2018/12/06 by Wang, B.
#14J33 #Algebraic Geometry (math.AG) #FOS: Mathematics
paper · doi:10.48550/arxiv.1812.02526
Let X0 be a generic quintic threefold in projective space \mathbf P4 over the complex numbers. For a fixed natural number d, let Rd(X0) be the open sub-scheme of the Hilbert scheme, parameterizing irreducible rational curves of degree d on X0. In this paper, we show that (1) Rd(X0) is smooth and of expected dimension, \par (2) Combining the Calabi-Yau condition on X0, we further show that it consists of immersed rational curves. (3) Parts (1) and (2) imply a statement of Clemens' conjecture: if C0∈ Rd(X0) and c0:\mathbf P1→ C0 is the normalization, the \par\hspace1cc normal sheaf is isomorphic to the vector bundle Nc0/X0≃ \mathcal O\mathbf P1(-1)⊕ \mathcal O\mathbf P1(-1).