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Symmetries, computers, and periodic orbits for the n -body problem D.L. Ferrario (University of Milano-Bicocca, Italy) Geometry and Computer Science February 810, 2017 Pescara (IT) Abstract Periodic orbits play a central role in the n-body


  1. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  2. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  3. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  4. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  5. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  6. 3. A problem the journal, Edvard Phragmén. author were not what he is, I would not for a moment hesitate to say that he has made a great mistake here.” journal to be destroyed, to submit a new corrected memoir (he did it in June 1890 — 270 pages long) and to pay for the new printing (the cost was more than the 2500 crowns of the prize). It may happen that small difgerences in the initial conditions produce great ones in the fjnal phenomena. ➔ But there was a problem. ➔ Some parts of the manuscript were not clear to the editor of ➔ In December 1888 he wrote, about the manuscript, “If the ➔ He was actually right. There was a mistake. ➔ Poincaré had to get back all the printed issues of the ➔ This is a self-applied butterfmy efgect, as he put it:

  7. 4. Consequences equations and the three-body problem, between 1892 and 1901 he published the six memoirs on Analysis situs , where basically topology and algebraic topology were created. statement: the (now Perelman’s Theorem) uniqueness of the topology of 3-spheres among simply-connected closed 3-manifolds, and the density of periodic orbits in the phase space for the (restricted) 3-body problem. If a particular solution of the restricted problem is given, one can always fjnd a periodic solution (with a period which might be very long) such that the difgerence between these two solutions is as small as desired for any given length of time. ➔ Méthodes nouvelles de la mécanique céleste (1892–1899). ➔ Motivated by the study of nonlinear ordinary difgerential ➔ Two Poincaré conjectures, both based on a fjrst wrong

  8. 4. Consequences equations and the three-body problem, between 1892 and 1901 he published the six memoirs on Analysis situs , where basically topology and algebraic topology were created. statement: the (now Perelman’s Theorem) uniqueness of the topology of 3-spheres among simply-connected closed 3-manifolds, and the density of periodic orbits in the phase space for the (restricted) 3-body problem. If a particular solution of the restricted problem is given, one can always fjnd a periodic solution (with a period which might be very long) such that the difgerence between these two solutions is as small as desired for any given length of time. ➔ Méthodes nouvelles de la mécanique céleste (1892–1899). ➔ Motivated by the study of nonlinear ordinary difgerential ➔ Two Poincaré conjectures, both based on a fjrst wrong

  9. 4. Consequences equations and the three-body problem, between 1892 and 1901 he published the six memoirs on Analysis situs , where basically topology and algebraic topology were created. statement: the (now Perelman’s Theorem) uniqueness of the topology of 3-spheres among simply-connected closed 3-manifolds, and the density of periodic orbits in the phase space for the (restricted) 3-body problem. If a particular solution of the restricted problem is given, one can always fjnd a periodic solution (with a period which might be very long) such that the difgerence between these two solutions is as small as desired for any given length of time. ➔ Méthodes nouvelles de la mécanique céleste (1892–1899). ➔ Motivated by the study of nonlinear ordinary difgerential ➔ Two Poincaré conjectures, both based on a fjrst wrong

  10. 4. Consequences equations and the three-body problem, between 1892 and 1901 he published the six memoirs on Analysis situs , where basically topology and algebraic topology were created. statement: the (now Perelman’s Theorem) uniqueness of the topology of 3-spheres among simply-connected closed 3-manifolds, and the density of periodic orbits in the phase space for the (restricted) 3-body problem. If a particular solution of the restricted problem is given, one can always fjnd a periodic solution (with a period which might be very long) such that the difgerence between these two solutions is as small as desired for any given length of time. ➔ Méthodes nouvelles de la mécanique céleste (1892–1899). ➔ Motivated by the study of nonlinear ordinary difgerential ➔ Two Poincaré conjectures, both based on a fjrst wrong

