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Ahmed Jellal

Publications and source records attributed to Ahmed Jellal.

179 records · Page 10Linked to original sources
arXiv2007

Effective Wess-Zumino-Witten Action for Edge States of Quantum Hall Systems on Bergman Ball

Using a group theory approach, we investigate the basic features of the Landau problem on the Bergman ball {\bf B}^k. This can be done by considering a system of particles living on {\bf B}^k in the presence of an uniform magnetic field B and realizing the ball as the coset space SU(k,1)/U(k). In quantizing the theory on {\bf{B}}^k, we define the wavefunctions as the Wigner \cal{D}-functions satisfying a set of suitable constraints. The corresponding Hamiltonian is mapped in terms of the right translation generators. In the lowest Landau level, we obtain the wavefunctions as the SU(k,1) coherent states. This are used to define the star product, density matrix and excitation potential in higher dimensions. With these ingredients, we construct a generalized effective Wess-Zumino-Witten action for the edge states and discuss their nature.

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arXiv2007

Thermodynamical Properties of Hall Systems

We study quantum Hall effect within the framework of a newly proposed approach, which captures the principal results of some proposals. This can be established by considering a system of particles living on the non-commutative plane in the presence of an electromagnetic field and quantum statistical mechanically investigate its basic features. Solving the eigenvalue equation, we analytically derive the energy levels and the corresponding wavefunctions. These will be used, at low temperature and weak electric field, to determine the thermodynamical potential Ω^{nc} and related physical quantities. Varying Ω^{nc} with respect to the non-commutativity parameter θ, we define a new function that can be interpreted as a Ω^{nc} density. Evaluating the particle number, we show that the Hall conductivity of the system is θ-dependent. This allows us to make contact with quantum Hall effect by offering different interpretations. We study the high temperature regime and discuss the magnetism of the system. We finally show that at θ=2l_B^2, the system is sharing some common features with the Laughlin theory.

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arXiv2005

Quantum Hall Effect on Higher Dimensional Spaces

We analysis the quantum Hall effect exhibited by a system of particles moving in a higher dimensional space. This can be done by considering particles on the Bergman ball {\bb{B}_ρ^d} of radius ρin the presence of an external magnetic field B and investigate its basic features. Solving the corresponding Hamiltonian to get the energy levels as well as the eigenfunctions. This can be used to study quantum Hall effect of confined particles in the lowest Landau level where density of particles and two point functions are calculated. We take advantage of the symmetry group of the Hamiltonian on {\bb{B}_ρ^d} to make link to the Landau problem analysis on the complex projective spaces CP^d. In the limit ρ\lga\infty, our analysis coincides with that corresponding to particles on the flat geometry {\bb{C}^d}. This task has been done for d=1, 2 and finally for the generic case, i.e. d \geq 3.

hep-th↗
arXiv2004

Supersymmetric Embedding of the Quantum Hall Matrix Model

We develop a supersymmetric extension of the Susskind-Polychronakos matrix theory for the quantum Hall fluids. This is done by considering a system combining two sets of different particles and using both a component field method as well as world line superfields. Our construction yields a class of models for fractional quantum Hall systems with two phases U and D involving, respectively $N_1$ bosons and $N_2$ fermions. We build the corresponding supersymmetric matrix action, derive and solve the supersymmetric generalization of the Susskind-Polychronakos constraint equations. We show that the general U(N) gauge invariant solution for the ground state involves two configurations parameterized by the bosonic contribution $k_{1}$ (integer) and in addition a new degree of freedom $k_{2}$, which is restricted to 0 and 1. We study in detail the two particular values of $k_{2}$ and show that the classical (Susskind) filling factor $ν$ receives no quantum correction. We conclude that the Polychronakos effect is exactly compensated by the opposite fermionic contributions.

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arXiv2004

A Matrix Model for Bilayered Quantum Hall Systems

We develop a matrix model to describe bilayered quantum Hall fluids for a series of filling factors. Considering two coupling layers, and starting from a corresponding action, we construct its vacuum configuration at ν=q_iK_{ij}^{-1}q_j, where K_{ij} is a 2\times 2 matrix and q_i is a vector. Our model allows us to reproduce several well-known wave functions. We show that the wave function Ψ_{(m,m,n)} constructed years ago by Yoshioka, MacDonald and Girvin for the fractional quantum Hall effect at filling factor {2\over m+n} and in particular Ψ_{(3,3,1)} at filling {1\over 2} can be obtained from our vacuum configuration. The unpolarized Halperin wave function and especially that for the fractional quantum Hall state at filling factor {2\over 5} can also be recovered from our approach. Generalization to more than 2 layers is straightforward.

