We consider Lorentzian wormholes with a phantom field and chiral matter fields. The chiral fields are described by the nonlinear sigma model with or without a Skyrme term. When the gravitational coupling of the chiral fields is increased, the wormhole geometry changes. The single throat is replaced by a double throat with a belly in between. For a maximal value of the coupling, the radii of both throats reach zero. Then the interior part pinches off, leaving a closed universe and two (asymptotically) flat spaces. A stability analysis shows that all wormholes threaded by chiral fields inherit the instability of the Ellis wormhole.

In the present paper, we construct a new solution to the Einstein-Maxwell-dilaton gravity equations describing electrically charged dilaton black holes immersed in a strong external magnetic field, and we study its properties. The black holes described by the solution are rotating but with zero total angular momentum and possess an ergoregion confined in a neighborhood of the horizon. Our results also show that the external magnetic field does not affect the black hole thermodynamics.

We attempt to calculate the point separated noise kernel for the self-similar Tolman-Bondi metric, using a method similar to that developed by Eftekharzadeh et al. for ultrastatic spacetimes, referring to the work by Page. In the case of formation of a naked singularity, the noise kernel thus obtained is found to be regular except on the Cauchy horizon, where it diverges. The behavior of the noise in the case of the formation of a covered singularity is found to be regular. This result seemingly renders backreaction non-negligible, which causes us to question the stability of the results obtained from the semiclassical treatment of the self-similar Tolman-Bondi metric.

We proved that strictly stationary Einstein-Maxwell-axion-dilaton spacetime with negative cosmological constant could not support a nontrivial configuration of complex scalar fields. We considered the general case of the arbitrary number of $U(1)$ gauge fields in the theory under consideration.

We consider a mechanism of dark matter production in the course of the first-order phase transition. We assume that there is an asymmetry between X and $\overline{\mathrm{X}}$ particles of the dark sector. In particular, it may be related to the baryon asymmetry. We also assume that the phase transition is so strongly first order that X particles do not permeate into the new phase. In this case, as the bubbles of the old phase collapse, X particles are packed into $Q$-balls with a huge mass defect. These $Q$-balls compose the present dark matter. We find that the required present dark matter density is obtained for the energy scale of the theory in the ballpark of 1–10 TeV. As an example, we consider a theory with an effective potential of one-loop motivated form.

The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have recently provided new and precise measurements of the cosmic microwave background anisotropy damping tail. This region of the cosmic microwave background angular spectra, thanks to the angular distortions produced by gravitational lensing, can probe the growth of matter perturbations and provide a new test for general relativity. Here we make use of the ACT and SPT power spectrum measurements (combined with the recent WMAP9 data) to constrain $f(R)$ gravity theories. Adopting a parametrized approach, we obtain an upper limit on the length scale of the theory of $B_0<0.86$ at 95% C.L. from ACT, while we get a much stronger limit from SPT with $B_0<0.14$ at 95% C.L.

We show that the cusp in the dark matter distribution required to explain the recently found excess in the gamma-ray spectrum at energies $\sim 130\mathrm{GeV}$ in terms of the dark matter annihilations cannot survive the tidal forces if it is offset by $\sim 1.5°$ from the Galactic center as suggested by observations.

We investigate the thermal QCD transition with two flavors of maximally twisted mass fermions for a set of pion masses, $300\mathrm{MeV}<m_{\pi }<500\mathrm{MeV}$, and lattice spacings, $a<0.09\mathrm{fm}$. We determine the pseudocritical temperatures and discuss their extrapolation to the chiral limit using scaling forms for different universality classes, as well as the scaling form for the magnetic equation of state. For all pion masses considered, we find reasonable consistency with $O(4)$ scaling plus leading corrections. However, a true distinction between the $O(4)$ scenario and a first-order scenario in the chiral limit requires lighter pions than are currently in use in simulations of Wilson fermions.

We discuss production of two pairs of $c\overline{c}$ in proton-proton collisions at the LHC. Both double-parton scattering (DPS) and single-parton scattering contributions are included in the analysis. Each step of DPS is calculated within a $k_t$-factorization approach, which effectively includes some next-to-leading-order corrections. The conditions of how to identify the DPS contribution are presented. The discussed mechanism unavoidably leads to the production of pairs of mesons: $D_i{D}_j$ (each containing $c$ quarks) or ${\overline{D}}_i{\overline{D}}_j$ (each containing $\overline{c}$ antiquarks). We calculate corresponding production rates for different combinations of charmed mesons as well as some differential distribution for ($D^0{D}^0+{\overline{D}}^0{\overline{D}}^0$) production. Within large theoretical uncertainties, the predicted DPS cross section is fairly similar to the cross section measured recently by the LHCb collaboration. The best description is obtained with the Kimber-Martin-Ryskin unintegrated gluon distribution, which very well simulates higher-order corrections. The contribution of single-parton scattering, calculated in the high-energy approximation, turned out to be rather small. Finally, we emphasize the significant contribution of the DPS mechanism to inclusive charmed meson spectra measured recently by ALICE, ATLAS, and the LHCb.

