661 research outputs found
Covariant Pauli-Villars Regularization of Quantum Gravity at the One Loop Order
We study a regularization of the Pauli-Villars kind of the one loop
gravitational divergences in any dimension. The Pauli-Villars fields are
massive particles coupled to gravity in a covariant and nonminimal way, namely
one real tensor and one complex vector. The gauge is fixed by means of the
unusual gauge-fixing that gives the same effective action as in the context of
the background field method. Indeed, with the background field method it is
simple to see that the regularization effectively works. On the other hand, we
show that in the usual formalism (non background) the regularization cannot
work with each gauge-fixing.In particular, it does not work with the usual one.
Moreover, we show that, under a suitable choice of the Pauli-Villars
coefficients, the terms divergent in the Pauli-Villars masses can be corrected
by the Pauli-Villars fields themselves. In dimension four, there is no need to
add counterterms quadratic in the curvature tensor to the Einstein action
(which would be equivalent to the introduction of new coupling constants). The
technique also works when matter is coupled to gravity. We discuss the possible
consequences of this approach, in particular the renormalization of Newton's
coupling constant and the appearance of two parameters in the effective action,
that seem to have physical implications.Comment: 26 pages, LaTeX, SISSA/ISAS 73/93/E
Stress Tensor from the Trace Anomaly in Reissner-Nordstrom Spacetimes
The effective action associated with the trace anomaly provides a general
algorithm for approximating the expectation value of the stress tensor of
conformal matter fields in arbitrary curved spacetimes. In static, spherically
symmetric spacetimes, the algorithm involves solving a fourth order linear
differential equation in the radial coordinate r for the two scalar auxiliary
fields appearing in the anomaly action, and its corresponding stress tensor. By
appropriate choice of the homogeneous solutions of the auxiliary field
equations, we show that it is possible to obtain finite stress tensors on all
Reissner-Nordstrom event horizons, including the extreme Q=M case. We compare
these finite results to previous analytic approximation methods, which yield
invariably an infinite stress-energy on charged black hole horizons, as well as
with detailed numerical calculations that indicate the contrary. The
approximation scheme based on the auxiliary field effective action reproduces
all physically allowed behaviors of the quantum stress tensor, in a variety of
quantum states, for fields of any spin, in the vicinity of the entire family (0
le Q le M) of RN horizons.Comment: 43 pages, 12 figure
Trace Anomaly and Backreaction of the Dynamical Casimir Effect
The Casimir energy for massless scalar field which satisfies priodic boundary
conditions in two-dimensional domain wall background is calculated by making
use of general properties of renormalized stress-tensor. The line element of
domain wall is time dependent, the trace anomaly which is the nonvanishing
for a conformally invariant field after renormalization,
represent the back reaction of the dynamical Casimir effect.Comment: 8 pages, no figures, typos corrected, discussion added, has been
accepted for the publication in GR
The Fermion Self-Energy during Inflation
We compute the one loop fermion self-energy for massless Dirac + Einstein in
the presence of a locally de Sitter background. We employ dimensional
regularization and obtain a fully renormalized result by absorbing all
divergences with BPHZ counterterms. An interesting technical aspect of this
computation is the need for a noninvariant counterterm owing to the breaking of
de Sitter invariance by our gauge condition. Our result can be used in the
quantum-corrected Dirac equation to search for inflation-enhanced quantum
effects from gravitons, analogous to those which have been found for massless,
minimally coupled scalars.Comment: 63 pages, 3 figures (uses axodraw.sty), LaTeX 2epsilon. Revised
version (to appear in Classical and Quantum Gravity) corrects some typoes and
contains some new reference
Management and efficacy of intensified insulin therapy starting in outpatients
Diabetic patients under multiple injection insulin therapy (i.e., intensified insulin therapy, IIT) usually start this treatment during hospitalization. We report here on the logistics, efficacy, and safety of IIT, started in outpatients. Over 8 months, 52 type I and type II diabetics were followed up whose insulin regimens consecutively had been changed from conventional therapy to IIT. Two different IIT strategies were compared: free mixtures of regular and intermediate (12 hrs)-acting insulin versus the basal and prandial insulin treatment with preprandial injections of regular insulin, and ultralente (24 hrs-acting) or intermediate insulin for the basal demand. After 8 months HbA1 levels had decreased from 10.6%±2.4% to 8.0%±1.3% (means±SD). There was no difference between the two regimens with respect to metabolic control; but type II patients maintained the lowered HbA1 levels better than type I patients. Only two patients were hospitalized during the follow-up time because of severe hypoglycemia. An increase of body weight due to the diet liberalization during IIT became a problem in one-third of the patients. Our results suggest that outpatient initiation of IIT is safe and efficacious with respect to near-normoglycemic control. Weight control may become a problem in IIT patients
Decoupling of the -scalar mass in softly broken supersymmetry
It has been shown recently that the introduction of an unphysical
-scalar mass is necessary for the proper renormalization
of softly broken supersymmetric theories by dimensional reduction (\drbar).
