运用Mawhin重合度理论,讨论一类半直线上三阶多点边值问题(q(t)x″(t))′=f(t,x(t),x′(t),x″(t)),a.e.t∈[0,+∞);■(η■在dim Ker L=2共振情形下的可解性,获得了该边值问题至少存在一个解的充分条件.这里f:[0,1]×R^(3)→R满足L^(1)[0,+∞)-Carathéodory条件,αi,βj∈R(1≤i≤m,1≤j≤n),0<ξ_(1)<ξ_(2)<…<ξ_(m)<+∞,0<η_(1)<η_(2)<…<η_(n)<+∞(m,n∈Z+),q(t)>0,q(t)∈C[0,+∞)∩C^(2)(0,+∞),1/q(t)∈L^(1)[0,+∞).
运用Mawhin重合度理论,讨论一类半直线上三阶多点边值问题{x″′(t)=f(t,x(t),x′(t),x″(t))+e(t),t∈[0,+∞),x(0)=m∑i=1α_(i)x(ξ_(i)),x(1)=n∑j=1β_(j)x(η_(j)),limt→+∞x′(t)=∑k=1lγkx″(ζk)在dim Ker L=3共振情形下解的存在性,f:[0,1]×R→R满足S-Carathéodory条件,e∈L1[0,∞),α_(i),β_(j),γk∈R,0<ξ1<ξ2<…<ξm<+∞,0<η1<η2<…<ηn<+∞,0<ζ_(1)<ζ_(2)<…<ζ_(l)<+∞(m,n,l∈Z^(+)),并且满足下列条件:(C1)m∑i=1α_(i)=1,m∑i=1α_(i)ξi=0,m∑i=1α_(i)ξ2i=0,∑j=1nβ_(j)=1,∑j=1nβ_(j)η_(j)=1,∑j=1nβ_(j)η2j=1,∑k=1lγk=1;(C2)Δ=∣∣∣∣Q_(1)e−tQ_(1)te−tQ_(1)t2e−tQ_(2)e−tQ_(2)te−tQ_(2)t2e−tQ_(3)e−tQ_(3)te−tQ_(3)t2e−t∣∣∣∣:=∣∣∣∣a_(11)a_(21)a_(31)a_(12)a_(22)a_(32)a_(13)a_(23)a_(33)∣∣∣∣≠0,其中,Q_(1)y=m∑i=1α_(i)∫ξi_(0)∫^(s)_(0)∫^(τ)_(0)y(v)dv dτds,Q_(2)y=∑j=1nβ_(j)∫^(η_(j))_(0)∫^(s)_(0)∫^(τ)_(0)y(v)dv dτds,Q_(3)y=l∑k=1γk∫^(+∞)_(γk)y(s)ds。
