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The definition of relative robustness and a two-parameter family of phase portraits in the dynamics of a rigid body. (English. Russian original) Zbl 0874.70006
Russ. Math. Surv. 51, No. 1, 165-166 (1996); translation from Usp. Mat. Nauk 51, No. 1, 175-176 (1996).
The author introduces the notion of relative robustness (structural stability) and illustrates it on an example of a rigid body interacting with a medium. The difference from the classical notion of robustness is that the author considers a $$C^1$$-neighbourhood of a vector field only in a certain class of vector fields, not in the space of all vector fields, and the fields from the neighbourhood should be equivalent to the initial vector field through a homeomorphism close (in $$C^0$$-topology) to the unit homeomorphism. Relative robustness of varying degree is also introduced.

##### MSC:
 70E15 Free motion of a rigid body 70G10 Generalized coordinates; event, impulse-energy, configuration, state, or phase space for problems in mechanics 37C75 Stability theory for smooth dynamical systems
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