Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates

Recently we proposed a generic construction of the additional integrals of motion for the Stäckel systems applying addition theorems to the angle variables. In this note we show some trivial examples associated with angle variables for elliptic and parabolic coordinate systems on the plane.

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Дата:2012
Автор: Tsiganov, A.V.
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Опубліковано: Інститут математики НАН України 2012
Назва видання:Symmetry, Integrability and Geometry: Methods and Applications
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Цитувати:Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates / A.V. Tsiganov // Symmetry, Integrability and Geometry: Methods and Applications. — 2012. — Т. 8. — Бібліогр.: 15 назв. — англ.

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spelling irk-123456789-1484702019-02-19T01:31:06Z Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates Tsiganov, A.V. Recently we proposed a generic construction of the additional integrals of motion for the Stäckel systems applying addition theorems to the angle variables. In this note we show some trivial examples associated with angle variables for elliptic and parabolic coordinate systems on the plane. 2012 Article Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates / A.V. Tsiganov // Symmetry, Integrability and Geometry: Methods and Applications. — 2012. — Т. 8. — Бібліогр.: 15 назв. — англ. 1815-0659 2010 Mathematics Subject Classification: 37J35; 70H06 DOI: http://dx.doi.org/10.3842/SIGMA.2012.031 http://dspace.nbuv.gov.ua/handle/123456789/148470 en Symmetry, Integrability and Geometry: Methods and Applications Інститут математики НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description Recently we proposed a generic construction of the additional integrals of motion for the Stäckel systems applying addition theorems to the angle variables. In this note we show some trivial examples associated with angle variables for elliptic and parabolic coordinate systems on the plane.
format Article
author Tsiganov, A.V.
spellingShingle Tsiganov, A.V.
Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
Symmetry, Integrability and Geometry: Methods and Applications
author_facet Tsiganov, A.V.
author_sort Tsiganov, A.V.
title Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
title_short Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
title_full Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
title_fullStr Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
title_full_unstemmed Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates
title_sort superintegrable stäckel systems on the plane: elliptic and parabolic coordinates
publisher Інститут математики НАН України
publishDate 2012
url http://dspace.nbuv.gov.ua/handle/123456789/148470
citation_txt Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates / A.V. Tsiganov // Symmetry, Integrability and Geometry: Methods and Applications. — 2012. — Т. 8. — Бібліогр.: 15 назв. — англ.
series Symmetry, Integrability and Geometry: Methods and Applications
work_keys_str_mv AT tsiganovav superintegrablestackelsystemsontheplaneellipticandparaboliccoordinates
first_indexed 2025-07-12T19:33:21Z
last_indexed 2025-07-12T19:33:21Z
