  Slow (logarithmic) relaxation from a highly excited state is studied in a
Hamiltonian system with many degrees of freedom. The relaxation time is shown
to increase as the exponential of the square root of the energy of excitation,
in agreement with the Boltzmann-Jeans conjecture, while it is found to be
inversely proportional to residual Kolmogorov-Sinai entropy, introduced in this
Letter. The increase of the thermodynamic entropy through this relaxation
process is found to be proportional to this quantity.
