Resumen: In this paper we introduce vector-valued Hermite expansions to approximate one-parameter operator families such as -groups and cosine functions. In both cases we estimate the rate of convergence of these Hermite expansions to the related family and compare to other already known approximations. Finally, we illustrate our results with particular examples of -groups and cosine functions and their Hermite expansions. Idioma: Inglés DOI: 10.1016/j.jmaa.2015.01.041 Año: 2015 Publicado en: JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS 426, 1 (2015), 288-311 ISSN: 0022-247X Factor impacto JCR: 1.014 (2015) Categ. JCR: MATHEMATICS rank: 56 / 311 = 0.18 (2015) - Q1 - T1 Categ. JCR: MATHEMATICS, APPLIED rank: 88 / 254 = 0.346 (2015) - Q2 - T2 Factor impacto SCIMAGO: 1.15 - Applied Mathematics (Q1) - Analysis (Q2)