Serge Andrianov Theory of Symplectic Formalism for Spin-Orbit Tracking

1. Saint-Petersburg State University, Russia Serge Andrianov Theory of SymplecticFormalism for Spin-Orbit Tracking Institute for Nuclear Physics ForschungszentrumJuelich September 25, 2013 1/12

2. Theoretical preparation of motion equations Equation of particles and spin evolution: Particles and Spin Motion Equations Lorentz-Maxwell equations L-M+T-BMTequations + T-BMTequations B and E-fields expansion in the neighborhood of the equilibrium trajectory Transformation of the L-M+T-BMT equations into the auxiliary coordinate system Transport matrix presentation of solution Tensor presentation of solution 2/12

3. The matrix form of nonlinear ODE’s All equations of particles and spin evolution can be written the following short form: We use Taylor series expansion in this form Here the Kronecker product. For k=2 we have k-times The solution is constructed in the form 3/12

4. The matrix presentation of ODE’s solutions (continue) Matrices describe the beam evaluation, which have evaluate using some different schemes. The choice of the scheme defines the convergence velocity corresponding series. Here there some different possibilities! The form of “usual” tensor presentation of the corresponding series can be written in the more complicated form see, for example, E´tienne Forest Geometric integration for particle accelerators. J. Phys. A: Math. Gen. 39 (2006) 5321–5377 4/12

5. From a physical model to a mathematical models It is well known that the computational problems in beam physics can be divided into the following groups. The First group of the problem is related to determining the required degree of approximation corresponding to the problem under study (on what power degree we should truncateourseries (the accuracy of all our manipulations). The Second group is based on calculation of the corresponding evolution operators in the framework of an used formalisms (here can be used different kind of methods – for example, COSY Infinity). The Third group of problems is connected with some specific problems, for example - long beam evolution problem, spin dynamics, the influence space charge, different aberrations correction and so on. It is necessary also to mention problems embedding the selected numerical methods into some computational framework to carry out the necessary computational experiments, carry out optimization process and so on. 5/12

6. From a physical model to a mathematical models Let list the basic requirements for the methods that can be used to model the beam dynamics and the corresponding related problems. First, the accuracy of approximation of the “ideal mapping” generated by the dynamical system under study. Here we should mention the problem: how estimate the closeness of ideal solutions and the corresponding approximate solutions? The second important demand is connected with the need to preserve the qualitative properties inherent in the dynamical system under study. For example, such as the symplectic property for Hamiltonian systems, conservation of exact (for example, energy conservation) and approximate integralsof motion and so on. Finally, accurate construction of the maps for some practical classes of dynamical systems. All our series will converge absolutely! In particular, it is necessary to mention one more problem - the problem of parallel and distributed computing processes using the corresponding maps both for the dynamics of particles and for an ensemble of particles in whole. The suggestedmethod admits distributing and paralleling by a naturally way. 6/12

7. Some examples of exact solutions The correctness of the matrix formalism can be tested for some simple examples. 1.One-dimensional nonlinear equation The exact solution of this equality has the form For Lie operator for our differential equation can be written in the form ! After some simple calculations one can obtain the desired solution! 7/12

8. Some examples of exact solutions As an example we consider the second order nonlinear Hamiltonian equations Using the above described approach one can obtain (4) (5) where We should note that (5) is exact solution of the equation system (4)! 8/12

9. The preservation of qualitative properties in matrix formalism (symplecticity) The symplecticity property of our computational scheme constrains some special restrictions, which can be written in the linear algebraic equations for some elements of corresponding matrices. For example, for the second order we obtain The symplecticity condition Remark1. Similar formulae we can receive from linear algebraic equations and for any order of nonlinearities! Remark2. For two dimensional phase vector and the second order of nonlinearity have the full agreement with the result, published in the paper by E´tienne Forest “Geometric integration for particle accelerators”. J. Phys. A: Math. Gen. 39 (2006) on the page 5335: It should be noted that similar matrices can be precomputed (for example, using Maple or Mathematica packages) and kept that in a special database. This approach guaranties us fulfillment of the symplecticity conditions up the necessary order (for arbitrary interval of independent variable)! 9/12

10. The preservation of qualitative properties in matrix formalism (energy conservation) It is known that in general cases the symplecticity of the map (exact or approximate map) does not guarantee the energy conservation. That is why we should imposed additionally condition for our approximating maps. In another words on the every step of the integration process we should guarantee the fulfillment of energy conservation law, which can be written in the following forms. In another words on the every step we must guarantee the energy conservation low, which can be written in the following forms , These conditions can be realized using some correction procedure. For linear case we have where , and we have ! 10/12

11. The preservation of qualitative properties in matrix formalism (energy conservation for nonlinear systems) There is a problem: Can we construct an integration scheme that is both symplectic and energy-conserving properties for a broad class of Hamiltonian systems? The well known Zhang and Marsden theorem answer – in general case – NO! If we want to conserve nonlinear Hamiltonian, than we should “correct a little” our truncated matrix map. In another words, some elements of we should be corrected. For this purpose we can evaluate some equations (see, an example, the correction procedure for symplectification). Here there are some different approaches. The choice of appropriate variant depends on the practical problem: the symplectification condition is universal property, while the energy conservation depends on the energy function (Hamiltonian)! Here there are some approaches. For our problems (particles beam + spin dynamics) the most appropriate method is the method of stroboscopic averaging, using the ergodic properties of our dynamical system. 11/29

12. The convergence problem for the matrix formalism (in terms of the phase vector ) We can derive corresponding conditions for convergence of matrix formalism using ODE’s presentation. Let cite corresponding estimations. Let be , from where and we have and , We can show that there are the next inequalities and Let be then we have (here is an exact solution): This inequality allows us to provide necessary estimation of our calculation accuracy! 12/29

13. Saint-Petersburg State University, Russia Thank for you attention! September 25, 2013 Institute for Nuclear Physics ForschungszentrumJuelich 13/12