65 research outputs found
Dirac Monopoles in the Ernst--Schwarzschild Spacetime
It is discussed that the Ernst--Schwarzschild metric describing a nonrotating
black hole in the external magnetic field admits the solutions of the Dirac
monopole types for the corresponding Maxwell equations. The given solutions are
obtained in explicit form and a possible influence of the conforming Dirac
monopoles on Hawking radiation is also outlined.Comment: Int. Journal of Modern Physics A, vol. 18 (2003), 2153-215
U(1,1)--Invariant Generation of Charges for Einstein--Maxwell--Dilaton--Axion Theory
The action of the isometry subgroup which preserves the trivial values of the
fields is studied for the stationary D=4 Einstein--Maxwell--Dilaton--Axion
theory. The technique for generation of charges and the corresponding procedure
for construction of new solutions is formulated. A solution describing the
double rotating dyon with independent values of all physical charges is
presented.Comment: 14 pages, RevTex, no figurie
Inverse dualisation and non-local dualities between Einstein gravity and supergravities
We investigate non-local dualities between suitably compactified
higher-dimensional Einstein gravity and supergravities which can be revealed if
one reinterprets the dualised Kaluza-Klein two-forms in as antisymmetric
forms belonging to supergravities. We find several examples of such a
correspondence including one between the six-dimensional Einstein gravity and
the four-dimensional Einstein-Maxwell-dilaton-axion theory (truncated N=4
supergravity), and others between the compactified eleven and ten-dimensional
supergravities and the eight or ten-dimensional pure gravity. The Killing
spinor equation of the D=11 supergravity is shown to be equivalent to the
geometric Killing spinor equation in the dual gravity. We give several examples
of using new dualities for solution generation and demonstrate how -branes
can be interpreted as non-local duals of pure gravity solutions. New
supersymmetric solutions are presented including -brane with two
rotation parameters.Comment: 32 pages, Late
Classical glueballs in non-Abelian Born-Infeld theory
It is shown that the Born-Infeld-type modification of the quadratic
Yang-Mills action suggested by the superstring theory gives rise to classical
particle-like solutions prohibited in the standard Yang-Mills theory. This
becomes possible due to the scale invariance breaking by the Born-Infeld
non-linearity. New classical glueballs are sphaleronic in nature and exhibit a
striking similarity with the Bartnik-McKinnon solutions of the Yang-Mills
theory coupled to gravity.Comment: Revtex, 4 pages, 2 eps figure
Integrable Systems in Stringy Gravity
Static axisymmetric Einstein-Maxwell-Dilaton and stationary axisymmetric
Einstein-Maxwell-Dilaton-Axion (EMDA) theories in four space-time dimensions
are shown to be integrable by means of the inverse scattering transform method.
The proof is based on the coset-space representation of the 4-dim theory in a
space-time admitting a Killing vector field. Hidden symmetry group of the
four-dimensional EMDA theory, unifying T and S string dualities, is shown to be
Sp(2, R) acting transitively on the coset Sp(2, R)/U(2). In the case of
two-parameter Abelian space-time isometry group, the hidden symmetry is the
corresponding infinite-dimensional group of the Geroch-Kinnersley-Chitre type.Comment: 8 pages, LATEX, MSU-DTP-94/21, October 9
Soliton solution in dilaton-Maxwell gravity
The inverse scattering problem method application to construction of exact
solution for Maxwell dilaton gravity system ia considered. By use of Belinsky
and Zakharov L - A pair the solution of the theory is constructed. The rotating
Kerr - like configuration with NUT - parameter is obtained.Comment: 8 pages in LaTex; published in Gen. Rel. Grav. pp. 32 (2000)
2219-222
U-Duality and Symplectic Formulation of Dilaton-Axion Gravity
We study a bosonic four--dimensional effective action corresponding to the
heterotic string compactified on a 6--torus (dilaton--axion gravity with one
vector field) on a curved space--time manifold possessing a time--like Killing
vector field. Previously an existence of the global
symmetry (--duality) as well as the symmetric space property of the
corresponding --model have been established following Neugebauer and
Kramer approach. Here we present an explicit form of the generators
in terms of coset variables and construct a representation of the coset in
terms of the physical target space coordinates. Complex symmetric
matrix (``matrix dilaton --axion'') is introduced for which --duality
takes the matrix valued form. In terms of this matrix the theory is
further presented as a K\"ahler --model. This leads to a more concise
formulation which opens new ways to construct exact classical
solutions. New solution (corresponding to constant ) is obtained
which describes the system of point massless magnetic monopoles endowed with
axion charges equal to minus monopole charges. In such a system mutual magnetic
repulsion is exactly balanced by axion attraction so that the resulting space
time is locally flat but possesses multiple Taub--NUT singularities.Comment: LATEX, 20 pages, no figure
Stationary BPS solutions to dilaton-axion gravity
Stationary four-dimensional BPS solutions to gravity coupled bosonic theories
admitting a three-dimensional sigma-model representation on coset spaces are
interpreted as null geodesics of the target manifold equipped with a certain
number of harmonic maps. For asymptotically flat (or Taub-NUT) space-times such
geodesics can be directly parametrized in terms of charges saturating the
Bogomol'nyi-Gibbons-Hull bound, and classified according to the structure of
related coset matrices. We investigate in detail the ``dilaton-axion gravity''
with one vector field, and show that in the space of BPS solutions an classical symmetry is acting. Within the present formalism the
most general multicenter (IWP/Taub-NUT dyon) solutions are derived in a simple
way. We also discover a large new class of asymptotically flat solutions for
which the dilaton and axion charges are constrained only by the BPS bound. The
string metrics for these solutions are generically regular. Both the IWP class
and the new class contain massless solutions.Comment: 29 pages, Latex, no figures. To be published in Phys. Rev. D. Minor
grammatical and bibliographical change
Internal Structure of Einstein-Yang-Mills Black Holes
It is shown that a generic black hole solution of the SU(2)
Einstein-Yang-Mills equations develops a new type of an infinitely oscillating
behavior near the singularity. Only for certain discrete values of the event
horizon radius exceptional solutions exist, possessing an inner structure of
the Schwarzschild or Reissner-Nordstrom type.Comment: 4.5 LaTeX pages, 8 eps figures, uses RevTeX, boxedeps.tex. 4 more
typos fixed, a footnote adde
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