John Christian Ottem


Department of Mathematics
University of Oslo
Box 1053, Blindern
0316 Oslo
Norway

Email: johnco@math.uio.no
Office: B1109


Research

My research interests are in algebraic geometry, in particular birational geometry, Calabi-Yau manifolds, and Hodge theory.

Algebraic geometry group at UiO
Algebra/algebraic geometry seminar at UiO.

CV

Events

Moduli and Algebraic Cycles Research programme at the Mittag-Leffler Institute, Fall 2021.
Enumeration and Moduli: A conference in algebraic geometry on the occasion of Geir Ellingsrud's 70th birthday. December 6-8 2018, University of Oslo.
Combinatorics and Hodge theory. 18-22 June 2018, Sophus Lie Conference Center, Nordfjordeid, Norway.
Geometry of Moduli. August 7, 2017 - Aug. 11, 2017, Lofoten, Norway.
Polar geometry: A conference celebrating the work of Ragni Piene on the occasion of her 70th birthday. January 26-28, 2017, University of Oslo.
Nordfjordeid Summer School: Stability conditions on triangulated categories and geometric applications. June 13-17, 2016, Sophus Lie Conference Center, Nordfjordeid, Norway.


Publications

  1. A pencil of Enriques surfaces with non-algebraic integral Hodge classes (with F. Suzuki) (2019)
  2. On deformations of quintic and septic hypersurfaces (with S. Schreieder) (2018)
  3. Remarks on the positivity of the cotangent bundle of a K3 surface (with F. Gounelas) (2018)
  4. Curve classes on irreducible holomorphic symplectic varieties (with G. Mongardi) (2018)
  5. Failure of the integral Hodge conjecture for threefolds of Kodaira dimension zero (with O. Benoist). To appear in Commentarii Mathematici Helvetici (2018)
  6. A counterexample to the birational Torelli problem for Calabi-Yau 3-folds (with J. V. Rennemo). Journal of the London Mathematical Society 97 (2018), 427-440
  7. Positivity of the diagonal (with B. Lehmann). Advances in Mathematics 335 (2018), 664-695.
  8. Effective cones of cycles on blow-ups of projective space (with I. Coskun, J. Lesieutre). Algebra & Number Theory 10-9 (2016).
  9. Nef cycles on some hyperkahler fourfolds. To appear in the LMS volume for Fulton 80 (2016)
  10. Curves disjoint from a nef divisor (with J. Lesieutre). Michigan Mathematical Journal 65 (2016), 321-332.
  11. On subvarieties with ample normal bundle. Journal of the European Mathematical Society 18 (2016), 2459-2468
  12. Birational geometry of hypersurfaces in products of projective spaces. Mathematische Zeitschrift 280 (2015), 135-148
  13. Quartic spectrahedra (with K. Ranestad, B. Sturmfels, C. Vinzant) Math. Prog. B (2015).
  14. Ample subvarieties and q-ample divisors. Advances in Mathematics 229 (2012), 2868-2887.
  15. Partially ample line bundles on toric varieties. (with N. Broomhead and A. Prendergast-Smith). Glasgow Math. J. 58 (2016)
  16. Algebraic boundaries of Hilbert's SOS cones (with G. Blekherman, J. Hauenstein, K. Ranestad and B. Sturmfels). Compositio Mathematica 148 (2012).
  17. Components of the Hilbert scheme of space curves on low-degree smooth surfaces (with J. O. Kleppe). International Journal of Mathematics Vol. 26, (2015)
  18. The Cox ring of a K3 surface of Picard number two. Journal of Pure and Applied Algebra 217 (2013), 709-715.
  19. On the Cox Ring of P2 Blown Up in Points on a Line. Mathematica Scandinavica 9, (2011), 21-31.

Other

Students

Bernt Ivar Utstøl Nødland
Bjørn Skauli

Teaching

This fall I am teaching MAT4200 - Commutative Algebra.