arXiv subjects

Stefan Giller

Publications and source records attributed to Stefan Giller.

At least 19 recordsLinked to original sources

arXiv2023

The semiclassical states excitations in the multi-rectangular billiards

The problem of the quantizations of the $L$-shaped billiards and the like ones, i.e. each angle of which is equal to $π/2$ or $3π/2$, is considered using as a tool the Fourier series expansion method. The respective wave functions and the quantization conditions are written and discussed looking for and discussing about the superscars effects in such multi-rectangular billiards (MRB). It is found that a special set of POC modes effect the superscars phenomena in MRB in which the billiards are excited as a whole to the modes closest to the semiclassical ones existing in their approximated copies being MRB in which their parallel sides remain in rational relations between themselves.

quant-ph↗

arXiv2022

Wave Functions and Energy Spectra in Rational Billiards Are Determined Completely by Their Periods

The rational billiards (RB) are classically pseudointegrable, i.e. their trajectories in the phase space lie on multi-tori. Each such a multi-torus can be unfolded into elementary polygon pattern (EPP). A rational billiards Riemann surface (RBRS) corresponding to each RB is then an infinite mosaic made by a periodic distribution of EPP. Periods of RBRS are directly related to periodic orbits of RB. It is shown that any stationary solutions (SS) to the Schrödinger equation (SE) in RB can be extended on the whole RBRS. The extended stationary wave functions (ESS) are then periodic on RBRS with its periods. Conversely, for each system of boundary conditions (i.e. the Dirichlet or the the Neumann ones or their mixture) consistent with EPP one can find so called stationary pre-solutions (SPS) of the Schrödinger equation defined on RBRS and respecting its periodic structure together with their energy spectra. Using SPS one can easily construct SS of RB for most boundary conditions on it by a trivial algebra over SPS. It proves therefore that the energy spectra defined by the boundary conditions for SS corresponding to each RB are totally determined by $2g$ independent periods of RBRS being homogeneous functions of these periods. RBRS can be constructed exclusively due to the rationality of the polygon billiards considered. Therefore the approach developed in the present paper can be seen as a new way in obtaining SS to SE in RB. SPS can be constructed explicitly for a class of RB which EPP can be decomposed into a set of periodic orbit channel (POC) parallel to each other (POCDRB). For such a class of RB the respective RBRS can be built as a standard multi-sheeted Riemann surface with a periodic structure. For POCDRB a discussion of the existence of the superscar states (SSS) can be done thoroughly.

nlin.CD↗

arXiv2019

High energy semiclassical wave functions in rational multi-connected and other (Sinai-like) billiards determined by their periodic orbits

The methods of the high energy semiclassical quantization in the rational polygon billiards used in our earlier papers are generalized to an arbitrary rational multi-connected polygon billiards i.e. to the billiards which is a rational polygon with other rational polygons inside them "rotated" with respect to the "mother" ones by rational angles. The respective procedure is described fully and its most important aspects are discussed. This generalization allows us to apply the method to arbitrary billiards with curved boundaries and with multi-connected areas where the respective semiclassical quantization is determined by the shortest periodic orbits of the billiards. As an example of the latter case the Sinai-like billiards is considered which is the right angle triangle with one of its acute angles equal to $π/6$ and with the circular hole in it.

quant-ph↗

arXiv2018

High energy semiclassical wave functions in the Bunimovich stadium billiards determined by its periodic orbits

It is argued that the high energy semiclassical wave functions (SWF) in an arbitrary billiards can be built by approximating the billiards by a respective polygon one. The latter billiards is determined by a finite number of periodic orbits of the original one limited by their lengths beginning with the shortest ones and which are common for both the billiards. The phenomenon of scars and superscars (Heller, E.J., {\it Phys. Rev. Lett.} {\bf 53},(1984) 1515) are then naturally incorporated into such a construction being a limit of periodic orbit channels (POCs) considered by Bogomolny and Schmit ({\it Phys. Rev. Lett.} {\bf 92} (2004) 244102). The Bunimovich stadium billiards is considered as an example of such an approach.

math-ph↗

arXiv2017

Superscar states in rational polygon billiards - a reality or an illusion?

