29 research outputs found
Dilaton Black Holes with Electric Charge
Static spherically symmetric solutions of the Einstein-Maxwell gravity with
the dilaton field are described. The solutions correspond to black holes and
are generalizations of the previously known dilaton black hole solution. In
addition to mass and electric charge these solutions are labeled by a new
parameter, the dilaton charge of the black hole. Different effects of the
dilaton charge on the geometry of space-time of such black holes are studied.
It is shown that in most cases the scalar curvature is divergent at the
horizons. Another feature of the dilaton black hole is that there is a finite
interval of values of electric charge for which no black hole can exist.Comment: 20 pages, LaTeX file + 1 figure, CALT-68-1885. (the postscript file
is improved
Dynamical Compactification, Standard Cosmology and the Accelerating Universe
A cosmological model based on Kaluza-Klein theory is studied. A metric, in
which the scale factor of the compact space evolves as an inverse power of the
radius of the observable universe, is constructed. The
Freedmann-Robertson-Walker equations of standard four-dimensional cosmology are
obtained precisely. The pressure in our universe is an effective pressure
expressed in terms of the components of the higher dimensional energy-momentum
tensor. In particular, this effective pressure could be negative and might
therefore explain the acceleration of our present universe. A special feature
of this model is that, for a suitable choice of the parameters of the metric,
the higher dimensional gravitational coupling constant could be negative.Comment: 11 pages, uses revte
Supersymmetric Moyal-Lax Representations
The super Moyal-Lax representation and the super Moyal momentum algebra are
introduced and the properties of simple and extended supersymmetric integrable
models are systematically investigated. It is shown that, much like in the
bosonic cases, the super Moyal-Lax equation can be interpreted as a Hamiltonian
equation and can be derived from an action. Similarly, we show that the
parameter of non-commutativity, in this case, is related to the central charge
of the second Hamiltonian structure of the system. The super Moyal-Lax
description allows us to go to the dispersionless limit of these models in a
singular limit and we discuss some of the properties of such systems.Comment: 16 page
General analysis of self-dual solutions for the Einstein-Maxwell-Chern-Simons theory in (1+2) dimensions
The solutions of the Einstein-Maxwell-Chern-Simons theory are studied in
(1+2) dimensions with the self-duality condition imposed on the Maxwell field.
We give a closed form of the general solution which is determined by a single
function having the physical meaning of the quasilocal angular momentum of the
solution. This function completely determines the geometry of spacetime, also
providing the direct computation of the conserved total mass and angular
momentum of the configurations.Comment: 3 pages, REVTEX file, no figure
Multidimensional integrable vacuum cosmology with two curvatures
The vacuum cosmological model on the manifold describing the evolution of Einstein spaces of non-zero
curvatures is considered. For the Einstein equations are reduced to the
Abel (ordinary differential) equation and solved, when dim dim. The Kasner-like behaviour of the
solutions near the singularity is considered ( is synchronous
time). The exceptional ("Milne-type") solutions are obtained for arbitrary .
For these solutions are attractors for other ones, when . For dim and certain two-parametric
families of solutions are obtained from ones using "curvature-splitting"
trick. In the case , a family of non-singular
solutions with the topology is found.Comment: 21 pages, LaTex. 5 figures are available upon request (hard copy).
Submitted to Classical and Quantum Gravit
No Black Hole Theorem in Three-Dimensional Gravity
A common property of known black hole solutions in (2+1)-dimensional gravity
is that they require a negative cosmological constant. In this letter, it is
shown that a (2+1)-dimensional gravity theory which satisfies the dominant
energy condition forbids the existence of a black hole to explain the above
situation.Comment: 3 pages, no figures, to be published in Physical Review Letter
Integration of D-dimensional 2-factor spaces cosmological models by reducing to the generalized Emden-Fowler equation
The D-dimensional cosmological model on the manifold describing the evolution of 2 Einsteinian factor spaces,
and , in the presence of multicomponent perfect fluid source is
considered. The barotropic equation of state for mass-energy densities and the
pressures of the components is assumed in each space. When the number of the
non Ricci-flat factor spaces and the number of the perfect fluid components are
both equal to 2, the Einstein equations for the model are reduced to the
generalized Emden-Fowler (second-order ordinary differential) equation, which
has been recently investigated by Zaitsev and Polyanin within discrete-group
analysis. Using the integrable classes of this equation one generates the
integrable cosmological models. The corresponding metrics are presented. The
method is demonstrated for the special model with Ricci-flat spaces
and the 2-component perfect fluid source.Comment: LaTeX file, no figure
Toda chains with type A_m Lie algebra for multidimensional m-component perfect fluid cosmology
We consider a D-dimensional cosmological model describing an evolution of
Ricci-flat factor spaces, M_1,...M_n (n > 2), in the presence of an m-component
perfect fluid source (n > m > 1). We find characteristic vectors, related to
the matter constants in the barotropic equations of state for fluid components
of all factor spaces.
We show that, in the case where we can interpret these vectors as the root
vectors of a Lie algebra of Cartan type A_m=sl(m+1,C), the model reduces to the
classical open m-body Toda chain.
Using an elegant technique by Anderson (J. Math. Phys. 37 (1996) 1349) for
solving this system, we integrate the Einstein equations for the model and
present the metric in a Kasner-like form.Comment: LaTeX, 2 ps figure
Einstein-Yang-Mills Theory with a Massive Dilaton and Axion: String-Inspired Regular and Black Hole Solutions
We study the classical theory of a non-Abelian gauge field (gauge group
) coupled to a massive dilaton, massive axion and Einstein gravity. The
theory is inspired by the bosonic part of the low-energy heterotic string
action for a general Yang-Mills field, which we consider to leading order after
compactification to dimensions. We impose the condition that spacetime
be static and spherically symmetric, and we introduce masses via a
dilaton-axion potential associated with supersymmetry (SUSY)-breaking by
gaugino condensation in the hidden sector. In the course of describing the
possible non-Abelian solutions of the simplified theory, we consider in detail
two candidates: a massive dilaton coupled to a purely magnetic Yang-Mills
field, and a massive axion field coupled to a non-Abelian dyonic configuration,
in which the electric and magnetic fields decay too rapidly to correspond to
any global gauge charge. We discuss the feasibility of solutions with and
without a nontrivial dilaton for the latter case, and present numerical regular
and black hole solutions for the former.Comment: 44 page