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P. Stovicek

Publications and source records attributed to P. Stovicek.

32 records · Page 2Linked to original sources
arXiv2001

Quantization of kinematics on configuration manifolds

The review is devoted to topological global aspects of quantal description. The treatment concentrates on quantizations of kinematical observables --- generalized positions and momenta. A broad class of quantum kinematics is rigorously constructed for systems, the configuration space of which is either a homogeneous space of a Lie group or a connected smooth finite-dimensional manifold without boundary. The class also includes systems in an external gauge field for an Abelian or a compact gauge group. Conditions for equivalence and irreducibility of generalized quantum kinematics are investigated with the aim of classification of possible quantizations. Complete classification theorems are given in two special cases. It is attempted to motivate the global approach based on a generalization of imprimitivity systems called {\em quantum Borel kinematics}. These are classified by means of global invariants --- quantum numbers of topological origin. Selected examples are presented which demonstrate the richness of applications of Borel quantization. The review aims to provide an introductory survey of the subject and to be sufficiently selfcontained as well, so that it can serve as a standard reference concerning Borel quantization for systems admitting localization on differentiable manifolds.

math-ph↗
arXiv2001

Weakly regular Floquet Hamiltonians with pure point spectrum

We study the Floquet Hamiltonian: -i omega d/dt + H + V(t) as depending on the parameter omega. We assume that the spectrum of H is discrete, {h_m (m = 1..infinity)}, with h_m of multiplicity M_m. and that V is an Hermitian operator, 2pi-periodic in t. Let J > 0 and set Omega_0 = [8J/9,9J/8]. Suppose that for some sigma > 0: sum_{m,n such that h_m > h_n} mu_{mn}(h_m - h_n)^(-sigma) < infinity where mu_{mn} = sqrt(min{M_m,M_n)) M_m M_n. We show that in that case there exist a suitable norm to measure the regularity of V, denoted epsilon, and positive constants, epsilon_* & delta_*, such that: if epsilon < epsilon_* then there exists a measurable subset |Omega_infinity| > |Omega_0| - delta_* epsilon and the Floquet Hamiltonian has a pure point spectrum for all omega in Omega_infinity.

math-ph↗
arXiv1999

Several remarks on ``Comments'' by A. Moroz

We make a couple of remarks on ``Comments'' due to A. Moroz which were addressed to our recent letter "Differential cross section for Aharonov-Bohm effect with non standard boundary conditions", Europhys. Lett. 44 (1998) 403.

quant-ph↗
arXiv1998

A construction of representations and quantum homogeneous spaces

A simplified construction of representations is presented for the quantized enveloping algebra Uq(g), with g being a simple complex Lie algebra belonging to one of the four principal series A, B, C or D. The carrier representation space is the quantized algebra of polynomials in antiholomorphic coordinate functions on the big cell of a coadjoint orbit of K where K is the compact simple Lie group with the Lie algebra g - the compact form of g.

math.QA↗
arXiv1998

About a resolvent formula

A resolvent formula, originally presented by Karner in his habilitation, is discussed. First the formula is considered abstractly and then it is demonstrated on an explicit example -- the so called simplified Fermi accelerator.

math-ph↗
arXiv1997

Perturbation of an eigenvalue from a dense point spectrum: a general Floquet Hamiltonian

We consider a perturbed Floquet Hamiltonian $-i\partial_t + H + βV(ωt)$ in the Hilbert space $L^2([0,T],E,dt)$. Here $H$ is a self-adjoint operator in $E$ with a discrete spectrum obeying a growing gap condition, $V(t)$ is a symmetric bounded operator in $E$ depending on $t$ $2π$-periodically, $ω= 2π/T$ is a frequency and $β$ is a coupling constant. The spectrum $Spec(-i\partial_t + H)$ of the unperturbed part is pure point and dense in $R$ for almost every $ω$. This fact excludes application of the regular perturbation theory. Nevertheless we show, for almost all $ω$ and provided $V(t)$ is sufficiently smooth, that the perturbation theory still makes sense, however, with two modifications. First, the coupling constant is restricted to a set $I$ which need not be an interval but 0 is still a point of density of $I$. Second, the Rayleigh-Schrodinger series are asymptotic to the perturbed eigen-value and the perturbed eigen-vector.

math-ph↗
arXiv1997

Perturbation of an Eigen-Value from a Dense Point Spectrum : An Example

We study a perturbed Floquet Hamiltonian $K+βV$ depending on a coupling constant $β$. The spectrum $σ(K)$ is assumed to be pure point and dense. We pick up an eigen-value, namely $0\inσ(K)$, and show the existence of a function $λ(β)$ defined on $I\subset\R$ such that $λ(β) \in σ(K+βV)$ for all $β\in I$, 0 is a point of density for the set $I$, and the Rayleigh-Schrödinger perturbation series represents an asymptotic series for the function $λ(β)$. All ideas are developed and demonstrated when treating an explicit example but some of them are expected to have an essentially wider range of application.

quant-ph↗
arXiv1996

Aharonov-Bohm Effect with $δ$--type Interaction

A quantum particle interacting with a thin solenoid and a magnetic flux is described by a five-parameter family of Hamilton operators, obtained via the method of self-adjoint extensions. One of the parameters, the value of the flux, corresponds to the Aharonov-Bohm effect; the other four parameters correspond to the strength of a singular potential barrier. The spectrum and eigenstates are computed and the scattering problem is solved.

math-ph↗
arXiv1996

Representations of $U_h(su(N))$ derived from quantum flag manifolds

A relationship between quantum flag and Grassmann manifolds is revealed. This enables a formal diagonalization of quantum positive matrices. The requirement that this diagonalization defines a homomorphism leads to a left \Uh -- module structure on the algebra generated by quantum antiholomorphic coordinate functions living on the flag manifold. The module is defined by prescribing the action on the unit and then extending it to all polynomials using a quantum version of Leibniz rule. Leibniz rule is shown to be induced by the dressing transformation. For discrete values of parameters occuring in the diagonalization one can extract finite-dimensional irreducible representations of \Uh as cyclic submodules.

q-alg↗
arXiv1995

Antiholomorphic representations for orthogonal and symplectic quantum groups

The coadjoint orbits for the series $B_l,\ C_l$ and $D_l$ are considered in the case when the base point is a multiple of a fundamental weight. A quantization of the big cell is suggested by means of introducing a $\ast$-algebra generated by holomorphic coordinate functions. Starting from this algebraic structure the irreducible representations of the deformed universal enveloping algebra are derived as acting in the vector space of polynomials in quantum coordinate functions.

q-alg↗
arXiv1994

Coherent States for Quantum Compact Groups

Coherent states are introduced and their properties are discussed for all simple quantum compact groups. The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit and interpret the coherent state as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R--matrix formulation (generalizing this way the $q$--deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel--Weil construction) are described using the concept of coherent state. The relation between representation theory and non--commutative differential geometry is suggested.}

hep-th↗