its nonlinear interactions with the gravitation field at first order in $M$.

In this work, we construct a five-dimensional spherically symmetric, charged and asymptotically anti–de Sitter black hole with its singularity being pointlike and strictly localized on our brane. In addition, the induced brane geometry is described by a Reissner-Nordström-(A)dS line element. We perform a careful classification of the horizons, and demonstrate that all of them are exponentially localized close to the brane thus exhibiting a pancake shape. The bulk gravitational background is everywhere regular, and reduces to an ${\mathrm{AdS}}_5$ spacetime right outside the black hole event horizon. This geometry is supported by an anisotropic fluid with only two independent components, the energy density ${\rho }_E$ and tangential pressure $p_2$. All energy conditions are respected close to and on our brane, but a local violation takes place within the event horizon regime in the bulk. A tensor-vector-scalar field-theory model is built in an attempt to realize the necessary bulk matter, however, in order to do so, both gauge and scalar degrees of freedom need to turn phantomlike at the bulk boundary. The study of the junction conditions reveals that no additional matter needs to be introduced on the brane for its consistent embedding in the bulk geometry apart from its constant, positive tension. We finally compute the effective gravitational equations on the brane, and demonstrate that the Reissner-Nordström-(A)dS geometry on our brane is caused by the combined effect of the five-dimensional geometry and bulk matter with its charge being in fact a tidal charge.

The spectrum of oscillating compact objects can be considerably altered in alternative theories of gravity. In particular, it may be enriched by modes with no counterpart in general relativity, tied to the dynamics of additional degrees of freedom generically present in these theories. Detection of these modes, e.g., in the gravitational-wave signal from a binary compact object coalescence, could provide a powerful tool to probe the underlying theory of gravity. To access the potential of such a detection, it is crucial to understand the linear and nonlinear spectral features of dynamically formed, oscillating compact objects in alternative theories of gravity. As a step towards that goal, in this work we present a suite of $1+1$ numerical relativity simulations of neutron stars in scalar-tensor theories, we carefully analyze the spectrum of stellar pulsations, and we compare results with expectations from linear perturbation theory. This allows us to build intuition for the case of binary neutron star mergers. Additionally, the models investigated in this work are representatives of two broad classes, in which the scalar field couples either strongly or weakly with the fluid. The distinct phenomenology of the nonlinear dynamics that we identify for each class of models, may find counterparts also in other alternative theories of gravity.

The stochastic approach to calculating scalar correlation functions in de Sitter spacetime is extended beyond the overdamped “slow-roll” approximation. We show that with the correct noise term, it reproduces the exact asymptotic long-distance behavior of field correlators in free field theory, thereby demonstrating the viability of the technique. However, we also show that the naïve way of calculating the noise term by introducing a cutoff at the horizon does not give the correct answer unless the cutoff is chosen specifically to give the required result. We discuss the implications of this for interacting theories.

An accurate and precise measurement of the spins of individual merging black holes is required to understand their origin. While previous studies have indicated that most of the spin information comes from the inspiral part of the signal, the informative spin measurement of the heavy binary black hole system GW190521 suggests that the merger and ringdown can contribute significantly to the spin constraints for such massive systems. We perform a systematic study into the measurability of the spin parameters of individual heavy binary black hole mergers using a numerical relativity surrogate waveform model including the effects of both spin-induced precession and higher-order modes. We find that the spin measurements are driven by the merger and ringdown parts of the signal for GW190521-like systems, but the uncertainty in the measurement increases with the total mass of the system. We are able to place meaningful constraints on the spin parameters even for systems observed at moderate signal-to-noise ratios, but the measurability depends on the exact six-dimensional spin configuration of the system. Finally, we find that the azimuthal angle between the in-plane projections of the component spin vectors at a given reference frequency cannot be well-measured for most of our simulated configurations even for signals observed with high signal-to-noise ratios.

“Glitches”—transient noise artifacts in the data collected by gravitational wave interferometers like the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo—are an ever-present obstacle for the search and characterization of gravitational wave signals. With some having morphology similar to high-mass, high-mass ratio, and extreme-spin binary black hole events, they limit sensitivity to such sources. They can also act as a contaminant for all sources, requiring targeted mitigation before astrophysical inferences can be made. We propose a data-driven, parametric model for frequently encountered glitch types using probabilistic principal component analysis. As a noise analog of parametrized gravitational wave signal models, it can be easily incorporated into existing search and detector characterization techniques. We have implemented our approach with the open-source glitschen package. Using LIGO’s currently most problematic glitch types, the “blip” and “tomte,” we demonstrate that parametric models of modest dimension can be constructed and used for effective mitigation in both frequentist and Bayesian analyses.

