15,726 research outputs found
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(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
Time Delay Induced Death in Coupled Limit Cycle Oscillators
We investigate the dynamical behaviour of two limit cycle oscillators that
interact with each other via time delayed coupling and find that time delay can
lead to amplitude death of the oscillators even if they have the same
frequency. We demonstrate that this novel regime of amplitude "death" also
exists for large collections of coupled identical oscillators and provide
quantitative measures of this death region in the parameter space of coupling
strength and time delay. Its implication for certain biological and physical
applications is also pointed out.Comment: 4 aps formatted revtex pages; 3 figures; to be published in Phys.
Rev. Let
Solitons on compact and noncompact spaces in large noncommutativity
We study solutions at the minima of scalar field potentials for Moyal spaces
and torii in the large non-commutativity and interprete these solitons in terms
of non-BPS D-branes of string theory. We derive a mass spectrum formula linking
different D-branes together on quantum torii and suggest that it describes
general systems of D-brane bound states extending the D2-D0 one. Then we
propose a shape for the effective potential approaching these quasi-stable
bound states. We give the gauge symmetries of these systems of branes and show
that they depend on the quantum torii representations.Comment: 25 pages, Latex, 1 figure (use epsfig.sty), corrected formul
Kramer--Neugebauer Transformation for Einstein--Maxwell--Dilaton--Axion Theory
The Kramer--Neugebauer--like transformation is constructed for the stationary
axisymmetric D=4 Einstein--Maxwell--dilaton--axion system. This transformation
directly maps the dualized sigma--model equations of the theory into the
nondualized ones. Also the new chiral matrix representation of the
problem is presented.Comment: 13 pages, RevTex, no figure
Bulk Kalb-Ramond field in Randall Sundrum scenario
We have considered the most general gauge invariant five-dimensional action
of a second rank antisymmetric Kalb-Ramond tensor gauge theory, including a
topological term of the form in a
Randall-Sundrum scenario. Such a tensor field (whose rank-3 field
strength tensor is ), which appears in the massless sector of a
heterotic string theory, is assumed to coexist with the gravity in the bulk.
The third rank field strength corresponding to the Kalb-Ramond field has a
well-known geometric interpretation as the spacetime torsion. The only
non-trivial classical solutions corresponding to the effective four-dimensional
action are found to be self-dual or anti-selfdual Kalb-Ramond fields. This
ensures that the four-dimensional effective action on the brane is
parity-conserving. The massive modes for both cases, lying in the TeV range,
are related to the fundamental parameters of the theory. These modes can be
within the kinematic reach of forthcoming TeV scale experiments. However, the
couplings of the massless as well as massive Kalb-Ramond modes with matter on
the visible brane are found to be suppressed vis-a-vis that of the graviton by
the warp factor, whence the conclusion is that both the massless and the
massive torsion modes appear much weaker than curvature to an observer on the
visible brane.Comment: 15 Pages,2 figures,Late
Exact Black Hole Degeneracies and the Topological String
Motivated by the recent conjecture of Ooguri, Strominger and Vafa, we compute
the semi-canonical partition function of BPS black holes in N=4 and N=8 string
theories, to all orders in perturbation theory. Not only are the black hole
partition functions surprisingly simple; they capture the full topological
string amplitudes, as expected from the OSV conjecture. The agreement is not
perfect, however, as there are differences between the black hole and
topological string partition functions even at the perturbative level. We
propose a minimal modification of the OSV conjecture, in which these
differences are understood as a nontrivial measure factor for the topological
string.Comment: 24 page
Black Hole Entropy Function and the Attractor Mechanism in Higher Derivative Gravity
We study extremal black hole solutions in D dimensions with near horizon
geometry AdS_2\times S^{D-2} in higher derivative gravity coupled to other
scalar, vector and anti-symmetric tensor fields. We define an entropy function
by integrating the Lagrangian density over S^{D-2} for a general AdS_2\times
S^{D-2} background, taking the Legendre transform of the resulting function
with respect to the parameters labelling the electric fields, and multiplying
the result by a factor of 2\pi. We show that the values of the scalar fields at
the horizon as well as the sizes of AdS_2 and S^{D-2} are determined by
extremizing this entropy function with respect to the corresponding parameters,
and the entropy of the black hole is given by the value of the entropy function
at this extremum. Our analysis relies on the analysis of the equations of
motion and does not directly make use of supersymmetry or specific structure of
the higher derivative terms.Comment: LaTeX file, 12page
Entropy Function for Heterotic Black Holes
We use the entropy function formalism to study the effect of the Gauss-Bonnet
term on the entropy of spherically symmetric extremal black holes in heterotic
string theory in four dimensions. Surprisingly the resulting entropy and the
near horizon metric, gauge field strengths and the axion-dilaton field are
identical to those obtained by Cardoso et. al. for a supersymmetric version of
the theory that contains Weyl tensor squared term instead of the Gauss-Bonnet
term. We also study the effect of holomorphic anomaly on the entropy using our
formalism. Again the resulting attractor equations for the axion-dilaton field
and the black hole entropy agree with the corresponding equations for the
supersymmetric version of the theory. These results suggest that there might be
a simpler description of supergravity with curvature squared terms in which we
supersymmetrize the Gauss-Bonnet term instead of the Weyl tensor squared term.Comment: LaTeX file, 23 pages; v2: references added; v3: minor addition; v4:
minor change
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