We generalize our holographic derivation of spontaneous angular momentum generation in $2+1$ dimensions in several directions. We consider cases when a parity-violating perturbation responsible for the angular momentum generation can be nonmarginal (while in our previous paper we restricted to a marginal perturbation), including all possible two-derivative interactions, with parity violations triggered both by gauge and gravitational Chern-Simons terms in the bulk. We make only a minimal assumption about the bulk geometry that it is asymptotically AdS, respects the Poincaré symmetry in $2+1$ dimensions, and has a horizon. In this generic setup, we find a remarkably concise and universal formula for the expectation value of the angular momentum density, to all orders in the parity violating perturbation.

We use a general relativistic approach to investigate the effects of weak cosmological magnetic fields on linear rotational perturbations during the radiation and dust epochs of the Universe. This includes ordinary kinematic vorticity, as well as vortexlike inhomogeneities in the density distribution of the matter. Our study confirms that magnetism sources both types of perturbations and that its presence helps cosmic rotation to survive longer. In agreement with previous Newtonian studies, we find that during the dust era vorticity decays slower than in nonmagnetized cosmologies. The relativistic nature of the treatment means that we can also investigate the epoch prior to equipartition. There, the magnetic effect is more pronounced, since it helps both of the above rotational distortions to maintain constant magnitude throughout the radiation era. Overall, magnetized universes not only generate vorticity but also provide a much better environment for the survival of rotational perturbations, than their magnetic-free counterparts.

We subject the stationary solutions of inviscid and axially symmetric rotational accretion to a time-dependent radial perturbation, which includes nonlinearity to any arbitrary order. Regardless of the order of nonlinearity, the equation of the perturbation bears a form that is similar to the metric equation of an analogue acoustic black hole. We bring out the time dependence of the perturbation in the form of a Liénard system by requiring the perturbation to be a standing wave under the second order of nonlinearity. We perform a dynamical systems analysis of the Liénard system to reveal a saddle point in real time, whose implication is that instabilities will develop in the accreting system when the perturbation is extended into the nonlinear regime. We also model the perturbation as a high-frequency traveling wave and carry out a Wentzel-Kramers-Brillouin analysis, treating nonlinearity iteratively as a very feeble effect. Under this approach, both the amplitude and the energy flux of the perturbation exhibit growth, with the acoustic horizon segregating the regions of stability and instability.

In a renormalizable $SO(10)$ theory, all fermion mass matrices are linear combinations of three fundamental types, $M^{10}$, $M^{\overline{126}}$, and $M^{120}$, whose superscripts indicate their $SO(10)$ transformation properties. We point out that each of these fundamental mass matrices possesses a natural symmetry that can be used to generate an unbroken horizontal symmetry $\mathcal{G}$, if the natural symmetry is taken to be the residual symmetry. This built-in symmetry is a Coxeter group. If it is finite, it must be one of five groups: $S_4$, $Z_2\times S_4$, $Z_2\times A_5$, and two “rank-4” groups. These symmetries place constraints on the fundamental mass matrices and reduce the number of parameters in an $SO(10)$ fit. Since they are built in and can be derived theoretically, it is hoped that they impose better constraints than those without a theoretical basis. However, that has yet to be confirmed because there is no attempt to fit the experimental data in this article, except to count the number of free parameters. To illustrate the similarities and differences of various kinds of constraints, a comparison is made with an existing $S_4$ model and with models possessing the Fritzsch texture.

Within the dual superconductor scenario for the QCD confining vacuum, the chromoelectric field generated by a static $q\overline{q}$ pair can be fitted by a function derived, by dual analogy, from a simple variational model for the magnitude of the normalized order parameter of an isolated Abrikosov vortex. Previous results for the SU(3) vacuum are revisited, but here the transverse chromoelectric field is measured by means of the connected correlator of two Polyakov loops and, in order to reduce noise, the smearing procedure is used instead of cooling. The penetration and coherence lengths of the flux tube are then extracted from the fit and compared with previous results.

