2 papers
math.DG2025
Geography of pinched four-manifolds
Renato G. Bettiol, Mario Kummer, Ricardo A. E. Mendes
We prove several new restrictions on the Euler characteristic and signature of oriented 4-manifolds with (positively or negatively) pinched sectional curvature. In particular, we s…
math.AG2025
Ulrich sheaves, the arithmetic writhe and algebraic isotopies of space curves
Daniele Agostini, Mario Kummer
We establish a connection between the theory of Ulrich sheaves and -homotopy theory. For instance, we prove that the -degree of a morphism between proje…