16,656 research outputs found

    On existence and uniqueness of the carrying simplex for competitive dynamical systems

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    Certain dynamical models of competition have a unique invariant hypersurface to whichevery nonzero tractory is asymptotic, having simple geometry and topology.Comment: Submitted to Journal of Biological Dynamics. 13 page

    Common zeros of inward vector fields on surfaces

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    A vector field X on a manifold M with possibly nonempty boundary is inward if it generates a unique local semiflow ΦX\Phi^X. A compact relatively open set K in the zero set of X is a block. The Poincar\'e-Hopf index is generalized to an index for blocks that may meet the boundary. A block with nonzero index is essential. Let X, Y be inward C1C^1 vector fields on surface M such that [X,Y]X=0[X,Y]\wedge X=0 and let K be an essential block of zeros for X. Among the main results are that Y has a zero in K if X and YY are analytic, or Y is C2C^2 and ΦY\Phi^Y preserves area. Applications are made to actions of Lie algebras and groups

    Zero sets of Lie algebras of analytic vector fields on real and complex 2-manifolds

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    Let X be an analytic vector field on a real or complex 2-manifold, and K a compact set of zeros of X whose fixed point index is not zero. Let A denote the Lie algebra of analytic vector fields Y on M such that at every point of M the values of X and [X,Y] are linearly dependent. Then the vector fields in A have a common zero in K. Application: Let G be a connected Lie group having a 1-dimensional normal subgroup. Then every action of G on M has a fixed point.Comment: 22 page

    Meissner effect, Spin Meissner effect and charge expulsion in superconductors

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    The Meissner effect and the Spin Meissner effect are the spontaneous generation of charge and spin current respectively near the surface of a metal making a transition to the superconducting state. The Meissner effect is well known but, I argue, not explained by the conventional theory, the Spin Meissner effect has yet to be detected. I propose that both effects take place in all superconductors, the first one in the presence of an applied magnetostatic field, the second one even in the absence of applied external fields. Both effects can be understood under the assumption that electrons expand their orbits and thereby lower their quantum kinetic energy in the transition to superconductivity. Associated with this process, the metal expels negative charge from the interior to the surface and an electric field is generated in the interior. The resulting charge current can be understood as arising from the magnetic Lorentz force on radially outgoing electrons, and the resulting spin current can be understood as arising from a spin Hall effect originating in the Rashba-like coupling of the electron magnetic moment to the internal electric field. The associated electrodynamics is qualitatively different from London electrodynamics, yet can be described by a small modification of the conventional London equations. The stability of the superconducting state and its macroscopic phase coherence hinge on the fact that the orbital angular momentum of the carriers of the spin current is found to be exactly /2\hbar/2, indicating a topological origin. The simplicity and universality of our theory argue for its validity, and the occurrence of superconductivity in many classes of materials can be understood within our theory.Comment: Submitted to SLAFES XX Proceeding
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