2,621 research outputs found
Extended N=2 Superconformal Structure of Gravity and W-Gravity Coupled to Matter
We show that almost all string theories, including the bosonic string, the
superstring and -string theories, possess a twisted N=2 superconformal
symmetry. This enables us to establish a connection between topological gravity
and the field theoretical description of matter coupled to gravity. We also
show how the \brs operators of the -string can be obtained by hamiltonian
reduction of . The tachyonic and ground ring states of -strings
are described in the light of the N=2 superconformal structure, and the ground
ring generators for the non-critical -string are explicitly constructed.
The relationship to models and quantum integrable systems is also briefly
described.Comment: 48 page
Diffusive electron acceleration at SNR shock fronts and the observed SNR radio spectral indices
The radio synchrotron emission from relativistic electrons in shell supernova remnants (SNRs) provides a unique opportunity to probe the energy distribution of energetic electrons at their acceleration site (SNR shock fronts). This information provides insight into the acceleration mechanism(s). The implications of these observations for the diffusive (first-order Fermi) acceleration of electrons at the SNR shock fronts are discussed
Calculations for Mirror Symmetry with D-branes
We study normal functions capturing D-brane superpotentials on several one-
and two-parameter Calabi-Yau hypersurfaces and complete intersections in
weighted projective space. We calculate in the B-model and interpret the
results using mirror symmetry in the large volume regime, albeit without
identifying the precise A-model geometry in all cases. We identify new classes
of extensions of Picard-Fuchs equations, as well as a novel type of topology
changing phase transition involving quantum D-branes. A 4-d domain wall which
is obtained in one region of closed string moduli space from wrapping a
four-chain interpolating between two Lagrangian submanifolds is, for other
values of the parameters, represented by a disk ending on a single Lagrangian.Comment: 42 page
On Heterotic/Type I Duality in d=8
We discuss heterotic corrections to quartic internal U(1) gauge couplings and
check duality by calculating one-loop open string diagrams and identifying the
D-instanton sum in the dual type I picture. We also compute SO(8)^4 threshold
corrections and finally R^2 corrections in type I theory.Comment: 9 pages, Latex, To appear in the proceedings of "Quantum Aspects of
Gauge Theories, Supersymmetries and Unification", Corfu, September 199
Bright Flash Neutron Radiography at the McClellan Nuclear Research Reactor
AbstractThe University of California, Davis McClellan Nuclear Research Center (MNRC) operates a 2 MW TRIGATM reactor, which is currently the highest power TRIGATM reactor in the United States. The Center was originally build by the US Air Force to detect hidden defects in aircraft structures using neutron radiography; the Center can accommodate samples as large as 10.00 m long, 3.65 m high, and weighing up to 2,270kg.The MNRC reactor can be pulsed to 350 MW for about 30ms (FWHM). The combination of a short neutron pulse with a fast microchannel plate based neutron detector enables high-resolution flash neutron radiography to complement conventional neutron radiograph
Hints for Off-Shell Mirror Symmetry in type II/F-theory Compactifications
We perform a Hodge theoretic study of parameter dependent families of
D-branes on compact Calabi-Yau manifolds in type II and F-theory
compactifcations. Starting from a geometric Gauss-Manin connection for B type
branes we study the integrability and flatness conditions. The B model geometry
defines an interesting ring structure of operators. For the mirror A model this
indicates the existence of an open-string extension of the so-called A model
connection, whereas the discovered ring structure should be part of the
open-string A model quantum cohomology. We obtain predictions for genuine
Ooguri-Vafa invariants for Lagrangian branes on the quintic in P4 that pass
some non-trivial consistency checks. We discuss the lift of the brane
compactifications to F-theory on Calabi-Yau 4-folds and the effective couplings
in the effective supergravity action as determined by the N = 1 special
geometry of the open-closed deformation space.Comment: 49 pages, 1 table; v2: Appendix and references added, minor
corrections; v3: discussion in sect. 2 extended, version published in
Nucl.Phys.
Aspects of quark mass generation on a torus
In this talk we report on recent results for the quark propagator on a
compact manifold. The corresponding Dyson-Schwinger equations on a torus are
solved on volumes similar to the ones used in lattice calculations. The
quark-gluon interaction is fixed such that the lattice results are reproduced.
We discuss both the effects in the infinite volume/continuum limit as well as
effects when the volume is small.Comment: 3 pages, 3 figures; talk given by CF at QNP06, Madrid, June 200
Heterotic/type I duality, D-instantons and an N=2 AdS/CFT correspondence
D-instanton effects are studied for the IIB orientifold T^2/I\Omega(-1)^{F_L}
of Sen using type I/heterotic duality. An exact one loop threshold calculation
of t_8 \tr F^4 and t_8(\tr F^2)^2 terms for the heterotic string on T^2 with
Wilson lines breaking SO(32) to SO(8)^4 is related to D-instanton induced terms
in the worldvolume of D7 branes in the orientifold. Introducing D3 branes and
using the AdS/CFT correspondence in this case, these terms are used to
calculate Yang-Mills instanton contributions to four point functions of the
large N_c limit of N=2 USp(2N_c) SYM with four fundamental and one
antisymmetric tensor hypermultiplets.Comment: 25 pages, harvmac(b), one figure, v2: minor changes, version to
appear in PR
New Symmetries of Supersymmetric Effective Lagrangians
We consider the structure of effective lagrangians describing the low-energy
dynamics of supersymmetric theories in which a global symmetry is
spontaneously broken to a subgroup while supersymmetry is unbroken. In
accordance with the supersymmetric Goldstone theorem, these lagrangians contain
Nambu--Goldstone superfields associated with a coset space ,
where is the complexification of and is the largest
subgroup of that leaves the order parameter invariant. The lagrangian may
also contain additional light matter fields. To analyze the effective
lagrangian for the matter fields, we first consider the case where the
effective lagrangian is obtained by integrating out heavy modes at weak
coupling (but including non-perturbative effects such as instantons). We show
that the superpotential of the matter fields is invariant, which can
give rise to non-trivial relations among independent -invariants in the
superpotential. We also show that the Kahler potential of the matter fields can
be restricted by a remnant of symmetry. These results are
non-perturbative and have a simple group-theoretic interpretation. When we
relax the weak-coupling constraint, there appear to be additional possibilities
for the action of on the matter fields, hinting that the constraints
imposed by may be even richer in strongly coupled theories.Comment: 23 pages, plain Te
Channeled blast wave behavior based on longitudinal instabilities
To address the important issue of how kinetic energy of collimated blast
waves is converted into radiation, Pohl & Schlickeiser (2000) have recently
investigated the relativistic two-stream instability of electromagnetic
turbulence. They have shown that swept-up matter is quickly isotropized in the
blast wave, which provides relativistic particles and, as a result, radiation.
Here we present new calculations for the electrostatic instability in such
systems. It is shown that the electrostatic instability is faster than the
electromagnetic instability for highly relativistic beams. However, even after
relaxation of the beam via the faster electrostatic turbulence, the beam is
still unstable with respect to the electromagnetic waves, thus providing the
isotropization required for efficient production of radiation. While the
emission spectra in the model of Pohl and Schlickeiser have to be modified, the
basic characteristics persist.Comment: Astronomy & Astrophysics, in pres
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