arXiv subjects

Gabriel Lopes Cardoso

Publications and source records attributed to Gabriel Lopes Cardoso.

59 records · Page 4Linked to original sources

arXiv1994

On the Relation of Four-Dimensional N=2,4 -- Supersymmetric String Backgrounds to Integrable Models

In this letter we discuss the relation of four-dimensional, $N=2$ supersymmetric string backgrounds to integrable models. In particular we show that non-Kählerian gravitational backgrounds with one $U(1)$ isometry plus non-trivial antisymmetric tensor and dilaton fields arise as the solutions of the Liouville equation or, for the case of vanishing central charge deficit, as the solutions of the continual Toda equation. When performing an Abelian duality transformation, a particular class of solutions of the continual Toda equation leads to the well-known gravitational Eguchi-Hanson instanton background with self-dual curvature tensor.

hep-th↗

arXiv1994

Moduli Dependent Non-Holomorphic Contributions of Massive States to Gravitational Couplings and $C^2$-Terms in $Z_N$-Orbifold Compactifications

It is pointed out that massive states in D=4, N=1 supergravity-matter theories can, in general, at the 1-loop level contribute non-holomorphic terms to quadratic gravitational couplings. It is then shown in the context of $(2,2)$-symmetric $Z_N$-orbifold theories that, for constant moduli backgrounds, the inclusion of such contributions can result in the cancellation of naked $C^2$-terms. ${\cal R}^2$-terms can also arise but, being ghost free, need not cancel.

hep-th↗

arXiv1993

Supersymmetric Calculation of Mixed KäHLER-Gauge and Mixed KäHLER-Lorentz Anomalies

We present a manifestly supersymmetric procedure for calculating the contributions from matter loops to the mixed Kähler-gauge and to the mixed Kähler- Lorentz anomalies in $N=1, D=4$ supergravity-matter systems. We show how this procedure leads to the well-known result for the mixed Kähler-gauge anomaly. For general supergravity-matter systems the mixed Kähler-Lorentz anomaly is found to contain a term proportional to ${\cal R}^2$ with a background field dependent coefficient as well as terms proportional to $(C_{mnpq})^2$ and to the Gauss-Bonnet topological density. We briefly comment on the relationship between the mixed Kähler-Lorentz anomaly and the moduli dependent threshold corrections to gravitational couplings in $Z_N$ orbifolds.

hep-th↗

arXiv1992

Natural Supergravity Inflation

We show that a single uncharged chiral superfield, canonically coupled to \mbox{$N=1$} supergravity with vanishing superpotential, naturally drives inflation in the early universe for a class of simple Kahler potentials. Inflation occurs due to the one-loop generation of a Kahler anomaly proportional to $\R^2$. The coefficient of this $\R^2$ term is of the correct magnitude to describe all aspects of an inflationary cosmology, including sufficient amplitude perturbations and reheating. Higher order terms proportional to $\R^n$ for $n \geq 3$ are naturally suppressed relative to the $\R^2$ term and, hence, do not destabilize the theory.

hep-th↗

arXiv1992

Coordinate and Kähler $σ$-Model Anomalies and Their Cancellation in String Effective Field Theories

We discuss the complete set of one-loop triangle graphs involving the Yang-Mills gauge connection, the \Kahler\ connection and the $σ$-model coordinate connection in the effective field theory of $(2,2)$ symmetric $Z_N$ orbifolds. That is, we discuss pure gauge, pure \Kahler\ and pure $σ$-model coordinate anomalies as well as the mixed anomalies, such as \Kahler-gauge, some of which have been discussed elsewhere. We propose a mechanism for restoring both \Kahler\ and $σ$-model coordinate symmetry based upon the introduction of two types of counterterms. Finally, we enlarge the $σ$-model generalization of the Green-Schwarz mechanism to allow the removal of the universal parts of a wider class of anomalies than those previously discussed.

hep-th↗