Structure

category of schemes

Notation SchR\Sch_R Objects schemes over R≠0R \neq 0, i.e. locally ringed spaces over RR that have an open covering by affine schemes over RR Morphisms morphisms of locally ringed spaces over RR Related LRSR\LRS_R, Top\Top, CAlg(R)\CAlg(R), [CRing,Set][\CRing, \Set] External nLab link
Here, RR is a fixed non-trivial commutative ring. The general properties of this category will not depend on the choice of RR. For R=ZR = \IZ we obtain the category Sch\Sch of schemes.

Satisfied properties

Assigned properties

Deduced properties

Unsatisfied properties

Assigned properties

Deduced properties*

*This also uses the deduced satisfied properties.

Unknown properties

There are 9 properties for which the database has no information on whether they are satisfied. Please help us fill in the gaps by contributing to this project.

Special objects

  • terminal object: Spec⁡(R)\Spec(R)
  • initial object: empty scheme
  • products: [finite case] The idea is to use Spec⁡(A)×Spec⁡(B)=Spec⁡(A⊗RB)\Spec(A) \times \Spec(B) = \Spec(A \otimes_R B) and then to glue affine pieces together. See EGA I, Chap. I, Thm. 3.2.1.
  • coproducts: disjoint union with the product sheaf

Special morphisms

  • isomorphisms: pairs (f,f♯)(f,f^{\sharp}) consisting of a homeomorphism ff and an isomorphism of sheaves f♯f^{\sharp} of RR-algebras
  • monomorphisms:
  • epimorphisms:
  • regular monomorphisms:
  • regular epimorphisms:

Comments

  • Monomorphisms are discussed at MO/56591. At least the case of morphisms of locally finite type is understood.
  • Regular monomorphisms are discussed at MO/66279.
  • Epimorphisms are discussed at MO/56564. Probably they cannot be classified.