First-principles lattice determinations of the Standard Model expectation for the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon have become sufficiently precise that further improvement requires including strong and electromagnetic isospin-breaking effects. We provide a continuum estimate of the strong-isospin-breaking contribution, $a_{\mu }^{\mathrm{SIB}}$, using $SU(3)$ chiral perturbation theory. The result is shown to be dominated by resonance-region contributions encoded in a single low-energy constant whose value is known from flavor-breaking hadronic $\tau$ decay sum rules. Implications of the form of the result for lattice determinations of $a_{\mu }^{\mathrm{SIB}}$ are also discussed.

Using on-shell amplitude methods, we explore four-dimensional electric-magnetic duality and its double copy. We show explicitly that the on-shell scattering amplitudes know about “dual” photons (and dual gravitons), that the off-shell photon propagator double-copies to the graviton propagator, and that the magnetic part of the propagator is essential for the double copy to hold. We also show that there is an equivalent gravitomagnetic part of the graviton propagator, which is essential in giving rise to solutions with either angular momentum or NUT charge. Furthermore, we comment on the so-called Weinberg paradox, which states that scattering amplitudes involving the mixing of electric and magnetic monopoles cannot be Lorentz invariant, and would seem to preclude the existence of the ’t Hooft–Polyakov (topological) monopole. We trace this paradox to the magnetic part of the propagator, showing that it can be eliminated if one restricts the scenario to proper orthochronous Lorentz transformations. Finally, we compute the fully relativistic cross section for arbitrary spin dyons using the recently formulated on-shell duality transformation, and we show that this is always fully Lorentz invariant.

A new family of coherent states for all dimensional loop quantum gravity is proposed, which is based on the generalized twisted geometry parametrization of the phase space of $SO(D+1)$ connection theory. We prove that this family of coherent states provides an overcomplete basis of the Hilbert space in which edge simplicity constraint is solved. Moreover, according to our explicit calculation, the expectation values of holonomy and flux operators with respect to this family of coherent states coincide with the corresponding classical values given by the labels of the coherent states, up to some gauge degrees of freedom. Besides, we study the peakedness properties of this family of coherent states, including the peakedness of the wave functions of this family of coherent states in holonomy, momentum, and phase space representations. It turns out that the peakedness in these various representations and the (relative) uncertainty of the expectation values of the operators are well controlled by the semiclassical parameter $t$. Therefore, this family of coherent states can serve as a candidate for the semiclassical analysis of all dimensional loop quantum gravity.

Using the nonperturbative functional renormalization group (FRG) within the Blaizot-Méndez-Galain-Wschebor approximation, we compute the operator product expansion (OPE) coefficient $c_{112}$ associated with the operators ${\mathcal{O}}_1\sim \phi$ and ${\mathcal{O}}_2\sim {\phi }^2$ in the three-dimensional $\mathrm{O}(N)$ universality class and in the Ising universality class ($N=1$) in dimensions $2\le d\le 4$. When available, exact results and estimates from the conformal bootstrap and Monte Carlo simulations compare extremely well to our results, while the FRG is able to provide values across the whole range of $d$ and $N$ considered.

In this paper, we study thermodynamics and phase structure of asymptotically AdS hairy and Reissner-Nordström-AdS (RNAdS) black holes in the extended phase space, where the cosmological constant is interpreted as a thermal pressure. The RNAdS and hairy black holes are black hole solutions of an Einstein-Maxwell-scalar (EMS) model with a nonminimal coupling between the scalar and electromagnetic fields. The Smarr relation, the first law of thermodynamics and the free energy are derived for black hole solutions in the EMS model. Moreover, the phase structure of the RNAdS and hairy black holes is investigated in canonical and grand canonical ensembles. Interestingly, RNAdS BH/hairy BH/RNAdS BH reentrant phase transitions, consisting of zeroth-order and second-order phase transitions, are found in both ensembles.

We construct supersymmetric, asymptotically ${\mathrm{AdS}}_5$ gravitational soliton solutions of five-dimensional gauged supergravity coupled to arbitrarily many vector multiplets. These generalize the supersymmetric solitons of $U(1{)}^3$ gauged supergravity previously obtained by Chong, Cvetic, Lu, and Pope as limits of local, nonsupersymmetric metrics. We show that the soliton spacetimes contain evanescent ergosurfaces and argue that, as a result, these solitons should be nonlinearly unstable.

