Time Asymmetry as Universe Asymmetry

Abstract

The problem of time asymmetry, also known as the problem of the arrow of time, can be summarized in the following question: How is it possible an evident time asymmetry if the laws of physics are time symmetric? In fact, all the laws of physics are invariant under time reversal t → − t ¹. However, we have the psychological feeling that past is different than future; moreover, there are clear time asymmetric phenomena, being the natural tendency from non equilibrium to equilibrium the most conspicuous example. Astonishing enough, the solution is contained in the above italized question. Since there is a time asymmetry that cannot be explained by the time-symmetric laws (equations) of physic, it must be explained by some time-asymmetric initial conditions. But, at first sight, initial conditions are arbitrary; therefore, it seems impossible to formulate a physical law on initial conditions. This is of course a naive statement. The initial conditions of any process are produced by another process in such a way that all process in a (connected) universe are coordinated in some way. Therefore, the reason of time asymmetry is the asymmetry of the universe, namely, a global reason. The aim of this paper is to explain this fundamental fact in the clearest possible way, and to discuss some recent criticisms of this global solution [1].