Showing papers on "Symplectic representation published in 1994"

Numerical Hamiltonian Problems

Abstract: Hamiltonian Systems. Examples of Hamiltonian Systems. Symplecticness. The solution operator. Preservation of area. Checking preservation of area: Jacobians. Checking preservation of area: differential forms. Symplectic transformations. Conservation of volume. Numerical Methods. Numerical integrators. Stiff problems. Runge-Kutta methods. Partitioned Runge-Kutta methods. Runge-Kutta-Nystrom methods. Composition of methods - adjoints. Order conditions. Order conditions for Runge-Kutta methods. The local error in Runge-Kutta methods. Order conditions for PRK methods. The local error in Partitioned Runge-Kutta methods. Order conditions for Runge-Kutta-Nystrom methods. The local error in Runge-Kutta-Nystrom mehthods. Implementation. Variable step sizes. Embedded pairs. Numerical experience with variable step sizes. Implementing implicit methods. Fourth-order Gauss method. Symplectic integration. Symplectic methods. Symplectic Runge-Kutta methods. Symplectic partitioned Runge-Kutta methods. Symplectic Runge-Kutta-Nystrom methods. Necessity of the symplecticness conditions. Symplectic order conditions. Prelimiaries. Order conditions for symplectic RK methods. Order conditions for symplectic PRK methods. Order conditions for symplectic RKN methods. Homogenous form of the order conditions. Available symplectic methods. Symplecticness of the Gauss methods. Diagonally implicity Runge-Kutta methods. Other symplectic Runge-Kutta methods. Explicit partitioned Runge-Kutta methods. Available symplectic Runge-Kutta-Nystrom methods. Numerical experiments. A comparison of symplectic integrators. Variable step sizes for symplectic methods. Conclusions and recommendations. Properties of symplectic integrators. Backward error interpretation. An alternative approach. Conservation of energy. KAM theory. Generating functions. The concept of generating function. Hamilton-Jacobi equations. Integrators based on generating functions. Generating functions for RK methods. Canonical order theory. Lie formalism. The Poisson bracket. Lie operators and Lie series. The Baker-Campbell-Hausdorff formula. Application to fractional-step methods. Extension to the non-Hamilton case. High-order methods. High-order Lie methods. High-order Runge-Kutta-Nystrom methods. A comparison of order 8 symplectic integrators. Extensions. Partitioned Runge-Kutta methods for nonseparable Hamiltonian systems. Canonical B-series. Conjugate symplectic methods. Trapezoidal rule. Constrained systems. General Poisson structures. Multistep methods. Partial differential equations. Reversable systems. Volume preserving flows.

Symplectic structures associated to Lie-Poisson groups

Abstract: The Lie-Poisson analogues of the cotangent bundle and coadjoint orbits of a Lie group are considered. For the natural Poisson brackets the symplectic leaves in these manifolds are classified, and the corresponding symplectic forms are described. Thus the construction of the Kirillov symplectic form is generalized for Lie-Poisson groups.

Conserving algorithms for the dynamics of Hamiltonian systems on lie groups

Abstract: Three conservation laws are associated with the dynamics of Hamiltonian systems with symmetry: The total energy, the momentum map associated with the symmetry group, and the symplectic structure are invariant under the flow. Discrete time approximations of Hamiltonian flows typically do not share these properties unless specifically designed to do so. We develop explicit conservation conditions for a general class of algorithms on Lie groups. For the rigid body these conditions lead to a single-step algorithm that exactly preserves the energy, spatial momentum, and symplectic form. For homogeneous nonlinear elasticity, we find algorithms that conserve angular momentum and either the energy or the symplectic form.

An introduction to symplectic geometry

Abstract: A symplectic form on a vector space V is a skew-symmetric bilinear form α: V × V → R such that \( \tilde \alpha :V \to V^ \star \tilde \alpha (x)(y) = \alpha (x,y) \) is an isomorphism. Here V* denotes the dual of V.

The Differential Geometry of Fedosov’s Quantization

Abstract: B. Fedosov has given a simple and very natural construction of a deformation quantization for any symplectic manifold, using a flat connection on the bundle of formal Weyl algebras associated to the tangent bundle of a symplectic manifold. The connection is obtained by affinizing, nonlinearizing, and iteratively flattening a given torsion free symplectic connection. In this paper, a classical analog of Fedosov’s operations on connections is analyzed and shown to produce the usual exponential mapping of a linear connection on an ordinary manifold. A symplectic version is also analyzed. Finally, some remarks are made on the implications for deformation quantization of Fedosov’s index theorem on general symplectic manifolds.

