Jan Arthur Christophersen

• Christophersen, Jan Arthur & Kleppe, Jan Oddvar (2019). Comparison theorems for deformation functors via invariant theory. Collectanea Mathematica. ISSN 0010-0757. 70(1), p. 1–32. doi: 10.1007/s13348-018-0232-z. Full text in Research Archive Show summary

  We compare deformations of algebras to deformations of schemes in the setting of invariant theory. Our results generalize comparison theorems of Schlessinger and the second author for projective schemes. We consider deformations (abstract and embedded) of a scheme X which is a good quotient of a quasi-affine scheme X0 by a linearly reductive group G and compare them to invariant deformations of an affine G-scheme containing X0 as an open invariant subset. The main theorems give conditions for when the comparison morphisms are smooth or isomorphisms.

• Christophersen, Jan Arthur & Ilten, Nathan Owen (2017). Vanishing cotangent cohomology for Plücker algebras. Communications in Algebra. ISSN 0092-7872. 45(9), p. 3929–3947. doi: 10.1080/00927872.2016.1249373. Full text in Research Archive Show summary

  We use representation theory and Bott’s theorem to show vanishing of higher cotangent cohomology modules for the homogeneous coordinate ring of Grassmannians in the Plücker embedding. As a by-product, we answer a question of Wahl about the cohomology of the square of the ideal sheaf for the case of Plücker relations. We obtain slightly weaker vanishing results for the cotangent cohomology of the coordinate rings of isotropic Grassmannians. This is an Accepted Manuscript of an article published by Taylor & Francis in Communications in Algebra on 31 Jan 2017, available online: http://www.tandfonline.com/10.1080/00927872.2016.1249373

• Christophersen, Jan Arthur & Ilten, Nathan Owen (2016). Hilbert schemes and toric degenerations for low degree Fano threefolds. Journal für die Reine und Angewandte Mathematik. ISSN 0075-4102. 2016(717), p. 77–100. doi: 10.1515/crelle-2014-0011. Full text in Research Archive
• Christophersen, Jan Arthur & Ilten, Nathan Owen (2014). Degenerations to unobstructed Fano Stanley-Reisner schemes. Mathematische Zeitschrift. ISSN 0025-5874. 278(1-2), p. 131–148. doi: 10.1007/s00209-014-1309-3. Full text in Research Archive
• Christophersen, Jan Arthur (2011). Deformations of equivelar Stanley-Reisner abelian surfaces. Advances in Mathematics. ISSN 0001-8708. 227(2), p. 801–829. doi: 10.1016/j.aim.2011.02.014. Full text in Research Archive
• Altmann, Klaus & Christophersen, Jan Arthur (2010). Deforming Stanley-Reisner schemes. Mathematische Annalen. ISSN 0025-5831. 348(3), p. 513–537. doi: 10.1007/s00208-010-0490-x. Full text in Research Archive
• Altmann, Klaus & Christophersen, Jan Arthur (2004). Cotangent cohomology of Stanley-Reisner rings. Manuscripta mathematica. ISSN 0025-2611. 115, p. 361–378. Full text in Research Archive
• Christophersen, Jan Arthur & Gustavsen, Trond Stølen (2001). On infinitesimal deformations and obstructions for rational surface singularities. Journal of Algebraic Geometry. ISSN 1056-3911. 10(1), p. 179–198. Full text in Research Archive
• Behnke, Kurt & Christophersen, Jan Arthur (1994). M-resolutions and deformations of quotient singularities. American Journal of Mathematics. ISSN 0002-9327. 116, p. 881–903. Full text in Research Archive
• Behnke, Kurt & Christophersen, Jan Arthur (1993). Hypersurface sections and obstructions (minimal elliptic singularities). Transactions of the American Mathematical Society. ISSN 0002-9947. 335, p. 175–193. Full text in Research Archive
• Christophersen, Jan Arthur (1991). On the components and discriminant of the versal base space of cyclic quotient singularities. In Mond, D. & Montaldi, J. (Ed.), Singularity Theory and its Applications, Warwick 1989 Part 1. Springer. p. 81–92. Full text in Research Archive
• Behnke, Kurt & Christophersen, Jan Arthur (1991). Hypersurface sections and obstructions (rational surface singularities). Compositio Mathematica. ISSN 0010-437X. 77, p. 233–268. Full text in Research Archive
• Christophersen, Jan Arthur (1987). Monomial curves and obstructions on cyclic quotient singularities. In Greuel, G.-M. & Trautman, G. (Ed.), Singularities, Representation of Algebras, and Vector Bundles, Proc., Lambrecht 1985. Springer. p. 117–133. Full text in Research Archive

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• Christophersen, Jan Arthur & Ranestad, Kristian (2018). Geometry of Moduli. Abelsymposium 2017. Springer. ISBN 9783319948805. 326 p. Full text in Research Archive

