We propose a new algorithm based on the Metropolis sampling method to perform Monte Carlo integration for path integrals in the recently proposed formulation of quantum field theories on the Lefschetz thimble. The algorithm is based on a mapping between the curved manifold defined by the Lefschetz thimble of the full action and the flat manifold associated with the corresponding quadratic action. We discuss an explicit method to calculate the residual phase due to the curvature of the Lefschetz thimble. Finally, we apply this new algorithm to a simple one-plaquette model where our results are in perfect agreement with the analytic integration. We also show that for this system the residual phase does not represent a sign problem.

We investigate the thermalization process of boosted charged AdS black holes in the Einstein-Maxwell system in the presence of an ionic lattice formed by a spatially varying chemical potential. We calculate perturbations of the black holes by the lattice and investigate how the momentum relaxation occurs through umklapp scattering. In the WKB approximation, both the momentum relaxation rate and entropy production rate are analytically obtained and the first law of black holes is derived in the irreversible process. Interestingly, both the analytical and numerical calculations show that the momentum relaxation rate or the entropy production rate does not approach zero in the zero temperature limit unless the velocity of the black hole is zero. In the dual field theory side, this indicates that persistent current does not exist even in the zero temperature limit, implying that the “ionic lattice” does not behave as a perfect lattice in a strongly coupled dual field theory.

Exact configurations of the four-dimensional Skyrme model are presented. The static configurations have the profile. Which behaves as a kink and, consequently, the corresponding energy-momentum tensor describes a domain wall. Furthermore, a class of exact time-periodic Skyrmions is discovered. Within such a class, it is possible to disclose a remarkable phenomenon that is a genuine effect of the Skyrme term. For a special value of the frequency the Skyrmions admit a nonlinear superposition principle. One can combine two or more exact “elementary” Skyrmions (which may depend in a nontrivial way on all the spacelike coordinates) into a new exact composite Skyrmion. Because of such a superposition law, despite the explicit presence of nonlinear effects in the energy-momentum tensor, the interaction energy between the elementary Skyrmions can be computed exactly. The relations with the appearance of Skyrme crystals are discussed.

We study large-$N$ orbifold equivalences involving three-dimensional $\mathcal{N}=3$ and $\mathcal{N}=4$ supersymmetric quiver Chern-Simons-matter theories. The gravity dual of the $\mathcal{N}=3$ Chern-Simons-matter theory is described by ${\mathrm{AdS}}_4\times {\mathcal{M}}_7$, where the tri-Sasaki manifold ${\mathcal{M}}_7$ is known as the Eschenburg space. We find evidence that a large-$N$ orbifold equivalence for the $\mathcal{N}=4$ case continues from the $M$-theory limit to the weak coupling limit. For the $\mathcal{N}=3$ case, we find consistent large-$N$ equivalences involving a projection changing the nodes of the gauge groups, and also for a projection changing Chern-Simons levels where for the latter projection, the Bogomol’nyi Prasad-Sommerfield monopole operators behave as expected in large-$N$ equivalence. For both cases we show, using the gravity dual, that the critical temperature of the confinement/deconfinement transition does not change and the entropy behaves as expected under the orbifold equivalence. We show that large-$N$ orbifold equivalence changing Chern-Simons levels can be explained using the planar equivalence in the mirror dual.

We consider the nonlinear massive gravity as a theory of a number of Stückelberg scalar fields minimally coupled to the Einstein-Hilbert gravity and argue that the counting of degrees of freedom can be done for scalar theory and gravity separately. In this paper we investigate the system with only two Stückelberg scalar fields. In this case we find the analytic expression for the determinant of the kinetic matrix of the scalar field Lagrangian and perform the full constraint analysis. In $1+1$ space-time dimensions, the theory corresponds to the full nonlinear massive gravity, and this determinant vanishes identically. In this case we find two first-class constraints and present the corresponding gauge symmetry of the theory which eliminates both scalar degrees of freedom. In $3+1$ dimensions, the determinant of the kinetic matrix does not vanish identically and, for generic initial conditions, both scalar fields are propagating.

