9,134 research outputs found
Ba Quadrupole Polarizabilities: Theory versus Experiment
Three different measurements have been reported for the ground state
quadrupole polarizability in the singly ionized barium (Ba) which disagree
with each other. Our calculation of this quantity using the relativistic
coupled-cluster method disagrees with two of the experimental values and is
within the error bars of the other. We discuss the issues related to the
accuracy of our calculations and emphasize the need for further experiments to
measure the quadrupole polarizability for this state and/or the 5D states.Comment: 6 pages, 3 table
On the Entropy Function and the Attractor Mechanism for Spherically Symmetric Extremal Black Holes
In this paper we elaborate on the relation between the entropy formula of
Wald and the "entropy function" method proposed by A. Sen. For spherically
symmetric extremal black holes, it is shown that the expression of extremal
black hole entropy given by A. Sen can be derived from the general entropy
definition of Wald, without help of the treatment of rescaling the AdS_2 part
of near horizon geometry of extremal black holes. In our procedure, we only
require that the surface gravity approaches to zero, and it is easy to
understand the Legendre transformation of f, the integration of Lagrangian
density on the horizon, with respect to the electric charges. Since the Noether
charge form can be defined in an "off-shell" form, we define a corresponding
entropy function, with which one can discuss the attractor mechanism for
extremal black holes with scalar fields.Comment: v3: Revtex4, 19 pages, discussion added, mistakes corrected, final
version; to appear in Phys. Rev.
The world-sheet corrections to dyons in the Heterotic theory
All the linear alpha-prime corrections, however excluding the gravitational
Chern-Simons correction, are studied in the toroidally compactified critical
Heterotic string theory. These corrections are computed to the entropy for a
BPS static spherical four dimensional dyonic black hole which represents a
wrapped fundamental string carrying arbitrary winding and momentum charges
along one cycle in the presence of KK-monopole and H-monopole charges
associated to another cycle. It is verified that after the inclusion of the
gravitational Chern-Simons corrections [hep-th/0608182], all the linear
alpha-prime corrections to the entropy for the supersymmetric dyon can be
reproduced by the inclusion of only the Gauss-Bonnet Lagrangian to the
supergravity approximation of the induced Lagrangian.Comment: JHEP style, 17 Pages; v2: a typo corrected ; v3: The coupling of the
gravitational Chern-Simons terms to the three form field strength taken into
account. The conclusion correcte
Non-supersymmetric Attractors in Born-Infeld Black Holes with a Cosmological Constant
We investigate the attractor mechanism for spherically symmetric extremal
black holes in Einstein-Born-Infeld-dilaton theory of gravity in
four-dimensions, in the presence of a cosmological constant. We look for
solutions analytic near the horizon by using perturbation method. It is shown
that the values of the scalar fields at the horizon are only dependent on the
charges carried by the black hole and are irrelevant in their asymptotic
values. This analysis supports the validity of non-supersymmetric attractors in
the presence of higher derivative interactions in the gauge fields part and in
non-asymptotically flat spacetime.Comment: 18 pages, no figu
Entropy Function for Non-Extremal Black Holes in String Theory
We generalize the entropy function formalism to five-dimensional and
four-dimensional non-extremal black holes in string theory. In the near horizon
limit, these black holes have BTZ metric as part of the spacetime geometry. It
is shown that the entropy function formalism also works very well for these
non-extremal black holes and it can reproduce the Bekenstein-Hawking entropy of
these black holes in ten dimensions and lower dimensions.Comment: 19 pages, no figure, JHEP3 style, to appear in JHE
Non-Supersymmetric Attractor Flow in Symmetric Spaces
We derive extremal black hole solutions for a variety of four dimensional
models which, after Kaluza-Klein reduction, admit a description in terms of 3D
gravity coupled to a sigma model with symmetric target space. The solutions are
in correspondence with certain nilpotent generators of the isometry group. In
particular, we provide the exact solution for a non-BPS black hole with generic
charges and asymptotic moduli in N=2 supergravity coupled to one vector
multiplet. Multi-centered solutions can also be generated with this technique.
It is shown that the non-supersymmetric solutions lack the intricate moduli
space of bound configurations that are typical of the supersymmetric case.Comment: 50 pages, 4 figures; v2: Reference added. To appear in JHE
Comparative studies of dipole polarizabilities in Sr, Ba and Ra and their applications to optical clocks
Static dipole polarizabilities are calculated in the ground and metastable
states of Sr, Ba and Ra using the relativistic coupled-cluster
method. Trends of the electron correlation effects are investigated in these
atomic ions. We also estimate the Stark and black-body radiation shifts from
these results for these systems for the transitions proposed for the optical
frequency standards and compare them with available experimental data.Comment: 10 pages, 1 figur
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