Symplectic methods applied to the Lotka-Volterra system
We analyse the preservation of physical properties of numerical approximations tosolutions of the Lotka-Volterra system: its positivity and the conservation of theHamiltonian. We focus on two numerical methods : the symplectic Euler method andan explicit variant of it. We first state under which con...
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ndltd-LACETR-oai-collectionscanada.gc.ca-QMM.195832014-02-13T03:56:53ZSymplectic methods applied to the Lotka-Volterra systemBeck, MélaniePure Sciences - MathematicsWe analyse the preservation of physical properties of numerical approximations tosolutions of the Lotka-Volterra system: its positivity and the conservation of theHamiltonian. We focus on two numerical methods : the symplectic Euler method andan explicit variant of it. We first state under which conditions they are symplectic andwe prove they are both Poisson integrators for the Lotka-Volterra system. Then, westudy under which conditions they stay positive. For the symplectic Euler method,we derive a simple condition under which the numerical approximation always stayspositive. For the explicit variant, there is no such simple condition. Using propertiesof Poisson integrators and backward error analysis, we prove that for initial conditionsin a given set in the positive quadrant, there exists a bound on the step size, such thatnumerical approximations with step sizes smaller than the bound stay positive overexponentially long time intervals. We also show how this bound can be estimated.We illustrate all our results by numerical experiments.McGill University2003Electronic Thesis or Dissertationapplication/pdfenalephsysno: 002022446Theses scanned by McGill Library.All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated.Master of Science (Department of Mathematics and Statistics) http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19583 |
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Pure Sciences - Mathematics Beck, Mélanie Symplectic methods applied to the Lotka-Volterra system |
description |
We analyse the preservation of physical properties of numerical approximations tosolutions of the Lotka-Volterra system: its positivity and the conservation of theHamiltonian. We focus on two numerical methods : the symplectic Euler method andan explicit variant of it. We first state under which conditions they are symplectic andwe prove they are both Poisson integrators for the Lotka-Volterra system. Then, westudy under which conditions they stay positive. For the symplectic Euler method,we derive a simple condition under which the numerical approximation always stayspositive. For the explicit variant, there is no such simple condition. Using propertiesof Poisson integrators and backward error analysis, we prove that for initial conditionsin a given set in the positive quadrant, there exists a bound on the step size, such thatnumerical approximations with step sizes smaller than the bound stay positive overexponentially long time intervals. We also show how this bound can be estimated.We illustrate all our results by numerical experiments. |
author |
Beck, Mélanie |
author_facet |
Beck, Mélanie |
author_sort |
Beck, Mélanie |
title |
Symplectic methods applied to the Lotka-Volterra system |
title_short |
Symplectic methods applied to the Lotka-Volterra system |
title_full |
Symplectic methods applied to the Lotka-Volterra system |
title_fullStr |
Symplectic methods applied to the Lotka-Volterra system |
title_full_unstemmed |
Symplectic methods applied to the Lotka-Volterra system |
title_sort |
symplectic methods applied to the lotka-volterra system |
publisher |
McGill University |
publishDate |
2003 |
url |
http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19583 |
work_keys_str_mv |
AT beckmelanie symplecticmethodsappliedtothelotkavolterrasystem |
_version_ |
1716641951495749632 |