ar X iv : m at h / 06 11 48 9 v 1 [ m at h . A P ] 1 6 N ov 2 00 6 GLOBAL EXISTENCE OF NULL - FORM WAVE EQUATIONS IN EXTERIOR DOMAINS

ar X iv : a st ro - p h / 06 11 09 9 v 1 2 N ov 2 00 6 Nuclear Activity in UZC Compact Groups of Galaxies

ar X iv : m at h / 06 11 45 2 v 1 [ m at h . A G ] 1 5 N ov 2 00 6 UNIRATIONALITY OF CERTAIN SUPERSINGULAR K 3 SURFACES IN CHARACTERISTIC

We show that every supersingular K3 surface in characteristic 5 with Artin invariant ≤ 3 is unirational.

ar X iv : h ep - l at / 0 11 00 06 v 3 6 N ov 2 00 1 1 Matrix elements of ∆ S = 2 operators with Wilson fermions

ar X iv : m at h / 01 11 20 8 v 1 [ m at h . D G ] 1 9 N ov 2 00 1 HOMOGENEOUS BÄCKLUND TRANSFORMATIONS OF HYPERBOLIC MONGE - AMPÈRE SYSTEMS

A Bäcklund transformation between two hyperbolic Monge-Am-p` ere systems may be described as a certain type of exterior differential system on a 6-dimensional manifold B. The transformation is homogeneous if the group of symmetries of the system acts transitively on B. We give a complete classification of homogeneous Bäcklund transformations between hyperbolic Monge-Ampère systems.

ar X iv : m at h / 06 11 38 6 v 1 [ m at h . R A ] 1 3 N ov 2 00 6 Quasi Q n - filiform Lie algebras ∗

In this paper we explicitly determine the derivation algebra, automorphism group of quasi Qn-filiform Lie algebras, and applying some properties of root vector decomposition we obtain their isomorphism theorem. AMS Classification: 17B05; 17B30