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arXiv2003

Two Coupled Harmonic Oscillators on Non-commutative Plane

We investigate a system of two coupled harmonic oscillators on the non-commutative plane \RR^2_θ by requiring that the spatial coordinates do not commute. We show that the system can be diagonalized by a suitable transformation, i.e. a rotation with a mixing angle α. The obtained eigenstates as well as the eigenvalues depend on the non-commutativity parameter θ. Focusing on the ground state wave function before the transformation, we calculate the density matrix ρ_0(θ) and find that its traces {\rm Tr}(ρ_{0}(θ)) and {\rm Tr}(ρ_0^2(θ)) are not affected by the non-commutativity. Evaluating the Wigner function on \RR^2_θ confirms this. The uncertainty relation is explicitly determined and found to depend on θ. For small values of θ, the relation is shifted by a θ^2 term, which can be interpreted as a quantum correction. The calculated entropy does not change with respect to the normal case. We consider the limits α=1 and α={π\over 2}. In first case, by identifying θto the squared magnetic length, one can recover basic features of the Hall system.

hep-th↗
arXiv2003

Anisotropic Quantum Hall Matrix Model

We consider the anisotropic effect in the quantum Hall systems by applying a confining potential that is not of parabolic type. This can be done by extending Susskind--Polychronakos's approach to involve the matrices of two coupled harmonic oscillators. Starting from its action, we employ a unitary transformation to diagonalize the model. The operators for building up the anisotropic ground state and creating the collective excitations can be constructed explicitly. Evaluating the area of the quantum Hall droplet, we obtain the corresponding filling factor which is found to depend on the anisotropy parameter and to vary with the magnetic field strength. This can be used to obtain the observed anisotropic filling factors, i.e. {9\over 2}, {11\over 2} and others.

hep-th↗
arXiv2003

Noncommutativity Parameter and Composite Fermions

We determine some particular values of the noncommutativity parameter θand show that the Murthy-Shankar approach is in fact a particular case of a more general one. Indeed, using the fractional quantum Hall effect (FQHE) experimental data, we give a measurement of θ. This measurement can be obtained by considering some values of the filling factor νand other ingredients, magnetic field B and electron density ρ. Moreover, it is found that θcan be quantized either fractionally or integrally in terms of the magnetic length l_0 and the quantization is exactly what Murthy and Shankar formulated recently for the FQHE. On the other hand, we show that the mapping of the FQHE in terms of the composite fermion basis has a noncommutative geometry nature and therefore there is a more general way than the Murthy-Shankar method to do this mapping.

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arXiv2003

A Matrix Model for ν_{k_1k_2}=\frac{k_1+k_2}{k_1 k_2} Fractional Quantum Hall States

We propose a matrix model to describe a class of fractional quantum Hall (FQH) states for a system of (N_1+N_2) electrons with filling factor more general than in the Laughlin case. Our model, which is developed for FQH states with filling factor of the form ν_{k_1k_2}=\frac{k_1+k_2}{k_1k_2} (k_1 and k_2 odd integers), has a U(N_1)\times U(N_2) gauge invariance, assumes that FQH fluids are composed of coupled branches of the Laughlin type, and uses ideas borrowed from hierarchy scenarios. Interactions are carried, amongst others, by fields in the bi-fundamentals of the gauge group. They simultaneously play the role of a regulator, exactly as does the Polychronakos field. We build the vacuum configurations for FQH states with filling factors given by the series ν_{p_1p_2}=\frac{p_2}{p_1p_2-1}, p_1 and p_2 integers. Electrons are interpreted as a condensate of fractional D0-branes and the usual degeneracy of the fundamental state is shown to be lifted by the non-commutative geometry behaviour of the plane. The formalism is illustrated for the state at ν={2/5}.

hep-th↗
arXiv2003

Second Virial Coefficient for Noncommutative Space

The second virial coefficient $B_{2}^{nc}(T)$ for non-interacting particles moving in a two-dimensional noncommutative space and in the presence of a uniform magnetic field $\vec B$ is presented. The noncommutativity parameter $\te$ can be chosen such that the $B_{2}^{nc}(T)$ can be interpreted as the second virial coefficient for anyons of statistics $\al$ in the presence of $\vec B$ and living on the commuting plane. In particular in the high temperature limit $\be\lga 0$, we establish a relation between the parameter $\te$ and the statistics $\al$. Moreover, $B_{2}^{nc}(T)$ can also be interpreted in terms of composite fermions.

