503 research outputs found
Consistent and covriant anomalies in the overlap formulation of chiral gauge theories
In this letter we show how the covariant anomaly emerges in the overlap
scheme. We also prove that the overlap scheme correctly reproduces the anomaly
in the flavour currents such as in vector like theories like QCD.Comment: 10 pages, Late
Regularized overlap and the chiral determinant
We study the relationship between the continuum overlap and its corresponding
chiral determinant, showing that the former amounts to an unregularised version
of the latter. We then construct a regularised continuum overlap, and consider
the chiral anomalies that follow therefrom. The relation between these
anomalies and the ones derived from the formal (i.e., unregularised) overlap is
elucidated.Comment: 14 pages, late
Fermion zero-modes on brane-worlds
We study localization of bulk fermions on a brane with inclusion of
Yang-Mills and scalar backgrounds in higher dimensions and give the conditions
under which localized chiral fermions can be obtained.Comment: Latex, 5 pages. A factor "2" mistake that propagated through a number
of equations is corrected. Conclusions unchange
Gauge Fields, Fermions and Mass Gaps in 6D Brane Worlds
We study fluctuations about axisymmetric warped brane solutions in 6D minimal
gauged supergravity. Much of our analysis is general and could be applied to
other scenarios. We focus on bulk sectors that could give rise to Standard
Model gauge fields and charged matter. We reduce the dynamics to Schroedinger
type equations plus physical boundary conditions, and obtain exact solutions
for the Kaluza-Klein wave functions and discrete mass spectra. The power-law
warping, as opposed to exponential in 5D, means that zero mode wave functions
can be peaked on negative tension branes, but only at the price of localizing
the whole Kaluza-Klein tower there. However, remarkably, the codimension two
defects allow the Kaluza-Klein mass gap to remain finite even in the infinite
volume limit. In principle, not only gravity, but Standard Model fields could
`feel' the extent of large extra dimensions, and still be described by an
effective 4D theory.Comment: 33 pages, 2 figures; typesetting problem fixed ({\o}replaced by
\omega
Non-linear quantum mechanics and semi-classical field theories
Imperial Users onl
A Formalism to Analyze the Spectrum of Brane World Scenarios
In this paper we develop a formalism to analyze the spectrum of small
perturbations about arbitrary solutions of Einstein, Yang-Mills and scalar
systems. We consider a general system of gravitational, gauge and scalar fields
in a dimensional space-time and give the bilinear action for the
fluctuations of the fields in the system around an arbitrary solution of the
classical field equations. We then consider warped geometries, popular in brane
world scenarios, and use the light cone gauge to separate the bilinear action
into a totally decoupled spin-two, -one and -zero fluctuations. We apply our
general scheme to several examples and discuss in particular localization of
abelian and non-abelian gauge fields of the standard model to branes generated
by scalar fields. We show in particular that the Nielsen-Olsen string solution
gives rise to a normalizable localized spin-1 field in any number of
dimensions.Comment: Latex, 31 pages. Final version appeared in Nucl. Phy
The Renormalization Group for Flag Manifolds
The renormalization group equations for a class of non--relativistic quantum
--models targeted on flag manifolds are given. These models emerge in a
continuum limit of generalized Heisenberg antiferromagnets. The case of the
manifold is studied in greater detail. We show
that at zero temperature there is a fixed point of the RG transformations in
--dimensions where the theory becomes relativistic. We study
the linearized RG transformations in the vicinity of this fixed point and show
that half of the couplings are irrelevant. We also show that at this fixed
point there is an enlargement of the global isometries of the target manifold.
We construct a discrete non--abelian enlargement of this kind.Comment: 22 page
Anomaly free U(1) chiral gauge theories on a two dimensional torus
We consider anomaly free combinations of chiral fermions coupled to
gauge fields on a 2D torus first in the continuum and then on the lattice in
the overlap formulation. Both in the continuum and on the lattice, when the
background consists of sufficiently large constant gauge potentials the action
induced by the fermions varies significantly under certain singular gauge
transformations. ``Ruling away'' such discontinuities cannot be justified in
the continuum framework and does not naturally fit on the lattice. Complete
gauge invariance in the continuum can be restored in some models by choosing
special boundary conditions for the fermions. Evidence is presented that gauge
averaging the overlap phases in these models produces correct continuum
results.Comment: 30 page
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