1,503 research outputs found
The Integer Valued SU(3) Casson Invariant for Brieskorn spheres
We develop techniques for computing the integer valued SU(3) Casson
invariant. Our method involves resolving the singularities in the flat moduli
space using a twisting perturbation and analyzing its effect on the topology of
the perturbed flat moduli space. These techniques, together with Bott-Morse
theory and the splitting principle for spectral flow, are applied to calculate
the invariant for all Brieskorn homology spheres.Comment: 50 pages, 3 figure
Structural dynamic interaction with solar tracking control for evolutionary Space Station concepts
The sun tracking control system design of the Solar Alpha Rotary Joint (SARJ) and the interaction of the control system with the flexible structure of Space Station Freedom (SSF) evolutionary concepts are addressed. The significant components of the space station pertaining to the SARJ control are described and the tracking control system design is presented. Finite element models representing two evolutionary concepts, enhanced operations capability (EOC) and extended operations capability (XOC), are employed to evaluate the influence of low frequency flexible structure on the control system design and performance. The design variables of the control system are synthesized using a constrained optimization technique to meet design requirements, to provide a given level of control system stability margin, and to achieve the most responsive tracking performance. The resulting SARJ control system design and performance of the EOC and XOC configurations are presented and compared to those of the SSF configuration. Performance limitations caused by the low frequency of the dominant flexible mode are discussed
Relativistic Shock Acceleration: A Hartree-Fock Approach
We examine the problem of particle acceleration at a relativistic shocks
assuming pitch-angle scattering and using a Hartree-Fock method to approximate
the associated eigenfunctions. This leads to a simple transcendental equation
determining the power-law index, , given the up and downstream velocities.
We compare our results with accurate numerical solutions obtained using the
eigenfunction method. In addition to the power-law index this method yields the
angular and spatial distributions upstream of the shock.Comment: 4 pages, 2 figures, proceedings of the "4th Heidelberg International
Symposium on High Energy Gamma-Ray Astronomy" July 7-11, 2008, Heidelberg,
German
Gauge Theoretic Invariants of, Dehn Surgeries on Knots
New methods for computing a variety of gauge theoretic invariants for
homology 3-spheres are developed. These invariants include the Chern-Simons
invariants, the spectral flow of the odd signature operator, and the rho
invariants of irreducible SU(2) representations. These quantities are
calculated for flat SU(2) connections on homology 3-spheres obtained by 1/k
Dehn surgery on (2,q) torus knots. The methods are then applied to compute the
SU(3) gauge theoretic Casson invariant (introduced in [H U Boden and C M
Herald, The SU(3) Casson invariant for integral homology 3--spheres, J. Diff.
Geom. 50 (1998) 147-206]) for Dehn surgeries on (2,q) torus knots for q=3,5,7
and 9.Comment: Version 3: minor corrections from version 2. Published by Geometry
and Topology at http://www.maths.warwick.ac.uk/gt/GTVol5/paper6.abs.htm
A symplectic manifold homeomorphic but not diffeomorphic to CP\u3csup\u3e2\u3c/sup\u3e # 3CP\u3csup\u3e2\u3c/sup\u3e
In this article we construct a minimal symplectic 4-manifold and prove it is homeomorphic but not diffeomorphic to CP # 3CP . © 2008 Mathematical Sciences Publishers. 2
On the rho invariant for manifolds with boundary
This article is a follow up of the previous article of the authors on the
analytic surgery of eta- and rho-invariants. We investigate in detail the
(Atiyah-Patodi-Singer)-rho-invariant for manifolds with boundary. First we
generalize the cut-and-paste formula to arbitrary boundary conditions. A priori
the rho-invariant is an invariant of the Riemannian structure and a
representation of the fundamental group. We show, however, that the dependence
on the metric is only very mild: it is independent of the metric in the
interior and the dependence on the metric on the boundary is only up to its
pseudo--isotopy class. Furthermore, we show that this cannot be improved: we
give explicit examples and a theoretical argument that different metrics on the
boundary in general give rise to different rho-invariants. Theoretically, this
follows from an interpretation of the exponentiated rho-invariant as a
covariantly constant section of a determinant bundle over a certain moduli
space of flat connections and Riemannian metrics on the boundary. Finally we
extend to manifolds with boundary the results of Farber-Levine-Weinberger
concerning the homotopy invariance of the rho-invariant and spectral flow of
the odd signature operator.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol3/agt-3-22.abs.htm
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