Search results for "M20"

showing 2 items of 12 documents

Optimal control with state constraints and the space shuttle re-entry problem

2003

In this article, we initialize the analysis under generic assumptions of the small \textit{time optimal synthesis} for single input systems with \textit{state constraints}. We use geometric methods to evaluate \textit{the small time reachable set} and necessary optimality conditions. Our work is motivated by the \textit{optimal control of the atmospheric arc for the re-entry of a space shuttle}, where the vehicle is subject to constraints on the thermal flux and on the normal acceleration. A \textit{multiple shooting technique} is finally applied to compute the optimal longitudinal arc.

[ MATH.MATH-OC ] Mathematics [math]/Optimization and Control [math.OC]Minimum principleMultiple shooting techniques49K15 70M2049M15Control of the atmospheric arc[MATH.MATH-OC] Mathematics [math]/Optimization and Control [math.OC]Optimal control with state constraints[MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC]
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On the CAT(0) dimension of 2-dimensional Bestvina-Brady groups

2002

Let K be a 2-dimensional finite flag complex. We study the CAT(0) dimension of the `Bestvina-Brady group', or `Artin kernel', Gamma_K. We show that Gamma_K has CAT(0) dimension 3 unless K admits a piecewise Euclidean metric of non-positive curvature. We give an example to show that this implication cannot be reversed. Different choices of K lead to examples where the CAT(0) dimension is 3, and either (i) the geometric dimension is 2, or (ii) the cohomological dimension is 2 and the geometric dimension is not known.

nonpositive curvatureGroup (mathematics)20F6720F67 57M20Geometric Topology (math.GT)Group Theory (math.GR)Cohomological dimensionEuclidean distanceCombinatoricsKernel (algebra)Mathematics::Group TheoryMathematics - Geometric Topologydimension57M20Dimension (vector space)FOS: MathematicsArtin groupflag complexGeometry and TopologyArtin groupMathematics - Group TheoryZero-dimensional spaceMathematicsFlag (geometry)
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