(1) CMLA, CNRS URA 1611, ENS-CACHAN, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France. e-mail
Abstract:
We prove that the maps from S2 intoS1 having a finite number of isolated singularities ofdegree ±1 are dense for the strong topology inH1/2(S2, S1). We also prove that smooth maps are densein H1/2(S2, S1)for the sequentially weak topology andthat this is no more the case in Hs(S2, S1) for s> 1/2.