  11. 5. King Oscar’s prize Lejeune Dirichlet communicated shortly before his death to a geometer cillations would appear to have served as his point of departure for this we know nothing about this method, except that the theory of small os- our planetary system in an absolutely rigorous manner. Unfortunately, plying this method, he had succeeded in demonstrating the stability of for integrating the difgerential equations of Mechanics, and that by ap- of his acquaintance [Leopold Kronecker] that he had discovered a method methods now at our disposal; we can at least suppose as much, since Given a system of arbitrarily many mass points that attract each other standing of the solar system, seems capable of solution using analytic This problem, whose solution would considerably extend our under- of whose values the series converges uniformly. as a series in a variable that is some known function of time and for all ever collide, try to fjnd a representation of the coordinates of each point according to Newton’s laws, under the assumption that no two points discovery. We can nevertheless suppose, almost with certainty, that

  12. 5. King Oscar’s prize (cont.) this method was based not on long and complicated calculations, but on the development of a fundamental and simple idea that one could rea- sonably hope to recover through persevering and penetrating research. In the event that this problem remains unsolved at the close of the con- test, the prize may also be awarded for a work in which some other prob- lem of Mechanics is treated as indicated and solved completely.

  13. 6. Long story heliocentric planetary model was formulated by Nicolaus Copernicus (1473–1543) in a note in 1513, and fjnally published with mathematical details in De revolutionibus orbium coelestium (1543). collected by Tycho Brahe (1546–1601), Kepler (1571–1630) discovered the laws governing the motion of planets around the sun, now called Kepler’s three laws of planetary motion. improved astronomical observations with telescope, and published the Dialogo sopra i massimi sistemi . ➔ Long after Aristarchus of Samos (3̃10–2̃30 BCE), the ➔ Founding his speculations on years of astronomical data ➔ After a few years, in 1632 Galileo Galilei (1564–1642)

  14. 6. Long story (cont.) problem can simply be stated, in modern words, as a m i m j gravitational potential force function d 2 q second-order difgerential Newton equation: in 1687. Philosophiæ Naturalis Principia Mathematica was published namely the law of universal gravitation. Newton’s born. He is the one who found the reason of Kepler’s laws, ➔ One year after Galileo died, Isaac Newton (1642–1727) was ➔ With Laws of Dynamics and Universal Gravitation, the dt 2 = ∇ U ( q ) , where q ( t ) is the confjguration at time t ∈ R , and U is the U ( q ) = ∑ | q i − q j | , i < j

  15. 6. Long story (cont.) Principia (propositions 1-17, 57-60). The conical nature of Kepler orbits can also be derived by purely geometrical means To predict the position positions of planets one has to use an approximation of solutions of Kepler equation and its generalizations. Then, in propositions 65-66, Newton describes some qualitative features of the three-body problem, and speculated that and exact solution “exceeds, if I am not mistaken, the force of any human mind”. where m i are the masses (in a unit such that the gravitational constant is 1) adn q i are the positions of the point masses in the euclidean space R d ( d = 2 , 3). ➔ Newton solved the two-body problem in the fjrst book of

  16. 6. (Long story) After Newton, Johann Bernoulli (1667–1748) and Leonhard Eu- ler (1707–1783) studied Newton’s equation for some simplifjed problems: they could integrate the the one-center and two fjxed- centers problem, which can be seen as an intermediate (inte- grable) approximation of the restricted three-body problem. In 1762, Euler considered the circular restricted three-body problem , which is related to the two-centers problem: consider Earth as rotation on a circle around the Sun, and consider the Moon as a negligible-mass body orbiting around the Earth, in rotating co- ordinates frame, and studied the collinear problem for generic masses (and found Euler central solutions).

