20,165 research outputs found
Non-Quadratic Gauge Fixing and Global Gauge Invariance in the Effective Action
The possibility of having a gauge fixing term in the effective Lagrangian
that is not a quadratic expression has been explored in spin-two theories so as
to have a propagator that is both traceless and transverse. We first show how
this same approach can be used in spontaneously broken gauge theories as an
alternate to the 't Hooft gauge fixing which avoids terms quadratic in the
scalar fields. This "non-quadratic" gauge fixing in the effective action
results in there being two complex Fermionic and one real Bosonic ghost fields.
A global gauge invariance involving a Fermionic gauge parameter, analogous to
the usual BRST invariance, is present in this effective action.Comment: 4 pages, revtex4 (submitted to Phys. Rev. D
The structure of the graviton self-energy at finite temperature
We study the graviton self-energy function in a general gauge, using a hard
thermal loop expansion which includes terms proportional to T^4, T^2 and
log(T). We verify explicitly the gauge independence of the leading T^4 term and
obtain a compact expression for the sub-leading T^2 contribution. It is shown
that the logarithmic term has the same structure as the ultraviolet pole part
of the T=0 self-energy function. We argue that the gauge-dependent part of the
T^2 contribution is effectively canceled in the dispersion relations of the
graviton plasma, and present the solutions of these equations.Comment: 27 pages, 6 figure
On Restricting to One Loop Order the Radiative Effects in Quantum Gravity
The dimensionful nature of the coupling in the Einstein-Hilbert action in
four dimensions implies that the theory is non-renormalizable; explicit
calculation shows that beginning at two loop order, divergences arise that
cannot be removed by renormalization without introducing new terms in the
classical action. It has been shown that, by use of a Lagrange multiplier field
to ensure that the classical equation of motion is satisfied in the path
integral, radiative effects can be restricted to one loop order. We show that
by use of such Lagrange multiplier fields, the Einstein-Hilbert action can be
quantized without the occurrence of non-renormalizable divergences. We then
apply this mechanism to a model in which there is in addition to the
Einstein-Hilbert action, a fully covariant action for a self-interacting scalar
field coupled to the metric. It proves possible to restrict loop diagrams
involving internal lines involving the metric to one-loop order; diagrams in
which the scalar field propagates occur at arbitrary high order in the loop
expansion. This model also can be shown to be renormalizable. Incorporating
spinor and vector fields in the same way as scalar fields is feasible, and so a
fully covariant Standard Model with a dynamical metric field can also be shown
to be renormalizableComment: 8 pages. This version contains more background materia
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