126,063 research outputs found
On dynamical mass generation in three dimensional supersymmetric U(1) gauge field theory
We investigate and contrast the non-perturbative infra red structure of N=1
and N=2 supersymmetric non-compact U(1) gauge field theory in three space-time
dimensions with N matter flavours. We study the Dyson-Schwinger equations in a
general gauge using superfield formalism; this ensures that supersymmetry is
kept manifest, though leads to spurious infra red divergences which we have to
avoid carefully. In the N=1 case the superfield formalism allows us to choose a
vertex which satisfies the U(1) Ward identity exactly, and we find the expected
critical behaviour in the wavefunction renormalization and strong evidence for
the existence of a gauge independent dynamically generated mass, but with no
evidence for a critical flavour number. We study the N=2 model by dimensional
reduction from four dimensional N=1 electrodynamics, and we refine the old
gauge dependence argument that there is no dynamical mass generation. We
recognize that the refinement only holds after dimensional reduction.Comment: 32 pages RevTeX; 3 axodraw figures include
Gravity: A New Holographic Perspective
A general paradigm for describing classical (and semiclassical) gravity is
presented. This approach brings to the centre-stage a holographic relationship
between the bulk and surface terms in a general class of action functionals and
provides a deeper insight into several aspects of classical gravity which have
no explanation in the conventional approach. After highlighting a series of
unresolved issues in the conventional approach to gravity, I show that (i)
principle of equivalence, (ii) general covariance and (iii)a reasonable
condition on the variation of the action functional, suggest a generic
Lagrangian for semiclassical gravity of the form with
. The expansion of in terms of the
derivatives of the metric tensor determines the structure of the theory
uniquely. The zeroth order term gives the Einstein-Hilbert action and the first
order correction is given by the Gauss-Bonnet action. Any such Lagrangian can
be decomposed into a surface and bulk terms which are related holographically.
The equations of motion can be obtained purely from a surface term in the
gravity sector. Hence the field equations are invariant under the
transformation and gravity does not
respond to the changes in the bulk vacuum energy density. The cosmological
constant arises as an integration constant in this approach. The implications
are discussed.Comment: Plenary talk at the International Conference on Einstein's Legacy in
the New Millennium, December 15 - 22, 2005, Puri, India; to appear in the
Proceedings to be published in IJMPD; 16 pages; no figure
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