In a strongly coupled quark-gluon plasma, collective excitations of gluons and quarks should dominate over the excitation of individual quasifree gluon and quark modes. To explore this possibility, we computed screening masses for ground-state light-quark mesons and baryons at leading order in a symmetry-preserving truncation scheme for the Dyson-Schwinger equations using a confining formulation of a contact interaction at nonzero temperature. Meson screening masses are obtained from Bethe-Salpeter equations, and baryon analogues from a novel construction of the Faddeev equation, which employs an improved quark-exchange approximation in the kernel. Our treatment implements a deconfinement transition that is coincident with chiral symmetry restoration in the chiral limit, when both transitions are second order. Despite deconfinement, in all $T=0$ bound-state channels, strong correlations persist above the critical temperature, $T>T_c$; and, in the spectrum defined by the associated screening masses, degeneracy between parity-partner correlations is apparent for $T\gtrsim 1.3T_c$. Notwithstanding these results, there are reasons (including Golberger-Treiman relations) to suppose that the inertial masses of light-quark bound states, when they may be defined, vanish at the deconfinement temperature, and that this is a signal of bound-state dissolution. Where a sensible comparison is possible, our predictions are consistent with results from contemporary numerical simulations of lattice-regularized QCD.

The amplitudes for the $pp\to pp{\pi }^0$ process applicable at high energy are discussed in detail. Both diffractive bremsstrahlung (Drell-Hiida-Deck-type model), photon-photon and photon-omega exchange mechanisms are included in the calculation. Large cross sections of the order of mb are predicted. The corresponding differential cross sections in rapidities and transverse momenta of outgoing protons and pions as well as relative azimuthal angle between outgoing protons are calculated for RHIC and LHC energies. The hadronic bremsstrahlung contributions dominate at large (forward, backward) pion rapidities. The diffractive nonresonant background contributes at small ${\pi }^{0}p$ invariant mass and could be therefore misinterpreted as the Roper resonance. We predict strong dependence of the slope in $t$ (squared four-momentum transfer between ingoing and outgoing proton) on the mass of the supplementary excited ${\pi }^{0}p$ system. At high energies and midrapidities, the photon-photon contribution dominates over the diffractive components, however, the corresponding cross section is rather small. The photon-odderon and odderon-photon contributions are included in addition and first estimates (upper limits) of their contributions to rapidity and transverse momentum distribution of neutral pions are presented. We suggest a search for the odderon contribution at midrapidity and at $p_{\perp ,{\pi }^0}\sim 0.5\mathrm{GeV}$. Our predictions are ready for verification at RHIC and LHC. The bremsstrahlung mechanisms discussed here contribute also to the $pp\to p(n{\pi }^{+})$ reaction. Both channels give a sizable contribution to the low-mass single diffractive cross section and must be included in extrapolating the measured experimental single diffractive cross section.

We revisit the reactor antineutrino anomaly using the recent reactor flux independent determination of sizable ${\theta }_{13}$ by considering the full set of the absolute reactor ${\overline{\nu }}_e$ flux measurements. When normalized to the predicted flux of Mueller et al. [Phys. Rev. C 83, 054615 (2011)], the new world average, after including results from Palo Verde, Chooz, and Double Chooz, is $0.959\pm 0.009$ (experiment uncertainty) $\pm 0.027$ (flux systematics). Including the data with kilometer baseline, the new world average is only about $1.4\sigma$ lower than the unity, weakening the significance of the reactor antineutrino anomaly. The upcoming results from Daya Bay, RENO, and the Double Chooz will provide further information about this issue.

We report a measurement of the inclusive semileptonic $B_s^0$ branching fraction in a $121{\mathrm{fb}}^{-1}$ data sample collected near the ${\rm Y}(5S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. Events containing $B_s^{0(*)}{\overline{B}}_s^{0(*)}$ pairs are selected by reconstructing a tag side $D_s^{+}$ and identifying a signal side lepton ${\ell }^{+}$ ($\ell =e$, $\mu$) that is required to have the same-sign charge to ensure that both originate from different $B_s^0$ mesons. The $B_s^0\to X^{-}{\ell }^{+}{\nu }_{\ell }$ branching fraction is extracted from the ratio of the measured yields of $D_s^{+}$ mesons and $D_s^{+}{\ell }^{+}$ pairs and the known production and branching fractions. The inclusive semileptonic branching fraction is measured to be $[10.6\pm 0.5(\mathrm{stat})\pm 0.7(\mathrm{syst})]\%$.