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fulltext Symmetry, Integrability and Geometry: Methods and Applications SIGMA 8 (2012), 031, 9 pages Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates? Andrey V. TSIGANOV St. Petersburg State University, St. Petersburg, Russia E-mail: andrey.tsiganov@gmail.com Received April 10, 2012, in final form May 21, 2012; Published online May 25, 2012 http://dx.doi.org/10.3842/SIGMA.2012.031 Abstract. Recently we proposed a generic construction of the additional integrals of motion for the Stäckel systems applying addition theorems to the angle variables. In this note we show some trivial examples associated with angle variables for elliptic and parabolic coordinate systems on the plane. Key words: integrability; superintegrability; separation of variables; Abel equations; addi- tion theorems 2010 Mathematics Subject Classification: 37J35; 70H06 1 Introduction In classical mechanics Hamiltonian system on a 2n-dimensional phase space M is called com- pletely integrable in Liouville’s sense if it possesses n functionally independent integrals of motion H1, . . . ,Hn in involution: dHi dt = {H,Hi} = 0, {Hi, Hj} = 0, i, j = 1, . . . , n, where H = H1 is the Hamilton function and {·, ·} is the Poisson bracket on M . Superintegrable system is a system that is integrable in the Liouville sense and that possesses more functionally independent integrals of motion than degrees of freedom. The construction of superintegrable Stäckel systems using angle variables ωk has been proposed in [12, 13, 14, 15]. In generic case the action variables ωk are multi-valued functions on the whole phase space M . In fact, we can extract polynomial integrals of motion from angle variables only when we can apply addition theorems to the corresponding Abelian integrals. As there are only few addition theorems for the Abel equations [1, 3] we can easily classify the corresponding superintegrable systems, see [12, 13, 14, 15]. The goal of this brief note is to present some trivial examples of applying this generic theory associated with elliptic and parabolic coordinate systems on the plane. Superintegrable systems separable in spherical coordinates can be found in [2, 6]. The corresponding addition integrals of motion are related with an addition theorem for the logarithmic angle variables. Of course, there is a trivial generalization of the proposed method for all the orthogonal coordinate systems in R3 (ellipsoidal, paraboloidal, cylindrical, prolate and oblate spheroidal coordinates etc). The non-Stäckel superintegrable systems in classical and quantum mechanics have been con- sidered in [7, 9]. In contrast with the Stäckel case we do not have a generic theory for constructing such superintegrable systems. ?This paper is a contribution to the Special Issue “Superintegrability, Exact Solvability, and Special Functions”. The full collection is available at http://www.emis.de/journals/SIGMA/SESSF2012.html mailto:ndrey.tsiganov@gmail.com http://dx.doi.org/10.3842/SIGMA.2012.031 http://www.emis.de/journals/SIGMA/SESSF2012.html 2 A.V. Tsiganov 2 The Stäckel systems The system associated with the name of Stäckel [11] is a holonomic system on the phase space R2n, with the canonical variables q = (q1, . . . , qn) and p = (p1, . . . , pn): Ω = n∑ j=1 dpj ∧ dqj , {pj , qk} = δjk. The nondegenerate n × n Stäckel matrix S, whose j column depends only on coordinate qj , defines n functionally independent integrals of motion Hk = n∑ j=1 ( S−1 ) jk ( p2j + Vj(qj) ) , the separated relations p2j = n∑ k=1 HkSkj(qj)− Vj(qj), and the action variables wk ωi = 1 n n∑ j=1 ∫ qj Sij(λ)√ n∑ k=1 HkSkj(λ)− Vj(λ) dλ, (2.1) so that {Hj , Hk} = {ωi, ωk} = 0, {Hj , ωk} = δij . In generic case the action variables (2.1) are sums of the multi-valued Abelian integrals. However, if we are able to apply the known addition theorems for these Abelian integrals then we can get additional integrals of motion [12, 13, 14]. Let us discuss addition theorems for the logarithmic (exponential) and elliptic functions [1, 3]. In the first case polynomials Pj = n∑ k=1 HkSkj(λ)− Vj(λ) are the second-order polynomials and ω = 1 n m∑ j=1 ∫ qj dλ√ k2jλ 2 + bjλ+ cj = m∑ j=1 ln ( pj + k2j qj + bj kj ) 1 nkj . So, we can easily get polynomial or rational function Z = ezω = m∏ j=1 ( pj + k2j qj + bj kj ) z nkj (2.2) at the special choice of kj and z. In the second case m− 1 angle variables ωk, . . . , ωk+m−1 with 1 < m ≤ n have to satisfy to the Abel equations dx1√ f(x1) + dx2√ f(x2) + · · ·+ dxm√ f(xm) = dωk, Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates 3 x1dx1√ f(x1) + x2dx2√ f(x2) + · · ·+ xmdxm√ f(xm) = dωk+1, · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · xm−2 1 dx1√ f(x1) + xm−2 2 dx2√ f(x2) + · · ·+ xm−2 m dxm√ f(xm) = dωk+m−1, with a common polynomial of fixed degree 2m f(x) ≡ A2mx2m +A2m−1x 2m−1 + · · ·+A1x +A0. (2.3) If this case there are some additional Richelot integrals of motion [10] Ck = [√ f(x1) F ′(x1) · 1 ak − x1 + · · ·+ √ f(xm) F ′(xm) · 1 ak − xm ]2 [√ f(x1) F ′(x1) + · · ·+ √ f(xm) F ′(xm) ]2 −A2m F (ak). Here ak are values of x at the branch points of the corresponding hyperelliptic curve and F (x) = (x− x1)(x− x2) · · · (x− xm) [10]. At m = 2 we have famous Euler algebraic integral [3]. If A2m = 0 and A2m−1 6= 0 in (2.3) there is another additional Richelot integrals of motion [10]. The Weierstrass generating function of such integrals for any values of the coefficients Ak and other constructions of additional integrals of the Abel equations are discussed in [1]. Some example of the Euler and Richelot superintegrable systems may be found in [4, 12, 15]. Below we show how these addition theorems could help us to classify superintegrable systems. 3 Elliptic coordinate system Let us consider elliptic coordinates on the plane q1,2 defined by 1− x2 λ− κ − y2 λ+ κ = (λ− q1)(λ− q2) λ2 − κ2 , κ ∈ R. The corresponding momenta reads as p1 = 2pxx q1 − κ + 2pyy q1 + κ , p2 = 2pxx q2 − κ + 2pyy q2 + κ . The Stäckel matrix and the separated relations S =  q1 q21 − κ2 q2 q22 − κ2 1 q21 − κ2 1 q22 − κ2  , p21 + V1 − q1H1 q21 − κ2 − H2 q21 − κ2 = 0, p22 + V2 − q2H1 q22 − κ2 − H2 q22 − κ2 = 0, give rise to the following Hamiltonians in the involution H1 = (q21 − κ2)(p21 + V1) q2 − q1 + (q22 − κ2)(p22 + V2) q2 − q1 , H2 = q2(q 2 1 − κ2)(p21 + V1) q1 − q2 − q1(q 2 2 − κ2)(p22 + V2) q1 − q2 . 4 A.V. Tsiganov The Hamiltonian H1 commutes with the second angle variable w2, which is equal to w2 = 1 2 ∫ q1 dλ√ (λ2 − κ2)(λH1 +H2 − V1λ2 + V1κ2) + 1 2 ∫ q2 dλ√ (λ2 − κ2)(λH1 +H2 − V2λ2 + V2κ2) . (3.1) Polynomials P1,2 = ( λ2 − κ2 )( λH1 +H2 − V1,2λ2 + V1,2κ 2 ) (3.2) standing under square root in these integrals are at least third-order polynomials on λ. So, in this case we can not apply addition theorem for the logarithms. It is easy to see that we can apply addition theorem for the elliptic functions at V1 = V1 = α. Namely, if we put λ = x and λ = y in the first and second integrals (3.1), we could apply the Euler