We construct the Faddeev-Kulish asymptotic states in a quantum field theory of electric and magnetic charges. We find that there are two kind of dressings: apart from the well-known (electric) Wilson line dressing, there is a magnetic counterpart which can be written as a ’t Hooft line operator. The ’t Hooft line dressings are charged under the magnetic large gauge transformation (LGT), but are neutral under electric LGT. This is in contrast to the Faddeev-Kulish dressings of electrons, which can be written as a Wilson line operator and are charged under electric LGT but neutral under magnetic LGT. With these dressings and the corresponding construction of the coherent states, the infrared finiteness of the theory of electric and magnetic charges is guaranteed. Even in the absence of magnetic monopoles, the electric and magnetic soft modes exhibit the electromagnetic duality of vacuum Maxwell theory. Using only the asymptotic form of three-point interactions in a field theory of electric and magnetic charges, we show that the leading magnetic dressings, like the leading electric ones, are exact in the field theory of electric and magnetic charges, in accordance with a conjecture of Strominger. We then extend the construction to perturbative quantum gravity in asymptotically flat spacetime, and construct gravitational ’t Hooft line dressings that are charged under dual supertranslations. The duality in the quantum theory between the electric and magnetic soft charges and their dressings is thus made manifest.

We study the free motion of a massive particle moving in the background of a Finslerian deformation of a plane gravitational wave in Einstein’s general relativity. The deformation is a curved version of a one-parameter family of relativistic Finsler structures introduced by Bogoslovsky, which are invariant under a certain deformation of Cohen and Glashow’s very special relativity group $\mathrm{ISIM}(2)$. The partially broken Carroll symmetry we derive using Baldwin-Jeffery-Rosen coordinates allows us to integrate the geodesics equations. The transverse coordinates of timelike Finsler geodesics are identical to those of the underlying plane gravitational wave for any value of the Bogoslovsky-Finsler parameter $b$. We then replace the underlying plane gravitational wave with a homogeneous $pp$-wave solution of the Einstein-Maxwell equations. We conclude by extending the theory to the Finsler-Friedmann-Lemaître model.

In this study, we consider three dark energy models in which $\mathrm{\Lambda }$ is not constant, but has a dynamic nature that depends on the Hubble parameter $H$ and/or its time derivative $\dot{H}$. We analyze the generalized running vacuum model, for which $\mathrm{\Lambda }(H)=A+B{H}^2+C\dot{H}$, along with the two models obtained by setting $B$ or $C$ equal to zero. A null value for $C$ yields the classical running vacuum model (RVM), while $B=0$ corresponds to what we term the generalized running vacuum subcase, or GRVS. Our main aim is to investigate whether these models can accommodate nonzero spatial curvature. To this end, we carry out a Markov chain Monte Carlo analysis using data for the observables associated with type-Ia supernovae, cosmic chronometers, the cosmic microwave background, and baryon acoustic oscillations, as well as two values for the Hubble constant. Then we include data relating to the growth of large-scale structure (LSS) and repeat the procedure. Our results indicate that taking LSS observations into account helps to tighten constraints and determine a definite sign for the model parameters. In the case of the RVM and GRVS, the addition of growth data result in dynamical vacuum energy being preferred to a cosmological constant at a little over $1\sigma$. This happens in both the flat and nonflat scenarios—there are only a few exceptions—but comes at the cost of an extra parameter, which can degrade the performance of the models (as assessed by model selection criteria). Of special relevance is the fact that the inclusion of LSS data appear to increase compatibility with a flat geometry. It also brings the constraints on the Hubble constant closer to the range of values established by Planck.

The method of minimal geometric deformation (MGD) is used to derive static, strongly gravitating, spherically symmetric, compact stellar distributions that are solutions of the Yang-Mills-Einstein-Dirac coupled field equations on fluid membranes with finite tension. Their solutions characterize MGD Yang-Mills-Dirac stars, whose mass has order of the Chandrasekhar mass, once the range of both the fermionic self-interaction and the Yang-Mills coupling constants is suitably chosen. Physical features of MGD Yang-Mills-Dirac stars are then discussed and their Arnowitt-Deser-Misner masses are derived, as a function of the fermion coupling constant, the finite brane tension, and the Yang-Mills running parameter.

