First, under some very mild growth conditions, we show that problem (1) is equivalent to the integral equation
where G(x,y)den">de"> is the Green's function associated with de288007b0" title="Click to view the MathML source">(−Δ)mden">de"> in Rnden">de">.Then by using the method of moving planes in integral forms, we prove that there is no positive solution for integral equation (2) in subcritical cases 160" class="mathmlsrc">160.gif&_user=111111111&_pii=S0022247X16301883&_rdoc=1&_issn=0022247X&md5=9848f8803f82be1507a541a986b98ad1">160.gif">den">de">. For the non-existence of positive radially symmetric solutions, we can extend the range to subcritical cases
den">de">. This partially solves an open conjecture posed by Quoc Hung Phan and Philippe Souplet [21].