10,492 research outputs found
Effective Superpotentials for SO/Sp with Flavor from Matrix Models
We study matrix models related to gauge theories with flavors. We
give the effective superpotentials for gauge theories with arbitrary tree level
superpotential up to first instanton level. For quartic tree level
superpotential we obtained exact one-cut solution. We also derive
Seiberg-Witten curve for these gauge theories from matrix model argument.Comment: 17pp,2 figures, v2;refs added and to appear in MPL
Fusion and breakup in the reactions of 6,7Li and 9Be
We develop a three body classical trajectory Monte Carlo (CTMC) method to
dicsuss the effect of the breakup process on heavy-ion fusion reactions induced
by weakly bound nuclei. This method follows the classical trajectories of
breakup fragments after the breakup takes place, and thus provides an
unambiguous separation between complete and incomplete fusion cross sections.
Applying this method to the fusion reaction Li + Bi, we find that
there is a significant contribution to the total complete fusion cross sections
from the process where all the breakup fragments are captured by the target
nucleus (i.e., the breakup followed by complete fusion).Comment: 4 pages, 3 eps figures. Uses espcrc1.sty. To be published in the
proceedings of the 8th international conference on clustering aspects of
nuclear structure and dynamics, November 24 - 29, 2003, Nara, Japan (Nucl.
Phys. A
Quiver Gauge Theory of Nonabelian Vortices and Noncommutative Instantons in Higher Dimensions
We construct explicit BPS and non-BPS solutions of the Yang-Mills equations
on the noncommutative space R^{2n}_\theta x S^2 which have manifest spherical
symmetry. Using SU(2)-equivariant dimensional reduction techniques, we show
that the solutions imply an equivalence between instantons on R^{2n}_\theta x
S^2 and nonabelian vortices on R^{2n}_\theta, which can be interpreted as a
blowing-up of a chain of D0-branes on R^{2n}_\theta into a chain of spherical
D2-branes on R^{2n} x S^2. The low-energy dynamics of these configurations is
described by a quiver gauge theory which can be formulated in terms of new
geometrical objects generalizing superconnections. This formalism enables the
explicit assignment of D0-brane charges in equivariant K-theory to the
instanton solutions.Comment: 45 pages, 4 figures; v2: minor correction
Reconstruction of supernova {\nu}_{\mu}, {\nu}_{\tau}, anti-{\nu}_{\mu}, and anti-{\nu}_{\tau} neutrino spectra at scintillator detectors
We present a new technique to directly reconstruct the spectra of mu/tau
neutrinos and antineutrinos from a supernova, using neutrino-proton elastic
scattering events (nu+p to nu+p) at scintillator detectors. These neutrinos,
unlike electron neutrinos and antineutrinos, have only neutral current
interactions, which makes it very challenging, with any reaction, to detect
them and measure their energies. With updated inputs from theory and
experiments, we show that this channel provides a robust and sensitive measure
of their spectra. Given the low yields and lack of spectral information in
other neutral current channels, this is perhaps the only realistic way to
extract such information. This will be indispensable for understanding flavor
oscillations of SN neutrinos, as it is likely to be impossible to disentangle
neutrino mixing from astrophysical uncertainties in a SN without adequate
spectral coverage of all flavors. We emphasize that scintillator detectors,
e.g., Borexino, KamLAND, and SNO+, have the capability to observe these events,
but they must be adequately prepared with a trigger for a burst of low-energy
events. We also highlight the capabilities of a larger detector like LENA.Comment: v3: Typo corrected in Eq.14, and metadata edits. Matches PRD version.
14 pages, 9 figures, 1 tabl
Validity of the linear coupling approximation in heavy-ion fusion reactions at sub barrier energies
The role of higher order coupling of surface vibrations to the relative
motion in heavy-ion fusion reactions at near-barrier energies is investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. Taking Ni + Zr
reactions as examples, it is shown that all order couplings lead to
considerably improved agreement with the experimentally measured fusion cross
sections and average angular momenta of the compound nucleus for such heavy
nearly symmetric systems. The importance of higher order coupling is also
examined for asymmetric systems like O + Cd, Sm, for
which previous calculations of the fusion cross section seemed to indicate that
the linear coupling approximation was adequate. It is shown that the shape of
the barrier distributions and the energy dependence of the average angular
momentum can change significantly when the higher order couplings are included,
even for systems where measured fusion cross sections may seem to be well
reproduced by the linear coupling approximation.Comment: Latex file, 15 pages, 6 figure
Phase diagram of vortex matter in layered superconductors with random point pinning
We study the phase diagram of the superconducting vortex system in layered
high-temperature superconductors in the presence of a magnetic field
perpendicular to the layers and of random atomic scale point pinning centers.
We consider the highly anisotropic limit where the pancake vortices on
different layer are coupled only by their electromagnetic interaction. The free
energy of the vortex system is then represented as a Ramakrishnan-Yussouff free
energy functional of the time averaged vortex density. We numerically minimize
this functional and examine the properties of the resulting phases. We find
that, in the temperature () -- pinning strength () plane at constant
magnetic induction, the equilibrium phase at low and is a Bragg glass.
As one increases or a first order phase transition occurs to another
phase that we characterize as a pinned vortex liquid. The weakly pinned vortex
liquid obtained for high and small smoothly crosses over to the
strongly pinned vortex liquid as is decreased or increased -- we do not
find evidence for the existence, in thermodynamic equilibrium, of a distinct
vortex glass phase in the range of pinning parameters considered here. %cdr We
present results for the density correlation functions, the density and defect
distributions, and the local field distribution accessible via SR
experiments. These results are compared with those of existing theoretical,
numerical and experimental studies.Comment: 15 pages, including figures. Higher resolution files for Figs 3a and
11 available from author
Mass Deformations of Super Yang-Mills Theories in D= 2+1, and Super-Membranes: A Note
Mass deformations of supersymmetric Yang-Mills theories in three spacetime
dimensions are considered. The gluons of the theories are made massive by the
inclusion of a non-local gauge and Poincare invariant mass term due to
Alexanian and Nair, while the matter fields are given standard Gaussian
mass-terms. It is shown that the dimensional reduction of such mass deformed
gauge theories defined on or produces matrix quantum
mechanics with massive spectra. In particular, all known massive matrix quantum
mechanical models obtained by the deformations of dimensional reductions of
minimal super Yang-Mills theories in diverse dimensions are shown also to arise
from the dimensional reductions of appropriate massive Yang-Mills theories in
three spacetime dimensions. Explicit formulae for the gauge theory actions are
provided.Comment: 20 Page
- …