We present a new two-parameter family of solutions of Einstein gravity with negative cosmological constant in 2+1 dimensions. These solutions are obtained by squashing the anti-deSitter geometry along one direction and posses four Killing vectors. Global properties as well as the four dimensional generalization are discussed, followed by the investigation of the geodesic motion. A simple global...

The geodesic graph of Riemannian spaces all geodesics of which are orbits of 1-parameter isometry groups is constructed by J. Szenthe in 1976 and it became a basic tool for studying such spaces, called g.o. spaces. This infinitesimal structure corresponds to the reductive complement m in the case of naturally reductive spaces. The systematic study of Riemannian g.o. spaces is started by O. Kowa...

Let T : H1 H2 H3 ! C be a trilinear form where H1, H2, H3 are separable Hilbertspaces. In the hypothesis that at least two of the three spaces are nite dimensional weshow that the norm square = kTk2 is a root of a certain algebraic equation, usually ofvery high degree, which we baptize the milleniar equation, because it is an analogue ofthe secular equation in the bilinear c...

This paper considers the identiiability of state space models for a system that is expressed as a linear fractional transformation (LFT): a constant matrix (containing identiied parameters) in feedback with a nite-dimensional, block-diagonal (\structured") linear operator. This model structure can represent linear time-invariant, linear parameter-varying, uncertain, and multidimensional systems...

Here, u is a p-dimensional decision variable, x is an n-dimensional parameter vector, X is a nonempty set-valued map from R to R, which specifies a feasible decision set, and f is an objective map from R × R to R, wherem, n, p are positive integers. The norms of all finite dimensional spaces are denoted by ‖ · ‖. C is a closed convex pointed cone with nonempty interior in R. The cone C induces ...

This paper studies nonparametric estimation of conditional moment models in which the generalized residual functions can be nonsmooth in the unknown functions of endogenous variables. This is a nonparametric nonlinear instrumental variables (IV) problem. We propose a class of penalized sieve minimum distance (PSMD) estimators which are minimizers of a penalized empirical minimum distance criter...

1 This paper studies nonparametric estimation of conditional moment restrictions in which the generalized residual functions can be nonsmooth in the unknown functions of endogenous variables. This is a nonparametric nonlinear instrumental variables (IV) problem. We propose a class of penalized sieve minimum distance (PSMD) estima-tors, which are minimizers of a penalized empirical minimum dista...