Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasi-arithmetic means of covariance functions with potential
  applications to space-time data   The theory of quasi-arithmetic means is a powerful tool in the study of
covariance functions across space-time. In the present study we use
quasi-arithmetic functionals to make inferences about the permissibility of
averages of functions that are not, in general, permissible covariance
functions. This is the case, e.g., of the geometric and harmonic averages, for
which we obtain permissibility criteria. Also, some important inequalities
involving covariance functions and preference relations as well as algebraic
properties can be derived by means of the proposed approach. In particular, we
show that quasi-arithmetic covariances allow for ordering and preference
relations, for a Jensen-type inequality and for a minimal and maximal element
of their class. The general results shown in this paper are then applied to
study of spatial and spatiotemporal random fields. In particular, we discuss
the representation and smoothness properties of a weakly stationary random
field with a quasi-arithmetic covariance function. Also, we show that the
generator of the quasi-arithmetic means can be used as a link function in order
to build a space-time nonseparable structure starting from the spatial and
temporal margins, a procedure that is technically sound for those working with
copulas. Several examples of new families of stationary covariances obtainable
with this procedure are shown. Finally, we use quasi-arithmetic functionals to
generalise existing results concerning the construction of nonstationary
spatial covariances and discuss the applicability and limits of this
generalisation.

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The categories of this paper are: astro-ph
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The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: cs
29
The categories of this paper are: funct-an
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The categories of this paper are: math-ph