%0 Journal Article %A Gallardo Gutiérrez, Eva A. %A González Doña, Javier %A Tradacete Pérez, Pedro %T Invariant subspaces for positive operators on Banach spaces with unconditional basis %D 2022 %@ 0002-9939 %U https://hdl.handle.net/20.500.14352/71793 %X We prove that every lattice homomorphism acting on a Banach space X with the lattice structure given by an unconditional basis has a non-trivial closed invariant subspace. In fact, it has a non-trivial closed invariant ideal, which is no longer true for every positive operator on such a space. Motivated by these examples, we characterize tridiagonal positive operators without non-trivial closed invariant ideals on X extending to this context a result of Grivaux on the existence of non-trivial closed invariant subspaces for tridiagonal operators. %~