The local Harnack inequality bounds from above the number of ovals which can appear in a small perturbation of a singular point. As is known, there are singular points for which this bound is not sharp. We show that Harnack inequality is sharp in any complex topologically equisingular class: every real plane curve singular point is complex deformation equivalent to a real singularity for which Harnack inequality is sharp. For semi-quasi-homogeneous and some other singularities we exhibit a real deformation with the same property. A refined Harnack inequality and its sharpness are discussed also.
@article{hal-00129577,
author = {Kharlamov, Viatcheslav and Risler, Jean-Jacques and Shustin, Eugenii},
title = {Maximal smoothings of real plane curve singular points.},
journal = {HAL},
volume = {1998},
number = {0},
year = {1998},
language = {en},
url = {http://dml.mathdoc.fr/item/hal-00129577}
}
Kharlamov, Viatcheslav; Risler, Jean-Jacques; Shustin, Eugenii. Maximal smoothings of real plane curve singular points.. HAL, Tome 1998 (1998) no. 0, . http://gdmltest.u-ga.fr/item/hal-00129577/