We investigate a class of gravitational $pp$ waves which represent the exterior vacuum field of spinning particles moving with the speed of light. Such exact spacetimes are described by the original Brinkmann form of the $pp$-wave metric including the often-neglected off-diagonal terms. We put emphasis on a clear physical and geometrical interpretation of these off-diagonal metric components. We explicitly analyze several new properties of these spacetimes associated with the spinning character of the source, such as rotational dragging of frames, geodesic deviation, impulsive limits and the corresponding behavior of geodesics.

We discuss new exact solutions to nonminimally extended Einstein–Yang–Mills equations describing spherically symmetric static wormholes supported by the gauge field of the Wu-Yang type in a dark energy environment. We focus on the analysis of three types of exact solutions to the gravitational field equations. Solutions of the first type relate to the model, in which the dark energy is anisotropic; i.e., the radial and tangential pressures do not coincide. Solutions of the second type correspond to the isotropic pressure tensor; in particular, we discuss the exact solution, for which the dark energy is characterized by the equation of state for a string gas. Solutions of the third type describe the dark energy model with constant pressure and energy density. For the solutions of the third type, we consider in detail the problem of horizons and find constraints for the parameters of nonminimal coupling and for the constitutive parameters of the dark energy equation of state, which guarantee that the nonminimal wormholes are traversable.

We study tachyon field inflation in the light of the $\text{Planck}+\mathrm{WMAP}+\mathrm{BICEP}2+\mathrm{BAO}$ joint data. While the minimally coupled tachyon field inflation is consistent with the Planck2013 data, it is not confirmed by the $\text{Planck}+\mathrm{WMAP}+\mathrm{BICEP}2+\mathrm{BAO}$ data set. However, a nonminimally coupled tachyon field inflation is consistent with this joint data set.

We study aspects of quantum cosmology in the presence of modified space-time geometry. In particular, within the context of gravity’s rainbow modified geometry, motivated from quantum gravity corrections at the Planck energy scale, we show that the distortion of the metric leads to a Wheeler-DeWitt equation whose solution admits outgoing plane waves. Hence, a period of cosmological inflation may arise without the need of introducing an inflaton field.

We analyze the effects of introducing vector fermions in the Higgs triplet model. In this scenario, the model contains, in addition to the Standard Model particle content, one triplet Higgs representation and a variety of vectorlike fermion states, including singlet, doublet, and triplet states. We investigate the electroweak precision variables and impose restrictions on model parameters. We show that, for some representations, introducing vector quarks significantly alters the constraints on the mass of the doubly charged Higgs boson, bringing it in closer agreement with present experimental constraints. We also study the effects of introducing the vectorlike fermions on neutral Higgs phenomenology, in particular on the loop-dominated decays $H\to \gamma \gamma$ and $H\to Z\gamma$, and the restrictions they impose on the parameter space.

We present renormalization constants of overlap quark bilinear operators on $2+1$-flavor domain wall fermion configurations. This setup is being used by the $\chi \mathrm{QCD}$ Collaboration in calculations of physical quantities such as strangeness in the nucleon and the strange and charm quark masses. The scale-independent renormalization constant for the axial-vector current is computed using the Ward identity. The renormalization constants for scalar, pseudoscalar, and vector currents are calculated in the RI-MOM scheme. Results in the $\overline{\mathrm{MS}}$ scheme are also given. The step scaling function of quark masses in the RI-MOM scheme is computed as well. The analysis uses, in total, six different ensembles of three sea quarks, each on two lattices with sizes ${24}^3\times 64$ and ${32}^3\times 64$ at spacings $a=(1.73\mathrm{GeV}{)}^{-1}$ and $(2.28\mathrm{GeV}{)}^{-1}$, respectively.

Here we demonstrate, first, the construction of dualities using the exact renormalization group approach and, second, that spatial noncommutativity can emerge as such a duality. This is done in a simple quantum mechanical setting that establishes an exact duality between the commutative and noncommutative quantum Hall systems with harmonic interactions. It is also demonstrated that this link can be understood as a blocking (coarse graining) transformation in time that relates commutative and noncommutative degrees of freedom.

The construction of a generic parametrization to describe the spacetime geometry around astrophysical black hole candidates is an important step to test the Kerr black hole hypothesis. In the last few years, the Johannsen-Psaltis metric has been the most common framework to study possible deviations from the Kerr solution with present and near-future observations. Recently, Cardoso, Pani, and Rico have proposed a more general parametrization. The aim of the present paper is to study this new metric in a specific context, namely, the thermal spectrum of geometrically thin and optically thick accretion disks. The most relevant finding is that the spacetime geometry around objects that look like very-fast-rotating Kerr black holes may still have large deviations from the Kerr solution. This is not the case with the Johannsen-Psaltis metric, which means the latter is missing an important class of non-Kerr spacetimes.

