69 research outputs found
Inflation from Supersymmetric Quantum Cosmology
We derive a special scalar field potential using the anisotropic Bianchi type
I cosmological model from canonical quantum cosmology under determined
conditions in the evolution to anisotropic variables . In the
process, we obtain a family of potentials that has been introduced by hand in
the literature to explain cosmological data. Considering supersymmetric quantum
cosmology, this family is scanned, fixing the exponential potential as more
viable in the inflation scenario .Comment: 14 pages, latex2e, To appear in Phys. Rev.
Topological gauge fixing
We implement the metric-independent Fock-Schwinger gauge in the abelian
quantum Chern-Simons field theory defined in . The expressions
of the various components of the propagator are determined. Although the gauge
field propagator differs from the Gauss linking density, we prove that its
integral along two oriented knots is equal to the linking number
Differentiable Rigidity under Ricci curvature lower bound
In this article we prove a differentiable rigidity result. Let and
be two closed -dimensional Riemannian manifolds ()
and be a continuous map of degree . We furthermore assume that
the metric is real hyperbolic and denote by the diameter of
. We show that there exists a number such that if the Ricci curvature of the metric is bounded below by
and its volume satisfies \vol_g (Y)\leqslant (1+\varepsilon)
\vol_{g_0} (X) then the manifolds are diffeomorphic. The proof relies on
Cheeger-Colding's theory of limits of Riemannian manifolds under lower Ricci
curvature bound.Comment: 33 pages, 1 dessi
Deformed N=2 theories, generalized recursion relations and S-duality
We study the non-perturbative properties of N=2 super conformal field
theories in four dimensions using localization techniques. In particular we
consider SU(2) gauge theories, deformed by a generic epsilon-background, with
four fundamental flavors or with one adjoint hypermultiplet. In both cases we
explicitly compute the first few instanton corrections to the partition
function and the prepotential using Nekrasov's approach. These results allow to
reconstruct exact expressions involving quasi-modular functions of the bare
gauge coupling constant and to show that the prepotential terms satisfy a
modular anomaly equation that takes the form of a recursion relation with an
explicitly epsilon-dependent term. We then investigate the implications of this
recursion relation on the modular properties of the effective theory and find
that with a suitable redefinition of the prepotential and of the effective
coupling it is possible, at least up to the third order in the deformation
parameters, to cast the S-duality relations in the same form as they appear in
the Seiberg-Witten solution of the undeformed theory.Comment: 33 pages, no figures, LaTeX2
Classical solutions for exotic instantons?
We consider the D7/D(--1) system in Type I' as a prototypical "exotic" brane
instanton. With respect to systems such as the D3/D(-1) ones, which correspond
to gauge instantons in four dimensions, exotic systems lack the bosonic mixed
moduli w of the ADHM construction, related to the instanton size, and their
possible field-theoretical interpretation as classical solutions is an
important open question. For the system at hand, we propose that it corresponds
to the point-like limit of the eight-dimensional so-called SO(8) instanton
solution. This configuration is a solution of the quartic term of the
non-abelian D7 action, i.e., the term which stays finite in the limit in which
alpha' goes to zero with the string coupling fixed that preserves the D(-1)
effects. As a necessary consistency condition, we check that the next order
term in the non-abelian effective action vanishes on the SO(8) solution so that
the limit we take is well-defined.Comment: 39 pages, 3 figures. Some references added, and minor corrections: a
more precise statement of eq. (3.18) and a few coefficients in eq. (3.10
Curing and post-curing luminescence in an epoxy resin
A spontaneous luminescence is reported when epoxy resin samples are heated in
air. This phenomenon is very sensitive to the nature of the atmosphere. The
same treatment in nitrogen leads to an extinction of the luminescence. The
emission process is restored when samples are kept for a sufficient time in
air. In order to better understand this phenomenon, we have investigated the
luminescence of the elementary constituents of the epoxy (resin and hardener)
when heated in air and nitrogen, as well as during resin curing in the same
atmospheres. It appears that the emission process is linked with the presence
of oxygen. Although the kinetics of the luminescence can differ depending on
the nature of the sample (cured resin, resin during curing, liquid components),
the emission spectra are the same during resin curing and upon heating of the
cured resin and hardener. The emission spectrum of the base resin is different.
It is concluded that the light results from a chemiluminescence process during
oxidation.Comment: p. 1
Exotic instanton counting and heterotic/type I' duality
We compute the partition function for the exotic instanton system
corresponding to D-instantons on D7 branes in Type I' theory. We exploit the
BRST structure of the moduli action and its deformation by RR background to
fully localize the integration. The resulting prepotential describes
non-perturbative corrections to the quartic couplings of the gauge field F
living on the D7's. The results match perfectly those obtained in the dual
heterotic theory from a protected 1-loop computation, thus providing a
non-trivial test of the duality itself.Comment: 42 pages, 3 figure
On Four-Point Functions of Half-BPS Operators in General Dimensions
We study four-point correlation functions of half-BPS operators of arbitrary
weight for all dimensions d=3,4,5,6 where superconformal theories exist. Using
harmonic superspace techniques, we derive the superconformal Ward identities
for these correlators and present them in a universal form. We then solve these
identities, employing Jack polynomial expansions. We show that the general
solution is parameterized by a set of arbitrary two-variable functions, with
the exception of the case d=4, where in addition functions of a single variable
appear. We also discuss the operator product expansion using recent results on
conformal partial wave amplitudes in arbitrary dimension.Comment: The discussion of the case d=6 expanded; references added/correcte
- …