Using the QCD sum rule with its operator product expansion reliably determined from lattice calculations for the pressure and energy density of hot QCD matter, we calculate the strength of the $J/\psi$ wave function at the origin and find that it decreases with temperature when the temperature is in the vicinity of the transition temperature. This result is shown to follow exactly that obtained from the solution of the Schrödinger equation for a charm and anticharm quark pair with a temperature independent quark mass using the free energy from lattice calculations as the potential and is in sharp contrast to that using the deeper potential associated with the internal energy, which shows an enhanced strength of the $J/\psi$ wave function at the origin. Our result thus suggests that the free energy potential from lattice calculations is the appropriate heavy-quark potential for analyzing the charmonium spectrum at a finite temperature.

We study saturation effects in the production of forward dijets in proton-lead collisions at the Large Hadron Collider, using the framework of High Energy Factorization. Such configurations, with both jets produced in the forward direction, probe the gluon density of the lead nucleus at a small longitudinal momentum fraction and also limit the phase space for emissions of additional jets. We find significant suppression of the forward dijet azimuthal correlations in proton-lead versus proton-proton collisions, which we attribute to stronger saturation of the gluon density in the nucleus than in the proton. In order to minimize model dependence of our predictions, we use two different extensions of the Balitsky-Kovchegov equation for evolution of the gluon density with subleading corrections.

We show that, besides the usual short distance contribution for $CP$ violation, final state interactions together with $CPT$ invariance can play an important role in the recent observation of $CP$ violation in three-body charmless $B^{\pm }$ decays. A significant part of the observed $CP$ asymmetry distribution in the Dalitz plot is located in a region where hadronic channels are strongly coupled. We illustrate our discussion comparing the recent observation of $CP$ violation in the $B^{\pm }\to K^{\pm }{K}^{+}{K}^{-}$ and $B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-}$ phase space, with a calculation based on $\pi \pi \to KK$ scattering.

Based on a sample of $(225.3\pm 2.8)\times 10^6$ $J/\psi$ events collected with the BESIII detector, the electromagnetic Dalitz decays of $J/\psi \to P{e}^{+}{e}^{-}(P={\eta }^{\prime }/\eta /{\pi }^0)$ are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays $J/\psi \to {\eta }^{\prime }{e}^{+}{e}^{-}$, $J/\psi \to \eta e^{+}{e}^{-}$, and $J/\psi \to {\pi }^0{e}^{+}{e}^{-}$ are observed for the first time. The branching fractions are determined to be $\mathcal{B}(J/\psi \to {\eta }^{\prime }{e}^{+}{e}^{-})=(5.81\pm 0.16\pm 0.31)\times 10^{-5}$, $\mathcal{B}(J/\psi \to \eta e^{+}{e}^{-})=(1.16\pm 0.07\pm 0.06)\times 10^{-5}$, and $\mathcal{B}(J/\psi \to {\pi }^0{e}^{+}{e}^{-})=(7.56\pm 1.32\pm 0.50)\times 10^{-7}$, where the first errors are statistical and the second ones systematic.

By numerical and analytical methods, we study in detail the effects of the Lifshitz dynamical exponent $z$ on the vector condensate induced by an applied magnetic field in the probe limit. Concretely, in the presence of the magnetic field, we obtain the Landau level independent of $z$, and we also find the critical value by coupling a Maxwell complex vector field and an SU(2) field into a ($3+1$)-dimensional Lifshitz black hole, respectively. The research results show that for the two models with the lowest Landau level, the increasing $z$ improves the response of the critical temperature to the applied magnetic field even without the charge density, and the analytical results uphold the numerical results. In addition, we find that, even in the Lifshitz black hole, the Maxwell complex vector model is still a generalization of the SU(2) Yang-Mills model. Furthermore, we construct the square vortex lattice and discuss the implications of these results.

