Gravitational wave observations of compact binary coalescences provide precision probes of strong-field gravity. There is thus now a standard set of null tests of general relativity (GR) applied to LIGO-Virgo detections and many more such tests proposed. However, the relation between all these tests is not yet well understood. We start to investigate this by applying a set of standard tests to simulated observations of binary black holes in GR and with phenomenological deviations from GR. We consider four types of tests: residuals, inspiral-merger-ringdown consistency, parametrized phasing (two versions), and modified dispersion relation. We also check the consistency of the unmodeled reconstruction of the waveforms with the waveform recovered using GR templates. These tests are applied to simulated observations similar to GW150914 with both large and small deviations from GR and similar to GW170608 just with small deviations from GR. We find that while very large deviations from GR are picked up with high significance by almost all tests, more moderate deviations are picked up by only a few tests, and some deviations are not recognized as GR violations by any test at the moderate signal-to-noise ratios we consider. Moreover, the tests that identify various deviations with high significance are not necessarily the expected ones. In particular, the parametrized tests recover PN test parameters much closer to zero than their true values in some cases. Additionally, we find that of the GR deviations we consider, the residuals test is only able to detect extreme deviations from GR that no longer look like binary black hole coalescences in GR. The reconstruction comparison shows more promise for detecting relatively small GR deviations in an unmodeled framework, at least for high-mass systems.

An important physical phenomenon that manifests itself during the inspiral of two orbiting compact objects is the tidal deformation of each under the gravitational influence of its companion. In the case of binary neutron star mergers, this tidal deformation and the associated Love numbers have been used to probe properties of dense matter and the nuclear equation of state. Nonspinning black holes on the other hand have a vanishing (field) tidal Love number in general relativity. This pertains to the deformation of the asymptotic gravitational field. In certain cases, especially in the late stages of the inspiral phase when the black holes get close to each other, the source multipole moments might be more relevant in probing their properties and the no-hair conjecture; contrastingly, these Love numbers do not vanish. In this paper, we track the source multipole moments in simulations of several binary black hole mergers and calculate these Love numbers. We present evidence that, at least for modest mass ratios, the behavior of the source multipole moments is universal.

We present new results concerning the Proca massive vector field in a Schwarzschild-anti–de Sitter (Schwarzschild-AdS) black hole geometry. We provide a first principles analysis of Proca vector fields in this geometry using both the vector spherical harmonic (VSH) decomposition and separation method and the Frolov-Krtouš-Kubizňák-Santos (FKKS) method that separates the relevant equations in spinning geometries. The analysis in the VSH method shows, on one hand, that it is arduous to separate the scalar-type from the vector-type polarizations of the electric sector of the Proca field, and on the other hand, it displays clearly the electric and the magnetic mode sectors. The analysis in the FKKS method is performed by taking the nonrotating limit of the Kerr-AdS spacetime, and shows that the Ansatz decouples the polarizations in the electric mode sector even in the nonrotating limit. On the other hand, it captures only two of the three possible polarizations; indeed, the magnetic mode sector, which is of vector-type, is missing. The reason for the absence of the remaining polarization is related to the degeneracy of the principal tensor in static spherical symmetric spacetimes. The degrees of freedom and quasinormal modes in both separation methods of the Proca field are found. The frequencies of the quasinormal modes are also carefully computed. For the electric mode sector in the VSH method the frequencies are found through an extension, which substitutes number coefficients by matrix coefficients, of the Horowitz-Hubeny numerical procedure, whereas for the magnetic mode sector in the VSH method and the electric sector of the FKKS method it is shown that a direct use of the procedure can be made. The values of the quasinormal mode frequencies obtained for each method are compared and shown to be in good agreement with each other. This further supports the analytical approaches presented here for the behavior of the Proca field in a Schwarzschild-AdS black hole background.

We construct a Bayesian inference deep learning machine for parameter estimation of gravitational wave events of binaries of black hole coalescence. The structure of our deep Bayesian machine adopts the conditional variational autoencoder scheme by conditioning on both the gravitational wave strains and the variations of the amplitude spectral density (ASD) of the detector noise. We show that our deep Bayesian machine is capable of yielding posteriors compatible with the ones from the nested sampling method and better than the one without conditioning on the ASD. Our result implies that the process of parameter estimation can be accelerated significantly by deep learning even with large ASD drifting/variation. We also apply our deep Bayesian machine to the LIGO/Virgo O3 events, the result is compatible with the one by the traditional Bayesian inference method for the gravitational wave events with signal-to-noise ratios higher than typical threshold value. We use one GPU device, NVIDIA RTX3090, to train the deep learning machines, which takes about 12 hours. After training, it takes less than one second to generate the posterior of a gravitational wave event and is far faster than the conventional nested sampling method.

