Divisors

• Degree
• Divisor corresponding to a rational function
• Canonical divisor
• Different divisor
• Properties: Effective, positive, principal, special
• Riemann-Roch space ${\cal L}(D)$ of a divisor D, given by a k-basis of algebraic functions
• Index of speciality
• Estimate of the number of divisor classes of degree zero (global fields)
• Divisor reduction