2,237 research outputs found
1+1 Dimensional Yang-Mills Theories in Light-Cone Gauge
In 1+1 dimensions two different formulations exist of SU(N) Yang Mills
theories in light-cone gauge; only one of them gives results which comply with
the ones obtained in Feynman gauge. Moreover the theory, when considered in
1+(D-1) dimensions, looks discontinuous in the limit D=2. All those features
are proven in Wilson loop calculations as well as in the study of the
bound state integral equation in the large N limit.Comment: Invited report at the Workshop "Low Dimensional Field Theory",
Telluride (CO), Aug. 5-17 1996; 16 pages, latex, no figures To appear in
International Journal of Modern Physics A minor misprints correcte
interaction in light-cone gauge formulations of Yang-Mills theory in 1+1 dimensions
A rectangular Wilson loop with sides parallel to space and time directions is
perturbatively evaluated in two light-cone gauge formulations of Yang-Mills
theory in 1+1 dimensions, with ``instantaneous'' and ``causal'' interactions
between static quarks. In the instantaneous formulation we get Abelian-like
exponentiation of the area in terms of . In the ``causal'' formulation the
loop depends not only on the area, but also on the dimensionless ratio , and being the lengths of the rectangular sides. Besides
it also exhibits dependence on . In the limit the area law
is recovered, but dependence on survives. Consequences of these results
are pointed out.Comment: 30 pages, latex, one figure included as a ps file, an Erratum
include
Time exponentiation of a Wilson loop for Yang-Mills theories in 2+\epsilon dimensions
A rectangular Wilson loop centered at the origin, with sides parallel to
space and time directions and length and respectively, is
perturbatively evaluated in Feynman gauge for Yang--Mills
theory in dimensions. When , there is a dependence on the
dimensionless ratio , besides the area. In the limit ,
keeping , the leading expression of the loop involves only the Casimir
constant of the fundamental representation and is thereby in agreement
with the expected Abelian-like time exponentiation (ALTE). At the result
depends also on , the Casimir constant of the adjoint representation and a
pure area law behavior is recovered, but no agreement with ALTE in the limit
. Consequences of these results concerning two and
higher-dimensional gauge theories are pointed out.Comment: RevTex, 28 pages, two figure files include
Spontaneous polarization and piezoelectricity in boron nitride nanotubes
Ab initio calculations of the spontaneous polarization and piezoelectric
properties of boron nitride nanotubes show that they are excellent
piezoelectric systems with response values larger than those of piezoelectric
polymers. The intrinsic chiral symmetry of the nanotubes induces an exact
cancellation of the total spontaneous polarization in ideal, isolated nanotubes
of arbitrary indices. Breaking of this symmetry by inter-tube interaction or
elastic deformations induces spontaneous polarization comparable to those of
wurtzite semiconductors.Comment: 5 pages in PRB double column format, 3 figure
Surface Polar Phonon Dominated Electron Transport in Graphene
The effects of surface polar phonons on electronic transport properties of
monolayer graphene are studied by using a Monte Carlo simulation. Specifically,
the low-field electron mobility and saturation velocity are examined for
different substrates (SiC, SiO2, and HfO2) in comparison to the intrinsic case.
While the results show that the low-field mobility can be substantially reduced
by the introduction of surface polar phonon scattering, corresponding
degradation of the saturation velocity is not observed for all three substrates
at room temperature. It is also found that surface polar phonons can influence
graphene electrical resistivity even at low temperature, leading potentially to
inaccurate estimation of the acoustic phonon deformation potential constant
- …