3 papers
math.AG2000
Logarithmic orbifold Euler numbers of surfaces with applications
Adrian Langer
We introduce orbifold Euler numbers for normal surfaces with Q-divisors. These numbers behave multiplicatively under finite maps and in the log canonical case we prove that they sa…
math.AG1998
Pluricanonical systems on surfaces with small K^2
Adrian Langer
We prove that the bicanonical system on a surface of general type with K^2=4 has no base components and describe clusters contracted by 4K_X for a numerical Godeaux surface and 3K_…
math.AG1998
A note on k-jet ampleness on surfaces
Adrian Langer
We prove Reider type criterions for k-jet spannedness and k-jet ampleness of adjoint bundles for surfaces with at most rational singularities. Moreover, we prove that on smooth sur…