Understanding the biasing between the clustering properties of halos and the underlying dark matter distribution is important for extracting cosmological information from ongoing and upcoming galaxy surveys. While on sufficiently large scales the halo overdensity is a local function of the mass density fluctuations, on smaller scales the gravitational evolution generates nonlocal terms in the halo density field. We characterize the magnitude of these contributions at third order in perturbation theory by identifying the coefficients of the nonlocal invariant operators, and extend our calculation to include nonlocal (Lagrangian) terms induced by a peak constraint. We apply our results to describe the scale dependence of halo bias in cosmologies with massive neutrinos. The inclusion of gravity-induced nonlocal terms and, especially, a Lagrangian $k^2$ contribution is essential to reproduce the numerical data accurately. We use the peak-background split to derive the numerical values of the various bias coefficients from the excursion set peak mass function. For neutrino masses in the range $0\le \sum _i{m}_{{\nu }_i}\le 0.6\mathrm{eV}$, we are able to fit the data with a precision of a few percents up to $k=0.3h{\mathrm{Mpc}}^{-1}$ without any free parameter.

We investigate the possibility of spatially homogeneous and inhomogeneous chiral fermion-antifermion condensation and superconducting fermion-fermion pairing in the ($1+1$)-dimensional model by Chodos et al. [Phys. Rev. D 61, 045011 (2000)] generalized to continuous chiral invariance. The consideration is performed at nonzero values of temperature $T$, electric charge chemical potential $\mu$ and chiral charge chemical potential ${\mu }_5$. It is shown that at $G_1<G_2$, where $G_1$ and $G_2$ are the coupling constants in the fermion-antifermion and fermion-fermion channels, the $(\mu ,{\mu }_5)$-phase structure of the model is in a one-to-one correspondence with the phase structure at $G_1>G_2$ (called duality correspondence). Under the duality transformation the (inhomogeneous) chiral symmetry breaking (CSB) phase is mapped into the (inhomogeneous) superconducting (SC) phase and vice versa. If $G_1=G_2$, then the phase structure of the model is self-dual. Nevertheless, the degeneracy between the CSB and SC phases is possible in this case only when there is a spatial inhomogeneity of condensates.

Elements are given of a calculation that identifies the size of a proton in the Schrödinger equation for lepton-proton bound states, using the renormalization group procedure for effective particles (RGPEP) in quantum field theory, executed only up to the second order of expansion in powers of the coupling constant. Already in this crude approximation, the extraction of size of a proton from bound-state observables is found to depend on the lepton mass, so the smaller the lepton mass the larger the proton size extracted from the same observable bound-state energy splitting. In comparing hydrogen and muon-proton bound-state dynamics, the crude calculation suggests that the difference between extracted proton sizes in these two cases can be a few percent. Such values would match the order of magnitude of the currently discussed proton-size differences in leptonic atoms. Calculations using the RGPEP of higher than second order are required for a precise interpretation of the energy splittings in terms of the proton size in the Schrödinger equation. Such calculations should resolve the conceptual discrepancy between two conditions: that the renormalization group scale required for high accuracy calculations based on the Schrödinger equation is much smaller than the proton mass (on the order of a root of the product of reduced and average masses of constituents) and that the energy splittings due to the physical proton size can be interpreted by ignoring corrections due to the effective nature of constituents in the Schrödinger equation.

Nonminimally coupled free scalar fields may be unstable in the spacetime of compact objects. Such instability can be triggered by classical seeds or, more simply, by quantum fluctuations giving rise to the so-called “vacuum awakening effect.” Here, we investigate how the parameter space that characterizes the instability is affected when the object gains some rotation. For this purpose, we focus on the stability analysis of nonminimally coupled scalar fields in the spacetime of slowly spinning matter shells.

In this paper, we formulate statistical mechanics of the polymerized systems in the semiclassical regime. On the corresponding polymeric symplectic manifold, we set up a noncanonical coordinate system in which all of the polymeric effects are summarized in the density of states. Since we show that the polymeric effects only change the number of microstates of a statistical system, working in this coordinate is quite reasonable from the statistical point of view. The results show that the number of microstates decreases due to existence of an upper bound for the momentum of the test particles in the polymer framework. We obtain a corresponding canonical partition function by means of the deformed density of states. By using the partition function, we study thermodynamics of the ideal gas in the polymer framework and show that our results are in good agreement with those that arise from the full quantum consideration at high temperature, and they coincide with their usual counterpart in the limit of low temperature.

