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The covering semigroup of invariant control systems on Lie groups

Víctor Ayala, Eyüp Kizil (2016)

Kybernetika

It is well known that the class of invariant control systems is really relevant both from theoretical and practical point of view. This work was an attempt to connect an invariant systems on a Lie group G with its covering space. Furthermore, to obtain algebraic properties of this set. Let G be a Lie group with identity e and Σ 𝔤 a cone in the Lie algebra 𝔤 of G that satisfies the Lie algebra rank condition. We use a formalism developed by Sussmann, to obtain an algebraic structure on the covering...

The cuspidal torsion packet on hyperelliptic Fermat quotients

David Grant, Delphy Shaulis (2004)

Journal de Théorie des Nombres de Bordeaux

Let 7 be a prime, C be the non-singular projective curve defined over by the affine model y ( 1 - y ) = x , the point of C at infinity on this model, J the Jacobian of C , and φ : C J the albanese embedding with as base point. Let ¯ be an algebraic closure of . Taking care of a case not covered in [12], we show that φ ( C ) J tors ( ¯ ) consists only of the image under φ of the Weierstrass points of C and the points ( x , y ) = ( 0 , 0 ) and ( 0 , 1 ) , where J tors denotes the torsion points of J .

The deformation relation on the set of Cohen-Macaulay modules on a quotient surface singularity

Trond Stølen Gustavsen, Runar Ile (2011)

Banach Center Publications

Let X be a quotient surface singularity, and define G d e f ( X , r ) as the directed graph of maximal Cohen-Macaulay (MCM) modules with edges corresponding to deformation incidences. We conjecture that the number of connected components of G d e f ( X , r ) is equal to the order of the divisor class group of X, and when X is a rational double point (RDP), we observe that this follows from a result of A. Ishii. We view this as an enrichment of the McKay correspondence. For a general quotient singularity X, we prove the conjecture...

The degree at infinity of the gradient of a polynomial in two real variables

Maciej Sękalski (2005)

Annales Polonici Mathematici

Let f:ℝ² → ℝ be a polynomial mapping with a finite number of critical points. We express the degree at infinity of the gradient ∇f in terms of the real branches at infinity of the level curves {f(x,y) = λ} for some λ ∈ ℝ. The formula obtained is a counterpart at infinity of the local formula due to Arnold.

The degree of the secant variety and the join of monomial curves.

Kristian Ranestad (2006)

Collectanea Mathematica

A monomial curve is a curve parametrized by monomials. The degree of the secant variety of a monomial curve is given in terms of the sequence of exponents of the monomials defining the curve. Likewise, the degree of the join of two monomial curves is given in terms of the two sequences of exponents.

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