In these theories, both the two-loop -functions of the scalar masses and
their one-loop finite corrections depend on . We find, however,
that the dependence on can be completely removed by slightly
modifying the \drbar renormalization scheme. We also show that previous \drbar
calculations of one-loop corrections in supersymmetry which ignored the
contribution correspond to using this modified scheme.Comment: 7 pages, LTH-336, NUB-3094-94TH, KEK-TH-40
Two-loop renormalization of gaugino masses in general supersymmetric gauge models
We calculate the two-loop renormalization group equations for the running
gaugino masses in general SUSY gauge models, improving our previous result. We
also study its consequence to the unification of the gaugino masses in the SUSY
SU(5) model. The two-loop correction to the one-loop relation
is found to be of the order of a few \%.Comment: 8 pages + 1 figure (omitted),KEK-TH-371 / UT-65
Conformal Supergravity in Twistor-String Theory
Conformal supergravity arises in presently known formulations of
twistor-string theory either via closed strings or via gauge-singlet open
strings. We explore this sector of twistor-string theory, relating the relevant
string modes to the particles and fields of conformal supergravity. We also use
the twistor-string theory to compute some tree level scattering amplitudes with
supergravitons, and compare to expectations from conformal supergravity. Since
the supergravitons interact with the same coupling constant as the Yang-Mills
fields, conformal supergravity states will contribute to loop amplitudes of
Yang-Mills gluons in these theories. Those loop amplitudes will therefore not
coincide with the loop amplitudes of pure super Yang-Mills theory.Comment: 43 pages harvmac tex, added footnote to introductio
Free Energy and Entropy for Semi-classical Black Holes in the Canonical Ensemble
We consider the thermodynamics of a black hole coupled to thermal radiation
in a spatially finite (spherical) region. Thermodynamic state functions are
derived in the canonical ensemble, defined by elements of radius and
boundary temperature . Using recent solutions of the semi-classical
back reaction problem, we compute the corrections to the mass of the
black hole, thermal energy, the entropy and free energy due to the presence of
hot conformal scalars, massless spinors and U(1) gauge quantum fields in the
vicinity of the hole. The free energy is particularly important for assessing
under what conditions the nucleation of black holes from hot flat space is
likely to occur.Comment: 25 pages, not including 10 Figures available upon request from the
author: LAEFF-94/08. Typed in LaTe
Strongly interacting bosons and supersymmetry
We present arguments in favor of the idea that supersymmetric sigma models
with compact symmetric K\"ahler spaces as target manifolds have a second-order
phase transition in four dimensions. When applied to electroweak symmetry
breaking, these models then do not require a light Higgs boson or
techni-resonances but predict fermionic superpartners of longitudinal W's and Z
with masses at or below TeV scale. Presence of the phase transition leads to a
fractional-power energy dependence of fixed-angle scattering amplitude of
longitudinal W's and Z's at high energies.Comment: 8 pages, LATEX, UCLA/93/TEP/2
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