We prove a global existence theorem (with respect to a geometricallydefined time) for globally hyperbolic solutions of the vacuum Einstein equations which admit a T 2 isometry group with two-dimensional spacelike orbits, acting on T 3 spacelike surfaces. Visiting Scientist: Max-Planck-Institut für Gravitationsphysik (Albert-EinsteinInstitut) Schlaatzweg 1, 14473 Potsdam, Germany

Horocyclic surfaces are surfaces in hyperbolic 3-space that are foliated by horocycles. We construct horocyclic surfaces associated with spacelike curves in the lightcone and investigate their geometric properties. In particular, we classify their singularities using invariants of corresponding spacelike curves.

AbstractIntegrable systems are derived from inelastic flows of timelike, spacelike, and null curves in 2– 3– dimensional Minkowski space. The derivation uses a Lorentzian version geometrical moving frame method which is known to yield the modified Korteveg-de Vries (mKdV) equation nonlinear Schrodinger (NLS) Euclidean space, respectively. In 2–dimensional timelike/spacelike curve shown defocusi...

Mass of singularity is defined, and its relation to whether the singularity is spacelike, timelike or null is discussed for spherically symmetric spacetimes. It is shown that if the mass of singularity is positive (negative) the singularity is non-timelike (non-spacelike). The connection between the sign of the mass and the force on a particle is also discussed.

It is shown how the gauge of the “regular finite initial value problem at spacelike infinity” can be used to construct a certain type of estimates for the Maxwell field propagating on a Schwarzschild background. These estimates are constructed with the objective of obtaining information about the smoothness near spacelike and null infinity of a wide class of solutions to the Maxwell equations.

The conformal geometry of spacelike surfaces in 4-dimensional Lorentzian space forms has been studied by the authors in a previous paper, where the so-called polar transform was introduced. Here it is shown that this transform preserves spacelike conformal isothermic surfaces. We relate this new transform with the known transforms (Darboux transform and spectral transform) of isothermic surface...

We extend previous proofs that violations of the null energy condition (NEC) are a generic and universal feature of traversable wormholes to completely non-symmetric time-dependent wormholes. We show that the analysis can be phrased purely in terms of local geometry at and near the wormhole throat, and do not have to make any technical assumptions about asymptotic flatness or other global prope...

We obtain a characterization for a compact Hopf hypersurface in the nearly Kaehler sphere S using a pinching on the scalar curvature of the hypersurface. It has been also observed that the totally geodesic sphere S in S has induced Sasakian structure as a hypersurface of the nearly Kaehler sphere S. M.S.C. 2000: 53C20, 53C45.