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Elliptic cohomologies: an introductory survey.

Guillermo Moreno (1992)

Publicacions Matemàtiques

Let α and β be any angles then the known formula sin (α+β) = sinα cosβ + cosα sinβ becomes under the substitution x = sinα, y = sinβ, sin (α + β) = x √(1 - y2) + y √(1 - x2) =: F(x,y). This addition formula is an example of "Formal group law", which show up in many contexts in Modern Mathematics.In algebraic topology suitable cohomology theories induce a Formal group Law, the elliptic cohomologies are the ones who realize the Euler addition formula (1778): F(x,y) =: (x √R(y) + y √R(x)/1 - εx2y2)....

Embeddings of a family of Danielewski hypersurfaces and certain C + -actions on C 3

Lucy Moser-Jauslin, Pierre-Marie Poloni (2006)

Annales de l’institut Fourier

We consider the family of polynomials in C [ x , y , z ] of the form x 2 y - z 2 - x q ( x , z ) . Two such polynomials P 1 and P 2 are equivalent if there is an automorphism ϕ * of C [ x , y , z ] such that ϕ * ( P 1 ) = P 2 . We give a complete classification of the equivalence classes of these polynomials in the algebraic and analytic category. As a consequence, we find the following results. There are explicit examples of inequivalent polynomials P 1 and P 2 such that the zero set of P 1 + c is isomorphic to the zero set of P 2 + c for all c C . There exist polynomials which are algebraically...

Equations of some wonderful compactifications

Pascal Hivert (2011)

Annales de l’institut Fourier

De Concini and Procesi have defined the wonderful compactification X ¯ of a symmetric space X = G / G σ where G is a complex semisimple adjoint group and G σ the subgroup of fixed points of G by an involution σ . It is a closed subvariety of a Grassmannian of the Lie algebra 𝔤 of G . In this paper we prove that, when the rank of X is equal to the rank of G , the variety is defined by linear equations. The set of equations expresses the fact that the invariant alternate trilinear form w on 𝔤 vanishes on the ( - 1 ) -eigenspace...

Equidimensional actions of algebraic tori

Haruhisa Nakajima (1995)

Annales de l'institut Fourier

Let X be an affine conical factorial variety over an algebraically closed field of characteristic zero. We consider equidimensional and stable algebraic actions of an algebraic torus on X compatible with the conical structure. We show that such actions are cofree and the nullcones of X associated with them are complete intersections.

Equivariant principal bundles for G–actions and G–connections

Indranil Biswas, S. Senthamarai Kannan, D. S. Nagaraj (2015)

Complex Manifolds

Given a complex manifold M equipped with an action of a group G, and a holomorphic principal H–bundle EH on M, we introduce the notion of a connection on EH along the action of G, which is called a G–connection. We show some relationship between the condition that EH admits a G–equivariant structure and the condition that EH admits a (flat) G–connection. The cases of bundles on homogeneous spaces and smooth toric varieties are discussed.

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