  17. 6. (Long story) t 0 (1772); also, he introduced the concepts of stability (1776) and po- Lagrange confjgurations) in his Essai sur le problème des trois corps tions for the (non-restricted) three-body problem, now termed some particular periodic orbits (homographic central confjgura- q j j Joseph-Louis Lagrange (born Giuseppe Lodovico Lagrangia, 1736– 1 of the Lagrangean action functional lutions Newton equations are local minimizers (critical points) quence editions the Mécanique analytique (1811,1815). In short, so- chanics, now called Lagrangean mechanics, published in subse- much more impact, later founded the analytical approach to me- 1813) expanded and generalized the results of Euler, and, with tential (1773). ∫ t 1 dt | 2 + U ( q ) 2 ∑ A [ q ] = m j | defjned on a suitable class of trajectories q ( t ) . Lagrange found

  18. 7. Before Poincaré reductions of the degrees of freedom. Hamilton-Jacobi formalism (with Poisson and Lagrange brackets and canonical transformations). three-body problem was published in 1836. 1867. The main procedure was to expand the Hamiltonian as Fourier series with respect to position coordinates and apply suitable canonical transformations. could accurately predict the orbit of the Moon up to 1 arc second. ➔ Changes of variables, and search for integrals and ➔ Jacobi (1804–1851) and Hamilton (1805–1865) : ➔ The Jacobi integral for the three-dimensional restricted ➔ Delaunay (1816–1872) treatise on lunar theory, in 1860 and ➔ After 57 iterations and 20 years of calculations, Delaunay

  19. 7. Before Poincaré (cont.) Newcomb proved that the three-body problem can be formally solved by infjnite series of purely periodic terms; in Lagrange coordinates. so slowly to be practically useless. ➔ The approach via series seemed promising: in 1874 Simon ➔ in 1883, Lindstedt again showed that such a series existed, ➜ The fjrst problem is: a formal series might not converge. ➜ The second problem is: a convergent series might converge

  20. the solution? Weierstrass mentioned “a method for 7. (Before Poincaré) integrating the difgerential equations of Mechanics”. Why integration and not computing? Aren’t they the same thing? ➔ But, actually, what is exactly the problem? ➔ And, given the problem, what does it mean to solve it? ➔ Newton equations in which space? Sobolev space H 1 ? C 1 ? C ∞ . C ω ? ➔ And, when an equation is “solved”? Contructively giving ➔ Singularies and collisions.

  21. the solution? Weierstrass mentioned “a method for 7. (Before Poincaré) integrating the difgerential equations of Mechanics”. Why integration and not computing? Aren’t they the same thing? ➔ But, actually, what is exactly the problem? ➔ And, given the problem, what does it mean to solve it? ➔ Newton equations in which space? Sobolev space H 1 ? C 1 ? C ∞ . C ω ? ➔ And, when an equation is “solved”? Contructively giving ➔ Singularies and collisions.

  22. the solution? Weierstrass mentioned “a method for 7. (Before Poincaré) integrating the difgerential equations of Mechanics”. Why integration and not computing? Aren’t they the same thing? ➔ But, actually, what is exactly the problem? ➔ And, given the problem, what does it mean to solve it? ➔ Newton equations in which space? Sobolev space H 1 ? C 1 ? C ∞ . C ω ? ➔ And, when an equation is “solved”? Contructively giving ➔ Singularies and collisions.

  23. the solution? Weierstrass mentioned “a method for 7. (Before Poincaré) integrating the difgerential equations of Mechanics”. Why integration and not computing? Aren’t they the same thing? ➔ But, actually, what is exactly the problem? ➔ And, given the problem, what does it mean to solve it? ➔ Newton equations in which space? Sobolev space H 1 ? C 1 ? C ∞ . C ω ? ➔ And, when an equation is “solved”? Contructively giving ➔ Singularies and collisions.

  24. the solution? Weierstrass mentioned “a method for 7. (Before Poincaré) integrating the difgerential equations of Mechanics”. Why integration and not computing? Aren’t they the same thing? ➔ But, actually, what is exactly the problem? ➔ And, given the problem, what does it mean to solve it? ➔ Newton equations in which space? Sobolev space H 1 ? C 1 ? C ∞ . C ω ? ➔ And, when an equation is “solved”? Contructively giving ➔ Singularies and collisions.

