In a nonlinear optical waveguide with defocusing Kerr-type nonlinearity. we discuss the existence of a type of stationary nonlinear waves with propagation-invariant density profiles. consisting of vortices located at the vertices of a regular polygon with or without an anti-vortex at its center. These polygons rotate around the center of the system and we provide approximate expressio... https://fitnessgravesyardes.shop/product-category/drive-motor-w-flywheel/