Wednesday, November 25, 2015

Happy 100th birthday, General Relativity!

"La Madre Terra" by Pietro Cascella, made for ICRANet. You can see Einstein's equation, which he translated into the metaphor "marble = wood". My guess is that it symbolizes Einstein's idea that everything (matter, life, not just the earth) emerges from the perfect geometry of spacetime. I took this photo at the Marco Besso Foundation exhibition in Rome, during the XIV-th Marcel Grossman conference.

Tuesday, October 20, 2015

Quantum Measurement and Initial Conditions

Quantum measurement finds the observed system in a collapsed state, rather than in the state predicted by the Schrödinger equation. Yet there is a relatively spread opinion that the wavefunction collapse can be explained by unitary evolution (for instance in the decoherence approach, if we take into account the environment). In this article it is proven a mathematical result which severely restricts the initial conditions for which measurements have definite outcomes, if pure unitary evolution is assumed. This no-go theorem remains true even if we take the environment into account. The result does not forbid a unitary description of the measurement process, it only shows that such a description is possible only for very restricted initial conditions. The existence of such restrictions of the initial conditions can be understood in the four-dimensional block universe perspective, as a requirement of global self-consistency of the solutions of the Schrödinger equation.
The arXiv link.

Friday, May 8, 2015

The top 5 finalist essays, FQXi essay contest 2015

Here are the top 5 essays from the 40 finalists of this year's FQXi essay contest, based on the community ratings.

Unofficially, since FQXi didn't announce yet which of the more than 200 essays are the 40 finalists, although the announcement was expected since April 22. My essay is on the fourth place.

The finalists will be judged by a jury, who will decide the awards until June 6, 2015.