Noyce Conference Room
  US Mountain Time

Our campus is closed to the public for this event.

James P. Crutchfield (Complexity Sciences Center and Physics Department, University of California at Davis, and SFI External Professor)

Abstract:  We show why the amount of information communicated between the past and future — the excess entropy — is not in general the amount of information stored in the present — the statistical complexity.  This is a puzzle, and a long-standing one, since the former describes observed behavior, while optimal prediction requires the latter.  We present a closed-form expression for the excess entropy in terms of optimal causal predictors and retrodictors — both epsilon-machines of computational mechanics. This leads us to two new system invariants: causal irreversibility — the temporal asymmetry between causal representations — and crypticity — the degree to which a process hides its state information.

Joint work with Chris Ellison, Ryan James, and John Mahoney.

SFI Host: 
David Krakauer