We present a systematic study of projection biases in the weak lensing analysis of the first year of data from the Dark Energy Survey (DES) experiment. In the analysis, we used a $\mathrm{\Lambda }\mathrm{CDM}$ model and three two-point correlation functions. We show that these biases are a consequence of projecting, or marginalizing, over parameters like $h$, ${\mathrm{\Omega }}_b$, $n_s$, and ${\mathrm{\Omega }}_{\nu }{h}^2$ that are both poorly constrained and correlated with the parameters of interest like ${\mathrm{\Omega }}_m$, ${\sigma }_8$, and $S_8$. Covering the relevant parameter space, we show that the projection biases are a function of where the true values of the poorly constrained parameters lie with respect to the parameter priors. For example, biases in the position of the posteriors can exceed the $1.5\sigma$ level if the true values of $h$ and $n_s$ are close to the top of the prior’s range, and the true values of ${\mathrm{\Omega }}_b$ and ${\mathrm{\Omega }}_{\nu }{h}^2$ are close to the bottom of the range of their priors. We also show that in some cases the 1D credible intervals can be overspecified by as much as 30% and coverage can be as low as 27%. Finally, we estimate these projection biases for the analysis of three and six years worth of DES data.

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct $f(\varphi )T$ term, where $\varphi$ is identified as the inflaton and $T$ is the trace of the energy-momentum tensor. The framework goes to Einstein gravity naturally when the inflaton decays out. We investigate inflation dynamics in this $f(\varphi )T$ gravity (not to be confused with torsion-scalar coupled theories) on a general basis and then apply it to three well-motivated inflationary models. We find that the predictions for the spectral tilt and the tensor-to-scalar ratio are sensitive to this new $f(\varphi )T$ term. This $f(\varphi )T$ gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.

We consider warm inflation in the context of holographic cosmology. The weak and the strong dissipative regime are analyzed in the slow-roll approximation and within what is known as intermediate inflation. For an appropriate choice of the equation of state, the intermediate inflation is not only an exact solution in general relativity, but it is also in the holographic setup considered in this paper. Within this approach several dissipative and physically relevant functions are considered. We constrain our model using the latest Planck data. We conclude that three of the models analyzed are consistent with Planck data for some ranges of the model parameters. However, one of them is ruled out by the observations.

We study the dynamics of magnetic fields in chiral magnetohydrodynamics, which takes into account the effects of an additional electric current related to the chiral magnetic effect in high-energy plasmas. We perform direct numerical simulations, considering weak seed magnetic fields and inhomogeneities of the chiral chemical potential ${\mu }_5$ with a zero mean. We demonstrate that a small-scale chiral dynamo can occur in such plasmas if fluctuations of ${\mu }_5$ are correlated on length scales that are much larger than the scale on which the dynamo growth rate reaches its maximum. Magnetic fluctuations grow by many orders of magnitude due to the small-scale chiral dynamo instability. Once the nonlinear backreaction of the generated magnetic field on fluctuations of ${\mu }_5$ sets in, the ratio of these scales decreases and the dynamo saturates. When magnetic fluctuations grow sufficiently to drive turbulence via the Lorentz force before reaching maximum field strength, an additional mean-field dynamo phase is identified. The mean magnetic field grows on a scale that is larger than the integral scale of turbulence after the amplification of the fluctuating component saturates. The growth rate of the mean magnetic field is caused by a magnetic $\alpha$ effect that is proportional to the current helicity. With the onset of turbulence, the power spectrum of ${\mu }_5$ develops a universal $k^{-1}$ scaling independently of its initial shape, while the magnetic energy spectrum approaches a $k^{-3}$ scaling.

We show the possibility to discover the neutrino nature by measuring the Majorana $CP$ phase at the DUNE experiment. This phase is turned on by a decoherence environment, possibly originated by physics at the Planck scale. A sizable distortion in the measurement of the Dirac $CP$ violation phase ${\delta }_{CP}$ is observed at DUNE when compared with T2HK measurement due to decoherence and the non-null Majorana phase. Being that, when the measurement of the Majorana phase is performed at DUNE, it reaches a precision of $23(21)\%$ for a decoherence parameter $\mathrm{\Gamma }=4.5(5.5)\times {10}^{-24}\mathrm{GeV}$ and a Majorana phase equal to $1.5\pi$. The latter precision is similar to the one obtained at the T2K experiment at its current Dirac $CP$ violation phase measurement.

