Sciences Et Techniques

Boson stars and black holes with complex and real scalar hair

2025-04-08T00:00:00Z

Boson stars and black holes with complex and real scalar hair Brihaye, Yves; Buisseret, Fabien; Hartmann, Betti; Layfield, Oliver We discuss boson stars and black holes with scalar hair in a model where the complex scalar field forming the boson star and the hair on the black hole, respectively, interacts with a real scalar field via a H´enon-Heiles-type potential. We demonstrate that black holes and boson stars carrying only a real scalar field with cubic self-interaction are possible and that black holes with both real and complex scalar field branch off from these solutions for sufficiently large interaction between the two fields and/or sufficiently large horizon radius rh. The latter possess lower mass for the same choice of coupling constants than the former, however seem to be thermodynamically preferred only for high enough temperature.

Q-balls and charged Q-balls in a two-scalar field theory with generalized Henon-Heiles potential

2024-04-30T00:00:00Z

Q-balls and charged Q-balls in a two-scalar field theory with generalized Henon-Heiles potential Buisseret, Fabien; Brihaye, Yves We construct Q-ball solutions from a model consisting of one massive scalar field ξ and one massive complex scalar field ϕ interacting via the cubic couplings g1ξϕ ϕ þ g2ξ3, typical of Henon-Heiles-like potentials. Although being formally simple, these couplings allow for Q-balls. In one spatial dimension, analytical solutions exist, either with vanishing or nonvanishing ϕ. In three spatial dimensions, we numerically build Q-ball solutions and investigate their behaviors when changing the relatives values of g1 and g2. For g1 < g2, two Q-balls with the same frequency exist, while ω ¼ 0 can be reached when g1 > g2. We then extend the former solutions by gauging the U(1) symmetry of ϕ and show that charged Q-balls exist.

Diffusion in Phase Space as a Tool to Assess Variability of Vertical Centre-of-Mass Motion during Long-Range Walking

2023-02-06T00:00:00Z

Diffusion in Phase Space as a Tool to Assess Variability of Vertical Centre-of-Mass Motion during Long-Range Walking Boulanger, Nicolas; BUISSERET, Fabien; Dehouck, Victor; DIERICK, Frédéric; White, Olivier When 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 vertical motion of the body’s centre-of-mass of 25 healthy participants walking for 10 min at spontaneous speed, we show that the distribution of the adiabatic invariant is compatible with the solution of a Fokker–Planck equation with a constant diffusion coefficient. The latter distribution appears to be a promising new tool for studying the long-range kinematic variability of walking.

Compte rendu de P. Galluzzi, «Galileo, Rosmini, Darwin : triumviri del cattolicesimo riformatore (1870-1918)»

2022-01-01T00:00:00Z

Compte rendu de P. Galluzzi, «Galileo, Rosmini, Darwin : triumviri del cattolicesimo riformatore (1870-1918)» STOFFEL, Jean-François Compte rendu de P. Galluzzi, «Galileo, Rosmini, Darwin : triumviri del cattolicesimo riformatore (1870-1918)», in Rivista di filosofia, vol. 113, 2022, n°3, pp. 489-495.