14 papers
BPS Saturation from Null Reduction
Reinhold W. Gebert, Shun'ya Mizoguchi
We show that any -dimensional strictly stationary, asymptotically Minkowskian solution of a null reduction of -dimensional pure gravity must saturate the BPS bou…
On the Imaginary Simple Roots of the Borcherds Algebra
Oliver Baerwald, Reinhold W. Gebert, Hermann Nicolai
In a recent paper (hep-th/9703084) it was conjectured that the imaginary simple roots of the Borcherds algebra at level 1 are its only ones. We here propose an indep…
Missing Modules, the Gnome Lie Algebra, and
O. Bärwald, R. W. Gebert, M. Günaydin +1
We study the embedding of Kac-Moody algebras into Borcherds (or generalized Kac-Moody) algebras which can be explicitly realized as Lie algebras of physical states of some complete…
Beyond the Frenkel-Kac-Segal construction of affine Lie algebras
R. W. Gebert
This contribution reviews recent progress in constructing affine Lie algebras at arbitrary level in terms of vertex operators. The string model describes a completely compactified…
A Nonlocal Transcendental Realization of the Sugawara Operators at Arbitrary Level
R. W. Gebert
A recently found new free field realization of the affine Sugawara operators at arbitrary level is reviewed, which involves exponentials of the well-known DDF operators in string t…
Explicit determination of a 727-dimensional root space of the hyperbolic Lie algebra
Oliver Bärwald, Reinhold W. Gebert
The 727-dimensional root space associated with the level-2 root $\bLambda_1$ of the hyperbolic Kac--Moody algebra is determined using a recently developed string theoretic…