Let $M^{ 2n}$ be a unitary torus $(2n)$-manifold, i.e., a $(2n)$-dimensional oriented stable complex connected closed $T^n$-manifold having a nonempty fixed set. In this paper we show that $M$ bounds equivariantly if and only if the equivariant Chern numbers $< (c_1^{ T^n})^i(c_2^{ T^n})^j, [M]>=0$ for all $i, j\in { \Bbb N}$, where $c_l^{ T^n}$ denotes the $l$th equivariant Chern class of $M$. As a consequence, we also show that if $M$ does not bound equivariantly then the number of fixed points is at least $\lceil{ n\over2}\rceil+1$.
Categories: math.AT math.DG