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Generalized Wilczynski invariants for non-linear ordinary differential equations  [PDF]
Boris Doubrov
Mathematics , 2007,
Abstract: We show that classical Wilczynski--Se-ashi invariants of linear systems of ordinary differential equations are generalized in a natural way to contact invariants of non-linear ODEs. We explore geometric structures associated with equations that have vanishing generalized Wilczynski invariants and establish relationship of such equations with deformation theory of rational curves on complex algebraic surfaces.
Affine invariants of annuli
Waldemar Cie lak, El bieta Szczygielska
Annales UMCS, Mathematica , 2012, DOI: 10.2478/v10062-012-0002-4
Abstract: A family of regular annuli is considered. Affine invariants of annuli are introduced.
Cutting Affine Moment Invariants
Jianwei Yang,Ming Li,Zirun Chen,Yunjie Chen
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/928161
Abstract: The extraction of affine invariant features plays an important role in many fields of image processing. In this paper, the original image is transformed into new images to extract more affine invariant features. To construct new images, the original image is cut in two areas by a closed curve, which is called general contour (GC). GC is obtained by performing projections along lines with different polar angles. New image is obtained by changing gray value of pixels in inside area. The traditional affine moment invariants (AMIs) method is applied to the new image. Consequently, cutting affine moment invariants (CAMIs) are derived. Several experiments have been conducted to evaluate the proposed method. Experimental results show that CAMIs can be used in object classification tasks.
Some Affine Invariants Revisited  [PDF]
Alina Stancu
Mathematics , 2012,
Abstract: We present several sharp inequalities for the SL(n) invariant $\Omega_{2,n}(K)$ introduced in our earlier work on centro-affine invariants for smooth convex bodies containing the origin. A connection arose with the Paouris-Werner invariant $\Omega_K$ defined for convex bodies $K$ whose centroid is at the origin. We offer two alternative definitions for $\Omega_K$ when $K \in C^2_+$. The technique employed prompts us to conjecture that any SL(n) invariant of convex bodies with continuous and positive centro-affine curvature function can be obtained as a limit of normalized $p$-affine surface areas of the convex body.
Casimir Invariants for Quantized Affine Lie Algebras  [PDF]
M. D. Gould,Y. -Z. Zhang
Physics , 1993, DOI: 10.1007/BF00751173
Abstract: Casimir invariants for quantized affine Lie algebras are constructed and their eigenvalues computed in any irreducible highest weight representation.
Centro-Affine Invariants for Smooth Convex Bodies  [PDF]
Alina Stancu
Mathematics , 2010,
Abstract: Employing a centro-affine flow on smooth convex bodies, we generate new centro-affine differential invariants. One class of the newly defined invariants is the object of a sharp isoperimetric inequality, while other new inequalities on known centro-affine invariants are obtained as a byproduct of the flow's study. Furthermore, this approach led to a geometric interpretation of a new affine surface area recently introduced by Ludwig and Reitzner.
On stably free modules over affine algebras  [PDF]
Jean Fasel,Richard G. Swan,Ravi A. Rao
Mathematics , 2011, DOI: 10.1007/s10240-012-0041-y
Abstract: We prove that stably free modules of rank d-1 over a smooth affine algebra of dimension d over an algebraically closed field k are free, provided (d-1)! is nonzero in k.
Characterization of accessibility for affine connection control systems at some points with nonzero velocity  [PDF]
María Barbero-Li?án
Mathematics , 2011,
Abstract: Affine connection control systems are mechanical control systems that model a wide range of real systems such as robotic legs, hovercrafts, planar rigid bodies, rolling pennies, snakeboards and so on. In 1997 the accessibility and a particular notion of controllability was intrinsically described by A. D. Lewis and R. Murray at points of zero velocity. Here, we present a novel generalization of the description of accessibility algebra for those systems at some points with nonzero velocity as long as the affine connection restricts to the distribution given by the symmetric closure. The results are used to describe the accessibility algebra of different mechanical control systems.
Geometry of Control-Affine Systems  [cached]
Jeanne N. Clelland,Christopher G. Moseley,George R. Wilkens
Symmetry, Integrability and Geometry : Methods and Applications , 2009,
Abstract: Motivated by control-affine systems in optimal control theory, we introduce the notion of a point-affine distribution on a manifold X – i.e., an affine distribution F together with a distinguished vector field contained in F. We compute local invariants for point-affine distributions of constant type when dim(X) = n, rank(F) = n–1, and when dim(X) = 3, rank(F) = 1. Unlike linear distributions, which are characterized by integer-valued invariants – namely, the rank and growth vector – when dim(X) ≤ 4, we find local invariants depending on arbitrary functions even for rank 1 point-affine distributions on manifolds of dimension 2.
Geometry of Control-Affine Systems  [PDF]
Jeanne N. Clelland,Christopher G. Moseley,George R. Wilkens
Mathematics , 2009, DOI: 10.3842/SIGMA.2009.095
Abstract: Motivated by control-affine systems in optimal control theory, we introduce the notion of a point-affine distribution on a manifold X - i.e., an affine distribution F together with a distinguished vector field contained in F. We compute local invariants for point-affine distributions of constant type when dim(X)=n, rank(F)=n-1, and when dim(X)=3, rank(F)=1. Unlike linear distributions, which are characterized by integer-valued invariants - namely, the rank and growth vector - when dim(X)<=4, we find local invariants depending on arbitrary functions even for rank 1 point-affine distributions on manifolds of dimension 2.
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