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On a time deformation reducing nonstationary stochastic processes to local stationarity

Published online by Cambridge University Press:  14 July 2016

Marc G. Genton*
Affiliation:
North Carolina State University
Olivier Perrin*
Affiliation:
Université Toulouse 1
*
Postal address: Department of Statistics, North Carolina State University, Box 8203, Raleigh, NC 27695-8203, USA. Email address: [email protected]
∗∗ Postal address: GREMAQ, Université des Sciences Sociales, 21 Allée de Brienne, 31000 Toulouse, France. Email address: [email protected]

Abstract

A stochastic process is locally stationary if its covariance function can be expressed as the product of a positive function multiplied by a stationary covariance. In this paper, we characterize nonstationary stochastic processes that can be reduced to local stationarity via a bijective deformation of the time index, and we give the form of this deformation under smoothness assumptions. This is an extension of the notion of stationary reducibility. We present several examples of nonstationary covariances that can be reduced to local stationarity. We also investigate the particular situation of exponentially convex reducibility, which can always be achieved for a certain class of separable nonstationary covariances.

Type
Research Papers
Copyright
Copyright © Applied Probability Trust 2004 

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