Chapter 3 Conformal equivalence and the Poincaré index

2019 ◽  
Vol 161 (3-4) ◽  
pp. 487-499
Author(s):  
Fabiano G. B. Brito ◽  
André O. Gomes ◽  
Icaro Gonçalves

Author(s):  
P. P. Zabreiko ◽  
A. V. Krivko-Krasko

The conditions of isolation of a zero singular point of plane polynomial fields of third and fourth degree are considered in terms of the coefficients of the components of these fields. The isolation conditions depend on the greatest common divisor of the components of polynomial fields: in some cases only on its degree, and in some cases, additionally, on the presence of nonzero real zeros. The reasoning, which allows one to write out the isolation conditions, is based on the concept of the resultant and subresultants of components of plane polynomial fields. If the zero singular point is isolated, its index is calculated through the values of subresultants and coefficients of components.


2015 ◽  
Vol 37 (2) ◽  
pp. 572-605
Author(s):  
FRÉDÉRIC LE ROUX

We use the homotopy Brouwer theory of Handel to define a Poincaré index between pairs of orbits for an orientation-preserving fixed-point-free homeomorphism of the plane. Furthermore, we prove that this index is almost additive.


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