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Nieuwenhuizen T.M.,Institute for Theoretical Physics
Foundations of Physics | Year: 2011

It is explained on a physical basis how absence of contextuality allows Bell inequalities to be violated, without bringing an implication on locality or realism. Hereto we connect first to the local realistic theory Stochastic Electrodynamics, and then put the argument more broadly. Thus even if Bell Inequality Violation is demonstrated beyond reasonable doubt, it will have no say on local realism, because absence of contextuality prevents the Bell inequalities to be derived from local realistic models. © 2010 The Author(s). Source


Koivisto T.S.,Institute for Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Nonsingular cosmologies are investigated in the framework of f(R) gravity within the first order formalism. General conditions for bounces in isotropic and homogeneous cosmology are presented. It is shown that only a quadratic curvature correction is needed to predict a bounce in a flat or to describe cyclic evolution in a curved dust-filled universe. Formalism for perturbations in these models is set up. In the simplest cases, the perturbations diverge at the turnover. Conditions to obtain smooth evolution are derived. © 2010 The American Physical Society. Source


Koivisto T.,Institute for Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

A variational principle was recently suggested by Goenner, where an independent metric generates the spacetime connection. It is pointed out here that the resulting theory is equivalent to the usual Palatini theory. However, a bimetric reformulation of the variational principle leads to theories which are physically distinct from both the metric and the metric-affine ones, even for the Einstein-Hilbert action. They are obtained at a decoupling limit of C-theories, which contain also other viable generalizations of the Palatini theories. © 2011 American Physical Society. Source


Koivisto T.S.,Institute for Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

C-theory provides a unified framework to study metric, metric-affine and more general theories of gravity. In the vacuum weak-field limit of these theories, the parameterized post-Newtonian parameters β and γ can differ from their general relativistic values. However, there are several classes of models featuring long-distance modifications of gravity but nevertheless passing the Solar System tests. Here it is shown how compute the parameterized post-Newtonian parameters in C-theories and also in nonminimally coupled curvature theories, correcting previous results in the literature for the latter. © 2011 American Physical Society. Source


Alexandru A.,George Washington University | Wenger U.,Institute for Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We present a reduction method for Wilson-Dirac fermions with nonzero chemical potential which generates a dimensionally reduced fermion matrix. The size of the reduced fermion matrix is independent of the temporal lattice extent and the dependence on the chemical potential is factored out. As a consequence the reduced matrix allows a simple evaluation of the Wilson fermion determinant for any value of the chemical potential and hence the exact projection to the canonical partition functions. © 2011 American Physical Society. Source

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