Resumen
We propose a new nonparametric test to test for symmetry and separability of space-time covariance functions. Unlike the existing nonparametric tests, our test has the attractive convenience of being free of choosing any user-chosen number or smoothing parameter. The asymptotic null distributions of the test statistics are free of nuisance parameters and the critical values have been tabulated in the literature. From a practical point of view, our test is easy to implement and can be readily used by the practitioner. A Monte-Carlo experiment and real data analysis illustrate the finite sample performance of the new test.

Resumen
In this article we consider the numerical approximation to the time-dependent viscoelasticity equations with an Oldroyd B constitutive equation. The approximation is stabilized by using a streamline upwind Petrov--Galerkin (SUPG) approximation for the constitutive equation. We analyze both the semidiscrete and fully discrete numerical approximations. For both discretizations we prove the existence of, and derive a priori error estimates for, the numerical approximations.