The spinning-hairy black holes that occur in Einstein’s gravity, supplemented by a doublet of complex scalar fields, are constructed within an extension of the model by a U(1) gauge symmetry involving a massless vector potential. The hairy black holes then acquire an electric charge and a magnetic moment; their domain of existence is discussed in terms of the gauge coupling constant.

We show that, in contrast to general relativity, in Eddington-inspired Born-Infeld gravity (EiBI), a violation of the null convergence condition does not necessarily lead to a violation of the null energy condition, by establishing a relationship between them. This serves as a motivation for finding wormhole solutions which can be supported by nonexotic matter in this gravity theory. We then obtain exact solutions of the field equations in EiBI gravity coupled to arbitrary nonlinear electrodynamics and anisotropic fluids. Depending on the signs and values of different parameters, the general solutions can represent both black holes and wormholes. In this work, we analyze the wormhole solutions. These wormholes are supported by nonexotic matter, i.e., matter satisfying all the energy conditions. As special cases of our general solutions, we work out several specific examples by considering Maxwell, power-law, Born-Infeld electrodynamics models and a particular form of an anisotropic fluid.

Gravitational-wave (GW) memory effects are constant changes in the GW strain and its time integrals, which are closely connected to changes in the charges that characterize asymptotically flat spacetimes. The first GW memory effect discovered was a lasting change in the GW strain. It can occur when GWs or massless fields carry away 4-momentum from an isolated source. Subsequently, it was shown that fluxes of intrinsic angular momentum can generate a new type of memory effect called the spin memory, which is an enduring change in a portion of the time integral of the GW strain. In this paper, we note that there is another new type of memory effect. We call it the “center-of-mass (CM) memory effect,” because it is related to changes in the CM part of the angular momentum of a spacetime. We first examine a few properties of the CM angular momentum. Specifically, we describe how it transforms under the supertranslation symmetry transformations of the Bondi-Metzner-Sachs group, and we compute a new expression for the flux of CM angular momentum carried by GWs in terms of a set of radiative multipole moments of the GW strain. We then turn to the CM memory effect. The CM memory effect appears in a quantity which has the units of the time integral of the GW strain. We define the effect in asymptotically flat spacetimes that start in a stationary state, radiate, and settle to a different stationary state. We show that it is invariant under infinitesimal supertranslation symmetries in this context. To determine the magnitude of the flux of CM angular momentum and the CM memory effect, we compute these quantities for nonspinning, quasicircular compact binaries in the post-Newtonian approximation. The CM memory effect arises from terms in the gravitational waveform for such binaries beginning at third and fourth post-Newtonian order for unequal- and equal-mass binaries, respectively. Finally, we estimate the amplitude of the CM memory effect for these binaries. We anticipate that it will be unlikely for current or upcoming GW detectors to measure the effect.

The nonlinear gravitational-wave memory effect is a prediction of general relativity in which test masses are permanently displaced by gravitational radiation. We implement a method for calculating the expected memory waveform from an oscillatory gravitational-wave time series. We use this method to explore the phenomenology of gravitational-wave memory using a numerical relativity surrogate model. Previous methods of calculating the memory have considered only the dominant oscillatory ($\ell =2$, $m=|2|$) mode in the spherical harmonic decomposition or the post-Newtonian expansion. We explore the contribution of higher-order modes and reveal a richer phenomenology than is apparent with $\ell =|m|=2$ modes alone. We also consider the “memory of the memory” in which the memory is, itself, a source of memory, which leads to a small, $O({10}^{-4})$, correction to the memory waveform. The method is implemented in the python package GWMemory, which is made publicly available.

In this work, we present the quasinormal modes of a fermionic field in the background of Gauss–Bonnet–AdS black holes. We find exact solutions for $D=5$ at the fixed value $\alpha =R^2/2$ of the Gauss-Bonnet coupling constant, with $R$ denoting the AdS radius, and we find numerical solutions for some range of values of the coupling constant $\alpha$ and $D=5$, 6. Mainly, we find two branches of quasinormal frequencies, a branch perturbative in the Gauss-Bonnet coupling constant $\alpha$ and another branch nonperturbative in $\alpha$. The phenomena of nonperturbative modes, which seem to be quite general in theories with higher curvature corrections, have been obtained in the spectrum of gravitational field perturbations and scalar field perturbations in previous works. We show that it also arises for fermionic field perturbations and therefore seems to be independent of the spin of the field under consideration. However, in contrast to gravitational and scalar field perturbations, where the nonperturbative modes are purely imaginary, we find that for fermionic field perturbations the nonperturbative modes acquire a real part. We find that the imaginary part of the quasinormal frequencies is always negative in both branches; therefore, the spherical Gauss–Bonnet–AdS black holes are stable against fermionic field perturbations.