Theories with a nonminimal coupling between the space-time curvature and matter fields introduce an extra force due to the nonconservation of the matter energy momentum. In the present work the theoretical consistency of such couplings is studied using a scalar field Lagrangian to model the matter content. The conditions that the coupling does not introduce ghosts, classical instabilities or superluminal propagation of perturbations are derived. These consistency conditions are then employed to rule out or severely restrict the forms of the nonminimal coupling functions considered in the previous literature. For example, a power-law coupling is viable only for sublinear positive power of the curvature scalar.

We perform a parameter study of nonspinning, equal- and unequal-mass black hole binaries on generic, eccentric orbits in numerical relativity. The linear momentum considered ranges from that of a circular orbit to ten times that value. We discuss the different manifestations of zoom-whirl behavior in the hyperbolic and the elliptic regime. The hyperbolic data set applies to dynamical capture scenarios (e.g., in globular clusters). Evolutions in the elliptic regime correspond to possible end states of supermassive black hole binaries. We spot zoom-whirl behavior for eccentricities as low as $e\sim 0.5$, i.e., within the expected range of eccentricities in massive black hole binaries from galaxy mergers and binaries near galactic centers. The resulting gravitational waveforms reveal a rich structure, which will effectively break degeneracies in parameter space, improving parameter estimation.

Here we consider the possibility of preheating the Universe via the parametric amplification of a massless, $U(1)$ Abelian gauge field. We assume that the gauge field is coupled to the inflaton via a dilaton-like coupling, a conformal factor with one free parameter. We present the results of high-resolution three-dimensional simulations of this model and show that this mechanism efficiently preheats the Universe to a radiation-dominated final state.

This paper studies intermediate homogenization of inhomogeneous cosmological models. It shows that spherically symmetric models, regardless of the equation of state, can undergo intermediate homogenization; i.e., a model can approach a homogeneous and isotropic state (which acts as a saddle point) from a relatively wide range of initial inhomogeneous conditions. The homogenization is not permanent—just temporary. Eventually, the model evolves toward a future inhomogeneous state. We also looked at the problem of the gravitational entropy. All definitions of entropy that we checked give decreasing gravitational entropy during the homogenization process. Thus, we should either accept that gravitational entropy can decrease or try to define it in other ways than just via density gradients, as these decrease during homogenization.

Searches for gravitational-wave bursts (transient signals, typically of unknown waveform) require identification of weak signals in background detector noise. The sensitivity of such searches is often critically limited by non-Gaussian noise fluctuations that are difficult to distinguish from real signals, posing a key problem for transient gravitational-wave astronomy. Current noise rejection tests are based on the analysis of a relatively small number of measured properties of the candidate signal, typically correlations between detectors. Multivariate analysis (MVA) techniques probe the full space of measured properties of events in an attempt to maximize the power to accurately classify events as signal or background. This is done by taking samples of known background events and (simulated) signal events to train the MVA classifier, which can then be applied to classify events of unknown type. We apply the boosted decision tree (BDT) MVA technique to the problem of detecting gravitational-wave bursts associated with gamma-ray bursts. We find that BDTs are able to increase the sensitive distance reach of the search by as much as 50%, corresponding to a factor of $\sim 3$ increase in sensitive volume. This improvement is robust against trigger sky position, large sky localization error, poor data quality, and the simulated signal waveforms that are used. Critically, we find that the BDT analysis is able to detect signals that have different morphologies from those used in the classifier training and that this improvement extends to false alarm probabilities beyond the $3\sigma$ significance level. These findings indicate that MVA techniques may be used for the robust detection of gravitational-wave bursts with a priori unknown waveform.