Null results from searches for new physics at the Large Hadron Collider (LHC) tend to enforce the belief that new particles must be much heavier than the weak scale. We undertake a systematic study of the interplay between Higgs alignment and $CP$-violation in complex two-Higgs-doublet models, which enables us to construct a $CP$-violating scenario where new Higgs bosons are close to the weak scale after including stringent constraints from the electric dipole moment and measurements at the LHC. In addition, we propose a novel potential signal of $CP$-violation in the Higgs-to-Higgs decays, $h_3\to h_2{h}_1$, where $h_3$, $h_2$, and $h_1$ are the heaviest, second heaviest and the Standard Model-like neutral Higgs bosons, respectively. The decay could manifest itself in triple boson final states in $h_1{h}_1{h}_1$ and $h_1{h}_{1}Z$, which are quite distinct and provide unique venues for new measurements at the LHC.

We investigate the potential for discovering new physics through the low-energy scattering processes $e^{-}p\to e^{-}({\mu }^{-}){\mathrm{\Lambda }}_c$, which could be accessible in the forthcoming $ep$ scattering experiments once adapted to our proposed setups. In the framework of a general low-energy effective Lagrangian, we demonstrate that, compared with the conventional flavor-changing neutral-current weak decays of charmed hadrons and the dilepton productions at high-energy colliders, the low-energy scattering processes can provide more competitive potentials for hunting the underlying new physics. In some specific leptoquark models, we also show that promising event rates can be expected for both the scattering processes, and point out a possible way to distinguish the experimental signals due to the scalar leptoquarks from those of the vector ones.

In 2015, the PHENIX Collaboration has measured single-spin asymmetries for charged pions in transversely polarized $p+p$ collisions at the center-of-mass energy of $\sqrt{s}=200\mathrm{GeV}$. The pions were detected at central rapidities of $|\eta |<0.35$. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.

We argue for the quantum-gravitational inconsistency of certain 6D $\mathcal{N}=(1,0)$ supergravity theories, whose anomaly-free gauge algebra $\mathfrak{g}$ and hypermultiplet spectrum $M$ were observed by Raghuram et al. [J. High Energy Phys. 07 (2021) 048] to be realizable only as part of a larger gauge sector $({\mathfrak{g}}^{\prime }\supset \mathfrak{g},M^{\prime }\supset M)$ in F-theory. To detach any reference to a string theoretic method of construction, we utilize flavor symmetries to provide compelling reasons why the vast majority of such $(\mathfrak{g},M)$ theories are not compatible with quantum gravity constraints, and how the “automatic enhancement” to $({\mathfrak{g}}^{\prime },M^{\prime })$ remedies this. In the first class of models, with ${\mathfrak{g}}^{\prime }=\mathfrak{g}\oplus \mathfrak{h}$, we show that there exists an unbroken flavor symmetry $\mathfrak{h}$ acting on the matter $M$, which, if ungauged, would violate the no-global-symmetries hypothesis. This argument also applies to 1-form center symmetries, which govern the gauge group topology and massive states in representations different from those of massless states. In a second class, we find that $\mathfrak{g}$ is incompatible with the flavor symmetry of certain supersymmetric strings that must exist by the completeness hypothesis.

The background-field method is adopted for studying the dynamics of coherent states within an interacting scalar field theory. Focusing on a coherent state that corresponds to the homogeneous condensate, the quantum depletion of the expectation value of the field operator is demonstrated to be due to the annihilation of the condensate constituents into relativistic quanta. Moreover, due to the fact that the initial field acceleration and energy for the nonsqueezed coherent states are determined in terms of a bare coupling constant, instead of the renormalized one, the appearance of perturbative singularities is shown to be inevitable. In other words, consistency of these states requires the finiteness of the bare coupling constant, through the resummation.

Black hole spectroscopy is the proposal to observe multiple quasinormal modes in the ringdown of a binary black hole merger. In addition to the fundamental quadrupolar mode, overtones and higher harmonics may be present and detectable in the gravitational wave signal, allowing for tests of the no-hair theorem. We analyze in detail the strengths and weaknesses of the standard Rayleigh criterion supplied with a Fisher matrix error estimation, and we find that the criterion is useful, but too restrictive. Therefore, we motivate the use of a conservative high Bayes factor threshold to obtain the black hole spectroscopy horizons of current and future detectors; i.e., the distance (averaged in sky location and binary inclination) up to which one or more additional modes can be detected and confidently distinguished from each other. We set up all of our searches for additional modes starting at $t=10(M_1+M_2)$ after the peak amplitude in simulated signals of circular nonspinning binaries. An agnostic multimode analysis allows us to rank the subdominant modes: for nearly equal mass binaries, we find $(\ell ,m,n)=(2,2,1)$ and (3,3,0) and, for very asymmetric binaries, (3,3,0) and (4,4,0), for the secondary and tertiary modes, respectively. At the current estimated rates for heavy stellar mass binary black hole mergers, with primary masses between 45 and 100 solar masses, we expect an event rate of mergers within our conservative estimate for the (2,2,1) spectroscopy horizon of $0.03–0.10{\mathrm{yr}}^{-1}$ for LIGO at design sensitivity and $(0.6-2.4)\times {10}^3{\mathrm{yr}}^{-1}$ for the future third generation ground-based detector Cosmic Explorer.