Unimodular gravity is an appealing approach to address the cosmological constant problem. In this scenario, the vacuum energy density of quantum fields does not gravitate and the cosmological constant appears merely as an integration constant. Recently, it has been shown that energy diffusion that may arise in quantum gravity and in theories with spontaneous collapse is compatible with this framework by virtue of its restricted diffeomorphism invariance. New studies suggest that this phenomenon could lead to higher-order equations in the context of homogeneous and isotropic Universe, affecting the well-posedness of their Cauchy initial-value problem. In this work, we show that this issue can be circumvented by assuming an equation of state that relates the energy density to the function that characterizes diffusion. As an application, we solve the field equations analytically for an isotropic and homogeneous universe in a barotropic model and in the mass-proportional continuous spontaneous localization (CSL) scenario, assuming that only dark matter develops energy diffusion. Different solutions possessing phase transition from decelerated to accelerated expansion are found. We use cosmological data of type Ia supernovae and observational Hubble data to constrain the free parameters of both models. It is found that very small but nontrivial energy nonconservation is compatible with the barotropic model. However, for the CSL model, we find that the best-fit values are not compatible with previous laboratory experiments. We comment on this fact and propose future directions to explore energy diffusion in cosmology.

Low mass x-ray binaries are prime targets for continuous gravitational wave searches by ground-based interferometers. Results are presented from a search for five low-mass x-ray binaries whose spin frequencies and orbital elements are measured accurately from x-ray pulsations: HETE J1900.1-2455, IGR $\mathrm{J}00291+5934$, SAX J1808.4-3658, XTE J0929-314, and XTE J1814-338. Data are analysed from Observing Run 2 of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). The search algorithm uses a hidden Markov model to track spin wandering, the $\mathcal{J}$-statistic maximum likelihood matched filter to track orbital phase, and a suite of five vetoes to reject artefacts from non-Gaussian noise. The search yields a number of low-significance, above threshold candidates consistent with the selected false-alarm probability. The candidates will be followed up in subsequent observing runs.

Dark matter particles from the galactic halo can be gravitationally trapped in the solar core or in external orbits. The enhanced density of dark matter particles either in the solar core or in external orbits can result in the annihilation of these particles producing gamma rays via long-lived intermediate states or directly outside the Sun, respectively. These processes would yield characteristic features in the energy spectrum of the subsequent gamma rays, i.e., a boxlike or linelike shaped feature, respectively. We have performed a dedicated analysis using a 10-year sample of gamma-ray events from the Sun collected by the Fermi Large Area Telescope searching for spectral features in the energy spectrum as a signature of dark matter annihilation. In the scenario of gamma-ray production via long-lived mediators, we have also evaluated the dark matter-nucleon spin-dependent and spin-independent scattering cross section constraints from the flux limits in a dark matter mass range from $3\mathrm{GeV}/{\mathrm{c}}^2$ up to about $1.8\mathrm{TeV}/{\mathrm{c}}^2$. In the mass range up to about $150\mathrm{GeV}/{\mathrm{c}}^2$, the limits are in the range ${10}^{-46}–{10}^{-45}{\mathrm{cm}}^2$ for the spin-dependent scattering and in the range ${10}^{-48}–{10}^{-47}{\mathrm{cm}}^2$ for the spin-independent case. The range of variation depends on the decay length of the mediator.

Motivated by developing a field-theoretic algebraic approach to the universal part of the stress-tensor sector of a scalar four-point function in a class of higher-dimensional conformal field theories (CFTs), we construct a mode operator, ${\mathcal{L}}_m$, near the lightcone in $d=4$ CFTs and show that it leads to a Virasoro-like commutator, including a regularized central-term. As an example, we describe how to reproduce the $d=4$ single-stress tensor exchange contribution in the lightcone limit by a mode summation. A general-$d$ extension is included. We comment on possible generalizations.

