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Abstract. Sufficient ultraspherical multiplier criteria are refined in such a way that they are comparable with necessary multiplier conditions. Also new necessary conditions for Jacobi multipliers are deduced which, in particular, imply known Cohen type inequalities. Muckenhoupt's transplantation theorem is used in an essential way.
AMS Subject Classification
(1991): 33C45, 42A45, 42C10
Keyword(s):
Ultraspherical polynomials,
multipliers,
necessary conditions,
sufficient conditions,
Cohen type inequalities,
fractional differences
Received September 26, 1994. (Registered under 5633/2009.)
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