Complexity and Robustness

J. M. Carlson* and John Doyle**

*Department of Physics, University of California, Santa
Barbara, CA 93106

**Control and Dynamical Systems, California Institute of
Technology, Pasadena, CA 91125


Highly Optimized Tolerance (HOT) was recently introduced as a 
conceptual framework to study fundamental aspects of complexity. 
HOT is motivated primarily by systems from biology and engineering 
and  emphasizes 1) highly structured, nongeneric, self-dissimilar 
internal configurations and 2) robust, yet fragile external 
behavior.  HOT claims these are the most important features of 
complexity and are not accidents of evolution or artifices of 
engineering design, but are inevitably intertwined and mutually 
reinforcing.  In the spirit of this collection, our paper contrasts 
HOT with alternative perspectives on complexity, drawing on both real 
world examples and also model systems, particularly those from
Self-Organized Criticality (SOC).