Let f(𝜃) be integrable on (0,π)
and define
where Pn(α,β)(x) is the Jacobi polynomial of degree n, order (α,β) and
Then if α,β,γ,δ ≧−1∕2 we have
for 1 < p < ∞,−1 < σ < p − 1 whenever the right hand side is finite.
From this result any norm inequality for Fourier coefficients can be
transplanted to give a corresponding norm inequality for Fourier-Jacobi
coefficients.
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