arXiv subjects

D. L. Ferrario

Publications and source records attributed to D. L. Ferrario.

4 recordsLinked to original sources

arXiv2024

Symmetries and periodic orbits for the $n$-body problem: about the computational approach

The main problem is to understand and to find periodic symmetric orbits in the $n$-body problem, in the sense of finding methods to prove or compute their existence, and more importantly to describe their qualitative and quantitative properties. In order to do so, and in order to classify such orbits and their symmetries, computers have been extensively used in many ways since decades. We will focus on some very special symmetric orbits, which occur as symmetric critical points (local minimizers) of the gravitational Lagrangean action functional. The exploration of the loop space of the $n$-point configuration space, raised some computational and mathematical questions that couldd be interesting. The aim of the article is to explain how such questions and issues were % considered in the development of a software package that combined symbolic algebra, numerical and scientific libraries, human interaction and visualization.

math.CA↗

arXiv2020

Fixed points and the inverse problem for central configurations

Central configurations play an important role in the dynamics of the $n$-body problem: they occur as relative equilibria and as asymptotic configurations in colliding trajectories. We illustrate how they can be found as projective fixed points of self-maps defined on the shape space, and some results on the inverse problem in dimension $1$, i.e. finding (positive or real) masses which make a given collinear configuration central. This survey article introduces readers to the recent results of the author, also unpublished, showing an application of the fixed point theory.

math.DS↗

arXiv2017

Central Configurations and Mutual Differences

Central configurations are solutions of the equations $λm_j\boldsymbol{q}_j = \frac{\partial U}{\partial \boldsymbol{q}_j}$, 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 $-\fracλα \boldsymbol{q} = P_m(Ψ(\boldsymbol{q}))$, where $P_m$ is the orthogonal projection over the spaces of $1$-cocycles and $Ψ(\boldsymbol{q}) = \frac{\boldsymbol{q}}{|\boldsymbol{q}|^{α+2}}$. 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.

math.DS↗

arXiv2016

Central configurations, Morse and fixed point indices

We compute the fixed point index of non-degenerate central configurations for the $n$-body problem in the euclidean space of dimension $d$, relating it to the Morse index of the gravitational potential function $\bar U$ induced on the manifold of all maximal $O(d)$-orbits. In order to do so, we analyze the geometry of maximal orbit type manifolds, and compute Morse indices with respect to the mass-metric bilinear form on configuration spaces.

math.DS↗