11,405 research outputs found
Quantum Hall Ferromagnets
It is pointed out recently that the quantum Hall states in bilayer
systems behave like easy plane quantum ferromagnets. We study the
magnetotransport of these systems using their ``ferromagnetic" properties and a
novel spin-charge relation of their excitations. The general transport is a
combination of the ususal Hall transport and a time dependent transport with
time average. The latter is due to a phase slippage process in
and is characterized by two topological constants. (Figures will be
provided upon requests).Comment: 4 pages, Revtex, Ohio State Universit
A Non-Abelian Self-Dual Gauge Theory in 5+1 Dimensions
We construct a non-Abelian gauge theory of chiral 2-forms (self-dual gauge
fields) in 6 dimensions with a spatial direction compactified on a circle of
radius R. It has the following two properties. (1) It reduces to the Yang-Mills
theory in 5 dimensions for small R. (2) It is equivalent to the
Lorentz-invariant theory of Abelian chiral 2-forms when the gauge group is
Abelian. Previous no-go theorems prohibiting non-Abelian deformations of the
chiral 2-form gauge theory are circumvented by introducing nonlocality along
the compactified dimension.Comment: 23 pages, reference adde
Dp-branes, NS5-branes and U-duality from nonabelian (2,0) theory with Lie 3-algebra
We derive the super Yang-Mills action of Dp-branes on a torus T^{p-4} from
the nonabelian (2,0) theory with Lie 3-algebra. Our realization is based on Lie
3-algebra with pairs of Lorentzian metric generators. The resultant theory then
has negative norm modes, but it results in a unitary theory by setting VEV's of
these modes. This procedure corresponds to the torus compactification,
therefore by taking a transformation which is equivalent to T-duality, the
Dp-brane action is obtained. We also study type IIA/IIB NS5-brane and
Kaluza-Klein monopole systems by taking other VEV assignments. Such various
compactifications can be realized in the nonabelian (2,0) theory, since both
longitudinal and transverse directions can be compactified, which is different
from the BLG theory. We finally discuss U-duality among these branes, and show
that most of the moduli parameters in U-duality group are recovered. Especially
in D5-brane case, the whole U-duality relation is properly reproduced.Comment: 1+26 page
A No-Go Theorem for M5-brane Theory
The BLG model for multiple M2-branes motivates an M5-brane theory with a
novel gauge symmetry defined by the Nambu-Poisson structure. This Nambu-Poisson
gauge symmetry for an M5-brane in large C-field background can be matched, on
double dimension reduction, with the Poisson limit of the noncommutative gauge
symmetry for a D4-brane in B-field background. Naively, one expects that there
should exist a certain deformation of the Nambu-Poisson structure to match with
the full noncommutative gauge symmetry including higher order terms. However,
We prove the no-go theorem that there is no way to deform the Nambu-Poisson
gauge symmetry, even without assuming the existence of a deformation of
Nambu-Poisson bracket, to match with the noncommutative gauge symmetry in 4+1
dimensions to all order, regardless of how the double dimension reduction is
implemented.Comment: v4: minor modifications
One-loop flavor changing electromagnetic transitions
We discuss the effect of the external fermion masses in the flavor-changing
radiative transitions of a heavy fermion (quark or lepton) to a lighter fermion
at the one-loop level, and point out an often overlooked crucial difference in
the sign of a charge factor between transitions of the down type
and the up type . We give formulas for the
effective vertex in various approximations and the exact formula for and .Comment: LaTeX 16 pages + 4 postscript figures. Misprints corrected, some
Comments adde
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