Related papers: Answering a Basic Objection to Bang/Crunch Hologra…
We show that D-dimensional de Sitter space is unstable to the nucleation of non-singular geometries containing spacetime regions with different numbers of macroscopic dimensions, leading to a dynamical mechanism of compactification. These…
Bouncing cosmologies, suggested by String/M-theory, may provide an alternative to standard inflation to account for the origin of inhomogeneities in our universe. The fundamental question regards the correct way to evolve the scalar…
A new duality is proposed in four-dimensional flat space, which exchanges between spin and orbital degrees of freedom. This is motivated by a Hodge decomposition of the angular-momentum bivector for massive fields, along which spin and…
We find exact solutions in five dimensional inhomogeneous matter dominated model with a varying cosmological constant. Adjusting arbitrary constants of integration one can also achieve acceleration in our model. Aside from an initial…
We present an effective Eulerian description, in the non-relativistic regime, of the growth of cosmological perturbations around a homogeneous but anisotropic Bianchi I spacetime background. We assume a small deviation from isotropy,…
We consider a new variant of cosmological perturbation theory that has been designed specifically to include non-linear density contrasts on scales 100 Mpc, while still allowing for linear fluctuations on larger scales. This theory is used…
The limited velocity implied by Lorentzian signature, prevents the universe to reach thermodynamic equilibrium implied by the CMB. Rapid expansion can occur by following Hawking and assuming a primordial Euclidean metric, in which case…
Recently many people have discussed the possibility that the universe is hyperbolic and was in an inflationary phase in the early stage. Under these assumptions, it is shown that the universe cannot have compact hyperbolic time-slices.…
We construct simple solutions of three-dimensional higher spin gravity interacting with matter in which only the scalar and spin-two fields are excited. They preserve Lorentz symmetry and are similar to the four-dimensional solutions…
We study extremal codimension-two areas and late-time bulk correlators between a pair of asymptotically de Sitter space universes connected through an Euclidean axion wormhole, in arbitrary dimensions. Assuming the validity of the de Sitter…
It is proved that in order to obtain a model of the accelerated cosmic expansion the thing one only need to do is to add a perturbation term to the Einstein-Hilbert Lagrangian. This term leads to some symmetry breaking terms in the fields…
String cosmology is revisited from cosmological viewpoint of holographic principle put forward by `t Hooft, and by Fischler and Susskind. It is shown that the holography requires existence of a `graceful exit' mechanism, which renders the…
We develop the holographic framework for the $\textrm{T}\overline{\textrm{T}}$ deformation of two-dimensional conformal field theories (CFT$_2$) with gravitational anomalies, characterized by unequal left and right central charges and…
Our purpose in this paper is to discuss criteria for the existence of a precise dual description of a cosmology. A number of exact descriptions exist for flat and anti de Sitter backgrounds and possibly for open FRW universes that nucleate…
We provide the first holographic evidence for the existence of a non-supersymmetric conformal manifold arising from exactly marginal but supersymmetry-breaking deformations of a superconformal three-dimensional field theory. In particular,…
We construct different neutral blackfold solutions in Anti-de Sitter and de Sitter background spacetimes in the limit where the cosmological scale is taken to be much larger than the transverse horizon size. This includes a class of…
We review in this lecture the relation between the Maldacena Conjecture, also known as AdS/CFT correspondence, and the so called Holographic principle that seems to be an essential ingredient for a quantum gravity theory. We also illustrate…
I give a critical review of the holographic hypothesis, which posits that a universe with gravity can be described by a quantum field theory in fewer dimensions. I first recall how the idea originated from considerations on black hole…
Much work has been devoted to the phenomenology and cosmology of the so-called braneworld universe, where our (3+1)-dimensional universe lies on a brane surrounded by a (4+1)-dimensional bulk spacetime that is essentially empty except for a…
In this letter we show that the noncommutative spaces, and in particular fuzzy spheres, are natural candidates which explicitly exhibit the holography, by noting that the smallest physically accessible volume is much larger that the…