377 research outputs found
Supersymmetry and the Systematics of T-duality Rotations in Type-II Superstring Theories
We describe a systematic method of studying the action of the T-duality group
O(d,d) on space-time fermions and R-R field strengths and potentials in type-II
string theories, based on space-time supersymmetry. The formalism is then used
to show that the couplings of non-Abelian D-brane charges to R-R potentials can
be described by an appropriate Clifford multiplication.Comment: 6 pages, LaTeX, uses espcrc2.sty; Contribution to the proceedings of
the D. V. Volkov memorial conference on ``Supersymmetry and Quantum Field
Theory'', Kharkov, July 25-29, 2000 (to appear in the Nucl. Phys. B
Conference Supplements
T-Duality, Space-time Spinors and R-R Fields in Curved Backgrounds
We obtain the T-duality transformations of space-time spinors (the
supersymmetry transformation parameters, gravitinos and dilatinos) of type-II
theories in curved backgrounds with an isometry. The transformation of the
spinor index is shown to be a consequence of the twist that T-duality
introduces between the left and right-moving local Lorentz frames. The result
is then used to derive the T-duality action on Ramond-Ramond field strengths
and potentials in a simple way. We also discuss the massive IIA theory and,
using duality, give a short derivation of ``mass''-dependent terms in the
Wess-Zumino actions on the D-brane worldvolumes.Comment: 19 pages, LaTeX; (V3): typos corrected and minor comments added (to
appear in Nucl. Phys. B
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Dose rate visualization of radioisotope thermoelectric generators
Advanced visualization techniques can be used to investigate gamma ray and neutron dose rates around complex dose rate intensive operations. A method has been developed where thousands of dose points are calculated using the MCNP(Monte Carlo N-Particle) computer code and then displayed to create color contour plots of the dose rate for complex geometries. Once these contour plots are created, they are sequenced together creating an animation to dynamically show how the dose rate changes with changes in the geometry or source over time
SO(d,d) Transformations of Ramond-Ramond Fields and Space-time Spinors
We explicitly construct the SO(d,d) transformations of Ramond-Ramond field
strengths and potentials, along with those of the space-time supersymmetry
parameters, the gravitinos and the dilatinos in type-II theories. The results
include the case when the SO(d,d) transformation involves the time direction.
The derivation is based on the compatibility of SO(d,d) transformations with
space-time supersymmetry, which automatically guarantees compatibility with the
equations of motion. It involves constructing the spinor representation of a
twist that an SO(d,d) action induces between the local Lorentz frames
associated with the left- and right-moving sectors of the worldsheet theory.
The relation to the transformation of R-R potentials as SO(d,d) spinors is also
clarified.Comment: 25 pages, LaTeX. V2: Added references, comments, and a new section on
the relation to the transformation of R-R potentials as SO(d,d) spinor
Depinning with dynamic stress overshoots: A hybrid of critical and pseudohysteretic behavior
A model of an elastic manifold driven through a random medium by an applied
force F is studied focussing on the effects of inertia and elastic waves, in
particular {\it stress overshoots} in which motion of one segment of the
manifold causes a temporary stress on its neighboring segments in addition to
the static stress. Such stress overshoots decrease the critical force for
depinning and make the depinning transition hysteretic. We find that the steady
state velocity of the moving phase is nevertheless history independent and the
critical behavior as the force is decreased is in the same universality class
as in the absence of stress overshoots: the dissipative limit which has been
studied analytically. To reach this conclusion, finite-size scaling analyses of
a variety of quantities have been supplemented by heuristic arguments.
If the force is increased slowly from zero, the spectrum of avalanche sizes
that occurs appears to be quite different from the dissipative limit. After
stopping from the moving phase, the restarting involves both fractal and
bubble-like nucleation. Hysteresis loops can be understood in terms of a
depletion layer caused by the stress overshoots, but surprisingly, in the limit
of very large samples the hysteresis loops vanish. We argue that, although
there can be striking differences over a wide range of length scales, the
universality class governing this pseudohysteresis is again that of the
dissipative limit. Consequences of this picture for the statistics and dynamics
of earthquakes on geological faults are briefly discussed.Comment: 43 pages, 57 figures (yes, that's a five followed by a seven), revte
Gauge Theory Description of D-brane Black Holes: Emergence of the Effective SCFT and Hawking Radiation
We study the hypermultiplet moduli space of an N=4, U(Q_1)xU(Q_5) gauge
theory in 1+1 dimensions to extract the effective SCFT description of near
extremal 5-dimensional black holes modelled by a collection of D1- and
D5-branes. On the moduli space, excitations with fractional momenta arise due
to a residual discrete gauge invariance. It is argued that, in the infra-red,
the lowest energy excitations are described by an effective c=6, N=4 SCFT on
T^4, also valid in the large black hole regime. The ``effective string
tension'' is obtained using T-duality covariance. While at the microscopic
level, minimal scalars do not couple to (1,5) strings, in the effective theory
a coupling is induced by (1,1) and (5,5) strings, leading to Hawking radiation.