The superscars phenomena (Heller, E.J., Phys. Rev. Lett. 53, (1984) 1515) in the rational polygon billiards (RPB) are analysed using the high energy semiclassical wave functions (SWF) built on classical trajectories forming skeletons. Considering examples of the pseudointegrable billiards such as the Bogomolny-Schmit triangle, the parallelogram and the L-shape billiards as well as the integrable rectangular one the constructed SWFs allow us to verify the idea of Bogomolny and Schmit (Phys. Rev. Lett. 92 (2004) 244102) of SWFs (superscars) propagating along periodic orbit channels (POC) and vanishing outside of them. It is shown that the superscars effects in RPB appear as natural properties of SWFs built on the periodic skeletons. The latter skeletons are commonly present in RPB and are always composed of POCs. The SWFs built on the periodic skeletons satisfy all the basic principles of the quantum mechanics contrary to the superscar states of Bogomolny and Schmit which break them. Therefore the superscars effects need not to invoke the idea of the superscar states of Bogomolny and Schmit at least in the cases considered in our paper.

quant-ph↗

arXiv2014

Semiclassical wave functions and energy spectra in polygon billiards

A consistent scheme of semiclassical quantization in polygon billiards by wave function formalism is presented. It is argued that it is in the spirit of the semiclassical wave function formalism to make necessary rationalization of respective quantities accompanied the procedure of the semiclassical quantization in polygon billiards. Unfolding rational polygon billiards (RPB) into corresponding Riemann surfaces (RS) periodic structures of the latter are demonstrated with 2g independent periods on the respective multitori with g as their genuses. However it is the two dimensional real space of the real linear combinations of these periods which is used for quantizing RPB. A class of doubly rational polygon billiards (DRPB) is distinguished for which these real linear relations are rational and their semiclassical quantization by wave function formalism is presented. It is shown that semiclassical quantization of both the classical momenta and the energy spectra are determined completely by periodic structure of the corresponding RS. Each RS is then reduced to elementary polygon patterns (EPP) as its basic periodic elements. Each such EPP can be glued to a torus of genus g. Semiclassical wave functions (SWF) are then constructed on EPP. The SWF for DRPB appear to be exact. They satisfy the Dirichlet, the Neumannn or the mixed boundary conditions. Not every mixing is allowed however and a respective incompleteness of SWF is discussed. Dens families of DRPB are used for approximate semiclassical quantization of RPB. General rational polygons are quantized by approximating them by DRPB. An extension of the formalism to irrational polygons is described as well. The semiclassical approximations constructed in the paper are controlled by general criteria of the eigenvalue theory. A relation between the superscar solutions and SWF constructed in the paper is also discussed.

quant-ph↗

arXiv2013

Skeletons and superscars

Semiclassical wave functions in billiards based on the Maslov-Fedoriuk approach are constructed. They are defined on classical constructions called skeletons which are the billiards generalization of the Arnold tori. Skeletons in the rational polygon billiards considered in the phase space can be closed with a definite genus or can be open being a cylinder-like or Moebius-like bands. The skeleton formulation is applied to calculate semiclassical wave functions and the corresponding energy spectra for the integrable and pseudointegrable billiards as well as in the limiting forms in some cases of chaotic ones. The superscars of Bogomolny and Schmit are shown to be simply singular semiclassical solutions of the eigenvalue problem in the billiards well built on the singular skeletons in the billiards with flat boundaries in both the integrable and the pseudointegrable billiards as well as in the chaotic cases of such billiards.

math-ph↗

arXiv2011

Semiclassical wave functions in billiards built on classical trajectories. Energy quantization, scars and periodic orbits