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• Christophersen, Jan Arthur (2018). Cotangent cohomology for Pflücker algebras. Full text in Research Archive
• Christophersen, Jan Arthur (2016). Derivations of artinian algebras and rigidity of curve singularities. Full text in Research Archive
• Christophersen, Jan Arthur (2014). Local cohomology and higher cotangent cohomology for cones over Grassmannians. FU Berlin. Full text in Research Archive
• Christophersen, Jan Arthur (2014). Local cohomology of the Kähler differentials of invariant rings. Full text in Research Archive
• Christophersen, Jan Arthur (2013). Comparison theorems for deformation functors. Full text in Research Archive
• Christophersen, Jan Arthur (2013). Simplicial complexes and projective varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2012). Triangulated topological manifolds and special algebraic varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2012). Comparison theorems for deformation functors. Full text in Research Archive
• Christophersen, Jan Arthur (2012). Simplicial complexes and projective varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2011). On the Hilbert scheme containing Fano threefolds of low degree. Full text in Research Archive
• Christophersen, Jan Arthur (2011). Associahedra, deltahedra and Mukai varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2011). The associahedron, deltahedra and Stanley-Reisner Fano varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2011). Triangulated topological manifolds and special algebraic varieties. Full text in Research Archive
• Christophersen, Jan Arthur (2010). Deformations of Stanley-Reisner abelian surfaces. Full text in Research Archive
• Christophersen, Jan Arthur (2010). Deformations of monomial ideals. Full text in Research Archive
• Christophersen, Jan Arthur (2010). Deformation Theory. Full text in Research Archive Show summary

  Fire forelesninger, innføring i deformasjonsteori for unge forskere (dr og post dr).

• Christophersen, Jan Arthur (2010). Deformasjoner av monomiale idealer. Full text in Research Archive
• Christophersen, Jan Arthur (2009). Introductory course in Deformation Theory. Full text in Research Archive
• Christophersen, Jan Arthur (2009). Ekvivelære trianguleringer av torusen og abelske flater. Full text in Research Archive
• Christophersen, Jan Arthur (2009). Milnor fibers of cyclic quotient singularities. Full text in Research Archive
• Christophersen, Jan Arthur (2009). Equivelar triangulations of tori and abelian surfaces. Full text in Research Archive
• Christophersen, Jan Arthur (2008). Deformations of Stanley-Reisner surfaces. Full text in Research Archive
• Christophersen, Jan Arthur (2008). Triangulations of the Torus and Abelian Surfaces. Full text in Research Archive
• Christophersen, Jan Arthur (2008). The minimal triangulation of the torus and abelian surfaces. Full text in Research Archive
• Christophersen, Jan Arthur (2007). Deformation theory in algebraic geometry. Full text in Research Archive
• Christophersen, Jan Arthur (2007). Deformations of a Stanley-Reisner abelian surface. Full text in Research Archive
• Christophersen, Jan Arthur (2006). Deformations of a Stanley-Reisner abelian surface and a Calabi-Yau 3-fold with Euler number 6. Full text in Research Archive
• Christophersen, Jan Arthur (2006). Deformations of a degenerate abelian surface in P6. Full text in Research Archive
• Christophersen, Jan Arthur (2006). Deformation theory, cotangent complexes and Massey products. Full text in Research Archive
• Christophersen, Jan Arthur (2006). Deformations of a degenerate abelian surface in P^6. Full text in Research Archive
• Christophersen, Jan Arthur (2000). Deforming Stanley-Reisner rings. Full text in Research Archive
• Christophersen, Jan Arthur (2000). Symmetri og materiens struktur - fra antikken til kvantefysikken. Full text in Research Archive
• Christophersen, Jan Arthur (2010). Forelesningsnotater MAT2500. Ingen. Full text in Research Archive
• Christophersen, Jan Arthur & Gustavsen, Trond Stølen (1996). ON INFINITESIMAL DEFORMATIONS AND OBSTRUCTIONS FOR RATIONAL SURFACE SINGULARITIES. Universitetet i Oslo. Full text in Research Archive
• Behnke, Kurt & Christophersen, Jan Arthur (1991). M-resolutions and Deformations of Quotient Singularities. Universitetet i Oslo. Full text in Research Archive
• Christophersen, Jan Arthur (1990). Obstructions for rational singularities and deformations of cyclic quotients. Universitetet i Oslo. Full text in Research Archive
• Christophersen, Jan Arthur (1986). MONOMIAL CURVES AND OBSTRUCTIONS ON CYCLIC QUOTIENT SINGULARITIES. Universitetet i Oslo. Full text in Research Archive
• Christophersen, Jan Arthur (1985). THE MILNOR NUMBER FOR CURVES ON TORIC SURFACES. Universitetet i Oslo. Full text in Research Archive
• Christophersen, Jan Arthur (1985). DERIVATIONS OF SIMPLICIAL CONIC ALGEBRAS. APPLICATIONS TO DEFORMATIONS OF CURVES ON TORIC SURFACES. Universitetet i Oslo. Full text in Research Archive

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