These considerations imply that, at least for such black holes, the calculation
of the Hawking decay rate for minimal scalars has a sound foundation in string
theory and statistical mechanics and, hence, there is no information loss.Comment: 24 pages, LaTeX, very minor changes, to appear in Nucl. Phys.
Duality between Electric and Magnetic Black Holes
A number of attempts have recently been made to extend the conjectured
duality of Yang Mills theory to gravity. Central to these speculations has been
the belief that electrically and magnetically charged black holes, the solitons
of quantum gravity, have identical quantum properties. This is not obvious,
because although duality is a symmetry of the classical equations of motion, it
changes the sign of the Maxwell action. Nevertheless, we show that the chemical
potential and charge projection that one has to introduce for electric but not
magnetic black holes exactly compensate for the difference in action in the
semi-classical approximation. In particular, we show that the pair production
of electric black holes is not a runaway process, as one might think if one
just went by the action of the relevant instanton. We also comment on the
definition of the entropy in cosmological situations, and show that we need to
be more careful when defining the entropy than we are in an asymptotically-flat
case.Comment: 23 pages, revtex, no figures. Major revision: two sections on the
electric Ernst solution adde
Type IIB Solutions with Interpolating Supersymmetries
We study type IIB supergravity solutions with four supersymmetries that
interpolate between two types widely considered in the literature: the dual of
Becker and Becker's compactifications of M-theory to 3 dimensions and the dual
of Strominger's torsion compactifications of heterotic theory to 4 dimensions.
We find that for all intermediate solutions the internal manifold is not
Calabi-Yau, but has SU(3) holonomy in a connection with a torsion given by the
3-form flux. All 3-form and 5-form fluxes, as well as the dilaton, depend on
one function appearing in the supersymmetry spinor, which satisfies a nonlinear
differential equation. We check that the fields corresponding to a flat bound
state of D3/D5-branes lie in our class of solutions. The relations among
supergravity fields that we derive should be useful in studying new gravity
duals of gauge theories, as well as possibly compactifications.Comment: 27pp, v2 REVTeX4, typographical fixes and minor clarifications, v3
added ref, modified discussion of RR axion slightl
Rotating Black Holes which Saturate a Bogomol'nyi Bound
We construct and study the electrically charged, rotating black hole solution
in heterotic string theory compactified on a dimensional torus. This
black hole is characterized by its mass, angular momentum, and a
dimensional electric charge vector. One of the novel features of this solution
is that for , its extremal limit saturates the Bogomol'nyi bound. This is
in contrast with the case where the rotating black hole solution develops
a naked singularity before the Bogomol'nyi bound is reached. The extremal black
holes can be superposed, and by taking a periodic array in , one obtains
effectively four dimensional solutions without naked singularities.Comment: 13 pages, no figure
Solitons in Triangular and Honeycomb Dynamical Lattices with the Cubic Nonlinearity
We study the existence and stability of localized states in the discrete
nonlinear Schr{\"o}dinger equation (DNLS) on two-dimensional non-square
lattices. The model includes both the nearest-neighbor and long-range
interactions. For the fundamental strongly localized soliton, the results
depend on the coordination number, i.e., on the particular type of the lattice.
The long-range interactions additionally destabilize the discrete soliton, or
make it more stable, if the sign of the interaction is, respectively, the same
as or opposite to the sign of the short-range interaction. We also explore more
complicated solutions, such as twisted localized modes (TLM's) and solutions
carrying multiple topological charge (vortices) that are specific to the
triangular and honeycomb lattices. In the cases when such vortices are
unstable, direct simulations demonstrate that they turn into zero-vorticity
fundamental solitons.Comment: 17 pages, 13 figures, Phys. Rev.
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