# Number of times a Gaussian process crosses zero in an interval

Using a probabilistic method for number theoretic purposes, I have encountered the following question (it may be very standard):

Let $X_t$ be a Gaussian process $(t>0)$ such that $X_0=0$. What is the expected number of times for the process to cross zero in the interval $[0,c)$ as a function of $c$?

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