The Hartman effect – first discovered by MacColl, in 1932 – is the claimed observation that, when a particle tunnels, it arrives at the opposite side of the barrier the moment it encounters the barrier. If this is so, then sufficiently wide barriers and fast particles should produce superluminal effective velocities. However, such superluminal effective velocities have been dismissed as...

In this talk I shall review the implications of superluminal travel and the means by which it can be achieved in classical General Relativity. We shall then see in the specific case of superluminal warp drives how it seems that a preemptive form of chronological protection is at work once their dynamics it is analysed within quantum field theory in curved spacetime. Finally, we shall discuss...

In this talk I will discuss the properties of quantum fields in causal set theory, a theory of quantum gravity in which nonlocality emerges as a consequence of discreteness and local Lorentz invariance. In particular I will present some recent results regarding the computation of entanglement entropy in this context and consider some comparisons with other models of quantum spacetime with...

Harnessing the flow of proper time of arbitrary external systems over which we exert little or no control has been a recurring theme in both science and science-fiction. Unfortunately, all relativistic schemes to achieve this effect beyond mere time dilation are utterly unrealistic. In this work, we find that there exist non-relativistic scattering experiments which, if successful, freeze out,...

Although quantum field theory inherits much of the basic structure laid out by the postulates of ordinary quantum mechanics, it is known that the measurement theory cannot go through unscathed. There are examples of idealised measurements in quantum field theory which produce superluminal signalling. These examples indicate that endowing quantum theory with a relativistic spacetime structure...

Traversable Wormholes are a prediction of General Relativity. After the discovery of the Gravitational Wave signals detected in 2015, Traversable Wormholes have had another renaissance, because they can be considered as Black Hole Mimickers.

In this talk we give a pedagogical introduction and we present some theoretical aspects at classical and semiclassical level, namely when the source has...

For the simplest case of Ellis Wormhole (WH) the fluid moving through the mentioned metrics is considered. For this purpose, the set of linearized equations composed of the Euler and continuity equations is examined. The propagation of sound waves has been considered and corresponding non-trivial analytical and numerical results – obtained.