Parcourir CEREF par auteur "Boulanger, Nicolas"
Voici les éléments 1-7 de 7
-
Adiabatic invariants drive rhythmic human motion in variable gravity
01 décembre 2020, CeREF TechniqueArticle scientifiqueVoluntary human movements are stereotyped. When modeled in the framework of classical mechanics they are expected to minimize cost functions that may include energy, a natural candidate from a physiological point of view also. In time-changing environments, however, energy is no longer conserved—regardless of frictional energy dissipation—and it is therefore not the preferred candidate for any cost ... -
Alice et le Pendule : au pays des variables actions-angles
27 octobre 2020, CeREF TechniquePublication d'intérêt général/presseArticle de vulgarisaiton sur le pendule de Foucault -
Diffusion in Phase Space as a Tool to Assess Variability of Vertical Centre-of-Mass Motion during Long-Range Walking
06 février 2023, CeREF SantéCeREF TechniqueArticle scientifiqueWhen a Hamiltonian system undergoes a stochastic, time-dependent anharmonic perturbation, the values of its adiabatic invariants as a function of time follow a distribution whose shape obeys a Fokker–Planck equation. The effective dynamics of the body’s centre-of-mass during human walking is expected to represent such a stochastically perturbed dynamical system. By studying, in phase space, the ... -
A First-Quantized Model for Unparticles and Gauge Theories around Conformal Window
02 décembre 2021, CeREF TechniqueArticle scientifiqueWe first quantize an action proposed by Casalbuoni and Gomis in 2014 that describes two massless relativistic scalar particles interacting via a conformally invariant potential. The spectrum is a continuum of massive states that may be interpreted as unparticles. We then obtain in a similar way the mass operator for a deformed action in which two terms are introduced that break the conformal symmetry: ... -
The Formulations of Classical Mechanics with Foucault’s Pendulum
01 octobre 2020, CERDECAMArticle scientifiqueSince the pioneering works of Newton (1643–1727), Mechanics has been constantly reinventing itself: reformulated in particular by Lagrange (1736–1813) then Hamilton (1805–1865), it now offers powerful conceptual and mathematical tools for the exploration of dynamical systems, essentially via the action-angle variables formulation and more generally through the theory of canonical transformations. ... -
Higher-derivative harmonic oscillators: stability of classical dynamics and adiabatic invariants
06 janvier 2019, CERISICArticle scientifiquehe status of classical stability in higher-deriv- ative systems is still subject to discussions. In this note, we argue that, contrary to general belief, many higher-derivative systems are classically stable. The main tool to see this prop- erty are Nekhoroshev’s estimates relying on the action-angle formulation of classical mechanics. The latter formulation can be reached provided the Hamiltonian ... -
Motor strategies and adiabatic invariants: The case of rhythmic motion in parabolic flights
05 août 2021, CeREF TechniqueArticle scientifiqueThe role of gravity in human motor control is at the same time obvious and difficult to isolate. It can be assessed by performing experiments in variable gravity. We propose that adiabatic invariant theory may be used to reveal nearly conserved quantities in human voluntary rhythmic motion, an individual being seen as a complex time-dependent dynamical system with bounded motion in phase space. ...