Conformal aspects of Palatini approach in Extended Theories of Gravity
نویسنده
چکیده
Abstract The debate on the physical relevance of conformal transformations can be faced by taking the Palatini approach into account to gravitational theories. We show that conformal transformations are not only a mathematical tool to disentangle gravitational and matter degrees of freedom (passing from the Jordan frame to the Einstein frame) but they acquire a physical meaning considering the bi-metric structure of Palatini approach which allows to distinguish between spacetime structure and geodesic structure. Examples of higher-order and non-minimally coupled theories are worked out and relevant cosmological solutions in Einstein frame and Jordan frames are discussed showing that also the interpretation of cosmological observations can drastically change depending on the adopted frame.
منابع مشابه
Palatini f(R) gravity as a fixed point
In the context of modified gravity, we point out how the Palatini version of these theories is singled out as a very special case corresponding to the unique fixed point of a transformation involving a special conformal rescaling of the metric. This mathematical peculiarity signals deeply rooted problems which make the theory unphysical. PACS: 04.50+h, 04.20.Cv, 04.20.Fy, 04.90.+e.
متن کاملExtension of the EGS theorem to metric and Palatini f(R) gravity
By using the equivalence between metric and Palatini f(R) (or “modified”) gravities with ω = 0,−3/2 Brans-Dicke theories, it is shown that the EhlersGeren-Sachs theorem of general relativity is extended to modified gravity. In the case of metric f(R) gravity studied before, this agrees with previous literature.
متن کاملPalatini Variational Principle for N - Dimensional Dilaton Gravity
We consider a Palatini variation on a general N -Dimensional second order, torsionfree dilaton gravity action and determine the resulting equations of motion. Consistency is checked by considering the restraint imposed due to invariance of the matter action under simple coordinate transformations, and the special case of N = 2 is examined. We also examine a sub-class of theories whereby a Palat...
متن کاملHow (Not) to Palatini
We revisit the problem of defining non-minimal gravity in the first order formalism. Specializing to scalar-tensor theories, which may be disguised as ‘higher-derivative’ models with the gravitational Lagrangians that depend only on the Ricci scalar, we show how to recast these theories as Palatini-like gravities. The correct formulation utilizes the Lagrange multiplier method, which preserves ...
متن کاملf(R) theories of gravity
Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology and astrophysics. Among numerous alternatives to Einstein’s theory of gravity, theories which include higher order curvature invariants, and specifically the particular class of f(R) theories, have a long history. In the last five years there has been a new st...
متن کامل