We use a Yang-Mills field coupled to an axion as probes of a black hole with arbitrary Lifshitz scaling to investigate, via holography, superconducting phase transitions of the dual theory with a $⟨p_x+i{p}_y⟩$ condensate. In the relativistic case with no axion, this phase is known to be unstable, the stable phase corresponding to condensates of the $⟨p_x⟩$ form. We investigate this stability in theories with nonrelativistic scaling. Finally we numerically compute the “Hall” conductivity of these black holes in the nonsuperconducting phase as a function of their Lifshitz scaling.

Theories with dark forces and dark sectors are of interest for dark matter models. In this paper we find the region in parameter space that is constrained by supernova cooling constraints when the models include dark sector particles with masses around 100 MeV or less. We include only interactions with electrons and positrons. The constraint is important for small mixing parameters. We do not include in this work interactions with nucleons, which could give other important constraints.

In arbitrary dimensions, we consider a particular Horndeski action given by the Einstein-Hilbert Lagrangian with a cosmological constant term, while the source part is described by a real scalar field with its usual kinetic term together with a nonminimal kinetic coupling. In order to evade the no-hair theorem, we look for solutions where the radial component of the conserved current vanishes identically. Under this hypothesis, we prove that this model cannot accommodate Lifshitz solutions with a radial scalar field. This problem is finally circumvented by turning on the time dependence of the scalar field, and we obtain a Lifshitz black hole solution with a fixed value of the dynamical exponent $z=\frac{1}{3}$. The same metric is also shown to satisfy the field equations arising only from the variation of the matter source.

In this work, we analyze a gravity model with higher derivatives including a $CPT$-even Lorentz-violating term. In principle, the model could be a low-energy limit of a Lorentz-invariant theory presenting the violation of Lorentz symmetry as a consequence of a spontaneous symmetry-breaking mechanism if a decoupling between the metric and the Nambu-Goldstone modes is assumed. We have set up a convenient operator basis for the expansion of wave operators for symmetric second-rank tensors in the presence of a background vector. By using this set of operators, the particle content is obtained, and its consistency, regarding the conditions for stability and unitarity, is discussed. We conclude that this extra Lorentz noninvariant contribution is unable to address the problems of stability and unitarity of higher-derivative gravity models.

The cosmological birefringence caused by the coupling between the cosmic scalar field and the cosmic microwave background (CMB) photons through the Chern-Simons term can rotate the polarization planes of the photons and mix the CMB $E$-mode and $B$-mode polarizations. The rotation angle induced by the dynamical scalar field can be separated into the isotropic background part and the anisotropic fluctuations. The effect of the background part has been studied in our previous work (Zhao and Li, arXiv:1402.4324). In this paper, we focus on the influence of the anisotropies of the rotation angle. We first assume that the cosmic scalar field is massless, consistent with other works, and we find that the rotation spectrum can be quite large, which may be detected by the potential CMB observations. However, if the scalar field is identified as the quintessence field, by detailed discussion of both the entropy and adiabatic perturbation modes for the first time, we find that the anisotropies of the rotation angle are always too small to be detectable. In addition, as the main goal of this paper, we investigate the effect of a rotated polarization power spectrum on the detection of relic gravitational waves. We find that the rotated $B$-mode polarization could be fairly large and comparable with those generated by the gravitational waves. This forms a new contamination for the detection of relic gravitational waves in the CMB. In particular, we also propose the method to reconstruct and subtract the rotated $B$-mode polarization, by which the residuals become negligible for the gravitational-wave detection.

