One of the most evident properties of our universe is that its phenomena exhibit several arrows of time, which in different ways show that the future is to be very different from the past. This is mysterious because the laws of physics we believe to be fundamental, such as quantum field theory and general relativity are symmetric under reversal of the time coordinate.
Ever since Boltzmann, the standard solution to the mystery has been to impose highly time asymmetric initial conditions on the time symmetric laws. This suffices to explain to us the irreversibility of many ordinary thermodynamic processes. But it doesn't provide an adequate explanation for the arrows of time, in a cosmological context, because it raises the question of what chooses the initial conditions of our universe and why they must be time asymmetric. Is it an accident or a reflection of a new principle that distinguishes the future from the past? This is just as big a mystery as the one it claims to resolve.
In 1978 Roger Penrose made a bold proposal, which this proposal embraces and develops. I call this Penrose's hypothesis:
The most fundamental laws are time asymmetric. In certain regimes, perhaps of late times or smaller than cosmological scales, their solutions are approximated by solutions to emergent, time symmetric laws, with the imposition of time asymmetric initial conditions.
If Penrose's hypothesis is correct, it provides the basis for a true explanation for the arrows of time.
The main goal of this proposal is to develop Penrose's hypothesis into a concrete and viable physical theory, which makes concrete predictions which may be tested by doable experiments or observations.
