3,013 research outputs found
Quasinormal Modes of Charged Scalars around Dilaton Black Holes in 2+1 Dimensions: Exact Frequencies
We have studied the charged scalar perturbation around a dilaton black hole
in 2 +1 dimensions. The wave equations of a massless charged scalar field is
shown to be exactly solvable in terms of hypergeometric functions. The
quasinormal frequencies are computed exactly. The relation between the
quasinormal frequencies and the charge of the black hole, charge of the scalar
and the temperature of the black hole are analyzed. The asymptotic form of the
real part of the quasinormal frequencies are evaluated exactly.Comment: 20 pages and 7 figures, some references are added and some removed.
There are some changes to the text. arXiv admin note: text overlap with
arXiv:hep-th/040716
Symmetries of supergravity black holes
We investigate Killing tensors for various black hole solutions of
supergravity theories. Rotating black holes of an ungauged theory, toroidally
compactified heterotic supergravity, with NUT parameters and two U(1) gauge
fields are constructed. If both charges are set equal, then the solutions
simplify, and then there are concise expressions for rank-2 conformal
Killing-Stackel tensors. These are induced by rank-2 Killing-Stackel tensors of
a conformally related metric that possesses a separability structure. We
directly verify the separation of the Hamilton-Jacobi equation on this
conformally related metric, and of the null Hamilton-Jacobi and massless
Klein-Gordon equations on the "physical" metric. Similar results are found for
more general solutions; we mainly focus on those with certain charge
combinations equal in gauged supergravity, but also consider some other
solutions.Comment: 36 pages; v2: minor changes; v3: slightly shorte
Proper Motions and CCD-photometry of Stars in the Region of the Open Cluster Trumpler 2
The results of the complex study of galactic open cluster Trumpler 2 are
presented. In order to obtain the proper motions the positions of 2600 stars up
to the limit magnitude B ~ 16.25 mag in the area 80x80 arcmin around the
cluster were measured on 6 plates with the maximal epoch difference of 63
years. The root-mean error of the relative proper motions is 4.2 mas/yr. The
catalogue of BV magnitudes of all the stars in the investigated area was
compiled. Astrometric selection of the cluster members within the region of
R<16 arcmin from the center of the cluster was made by means of the W.Sanders
method. In that field 192 stars were found to have the individual membership
probability greater then 85%, 148 of them are situated within the
+/-3sigma_(B-V) band around the main sequence of the cluster. They are
considered to be cluster members by two criteria. The U-B ~ B-V diagram plotted
for the astrometrical cluster members by the data taken from the Washington
catalogue of the UBV photometry in the galactic cluster fields (Hoag et
al.1961) made it possible to redefine the value of the color excess E(B-V)=0.40
mag. The superposition of the MS of the cluster with the ZAMS Schmidt-Kaler
leads to the coincidence at the value of the apparent distance module
(V-Mv)=10.50 which corresponds to the distance r=725 pc. The luminosity and
mass functions of the Trumpler 2 were constructed and the value of the slope
Gamma=-1.90+/-0.22 was determined. The cluster age of 8.913x10^7 yr was
determined. It is shown that the red giant on the late stage of the evolution
(st N.1095) belongs to cluster and indicates the brightness variability. The
possibility that the number of both known and recently discovered variables are
cluster members was considered. Tables 2,3,3A,5 will be only available in the
electronic form.Comment: 14 pages, 7 figure
Plane torsion waves in quadratic gravitational theories
The definition of the Riemann-Cartan space of the plane wave type is given.
The condition under which the torsion plane waves exist is found. It is
expressed in the form of the restriction imposed on the coupling constants of
the 10-parametric quadratic gravitational Lagrangian. In the mathematical
appendix the formula for commutator of the variation operator and Hodge
operator is proved. This formula is applied for the variational procedure when
the gravitational field equations are obtained in terms of the exterior
differential forms.Comment: 3 May 1998. - 11
Supersymmetry of Tensionless Rotating Strings in AdS_5 x S^5, and Nearly-BPS Operators
It is shown that a class of rotating strings in AdS_5 x S^5 with SO(6)
angular momenta (J,J',J') preserve 1/8-supersymmetry for large J,J', in which
limit they are effectively tensionless; when J=0, supersymmetry is enhanced to
1/4. These results imply that recent checks of the AdS/CFT correspondence
actually test a nearly-BPS sector.Comment: 12 pages, no figures; v2: new section on CFT operators and new
references added, discussion section and acknowledgements modified, abstract
rephrashe
A note on spin chain/string duality
Recently a significant progress in matching the anomalous dimensions of
certain class of operators in N=4 SYM theory and rotating strings was made. The
correspondence was established mainly using Bethe ansatz technique applied to
the spin s Heisenberg model. In a recent paper Kruczenski (hep-th/0311203)
suggested to solve the Heisenberg model by using of sigme model approach. In
this paper we generalize the solutions obtained by Kruczenski and comment on
the dual string theory. It turns out that our solutions are related to the so
called Neumann-Rosochatius integrable system. We comment on the spin chain
solutions and on the string/gauge theory correspondence.Comment: v.2 One reference added, typos corrected, 21 page
- …