  25. 8. Integrable systems (1884), and in 1887 he proved that there are no fjrst bodies). functions in the phase space (positions and velocities of the angular momentum and the energy/Hamiltonian) symmetries: the six of the centre of gravity, the three of integrals as algebraic (beyond those coming from known Lagrange can be divergent for the three-body problem systems, did not work well. which is the starting point of the theory of integrable solutions in terms of arbitrary constants. This approach, is to fjnd as many fjrst integrals as necessary to express the attack had been the one of “integrating” the equations, that integral for the restricted three-body problem, and in ... ➔ As with the integrability of Kepler problem, the fjrst line of ➔ Bruns (1848-1919) showed that the series solutions of ➔ In 1889 Poincaré proved that the Jacobi integral is the only

  26. 8. Integrable systems (1884), and in 1887 he proved that there are no fjrst bodies). functions in the phase space (positions and velocities of the angular momentum and the energy/Hamiltonian) symmetries: the six of the centre of gravity, the three of integrals as algebraic (beyond those coming from known Lagrange can be divergent for the three-body problem systems, did not work well. which is the starting point of the theory of integrable solutions in terms of arbitrary constants. This approach, is to fjnd as many fjrst integrals as necessary to express the attack had been the one of “integrating” the equations, that integral for the restricted three-body problem, and in ... ➔ As with the integrability of Kepler problem, the fjrst line of ➔ Bruns (1848-1919) showed that the series solutions of ➔ In 1889 Poincaré proved that the Jacobi integral is the only

  27. 8. Integrable systems (1884), and in 1887 he proved that there are no fjrst bodies). functions in the phase space (positions and velocities of the angular momentum and the energy/Hamiltonian) symmetries: the six of the centre of gravity, the three of integrals as algebraic (beyond those coming from known Lagrange can be divergent for the three-body problem systems, did not work well. which is the starting point of the theory of integrable solutions in terms of arbitrary constants. This approach, is to fjnd as many fjrst integrals as necessary to express the attack had been the one of “integrating” the equations, that integral for the restricted three-body problem, and in ... ➔ As with the integrability of Kepler problem, the fjrst line of ➔ Bruns (1848-1919) showed that the series solutions of ➔ In 1889 Poincaré proved that the Jacobi integral is the only

  28. 8. (Integrable systems) the non-existence of new integrals analytic in positions and the small parameter of mass-ratios of planets. unknown fjrst integrals which are algebric only in momenta. non-existence theorems and approximating Hamiltonians, until to-day. ➔ ... 1890 King’s Prize memoir in Acta Mathematica he proved ➔ Later, in 1896-98 Painlevé showed that there are no ➔ Still, the search of new integrals continues, with some

  29. 8. (Integrable systems) the non-existence of new integrals analytic in positions and the small parameter of mass-ratios of planets. unknown fjrst integrals which are algebric only in momenta. non-existence theorems and approximating Hamiltonians, until to-day. ➔ ... 1890 King’s Prize memoir in Acta Mathematica he proved ➔ Later, in 1896-98 Painlevé showed that there are no ➔ Still, the search of new integrals continues, with some

  30. 8. (Integrable systems) the non-existence of new integrals analytic in positions and the small parameter of mass-ratios of planets. unknown fjrst integrals which are algebric only in momenta. non-existence theorems and approximating Hamiltonians, until to-day. ➔ ... 1890 King’s Prize memoir in Acta Mathematica he proved ➔ Later, in 1896-98 Painlevé showed that there are no ➔ Still, the search of new integrals continues, with some

