We studied the time-averaged gamma-ray burst spectra accumulated by the spectroscopy detectors of the Burst and Transient Source Experiment. The spectra are described well at low energy by a… Expand

Negative energy densities and fluxes due to quantum coherence effects in quantum field theories are discussed. Such negative energy fluxes seemingly lead to a breakdown of the second law of… Expand

Although quantum field theory allows local negative energy densities and fluxes, it also places severe restrictions upon the magnitude and extent of the negative energy. The restrictions take the… Expand

We will apply the quantum-inequality-type restrictions to Alcubierre's warp drive metric on a scale in which a local region of spacetime can be considered `flat'. These are inequalities that restrict… Expand

The effects of spacetime curvature upon phase transitions in an expanding universe are investigated. We consider a Robertson-Walker model which is a radiation-dominated universe at early times and… Expand

In a previous paper, a bound on the negative energy density seen by an arbitrary inertial observer was derived for the free massless, quantized scalar eld in four-dimensional Minkowski spacetime.… Expand

We consider the theory of quantized gravitational wave perturbations in the three types of Robertson-Walker universes. In a gauge analogous to the Coulomb gauge in electrodynamics it is possible to… Expand

We study the fluctuations of the stress tensor for a massless scalar field in two- and four-dimensional Minkowski spacetime in the vacuum state. Covariant expressions for the stress tensor… Expand