We present an analytic study of cosmic superconducting chiral string collisions in Minkowski space, applying the kinematic constraints that arise from the relevant generalization of the Nambu-Goto action. In particular, we revisit the solution for chiral superconducting cosmic strings and demonstrate that Y junction production for such strings is possible. We consider the collision of chiral current-carrying straight strings and obtain the region in “angle-velocity” space that allows the production of string junctions. This study contributes to the understanding of the complex evolution of chiral superconducting string networks.

In this work, based on the worldline path integral representation of the vacuum energy in spacetime with a Lorentzian metric, we provide a new but complementary interpretation of the Unruh effect. We perform the quantization of the massless free scalar field in Rindler space, specifying initial and final conditions. After quantization, the final outcome for the vacuum energy is interpreted as world line path integrals. In this picture, we find that the Unruh radiation is made of real particles as well as real antiparticles. The prediction regarding the presence of antiparticles in the radiation might open new lines for the experimental detection of the effect. We present a thought experiment which offers a clear picture and supports the new interpretation.

Measurements of the $R_{D^{*}}\equiv \mathrm{Br}(B\to \tau \nu D^{*})/\mathrm{Br}(B\to e\nu D^{*})$ parameter remain in tension with the standard model prediction, despite recent results helping to close the gap. The standard model prediction it is compared with considers the $D^{*}$ as an external particle, even though what is detected in experiments is a $D\pi$ pair it decays into, from which it is reconstructed. We argue that the experimental result must be compared with the theoretical prediction considering the full four-body decay ($B\to l\nu D^{*}\to l\nu D\pi$). We show that the longitudinal degree of freedom of the off shell $D^{*}$ helps to further close the disagreement gap with experimental data. We find values for the ratio $R_{D\pi }^l\equiv \mathrm{Br}(B\to \tau {\nu }_{\tau }D\pi )/\mathrm{Br}(B\to l{\nu }_{l}D\pi )$ of $R_{D\pi }^e=0.274\pm 0.003$ and $R_{D\pi }^{\mu }=0.275\pm 0.003$, where the uncertainty comes from the uncertainty of the form factors parameters. Comparing against $R_{D\pi }$ reduces the gap with the latest LHCb result from $1.1\sigma$ to $0.48\sigma$, while the gap with the latest Belle result is reduced from $0.42\sigma$ to just $0.10\sigma$ and with the world average results from $3.7\sigma$ to $2.1\sigma$.

Very recently, a new ${\mathrm{\Omega }}^{*}$ state was reported by the Belle Collaboration, with its mass of $2012.4\pm 0.7(\text{stat})\pm 0.6(\text{syst})\mathrm{MeV}$, which locates just below the $K{\mathrm{\Xi }}^{*}$ threshold and hence hints to be a possible $K{\mathrm{\Xi }}^{*}$ hadronic molecule. Using the effective Lagrangian approach as the same as our previous works for other possible hadronic molecular states, we investigate the decay behavior of this new ${\mathrm{\Omega }}^{*}$ state within the hadronic molecular picture. The results show that the measured decay width can be reproduced well and its dominant decay channel is predicted to be the $K\pi \mathrm{\Xi }$ three-body decay. This suggests that the newly observed ${\mathrm{\Omega }}^{*}$ may be ascribed as the $J^P={3/2}^{-}K{\mathrm{\Xi }}^{*}$ hadronic molecular state and can be further checked through its $K\pi \mathrm{\Xi }$ decay channel.

In the next-to-minimal supersymmetric standard model (NMSSM), it is possible to have strong mass degeneracies between the new singletlike scalar and the heavy doubletlike scalar, as well as between the singletlike and doubletlike pseudoscalar Higgs states. When the difference in the masses of such states is comparable with the sum of their widths, the quantum mechanical interference between their propagators can become significant. We study these effects by taking into account the full Higgs boson propagator matrix in the calculation of the production process of ${\tau }^{+}{\tau }^{-}$ pairs in gluon fusion at the Large Hadron Collider (LHC). We find that, while these interference effects are sizeable, they are not resolvable in terms of the distributions of differential cross sections, owing to the poor detector resolution of the ${\tau }^{+}{\tau }^{-}$ invariant mass. They are, however, identifiable via the inclusive cross sections, which are subject to significant variations with respect to the standard approaches, wherein the propagating Higgs bosons are treated independently from one another. We quantify these effects for several representative benchmark points, extracted from a large set of points, obtained by numerical scanning of the NMSSM parameter space, that satisfy the most important experimental constraints currently available.

