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If is a morphism of varieties over , then we define the push-forward of with respect to as the cycle , where the degree of is defined as if is generically finite and we set if . By restriction, the push-forward can be defined in the same way on prime cycles of and extends by linearity to all cycles of .
Now let be a moment map of the open subset of . By 4.6,
is a tropical cycle on . If is generically finite, then this tropical cycle is of pure dimension and the support is equal to (see Lemma 4.9).