Boson stars have attracted much attention in recent decades as simple, self-consistent models of compact objects and also as self-gravitating structures formed in some dark-matter scenarios. Direct detection of these hypothetical objects through electromagnetic signatures would be unlikely because their bosonic constituents are not expected to interact significantly with ordinary matter and radiation. However, binary boson stars might form and coalesce emitting a detectable gravitational wave signal, which might distinguish them from ordinary compact object binaries containing black holes and neutron stars. We study the merger of two boson stars by numerically evolving the fully relativistic Einstein-Klein-Gordon equations for a complex scalar field with a solitonic potential that generates very compact boson stars. Owing to the steep mass-radius diagram, we can study the dynamics and gravitational radiation from unequal-mass binary boson stars with mass ratios up to $q\approx 23$ without the difficulties encountered when evolving binary black holes with large mass ratios. Similar to the previously studied equal-mass case, our numerical evolutions of the merger produce either a nonspinning boson star or a spinning black hole, depending on the initial masses and on the binary angular momentum. We do not find any evidence of synchronized scalar clouds forming around either the remnant spinning black hole or around the remnant boson stars. Interestingly, in contrast to the equal-mass case, one of the mechanisms to dissipate angular momentum is now asymmetric and leads to large kick velocities (up to a few ${10}^4\mathrm{km}/\mathrm{s}$), which could produce wandering remnant boson stars. We also compare the gravitational wave signals predicted from boson star binaries with those from black hole binaries and comment on the detectability of the differences with ground interferometers.

We study a generalization of the Holst action where we admit nonmetricity and torsion in manifolds with timelike boundaries (both in the metric and tetrad formalism). We prove that its space of solutions is equal to the one of the Palatini action. Therefore, we conclude that the metric sector is in fact identical to general relativity (GR), which is defined by the Einstein-Hilbert action. We further prove that, despite defining the same space of solutions, the Palatini and (the generalized) Holst Lagrangians are not cohomologically equal. Thus, the presymplectic structure and charges provided by the covariant phase space method might differ. However, using the relative bicomplex framework, we show the covariant phase spaces of both theories are equivalent (and in fact equivalent to GR), as well as their charges, clarifying some open problems regarding dual charges and their equivalence in different formulations.

Based on carefully selected physical requirements, we develop and analyze a rotating regular black hole with asymptotically Minkowski core. This Kerr-like geometry possesses the full “Killing tower” of nontrivial Killing tensor, Killing-Yano tensor, and principal tensor. The Hamilton-Jacobi equation, Klein-Gordon equation, and Maxwell’s equations are separable. Energy-condition violating physics is pushed into an arbitrarily small region in the deep core. Extraction of astrophysical observables falsifiable/verifiable by the observational community is straightforward.

It is a long-standing open question if a gravitomagnetic charge, the gravitational analogon to a hypothetical magnetic charge in electrodynamics, exists in nature. It naturally occurs in certain exact solutions to Einstein’s electrovacuum-field equations with cosmological constant. The charged NUT–de Sitter metric is such a solution. It describes a black hole with electric and gravitomagnetic charges and a cosmological constant. In this paper we will address the question how we can observe the gravitomagnetic charge using gravitational lensing. For this purpose we first solve the equations of motion for lightlike geodesics using Legendre’s canonical forms of the elliptic integrals and Jacobi’s elliptic functions. We fix a stationary observer in the domain of outer communication and introduce an orthonormal tetrad. The orthonormal tetrad relates the direction under which the observer detects a light ray to its latitude-longitude coordinates on the observer’s celestial sphere. In this parametrization we rederive the angular radius of the shadow, formulate a lens map, discuss the redshift, and the travel time. We also discuss relevant differences with respect to spherically symmetric and static spacetimes and how we can use them to determine if an astrophysical black hole has a gravitomagnetic charge.

