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Register a new userAn obstruction to the smoothability of singular nonpositively curved metrics on 4-manifolds by patterns of incompressible tori
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Authors
Stephan Stadler
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We give new examples of closed smooth 4-manifolds which support singular metrics of nonpositive curvature, but no smooth ones, thereby answering affirmatively a question of Gromov. The obstruction comes from patterns of incompressible 2-tori sufficiently complicated to force branching of geodesics for nonpositively curved metrics.
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