1,721,103 research outputs found
Dynamics with exotic symmetries
No full textInspired by the geometrical methods allowing the introduction of mechanical systems confined in the plane and endowed with exotic galilean symmetry, we resort to the Lagrange-Souriau 2-form formalism, in order to look for a wide class of 3D systems, involving not commuting and/or not canonical variables, but possessing geometric as well gauge symmetries in position and momenta space too. As a paradigmatic example, a charged particle simultaneously interacting with a magnetic monopole and a dual monopole in momenta space is considered. The main features of the motions, conservation laws and the analogies with the planar case are discussed. Possible physical realizations of the model are proposed
Finite amplitude electrostatic waves in magneto-active plasmas
No full textWeakly nonlinear dispersive longitudinal waves in an infinite homogeneous collisionless plasma in the presence of an external constant and uniform magnetic field are considered. Under specific physical assumptions and for an arbitrary three-dimensional envelope modulation of a plane wave, a purely differential system is derived. Taking into account the effect of wave-wave and wave-particle interaction, the evolution of the modulation is described by a modified nonlinear Schrödinger equation, coupled to the space perturbation charge densities. The generation of a static mode is described. As a particular case the electron waves are discussed and some special solutions, resorting to the theory of the perturbed solitions
Statistical Behavior of a Set of Uniformly Rotating Independent Particles with Random Frequencies
No full textA set of independent particles in uniform rotation, but with incommensurable frequencies, has behavior similar to that of a one-dimensional perfect gas, with constant internal energy. In fact, assuming that initially the particles are at the same point on the circle, they will quickly move to positions that are distributed with a uniform density. To verify this, we choose particles and randomly assign them frequencies within a certain range. Then we compute how many particles are located within a predetermined arc of our choice at each time step. Experimentally, we verify that the distribution of the points in the arc is very well approximated by the binomial distribution , which is characterized by the total number of particles and the parameter . The probability that all particles return to a configuration arbitrarily close to the initial one is equal to , which is negligible, if it is even possible (a Poincare's recurrence). For example, for frequencies between about and Hz, 15 particles may return to an arc of angle around the initial position in a time of the order of the age of the universe, years. In this Demonstration, you can observe density fluctuations in both space and time
Attivita' di orientamento del Corso di Laurea in Fisica
No full textCollocazione nell'ambito della formazione universitaria territoriale del Corso di Laurea in Fisica dell'Universita' di Lecce. Attivita' di orientamento in ingresso svolte dallo stesso Corso negli anni piu' recenti
Dynamics in Non-Commutative Spaces and Generalizations
No full textResorting to the Lagrange–Souriau 2-form formalism, a wide class of systems are derived in non-commuting and/or non-canonical variables, nor the Darboux theorem can be helpful, because of the gauge character of all phase-space variables. As a paradigmatic example, the motion of a charged particle in a magnetic monopole field in the presence of a momentum space monopole is considered
Exotic Galileian Group in Field Theory
No full textThe exotic Galileian group is realized as a symmetry group of a family of non relativistic field theories on the noncommutative plane. This has been obtained in a unique way consistent with the Seiberg-Witten map. The symmetry group of the free model is analyzed and a characterization of the class of the self-interacting theories has been given
`Continuum Approximation of the Fermi-Pasta-Ulam lattice
No full textViene studiata una approssimazione al continuo del reticolo di Fermi - Pasta - Ulam, con metodi di approssimazione di operatori alla Maslov. Si dimostra che nel limite continuo il sistema è riconducibile all'equazione di Korteweg - de Vries
Hamiltonian theory of anyons in crystals
No full textSemiclassical wave packets for electrons in crystals, subject to an external electromagnetic
field, satisfy Hamiltonian equations. In (2+1)-dimensions and in the limit of uniform fields, the symmetry
group results in a two-folded Galilei algebra, incorporating an “exotic” central charge. It has the physical meaning of the Berry-phase curvature. In the Hamiltonian scheme, we discuss possible deformations of
that algebra and the physical meaning
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