We show that a closed non-positively curved 4-manifold with negative Ricci curvature has positive Gromov's simplicial volume.
Links:
[1] https://www.mpim-bonn.mpg.de/taxonomy/term/39
[2] https://www.mpim-bonn.mpg.de/node/3444
[3] https://www.mpim-bonn.mpg.de/TopologySeminar