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Introducing a new form of scalar potential V(ɸ), we derive a proper form of the rotating black hole solution in three-dimensional Einstein gravity with nonminimally coupled scalar field and find that the first law of thermodynamics of this new rotating hairy black hole can be protected, where the scalar field parameter B is constrained to relate to the black hole size. We also disclose the Hawking-Page phase transition between this rotating hairy black holes and the pure thermal radiation. Moreover, we study phase transitions between this rotating hairy black hole and rotating Banados-Teitelboim-Zanelli (BTZ) black hole. Considering the matchings for the temperature and angular momentum, we find that the rotating BTZ black hole always has smaller free energy, which is a thermodynamically more preferred phase. Additionally, we evaluate the thermodynamics of the rotating black hole with minimally coupled scalar hair in three dimensions, which exhibits that the thermodynamical behaviors of this rotating hairy black hole are very similar to those of the rotating black hole with nonminimally coupled scalar hair. [ABSTRACT FROM AUTHOR]

We study the thermodynamics in the grand canonical ensemble of D-dimensional charged Gauss-Bonnet-AdS black holes in the extended phase space. We find that the usual small-large black hole phase transition, which exhibits analogy with the van der Waals liquid-gas system, holds in five-dimensional spherical charged Gauss-Bonnet-AdS black holes when its potential is fixed within the range 0 < Φ < 3 √π/4. For the other higher dimensional and topological charged Gauss-Bonnet-AdS black holes, there is no such phase transition. In the limiting case, Reissner-Nordstrom AdS black holes, with vanishing Gauss-Bonnet parameter, there is no critical behavior in the grand canonical ensemble. This result holds independent of the spacetime dimensions and topologies. We also examine the behavior of physical quantities in the vicinity of the critical point in the five-dimensional spherical charged Gauss-Bonnet-AdS black holes. [ABSTRACT FROM AUTHOR]

We discuss the (2+1)-dimensional parity violating charged fluid on a finite cutoff surface Sc, dual to the nondynamical and dynamical Chern-Simons (CS) modified gravities. Using nonrelativistic long-wavelength expansion method, the field equations are solved up to O(ε²) in the nondynamical model. It is shown that there exists nonvortical dual fluid with shear viscosity ? and Hall viscosity ?A on the cutoff surface Sc. The ratio of shear viscosity over entropy density ?/s of the fluid takes the universal value 1/4p, while the ratio of Hall viscosity over entropy density ?A/s depends on the Sc and black brane charge q. Moreover the nonvortical dual fluid obeys the magnetohydrodynamic (MHD) equation. However, these kinematic viscosities ? and ?A related to ? and ?A do not appear in this MHD equation, due to the constraint condition ?~2ßj=0 for the (2+1)-dimensional dual fluid. Then, we extend our discussion to the dynamical CS modified gravity and show that the dual vortical fluid possesses another so-called Curl viscosity ?A, whose ratio to entropy density ?A/s also depends on the Sc and q. Moreover, the value of ?/s still equals to 1/4p and the result of ?A/s agrees to the previous result under the probe limit of the pseudo scalar field at the infinite boundary in the charged black brane background for the dynamical CS modified gravity. This vortical dual fluid corresponds to the magnetohydrodynamic (MHD) turbulence equation in plasma physics. [ABSTRACT FROM AUTHOR]

We investigate the quasinormal mode of the perturbation of the scalar field interacting with the electromagnetic field in the backgrounds of neutral AdS black hole, the Reissner-Nordstrom AdS black hole, and the Born-Infeld AdS black hole. We study the influence of the electric charge Q, the coupling q between electromagnetic and scalar field, and the Born-Infeld parameter h on the quasinormal frequencies of the scalar perturbations. We observe the possible growing mode when the perturbation of the scalar field strongly couples to the electromagnetic field. When the electromagnetic field becomes nonlinear described by the Born-Infeld electrodynamics, the nonlinearity described by the Born-Infeld parameter can hinder the instability to happen in the scalar perturbation. The quasinormal behavior of the scalar field perturbation can help us further understand the physics in the holographic superconductor. [ABSTRACT FROM AUTHOR]

In this work, we present a numerical scheme to study the quasinormal modes of the time-dependent Vaidya black hole metric in asymptotically anti-de Sitter spacetime. The proposed algorithm is primarily based on a generalized matrix method for quasinormal modes. The main feature of the present approach is that the quasinormal frequency, as a function of time, is obtained by a generalized secular equation and therefore a satisfactory degree of precision is achieved. The implications of the results are discussed. [ABSTRACT FROM AUTHOR]

Observations indicate that large-scale anomalies exist in the fluctuations of the cosmic microwave background. In these anomalies, the hemispherical power amplitude asymmetry has a correlation length comparable to that of the observable universe. We propose that a topological defect created by spontaneous breaking of the U(1) symmetry prior to inflation generated an initial phase variation, δζ, across the observable region of the universe. The amplitude of this phase fluctuation is protected by topology if the defect is inside the horizon, and is frozen by causality if the defect exits the horizon. After inflation, the phase-corresponding boson field started to oscillate, when the Hubble rate decreased to a level comparable to the mass of the boson field. The energy density of the newly created boson particles varied across the observable universe. The bosons subsequently decayed into radiation prior to the big bang nucleosynthesis epoch, and the resulting fluctuations in the energy density produced the observed power asymmetry. This scenario predicts a scale-dependent modulation amplitude power asymmetry and in addition, as topological defects created by phase transitions are a very general phenomenon, the observed hemispherical asymmetry may be seen as an evidence for the cosmological inflation. [ABSTRACT FROM AUTHOR]

