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Renormalization group analysis of a quivering string model of posture control
1Centro de Astrobiología (NASA Astrobiology Institute), INTA, Carretera Ajalvir, Kilómetro 4, 28850 Torrejón de Ardoz, Madrid, Spain. alonso@laeff.esa.es
Summary
This study models human posture control using a trembling string. Adding nonlinearity reveals complex dynamics, confirming the linear model
Area of Science:
- Physics, Biomechanics, Systems Biology
Background:
- Human posture control is a complex physiological system.
- Understanding its dynamics aids in rehabilitation and robotics.
Purpose of the Study:
- To apply scaling concepts and renormalization group methods to a simplified human posture control model.
- To investigate the effects of nonlinearity on posture dynamics.
Main Methods:
- A linear model of posture control using a trembling string with damping and restoring forces.
- Introduction of uncorrelated white Gaussian noise to simulate physiological control corrections.
- Analysis using scaling concepts and renormalization group methods.
Main Results:
- A weak quadratic nonlinearity introduces a complex phase space with nontrivial fixed points.
- The transition from diffusive to saturated regimes in the linear model is a crossover phenomenon.
- The linear model demonstrates robustness against weak nonlinearities.
Conclusions:
- Posture control dynamics can be effectively modeled using physical systems and advanced analytical techniques.
- Nonlinearities significantly alter posture control dynamics, introducing new stable and unstable states.
- Predictions are made for measurable correlations in front-back displacement during posture control.