Heidelberg 2007 – scientific programme

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SYEU: Symposium Knowledge of the Early Universe

SYEU 1: Knowledge of the Early Universe

SYEU 1.3: Plenary Talk

Monday, March 5, 2007, 16:45–17:45, KIP Gr. HS

Darker than Vacuum — •Rainer Verch — Institut für Theoreti-sche Physik, Universität Leipzig, Postfach 100920, D-04009 Leipzig

It is known that systems described by quantum mechanics and by quantum field theory have the peculiar property that density-like properties, whose integrals are non-negative, can violate positivity at single points in space and time to arbitrary extent. The expectation value of the energy density at a point, for example, is unbounded below as a function of the state. In this sense, there are states which are local sinks for the energy, and they are thus, locally, "darker than vacuum". This opens a priori the possibility to encounter spacetime structures with exotic causal behaviour, such as wormholes or warp-drive scenarios, as solutions to the semiclassical generalization of Einstein’s equations where matter is treated in terms of quantum field theory but the spacetime geometry is described classically. However, the principle of stability of matter puts constraints on the amount and duration of positivity violation for, e.g., energy densities; these contraints have come to be known as Quantum (Energy) Inequalities. We will report on results obtained in the recent years on this circle of issues. We are also planning to discuss some aspects of local energy concepts in this context.