102,936 research outputs found
Time evolution of a Vlasov–Poisson plasma with different species and infinite mass in R3
No full textWe study existence and uniqueness of the solution to the Vlasov–Poisson system describing a plasma constituted by different species evolving in R3, whose particles interact via the Coulomb potential. The species can have both positive or negative charge. It is assumed that initially the particles are distributed according to a spatial density with a power-law decay in space, allowing for unbounded mass, and an exponential decay in velocities given by a Maxwell–Boltzmann law, extending a result contained in Caprino et al. (J Stat Phys 169:1066–1097,2017), which was restricted to finite total mass
On a microscopic model of viscous friction
No full textWe consider a body moving along the x-axis under the action of an external force E and immersed in an infinitely extended perfect gas. We assume the gas to be described by the mean-field approximation and interacting elastically with the body. In this setup, we discuss the following statement: "Let V-0 be the initial velocity of the body and V-infinity its asymptotic velocity, then for vertical bar V-0-V-infinity vertical bar small enough it results vertical bar V(t)-V infinity vertical bar approximate to Ct(-d-2) for t large, where V (t) is the velocity of the body at time t, d the dimension of the space and C is a positive constant depending on the medium and on the shape of the body". The reason for the power law approach to the stationary state instead of the exponential one (usually assumed in viscous friction problems), is due to the long memory of the dynamical system. In a recent paper by Caprino, Marchioro and Pulvirenti,(3) the case of E constant and positive, with 0 < V-0 < V-infinity, for a disk orthogonal to the x-axis has been discussed. Here we complete the analysis in the cases E > 0 with V-0 > V-infinity and E = 0. We also approach the problem of an x-dependent external force, by choosing E of harmonic type. In this case we obtain the power-like asymptotic time behavior for the body position X(t). The investigation is done in detail for a disk orthogonal to the x-axis and then, by a sketched proof, extended to a body with a general convex shape
C. Caprino, A. M. Colini, G. Gatti, M. Pallottino, P. Romanelli, La colonna di Marco Aurelio
No full textD. S. G. M. C. Caprino, A. M. Colini, G. Gatti, M. Pallottino, P. Romanelli, La colonna di Marco Aurelio. In: Bulletin de l'Association Guillaume Budé, n°2, juin 1957. pp. 99-100
Predicting Fatigue Lifetime of Glass Fibre-Reinforced Composites from Residual Strength Data
No full textMilano, Ital
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