12,363 research outputs found

### Exact dynamical AdS black holes and wormholes with a Klein-Gordon field

We present several classes of exact solutions in the Einstein-Klein-Gordon
system with a cosmological constant. The spacetime has spherical, plane, or
hyperbolic symmetry and the higher-dimensional solutions are obtained in a
closed form only in the plane symmetric case. Among them, the class-I solution
represents an asymptotically locally anti-de Sitter (AdS) dynamical black hole
or wormhole. In four and higher dimensions, the generalized Misner-Sharp
quasi-local mass blows up at AdS infinity, inferring that the spacetime is only
locally AdS. In three dimensions, the scalar field becomes trivial and the
solution reduces to the BTZ black hole.Comment: 11 pages, 2 figures, 2 tables; v2, results strengthened, argument on
trapping horizon corrected; v3, argument on locally AdS property added,
accepted for publication in Physical Review

### Anti-de Sitter massless scalar field spacetimes in arbitrary dimensions

We consider $d$-dimensional static spacetimes in Einstein gravity with a
cosmological constant in the presence of a minimally coupled massless scalar
field. The spacetimes have a $(d-2)$-dimensional base manifold given by an
Einstein space and the massless scalar field depends only on the radial
coordinate. The field equations are decoupled in the general case, and can be
solved exactly for the cases when either the cosmological constant vanishes or
the base manifold is Ricci flat. We focus on the case of a negative
cosmological constant and a Ricci-flat base manifold. The solution has a
curvature singularity located at the origin, where also the scalar field
diverges. Since there is no event horizon surrounding this singularity, the
solution describes a naked singularity dressed with a nontrivial scalar field.
This spacetime is an asymptotically locally anti-de Sitter one when the
Ricci-flat base manifold is locally flat. The asymptotic solution for an
arbitrary Einstein base manifold is found and the corresponding mass,
calculated through the canonical generator of the time-translation invariance,
is shown to be finite. The contribution to the mass from the scalar field at
infinity is also discussed.Comment: 14 pages, 1 figure. Typos correcte

### Trapped ghosts: a new class of wormholes

We construct examples of static, spherically symmetric wormhole solutions in
general relativity with a minimally coupled scalar field $\phi$ whose kinetic
energy is negative in a restricted region of space near the throat (of
arbitrary size) and positive far from it. Thus in such configurations a "ghost"
is trapped in the strong-field region, which may in principle explain why no
ghosts are observed under usual conditions. Some properties of general wormhole
models with the $\phi$ field are revealed: it is shown that (i) trapped-ghost
wormholes are only possible with nonzero potentials $V(\phi)$; (ii) in twice
asymptotically flat wormholes, a nontrivial potential $V(\phi)$ has an
alternate sign, and (iii) a twice asymptotically flat wormhole which is
mirror-symmetric with respect to its throat has necessarily a zero
Schwarzschild mass at both asymptotics.Comment: 4.2 pages, 4 figures. Version to appear in CQ

### The application of the global isomorphism to the surface tension of the liquid-vapor interface of the Lennard-Jones fluids

In this communication we show that the surface tension of the real fluids of
the Lennard-Jones type can be obtained from the surface tension of the lattice
gas (Ising model) on the basis of the global isomorphism approach developed
earlier for the bulk properties.Comment: 8 pages, 6 figure

### Self-force of a point charge in the space-time of a massive wormhole

We consider the self-potential and the self-force for an electrically charged
particle at rest in the massive wormhole space-time. We develop general
approach for the renormalization of electromagnetic field of such particle in
the static space-times and apply it to the space-time of the wormhole with
parameter of the mass, $m$. The self-force is found in manifest form; it is an
attractive force. We discus the peculiarities due to massive parameter of the
wormhole.Comment: 10 pages, 1 figure text correcte

### A naked singularity stable under scalar field perturbations

We prove the stability of a spacetime with a naked singularity under scalar
field perturbations, where the perturbations are regular at the singularity.
This spacetime, found by Janis, Newman and Winicour, and independently by
Wyman, is sourced by a massless scalar field and also arises as a certain limit
of a class of charged dilatonic solutions in string theory. This stability
result opens up specific questions for investigation related to the cosmic
censorship conjecture and the mechanism by which it is implemented in nature.Comment: 19 pages, version to appear in IJMPD, references adde

### Reaction-diffusion fronts with inhomogeneous initial conditions

Properties of reaction zones resulting from A+B -> C type reaction-diffusion
processes are investigated by analytical and numerical methods. The reagents A
and B are separated initially and, in addition, there is an initial macroscopic
inhomogeneity in the distribution of the B species. For simple two-dimensional
geometries, exact analytical results are presented for the time-evolution of
the geometric shape of the front. We also show using cellular automata
simulations that the fluctuations can be neglected both in the shape and in the
width of the front.Comment: 11 pages, 3 figures, submitted to J. Phys.

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