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Halo Formation in Warm Dark Matter Models
Discrepancies have emerged between the predictions of standard cold dark matter (CDM) theory and observations of clustering on subgalactic scales. Warm dark matter (WDM) is a simple modification of
The Ekpyrotic universe: Colliding branes and the origin of the hot big bang
We propose a cosmological scenario in which the hot big bang universe is produced by the collision of a brane in the bulk space with a bounding orbifold plane, beginning from an otherwise cold,
From big crunch to big bang
We consider conditions under which a universe contracting towards a big crunch can make a transition to an expanding big bang universe. A promising example is 11-dimensional M-theory in which the
Measure problem in cosmology
The Hamiltonian structure of general relativity provides a natural canonical measure on the space of all classical universes, i.e., the multiverse. We review this construction and show how one can
A Cyclic Model of the Universe
A cosmological model in which the universe undergoes an endless sequence of cosmic epochs that begin with a "bang" and end in a “crunch" is proposed, which produces the homogeneity, flatness, and energy needed to begin the next cycle.
Cosmic Evolution in a Cyclic Universe
Based on concepts drawn from the ekpyrotic scenario and M theory, we elaborate our recent proposal of a cyclic model of the universe. In this model, the universe undergoes an endless sequence of
Generating Ekpyrotic Curvature Perturbations Before the Big Bang
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described
General primordial cosmic perturbation
We consider the most general primordial cosmological perturbation in a universe filled with photons, baryons, neutrinos, and a hypothetical cold dark matter (CDM) component within the framework of