Existence and multiplicity of positive solutions to nonlinear first-order PBVPs on time scales

In this paper, we consider the following nonlinear first-order periodic boundary value problems on time scales {xΔ(t)+p(t)x(σ(t))=f(x(t)),t∈[0,T]T,x(0)=x(σ(T)). Some new existence and multiplicity criteria of positive solutions are established by using several well-known fixed point theorems.