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, CalabiYau 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 MittagLeffler Institute, Fall 2021.
Enumeration and Moduli: A conference in algebraic geometry on the
occasion of Geir Ellingsrud's 70th birthday. December 68 2018, University of Oslo.
Combinatorics and Hodge theory. 1822 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 2628, 2017, University of Oslo.
Nordfjordeid Summer School: Stability conditions on triangulated categories and geometric applications.
June 1317, 2016, Sophus Lie Conference Center, Nordfjordeid, Norway.
Publications

A pencil of Enriques surfaces with nonalgebraic integral Hodge classes
(with F. Suzuki) (2019)

On deformations of quintic and septic hypersurfaces
(with S. Schreieder) (2018)

Remarks
on the positivity of the cotangent bundle of a K3 surface
(with F. Gounelas) (2018)

Curve classes on irreducible holomorphic symplectic varieties (with
G. Mongardi) (2018)

Failure of the integral Hodge conjecture for threefolds of Kodaira dimension zero (with O. Benoist). To appear in Commentarii Mathematici Helvetici (2018)

A counterexample to the birational Torelli problem for
CalabiYau 3folds (with J. V. Rennemo). Journal of the London Mathematical Society 97 (2018), 427440

Positivity of the diagonal (with B. Lehmann). Advances in Mathematics 335 (2018), 664695.

Effective cones of cycles on blowups of projective space (with
I. Coskun, J. Lesieutre). Algebra & Number Theory 109 (2016).

Nef cycles
on some hyperkahler fourfolds. To appear in the LMS volume for Fulton 80 (2016)

Curves
disjoint from a nef divisor (with J. Lesieutre). Michigan
Mathematical Journal 65 (2016), 321332.

On subvarieties with ample normal bundle. Journal of the European Mathematical Society 18 (2016), 24592468

Birational geometry of hypersurfaces in products of projective
spaces. Mathematische Zeitschrift 280 (2015), 135148

Quartic spectrahedra (with K. Ranestad, B. Sturmfels,
C. Vinzant) Math. Prog. B (2015).

Ample subvarieties and qample divisors. Advances in Mathematics 229 (2012), 28682887.

Partially ample line bundles on toric varieties. (with N. Broomhead and
A. PrendergastSmith). Glasgow Math. J. 58 (2016)

Algebraic
boundaries of Hilbert's SOS cones (with G. Blekherman, J. Hauenstein, K. Ranestad
and B. Sturmfels). Compositio Mathematica 148 (2012).

Components of the Hilbert scheme of space curves on lowdegree smooth
surfaces (with J. O. Kleppe). International Journal of Mathematics Vol. 26, (2015)

The Cox ring of a K3 surface of Picard number two. Journal of Pure
and Applied Algebra
217 (2013), 709715.
 On the Cox Ring of P^{2} Blown Up in Points on a Line. Mathematica
Scandinavica 9,
(2011), 2131.
Other
Students
Bernt Ivar Utstøl Nødland
Bjørn Skauli
Teaching
This fall I am teaching MAT4200  Commutative Algebra.