The semiclassical approximation for electron wave-packets in crystals leads to equations which can be derived from a Lagrangian or, under suitable regularity conditions, in a Hamiltonian framework. In the plane, these issues are studied using the method of the coadjoint orbit applied to the “enlarged” Galilei group.

Jacopo Grilli, ∗ Matteo Adorisio, Samir Suweis, Gyuri Barabás, Jayanth R. Banavar, Stefano Allesina, 4 and Amos Maritan Dept. of Ecology & Evolution, University of Chicago. Chicago, IL 60637, USA Dept. of Physics and Astronomy “Galileo Galilei”, Università degli Studi di Padova, Padova, Italy Department of Physics, University of Maryland, College Park, MD 20742, USA Computation Institute, Unive...

The “exotic” particle model associated with the two-parameter central extension of the planar Galilei group can be used to derive the ground states of the Fractional Quantum Hall Effect. Similar equations arise for a semiclassical Bloch electron. Exotic Galilean symmetry is also be shared by Chern-Simons field theory of the Moyal type.

With the help of contraction method we study the harmonic oscillator in spaces with degenerate metrics, namely, on Galilei plane and in the flat 3D Cayley-Klein spaces R 3 (j 2 , j 3). It is shown that the inner degrees of freedom are appeared which physical dimensions are different from the dimension of the space.

1 Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada, Spain, 2 INAF, Osservatorio Astronomico di Padova, Padova, Italy, 3 CONACYT Research Fellow, Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico, 4 Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico, 5 Dipartimento di Fisica Astronomia “Galileo Galilei”, University of...

What’s Behind Acoustic Peaks in the Cosmic Microwave Background Anisotropies C. Baccigalupi, A. Balbi, S. Matarrese, F. Perrotta , N. Vittorio SISSA/ISAS, Via Beirut 2-4, 34014 Trieste, Italy Dipartimento di Fisica, Università di Roma ‘Tor Vergata’ and INFN, Sezione di Roma II Dipartimento di Fisica ‘Galileo Galilei’, Università di Padova, and INFN, Sezione di Padova, via Marzolo 8, 35131 Padov...