Symplectic reduction of higher order Lagrangian systems with symmetry

Abstract: One can develop a symplectic reduction procedure for higher order Lagrangian systems with symmetry. The reconstruction procedure of the dynamics is also studied and an application (spinning particle) is given at the end of the work.

Symplectic manifolds, coherent states, and semiclassical approximation

Abstract: The symplectic structure and Hamiltonian dynamics for a class of Grassmannian manifolds are described here. Using the two‐dimensional sphere (S2) and disc (D2) as illustrative cases, we write their path integral representations using coherent state techniques. These path integrals can be evaluated exactly by semiclassical methods, thus providing examples of the localization formula. Along the way, we also give a local coordinate description for a class of Grassmannians.

An explicit description of the symplectic structure of moduli spaces of flat connections

Abstract: The moduli space of flat connections on a principal G‐bundle over a compact oriented surface of genus g≥1 is considered herein. Using the holonomies around noncontractible loops, the moduli space is described as a quotient of a submanifold of G2g. An explicit expression is obtained for the symplectic form on the smooth part of moduli space, and several properties of this form are established.

Symplectic and almost complex manifolds

Abstract: The aim of this chapter is to introduce the basic problems and (soft!) techniques in symplectic geometry by presenting examples—more exactly series of examples— of almost complex and symplectic manifolds: it is obviously easier to understand the classification of symplectic ruled surfaces if you have already heard of Hirzebruch surfaces for instance.

Massless particles, electromagnetism, and Rieffel induction

Abstract: The connection between space-time covariant representations (obtained by inducing from the Lorentz group) and irreducible unitary representations (induced from Wigner's little group) of the Poincar\'{e} group is re-examined in the massless case. In the situation relevant to physics, it is found that these are related by Marsden-Weinstein reduction with respect to a gauge group. An analogous phenomenon is observed for classical massless relativistic particles. This symplectic reduction procedure can be (`second') quantized using a generalization of the Rieffel induction technique in operator algebra theory, which is carried through in detail for electro- magnetism. Starting from the so-called Fermi representation of the field algebra generated by the free abelian gauge field, we construct a new (`rigged') sesquilinear form on the representation space, which is positive semi-definite, and given in terms of a Gaussian weak distribution (promeasure) on the gauge group (taken to be a Hilbert Lie group). This eventually constructs the algebra of observables of quantum electro- magnetism (directly in its vacuum representation) as a representation of the so-called algebra of weak observables induced by the trivial representation of the gauge group.

Symplectic analysis of a Dirac constrained theory

Abstract: The symplectic formalism is applied to a system recently analyzed by the Dirac method. It is shown that this procedure is quite straightforward and elegant for the two versions of the model.

Symplectic toric orbifolds

Abstract: A symplectic toric orbifold is a compact connected orbifold $M$, a symplectic form $\omega$ on $M$, and an effective Hamiltonian action of a torus $T$ on $M$, where the dimension of $T$ is half the dimension of $M$. We prove that there is a one-to-one correspondence between symplectic toric orbifolds and convex rational simple polytopes with positive integers attached to each facet.

Classical intertwiner space and quantization

Abstract: Given two symplectic realizations, a symplectic manifold called the classical intertwiner space is introduced as a classical analogue of an intertwiner space of representations of an associative algebra. We describe explicitly how a quantum data on realizations induces a quantum data on their classical intertwiner space.

THE INFINITE-DIMENSIONAL p-ADIC SYMPLECTIC GROUP

Abstract: An analogue of the Fock representation is constructed for the infinite-dimensional p-adic Heisenberg group.The restricted symplectic group is defined for an infinite-dimensional symplectic space over the field Qp of p-adic numbers. For the restricted symplectic group a projective representation is constructed that is compatible with the representation of the Heisenberg group, and an expression for the cocycle of this representation is given in terms of the p-adic Maslov index. It is proved that the extension corresponding to this cocycle reduces to a Z2-extension.

Globally irreducible representations of the finite symplectic group Sp4(q)

Abstract: (1994). Globally irreducible representations of the finite symplectic group Sp4(q) Communications in Algebra: Vol. 22, No. 15, pp. 6439-6457.