Ram Brustein

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A large class of string-cosmology backgrounds leads to a spectrum of relic stochastic gravitational waves, strongly tilted towards high frequencies, and characterized by two basic parameters of the cosmological model. We estimate the required sensitivity for detection of the predicted gravitational radiation and show that a region of our parameter space is(More)
We construct, for the first time, a model of graceful exit transition from a dilaton-driven inflationary phase to a decelerated Friedman−Robertson−Walker era. Exploiting a demonstration that classical corrections can stabilize a high curvature string phase while the evolution is still in the weakly coupled regime, we show that if additional terms of the(More)
The Bekenstein-Hawking entropy of black holes in Einstein’s theory of gravity is equal to a quarter of the horizon area in units of Newton’s constant. Wald has proposed that in general theories of gravity the entropy of stationary black holes with bifurcate Killing horizons is a Noether charge which is in general different from the Bekenstein-Hawking(More)
A characteristic spectrum of relic gravitational radiation is produced by a period of ‘‘stringy inflation’’ in the early Universe. This spectrum is unusual, because the energy density rises rapidly with frequency. We show that correlation experiments with the two gravitational-wave detectors being built for the Laser Interferometric Gravitational Wave(More)
We find de Sitter and flat space solutions with all moduli stabilized in four dimensional supergravity theories derived from the heterotic and type II string theories, and explain how all the previously known obstacles to finding such solutions can be removed. Further, we argue that if the compact manifold allows a large enough space of discrete topological(More)
String cosmology solutions are examined in a generalized phase-space including sources representing arbitrary corrections to lowest order string-dilatongravity effective action. We find a set of necessary conditions for a graceful exit transition from a dilaton-driven inflationary phase to a radiation dominated era. We show that sources allowing such a(More)
Supernova searches have been been suggested as a method for determining precisely the current value and time variation of the equation of state, w, of the dark energy component responsible for the accelerated expansion of the Universe. We show that the method is fundamentally limited by the fact that luminosity distance depends on w through a multiple(More)