With the increasing sensitivities of the gravitational wave (GW) detectors and more detectors joining the international network, the chances of detection of a stochastic GW background (SGWB) are progressively increasing. Different astrophysical and cosmological processes are likely to give rise to backgrounds with distinct spectral signatures and distributions on the sky. The observed background will therefore be a superposition of these components. Hence, one of the first questions that will come up after the first detection of a SGWB will likely be about identifying the dominant components and their distributions on the sky. Both these questions were addressed separately in the literature, namely, how to separate components of isotropic backgrounds and how to probe the anisotropy of a single component. Here, we address the question of how to separate distinct anisotropic backgrounds with (sufficiently) different spectral shapes. We first obtain the combined Fisher information matrix from folded data using an efficient analysis pipeline pystoch, which incorporates covariances between pixels and spectral indices. This is necessary for estimating the detection statistic and setting upper limits. However, based on a recent study, we ignore the pixel-to-pixel noise covariance that does not have a significant effect on the results at the present sensitivity levels of the detectors. We establish the validity of our formalism using injection studies. We show that the joint analysis accurately separates and estimates backgrounds with different spectral shapes and different sky distributions with no major bias. This does come at the cost of increased variance. Thus making the joint upper limits safer, though less strict than the individual analysis. We finally set joint upper limits on the multicomponent anisotropic background using Advanced LIGO data taken up to the first half of the third observing run.

We study negative modes around the Coleman–de Luccia bounce solution. The conditions for the appearance of an infinite number of negative modes do not coincide between Lagrangian and Hamiltonian formulations in the literature, and we discuss the origin of this difference in detail. We show how different choices of the variable for the fluctuation around the bounce solution affect the negative mode condition in the Hamiltonian approach, and point out that there exists a choice that gives the same negative mode condition as the Lagrangian approach.

We carry out a detailed study of the confinement phase transition in a dark sector with an $SU(N)$ gauge group and a single generation of a dark heavy quark. We focus on heavy enough quarks such that their abundance freezes out before the phase transition, and the phase transition is of first order. We find that during this phase transition, the quarks are trapped inside contracting pockets of the deconfined phase and are compressed enough to interact at a significant rate, giving rise to a second stage of annihilation that can dramatically change the resulting dark matter abundance. As a result, the dark matter can be heavier than the often-quoted unitarity bound of $\sim 100\mathrm{TeV}$. Our findings are almost completely independent of the details of the portal between the dark sector and the Standard Model. We comment briefly on possible signals of such a sector. Our main findings are summarized in a companion paper, while here we provide further details on different parts of the calculation.

General-purpose Markov chain Monte Carlo sampling algorithms suffer from a dramatic reduction in efficiency as the system being studied is driven toward a critical point through, for example, taking the continuum limit. Recently, a series of seminal studies suggested that normalizing flows—a class of deep generative models—can form the basis of a sampling strategy that does not suffer from this “critical slowing down.” The central idea is to use machine learning techniques to build (approximate) trivializing maps, i.e., field transformations that map the theory of interest into a “simpler” theory in which the degrees of freedom decouple. These trivializing maps provide a representation of the theory in which all its nontrivial aspects are encoded within an invertible transformation to a set of field variables whose statistical weight in the path integral is given by a distribution from which sampling is easy. No separate process is required to generate training data for such models, and convergence to the desired distribution is guaranteed through a reweighting procedure such as a Metropolis test. From a theoretical perspective, this approach has the potential to become more efficient than traditional sampling since the statistical efficiency of the sampling algorithm is decoupled from the correlation length of the system. The caveat to all of this is that, somehow, the costs associated with the highly nontrivial task of sampling from the path integral of an interacting field theory are transferred to the training of a model to perform this transformation. In a proof-of-principle demonstration on two-dimensional ${\varphi }^4$ theory, Albergo, Kanwar, and Shanahan [Phys. Rev. D 100, 034515 (2019)] modeled the trivializing map as a sequence of pointwise affine transformations. We pick up this thread, with the aim of quantifying how well we can expect this approach to scale as we increase the number of degrees of freedom in the system. We make several modifications to the original design that allow our models to learn more efficient representations of trivializing maps using much smaller neural networks, which leads to a large reduction in the computational cost required to train models of equivalent quality. After making these changes, we find that sampling efficiency is almost entirely dictated by how extensively a model has been trained while being unresponsive to further alterations that increase model flexibility. However, as we move toward the continuum limit the training costs scale extremely quickly, which urgently requires further work to fully understand and mitigate.