Detection of gravitational waves (GWs) provides us with an opportunity to test general relativity in strong and dynamical regimes of gravity. One of the tests is checking whether GW propagates with the speed of light or not. This test is crucial because the velocity of GW has not ever been directly measured. Propagation speed of a GW can deviate from the speed of light due to the modification of gravity, graviton mass, and the nontrivial spacetime structure such as extra dimensions and quantum gravity effects. Here we report a simple method to measure the propagation speed of a GW by directly comparing arrival times between GWs and neutrinos from supernovae or photons from short gamma-ray bursts. As a result, we found that the future multimessenger observations of a GW, neutrinos, and photons can test the GW propagation speed with the precision of $\sim 10^{-16}$, improving the previous suggestions by 8–10 orders of magnitude. We also propose a novel method that distinguishes the true signal due to the deviation of GW propagation speed from the speed of light and the intrinsic time delay of the emission at a source by looking at the redshift dependence.

Dynamics at large redshift near the horizon of an extreme Kerr black hole are governed by an infinite-dimensional conformal symmetry. This symmetry may be exploited to analytically, rather than numerically, compute a variety of potentially observable processes. In this paper we compute and study the conformal transformation properties of the gravitational radiation emitted by an orbiting mass in the large-redshift near-horizon region.

We discuss cosmological models for an eternal Universe. Physical observables show no singularity from the infinite past to the infinite future. While the Universe is evolving, there is no beginning and no end—the Universe exists forever. The early state of inflation is described in two different, but equivalent pictures. In the freeze frame the Universe emerges from an almost static state with flat geometry. After entropy production it shrinks and “thaws” slowly from a “freeze state” with extremely low temperature. The field transformation to the second “big bang picture” (Einstein frame) is singular. This “field singularity” is responsible for an apparent singularity of the big bang. Furthermore, we argue that past-incomplete geodesics do not necessarily indicate a singularity or beginning of the Universe. Proper time ceases to be a useful concept for physical time if particles become massless. We propose to define physical time by counting the number of zeros of a component of the wave function. This counting is independent of the choice of coordinates and frames, and applies to massive and massless particles alike.

Shift symmetry is essential to protect the flatness of the potential, even beyond the super-Planckian vacuum expectation value for an inflaton field. The breaking of the shift symmetry can yield potentials suitable for super-Planckian excursion of the inflaton. The aim of this paper is to illustrate that it is indeed possible to break the shift symmetry dynamically within four-dimensional supergravity prior to a long phase of inflation. Thanks to the shift symmetry, the leading contribution to the inflaton potential is free from the dangerous exponential factor even after its breaking, which is the main obstacle to realizing the super-Planckian inflation in supergravity. But, in our simple model, the resulting inflaton potential is a cosine-type potential rather than the power-law one, and it is difficult to realize a super-Planckian breaking scale, unfortunately.

We describe the formalism of a quantitative analytic model for the evolution of realistic wiggly (as opposed to Goto-Nambu) cosmic strings. The model is particularly suited for describing the evolution of small-scale structure on string networks. We discuss model solutions in the extreme limit where the wiggles make up a high fraction of the total energy of the string network (which physically corresponds to the tensionless limit) and also provide a brief discussion of the opposite (linear) limit where wiggles are a small fraction of the total energy. A companion paper will discuss the detailed modeling and scaling behavior of the small-scale wiggles in the general model, together with a basic comparison with numerical simulations.

We constrain the parameters of a self-interacting massive dark matter scalar particle in a condensate using the kinematics of the eight brightest dwarf spheroidal satellites of the Milky Way. For the case of a repulsive self-interaction, the condensate develops a mass density profile with a characteristic scale radius that is closely related to the fundamental parameters of the theory. We find that the velocity dispersion of dwarf spheroidal galaxies suggests a scale radius of the order of 1 kpc, in tension with previous results found using the rotational curve of low-surface-brightness and dwarf galaxies. The new value is however favored marginally by the constraints coming from the number of relativistic species at big bang nucleosynthesis. We discuss the implications of our findings for the particle dark matter model and argue that while a single classical coherent state can correctly describe the dark matter in dwarf spheroidal galaxies, it cannot play, in general, a relevant role for the description of dark matter in bigger objects.