He proved that the probability of a tail event is either zero or one and introduced the notion of a "field of probability" in his Foundations of the Theory of Probability.
This man used dimensional analysis to obtain an energy spectrum varying with wavenumber to the minus five-thirds power in his study of turbulence.  He proved that the probability of a tail event is either zero or one and introduced the notion of a "field of probability" in his Foundations of the Theory of Probability. Almost all integrable Hamiltonian systems with rationally independent frequencies are not (*) destroyed by sufficiently small perturbations according to a theorem named for this man, Arnold, and Moser. For a specified description language, the length of the shortest description of a string is this man's namesake complexity for that string. For 10 points, name this Russian mathematician.
This man used dimensional analysis to obtain an energy spectrum varying with wavenumber to the minus five-thirds power in his study of turbulence.  
Andrey Nikolaevich Kolmogorov