We consider smooth, nonvanishing complex (not essentially real) vector fields L= X+ i Y that
satisfy the Nirenberg-Treves condition (P) and are allowed to possess some closed one …

In this work we deal with solvability of first‐order differential equations in the form, where L is
a planar complex vector field, elliptic everywhere except along a simple closed curve Σ on …

This paper deals with the solvability near the characteristic set Σ={0\} * S^ 1 Σ= 0× S 1 of
operators of the form L= ∂/∂ t+(x^ na (x)+ ixb (x)) ∂/∂ x, b (0) ≠ 0\,\rm and\,\, n ≧ 2,\,\rm …

In this work, we deal with solvability near the characteristic set of equations in the form Lu=
pu+ f, where the operator L=∂ t+(xna (x)+ ixb (x))∂ x is defined on Ω= R× S1, a and b are …

Esta dissertação expõe sobre a resolubilidade do campo vetorial complexo L= â/â t+(a (x)+
ib (x)) â/â x, b ⢠0 definido em Ω ε=(-ε, ε) à S1, ε> 0, perto do conjunto característico …