It has been known for many years that the leading correction to the black hole entropy is a logarithmic term, which is universal and closely related to conformal anomaly. A fully consistent analysis of this issue has to take quantum backreactions to the black hole geometry into account. However, it was always unclear how to naturally derive the modified black hole metric, especially from an effective action, because the problem refers to the elusive nonlocality of quantum gravity. In this paper, we show that this problem can be resolved within an effective field theory (EFT) framework of quantum gravity. Our work suggests that the EFT approach provides a powerful and self-consistent tool for studying the quantum gravitational corrections to black hole geometries and thermodynamics.

The solar gravitational lens (SGL) offers unique capabilities for direct high-resolution imaging of faint, distant objects, such as exoplanets. For that purpose, in the near future, a spacecraft carrying a meter-class telescope with a solar coronagraph would be placed in the focal region of the SGL. That region begins at $\sim 547$ astronomical units from the Sun and occupies the immediate vicinity of the target-specific primary optical axis—the line that connects the center of the target and that of the Sun. Clearly, this axis is not at rest. It undergoes complex motion as the exoplanet orbits its host star, as that star moves with respect to the Sun, and even as the Sun itself moves with respect to the Solar System’s barycenter due to the gravitational pull of planets in our Solar System. Although less prominent, other motions exist. An image of an extended object is projected by the SGL into an image plane and moves within that plane, responding to the motion of the optical axis. To sample the image, a telescope must always be on the move, following the projection, with precise knowledge of its own position with respect to the image. We consider the dominant motions that determine the position of the focal line as a function of time. We evaluate the needed navigational capability for the telescope to conduct a multiyear exoplanet imaging mission in the focal region for the SGL. We show that even in a rather conservative case, when an Earth-like exoplanet is in our immediate stellar neighborhood at $\sim 10$ light years, the motion of the image is characterized by a small total acceleration that is driven primarily by the orbital motion of the exoplanet (its effect on the projected image estimated to be at the level of $\sim 6\mu {\mathrm{m}/\mathrm{s}}^2$, decreasing inversely with distance to a target) and by the reflex motion of our Sun (target independent, contributing at $\sim 0.2\mu {\mathrm{m}/\mathrm{s}}^2$). We discuss how the amplified light of the host star allows us to establish a local reference frame that significantly relaxes navigational requirements for the imaging operations. We conclude that the required navigation in the SGL’s focal region, although complex, can be accurately modeled, and a $\sim 10$-year prospective imaging mission is achievable with the already available propulsion technology.

We revisit a general minisuperspace (MSS) formalism for scalar tensor Friedmann-Lemaître-Robertson-Walker type cosmological models in an arbitrary frame with a perfect fluid source. We discuss how to impose Cauchy data on the corresponding dynamical system in order to reconstruct a standard ($\mathrm{\Lambda }\mathrm{CDM}$) cosmological model. So far, the integrability of such models has been extensively studied in the Einstein or Jordan frames mainly. We extend these studies to an arbitrary frame taking into account nonminimal coupling between matter and gravity. To this aim we explore a gauge freedom associated with a choice of lapse function. We show that particular isothermal MSS coordinates are related with Einstein frames representing solution equivalent classes and have some invariant meaning. This provides a new universal framework for investigating cosmic evolution in an arbitrary frame: analytical solutions obtained in the Einstein frame can be transformed back to the physical frame by making use of a conformal transformation and field redefinition. We also show how such a technique can be useful when applied to Wheeler-DeWitt quantum cosmology.

We consider a spatially flat Friedmann-Lemaître-Robertson-Walker background space with an ideal gas and a multifield Lagrangian consisting of two minimally coupled scalar fields which evolve in a field space of constant curvature. For this cosmological model we classify the potential function for the scalar fields such that variational point symmetries exist. The corresponding conservation laws are calculated. Finally, analytic solutions are presented for specific functional forms of the scalar field potential in which the cosmological field equations are characterized as a Liouville integrable system by point symmetries. The free parameters of the cosmological model are constrained in order to describe analytic solutions for an inflationary epoch. Finally, stability properties of exact closed-form solutions are investigated. These solutions are scaling solutions with important physical properties for the cosmological model.