Informationen zum Steilkurs Schemata/Fast track course schemes
Wintersemester 2022

Aktuelles

• The room is equipped with video and the lecture will be streamed via the BBB-room Steilkurs Schemes (It seems that the link only works once the room has actually been started.)

Material

Dates

Lecture

Tuesday 08-10, SR 404, Ernst-Zermelo-Str. 1

Excercise and discussion classes

Thursday 10-12; Friday 10-12

Material covered and excercises

• 24.10.22: Let X=C as topological space, O the sheaf of holomorphic functions, O^* the sheaf of nowhere vanishing holomorphic functions, exp:O\to O^* the exponential map. Show that exp is surjective as a morphism of sheaves, but not as a morphism of presheaves

  Hartshorne II. 1.3, 1.8, 1.17, 1.19

• 8.11.22: Schemes and morphisms of schemes, first half of Hartshorne II.2
  • Let $(X,\Oh_X)$ be a locally ringes space such that every point has a neighbourhood $U$ such that $(U,\Oh_X|_U)$ is isomorphic to $(U',\Ch)$ where $U\subset\R^n$ is open and $\Ch$ the sheaf of differentiable functions on $U$. Show that $X$ has a unique structure of a differentiable manifold such that $\Oh_X$ is the sheaf of differentiable functions on $U$.
  • Work out $\Spec A$ and its topology in the following cases: $\Z$, $k$ field, $k[X]$ and $k[X,Y]$ for $k$ algebraically closed field, $\Z_p$ ($p$-adic numbers), $\Z/p^n$ for $p$ prime, $k[[X]]$ for $k$ a field.
  • $\Spec(A\oplus B)=\Spec A\cup \Spec B$
  • Hartshorne II.2.1, 2.3, 2.5, 2.7, 2.19
• 15.11.22: Varietäten, projektiver Raum, erste Eigenschaften

  Hartshorne II 2.10, 2.11, 3.5, 3.6, 3.8

• 22.11.22:Immersions, T-valued points, fibre product Ha II.3
  • Hartshorne II 3.9, 3.10, 3.13
    
  • Let f:X\to Y be an $S$-morphism. We define the graph G_f as
    G_f(T)={ (x,f(x)) in X(T) x_{S(T)} Y(T) }
    Show that the natural map G_f\to X is an isomorphism, in particular G_f is a scheme.
    Let g:Y\to Z be another S-morphism. Show that
    G_{fg}=G_f x_{Y}G_g
• 29.11.22 Separated and proper, valuation rings Ha II.4
  • Let A be a one-dimensional local noetherian integral domain with maximal ideal m and residue field k. The following are equivalent:
    1. A is a discrete valuation ring
    2. A is integrally closed
    3. m is a principal ideal
    4. dim_k(m/m^2)=1
    5. Every non-zero ideal is a power of m
    6. There is x in A such that every non-zero ideal is of the form (x^v) with v\geq 0.
  • Ha II 4.1, 4.2, 4.3, 4.8
• 06.12.22 Valuative criteria Ha II.4
  • Let k algebraically closed, C=V(XY)\subset\A^2_k, R=k[[t]]. Determine all morphisms of k-schemes \Spec k[[t]]\to C. What are the image of the special/generic point in each case?
  • Ha II 4.4, 4.6, 3.17
• 13.12.22 Modulgarben Ha II.5
  Ha II 5.1, 5.6, 5.7 Tipp: Nakyamas Lemma