Abstract
Let G be a compact abelian group with dual Γ. A function φ on Γ is said to be a multiplier from Lp(G) to lq(Γ) (φ∈(Lp(G),lq(Γ))) if φfˆ∈lq(Γ) for every f∈Lp(G).
Suppose that G is a compact abelian group not totally disconnected and 1≤p1<p2≤2, 1≤q<p′1. Then (Lp1(G),lq(Γ))⊂(Lp2(G),lq(Γ)).
Using the Weil's map the author reduces the problem to the case of G=T. The result is then a consequence of the theory of trigonometric series with decreasing coefficients.
For every compact abelian group G, 1<p<2, q<p′, one has lp′q/(p′−q)(Γ)⊆(Lp(G),lq(Γ)).
For G=T, 1<p<2, q<p′, φ∈(Lp(T),lq(Z)) non-negative, decreasing and even, he proves that φ∈lr(Z) for all r>p′q/(p′−q). The author also obtains a sufficient condition on a sequence φ to be in (Lp(T),lq(Z)) (Theorem 8 p. 157). As a consequence he shows the existence of φ∈(Lp(T),lq(Z)) non-negative, decreasing and even but not in lp′q/(p′−q)(Z).
Suppose that G is a compact abelian group not totally disconnected and 1≤p1<p2≤2, 1≤q<p′1. Then (Lp1(G),lq(Γ))⊂(Lp2(G),lq(Γ)).
Using the Weil's map the author reduces the problem to the case of G=T. The result is then a consequence of the theory of trigonometric series with decreasing coefficients.
For every compact abelian group G, 1<p<2, q<p′, one has lp′q/(p′−q)(Γ)⊆(Lp(G),lq(Γ)).
For G=T, 1<p<2, q<p′, φ∈(Lp(T),lq(Z)) non-negative, decreasing and even, he proves that φ∈lr(Z) for all r>p′q/(p′−q). The author also obtains a sufficient condition on a sequence φ to be in (Lp(T),lq(Z)) (Theorem 8 p. 157). As a consequence he shows the existence of φ∈(Lp(T),lq(Z)) non-negative, decreasing and even but not in lp′q/(p′−q)(Z).
Original language | English |
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Pages (from-to) | 151-158 |
Number of pages | 8 |
Journal | Indian Journal of Math |
Volume | 45 |
Issue number | 2 |
Publication status | Published - 2003 |