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Published online by Cambridge University Press: 13 June 2025
We investigate geometric properties of invariant spatio-temporal random fields $X\colon\mathbb M^d\times \mathbb R\to \mathbb R$ defined on a compact two-point homogeneous space
$\mathbb M^d$ in any dimension
$d\ge 2$, and evolving over time. In particular, we focus on chi-squared-distributed random fields, and study the large-time behavior (as
$T\to +\infty$) of the average on [0,T] of the volume of the excursion set on the manifold, i.e. of
$\lbrace X(\cdot, t)\ge u\rbrace$ (for any
$u >0$). The Fourier components of X may have short or long memory in time, i.e. integrable or non-integrable temporal covariance functions. Our argument follows the approach developed in Marinucci et al. (2021) and allows us to extend their results for invariant spatio-temporal Gaussian fields on the two-dimensional unit sphere to the case of chi-squared distributed fields on two-point homogeneous spaces in any dimension. We find that both the asymptotic variance and limiting distribution, as
$T\to +\infty$, of the average empirical volume turn out to be non-universal, depending on the memory parameters of the field X.