We present the first chiral-continuum–finite-volume extrapolation of the hyperon octet axial couplings ($g_{\mathrm{\Sigma }\mathrm{\Sigma }}$ and $g_{\mathrm{\Xi }\mathrm{\Xi }}$) from $N_f=2+1+1$ lattice QCD. These couplings are important parameters in the low-energy effective field theory description of the octet baryons and are fundamental to the nonleptonic decays of hyperons and to hyperon-hyperon and hyperon-nucleon scattering with applications to neutron stars. We use clover lattice fermion action for the valence quarks with sea quarks coming from configurations of $N_f=2+1+1$ highly improved staggered quarks generated by MILC Collaboration. Our work includes the first calculation of $g_{\mathrm{\Sigma }\mathrm{\Sigma }}$ and $g_{\mathrm{\Xi }\mathrm{\Xi }}$ directly at the physical pion mass on the lattice, and a full account of systematic uncertainty, including excited-state contamination, finite-volume effects, and continuum extrapolation, all addressed for the first time. We find the ratio of the continuum-limit hyperon coupling constants with respect to the nucleon axial charges to be $g_{\mathrm{\Sigma }\mathrm{\Sigma }}/g_A=0.351(6)(2)$ and $g_{\mathrm{\Xi }\mathrm{\Xi }}/g_A=-0.213(5)(1)$, where the first error includes the statistical and extrapolation systematic uncertainties, and the second error corresponds to systematics associated with varying lattice parameters. The SU(3) symmetry breaking derived from these axial charges is 9%, which is about a factor of 2 smaller than earlier lattice estimates.

We present the technique for resummation of flux tube excitations series arising in pentagon operator expansion program for polygonal Wilson loops in $\mathcal{N}=4$ SYM. Here we restrict ourselves with contributions of one-particle effective states and consider as a particular example ${\mathrm{NMHV}}_6$ amplitude at one-loop. The presented technique is also applicable at higher loops for one effective particle contributions and has the potential for generalization to contributions with more effective particles.

We study microscopic operators describing the experience of an observer falling into the horizon of a unitarily evaporating black hole. For a young black hole, these operators can be taken to act only on the degrees of freedom in the black hole region: the soft—or stretched horizon—modes as well as the semiclassical modes in the zone region. On the other hand, for an old black hole, the operators must also involve radiation emitted earlier; the difference between the two cases comes from statistics associated with the coarse graining performed to obtain the effective theory of the interior. We find that the operators relevant for the interior theory can be defined globally as standard linear operators throughout the microstates, which obey the correct algebra up to corrections exponentially suppressed in the ratio of excitation energy to the Hawking temperature. We conjecture that the existence of such global operators is required for the emergence of the semiclassical picture. We also elucidate the relation between the present construction and entanglement wedge reconstruction of the interior.

We perform the four-dimensional (4D) Kaluza-Klein (KK) reduction of the five-dimensional locally scale invariant Weyl-Dirac gravity. While compactification unavoidably introduces an explicit length scale into the theory, it does it in such a way that the KK radius can be integrated out from the low energy regime, leaving the KK vacuum to still enjoy local scale invariance at the classical level. Imitating a $U(1)\times \tilde{U}(1)$ gauge theory, the emerging 4D theory is characterized by a kinetic Maxwell-Weyl mixing whose diagonalization procedure is carried out in detail. In particular, we identify the unique linear combination which defines the 4D Weyl vector and fully classify the 4D scalar sector. The later consists of (using Weyl language) a coscalar and two in-scalars. The analysis is performed for a general KK $m$-ansatz, parametrized by the power $m$ of the scalar field which factorizes the 4D metric. The no-ghost requirement, for example, is met provided $-\frac{1}{2}\le m\le 0$. An $m$-dependent dictionary is then established between the original 5D Brans-Dicke parameter ${\omega }_5$ and the resulting 4D ${\omega }_4$. The critical ${\omega }_5=-\frac{4}{3}$ is consistently mapped into critical ${\omega }_4=-\frac{3}{2}$. The KK reduced Maxwell-Weyl kinetic mixing cannot be scaled away as it is mediated by a 4D in-scalar (residing within the 5D Weyl vector). The mixing is explicitly demonstrated within the Einstein frame for the special physically motivated choice of $m=-\frac{1}{3}$. For instance, a super critical Brans-Dicke parameter induces a tiny positive contribution to the original (if introduced via the five-dimensional scalar potential) cosmological constant. Finally, some no-scale quantum cosmological aspects are studied at the universal minisuperspace level.