We give a new perspective on the dynamics of conformal theories realized in the $\mathrm{SU}(N)$ gauge theory, when the number of flavors $N_f$ is within the conformal window. Motivated by the renormalization group argument on conformal theories with a finite IR cutoff ${\Lambda }_{\mathrm{IR}}$, we conjecture that the propagator of a meson $G_H(t)$ on a lattice behaves at large $t$ as a power-law corrected Yukawa-type decaying form $G_H(t)={\tilde{c}}_H\exp (-{\tilde{m}}_{H}t)/t^{{\alpha }_H}$ instead of the exponentially decaying form $c_H\exp (-m_{H}t)$, in the small quark mass region where $m_H\le c{\Lambda }_{\mathrm{IR}}$: $m_H$ is the mass of the ground state hadron in the channel $H$ and $c$ is a constant of order 1. The transition between the “conformal region” and the “confining region” is a first order transition. Our numerical results verify the predictions for the $N_f=7$ case and the $N_f=16$ case in the SU(3) gauge theory with the fundamental representation.

This is the third in a series of papers aimed at developing a practical time-domain method for self-force calculations in Kerr spacetime. The key elements of the method are (i) removal of a singular part of the perturbation field with a suitable analytic “puncture,” (ii) decomposition of the perturbation equations in azimuthal ($m$-)modes, taking advantage of the axial symmetry of the Kerr background, (iii) numerical evolution of the individual $m$-modes in $2+1$ dimensions with a finite difference scheme, and (iv) reconstruction of the local self-force from the mode sum. Here we report a first implementation of the method to compute the gravitational self-force. We work in the Lorenz gauge, solving directly for the metric perturbation in $2+1$ dimensions, for the case of circular geodesic orbits. The modes $m=0$, 1 contain nonradiative pieces, whose time-domain evolution is hampered by certain gauge instabilities. We study this problem in detail and propose ways around it. In the current work we use the Schwarzschild geometry as a platform for development; in a forthcoming paper—the fourth in the series—we apply our method to the gravitational self-force in Kerr geometry.

In this work, we present the hitherto most efficient and accurate method for the numerical integration of post-Newtonian equations of motion. We first transform the Poisson system as given by the post-Newtonian approximation to canonically symplectic form. Then we apply Gauss Runge-Kutta schemes to numerically integrate the resulting equations. This yields a convenient method for the structure preserving long-time integration of post-Newtonian equations of motion. In extensive numerical experiments, this approach turns out to be faster and more accurate (i) than previously proposed structure preserving splitting schemes and (ii) than standard explicit Runge-Kutta methods. We also show our approach to be appropriate for simulations on transitional precession.

We reconsider the recent observation by the D0 experiment of a sizable like-sign dimuon charge asymmetry, highlighting that it could be affected by $CP$-violating new physics contributions not only in $B_d$- and $B_s$-meson mixings but also in semileptonic decays of $b$ and $c$ quarks producing muons. The D0 measurement could be reconciled with the standard model expectations for neutral-meson mixings, provided that the $CP$ asymmetry in semileptonic $b$ ($c$) decays reaches 0.3% (1%). Such effects, which lie within the available (rather loose) experimental bounds, would be clear indications of new physics and should be investigated experimentally.

We present a new class of exact self-similar solutions possessing cylindrical or spherical symmetry in Born–Infeld theory. A cylindrically symmetric solution describes the propagation of a cylindrical electromagnetic disturbance in a constant background magnetic field in Born–Infeld electrodynamics. We show that this solution corresponds to vacuum breakdown and the subsequent propagation of an electron-positron avalanche. The proposed method of finding exact analytical solutions can be generalized to the model of a spherically symmetric scalar Born–Infeld field in the ($n+1$)-dimensional Minkowski space-time. As an example, the case $n=3$ is discussed.

We investigate the nonperturbative stability of asymptotically anti-de Sitter gravity coupled to tachyonic scalar fields with mass near the Breitenlohner-Freedman bound. Such scalars are characterized by power-law radial decay near the anti-de Sitter boundary, and typical boundary conditions are “Dirichlet” (which fix the slower falloff mode) or “Neumann” (which fix the faster falloff mode) type. More generally though, these “designer gravity” theories admit a large class of boundary conditions defined by a functional relation between the two modes. While previous stability proofs have considered boundary conditions that are deformations of the Neumann theory, the goal of this paper is to analyze stability in designer gravity with boundary conditions that are irrelevant deformations of the Dirichlet theory. We obtain a lower bound on the energy using spinor charge methods and show that, for the most interesting class of such boundary conditions, the theory is always stable. We argue that the deformed theory flows to a new fixed point in the ultraviolet, which is just the Neumann theory. We also derive a corresponding “effective potential” that implies stability if it has a global minimum.

The Bethe-Salpeter amplitude for the fermion-antifermion bound state in the Schwinger model is investigated. The dependence on the relative time and position in the center-of-mass frame in all contributing instanton sectors is analyzed. The same is accomplished for the relative energy and momentum variables. Several interesting properties of the amplitude are revealed. The explicit threshold structure is demonstrated.