Entropy and the Typicality of Universes

Understand

The universal validity of the second law of thermodynamics is widely attributed to a finely tuned initial condition of the universe.

• This creates a problem: why is the universe atypical? We suggest that the problem is an artefact created by inappropriate transfer of the traditional concept of entropy to the whole universe.
• Use of what we call the relational $N$-body problem as a model indicates the need to employ two distinct entropy-type concepts to describe the universe.
• One, which we call entaxy, is novel.