arXiv subjects

A. Ludu

Publications and source records attributed to A. Ludu.

23 records · Page 2Linked to original sources

arXiv2000

Soliton excitations as emitted clusters on nuclear surfaces

This work reports on calculations of the deformation energy of a nucleus plus an emitted cluster as a soliton moving on its surface. The potential barrier against the emission of a soliton is calculated within the macroscopic-microscopic method. The outer turning point of the barrier determines limitations on the geometrical and kinematical parameters for the formation of a surface soliton. For large asymmetry, the two-center shell model is used to assign a structure to the soliton. Calculations for $^{248}$N\lowercase{o} with the emission of a $^{40}$C\lowercase{a} soliton are reported; likewise for $^{224}$T\lowercase{h} with the emission of $^{16}$O. Except for necked shapes at the very first stages of soliton formation, the greatest portion of the deformation path displays rather compact configurations with large neck radii. These shape sequences correspond to allowable soliton velocities. Close to and just beyond the touching point configuration, where the shape becomes concave, the width and the velocity of the soliton approach zero. The calculations suggest that the emission of a $^{40}$C\lowercase{a} structure is quite probable due to a low potential barrier, whereas the emission of an $^{16}$O type soliton is rather unlikely due to the higher penetration barrier.

nucl-th↗

arXiv1997

Nonlinear deformed su(2) algebras involving two deforming functions

The most common nonlinear deformations of the su(2) Lie algebra, introduced by Polychronakos and Ro\v cek, involve a single arbitrary function of J_0 and include the quantum algebra su_q(2) as a special case. In the present contribution, less common nonlinear deformations of su(2), introduced by Delbecq and Quesne and involving two deforming functions of J_0, are reviewed. Such algebras include Witten's quadratic deformation of su(2) as a special case. Contrary to the former deformations, for which the spectrum of J_0 is linear as for su(2), the latter give rise to exponential spectra, a property that has aroused much interest in connection with some physical problems. Another interesting algebra of this type, denoted by ${\cal A}^+_q(1)$, has two series of (N+1)-dimensional unitary irreducible representations, where N=0, 1, 2, .... To allow the coupling of any two such representations, a generalization of the standard Hopf axioms is proposed. The resulting algebraic structure, referred to as a two-colour quasitriangular Hopf algebra, is described.

q-alg↗

arXiv1997

A nonlinear deformed su(2) algebra with a two-colour quasitriangular Hopf structure

Nonlinear deformations of the enveloping algebra of su(2), involving two arbitrary functions of J_0 and generalizing the Witten algebra, were introduced some time ago by Delbecq and Quesne. In the present paper, the problem of endowing some of them with a Hopf algebraic structure is addressed by studying in detail a specific example, referred to as ${\cal A}^+_q(1)$. This algebra is shown to possess two series of (N+1)-dimensional unitary irreducible representations, where N=0, 1, 2, .... To allow the coupling of any two such representations, a generalization of the standard Hopf axioms is proposed by proceeding in two steps. In the first one, a variant and extension of the deforming functional technique is introduced: variant because a map between two deformed algebras, su_q(2) and ${\cal A}^+_q(1)$, is considered instead of a map between a Lie algebra and a deformed one, and extension because use is made of a two-valued functional, whose inverse is singular. As a result, the Hopf structure of su_q(2) is carried over to ${\cal A}^+_q(1)$, thereby endowing the latter with a double Hopf structure. In the second step, the definition of the coproduct, counit, antipode, and R-matrix is extended so that the double Hopf algebra is enlarged into a new algebraic structure. The latter is referred to as a two-colour quasitriangular Hopf algebra because the corresponding R-matrix is a solution of the coloured Yang-Baxter equation, where the `colour' parameters take two discrete values associated with the two series of finite-dimensional representations.

q-alg↗

arXiv1996

Complex su_q(2) Dynamical Symmetry, Limiting Cases and 1-Dimensional Potential Realisation

Using a complex deformation q=exp(is) of su(2) we obtain extensions of the finite-dimensional representations towards the infinite-dimensional ones. A generalised q-deformation of su(2), as a Hopf algebra is introduced. We present the corresponding Schrodinger picture, by using a differential realisation, and a large class of potentials is obtained.A connection between the unirreps with q a root of unity and the comensurability of the potentials is investigated. The smooth transition between su(2) and su(1,1) , through E(1) is obtained at different levels: of the unirreps, of the topology, of the commutators and of the potentials in the corresponding Schrodinger equation.

q-alg↗

arXiv1996

Generalized KdV Equation for Fluid Dynamics and Quantum Algebras

We generalize the non-linear one-dimensional equation of a fluid layer for any depth and length as an infinite order differential equation for the steady waves. This equation can be written as a q-differential one, with its general solution written as a power series expansion with coefficients satisfying a nonlinear recurrence relation. In the limit of long and shallow water (shallow channels) we reobtain the well known Korteweg-de-Vries equation together with its single-soliton solution.

q-alg↗