17 citations · 36 across the 7 of their papers we have counts for
7 papers
Geometric Analysis of Ori-type Spacetimes
J. Dietz, A. Dirmeier, M. Scherfner
In 1993 A. Ori \cite{Ori93} presented spacetimes violating the chronology condition in order to answer the question whether a time machine construction has to violate the weak ener…
Geometric Analysis of Particular Compactly Constructed Time Machine Spacetimes
Jürgen Dietz, Alexander Dirmeier, Mike Scherfner
We formulate the concept of time machine structure for spacetimes exhibiting a compactely constructed region with closed timelike curves. After reviewing essential properties of th…
On Conformal Vector Fields Parallel to The Observer Field
Alexander Dirmeier, Matthias Plaue, Mike Scherfner
We review a theorem by Hasse and Perlick establishing a result characterizing parallax-free cosmological models via three equivalent properties -- namely the existence of a redshif…
On Spacetimes with Given Kinematical Invariants: Construction and Examples
M. Plaue, M. Scherfner, L. A. M. de Sousa
We present a useful method for the construction of cosmological models by solving the differential equations arising from calculating the kinematical invariants (shear, rotation, e…
Rotation in string cosmology
Yuri N. Obukhov, Thoralf Chrobok, Mike Scherfner
We describe exact cosmological solutions with rotation and expansion in the low-energy effective string theory. These models are spatially homogeneous (closed Bianchi type IX) and…
Shear-free rotating inflation
Yuri N. Obukhov, Thoralf Chrobok, Mike Scherfner
We demonstrate the existence of shear-free cosmological models with rotation and expansion which support the inflationary scenarios. The corresponding metrics belong to the family…
On closed rotating worlds
Thoralf Chrobok, Yuri N. Obukhov, Mike Scherfner
A new solution for the stationary closed world with rigid rotation is obtained for the spinning fluid source. It is found that the spin and vorticity are locally balanced. This mod…