Probing the evolution of the universe at high redshifts with standard candles is a powerful way to discriminate dark energy models, where an open question nowadays is whether this component is constant or evolves with time. One possible source of ambiguity in this kind of analysis comes from cosmic opacity, which can mimic a dark energy behavior. However, most tests of cosmic opacity have been restricted to the redshift range $z<2$. In this work, by using luminosity distances of gamma-ray bursts, given the validity of the Amati relation, and the latest $H(z)$ data we determine constraints on the cosmic opacity at high redshifts ($z>2$) for a flat $\mathrm{\Lambda }\mathrm{CDM}$ model. A possible degeneracy of the results with the adopted cosmological model is also investigated by considering a flat XCDM model. The limits on cosmic opacity in the redshift range $0<z<2$ are updated with type Ia supernovae (SNe Ia) from the Union2.1 sample, where we added the most distant ($z=1.713$) spectroscopically confirmed SNe Ia. From the analyses performed, we find that both SNe Ia and gamma ray bursts samples are compatible with a transparent universe at $1\sigma$ level and the results are independent of the dark energy equation of state parameter $w$.

We examine the reach at hadron colliders for the lightest warped Kaluza-Klein graviton $G_1$ in the $Z(\to {\ell }^{+}{\ell }^{-})Z(\to \nu \overline{\nu })$ channel, $\ell =e$, $\mu$, within Randall-Sundrum models of hierarchy and flavor where the Standard Model gauge fields and fermions propagate in the 5D bulk. The reconstructed $Z$ and the accompanying large missing energy allow for an efficient suppression of backgrounds. For reasonable parameters, an $\sim 2(2.6)\mathrm{TeV}$ $G_1$ can be discovered at $5\sigma$ with $300{\mathrm{fb}}^{-1}(3{\mathrm{ab}}^{-1})$ of 14 TeV LHC data via our “$Z$ with missing energy” signal. Using this signal, the discovery reach for $G_1$ at a future 100 TeV $pp$ collider is estimated to be as high as $\sim 10\mathrm{TeV}$. We discuss mass determination of the singly produced $G_1$ using the energy distribution of its visible ($Z\to {\ell }^{+}{\ell }^{-}$) decay product by adapting a recently proposed method. Based on our analysis, a mass measurement at the $\sim 5\%$ level with $\sim 3{\mathrm{ab}}^{-1}$ of the 14 TeV LHC data can be feasible.

The heaviness of the top quark makes its two-body Cabibbo-favored decay mode $t\to b{W}^{+}$ to be dominant, at such a level that hardly any other decay mode reaches a detectable branching ratio within the Standard Model. Here we study the decay $t\to b{W}^{+}{\ell }^{-}{\ell }^{+}$ ($\ell =e,\mu ,\tau$), which diverges for massless leptons, and it can reach a branching ratio $\sim \mathcal{O}(10^{-5}\sim 10^{-6})$ for reasonable values of the low energy cut in the lepton pair invariant mass. This rate surpasses almost any other rare decays such as $t\to cX$ ($X=\gamma ,Z,g,H,W^{+}{W}^{-}$), and thus offers the possibility of being detectable. Furthermore, the estimate of this channel is relevant because it can mimic the signal arising from the lepton number violating decay $t\to b{W}^{-}{\ell }^{+}{\ell }^{+}$, when the $W$ boson decays into lepton channels.

We discuss the profile of the impact-parameter dependent elastic scattering amplitude. Extraction of impact-parameter dependence from the data set with inclusion of the experimental data on elastic scattering at the LHC energies helps to reveal the asymptotics of hadron interactions. Analysis of the data clearly indicates that the impact-parameter elastic scattering amplitude exceed the black disk limit at the LHC energy 7 TeV and the inelastic overlap function reaches its maximum value at $b>0$.

The first proof of well posedness of an initial boundary value problem for the Einstein equations was given in 1999 by Friedrich and Nagy. They used a frame formalism with a particular gauge for formulating the equations. This “Friedrich–Nagy” gauge has never been implemented for use in numerical simulations before because it was deemed too complicated. In this paper we present an implementation of the Friedrich–Nagy gauge for systems with two commuting spacelike Killing vectors. We investigate the numerical performance of this formulation for plane wave space-times, reproducing the well-known Khan–Penrose solution for colliding impulsive plane waves and exhibiting a gravitational wave “ping-pong.”