Gravitational waveforms from coalescences of binary black hole and binary neutron star systems with low tidal effects can hardly be distinguished if the two systems have similar masses. In the absence of discriminating power based on the gravitational waveforms, the classification of sources into binary neutron stars, binary black holes and mixed systems can only be unambiguous when assuming the standard model of stellar evolution and using the fact that there exists a mass gap between neutron stars and black holes. This approach is however limited by its own assumptions: for instance the 2.6 solar mass object detected in the GW190814 event remains unclassified, and models of new physics can introduce new compact objects, like primordial black holes, which may have masses in the same range as neutron stars. In what follows, we investigate the possibility of discriminating between gravitational-wave signals emitted by different systems. First, we study the match between two waveforms, assuming several sensitivities of the detectors. In a second step, the ability of distinguishing one signal from the other is evaluated on simulations: a gravitational-wave signal is added to realistic noise from the LIGO-Virgo detectors, and the model best describing the simulated data is chosen based on the Bayes factor. The results depend strongly on the considered parameters, as the masses of the objects and tidal deformabilities of the neutrons stars. The task of distinguishing the nature of a compact object based on the gravitational-wave signal appears challenging for the current interferometers network. For instance, for a BNS system with tidal deformabilities $\mathrm{\Lambda }=600$ and chirp mass $1.44M_{\odot }$ and under optimistic assumptions, the nature of compact objects is correctly determined only for distances smaller that 150 Mpc, while it is unambiguously determined even for a distance of 300 Mpc in the case of third-generation detectors.

We investigate the predictions of inflation models with a nonminimal coupling to gravity for inflationary observables such as the spectral index and tensor-to-scalar ratio in a general setting. We argue that, depending on the relation between the Jordan frame potential and a function characterizing the nonminimal coupling, one can classify the model into three categories, each of which gives distinctive predictions for the inflationary observables. We derive general predictions for each class and also investigate some explicit models to discuss how the general features arise. Our results would be useful to design an inflation model consistent with observational constraints with a nonminimal coupling to gravity.

Long standing themes in inflation include the issue of large field vs. small field inflation as well as the question what fraction of phase space leads to sufficient inflation and furthermore is compatible with the experimental data. In the present paper, these issues are discussed in the context of modular inflation, a specialization of the framework of automorphic nonlinear $\sigma$ models associated to homogeneous spaces $G/K$ in which the continuous shift symmetry group $G$ is weakly broken to discrete subgroups $\mathrm{\Gamma }$. The target spaces of these theories inherit a curved structure from the group $G$, which in the case of modular invariant inflation leads to a hyperbolic field space geometry. It is shown that in this class of models the symmetry structure leads to both large and small field inflationary trajectories within a single modular inflation model. The present paper analyzes the concrete model of $j$-inflation, a hyperbolic model with nontrivial inflaton interactions. It describes in some detail the structure of the initial conditions, including a systematic analysis of several phenomenological functions on the target space, leading to constraints on the curvature scalar of the field space by upcoming experiments, as well as a discussion of the scaling behavior of the spectral index, the finite volume fraction of the field space leading to sufficient inflation, the attractor behavior of $j$-inflation, and a comparison of inflaton trajectories vs. target space geodesics. The tensor-ratio analysis shows that $j$-inflation is an interesting target for upcoming ground and satellite experiments.

Cosmic filaments are the largest collapsing structure in the Universe. Recently both observations and simulations inferred that cosmic filaments have coherent angular momenta (spins). Here we use filament finders to identify the filamentary structures in cosmological simulations and study their physical origins, which are well described by the primordial tidal torque of their Lagrangian counterpart regions—protofilaments. This initial angular momenta statistically preserve their directions to low redshifts. We further show that a spin reconstruction method can predict the spins of filaments and potentially relate their spins to the initial conditions of the Universe. This correlation provides a new way of constraining and obtaining additional information of the initial perturbations of the Universe.

Inspirals of an intermediate mass black hole (IMBH) and a solar mass type object will be observable by space based gravitational wave detectors such as the Laser Interferometer Space Antenna. A dark matter overdensity around an IMBH—a dark matter spike—can affect the orbital evolution of the system. We consider here such intermediate mass ratio inspirals on eccentric orbits, experiencing dynamical friction of the dark matter spike. We find that by including the relative velocities of the dark matter particles, the dynamical friction tends to circularize the orbit, in contrast to previous inquiries. We derive a general condition for circularization or eccentrification for any given dissipative force. In addition to the dephasing, we suggest using the circularization rate as another probe of the dark matter spike. Observing these effects would be an indicator for the particle nature of dark matter.

Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe); hence, the cumulative signal from all past supernova (SN) events can create a diffuse flux peaked at energies of about 25 MeV. We improve upon the modeling of the ALPs flux by including a set of CC SN models with different progenitor masses, as well as the effects of failed CC SNe, which yield the formation of black holes instead of explosions. Relying on the coupling strength of ALPs to photons and the related Primakoff process, the diffuse SN ALP flux is converted into gamma rays while traversing the magnetic field of the Milky Way. The spatial morphology of this signal is expected to follow the shape of the Galactic magnetic field lines. We make use of this via a template-based analysis that utilizes 12 years of Fermi-LAT data in the energy range from 50 MeV to 500 GeV. In our benchmark case of the realization of astrophysical and cosmological parameters, we find an upper limit of $g_{a\gamma }\lesssim 3.76\times {10}^{-11}{\mathrm{GeV}}^{-1}$ at a 95% confidence level for $m_a\ll {10}^{-11}\mathrm{eV}$, while we find that systematic deviations from this benchmark scenario induce an uncertainty as large as about a factor of two. Our result slightly improves the CAST bound, while still being a factor of six (baseline scenario) weaker than the SN1987A gamma-ray burst limit.

We compute an effective potential between two fixed sources in light-front quantization of a quenched scalar Yukawa theory that models the interaction of complex scalar fields through the exchange of a neutral scalar. Despite the breaking of explicit rotational symmetry by the use of light-front coordinates, the effective potential is rotationally symmetric and matches the standard Yukawa potential for scalar exchange. The neutral scalar field is represented by a coherent state, which is obtained nonperturbatively as an eigenstate of our model Hamiltonian, with the eigenenergy determining the effective potential. The sources are represented by wave packets that are fixed with respect to ordinary time, but move in light-front coordinates. The theory is quenched, to remove pair-production processes that would otherwise cause the spectrum to be unbounded from below. For divergent contributions we consider both a simple momentum cutoff and a Pauli-Villars regularization, with the divergence absorbed by a renormalized mass for the sources.

We present a supersymmetric model where energy scales of a discrete $R$-symmetry breaking ($Z_{6R}$) and cosmic inflation are commonly attributed to the confinement scale of a hidden $Sp(2)$ strong dynamics. Apart from these, the supersymmetry-breaking scale, the Higgsino mass, and the right-handed neutrino masses are all shown to stem from the $Z_{6R}$ breaking scale inferred from cosmic microwave background observables. We will show that the model is characterized by the supersymmetry-breaking soft mass $m_{\mathrm{soft}}\simeq 100–1000\mathrm{TeV}$ and the reheating temperature $T_{\mathrm{rh}}\simeq {10}^9\mathrm{GeV}$. Then we discuss how these predictions of the model can be tested with the help of the spectrum of the gravitational wave induced by the short-lived cosmic string present during the reheating era.

We make a comprehensive investigation of the Lorentz invariance violation (LIV) effects that may occur in two-neutrino double-beta ($2\nu \beta \beta$) decay for all the experimentally interesting nuclei. We deduce the formulas for the LIV deviations and provide single and summed energy electron spectra and angular correlation between electrons with and without LIV contributions to be used for constraining the LIV coefficient ${\stackrel{\circ }{a}}_{\mathrm{of}}^{(3)}$. First, we confirm the shifting of the electron spectra to higher electron energies due to LIV for all nuclei. Next, we analyze other LIV signatures that can be used in LIV investigations. Thus, from the comparison of the electron and angular correlation spectra calculated with the inclusion of the LIV contributions, with their standard forms, information can be obtained about the strength versus observability of the LIV effects in the current experimental statistics. Then, we present the alternative method of constraining ${\stackrel{\circ }{a}}_{\mathrm{of}}^{(3)}$ from the measurement of the angular correlation coefficient and estimate the statistics that different double-beta decay experiments should reach to constrain the LIV coefficient at the level of the current beta decay experiments. We hope that our work will improve the theoretical support and further stimulate the search for LIV in double-beta decay.