The evolution of perturbations is a crucial part of the phenomenology of the dark sector cosmology. We advocate parametrizing these perturbations using equations of state for the entropy perturbation and the anisotropic stress. For small perturbations, these equations of state will be linear in the density, velocity and metric perturbations, and in principle these can be related back to the field content of the underlying model allowing for confrontation with observations. We illustrate our point by constructing gauge-invariant entropy perturbations for theories where the dark sector Lagrangian is a general function of a scalar field, its first and second derivatives, and the metric and its first derivative, $\mathcal{L}=\mathcal{L}(\varphi ,{\partial }_{\mu }\varphi ,{\partial }_{\mu }{\partial }_{\nu }\varphi ,g_{\mu \nu },{\partial }_{\alpha }{g}_{\mu \nu })$. As an example, we show how to apply this approach to the case of models of kinetic gravity braiding.

We study the two-body decay of a mother particle into a massless daughter. We further assume that the mother particle is unpolarized and has a generic boost distribution in the laboratory frame. In this case, we show analytically that the laboratory frame energy distribution of the massless decay product has a peak, whose location is identical to the (fixed) energy of that particle in the rest frame of the corresponding mother particle. Given its simplicity and “invariance” under changes in the boost distribution of the mother particle, our finding should be useful for the determination of masses of mother particles. In particular, we anticipate that such a procedure will then not require a full reconstruction of this two-body decay chain (or, for that matter, information about the rest of the event). With this eventual goal in mind, we make a proposal for extracting the peak position by fitting the data to a well-motivated analytic function describing the shape of such an energy distribution. This fitting function is then tested on the theoretical prediction for top quark pair production and its decay, and it is found to be quite successful in this regard. As a proof of principle of the usefulness of our observation, we apply it for measuring the mass of the top quark at the LHC, using simulated data and including experimental effects.

Dijet resonance searches are simple, yet powerful and model-independent, probes for discovering new particles at hadron colliders. Once such a resonance has been discovered it is important to determine the mass, spin, couplings, chiral behavior and color properties to determine the underlying theoretical structure. We propose a new variable which, in the absence of decays of the resonance into new nonstandard states, distinguishes between color-octet and color-singlet resonances. To keep our study widely applicable we study phenomenological models of color-octet and color-singlet resonances in flavor universal as well as flavor nonuniversal scenarios. We present our analysis for a wide range of mass (2.5–6 TeV), couplings and flavor scenarios for the LHC with center of mass energy of 14 TeV and varying integrated luminosities of 30, 100, 300 and $1000{\mathrm{fb}}^{-1}$. We find encouraging results to distinguish color-octet and color-singlet resonances for different flavor scenarios at the LHC.

$K^{*}$ mesons and in particular the $K^{*}(892)$ were frequently addressed in lattice simulations, but always while ignoring that the $K^{*}(892)$ decays strongly. We present an exploratory extraction of the masses and widths for the $K^{*}$ resonances by simulating $K\pi$ scattering in $p$ waves with $I=1/2$ on the lattice. The $K\pi$ system with total momenta $P=\frac{2\pi }{L}{e}_z$, $\frac{2\pi }{L}(e_x+e_y)$, and 0, that allows the extraction of phase shifts at several values of $K\pi$ relative momenta, is studied. A Breit-Wigner fit of the phase renders a $K^{*}(892)$ resonance mass $m^{\mathrm{lat}}=891\pm 14\mathrm{MeV}$ and the $K^{*}(892)\to K\pi$ coupling $g^{\mathrm{lat}}=5.7\pm 1.6$ compared to the experimental values $m^{\exp }\approx 892\mathrm{MeV}$ and $g^{\exp }=5.72\pm 0.06$, where $g$ parametrizes the $K^{*}\to K\pi$ width. When extracting the phase shift around the $K^{*}(1410)$ and $K_2^{*}(1430)$ resonances, we take into account the mixing of $p$ waves with $d$ waves and assume that the scattering is elastic in our simulation. This gives us an estimate of the $K^{*}(1410)$ resonance mass $m^{\mathrm{lat}}=1.33\pm 0.02\mathrm{GeV}$ compared to $m^{\exp }=1.414\pm 0.0015\mathrm{GeV}$, assuming the experimental $K^{*}(1410)\to K\pi$ coupling. We contrast the resonant $I=1/2$ channel with the repulsive nonresonant $I=3/2$ channel, where the phase is found to be negative and small, in agreement with experiment.