addition theorem dx√ X + dy√ Y = ds√ S (3.3) to angle variable ω2. Here X is an arbitrary quartic X = ax4 + 4bx3 + 6cx2 + 4dx + e (3.4) and Y, S are the same functions of another variables y and s. In this case, symmetrical bi- quadratic form of x and y F (x, y) = ax2y2 + 2bxy(x + y) + c ( x2 + 4xy + y2 ) + 2d(x + y) + e = 0 defines the conic section on the plane (x, y). According to [1, 3, 10], there is a famous Euler integral C = F (x, y)− √ X √ Y 2(x− y)2 = 1 4 (√ X− √ Y x− y )2 − a(x + y)2 4 − b(x + y)− c. (3.5) For the quartic (3.2) associated with the angle variable (3.1) this Euler integral looks like H3 = (p1 − p2)(q21 − κ2)(q22 − κ2) (q1 − q2)3 ( α(q1 − q2)2 − (p1 − p2)2κ2 + (p1q1 − p2q2)2 ) . Here q1,2 and p1,2 are elliptic coordinates and momenta. It is a third-order polynomial in momenta which commutes with the Hamiltonian {H1, H2} = 0, {H2, H3} = H4 6= 0. The algebra of the polynomial integrals of motion H1, H2, H3 can be closed only after some other polynomial generators are added. Thus, we easily find the additional integrals of motion for the Hamilton function of the oscillator 4H1 = p2x + p2y + a ( x2 + y2 ) using the separation of variables in elliptic coordinate system and the corresponding angle va- riables. Another result is that there is only one superintegrable system separable in elliptic coordinates and associated with the known addition theorems for Abelian integrals. Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates 5 4 Parabolic coordinate system Let us consider parabolic coordinates on the plane q1,2 defined by x = q1q2, y = q21 − q22 2 and the corresponding momenta px = p1q2 + p2q1 q21 + q22 , py = q1p1 − q2p2 q21 + q22 , The Stäckel matrix and the separated relations S = ( q21 q22 1 −1 ) , p21 + V1(q1)− q21H1 −H2 = 0, p22 + V2(q2)− q22H1 +H2 = 0, (4.1) give rise to the Hamiltonians H1 = p21 + p+2 V1(q1) + V2(q2) q21 + q22 , H2 = p21q 2 2 − p22q21 + q22V1(q1)− q21V2(q2) q21 + q22 . The Hamiltonian H1 commutes with the second angle variable w2, which is equal to w2 = 1 2 ∫ q1 dλ√ λ2H1 +H2 − V1(λ) + 1 2 ∫ q2 dλ√ λ2H1 −H2 − V2(λ) . In contrast with the elliptic coordinates, polynomials P1,2 = λ2H1 +H2 − V1,2(λ) standing under square root in these integrals are at least second-order polynomials on λ. So, we can apply both known addition theorems to these Abelian integrals. In fact, these integrals are expressed via logarithmic functions iff: Case 1 : V1 = b1q1 + c1, V2 = b2q2 + c2, Case 2 : V1 = a1q −2 1 + b1, V2 = a2q −2 2 + b1. The addition theorem for the elliptic function is applicable iff: Case 3 : V1 = a1q 6 1 + b1q 4 1 + c1q −2 1 , V2 = a1q 6 2 − b1q42 + c1q −2 2 . The corresponding Hamilton functions are deformations of the Kepler–Coulomb and oscillator Hamiltonians: Case 1 : H1 = p2x + p2y + 1 2 √ x2 + y2 ( b1 √ x+ √ x2 + y2 + b2 √√ x2 + y2 − x+ c1 + c2 ) = p2x + p2y + 1 2r ( b1 √ 2 cos ϕ 2 + b2 √ 2 sin ϕ 2 + c1 + c2 ) ; Case 2 : H1 = p2x + p2y + 1 2 √ x2 + y2 ( a1 x+ √ x2 + y2 + a2 x− √ x2 + y2 + b1 + b2 ) = p2x + p2y + a1 2r2 (cosϕ+ 1) − a2 2r2 (cosϕ− 1) + b1 + b2 2r ; Case 3 : H1 = p2x + p2y + α ( 4x2 + y2 ) + 2βx+ γ y2 . Here r = √ x2 + y2 and ϕ = arctanx/y are polar coordinates on the plane. According to [8] these systems remain superintegrable in the quantum case. 6 A.V. Tsiganov 4.1 Case 1 In the first case the second angle variable equals ω2 = 1 2 ∫ q1 dλ√ λ2H1 − b1λ+H2 − c1 − 1 2 ∫ q2 dλ√ λ2H1 − b2λ−H2 − c2 = ln ( p1 − q1H1−b1/2√ H1 ) 2 √ H1 − ln ( p2 − q2H1−b2/2√ H1 ) 2 √ H1 . The application of the addition theorem (2.2) to ω2 gives rise to the following rational integral of motion Z = e2 √ H1ω2 = 2q1H1 + 2p1 √ H1 − b1 2q2H1 + 2p2 √ H1 − b2 . In order to calculate polynomial integral of motion let us consider a series expansion of the function f = 1√ H1 ( αZ + βZ−1 ) = α(4H1H2 − 4H1c1 − b21)− β(4H1H2 + 4H1c2 + b22)√ H1(4H1c2 + 4H1H2 + b22)(b 2 1 + 4H1c1 − 4H1H2) +O(p1,2), by momenta p1,2. Here we substitute the variables q1,2 from the separated relations (4.1) into the rational integral Z and α, β are undefined polynomials in H1,2. Equating first coefficient of this expansion to zero one gets the following expressions for these polynomials α = 4H1H2 + 4H1c2 + b22, β = 4H1H2 − 4H1c1 − b21. At this values of α and β the function f becomes a third-order polynomial in momenta H3 = 1√ H1 ( αZ + βZ−1 ) = 1√ H1 ( αe2 √ H1ω2 + βe−2 √ H1ω2 ) = 8(p1q2 − p2q1)(p21 + p22 + c1 + c2) q21 + q22 + 4 ( 2p1q1q2 − p2(q21 − q22) ) b1 q21 + q22 − 4 ( 2p2q1q2 + p1(q 2 1 − q22) ) b2 q21 + q22 , such that {H1, H3} = 0. In order to close the algebra of the polynomial integrals of motion H1, H2, H3 we have to add one more polynomial generator H4 = {H2, H3} = 2αe2 √ H1ω2 − 2βe−2 √ H1ω2 . by analogy with exp(ω), sin(ω) and cos(ω) functions. Remark 1. One of the referees proposed another construction of the polynomial integrals of motion from the angle variable ω2. Namely, from the separation equations we can deduce that ∆1 = (2q1H1 + 2p1 √ H1 − b1)(2q1H1 − 2p1 √ H1 − b1) = −4H1H2 + 4H1c1 + b21, ∆2 = (2q2H1 + 2p2 √ H1 − b2)(2q2H1 − 2p2 √ H1 − b2) = 4H1H2 + 4H1c2 + b22. Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates 7 We can therefore write Ψ1 = ∆1Z −1 = ( (2q1H1 − b1)(2q2H2 − b2)− 4H1p1p2 ) − 2 √ H1 ( (2q2H1 − b2)p1 − (2q1H1 − b1)p2 ) and Ψ2 = ∆2Z = ( (2q1H1 − b1)(2q2H2 − b2)− 4H1p1p2 ) + 2 √ H1 ( (2q2H1 − b2)p1 − (2q1H1 − b1)p2 ) . Consequently H3 = 1√ H1 (Ψ1 −Ψ2) = −4 ( (2q2H1 − b2)p1 − (2q1H1 − b1)p2 ) is a third-order constant of motion. This method of explanation may be clearer than the method of expansion of the rational in momenta function f = αZ + βZ−1 with indefinite coefficients α and β. Remark 2. Let us remind, that two-dimensional open Toda lattice defined by the following polynomial integrals of motion H1 = p21 + p22 + eq1−q2 , H2 = p1 + p2, has the non-rational in momenta additional integral of motion Z = p1 − p2 + √ J p1 − p2 − √ J exp (√ J q1 + q2 p1 + p2 ) , J = 2H2 −H2 1 . which can be also obtained from the second angle variable ω2 [14]. However, it is easy to prove, that we can not apply working above constructions of polynomial integral of motion H3 in this case. 4.2 Case 2 In the second case the angle variable is equal to ω2 = 1 2 ∫ q1 λdλ√ λ4H1 + (H2 − b1)λ2 − a1 − 1 2 ∫ q2 λdλ√ λ4H1 − (H2 + b2)λ2 − a2 . Changing variables µ = λ2 one gets second-order polynomials Pj = µ2H1 ± (H2 ∓ bj)µ− aj under the square root and desired sum of the logarithms ω2 = ln ( 2q21H1 + 2q1p1 √ H1 +H2 − b1) ) 4 √ H1 − ln ( 2q22H1 + 2q2p2 √ H1 −H2 − b2) ) 4 √ H1 . The rational integral of motion (2.2) is equal to Z = e4 √ H1ω2 = 2q21H1 + 2q1p1 √ H1 +H2 − b1 2q22H1 + 2q2p2 √ H1 −H2 − b2 . 