title: Symmetric array of off-axis singular beams: spiral beams and their critical points.
abstract: We consider conditions of structural stability under which the array of singular beams preserves its topological structure and intensity distribution while slightly perturbing its intrinsic parameters. The orbital angular momentum of the array as a function of the array parameters is a characteristic function, and its extreme points correspond to stable and unstable array states.
authors.affiliation: Department of Physics, Taurida National V. Vernandsky University, Vernadsky Av. 4, Simferopol 95007, Crimea, Ukraine.
authors.forename: Yana
authors.initials: Y
authors.lastname: Izdebskaya
authors.forename: Vladlen
authors.initials: V
authors.lastname: Shvedov
authors.forename: Alexander
authors.initials: A
authors.lastname: Volyar