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Resumen:
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If F and G are disjoint compact surfaces with boundary in S3=?D4, let F? and G? be the result of pushing F and G into the interior of D4, keeping ?F and ?G fixed. The authors give an explicit cut and paste description of an irregular 3-fold branched cover W4(F,G) of D4 branched along F?G. If M3=?W4(F,G), they say that (F,G) "represents M3 by bands''. Their main result is that any closed oriented 3-manifold can be so represented. In particular, any such 3-manifold bounds a simply connected W4 which is an irregular 3-fold branched cover of D4. Moreover, F and G can always be chosen in a rather special form which leads to a formula for the ?-invariant of M3 when M3 is a (Z/2)-homology sphere.
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