arXiv subjects

Jan Louis

Publications and source records attributed to Jan Louis.

78 records · Page 5Linked to original sources

arXiv1995

On Gauge Couplings in String Theory

We investigate the field dependence of the gauge couplings of $N=1$ string vacua from the point of view of the low energy effective quantum field theory. We find that field-theoretical considerations severely constrain the form of the string loop corrections; in particular, the dilaton dependence of the gauge couplings is completely universal at the one-loop level. The moduli dependence of the string threshold corrections is also constrained, and we illustrate the power of such constraints with a detailed discussion of the orbifold vacua and the $(2,2)$ (Calabi-Yau) vacua of the heterotic string.

hep-th↗

arXiv1994

Some Phenomenological Implications of String Loop Effects

We investigate low energy implications of string loop corrections to supergravity couplings which break a possible flavor universality of the tree level. If Supersymmetry is broken by the dilaton $F$-term, universal soft scalar masses arise at the leading order but string loop corrections generically induce flavor-non-diagonal soft terms. Constraints from flavor changing neutral currents (FCNC) and CP violation then require a large supersymmtery breaking scale and thus heavy gluinos and squarks. If Supersymmetry is broken by moduli $F$-terms, universality at the string tree level can only be guaranteed by extra conditions on the Kähler potential. A large hierarchy between the gluino and squark masses ensures that FCNC and CP violation constraints are satisfied. If the soft scalar masses vanish at the string tree level, the cosmological problems related to light moduli can be evaded. However, generic string loop corrections violate FCNC bounds and require very heavy squark masses ($\approx 100\, TeV$).

hep-ph↗

arXiv1993

Model-Independent Analysis of Soft Terms in Effective Supergravity and in String Theory

We discuss supersymmetry breakdown in effective supergravities such as emerge in the low-energy limit of superstring theory. Without specifying the precise trigger of the breakdown, we analyse the soft parameters in the Lagrangian of the supersymmetrized Standard Model.

hep-th↗

arXiv1992

Differential Equations in Special Kahler Geometry

The structure of differential equations as they appear in special \K\ geometry of $N=2$ supergravity and $(2,2)$ vacua of the heterotic string is summarized. Their use for computing couplings in the low energy effective Lagrangians of string compactifications is outlined. (Talk presented at the Workshop on String Theory, April 8--10, 1992, Trieste, Italy)

hep-th↗

arXiv1992

Recent Developments in Superstring Phenomenology

Recent developments in superstring phenomenology are summarized on a non-technical level. (Talk presented at the XXVIIth Rencontre de Moriond on Electroweak Interactions and Unified Theories.)

hep-ph↗

arXiv1991

Flat Holomorphic Connections and Picard-Fuchs Identities From $N=2$ Supergravity

We show that in special Kähler geometry of $N=2$ space-time supergravity the gauge variant part of the connection is holomorphic and flat (in a Riemannian sense). A set of differential identities (Picard-Fuchs identities) are satisfied on a holomorphic bundle. The relationship with the differential equations obeyed by the periods of the holomorphic three form of Calabi-Yau manifolds is outlined.

hep-th↗