We study the gravity duals of supercurrent solutions in the anti-de Sitter (AdS) black hole background with general phase structure to describe both the first- and the second-order phase transitions at finite temperature in strongly interacting systems. We argue that the conductivity and the pair susceptibility can be possible phenomenological indications to distinguish the order of phase transitions. We extend our discussion to the AdS soliton configuration. Different from the black hole spacetime, in the probe limit, the first-order phase transition cannot be brought by introducing the spatial component of the vector potential of the gauge field in the AdS soliton background. [ABSTRACT FROM AUTHOR]

We study the process of fully nonlinear dynamical scalarization starting from a charged black hole or a naked singularity in asymptotically flat spacetime in the Einstein-Maxwell-dilaton theory. Initially, the dilaton field is negligible compared to the gravitational and the Maxwell field. Then the dilaton field experiences an immediate growth, later it oscillates with damping amplitude and finally settles down to a finite value. For a hairy black hole that develops from an original Reissner-Nordström black hole, since the dilaton oscillation and decay are almost independent of the coupling parameter, unlike the anti-de Sitter spacetime it is not easy to distinguish the resulting hairy black hole from the original asymptotically flat charged hole. For a hairy black hole evolves from an original naked singularity, the resulting hairy black hole has rich structures. In the scalarization process, the naked singularity is soon enveloped by one outer horizon, then another horizon is developed and in the end, a stable hairy black hole forms and two horizons degenerate into one protecting the singularity. The hairy black hole mass saturates exponentially in the scalarization. [ABSTRACT FROM AUTHOR]

We study the nonlinear evolution of the spherical symmetric charged black holes under a small neutral scalar field perturbation in Einstein-Maxwell-dilaton theory with coupling function f(ϕ)=e-bϕ in asymptotic anti-de Sitter spacetime. The nonminimal coupling between scalar and Maxwell fields allows the transmission of the energy from the Maxwell field to the scalar field, but also behaves as a repulsive force for the scalar. The scalar field oscillates with damping amplitude and converges to a final value. The irreducible mass of the black hole increases abruptly at initial times and then saturates to the final value exponentially. The saturating rate is twice the decaying rate of the dominant mode of the scalar. The effects of the black hole charge, the cosmological constant, and the coupling parameter on the evolution are studied in detail. When the initial configuration is a naked singularity spacetime with a large charge to mass ratio, a horizon will form soon and hide the singularity. [ABSTRACT FROM AUTHOR]

Gravitational wave echoes from black holes have been suggested as a crucial observable to probe the spacetime in the vicinity of the horizon. In particular, it was speculated that the echoes are closely connected with specific characteristics of the exotic compact objects, and moreover, possibly provide an access to the quantum nature of gravity. Recently, it was shown that the discontinuity in the black hole metric substantially modifies the asymptotical behavior of quasinormal frequencies. In the present study, we proceed further and argue that a discontinuity planted into the metric furnishes an alternative mechanism for the black hole echoes. Physically, the latter may correspond to an uneven matter distribution inside the surrounding halo. To demonstrate the results, we first numerically investigate the temporal evolution of the scalar perturbations around a black hole that possesses a nonsmooth effective potential. It is shown that the phenomenon persists even though the discontinuity can be located further away from the horizon with rather insignificant strength. Besides, we show that the echoes in the present model can be derived analytically based on the modified pole structure of the associated Green function. The asymptotical properties of the quasinormal mode spectrum and the echoes are found to be closely connected, as both features can be attributed to the same origin. In particular, the period of the echoes in the time domain T is shown to be related to the asymptotic spacing between successive poles along the real axis in the frequency domain Δ(Rω) by a simple relation limRω→+∞Δ(Rω)=2π/T. Moreover, we discuss possible distinguishment between different echo mechanisms. The potential astrophysical implications of the present findings are also addressed. [ABSTRACT FROM AUTHOR]

We study the time evolution of the test scalar and electromagnetic fields perturbations in configurations of phantom wormholes surrounded by dark energy with state parameter < - 1. We observe obvious signals of echoes reflecting wormholes properties and disclose the physical reasons behind such phenomena. In particular, we find that the dark energy equation of state has a clear imprint in echoes in wave perturbations. When approaches the phantom divide = - 1 from below, the delay time of echoes becomes longer. The echo of gravitational wave is likely to be detected in the near future, and the signature of the dark energy equation of state in the echo spectrum can serve as a local measurement of the dark energy. [ABSTRACT FROM AUTHOR]

We point out that there are only three polarizations for gravitational waves in f(R) gravity, and the polarization due to the massive scalar mode is a mix of the pure longitudinal and transverse breathing polarization. The classification of the six polarizations by the Newman-Penrose quantities is based on weak, plane and null gravitational waves, so it is not applicable to the massive mode. [ABSTRACT FROM AUTHOR]