871 research outputs found
A holomorphic representation of the Jacobi algebra
A representation of the Jacobi algebra by first order differential operators with polynomial
coefficients on the manifold is presented. The
Hilbert space of holomorphic functions on which the holomorphic first order
differential operators with polynomials coefficients act is constructed.Comment: 34 pages, corrected typos in accord with the printed version and the
Errata in Rev. Math. Phys. Vol. 24, No. 10 (2012) 1292001 (2 pages) DOI:
10.1142/S0129055X12920018, references update
Drag in a resonantly driven polariton fluid
We study the linear response of a coherently driven polariton fluid in the pump-only configuration scattering against a point-like defect and evaluate analytically the drag force exerted by the fluid on the defect. When the system is excited near the bottom of the lower polariton dispersion, the sign of the interaction-renormalised pump detuning classifies the collective excitation spectra into three different categories (Ciuti and Carusotto 2005 Phys. Status Solidi b 242 2224): linear for zero, diffusive-like for positive and gapped for negative detuning. We show that both cases of zero and positive detuning share a qualitatively similar crossover of the drag force from the subsonic to the supersonic regime as a function of the fluid velocity, with a critical velocity given by the speed of sound found for the linear regime. In contrast, for gapped spectra, we find that the critical velocity exceeds the speed of sound. In all cases, the residual drag force in the subcritical regime depends on the polariton lifetime only. Also, well below the critical velocity, the drag force varies linearly with the polariton lifetime, in agreement with previous work (Cancellieri et al 2010 Phys. Rev. B 82 224512), where the drag was determined numerically for a finite-size defect
A convenient coordinatization of Siegel-Jacobi domains
We determine the homogeneous K\"ahler diffeomorphism which expresses the
K\"ahler two-form on the Siegel-Jacobi ball \mc{D}^J_n=\C^n\times \mc{D}_n as
the sum of the K\"ahler two-form on \C^n and the one on the Siegel ball
\mc{D}_n. The classical motion and quantum evolution on \mc{D}^J_n
determined by a hermitian linear Hamiltonian in the generators of the Jacobi
group G^J_n=H_n\rtimes\text{Sp}(n,\R)_{\C} are described by a matrix Riccati
equation on \mc{D}_n and a linear first order differential equation in
z\in\C^n, with coefficients depending also on W\in\mc{D}_n. denotes
the -dimensional Heisenberg group. The system of linear differential
equations attached to the matrix Riccati equation is a linear Hamiltonian
system on \mc{D}_n. When the transform is
applied, the first order differential equation in the variable
\eta=(\un-W\bar{W})^{-1}(z+W\bar{z})\in\C^n becomes decoupled from the motion
on the Siegel ball. Similar considerations are presented for the Siegel-Jacobi
upper half plane \mc{X}^J_n=\C^n\times\mc{X}_n, where \mc{X}_n denotes the
Siegel upper half plane.Comment: 32 pages, corrected typos, Latex, amsart, AMS font
Identification of Berezin-Toeplitz deformation quantization
We give a complete identification of the deformation quantization which was
obtained from the Berezin-Toeplitz quantization on an arbitrary compact Kaehler
manifold. The deformation quantization with the opposite star-product proves to
be a differential deformation quantization with separation of variables whose
classifying form is explicitly calculated. Its characteristic class (which
classifies star-products up to equivalence) is obtained. The proof is based on
the microlocal description of the Szegoe kernel of a strictly pseudoconvex
domain given by Boutet de Monvel and Sjoestrand.Comment: 26 page
Vlasov moment flows and geodesics on the Jacobi group
By using the moment algebra of the Vlasov kinetic equation, we characterize
the integrable Bloch-Iserles system on symmetric matrices
(arXiv:math-ph/0512093) as a geodesic flow on the Jacobi group. We analyze the
corresponding Lie-Poisson structure by presenting a momentum map, which both
untangles the bracket structure and produces particle-type solutions that are
inherited from the Vlasov-like interpretation. Moreover, we show how the Vlasov
moments associated to Bloch-Iserles dynamics correspond to particular subgroup
inclusions into a group central extension (first discovered in
arXiv:math/0410100), which in turn underlies Vlasov kinetic theory. In the most
general case of Bloch-Iserles dynamics, a generalization of the Jacobi group
also emerges naturally.Comment: 45 page
The Geometry of Quantum Mechanics
A recent notion in theoretical physics is that not all quantum theories arise
from quantising a classical system. Also, a given quantum model may possess
more than just one classical limit. These facts find strong evidence in string
duality and M-theory, and it has been suggested that they should also have a
counterpart in quantum mechanics. In view of these developments we propose
"dequantisation", a mechanism to render a quantum theory classical.
Specifically, we present a geometric procedure to "dequantise" a given quantum
mechanics (regardless of its classical origin, if any) to possibly different
classical limits, whose quantisation gives back the original quantum theory.
The standard classical limit arises as a particular case of our
approach.Comment: 15 pages, LaTe
Dipolar degrees of freedom and Isospin equilibration processes in Heavy Ion collisions
Background: In heavy ion collision at the Fermi energies Isospin
equilibration processes occur- ring when nuclei with different charge/mass
asymmetries interacts have been investigated to get information on the
nucleon-nucleon Iso-vectorial effective interaction. Purpose: In this paper,
for the system 48Ca +27 Al at 40 MeV/nucleon, we investigate on this process by
means of an observable tightly linked to isospin equilibration processes and
sensitive in exclusive way to the dynamical stage of the collision. From the
comparison with dynamical model calculations we want also to obtain information
on the Iso-vectorial effective microscopic interaction. Method: The average
time derivative of the total dipole associated to the relative motion of all
emitted charged particles and fragments has been determined from the measured
charges and velocities by using the 4? multi-detector CHIMERA. The average has
been determined for semi- peripheral collisions and for different charges Zb of
the biggest produced fragment. Experimental evidences collected for the systems
27Al+48Ca and 27Al+40Ca at 40 MeV/nucleon used to support this novel method of
investigation are also discussed.Comment: Submitted for publication on Phys. Rev. C. 0n 24-oct-201
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