hep-th↗
arXiv2002

Electrons-Holes on Noncommutative Plane and Hall Effect

By considering N_e-electrons and N_h-holes together in uniform external magnetic and electric fields, we end up with a total Hall conductivity σ_{H}^{tot}, which is depending to the difference between N_e and N_h and becomes null when N_e=N_h. Dealing with the same system but requiring that the coordinates of plane are noncommuting, we obtain a new Hall conductivity σ_{H}^{(tot,nc)}. In the limit N_e=N_h, we find that σ_{H}^{(tot,nc)} is only noncommutativity parameters θ_i-dependent, which means that theoretically it is possible to have Hall effect without B. Moreover, at the critical points θ_e=l^2 and θ_h=-l^2, we find that σ_{H}^{(tot,nc)} becomes two times the usual Hall conductivity for an noninteracting mixing system.

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arXiv2001

Coherent States for Generalized Laguerre Functions

We explicitly construct a Hamiltonian whose exact eigenfunctions are the generalized Laguerre functions. Moreover, we present the related raising and lowering operators. We investigate the corresponding coherent states by adopting the Gazeau-Klauder approach, where resolution of unity and overlapping properties are examined. Coherent states are found to be similar to those found for a particle trapped in a Pöschl-Teller potential of the trigonometric type. Some comparisons with Barut-Girardello and Klauder-Perelomov methods are noticed.

hep-th↗
arXiv2001

Orbital Magnetism of Two-Dimension Noncommutative Confined System

We study a system of spinless electrons moving in a two dimensional noncommutative space subject to a perpendicular magnetic field $\vec B$ and confined by a harmonic potential type ${1\over 2}mw_{0}r^2$. We look for the orbital magnetism of the electrons in different regimes of temperature $T$, magnetic field $\vec B$ and noncommutative parameter $\te$. We prove that the degeneracy of Landau levels can be lifted by the $\te$-term appearing in the electron energy spectrum at weak magnetic field. Using the {\it Berezin-Lieb} inequalities for thermodynamical potential, it is shown that in the high temperature limit, the system exibits a magnetic $\te$-dependent behaviour, which is missing in the commutative case. Moreover, a correction to susceptibility at low $T$ is observed. Using the {\it Fermi-Dirac} trace formulas, a generalization of the thermodynamical potential, the average number of electrons and the magnetization is obtained. There is a critical point where the thermodynamical potential becomes infinite in both of two methods above. So at this point we deal with the partition function by adopting another approach. The standard results in the commutative case for this model can be recovered by switching off the $\te$-parameter.

hep-th↗
arXiv2000

Graded q-pseudo-differential Operators and Supersymmetric Algebras

We give a supersymmetric generalization of the sine algebra and the quantum algebra $U_{t}(sl(2))$. Making use of the $q$-pseudo-differential operators graded with a fermionic algebra, we obtain a supersymmetric extension of sine algebra. With this scheme we also get a quantum superalgebra $U_{t}(sl(2/1)$.

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arXiv2000

Thermodynamic Properties of a Quantum Group Boson Gas $GL_{p,q}(2)$

An approach is proposed enabling to effectively describe the behaviour of a bosonic system. The approach uses the quantum group $GL_{p,q}(2)$ formalism. In effect, considering a bosonic Hamiltonian in terms of the $GL_{p,q}(2)$ generators, it is shown that its thermodynamic properties are connected to deformation parameters $p$ and $q$. For instance, the average number of particles and the pressure have been computed. If $p$ is fixed to be the same value for $q$, our approach coincides perfectly with some results developed recently in this subject. The ordinary results, of the present system, can be found when we take the limit $p=q=1$.

hep-th↗
arXiv2000

D-dimensional Ideal Quantum Gases in $Ar^{n}+Br^{-n}$ Potential

The paper is concerned with thermostatistics of both $D$-dimensional Bose and Fermi ideal gases in a confining potential of type $Ar^{n}+Br^{-n}$. The investigation is performed in the framework of the semiclassical approximation. Some physical quantities for such systems are derived, like density of states, density profiles and number of particles. Bose-Einstein condensation (BEC) is discussed in the high and low temperature regimes.

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