Complemented Copies of $c_{0}$ in Positive Tensor Products of Banach Lattices

Abstract: A result of Cembranos states that a non-trivial injective tensor product of a $C$-space contains a complemented copy of $c_{0}$, and in particular fails the Grothendieck property. We establish a positive analogue of the Cembranos theorem for tensor products of Banach lattices. If $E$ and $F$ are infinite dimensional Banach lattices, with $E$ containing $c_{0}$ and $E<sup>{\ast}$ or $F<sup>{\ast}$ having the bounded positive approximation property, then the Wittstock tensor product $E\widetilde{\otimes}<em>{\vert{\varepsilon}\vert}F$ contains a complemented copy of $c</em>{0}$. If $F$ is in addition reflexive, then $E\widetilde{\otimes}_{\vert{\varepsilon}\vert}F$ fails the positive Grothendieck property.