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Sojourn functionals of time-dependent $\chi^2$-random fields on two-point homogeneous spaces

Published online by Cambridge University Press:  13 June 2025

Alessia Caponera*
Affiliation:
LUISS Guido Carli
Maurizia Rossi*
Affiliation:
Università di Milano-Bicocca
María Dolores Ruiz Medina*
Affiliation:
Universidad de Granada
*
*Email address: acaponera@luiss.it
**Email address: maurizia.rossi@unimib.it
***Email address: mruiz@ugr.es

Abstract

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.

Type
Original Article
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Applied Probability Trust

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