Corrections to Einstein’s equations that become important at small curvatures are considered. The field equations are derived using a Palatini variation in which the connection and metric are varied independently. In contrast to the Einstein-Hilbert variation, which yields fourth order equations, the Palatini approach produces second order equations in the metric. The Lagrangian L(R) = R− α/R i...

Action at a distance in Newtonian physics is replaced by finite propagation speeds in classical physics, the physics defined by the field theories of Maxwell and Einstein. As a result, the differential equations of motion in Newtonian physics are replaced in classical physics by functional differential equations, where the delay associated with the finite propagation speed (the speed of light) ...

Scalar boson stars and Dirac are solitonic solutions of the Einstein{Klein-Gordon Einstein- classical equations, respectively. Despite different bosonic vs: fermionic nature matter field, these to field equations have been shown qualitatively similar features [1]. In particular, for spinning most fundamental configurations can be in both cases toroidal, unlike Proca that spheroidal [2]. this pa...

As is well known, in order for the Einstein–Hilbert action to have a well defined variation, and therefore to be used for deriving field equation through the stationary action principle, it has to be amended by the addition of a suitable boundary term. It has recently been claimed that, if one constructs an action by adding this term to the matter action, the Einstein field equations can be der...

Following recent advances in the local theory of current-algebraic orbifolds, we study various geometric properties of the general WZW orbifold, the general coset orbifold and a large class of (non-linear) sigma model orbifolds. Phase-space geometry is emphasized for the WZW orbifolds – while for the sigma model orbifolds we construct the corresponding sigma model orbifold action, which include...

Corrections to Einstein’s equations that become important at small curvatures are considered. The field equations are derived using a Palatini variation in which the connection and metric are varied independently. In contrast to the Einstein-Hilbert variation, which yields fourth order equations, the Palatini approach produces second order equations in the metric. The Lagrangian L(R) = R− α/R i...

We establish analogues of the Hawking and Penrose singularity theorems based on (a) averaged energy conditions with exponential damping; (b) conditions on local stress–energy averages inspired by the quantum energy inequalities satisfied by a number of quantum field theories. As particular applications, we establish singularity theorems for the Einstein equations coupled to a classical scalar f...

We discuss the physical equivalence between the Einstein and Jordan frames in Brans-Dicke theory. The inequivalence of conformal transformed theories is clarified with the help of an old equivalence theorem of Chrisholm’s. 04.20. Fy, 04.50. +h Typeset using REVTEX 1 Brans-Dicke theory is a natural generalization of Einstein theory. In Brans-Dicke theory, the effective gravitational constantGeff...

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