The transfer-matrix of the U(1) lattice gauge theory is investigated in the field Fourier space, the basis of which consists of the quantized currents on lattice links. Based on a lattice version of the current conservation, the transfer-matrix elements are shown to be nonzero only between current states that differ in circulating currents inside plaquettes. In the strong coupling limit, a series expansion is developed for the elements of the transfer matrix, to which a diagrammatic representation based on the occurrence of virtual link and loop currents can be associated. With $g$ as the coupling, the weight of each virtual current in the expansion is $1/g^2$, by which at any given order the relevant diagrams are determined. Either by interpretation or through their role in fixing the relevant terms, the diagrams are reminiscent of the Feynman ones of the perturbative small coupling expansions.

The large data sample of the $B_c$ meson collected at the LHC experiment and the HL-LHC experiment provides us the opportunity to study the $B_c$ decays and the related physics. In this paper, we investigate the effect of $K^0-{\overline{K}}^0$ mixing on the branching ratios, $CP$ violations and $CPT$ violations in the $B_c^{\pm }\to B^{\pm }{K}_{S,L}^0$ decays. We find that some of the $B_c^{\pm }\to B^{\pm }{K}_{S,L}^0\to f_{B^{\pm }}{f}_{K_{S,L}^0}$ decay chains have large branching ratios, whose maximum value can exceed the order of ${10}^{-6}$, the minimum number of $B_c^{\pm }$ events times efficiency for observing the decays at three standard deviations ($3\sigma$) level is about ${10}^6$. We study the $CP$ asymmetries in the $B_c^{\pm }\to B^{\pm }{K}_{S,L}^0$ decays and find that the $CP$ asymmetries can exceed the order of ${10}^{-3}$, which are dominated by $K^0-{\overline{K}}^0$ mixing. We give the most promising processes to observe the $CP$ violations and the ranges of the numbers of $B_c^{\pm }$ events-times-efficiency needed to observe the $CP$ asymmetries at a significance of $3\sigma$ in these decays. We investigate the possibility to constraint the $CPT$ violation parameter $z$ in the $B_c^{\pm }\to B^{\pm }{K}_{S,L}^0\to f_{B^{\pm }}{f}_{K_{S,L}^0}$ decays and give the most promising processes to constraint the parameter $z$.

The decays $K^{*}(892)\to K_{S,L}^0\pi$ can be used to study $CP$ violation and $CPT$ violation. The $K^{*}(892)$ (hereinafter referred to as $K^{*}$) meson can be produced via $J/\psi$ decays at BESIII. In this paper, we study $CP$ violation and $K_S^0-K_L^0$ asymmetry in the $J/\psi$ decays involving the $K^{*}$ meson in the final states and obtain the following results: ${\mathcal{A}}_{CP}(J/\psi \to K^{*}{f}_{J/\psi }\to K_S^0\pi f_{J/\psi })=(3.64\pm 0.04)\times {10}^{-3}$, ${\mathcal{A}}_{CP}(J/\psi \to K^{*}{f}_{J/\psi }\to K_L^0\pi f_{J/\psi })=(-3.32\pm 0.04)\times {10}^{-3}$, and $R(J/\psi \to K^{*}{f}_{J/\psi }\to K_{S,L}^0\pi f_{J/\psi })=(3.51\pm 0.03)\times {10}^{-3}$, $R(J/\psi \to {\overline{K}}^{*}{\overline{f}}_{J/\psi }\to K_{S,L}^0\pi {\overline{f}}_{J/\psi })=(-3.45\pm 0.03)\times {10}^{-3}$. Based on two cases, the samples of ${10}^{10}$ and ${10}^{12}J/\psi$ events, we calculate the expected numbers of the observed signal events on the $CP$ violation and the $K_S^0-K_L^0$ asymmetry in the $J/\psi$ decays with $K^{*}$ meson in the final states, and we find that the BESIII experiment may be able to unambiguously observe $CP$ violation and $K_S^0-K_L^0$ asymmetry for each of these two cases. We study the possibility to constrain the $CPT$ violation parameter $z$ and discuss the sensitivity for the measurement of $z$ in $J/\psi$ decays with $K^{*}$ meson in the final states at BESIII. The sensitivity of the measurement of $z$ depends on the measured precision of the parameters $m_L-m_S$, ${\mathrm{\Gamma }}_L$, ${\mathrm{\Gamma }}_S$, $p$, and $q$ and the consistence between the values of $t_0$ and $t_1$ and the event selection criteria in experiment.