8 A.V. Tsiganov As above we consider the expansion of the function f = 1√ H1 ( αZ + βZ−1 ) by momenta p1,2. Equating first coefficient of this expansion to zero one gets polynomials α, β α = 4H1a2 + b22 + 2b2H2 +H2 2 , β = −4H1a1 − b21 + 2b1H2 −H2 2 . At this values of α and β the function f becomes a third-order polynomial in momenta H3 = 1√ H1 ( αZ + βZ−1 ) = 1√ H1 ( αe4 √ H1ω2 + βe−4 √ H1ω2 ) = 4(q1p1 − q2p2)(q2p1 − q1p2)2 q21 + q22 + 4q1q2(q2p1 − q1p2)(b1 + b2) q21 + q22 + 4a1q2 ( q2q1p1 − (2q21 + q22)p2 ) q21(q21 + q22) − 4a2q1 ( q2q1p2 − (2q22 + q21)p1 ) q22(q21 + q22) . such that {H1, H3} = 0. In order to close the algebra of the polynomial integrals of motion H1, H2, H3 we have to add one more polynomial generator H4 = {H2, H3} = 4αe4 √ H1ω2 − 4βe−4 √ H1ω2 . 4.3 Case 3 In the third case the angle variable is equal to ω2 = ∫ q1 λdλ√ −a1λ8 − b1λ6 +H1λ4 +H2λ2 − c1 − ∫ q2 λdλ√ −a1λ8 + b1λ6 +H1λ4 −H2λ2 − c1 . Changing variables λ = √ x and λ = i √ y at the first and second integral one gets the Euler addition theorem (3.3). In fact, this example has been considered in Euler’s book [3] too. Identifying quartic P = −a1µ4 − b1µ3 +H1µ 2 +H2µ− c1 with X (3.4) we can easily calculate the Euler integral of motion (3.5) in parabolic coordinates H3 = s = (q1p1 − q2p2)(q1p2 + q2p1) 2 (q21 + q22)3 + a1q1q2(2q 3 1p2 + q2q 2 1p1 − q1q22p2 − 2q32p1) q21 + q22 + b1q1q2(q1p2 + q2p1) q21 + q22 + c1(q1p1 − q2p2) q21q 2 2(q21 + q22) . The algebra of the integrals of motion H1, H2, H3 is more complicated then the algebra asso- ciated with the addition theorem for logarithms. In fact, in order to close this algebra we have to introduce the counterparts of the Jacobi elliptic functions sn(ω), cn(ω) and dn(ω) instead of the trigonometric functions sin(ω) and cos(ω), which we used for the superintegrable systems associated with the addition theorem for logarithms. Superintegrable Stäckel Systems on the Plane: Elliptic and Parabolic Coordinates 9 5 Conclusion It is known that orthogonal coordinate systems on Riemaniann manifolds can be viewed as an orthogonal sum of certain basic coordinate systems and these basic systems can be obtained from the elliptic coordinate system [5] using a degeneration procedure. This degeneration decreases the degree of polynomials standing under square roots into the angle variables (2.1). Thus, we have only one superintegrable systems separable in elliptic coordinates, whereas for degenerations we have a lot of different superintegrable systems. As usual, the addition theorem for logarithms allows us to get additional integrals of higher order in momenta [12, 13]. Acknowledgments We are greatly indebted referees for several improvements and corrections induced by their comments. 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Theor. 43 (2010), 055201, 14 pages, arXiv:0909.2923. http://dx.doi.org/10.1134/S156035470906001X http://dx.doi.org/10.1088/1751-8113/42/7/075202 http://dx.doi.org/10.1088/1751-8113/42/7/075202 http://arxiv.org/abs/1202.0197 http://dx.doi.org/10.1016/j.physd.2011.05.020 http://arxiv.org/abs/1011.3249 http://arxiv.org/abs/1204.0700 http://dx.doi.org/10.1088/1751-8113/44/16/162001 http://arxiv.org/abs/1101.5405 http://dx.doi.org/10.1515/crll.1842.23.354 http://dx.doi.org/10.1515/crll.1842.23.354 http://dx.doi.org/10.1088/1751-8113/41/33/335204 http://arxiv.org/abs/0805.3443 http://dx.doi.org/10.1134/S1560354709030034 http://arxiv.org/abs/0810.1100 http://dx.doi.org/10.1134/S1560354708030040 http://arxiv.org/abs/0711.2225 http://dx.doi.org/10.1088/1751-8113/43/5/055201 http://arxiv.org/abs/0909.2923 1 Introduction 2 The Stäckel systems 3 Elliptic coordinate system 4 Parabolic coordinate system 4.1 Case 1 4.2 Case 2 4.3 Case 3 5 Conclusion References