We investigate the properties of the event horizon in the merger between a large black hole and a smaller neutron star. We find that, if the star is compact enough, then, in its rest frame a horizon begins to grow inside the star before it merges with the black hole, in a manner analogous to the growth of the event horizon in stellar collapse. We may say that, ahead of its fall into the larger black hole, the neutron star begins to become a black hole itself. We discuss how the phenomenon, even if not directly observable, can be invariantly characterized. We demonstrate it quantitatively by explicitly constructing the merger event horizon in the extreme-mass-ratio limit. We show that the effect is present for realistic neutron star models and admissible values of the compactness.

We show that the breaking of the conformal invariance of the electromagnetic Lagrangian, which is required for inflationary magnetogenesis, arises naturally in the Poincaré gauge theory. We use the minimal coupling prescription to introduce the electromagnetic gauge fields as well as non-Abelian gauge fields in this theory. Due to the addition of non-Abelian gauge fields, we show that the solar constraints on this model can be naturally evaded. We find that in the minimal version of this model the generated magnetic field is too small to explain the observations. We discuss some generalizations of the gravitational action, including the Starobinsky model and a model with conformal invariance. We show that such generalizations naturally generate the kinetic energy terms required for magnetogenesis. We propose a generalization of the minimal model by adding a potential term, which is allowed within the framework of this model, and show that it leads to sufficiently large magnetic fields.

Ringdown gravitational waves of compact binary mergers are an important target to test general relativity. The main components of the ringdown waveform after merger are black hole quasinormal modes. In general relativity, all multipolar quasinormal modes of a black hole should give the same values of black hole parameters. Although the observed binary black hole events so far are not significant enough to perform the test with ringdown gravitational waves, it is expected that the test will be achieved in third generation detectors. The Japanese gravitational wave detector KAGRA, called bKAGRA for the current configuration, has started observation, and discussions for the future upgrade plans have also started. In this study, we consider which KAGRA upgrade plan is the best to detect the subdominant quasinormal modes of black holes in the aim of testing general relativity. We use a numerical relativity waveform as injected signals that contains two multipolar modes and analyze each mode by matched filtering. Our results suggest that the plan FDSQZ, which improves the sensitivity of KAGRA for broad frequency range, is the most suitable configuration for black hole spectroscopy.

We study the thermodynamics of a five-dimensional Schwarzschild black hole, also known as a five-dimensional Schwarzschild-Tangherlini black hole, in the canonical ensemble using York’s formalism. Inside a cavity of fixed size $r$ and fixed temperature $T$, we find that there is a threshold at $\pi rT=1$ above which a black hole can be in thermal equilibrium with the cavity’s boundary. Moreover, this thermal equilibrium can only be achieved for two specific types of black holes. One is a small black hole (compared with the cavity size $r$) of horizon radius $r_{+1}$, while the other is a large black hole (of the order of the cavity size $r$) of horizon radius $r_{+2}$. In five dimensions, the radii $r_{+1}$ and $r_{+2}$ have an exact expression. Through the path integral formalism, which directly yields the partition function of the system, one obtains the action and thus the free energy for the black hole in the canonical ensemble. The procedure leads naturally to the thermal energy and entropy of the canonical system, the latter turning out to be given by the Bekenstein-Hawking area law $S=\frac{A_{+}}{4}$, where the black hole’s surface area in five dimensions is $A_{+}=2{\pi }^2{r}_{+}^3$ and $r_{+}$ stands for both $r_{+1}$ and $r_{+2}$. We also calculate the heat capacity and find that it is positive when the heat bath is placed at a radius $r$ that is equal or less than the photonic orbit, implying in this case thermodynamic stability, and instability otherwise. This means that the small black hole $r_{+1}$ is unstable and the large one $r_{+2}$ is stable. A generalized free energy is used to compare the possible thermodynamic phase transitions relative to classical hot flat space which has zero free energy, and we show that it is feasible in certain instances that classical hot flat space transits through $r_{+1}$ to settle at the stable $r_{+2}$, with the free energy of the unstable smaller black hole $r_{+1}$ acting as the potential barrier between the two states. It is also shown that, remarkably, the free energy of the larger $r_{+2}$ black hole is zero when the cavity radius is equal to the Buchdahl radius. The relation to the instabilities that arise due to perturbations in the path integral in the instanton solution is mentioned. Hot flat space is made of gravitons and it should be treated quantum mechanically rather than classically. Quantum hot flat space has negative free energy and we find the conditions for which the large black hole phase, quantum hot flat space phase, or both are the ground state of the canonical ensemble. The corresponding phase diagram is displayed in a $r\times T$ plot showing clearly the three possible phases. Using the density of states $\nu$ at a given energy $E$ we also find that the entropy of the large black hole $r_{+2}$ is $S=\frac{A_{+2}}{4}$. In addition, we make the connection between the five-dimensional thermodynamics and York’s four-dimensional results.