A way of construction of semiclassical wave function (SWF) based on the Maslov - Fedoriuk approach is proposed which appears to be appropriate also for systems with chaotic classical limits. Some classical constructions called skeletons are considered. The skeletons are generalizations of Arnolds' tori able to gather chaotic dynamics. SWF's are continued by caustic singularities in the configuration space rather then in the phase space using complex time method. The skeleton formulation provides us with a new algorithm for the semiclassical approximation method which is applied to construct SWF's as well as to calculate energy spectra for the circular and rectangular billiards as well as to construct the simplest SWF's and the respective spectrum for the Bunimovich stadium. The scar phenomena are considered and a possibility of their description by the skeleton method is discussed. PACS number(s): 03.65.-w, 03.65.Sq, 02.30.Jr, 02.30.Lt, 02.30.Mv Key Words: Schrödinger equation, semiclassical expansion, Lagrange manifolds, classical trajectories, chaotic dynamics, quantum chaos, scars

math-ph↗

arXiv2008

The semiclassical small-$\hbar$ limit of loci of roots of fundamental solutions for polynomial potentials

In this paper a description of the small-$\hbar$ limit of loci of zeros of fundamental solutions for polynomial potentials is given. The considered cases of the potentials are bounded to the ones which provided us with simple turning points only. Among the latter potentials still several cases of Stokes graphs the potentials provide us with are distinguished, i.e. the general non-critical Stokes graphs, the general critical ones but with only single internal Stokes line and the Stokes graphs corresponding to arbitrary multiple-well real even degree polynomial potentials with internal Stokes lines distributed on the real axis only. All these cases are considered in their both versions of the quantized and not quantized $\hbar$. In particular due to the fact that the small-$\hbar$ limit is semiclassical it is shown that loci of roots of fundamental solutions in the cases considered are collected along Stokes lines. There are infinitely many roots of fundamental solutions on such lines escaping to infinity and a finite number of them on internal Stokes lines.

math-ph↗

arXiv2008

The high energy semiclassical asymptotics of loci of roots of fundamental solutions for polynomial potentials

In the case of polynomial potentials all solutions to 1-D Schroedinger equation are entire functions totally determined by loci of their roots and their behaviour at infinity. In this paper a description of the first of the two properties is given for fundamental solutions for the high complex energy limit when the energy is quantized or not. In particular due to the fact that the limit considered is semiclassical it is shown that loci of roots of fundamental solutions are collected of selected Stokes lines (called exceptional) specific for the solution considered and are distributed along these lines in a specific way. A stable asymptotic limit of loci of zeros of fundamental solutions on their exceptional Stokes lines has island forms and there are infintely many of such roots islands on exceptional Stokes lines escaping to infinity and a finite number of them on exceptional Stokes lines which connect pairs of turning points. The results obtained for asymptotic roots distributions of fundamental solutions in the semiclassical high (complex) energy limit are of a general nature for polynomial potentials.

math-ph↗

arXiv2003

Adiabatic limit interference effects for two energy level transition amplitudes and Nikitin - Umanskii formula studied by fundamental solution method

A method of fundamental solutions has been used to study adiabatic transition amplitudes in two energy level systems for a class of Hamiltonians allowing some simplifications of Stokes graphs corresponding to such transitions. It has been shown that for simplest such cases the amplitudes take the Nikitin - Umanskii form but for more complicated ones they are formed by a sum of terms strictly related to a structure of Stokes graph corresponding to such cases. This paper corrects our previous one [Phys. Rev. A, 63 052101 (2001)] and its results are in a full agreement with the ones of Joye, Mileti and Pfister [Phys. Rev. A, 44 4280 (1991)].

quant-ph↗

arXiv2001

Simple applications of fundamental solution method in 1D quantum mechanics A talk given at the conference on: "Geometry Symmetry and Mechanics I" Lisbon, 11-16 July 2001

A method of fundamental solutions has been used to show its effectiveness in solving some well known problems of 1D quantum mechanics (barrier penetrations, over-barrier reflections, resonance states), i.e. those in which we look for exponentially small contributions to semiclassical expansions for considered quantities. Its usefulness for adiabatic transitions in two energy level systems is also mentioned.

quant-ph↗

arXiv2001

Fundamental solution method applied to time evolution of two energy level systems: exact and adiabatic limit results

