Gravitational instabilities in fusion research

Demir, Pınar


Gravitational energy in quadratic-curvature gravities
Deser, S; Tekin, Bayram (2002-09-02)
We define energy (E) and compute its values for gravitational systems involving terms quadratic in curvature. There are significant differences, both conceptually and concretely, from Einstein theory. For D=4, all purely quadratic models admit constant curvature vacua with arbitrary Lambda, and E is the "cosmological" Abbott-Deser (AD) expression; instead, E always vanishes in flat, Lambda=0, background. For combined Einstein-quadratic curvature systems without explicit Lambda-term vacuum must be flat space...
Gravitational interactions in 2+1 dimensions
Dereli, Tekin; Tucker, Robin W. (IOP Publishing, 1988-7-1)
Modifications to Einstein's vacuum equations for gravitation in 2+1 dimensions are studied. The addition of the Schouten-Eisenhart 2-forms to the field equations admits gravitational wave solutions although no non-trivial static rotationally symmetric metrics exist. Higher-order derivative models for the metric are discussed together with a 2+1 Brans-Dicke theory. The latter is solved for a static metric exhibiting singularities.
Gravitational charges of transverse asymptotically AdS spacetimes
Cebeci, Hakan; Sarıoğlu, Bahtiyar Özgür; Tekin, Bayram (American Physical Society (APS), 2006-12-01)
Using Killing-Yano symmetries, we construct conserved charges of spacetimes that asymptotically approach to the flat or anti-de Sitter spaces only in certain directions. In D dimensions, this allows one to define gravitational charges (such as mass and angular momenta densities) of p-dimensional branes/solitons or any other extended objects that curve the transverse space into an asymptotically flat or AdS one. Our construction answers the question of what kind of charges the antisymmetric Killing-Yano tens...
Gravitational energy-momentum density in Bianchi type II space-times
Aydogdu, Oktay (World Scientific Pub Co Pte Lt, 2006-04-01)
In this paper, using Einstein, Landau and Lifshitz's energy-momentum complexes both in general relativity and teleparallel gravity, we calculate the total energy distribution (due to matter and fields, including gravitation) associated with locally rotationally symmetric (LRS) Bianchi type II cosmological models. We show that energy densities in these different gravitation theories are the same, so they agree with each other. We obtain the result that the total energy is zero. This result agrees with previo...
Gravitational Waves and 2.5 PN Gravitational Wave Memory
Uçanok, Onur; Tekin, Bayram; Department of Physics (2020-9)
Since the discovery of general relativity, the Einstein field equations have explainedmany phenomenon (e.g. precession of orbits) and predicted others (e.g. gravitational lensing, gravitational time dilation and black holes). Among its many predictions,the wave-like nature of the linearized theory has garnered a lot of attention due to the possiblity of gravitational wave propagation; their effects, their observability andthe complicated nature of gravitational radiation. Many scientists (that can be foun...
Citation Formats
P. Demir, “Gravitational instabilities in fusion research,” Middle East Technical University, 2000.