We study static, spherically symmetric black holes supported by the Euler-Heisenberg theory of electrodynamics and coupled to two different modified theories of gravity. Such theories are the quadratic $f(R)$ model and Eddington-inspired Born-Infeld gravity, both formulated in metric-affine spaces, where the metric and affine connection are independent fields. We find exact solutions of the corresponding field equations in both cases, characterized by mass, charge, the Euler-Heisenberg coupling parameter, and the modified gravity one. For each such family of solutions, we characterize its horizon structure and the modifications in the innermost region, finding that some subclasses are geodesically complete. The singularity regularization is achieved under two different mechanisms: either the boundary of the manifold is pushed to an infinite affine distance, not being able to be reached in finite time by any geodesic, or the presence of a wormhole structure allows for the smooth extension of all geodesics overcoming the maximum of the potential barrier.

We present an improved spectral algorithm for Cauchy-characteristic extraction and characteristic evolution of gravitational waves in numerical relativity. The new algorithms improve spectral convergence both at the poles of the spherical-polar grid and at future null infinity, as well as increase the temporal resolution of the code. The key to the success of these algorithms is a new set of high-accuracy tests, which we present here. We demonstrate the accuracy of the code and compare with the existing pittnull implementation.

We investigate the parameter distributions of the viable generalized scalar-tensor theory with conventional dust matter after GW170817 in a model-independent way. We numerically construct the models by computing the time evolution of a scalar field, which leads to a positive definite second-order Hamiltonian, and the models are consistent with the observed Hubble parameter. We show the model parameter distributions in the degenerate higher-order scalar-tensor (DHOST) theory and its popular subclasses, e.g., Horndeski and GLPV theories, etc. We find that (1) the Planck mass run rate, ${\alpha }_M$, is insensitive to distinguish the theories; (2) the kinetic-braiding parameter, ${\alpha }_B$, marginally discriminates the models from those of the Horndeski theory in some range; and (3) the parameters for the higher-order theories, ${\alpha }_H$ and ${\beta }_1$, are relatively smaller in magnitude (by several factors) than ${\alpha }_M$ and ${\alpha }_B$, but can still be used for discriminating the theories except for the GLPV theory. Based on the above three facts, we propose a minimal set of parameters that sensibly distinguishes the subclasses of DHOST theories, (${\alpha }_M$, ${\alpha }_B-{\alpha }_M/2$, ${\beta }_1$).

We consider a process where two identical massive particles fall inwards, starting from rest at infinity towards the extremal Kerr black hole, collide outside the event horizon in its vicinity, and produce two massless particles. The center-of-mass energy of collision between the two particles diverges if one of the particles admits a specific critical value of the angular momentum and if the collision takes place at a location arbitrarily close to the event horizon. Assuming the isotropic emission of particles in the center-of-mass frame, we show that one of the massless particles produced has divergent conserved energy comparable to the center-of-mass energy with probability slightly less than half. This particle enters the black hole event horizon which coincides with the Cauchy horizon, turns back, and emerges through the white hole event horizon into another asymptotic region in the maximal extension of Kerr spacetime. Since conserved energy is preserved in this process, it is perceived as a particle with divergent energy by the observer when it reaches infinity. Thus the extremal white hole appears to be a source of ultrahigh energy particles. Similar processes wherein collision takes place slightly inside the black hole event horizon or just outside or inside of the white hole event horizon also produce high energy particles.