854 research outputs found
Gravitational Dressing of N=2 Sigma-Models Beyond Leading Order
We study the beta-function of the N=2 sigma-model coupled to N=2 induced
supergravity. We compute corrections to first order in the semiclassical limit,
, beyond one-loop in the matter fields. As compared to the
corresponding bosonic, metric sigma-model calculation, we find new types of
contributions arising from the dilaton coupling automatically accounted for,
once the K\"ahler potential is coupled to N=2 supergravity.Comment: latex, 16 pages, 8 figure
Renormalization Group Flows in Sigma--Models Coupled to Two--Dimensional Dynamical Gravity
We consider a bosonic \s--model coupled to two--dimensional gravity. In the
semiclassical limit, , we compute the gravity dressing of
the \b--functions at two--loop order in the matter fields. We find that the
corrections due to the presence of dynamical gravity are {\em not} expressible
simply in terms of a multiplicative factor as previously obtained at the
one--loop level. Our result indicates that the critical points of the theory
are nontrivially influenced and modified by the induced gravity.Comment: Latex file, 18 pages plus 7 figure
Quantum Aspects of the Noncommutative Sine-Gordon Model
In this paper, we first use semi-classical methods to study quantum field
theoretical aspects of the integrable noncommutative sine-Gordon model proposed
in [hep-th/0406065]. In particular, we examine the fluctuations at quadratic
order around the static kink solution using the background field method. We
derive equations of motion for the fluctuations and argue that at O(theta^2)
the spectrum of fluctuations remains essentially the same as that of the
corresponding commutative theory. We compute the one-loop two-point functions
of the sine-Gordon field and the additional scalar field present in the model
and exhibit logarithmic divergences, only some of which lead to UV/IR mixing.
We briefly discuss the one-loop renormalization in Euclidean signature and
comment on the obstacles in determining the noncommutativity corrections to the
quantum mass of the kink.Comment: 1+14 pages, 8 eps figures, Added references, Version to appear in
JHE
Infrared behavior of graviton-graviton scattering
The quantum effective theory of general relativity, independent of the
eventual full theory at high energy, expresses graviton-graviton scattering at
one loop order O(E^4) with only one parameter, Newton's constant. Dunbar and
Norridge have calculated the one loop amplitude using string based techniques.
We complete the calculation by showing that the 1/(d-4) divergence which
remains in their result comes from the infrared sector and that the cross
section is finite and model independent when the usual bremsstrahlung diagrams
are included.Comment: 12 pages, uses axodra
Factorization in graviton interactions
The study of factorization in the linearized gravity is extended to the
graviton scattering processes with a massive scalar particle, with a massless
vector boson and also with a graviton. Every transition amplitude is shown to
be completely factorized and the physical implications of their common factors
are discussed.Comment: 5 pages, Revtex 3.0, SNUTP 93-7
Properties of Semi-Chiral Superfields
Whenever the N=(2,2) supersymmetry algebra of non-linear sigma-models in two
dimensions does not close off-shell, a holomorphic two-form can be defined. The
only known superfields providing candidate auxiliary fields to achieve an
off-shell formulation are semi-chiral fields. Such a semi-chiral description is
only possible when the two-form is constant. Using an explicit example,
hyper-Kahler manifolds, we show that this is not always the case. Finally, we
give a concrete construction of semi-chiral potentials for a class of
hyper-Kahler manifolds using the duality exchanging a pair consisting of a
chiral and a twisted-chiral superfield for one semi-chiral multiplet.Comment: LaTeX, 17 page
Non(anti)commutative SYM theory: Renormalization in superspace
We present a systematic investigation of one-loop renormalizability for
nonanticommutative N=1/2, U(N) SYM theory in superspace. We first discuss
classical gauge invariance of the pure gauge theory and show that in
contradistinction to the ordinary anticommutative case, different
representations of supercovariant derivatives and field strengths do not lead
to equivalent descriptions of the theory. Subsequently we develop background
field methods which allow us to compute a manifestly covariant gauge effective
action. One-loop evaluation of divergent contributions reveals that the theory
simply obtained from the ordinary one by trading products for star products is
not renormalizable. In the case of SYM with no matter we present a N=1/2
improved action which we show to be one-loop renormalizable and which is
perfectly compatible with the algebraic structure of the star product. For this
action we compute the beta functions. A brief discussion on the inclusion of
chiral matter is also presented.Comment: Latex file, 59 pages, 10 figures, One reference adde
Holomorphy, Minimal Homotopy and the 4D, N = 1 Supersymmetric Bardeen-Gross-Jackiw Anomaly
By use of a special homotopy operator, we present an explicit, closed-form
and simple expression for the left-right Bardeen-Gross-Jackiw anomalies
described as the proper superspace integral of a superfunction.Comment: 16 pp, LaTeX, Replacement includes addition comment on WZNW term and
one new referenc
Recovering Infinities in Graviton Scattering Amplitudes using Cutkosky rules
We use the Cutkosky rules as a tool for determining the infinities present in
graviton scattering amplitudes. We are able to confirm theoretical derivations
of counterterms in Einstein-Maxwell theory and to determine new results in the
Dirac-Einstein counter-Lagrangian.Comment: 10 pages, 4 Postscript figures, uses epsf.st
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