MG15 - Talk detail

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Analysis of the causal structure of collapse and evaporation process and detailed field-theoretical calculations lead us to consider the effects of black hole radiation starting prior to the final stage of collapse. Its precise form is still controversial, but its existence leads to a number of general conclusions about evolution of the collapsing bodies. Starting from a massive thin shell in spherically-symmetric spacetime and using the semiclassical Einstein equations we show that if a non-zero radiation flux is perceived by a distant observer, the shell remains at a certain sub-Planckian distance from the Schwarzschild radius. This distance depends only on the shell’s mass and evaporation rate. Moreover, a collapsing massive thin shell might become null in a finite proper time. I discuss the conditions that the metric must satisfy for such `horizon avoidance’ to take place. I then consider how these results can be extended to general spherically-symmetric collapse. Without the event horizon the information loss paradox is gone, but many important conceptual and observational questions just become more interesting.

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Abstract

Satellite missions for secure quantum communications are now becoming reality. They also provide opportunities for new tests of fundamental physics. Several possible experiments related to the QEYSSAT mission will be described. Ability to perform sensitive optical interferometry is one of the key performance requirements of such missions. This ability makes possible a new class of tests of the Einstein Equivalence Principle (EEP). The key element of EEP is the local position invariance (LPI), and one of its aspects is demonstrated by measuring the gravitational red shift. Violation of the LPI is characterized by the parameter α that in all metric theories equals to 1. Current test are effectively focused on the matter sector, assuming that electromagnetic signals travels in the usual way. We propose an interferometric test that deals exclusively with light. The main obstacle to its implementation is the first-order Doppler Effect that dominates the parameters of interest. Our design allows to eliminate this problem and potentially opens a way for all-optical tests that will put tighter bounds on α-1.

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