Recovering the effective cosmological constant in extended gravity theories
نویسندگان
چکیده
In the framework of extended gravity theories, we discuss the meaning of a time dependent “cosmological constant” and give a set of conditions to recover asymptotic de Sitter behaviour for a class of cosmological models independently of initial data. To this purpose we introduce a time–dependent (effective) quantity which asymptotically becomes the true cosmological constant. We will deal with scalar–tensor, fourth and higher than fourth–order theories. PACS: 98.80H, 04.50+h e-mail address: capozziello @vaxsa.csied.unisa.it [email protected] [email protected]
منابع مشابه
The Effective Cosmological Constant in Higher Order Gravity Theories
Fundamental issues as the determination of gravity vacuum state, the mechanism which led the early universe to the today observed large scale structures, and the prediction of what will be the fate of the whole universe are all connected to the determination of cosmological constant. Besides, from several points of view, it seems that Einstein’s theory of gravity must be generalized to higher–o...
متن کاملNonminimal Derivative Couplings and Inflation in Generalized Theories of Gravity
We study extended theories of gravity where nonminimal derivative couplings of the form Rφ, kφ, l are present in the Lagrangian. We show how and why the other couplings of similar structure may be ruled out and then deduce the field equations and the related cosmological models. Finally, we get inflationary solutions which do follow neither from any effective scalar field potential nor from a c...
متن کاملNonminimal Derivative Coupling and the Recovering of Cosmological Constant
We show that the existence of the cosmological constant can be connected to a nonminimal derivative coupling, in the action of gravity, between the geometry and the kinetic part of a given scalar field without introducing any effective potential of scalar fields. Exact solutions are given. PACS: 98.80 H, 04.50 +h E-mail:[email protected] E-mail:[email protected]
متن کاملConstraining the Schwarzschild-de Sitter Solution in Models of Modified Gravity
The Schwarzschild-de Sitter (SdS) solution exists in the large majority of modified gravity theories, as expected, and in particular the effective cosmological constant is determined by the specific parameters of the given theory. We explore the possibility to use future extended radio-tracking data from the currently ongoing New Horizons mission in the outskirts peripheries of the Solar System...
متن کاملSymmetric Variations of the Metric and Extrema of the Action for Pure Gravity
Symmetries of generalized gravitational actions, yielding field equations which typically involve at most second-order derivatives of the metric, are considered. The field equations for several different higher-derivative theories in the first-order formalism are derived, and variations of a generic set of higher-order curvature terms appearing in string effective actions are studied. It is sho...
متن کامل