In this paper we extend the Cosmological Constant Seesaw treatment of hepth/0602112 to String/M-Theory where the cosmological constant is finite. We discuss how transitions between different λ, one of Planckian vacuum energy, can give rise to a large M Pl denominator in the Cosmological Constant Seesaw relation discussed by Banks, Motl and Carroll. We apply these ideas to 2d/3d String/M-Theory ...

Starting from an exact (in the Regge slope α ′ ) functional method for a bosonic stringy σ-model, we investigate four-dimensional cosmological string solutions in graviton, dilaton and antisymmetric tensor backgrounds, compatible with world-sheet conformal invariance, and valid beyond perturbative expansions in powers of α ′ . The antisymmetric tensor field, playing the rôle of an axion in the ...

Abstract From the field equations corresponding to a four-dimensional brane embedded in five-dimensional spacetime of Einstein–Chern–Simons theory for gravity, we find cosmological solutions that describe an accelerated expansion flat universe. Apart from quintessence-type evolution scheme, obtain transient phantom evolution, which is not ruled out by current observational data. Additionally, b...

‎This paper is devoted to definition standard higher dimension shearlet group $ mathbb{S} = mathbb{R}^{+} times mathbb {R}^{n-1} times mathbb {R}^{n} $ and determination of square integrable subrepresentations of this group‎. ‎Also we give a characterisation of admissible vectors associated to the Hilbert spaces corresponding to each su brepresentations‎.

We link observational parameters such as the deceleration parameter, the jerk, the kerk (snap) and higher-order derivatives of the scale factor, called statefinders, to the conditions which allow to develop sudden future singularities of pressure with finite energy density. In this context, and within the framework of Friedmann cosmology, we also propose higher-order energy conditions which rel...

We examine the possibility of achieving quintessential inflation, where the same field serves as both inflaton and quintessence, in the context of a five-dimensional braneworld. Braneworld cosmology provides an appropriate environment as it permits inflation with much steeper potentials than the conventional scenario, which is favorable to a late-time quintessence. We explore a wide space of mo...

In these lectures notes, we will discuss a particular higher order gravity theory, Lovelock theory, that generalises in higher dimensions than 4, general relativity. After briefly motivating modifications of gravity, we will introduce the theory in question and we will argue that it is a unique, mathematically sensible, and physically interesting extension of general relativity. We will see, by...

In brane-world cosmology gravitational waves can propagate in the higher dimensions (i.e., in the ‘bulk’). In some appropriate regimes the bulk gravitational waves may be approximated by plane waves. We systematically study five-dimensional gravitational waves that are algebraically special and of type N. In the most physically relevant case the projected non-local stress tensor on the brane is...