In this paper we study the photoproduction of top quarks in coherent $pp$, $pPb$, and $PbPb$ interactions at LHC energies in the collinear formalism. We present our predictions for the total cross sections, event rates, and rapidity distributions. The dependence in the parton distributions used in the calculations is analyzed, and the effect of the shadowing corrections is estimated.

It is well known that the teleparallel equivalent of general relativity yields the same vacuum solutions as general relativity does, which ensures that this particular teleparallel model is in good agreement with experiments. A lesser known result concerns the existence of a wider class of teleparallel models which also admits these solutions when the spacetime is diagonalizable by means of a coordinate change. However, it is stated by Obukhov and Pereira [Phys. Rev. D 67, 044016 (2003)] that the teleparallel equivalent of general relativity is the only teleparallel model which admits black holes. To show that this statement is not true, I present the result of Hayashi and Shirafuji [Phys. Rev. D 19, 3524 (1979)], which proves the existence of this wider class by showing the equivalence between two Lagrangians. It turns out that this equivalence also holds for plane-wave metrics. In addition, I update the constraints on the parameters of the teleparallel models.

In this work the generation of generalized Chern-Simons terms in three-dimensional quantum electrodynamics with high spatial derivatives is studied. We analyze the self-energy corrections to the gauge field propagator by considering an expansion of the corresponding amplitudes up to third order in the external momenta. The divergences of the corrections are determined and explicit forms for the Chern-Simons terms with high derivatives are obtained. Some unusual aspects of the calculation are stressed and the existence of a smooth isotropic limit is proved. The transversality of the anisotropic gauge propagator is also discussed.

Two-dimensional causal dynamical triangulations provide a definition of the path integral for projectable two-dimensional Hořava-Lifshitz quantum gravity. We solve the theory coupled to gauge fields.

We analyze the proton recoil energy and angular distribution of the radiative ${\beta }^{-}$ decay of the neutron to leading order in the large baryon mass expansion by taking into account the contributions of the proton-photon correlations. We show that the account for the proton-photon correlations does not contradict the description of the radiative corrections to the lifetime of the neutron and the proton recoil energy spectrum of the neutron ${\beta }^{-}$ decay in terms of the functions $(\alpha /\pi )g_n(E_e)$ and $(\alpha /\pi )f_n(E_e)$, where $E_e$ is the electron energy. In addition we find that the contributions of the proton-photon correlations in the radiative ${\beta }^{-}$ decay of the neutron to the proton recoil asymmetry $C$ are of order ${10}^{-4}$. They make the contributions of the radiative corrections to the proton recoil asymmetry $C$ symmetric with respect to a change $A_0\leftrightarrow B_0$, where $A_0$ and $B_0$ are the correlation coefficients of the neutron ${\beta }^{-}$ decay.

The post-Newtonian parameter $\gamma$ resulting from a universal scalar-matter coupling is investigated in Brans-Dicke–like scalar-tensor theories where the scalar potential is assumed to be negligible. Conversely to previous studies, we use a perfect fluid formalism in order to get the explicit scalar-field equation. It is shown that the metric can be put in its standard post-Newtonian form. However, it is pointed out that $1-\gamma$ could be either positive, null or negative for a finite value of ${\omega }_0$, depending on the coupling function, while scalar-tensor theories without coupling always predict $\gamma <1$ for a finite value of ${\omega }_0$.