We determine the curvature of the pseudocritical line of $N_f=2+1$ QCD with physical quark masses via Taylor expansion in the quark chemical potentials. We adopt a discretization based on stout improved staggered fermions and the tree level Symanzik gauge action; the location of the pseudocritical temperature is based on chiral symmetry restoration. Simulations are performed on lattices with different temporal extent ($N_t=6$, 8, 10), leading to a continuum extrapolated curvature $\kappa =0.0145(25)$, which is in very good agreement with the continuum extrapolation obtained via analytic continuation and the same discretization, $\kappa =0.0135(20)$. This result eliminates the possible tension emerging when comparing analytic continuation with earlier results obtained via Taylor expansion.

Understanding hydrodynamization in microscopic models of heavy-ion collisions has been an important topic in current research. Many lessons obtained within the strongly coupled (holographic) models originate from the properties of transient excitations of equilibrium encapsulated by short-lived quasinormal modes of black holes. This paper aims to develop similar intuition for expanding plasma systems described by a simple model from the weakly coupled domain: the Boltzmann equation in the relaxation time approximation. We show that in this kinetic theory setup there are infinitely many transient modes carrying information about the initial distribution function. They all have the same exponential damping set by the relaxation time but are distinguished by different power-law suppressions and different frequencies of oscillations, logarithmic in proper time. Finally, we also analyze the resurgent interplay between the hydrodynamics and transients in this setup.

Double field theory is a manifestly T-duality invariant formulation of string theory in which the effective theory at any order of ${\alpha }^{\prime }$ is invariant under global $O(D,D)$ transformations and ought to be invariant under gauge transformations which receive ${\alpha }^{\prime }$-corrections. On the other hand, the effective theory in the usual $D$-dimensional formulation of string theory is manifestly gauge invariant and ought to be invariant under T-duality transformations which receive ${\alpha }^{\prime }$-corrections. We speculate that the combination of these two constraints may fix both the $2D$-dimensional and the $D$-dimensional effective actions without knowledge of the ${\alpha }^{\prime }$-corrections of the gauge and the T-duality transformations. In this paper, using generalized fluxes, we construct arbitrary $O(D,D)$-invariant actions at orders ${\alpha }^{\prime 0}$ and ${\alpha }^{\prime }$, and then dimensionally reduce them to the $D$-dimensional spacetime. On the other hand, at these orders, we construct arbitrary covariant $D$-dimensional actions. Constraining the two $D$-dimensional actions to be equal up to noncovariant field redefinitions, we find that both actions are fixed up to overall factors and up to field redefinitions.

We use gauge/string duality to model a doubly heavy diquark in a color antitriplet moving in a thermal plasma at temperatures near the critical. With the assumption that there is no relative motion between the constituents, we calculate the drag force on the diquark. At high enough speed we find that diquark string configurations develop a cusp. In addition, we estimate the spatial string tension at nonzero baryon chemical potential, and also briefly discuss an extension to a triply heavy triquark in a color triplet.

We study compactifications on Riemann surfaces with punctures of $\mathcal{N}=(1,0)$ six-dimensional SCFTs with a one-dimensional tensor branch and no continuous global symmetries. The effective description of such models on the tensor branch is in terms of pure gauge theories with decoupled tensor. For generic Riemann surfaces, the resulting theories in four dimensions are expected to have $\mathcal{N}=1$ supersymmetry. We compute the anomalies expected from the resulting four-dimemsional theories by integrating the anomaly polynomial of the six-dimensional theory on the Riemann surface. For the cases with six-dimensional gauge models with gauge groups $SU(3)$ and $SO(8)$, we further propose a field theory construction for the resulting four-dimensional theories. For the six-dimensional $SU(3)$ theory, we argue that the theories in four dimensions are quivers with $SU(3)$ gauge nodes and free chiral fields. The theories one obtains from the six-dimensional $SO(8)$ gauge theory are quivers with $SU(4)$ gauge groups and chiral fields with R charge a half. In the last case, the theories constructed for general Riemann surfaces involve gauging of symmetries appearing at strong coupling. The conformal manifolds of the models are constructed from gauge couplings and baryonic superpotentials. We support our conjectures by matching the dimensions of the conformal manifolds with complex structure moduli of the Riemann surfaces, matching anomalies between six and four dimensions, and checking the dualities related to different pairs of pants decompositions of the surfaces. As a simple application of the results, we conjecture that $SU(3)$ gauge theory with nine flavors in four dimensions has a duality group acting on the seven-dimensional conformal manifold which is the mapping class group of the sphere with ten marked points.