A method of fundamental solutions has been used to investigate transitions in two energy level systems with no level crossing in a real time. Compact formulas for transition probabilities have been found in their exact form as well as in their adiabatic limit. No interference effects resulting from many level complex crossings as announced by Joye, Mileti and Pfister (Phys. Rev. {\bf A44} 4280 (1991)) have been detected in either case. It is argued that these results of this work are incorrect. However, some effects of Berry's phases are confirmed.

quant-ph↗

arXiv2000

Borel Summable Solutions to 1D Schrödinger Equation

It is shown that so called fundamental solutions the semiclassical expansions of which have been established earlier to be Borel summable to the solutions themselves appear also to be the unique solutions to the 1D Schrödinger equation having this property. Namely, it is shown in this paper that for the polynomial potentials the Borel function defined by the fundamental solutions can be considered as the canonical one. The latter means that any Borel summable solution can be obtained by the Borel transformation of this unique canonical Borel function multiplied by some $\hbar$-dependent and Borel summable constant. This justify the exceptional role the fundamental solutions play in 1D quantum mechanics and completes the relevant semiclassical theory relied on the Borel resummation technique and developed in our other papers.

quant-ph↗

arXiv1999

Topological Expansion and Exponential Asymptotics in 1D Quantum Mechanics

Borel summable semiclassical expansions in 1D quantum mechanics are considered. These are the Borel summable expansions of fundamental solutions and of quantities constructed with their help. An expansion, called topological,is constructed for the corresponding Borel functions. Its main property is to order the singularity structure of the Borel plane in a hierarchical way by an increasing complexity of this structure starting from the analytic one. This allows us to study the Borel plane singularity structure in a systematic way. Examples of such structures are considered for linear, harmonic and anharmonic potentials. Together with the best approximation provided by the semiclassical series the exponentially small contribution completing the approximation are considered. A natural method of constructing such an exponential asymptotics relied on the Borel plane singularity structures provided by the topological expansion is developed. The method is used to form the semiclassical series including exponential contributions for the energy levels of the anharmonic oscillator.

quant-ph↗

arXiv1998

Change of Variable as Borel Resummation of Semiclassical Series

It is shown that a change of variable in 1-dim Schroedinger equation applied to the Borel summable fundamental solutions [Giller] is equivalent to Borel resummation of the fundamental solutions multiplied by suitably chosen $\hbar$-dependent constant. This explains why change of variable can improve JWKB formulae [Giller, Milczarski]. It is shown also that a change of variable alone cannot provide us with the exact JWKB formulae.

quant-ph↗

arXiv1997

Rectangular Well as Perturbation

We discuss a finite rectangular well as a perturbation for the infinite one with a depth $λ^2$ of the former as a perturbation parameter. In particular we consider a behaviour of energy levels in the well as functions of complex $λ$. It is found that all the levels of the same parity are defined on infinitely sheeted Riemann surfaces which topological structures are described in details. These structures differ considerably from those found in models investigated earlier. It is shown that perturbation series for all the levels converge what is in contrast with the known results of Bender and Wu. The last property is shown to hold also for the finite rectangular well with Dirac delta barier as a perturbation considered earlier by Ushveridze.

quant-ph↗

arXiv1997

spl(p,q) superalgebra and differential operators

Series of finite dimensional representations of the superalgebras spl(p,q) can be formulated in terms of linear differential operators acting on a suitable space of polynomials. We sketch the general ingredients necessary to construct these representations and present examples related to spl(2,1) and spl(2,2). By revisiting the products of projectivised representations of sl(2), we are able to construct new sets of differential operators preserving some space of polynomials in two or more variables. In particular, this allows to express the representation of spl(2,1) in terms of matrix differential operators in two variables. The corresponding operators provide the building blocks for the construction of quasi exactly solvable systems of two and four equations in two variables. We also present a quommutator deformation of spl(2,1) which, by construction, provides an appropriate basis for analyzing the quasi exactly solvable systems of finite difference equations.

q-alg↗