  31. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  32. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  33. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  34. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  35. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  36. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  37. 9. After Poincaré The ideas developed in Poincaré’s Les Méthodes nouvelles de la mé- canique celeste (1892-1899) contained seeds of innovation in many fjelds: Hadamard, E.T. Whittaker, G.D. Birkhofg, J. Moser) of periodic orbits as closed geodesics, restricted circular three-body problem, the Last Geometric Theorem of Poincaré proved). ➔ global approach to dynamical system ➔ qualitative ➔ Poincaré-Birkhofg recurrence theorem, ➔ or the analogy introduced by Poincaré (see also Jacques ➔ the topological approach to stability ➔ and periodic orbits as fjxed points of Poincaré section ➔ (and the existence of infjnitely many periodic orbits in the

  38. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  39. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  40. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  41. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  42. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  43. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  44. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  45. With a shift in computing techniques and the need of mathematical tools 10. Last century for space missions and astrodynamics, the problem is still very alive also from the mathematical point of view. ➔ Levi-Civita ➔ Moulton ➔ G.D. Birkhofg ➔ Chazy ➔ Sundmann ➔ Kolmogorov ➔ Arnold ➔ Moser ( = ⇒ KAM)

  46. 11. Series solutions? 1991: A generalization of and Abel-Ruffjni theorem). equations (Galois theory Compare with: was found by Quidong Wang. Sundman’s result to n -body collisions. Figure: Sundman Contraption: the collisions, but not for triple Regularization of binary full three-body problem. 1913: Karl Sundman. Solutions (never built) perturbograph by series in terms of t 1 / 3 for the ➔ Solve polynomial ➔ Compute digits of π .

  47. 11. Series solutions? 1991: A generalization of and Abel-Ruffjni theorem). equations (Galois theory Compare with: was found by Quidong Wang. Sundman’s result to n -body collisions. Figure: Sundman Contraption: the collisions, but not for triple Regularization of binary full three-body problem. 1913: Karl Sundman. Solutions (never built) perturbograph by series in terms of t 1 / 3 for the ➔ Solve polynomial ➔ Compute digits of π .

  48. 11. Series solutions? 1991: A generalization of and Abel-Ruffjni theorem). equations (Galois theory Compare with: was found by Quidong Wang. Sundman’s result to n -body collisions. Figure: Sundman Contraption: the collisions, but not for triple Regularization of binary full three-body problem. 1913: Karl Sundman. Solutions (never built) perturbograph by series in terms of t 1 / 3 for the ➔ Solve polynomial ➔ Compute digits of π .

  49. 11. Series solutions? 1991: A generalization of and Abel-Ruffjni theorem). equations (Galois theory Compare with: was found by Quidong Wang. Sundman’s result to n -body collisions. Figure: Sundman Contraption: the collisions, but not for triple Regularization of binary full three-body problem. 1913: Karl Sundman. Solutions (never built) perturbograph by series in terms of t 1 / 3 for the ➔ Solve polynomial ➔ Compute digits of π .

  50. 11. Series solutions? 1991: A generalization of and Abel-Ruffjni theorem). equations (Galois theory Compare with: was found by Quidong Wang. Sundman’s result to n -body collisions. Figure: Sundman Contraption: the collisions, but not for triple Regularization of binary full three-body problem. 1913: Karl Sundman. Solutions (never built) perturbograph by series in terms of t 1 / 3 for the ➔ Solve polynomial ➔ Compute digits of π .

  51. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  52. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  53. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  54. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  55. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  56. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  57. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  58. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  59. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  60. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  61. 12. The n -body problem is about: (1) Integrability and non-integrability and near-integrability (2) Series solutions (3) Stability (4) Chaotic dynamics / complexity (5) Computability (6) Intuitionism (7) Computer assisted/aided proofs (8) Approximations / verifjed approximations / certifjed calculations (9) Variational methods (10) Singularities and regularization (11) Periodic orbits

  62. 1 Poincaré, topology and the n -body problem 2 Periodic orbits, symmetries, geometry and Lagrangean mini- mizers 3 Qualitative features, analysis, modeling and computing 4 Explorations and crawlers: symmetry groups, loop spaces, critical points and interactive distributed computing 5 Human interaction: visualization, CLI and interfaces, 3D ma- nipulation and remote computations 6 Conclusions

