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Covariant gravity with Lagrange multiplier constraint
Shin'ichi Nojiri
We review on the models of gravity with a constraint by the Lagrange multiplier field. The constraint breaks general covariance or Lorentz symmetry in the ultraviolet region. We re…
Stability of accelerating cosmology in two scalar-tensor theory: Little Rip versus de Sitter
Yusaku Ito, Shin'ichi Nojiri, Sergei D. Odintsov
We develop the general reconstruction scheme in two scalar model. The quintom-like theory which may describe (different) non-singular Little Rip or de Sitter cosmology is reconstru…
Could the dynamical Lorentz symmetry breaking induce the superluminal neutrinos?
Shin'ichi Nojiri, Sergei D. Odintsov
The toy fermion model coupled with Lagrange multiplier constraint field is proposed. The possibility of superluminal neutrino propagation as result of dynamical Lorentz symmetry br…
Cosmological perturbations in -essence model
Kazuharu Bamba, Jiro Matsumoto, Shin'ichi Nojiri
Subhorizon approximation is often used in cosmological perturbation theory. In this paper, however, it is shown that the subhorizon approximation is not always a good approximation…
Cyclic, ekpyrotic and little rip universe in modified gravity
Shin'ichi Nojiri, Sergei D. Odintsov, Diego Saez-Gomez
We propose the reconstruction of gravity in such a way that corresponding theory admits cyclic and ekpyrotic universe solutions. The number of explicit examples of such $F(R…
Models for Little Rip Dark Energy
Paul H. Frampton, Kevin J. Ludwick, Shin'ichi Nojiri +2
We examine in more detail specific models which yield a little rip cosmology, i.e., a universe in which the dark energy density increases without bound but the universe never reach…