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2013
Impact Factor

# Kei Moritsugu

## Publications:

 Fukuda I., Moritsugu K., Fukunishi Y. On Ergodicity for Multidimensional Harmonic Oscillator Systems with Nosé – Hoover-type Thermostat 2021, vol. 26, no. 2, pp.  183-204 Abstract A simple proof and a detailed analysis of the nonergodicity for multidimensional harmonic oscillator systems with the Nosé – Hoover-type thermostat are presented. The origin of the nonergodicity is the symmetries in the multidimensional target physical system, and it differs from that in the Nosé – Hoover thermostat with the one-dimensional harmonic oscillator. A new and simple deterministic method to recover the ergodicity is also proposed. An individual thermostat variable is attached to each degree of freedom, and all of these variables act on a friction coefficient for each degree of freedom. This action is linear and controlled by a Nosé mass matrix $\mathbf{Q}$, which is the matrix analogue of the scalar Nosé mass. The matrix $\mathbf{Q}$ can break the symmetry and contribute to the ergodicity. Keywords: ergodicity, Nosé – Hoover equation, thermostat, molecular dynamics, invariant space, multidimensional harmonic oscillator, Nosé-mass matrix, density dynamics Citation: Fukuda I., Moritsugu K., Fukunishi Y.,  On Ergodicity for Multidimensional Harmonic Oscillator Systems with Nosé – Hoover-type Thermostat, Regular and Chaotic Dynamics, 2021, vol. 26, no. 2, pp. 183-204 DOI:10.1134/S1560354721020064