  63. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  64. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  65. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  66. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  67. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  68. 14. What? area-preserving, orientation-preserving homeomorphism of an annulus that rotates the two boundaries in opposite PCR3BP periodic orbits are infjnite. Lagrange orbits. singularities. ➔ Last geometric theorem (Poincaré-Birkhofg Theorem: every directions has at least two fjxed points) = ⇒ in the ➔ But, in the general problem, proven to exist: Euler and ➔ And rotating central confjgurations. ➔ Chenciner-Montgomery remarkable fjgure-eight. ➔ Find: Symmetric Lagrangean minimizers ➔ Avoiding going to infjnity (coercivity) and collision

  69. 15. Symmetry and choreographies Chenciner–Montgomery Eight Choreography [ � ] x 1 ( t ) x 1 ( t + T 12 ) x 4 ( t ) x 4 ( t + T 12 ) x 5 ( t + T 12 ) x 2 ( t + T 12 ) x 5 ( t ) x 6 ( t ) x 2 ( t ) x 3 ( t ) x 6 ( t + T 12 ) x 3 ( t + T 12 ) Two symmetric 3 -choregraphies [ � ]

  70. 1 Poincaré, topology and the n -body problem 2 Periodic orbits, symmetries, geometry and Lagrangean mini- mizers 3 Qualitative features, analysis, modeling and computing 4 Explorations and crawlers: symmetry groups, loop spaces, critical points and interactive distributed computing 5 Human interaction: visualization, CLI and interfaces, 3D ma- nipulation and remote computations 6 Conclusions

  71. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  72. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  73. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  74. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  75. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  76. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  77. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  78. 16. Computers and geometry of orbits features. Restricted 3BP and perturbations: Copenhagen (Stromgren) mechanical, Karl Sundman (perturbographe), electronic Hénon (Nice), Broucke, Szebehely, Bruno, Carles Simó, Stuchi, Alessandra Celletti, Luigi Chierchia (Computer-assisted proofs), Krakow School, Hans Koch). dimensional Morse theory (computationally fjrst). ➔ Computing (periodic) orbits: simulations, ODE, qualitative ➔ What to expect on an orbit? Detecting chaos and instability . ➔ Existence. ➔ Symmetry group. ➔ Approximation. ➔ Stability. ➔ Global fmow. ➔ Try to put together a stratifjed singular infjnitely

  79. 18. Predicting planetary orbits in the Institute of Atomic Energy, I got a taste of computational computer: G.J. Sussman & al. University, the fjrst chair in this area in our country”. the Chair of Computational Mathematics of Moscow State accepted with great pleasure an ofger by I.G. Petrovskii to head mathematics and realized its exceptional potential. Thus, I SETUN in 1958. Sobolev recalled, about the 50’s: “Working Lvovich Sobolev, who built the ternary balanced computer MANIAC computer; and Nikolay Brusentsov with Sergei Ulam (and their numerical paradox) on Los Alamos mechanical computer). ➔ circa 200BCE: Antikythera Mechanism (earliest known ➔ Mechanical (orrery) ➔ After the Great Patriotic World War II: Fermi, Pasta and ➔ Digital Orrery (Caltech and MIT, 1984): special-purpose ➔ Jacques Laskar (BdL Paris): perturbation expansions.

  80. 18. Predicting planetary orbits in the Institute of Atomic Energy, I got a taste of computational computer: G.J. Sussman & al. University, the fjrst chair in this area in our country”. the Chair of Computational Mathematics of Moscow State accepted with great pleasure an ofger by I.G. Petrovskii to head mathematics and realized its exceptional potential. Thus, I SETUN in 1958. Sobolev recalled, about the 50’s: “Working Lvovich Sobolev, who built the ternary balanced computer MANIAC computer; and Nikolay Brusentsov with Sergei Ulam (and their numerical paradox) on Los Alamos mechanical computer). ➔ circa 200BCE: Antikythera Mechanism (earliest known ➔ Mechanical (orrery) ➔ After the Great Patriotic World War II: Fermi, Pasta and ➔ Digital Orrery (Caltech and MIT, 1984): special-purpose ➔ Jacques Laskar (BdL Paris): perturbation expansions.

