arXiv subjects

Y. Ohkuwa

Publications and source records attributed to Y. Ohkuwa.

5 recordsLinked to original sources

arXiv2009

Gravitational waves originated before compactification in Kaluza-Klein theory

We investigate the propagation of multidimensional gravitational waves generated before compactification and observes today as 4-dimensional gravitational waves and gauge fields by generalizing the investigation of Alesci and Montani(AM) to the case where the internal space is an n-sphere. We also derive the 4-dimensional forms of the multidimensional harmonic gauge condition. The primary difference from the case of AM comes from the effect of curvature of the internal space which prevent the space to be static. The other effects are explicitly shown for propagation of the waves in our 4-dimensional spacetime. Static internal space exists if multidimensional cosmologicalconstant is present. Then the situation is similar to the one-dimensional internal space.

gr-qc↗

arXiv2009

On the equivalence theorem in f(R)-type generalized gravity

We investigate whether the equivalence theorem in f(R)-type gravity is valid also in quantum theory. It is shown that, if the canonical quantization is assumed, equivalence does not hold in quantum theory.

gr-qc↗

arXiv2005

A canonical formalism of f(T)-type gravity in terms of Lie derivatives

A canonical formalism of f(R)-type gravity is proposed, resolving the problem in the formalism of Buchbinder and Lyakhovich(BL). The new coordinates corresponding to the time derivatives of the metric are taken to be its Lie derivatives which is the same as in BL. The momenta canonically conjugate to them and Hamiltonian density are defined similarly to the formalism of Ostrogradski. It is shown that our method surely resolves the problem of BL.

gr-qc↗

arXiv2004

Interpretation of the first order formalism of f(R)-type gravity and the corresponding second order formalism

f(R)-type gravity in the first order formalism is interpreted as Einstein gravity with non-minimal coupling arising from the use of unphysical frame. Identification of the corresponding second order higher-curvature gravity in the physical frame is proposed by requiring that the action is the same.

gr-qc↗

arXiv2003

Correspondence between the first and the second order formalism in the generalized gravity of f(R)-type

We clarify the correspondence between the first order formalism and the second order formalism in the generalized gravity where the Lagrangian density is given by a function of the scalar curvature f(R).

gr-qc↗