169 research outputs found
Chiral zero modes in non local domain walls
We study a generalization of the Callan-Harvey mechanism to the case of a non
local mass. Using a 2+1 model as a concrete example, we show that both the
existence and properties of localized zero modes can also be consistently
studied when the mass is non local. After dealing with some general properties
of the resulting integral equations, we show how non local masses naturally
arise when radiative corrections are included. We do that for a 2+1 dimensional
example, and also evaluate the zero mode of the resulting non local Dirac
operator.Comment: 20 pages, LaTeX, 4 figures; typos and content of sections 2 and 3
correcte
Noncommutative theories and general coordinate transformations
We study the class of noncommutative theories in dimensions whose spatial
coordinates can be obtained by performing a smooth change of
variables on , the coordinates of a standard noncommutative
theory, which satisfy the relation , with a
constant tensor. The variables verify a commutation
relation which is, in general, space-dependent. We study the main properties of
this special kind of noncommutative theory and show explicitly that, in two
dimensions, any theory with a space-dependent commutation relation can be
mapped to another where that is constant.Comment: 21 pages, no figures, LaTeX. v2: section 5 added, typos corrected.
Version to appear in Physical Review
On bosonization in dimensions
A recently proposed path-integral bosonization scheme for massive fermions in
dimensions is extended by keeping the full momentum-dependence of the
one-loop vacuum polarization tensor. This makes it possible to discuss both the
massive and massless fermion cases on an equal footing, and moreover the
results it yields for massless fermions are consistent with the ones of
another, seemingly different, canonical quantization approach to the problem of
bosonization for a massless fermionic field in dimensions.Comment: 11 pages, Latex, omitted references added, typos correcte
A functional approach to the Van der Waals interaction
Based on a microscopic model, we use a functional integral approach to
evaluate the quantum interaction energy between two neutral atoms. Each atom is
coupled to the electromagnetic (EM) field via a dipole term, generated by an
electron bound to the nucleus via a harmonic potential. We show that the
resulting expression for the energy becomes the Van der Waals interaction
energy at the first non-trivial order in an expansion in powers of the fine
structure constant, encompassing both the long and short distance behaviours.
We also explore the opposite, strong-coupling limit, which yields a result for
the interaction energy as well as a threshold for the existence of a vacuum
decay probability, manifested here as an imaginary part for the effective
action.
In the weak-coupling limit, we also study the effect of using a general
central potential for the internal structure of the atoms.Comment: 14 pages, 3 figures, LaTe
Induced Parity Breaking Term in Arbitrary Odd Dimensions at Finite Temperature
We calculate the exact parity odd part of the effective action
() for massive Dirac fermions in 2d+1 dimensions at finite
temperature, for a certain class of gauge field configurations. We consider
first Abelian external gauge fields, and then we deal with the case of a
non-Abelian gauge group containing an Abelian U(1) subgroup. For both cases, it
is possible to show that the result depends on topological invariants of the
gauge field configurations, and that the gauge transformation properties of
depend only on those invariants and on the winding number
of the gauge transformation.Comment: 10 pages, revtex, no figure
One-loop effects in a self-dual planar noncommutative theory
We study the UV properties, and derive the explicit form of the one-loop
effective action, for a noncommutative complex scalar field theory in 2+1
dimensions with a Grosse-Wulkenhaar term, at the self-dual point. We also
consider quantum effects around non-trivial minima of the classical action
which appear when the potential allows for the spontaneous breaking of the U(1)
symmetry. For those solutions, we show that the one-loop correction to the
vacuum energy is a function of a special combination of the amplitude of the
classical solution and the coupling constant.Comment: Version to appear in JHE
Knee Arthrodesis with the Ilizarov External Fixator as Treatment for Septic Failure of Knee Arthroplasty
A simple derivation of the Overlap Dirac Operator
We derive the vector-like four dimensional overlap Dirac operator starting
from a five dimensional Dirac action in the presence of a delta-function
space-time defect. The effective operator is obtained by first integrating out
all the fermionic modes in the fixed gauge background, and then identifying the
contribution from the localized modes as the determinant of an operator in one
dimension less. We define physically relevant degrees of freedom on the defect
by introducing an auxiliary defect-bound fermion field and integrating out the
original five dimensional bulk field.Comment: 9 pages, LaTe
Finite Size Effects in the Anisotropic \lambda/4!(\phi^4_1 + \phi^4_2)_d Model
We consider the model on a
d-dimensional Euclidean space, where all but one of the coordinates are
unbounded. Translation invariance along the bounded coordinate, z, which lies
in the interval [0,L], is broken because of the boundary conditions (BC's)
chosen for the hyperplanes z=0 and z=L. Two different possibilities for these
BC's boundary conditions are considered: DD and NN, where D denotes Dirichlet
and N Newmann, respectively. The renormalization procedure up to one-loop order
is applied, obtaining two main results. The first is the fact that the
renormalization program requires the introduction of counterterms which are
surface interactions. The second one is that the tadpole graphs for DD and NN
have the same z dependent part in modulus but with opposite signs. We
investigate the relevance of this fact to the elimination of surface
divergences.Comment: 33 pages, 2 eps figure
Non-static Dimensional Reduction of QED_3 at Finite Temperature
We study an extreme non-static limit of 2+1-dimensional QED obtained by
making a dimensional reduction so that all fields are spatially uniform but
time dependent. This dimensional reduction leads to a 0+1-dimensional field
theory that inherits many of the features of the 2+1-dimensional model, such as
Chern-Simons terms, time-reversal violation, an analogue of parity violation,
and global U(2) flavor symmetry. At one-loop level, interactions induce a
Chern-Simons term at finite T with coefficient tanh(beta m_F/2), where m_F is
the fermion mass. The finite temperature two loop self-energies are also
computed, and are non-zero for all temperatures.Comment: 28 pp, 11 figures, uses axodraw.st
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