In mathematics, a Kodaira surface is a compact complex surface of Kodaira dimension 0 and odd first Betti number.
These are never algebraic, though they have non-constant meromorphic functions. They are usually divided into two subtypes: primary Kodaira surfaces with trivial canonical bundle, and secondary Kodaira surfaces which are quotients of these by finite groups of orders 2, 3, 4, or 6, and which have non-trivial canonical bundles. The secondary Kodaira surfaces have the same relation to primary ones that Enriques surfaces have to K3 surfaces, or bielliptic surfaces have to abelian surfaces.
Invariants: If the surface is the quotient of a primary Kodaira surface by a group of order k=1,2,3,4,6, then the plurigenera Pn are 1 if n is divisible by k and 0 otherwise.
Hodge diamond:
1 | |||||
---|---|---|---|---|---|
1 | 2 | ||||
1 | 2 | 1 | (Primary) | ||
2 | 1 | ||||
1 |
1 | |||||
---|---|---|---|---|---|
0 | 1 | ||||
0 | 0 | 0 | (Secondary) | ||
1 | 0 | ||||
1 |
Examples: Take a non-trivial line bundle over an elliptic curve, remove the zero section, then quotient out the fibers by Z acting as multiplication by powers of some complex number z. This gives a primary Kodaira surface.