Stability of Relative Equilibria in the Planar N-Vortex Problem

We study the linear and nonlinear stability of relative equilibria in the planar N-vortex problem, adapting the approach of Moeckel from the corresponding problem in celestial mechanics. After establishing some general theory, a topological approach is taken to show that for the case of positive circulations, a relative equilibrium is linearly stable if and only if it is a nondegenerate minimum of the Hamiltonian restricted to a level surface of the angular impulse (moment of inertia). Using a criterion of Dirichlet's, this implies that any linearly stable relative equilibrium with positive vorticities is also nonlinearly stable. Two symmetric families, the rhombus and the isosceles trapezoid, are analyzed in detail, with stable solutions found in each case.Comment: 23 pages, 3 figure

[Review of] Joseph Bruchac, ed. Songs from This Earth on Turtle\u27s Back

Poetry by American Indians may be traced to the writings of John Rollin Ridge, a Cherokee who came to California in the early 1850s, edited several northern California newspapers, and helped create the legend of Joaquin Murieta, and to the works of Alexander Posey, a Creek who wrote romantic nature poems and dialect stories in the style of the local colorists. Nonetheless, few Indian poets existed prior to the 1970s. Since then, there has been a tremendous surge in the numbers of Indians writing poetry, and their work has received a great deal of critical acclaim, as evidenced by the attention given to James Welch\u27s Riding the Earthboy 40, Wendy Rose\u27s Lost Copper, and Maurice Kenny\u27s The Mama Poems, which garnered the American Book Award for 1984

Baby Chick Troubles and Their Control

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English fiddling 1650-1850 : reconstructing a lost idiom

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