No Events on Closed Causal Curves

We introduce the Causal Compatibility Conjecture for the Events, Trees, Histories (ETH) approach to Quantum Theory (QT) in the semi-classical setting. We then prove that under the assumptions of the conjecture, points on closed causal curves are physically indistinguishable in the context of the ETH approach to QT and thus the conjecture implies a compatibility of the causal structures even in presence of closed causal curves. As a consequence of this result there is no observation that could be made by an observer to tell any two points on a closed causal curve apart. We thus conclude that closed causal curves have no physical significance in the context of the ETH approach to QT. This is an indication that time travel will not be possible in a full quantum theory of gravity and thus forever remain a fantasy

Smoothness of the future and past trapped sets in Kerr-Newman-Taub-NUT spacetimes

We consider the sets of future/past trapped null geodesics in the exterior region of a sub-extremal Kerr-Newman-Taub-NUT spacetime. We show that, from the point of view of any timelike observer outside of such a black hole, trapping can be understood as two smooth sets of spacelike directions on the celestial sphere of the observer

Model reduction for analysis of cascading failures in power systems

In this paper, we apply a principal-orthogonal decomposition based method to the model reduction of a hybrid, nonlinear model of a power network. The results demonstrate that the sequence of fault events can be evaluated and predicted without necessarily simulating the whole system

The East-West asymmetry of single muons at Campinas

The EASCAMP experiment, one of the few situated in the Southern Hemisphere, operating at the State University of Campinas, UNICAMP, Brazil, detected for two years single muons in the low energetic range. The primary cosmic rays that produce these muons have a geomagnetic vertical cut-off of 10.6 GV. We studied the azimuthal distribution of three million single muons obtaining an East-West asymmetry of AEW = ( 8.91 ± 0.04)%. Another analysis concerned with the atmospheric muons propagation index is performed comparing the experimental zenith angular distribution and a simulated isotropic cosmic rays distribution