  81. 18. Predicting planetary orbits in the Institute of Atomic Energy, I got a taste of computational computer: G.J. Sussman & al. University, the fjrst chair in this area in our country”. the Chair of Computational Mathematics of Moscow State accepted with great pleasure an ofger by I.G. Petrovskii to head mathematics and realized its exceptional potential. Thus, I SETUN in 1958. Sobolev recalled, about the 50’s: “Working Lvovich Sobolev, who built the ternary balanced computer MANIAC computer; and Nikolay Brusentsov with Sergei Ulam (and their numerical paradox) on Los Alamos mechanical computer). ➔ circa 200BCE: Antikythera Mechanism (earliest known ➔ Mechanical (orrery) ➔ After the Great Patriotic World War II: Fermi, Pasta and ➔ Digital Orrery (Caltech and MIT, 1984): special-purpose ➔ Jacques Laskar (BdL Paris): perturbation expansions.

  82. 18. Predicting planetary orbits in the Institute of Atomic Energy, I got a taste of computational computer: G.J. Sussman & al. University, the fjrst chair in this area in our country”. the Chair of Computational Mathematics of Moscow State accepted with great pleasure an ofger by I.G. Petrovskii to head mathematics and realized its exceptional potential. Thus, I SETUN in 1958. Sobolev recalled, about the 50’s: “Working Lvovich Sobolev, who built the ternary balanced computer MANIAC computer; and Nikolay Brusentsov with Sergei Ulam (and their numerical paradox) on Los Alamos mechanical computer). ➔ circa 200BCE: Antikythera Mechanism (earliest known ➔ Mechanical (orrery) ➔ After the Great Patriotic World War II: Fermi, Pasta and ➔ Digital Orrery (Caltech and MIT, 1984): special-purpose ➔ Jacques Laskar (BdL Paris): perturbation expansions.

  83. 18. Predicting planetary orbits in the Institute of Atomic Energy, I got a taste of computational computer: G.J. Sussman & al. University, the fjrst chair in this area in our country”. the Chair of Computational Mathematics of Moscow State accepted with great pleasure an ofger by I.G. Petrovskii to head mathematics and realized its exceptional potential. Thus, I SETUN in 1958. Sobolev recalled, about the 50’s: “Working Lvovich Sobolev, who built the ternary balanced computer MANIAC computer; and Nikolay Brusentsov with Sergei Ulam (and their numerical paradox) on Los Alamos mechanical computer). ➔ circa 200BCE: Antikythera Mechanism (earliest known ➔ Mechanical (orrery) ➔ After the Great Patriotic World War II: Fermi, Pasta and ➔ Digital Orrery (Caltech and MIT, 1984): special-purpose ➔ Jacques Laskar (BdL Paris): perturbation expansions.

  84. 19. What to add? infjnity? gsl, slatec, minuit, minpack, ...). Glued with paper clips, computing, computer algebra. calculus of variations, numerical analysis and scientifjc be approximate by fjnite-dimensional approximations? approximations are close to real solutions? Strong-force trick? Smoothing? Regularizations like Sundman or Levi-Civita or McGehee? python and duct tape. Kind of a minor sage-math? ➔ A template numerical optimization search with symbolic data ( O ( d ) , Σ n , ...) ➔ Collisions: what to do about near-colliding trajectories? ➔ Coercivity: what to do of minima or critical points at ➔ Visibility of critical points: when the fjnite-dimensional ➔ Closure: when the infjnite-dimensional critical point can ➔ Ingredients: Sobolev spaces, geometry and topology, = ⇒ A mixture of GAP, F95 and scientifjc libraries (IMSL,

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