Periods of linear algebraic cycles

In this article we use a theorem of Carlson and Griffiths and compute periods of linear algebraic cycles $\mathbb{P}^{\frac{n}{2}}$ inside the Fermat variety of even dimension $n$ and degree $d$. As an application, for examples of $n$ and $d$, we prove that the locus of hypersurfaces containing two linear cycles whose intersection is of low dimension, is a reduced component of the Hodge locus in the underlying parameter space. We also check the same statement for hypersurfaces containing a complete intersection algebraic cycle. Our result confirms the Hodge conjecture for Hodge cycles obtained by the monodromy of the homology class of such algebraic cycles. This is known as the variational Hodge conjecture.

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Received 5 March 2019

Received revised 11 March 2019

Accepted 28 March 2019

Published 5 November 2019