Abstract. By employing a regularizing transformation, the problem of bifurcation of relative equilibria in the Newtonian 4-body problem is reduced to a study of an algebraic correspondence between real algebraic varieties. The finiteness theorems of algebraic geometry are used to find an upper bound for the number of affine equivalence classes of relative equilibria which holds for all masses in the complement of a proper, algebraic subset of the space of all masses.
Introduction; relative equilibria of the N-body problemThe Newtonian TV-body problem concerns the motion of TV point masses under the influence of their mutual gravitational attraction. We will consider the case when all the particles move in a fixed plane which we take to be the complex plane, C. The position vector zeC N is the vector (z,, ...,z n ) where z,-= x,-+ iy,-£ C is the position of the yth particle. The mass vector m e R n+ is (m l ,..., m N ) where m, is the mass of the jth particle. In complex notation, Newton's laws are: