Divisors

Definitions

  • What is a prime divisor?
  • What is a Weil divisor?
  • What is a Cartier divisor?
  • What is an effective divisor?
  • What is a reduced divisor?
  • What is a principal divisor?
  • What is the divisor class group?
  • What does it mean for divisors to be linearly equivalent?
  • What does it mean for two divisors to be numerically equivalent?
  • What is the Picard group?
  • What is the pullback of a divisor?
  • What is the divisor associated to a section of a bundle?
  • For \(D\) a prime divisor and \(p\in \mathop{\mathrm{supp}}D\), what is the multiplicity of \(p\) in \(D\)?
  • What is a SNC divisor?
  • For \(D\) a divisor, what is \({\mathcal{O}}_X(D)\)?
  • What is a polarization?
    • What is an ample divisor?
    • What is a very ample divisor?
  • What is a nef divisor?
  • What is a big divisor?
  • What is a variety of general type?
  • What is the ramification divisor of a surjective morphism \(f:X\to Y\) of smooth projective curves?
    • What is the ramification index?
    • What is the branch locus?
  • What is a linear system?
    • What is a complete linear system?
      • What is the complete linear system associated to a section?
    • What is the base locus of a linear system?
    • What does it mean for a linear system to be base point free?
  • What is the Riemann-Roch space?

Problems

  • Show that the hyperplane sections of a projective variety \(X\) form a base point free linear system of effective divisors on \(X\).
    • Show that if \(X\) is normal, then a generic element of this system is a smooth and reduced divisor.