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Families of functions dominated by distributions of C -classes of mappings

Goo Ishikawa (1983)

Annales de l'institut Fourier

A subsheaf of the sheaf Ω of germs C functions over an open subset Ω of R n is called a sheaf of sub C function. Comparing with the investigations of sheaves of ideals of Ω , we study the finite presentability of certain sheaves of sub C -rings. Especially we treat the sheaf defined by the distribution of Mather’s 𝒞 -classes of a C mapping.

Felix Klein's paper on real flexes vindicated

Felice Ronga (1998)

Banach Center Publications

In a paper written in 1876 [4], Felix Klein gave a formula relating the number of real flexes of a generic real plane projective curve to the number of real bitangents at non-real points and the degree, which shows in particular that the number of real flexes cannot exceed one third of the total number of flexes. We show that Klein's arguments can be made rigorous using a little of the theory of singularities of maps, justifying in particular his resort to explicit examples.

Final forms for a three-dimensional vector field under blowing-up

Felipe Cano (1987)

Annales de l'institut Fourier

We study the final situations which may be obtained for a singular vector field by permissible blowing-ups of the ambient space (in dimension three). These situations are preserved by permissible blowing-ups and its structure is simple from the view-point of the integral branches. Technically, we take a logarithmic approach, by marking in each step the exceptional divisor of the transformation.

Flows near compact invariant sets. Part I

Pedro Teixeira (2013)

Fundamenta Mathematicae

It is proved that near a compact, invariant, proper subset of a C⁰ flow on a locally compact, connected metric space, at least one, out of twenty eight relevant dynamical phenomena, will necessarily occur. Theorem 1 shows that the connectedness of the phase space implies the existence of a considerably deeper classification of topological flow behaviour in the vicinity of compact invariant sets than that described in the classical theorems of Ura-Kimura and Bhatia. The proposed classification brings...

Foliations by curves with curves as singularities

M. Corrêa Jr, A. Fernández-Pérez, G. Nonato Costa, R. Vidal Martins (2014)

Annales de l’institut Fourier

Let be a holomorphic one-dimensional foliation on n such that the components of its singular locus Σ are curves C i and points p j . We determine the number of p j , counted with multiplicities, in terms of invariants of and C i , assuming that is special along the C i . Allowing just one nonzero dimensional component on Σ , we also prove results on when the foliation happens to be determined by its singular locus.

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