261 research outputs found
Domain walls in gapped graphene
The electronic properties of a particular class of domain walls in gapped
graphene are investigated. We show that they can support mid-gap states which
are localized in the vicinity of the domain wall and propagate along its
length. With a finite density of domain walls, these states can alter the
electronic properties of gapped graphene significantly. If the mid-gap band is
partially filled,the domain wall can behave like a one-dimensional metal
embedded in a semi-conductor, and could potentially be used as a single-channel
quantum wire.Comment: 4 pgs. revte
Finite size corrections and integrability of N=2 SYM and DLCQ strings on a pp-wave
We compute the planar finite size corrections to the spectrum of the dilatation operator acting on two-impurity states of a certain limit of conformal Script N = 2 quiver gauge field theory which is a ZM-orbifold of Script N = 4 supersymmetric Yang-Mills theory. We match the result to the string dual, IIB superstrings propagating on a pp-wave background with a periodically identified null coordinate. Up to two loops, we show that the computation of operator dimensions, using an effective Hamiltonian technique derived from renormalized perturbation theory and a twisted Bethe ansatz which is a simple generalization of the Beisert-Dippel-Staudacher [1] long range spin chain, agree with each other and also agree with a computation of the analogous quantity in the string theory. We compute the spectrum at three loop order using the twisted Bethe ansatz and find a disagreement with the string spectrum very similar to the known one in the near BMN limit of Script N = 4 super-Yang-Mills theory. We show that, like in Script N = 4, this disagreement can be resolved by adding a conjectured ``dressing factor'' to the twisted Bethe ansatz. Our results are consistent with integrability of the Script N = 2 theory within the same framework as that of Script N = 4
Universality and the magnetic catalysis of chiral symmetry breaking
The hypothesis that the magnetic catalysis of chiral symmetry breaking is due
to interactions of massless fermions in their lowest Landau level is examined
in the context of chirally symmetric models with short ranged interactions. It
is argued that, when the magnetic field is sufficiently large, even an
infinitesimal attractive interaction in the appropriate channel will break
chiral symmetry.Comment: 24 pages, 6 figures, REVTeX. The final version with minor
corrections. To appear in Phys Rev D60 (1999
Anyons as quon particles
The momentum operator representation of nonrelativistic anyons is developed
in the Chern - Simons formulation of fractional statistics. The connection
between anyons and the q-deformed bosonic algebra is established.Comment: 10 pages,Late
Investigations of Pairing in Anyon Systems
We investigate pairing instabilities in the Fermi-liquid-like state of a
single species of anyons. We describe the anyons as Fermions interacting with a
Chern-Simons gauge field and consider the weak coupling limit where their
statistics approaches that of Fermions. We show that, within the conventional
BCS approach, due to induced repulsive Coulomb and current-current
interactions, the attractive Aharonov-Bohm interaction is not sufficient to
generate a gap in the Fermion spectrum.Comment: (11 pages, 2 Figures not included
Magnetic field-induced insulating behavior in highly oriented pyrolitic graphite
We propose an explanation for the apparent semimetal-insulator transition
observed in highly oriented pyrolitic graphite in the presence of magnetic
field perpendicular to the layers. We show that the magnetic field opens an
excitonic gap in the linear spectrum of the Coulomb interacting quasiparticles,
in a close analogy with the phenomenon of dynamical chiral symmetry breaking in
the relativistic theories of the 2+1-dimensional Dirac fermions. Our
strong-coupling appoach allows for a non-perturbative description of the
corresponding critical behavior
Z_N Phases in Hot Gauge Theories
We argue that the \zn phases of hot gauge theories cannot be realized as a
real system with an Hermitean density matrix.Comment: 7 page
Fermi point in graphene as a monopole in momentum space
We consider the effective field theory of graphene monolayer with the Coulomb
interaction between fermions taken into account. The gauge field in momentum
space is introduced. The position of the Fermi point coincides with the
position of the corresponding monopole. The procedure of extracting such
monopoles during lattice simulations is suggested.Comment: Latex, 12 page
Two-Loop Analysis of Non-abelian Chern-Simons Theory
Perturbative renormalization of a non-Abelian Chern-Simons gauge theory is
examined. It is demonstrated by explicit calculation that, in the pure
Chern-Simons theory, the beta-function for the coefficient of the Chern-Simons
term vanishes to three loop order. Both dimensional regularization and
regularization by introducing a conventional Yang-Mills component in the action
are used. It is shown that dimensional regularization is not gauge invariant at
two loops. A variant of this procedure, similar to regularization by
dimensional reduction used in supersymmetric field theories is shown to obey
the Slavnov-Taylor identity to two loops and gives no renormalization of the
Chern-Simons term. Regularization with Yang-Mills term yields a finite
integer-valued renormalization of the coefficient of the Chern-Simons term at
one loop, and we conjecture no renormalization at higher order. We also examine
the renormalization of Chern-Simons theory coupled to matter. We show that in
the non-abelian case the Chern-Simons gauge field as well as the matter fields
require infinite renormalization at two loops and therefore obtain nontrivial
anomalous dimensions. We show that the beta function for the gauge coupling
constant is zero to two-loop order, consistent with the topological
quantization condition for this constant.Comment: 48 pages, UU/HEP/91/12; file format changed to standard Latex to
solve the problem with printin
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