M. Marcus et L. Veron, BOUNDARY TRACE OF POSITIVE SOLUTIONS OF N ONLINEAR ELLIPTIC-EQUATIONS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 321(2), 1995, pp. 179-184
Let B be the unit open ball in R(N) and u a positive solution of (E) :
-Delta u + u(q) = 0, q > 1, in B. We prove that it is possible to def
ine the trace of u on partial derivative B by a unique couple (S, mu)
where S is a closed subset of partial derivative B and mu is a Radon m
easure on R = partial derivative B\S. The set S is the singular set of
the trace of a and the set R is the regular set where the trace of u
is mu.