Searcharxiv⌕ Search

arXiv subjects

Dieter Lüst

Publications and source records attributed to Dieter Lüst.

22 records · Page 2Linked to original sources
arXiv1995

Threshold Corrections and Symmetry Enhancement in String Compactifications

We present the computation of threshold functions for Abelian orbifold compactifications. Specifically, starting from the massive, moduli-dependent string spectrum after compactification, we derive the threshold functions as target space duality invariant free energies (sum over massive string states). In particular we work out the dependence on the continuous Wilson line moduli fields. In addition we concentrate on the physically interesting effect that at certain critical points in the orbifold moduli spaces additional massless states appear in the string spectrum leading to logarithmic singularities in the threshold functions. We discuss this effect for the gauge coupling threshold corrections; here the appearance of additional massless states is directly related to the Higgs effect in string theory. In addition the singularities in the threshold functions are relevant for the loop corrections to the gravitational coupling constants.

hep-th↗
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↗