Thermodynamic depth of causal states: Objective complexity via minimal representations

  title={Thermodynamic depth of causal states: Objective complexity via minimal representations},
  author={James P. Crutchfield and Cosma Rohilla Shalizi},
  journal={Physical Review E},
Thermodynamic depth is an appealing but flawed structural complexity measure. It depends on a set of macroscopic states for a system, but neither its original introduction by Lloyd and Pagels nor any follow-up work has considered how to select these states. Depth, therefore, is at root arbitrary. Computational mechanics, an alternative approach to structural complexity, provides a definition for a system{close_quote}s minimal, necessary causal states and a procedure for finding them. We show… 

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