Symmetry, Integrability and Geometry: Methods and Applications (SIGMA)


SIGMA 13 (2017), 021, 11 pages      arXiv:1608.00480      https://doi.org/10.3842/SIGMA.2017.021

Central Configurations and Mutual Differences

D.L. Ferrario
Department of Mathematics and Applications, University of Milano-Bicocca, Via R. Cozzi, 55 20125 Milano, Italy

Received December 06, 2016, in final form March 27, 2017; Published online March 31, 2017

Abstract
Central configurations are solutions of the equations $\lambda m_j\boldsymbol{q}_j = \frac{\partial U}{\partial \boldsymbol{q}_j}$, where $U$ denotes the potential function and each $\boldsymbol{q}_j$ is a point in the $d$-dimensional Euclidean space $E\cong {\mathbb R}^d$, for $j=1,\ldots, n$. We show that the vector of the mutual differences $\boldsymbol{q}_{ij} = \boldsymbol{q}_i - \boldsymbol{q}_j$ satisfies the equation $-\frac{\lambda}{\alpha} \boldsymbol{q} = P_m(\Psi(\boldsymbol{q}))$, where $P_m$ is the orthogonal projection over the spaces of $1$-cocycles and $\Psi(\boldsymbol{q}) = \frac{\boldsymbol{q}}{|\boldsymbol{q}|^{\alpha+2}}$. It is shown that differences $\boldsymbol{q}_{ij}$ of central configurations are critical points of an analogue of $U$, defined on the space of $1$-cochains in the Euclidean space $E$, and restricted to the subspace of $1$-cocycles. Some generalizations of well known facts follow almost immediately from this approach.

Key words: central configurations; relative equilibria; $n$-body problem.

pdf (400 kb)   tex (17 kb)

References

  1. Albouy A., Open problem 1: are Palmore's ''ignored estimates'' on the number of planar central configurations correct?, Qual. Theory Dyn. Syst. 14 (2015), 403-406, arXiv:1501.00694.
  2. Albouy A., Chenciner A., Le problème des $n$ corps et les distances mutuelles, Invent. Math. 131 (1998), 151-184.
  3. Albouy A., Kaloshin V., Finiteness of central configurations of five bodies in the plane, Ann. of Math. 176 (2012), 535-588.
  4. Fadell E.R., Husseini S.Y., Geometry and topology of configuration spaces, Springer Monographs in Mathematics, Springer-Verlag, Berlin, 2001.
  5. Fayçal N., On the classification of pyramidal central configurations, Proc. Amer. Math. Soc. 124 (1996), 249-258.
  6. Ferrario D.L., Planar central configurations as fixed points, J. Fixed Point Theory Appl. 2 (2007), 277-291.
  7. Ferrario D.L., Fixed point indices of central configurations, J. Fixed Point Theory Appl. 17 (2015), 239-251, arXiv:1412.5817.
  8. Hampton M., Moeckel R., Finiteness of relative equilibria of the four-body problem, Invent. Math. 163 (2006), 289-312.
  9. Iturriaga R., Maderna E., Generic uniqueness of the minimal Moulton central configuration, Celestial Mech. Dynam. Astronom. 123 (2015), 351-361, arXiv:1406.6887.
  10. Lang S., Fundamentals of differential geometry, Graduate Texts in Mathematics, Vol. 191, Springer-Verlag, New York, 1999.
  11. MacMillan W.D., Bartky W., Permanent configurations in the problem of four bodies, Trans. Amer. Math. Soc. 34 (1932), 838-875.
  12. Moeckel R., Relative equilibria of the four-body problem, Ergodic Theory Dynam. Systems 5 (1985), 417-435.
  13. Moeckel R., On central configurations, Math. Z. 205 (1990), 499-517.
  14. Moeckel R., Central configurations, in Central Configurations, Periodic Orbits, and Hamiltonian Systems, Adv. Courses Math. CRM Barcelona, Birkhäuser/Springer, Basel, 2015, 105-167.
  15. Moeckel R., Montgomery R., Symmetric regularization, reduction and blow-up of the planar three-body problem, Pacific J. Math. 262 (2013), 129-189, arXiv:1202.0972.
  16. Ouyang T., Xie Z., Zhang S., Pyramidal central configurations and perverse solutions, Electron. J. Differential Equations (2004), 106, 9 pages.
  17. Xia Z., Convex central configurations for the $n$-body problem, J. Differential Equations 200 (2004), 185-190.

Previous article  Next article   Contents of Volume 13 (2017)