Title: A Macdonald refined topological vertex,
Abstract: We consider the refined topological vertex of Iqbal et al, as a function of
two parameters (x, y), and deform it by introducing Macdonald parameters (q,
t), as in the work of Vuletic on plane partitions, to obtain 'a Macdonald
refined topological vertex'. In the limit q -> t, we recover the refined
topological vertex of Iqbal et al. In the limit x -> y, we obtain a
qt-deformation of the topological vertex of Aganagic et al. Copies of the
vertex can be glued to obtain qt-deformed 5D instanton partition functions that
have well-defined 4D limits and, for generic values of (q, t), contain
infinite-towers of poles for every pole in the limit q -> t.