Using the volume of the space enclosed by the Ryu-Takayanagi (RT) surface, we study the complexity of the disk-shape subregion (with radius R) in various ($2+1$)-dimensional gapped systems with gravity dual. These systems include a class of toy models with singular IR and the bottom-up models for quantum chromodynamics and fractional quantum Hall effects. Two main results are: (i) in the large-R expansion of the complexity, the R-linear term is always absent, similar to the absence of topological entanglement entropy, and (ii) when the entanglement entropy exhibits the classic “swallowtail” phase transition, the complexity is sensitive but reacts differently.

Spin raising and lowering operators for massless field equations constructed from twistor spinors are considered. Solutions of the spin-$\frac{3}{2}$ massless Rarita-Schwinger equation from source-free Maxwell fields and twistor spinors are constructed. It is shown that this construction requires Ricci-flat backgrounds due to the gauge invariance of the massless Rarita-Schwinger equation. Constraints to construct spin raising and lowering operators for Rarita-Schwinger fields are found. Symmetry operators for Rarita-Schwinger fields via twistor spinors are obtained.

In this work we investigate an interesting connection between the absence of Newtonian singularities in the classical nonrelativistic potential and renormalizability properties in higher-derivative models of quantum gravity. In the framework of a large class of $D$-dimensional higher-derivative models of quantum gravity, we compute the nonrelativistic potential energy associated with two pointlike masses. Investigating its behavior for small distances, we find an algebraic condition which is sufficient for the cancellation of the Newtonian singularity. We verify that the same condition is necessary to ensure power-counting renormalizability and, as a consequence, we conclude that renormalizable higher-derivative models do not exhibit the so-called Newtonian singularity. Finally, we discuss the role of ghosts in the mechanism for the cancellation of Newtonian singularities.

In principle, gravitational waves could exist at any frequency. Recently, the LIGO-Virgo Collaboration detected gravitational waves (GWs) by probing their mechanical responses with laser interferometers. The detected GWs are in the intermediate-frequency band, i.e., GW150914: 35–250 Hz; GW151226: 35–450 Hz; GW170104: 30–350 Hz; GW170814: 35–450 Hz; and GW170817: 30–350 Hz. Alternatively, in this paper we investigate the observable electromagnetic responses (EMRs) of the GWs, passing through an alternating magnetic field. We show that, differing from the original Gertsenshtein-Zeldovich effect (which is the second-order effect of the amplitude of the GW passing through a high stationary magnetic field and consequently is too weak to be detected), the EMRs of the GWs in the present configuration are the first-order perturbation effects and thus the induced perturbation photon fluxes are detectable with the current well-developed weak-light detection techniques. Furthermore, we show that the wave impedances of the GW-induced electromagnetic wave perturbations are very different from those of the background electromagnetic noises (i.e., $\cong 377\mathrm{\Omega }$ for EM radiation in the background flat space-time). Therefore, with a properly designed wave-matching technique, the stronger background EM noise (without any GW information) can be effectively filtered out, and thus only the GW-induced perturbation photon fluxes are conducted to the detectors. The configuration proposed here could be utilized to actively look for GWs in a sufficiently wide frequency band, depending on the achievable scales of the required high magnetic fields. Hopefully, the proposal could provide a platform to detect GWs based on their electromagnetic response in higher frequency bands.

We analyze the collisional Penrose process of spinning test particles in an extreme Kerr black hole. We consider that two particles plunge into the black hole from infinity and collide near the black hole. For the collision of two massive particles, if the spins of particles are $s_1\approx 0.01379\mu M$ and $s_2\approx -0.2709\mu M$, we obtain the maximal efficiency is about ${\eta }_{\max }=(\text{extracted energy})/(\text{input energy})\approx 15.01$, which is more than twice as large as the case of the collision of non-spinning particles (${\eta }_{\max }\approx 6.32$). We also evaluate the collision of a massless particle without spin and a massive particle with spin (Compton scattering), in which we find the maximal efficiency is ${\eta }_{\max }\approx 26.85$ when $s_2\approx -0.2709\mu M$, which should be compared with ${\eta }_{\max }\approx 13.93$ for the nonspinning case.