24,844 research outputs found
Zero Curvature Formalism for Supersymmetric Integrable Hierarchies in Superspace
We generalize the Drinfeld-Sokolov formalism of bosonic integrable
hierarchies to superspace, in a way which systematically leads to the zero
curvature formulation for the supersymmetric integrable systems starting from
the Lax equation in superspace. We use the method of symmetric space as well as
the non-Abelian gauge technique to obtain the supersymmetric integrable
hierarchies of the AKNS type from the zero curvature condition in superspace
with the graded algebras, sl(n+1,n), providing the Hermitian symmetric space
structure.Comment: LaTeX, 9 pg
Exact Effective Action for (1+1 Dimensional) Fermions in an Abelian Background at Finite Temperature
In an effort to further understand the structure of effective actions for
fermions in an external gauge background at finite temperature, we study the
example of 1+1 dimensional fermions interacting with an arbitrary Abelian gauge
field. We evaluate the effective action exactly at finite temperature. This
effective action is non-analytic as is expected at finite temperature. However,
contrary to the structure at zero temperature and contrary to naive
expectations, the effective action at finite temperature has interactions to
all (even) orders (which, however, do not lead to any quantum corrections). The
covariant structure thus obtained may prove useful in studying 2+1 dimensional
models in arbitrary backgrounds. We also comment briefly on the solubility of
various 1+1 dimensional models at finite temperature.Comment: A few clarifying remarks added;21 page
Absence of structural correlations of magnetic defects in heavy fermion LiV2O4
Magnetic defects have pronounced effects on the magnetic properties of the
face-centered cubic compound LiV2O4. The magnetic defects arise from crystal
defects present within the normal spinel structure. High-energy x-ray
diffraction studies were performed on LiV2O4 single crystals to search for
superstructure peaks or any other evidence of periodicity in the arrangement of
the crystal defects present in the lattice. Entire reciprocal lattice planes
are mapped out with help of synchrotron radiation. No noticeable differences in
the x-ray diffraction data between a crystal with high magnetic defect
concentration and a crystal with low magnetic defect concentration have been
found. This indicates the absence of any long-range periodicity or short-range
correlations in the arrangements of the crystal/magnetic defects.Comment: 6 pages, 4 figure
The Prediction of Mass of Z'-Boson from Mixing
B_q^0-B_^0 bar mixing offers a profound probe into the effects of new
physics beyond the Standard Model. In this paper, and
mass differences are considered taking the effect of both
Z-and Z' -mediated flavour-changing neutral currents in the
mixing (q = d, s). Our estimated mass of Z' boson is accessible at the
experiments LHC and B-factories in near future.Comment: 11 pages, 02 Figure
Derivative expansion and large gauge invariance at finite temperature
We study the 0+1 dimensional Chern-Simons theory at finite temperature within
the framework of derivative expansion. We obtain various interesting relations,
solve the theory within this framework and argue that the derivative expansion
is not a suitable formalism for a study of the question of large gauge
invariance.Comment: 12 pages, Late
Intrinsic Spin Hall Effect in the presence of Extrinsic Spin-Orbit Scattering
Intrinsic and extrinsic spin Hall effects are considered together on an equal
theoretical footing for the Rashba spin-orbit coupling in two-dimensional (2D)
electron and hole systems, using the diagrammatic method for calculating the
spin Hall conductivity. Our analytic theory for the 2D holes shows the expected
lowest-order additive result for the spin Hall conductivity. But, the 2D
electrons manifest a very surprising result, exhibiting a non-analyticity in
the Rashba coupling strength where the strictly extrinsic spin Hall
conductivity (for ) cannot be recovered from the
limit of the combined theory. The theoretical results are discussed in the
context of existing experimental results.Comment: 5 pages, 2 figure
Derivative Expansion and the Effective Action for the Abelian Chern-Simons Theory at Higher Orders
We study systematically the higher order corrections to the parity violating
part of the effective action for the Abelian Chern-Simons theory in 2+1
dimensions, using the method of derivative expansion. We explicitly calculate
the parity violating parts of the quadratic, cubic and the quartic terms (in
fields) of the effective action. We show that each of these actions can be
summed, in principle, to all orders in the derivatives. However, such a
structure is complicated and not very useful. On the other hand, at every order
in the powers of the derivatives, we show that the effective action can also be
summed to all orders in the fields. The resulting actions can be expressed in
terms of the leading order effective action in the static limit. We prove gauge
invariance, both large and small of the resulting effective actions. Various
other features of the theory are also brought out.Comment: 36 page
Experimental Persistence Probability for Fluctuating Steps
The persistence behavior for fluctuating steps on the surface was determined by analyzing time-dependent
STM images for temperatures between 770 and 970K. The measured persistence
probability follows a power law decay with an exponent of . This is consistent with the value of predicted for
attachment/detachment limited step kinetics. If the persistence analysis is
carried out in terms of return to a fixed reference position, the measured
persistence probability decays exponentially. Numerical studies of the Langevin
equation used to model step motion corroborate the experimental observations.Comment: LaTeX, 11 pages, 4 figures, minor changes in References sectio
Spin polarization of the quantum Hall state
We report on results of numerical studies of the spin polarization of the
half filled second Landau level, which corresponds to the fractional quantum
Hall state at filling factor . Our studies are performed using both
exact diagonalization and Density Matrix Renormalization Group (DMRG) on the
sphere. We find that for the Coulomb interaction the exact finite-system ground
state is fully polarized, for shifts corresponding to both the Moore-Read
Pfaffian state and its particle-hole conjugate (anti-Pfaffian). This result is
found to be robust against small variations of the interaction. The low-energy
excitation spectrum is consistent with spin-wave excitations of a
fully-magnetized ferromagnet.Comment: Final version published on PR
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