GALERKIN METHOD (NUMERICAL MATHEMATICS); DIFFUSION EQUATIONS + HEAT EQUATIONS (MATHEMATICAL ANALYSIS); Affine-parametric operator equations; Tensorized Chebyshev polynomial chaos approximation; SIGNALVERARBEITUNG (NACHRICHTENTECHNIK); Compressive sensing; LINEARE OPERATOREN UND OPERATORENGLEICHUNGEN (FUNKTIONALANALYSIS); LINEAR OPERATORS AND OPERATOR EQUATIONS (FUNCTIONAL ANALYSIS); Parametric diffusion equation; DIFFUSIONSGLEICHUNGEN + WÄRMELEITUNGSGLEICHUNGEN (ANALYSIS); s-term approximation; GALERKIN-VERFAHREN (NUMERISCHE MATHEMATIK); High-dimensional approximation; SIGNAL PROCESSING (TELECOMMUNICATIONS)