We show that new physics explanations of the muon $g-2$ anomaly by the contributions of new leptons mediated by the standard model Higgs boson necessarily lead to large rates for ${\mu }^{+}{\mu }^{-}\to hh$ and ${\mu }^{+}{\mu }^{-}\to hhh$ irrespectively of details of the model or the scale of new physics. For new leptons with the same quantum numbers as the standard model leptons, cross sections are expected to be about 240 ab for ${\mu }^{+}{\mu }^{-}\to hh$ independently of the center of mass energy, $\sqrt{s}$, and about 2.7 ab for ${\mu }^{+}{\mu }^{-}\to hhh$ for $\sqrt{s}=1\mathrm{TeV}$ and growing quadratically with $\sqrt{s}$. Predictions for models featuring new leptons with different quantum numbers and for a type-II two Higgs doublet model, where additional Higgs bosons can contribute to muon $g-2$, are also presented.

In this erratum we fix a bug in the generation of initial conditions for the simulations presented in our paper “Luminosity distance and anisotropic sky sampling at low redshifts: A numerical relativity study.” Our new simulations have overall smaller typical density contrasts, and therefore the amplitude of anisotropic effects found has reduced. However, qualitatively our results are unchanged.

A problematic feature of low-energy-scale inflationary models, such as Starobinsky inflation, in a spatially closed universe is the occurrence of a recollapse and a big crunch singularity before inflation can even set in. In a recent work, it was shown that this problem can be successfully resolved in loop quantum cosmology for a large class of initial conditions due to a nonsingular cyclic evolution and a hysteresislike phenomenon. However, for certain highly unfavorable initial conditions, the onset of inflation was still difficult to obtain. In this work, we explore the role of dissipative particle production, which is typical in warm inflation scenario, in the above setting. We find that entropy production sourced by such dissipative effects makes hysteresislike phenomena stronger. As a result, the onset of inflation is quick in general, including for highly unfavorable initial conditions where it fails or is significantly delayed in the absence of dissipative effects. We phenomenologically consider three warm inflation scenarios with distinct forms of dissipation coefficient and from dynamical solutions and phase-space portraits find that the phase space of favorable initial conditions turns out to be much larger than in cold inflation.

The Abelian Chern-Simons theory is considered on a cylindrical spacetime $\mathbb{R}\times D$, in a not necessarily flat Lorentzian background. As in the flat bulk case with planar boundary, we find that also on the radial boundary of a curved background a Kaç-Moody algebra exists, with the same central charge as in the flat case, which henceforth depends neither on the bulk metric nor on the geometry of the boundary. The holographically induced theory on the 2D boundary is topologically protected, in the sense that it describes a Luttinger liquid, no matter which the bulk metric is. The main result of this paper is that a remnant of the 3D bulk theory resides in the chiral velocity of the edge modes, which is not a constant like in the flat bulk case, but it is local, depending on the determinant of the induced metric on the boundary. This result may provide a theoretical framework for the recently observed accelerated chiral bosons on the edge of some Hall systems.

We present an improved formulation of 4-dimensional Lorentzian spinfoam quantum gravity with a cosmological constant. The construction of spinfoam amplitudes uses the state-integral model of $\mathrm{PSL}(2,\mathbb{C})$ Chern-Simons theory and the implementation of a simplicity constraint. The formulation has two key features: (1) spinfoam amplitudes are all finite, and (2) with suitable boundary data, the semiclassical asymptotics of the vertex amplitude has two oscillatory terms, with phase plus or minus the 4-dimensional Lorentzian Regge action with a cosmological constant for the constant curvature 4-simplex.