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Ivancevic_Applied-Diff-Geom

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<strong>Applied</strong> Manifold <strong>Geom</strong>etry 453results in the Jacobi Hamiltonian [Lanczos (1986)]. Another closely relatedgeometrization was used in [Rosquist (1997)]. Both methods involvea re–parameterization of the independent variable. Usually we will refer tothe independent variable as the time, although its physical interpretationmay vary. As a consequence of this feature, the original Lax representationis not preserved. It is known how to transform the invariants themselvesunder the time re–parameterization [Rosquist and Pucacco (1995);Rosquist (1997)]. Given that the geometrized invariants are also in involution,the existence of a Lax representation is guaranteed [Babelon andViallet (1990)]. However, to actually find such a Lax representation isnon–trivial. Another geometrization scheme which does preserve the originalLax representation is to apply a suitable canonical transformation. Thisis however only possible for Hamiltonians with a potential of a special form.One such system that we will consider in this paper is the 3–particle openToda latticeH = 1 2(¯p1 2 + ¯p 2 2 + ¯p 32 ) + e 2(¯q1 −¯q 2) + e 2(¯q2 −¯q 3) . (3.265)Below we will discuss two canonical transformations which correspond to inequivalentgeometric representations of (3.265). For an explicit integrationof the Toda lattice, see e.g. [Perelomov (1990)]. The standard symmetricLax representation is [Perelomov (1990)]⎛ ⎞ ⎛⎞¯p 1 ā 1 00 ā 1 0L = ⎝ ā 1 ¯p 2 ā 2⎠ , A = ⎝ −ā 1 0 ā 2⎠ ,0 ā 2 ¯p 3 0 −ā 2 0where ā 1 = exp(¯q 1 − ¯q 2 ), ā 2 = exp(¯q 2 − ¯q 3 ).Note that the definitions of ā 1 and ā 2 differ from the ones used in [Rosquist(1997)]. The Hamiltonian (3.265) admits the linear invariant, I 1 = L = ¯p 1 +¯p 2 + ¯p 3 , corresponding to translational invariance. The Lax representationalso gives rise to the two invariants, I 2 = 1 2 L2 = H and I 3 = 1 3 L3 . We willassume that the tensorial Lax representation is linear and homogeneous inthe momenta. A homogeneous Lax representation can be obtained fromthe standard representation by applying a canonical transformation of thephase space.3.16.2.1 Tensorial Lax RepresentationHere we straightforwardly apply a simple canonical transformation that willgive a linear and homogeneous Lax representation [Rosquist and Goliath

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