Sigurdur Helgason https://hdl.handle.net/1721.1/18164 2026-04-12T17:18:01Z Topologies of group algebras and a theorem of Littlewood https://hdl.handle.net/1721.1/26691 Topologies of group algebras and a theorem of Littlewood Helgason, Sigurdur An important problem in Fourier analysis is that of investigating the relationship between the "size" of a function and the "size" of its Fourier transform. The present paper can be regarded as a contribution to this problem. First published in the Transactions of the American Mathematical Society in Vol.86, 1957, published by the American Mathematical Society 1957-01-01T00:00:00Z Response to Steele Prize Award https://hdl.handle.net/1721.1/26690 Response to Steele Prize Award Helgason, Sigurdur First published in the Notices of the American Mathematical Society in Vol.35, 1988, published by the American Mathematical Society 1988-01-01T00:00:00Z Invariant differential equations on homogeneous manifolds https://hdl.handle.net/1721.1/26689 Invariant differential equations on homogeneous manifolds Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.83, 1977, published by the American Mathematical Society 1977-01-01T00:00:00Z Paley-Wiener theorems and surjectivity of invariant differential operators on symmetric spaces and Lie groups https://hdl.handle.net/1721.1/26688 Paley-Wiener theorems and surjectivity of invariant differential operators on symmetric spaces and Lie groups Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.79, 1973, published by the American Mathematical Society 1973-01-01T00:00:00Z A Fatou- type theorem for harmonic functions on symmetric spaces https://hdl.handle.net/1721.1/26687 A Fatou- type theorem for harmonic functions on symmetric spaces Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.74, 1968, published by the American Mathematical Society 1968-01-01T00:00:00Z Radon-Fourier transforms on symmetric spaces and related group representations https://hdl.handle.net/1721.1/26686 Radon-Fourier transforms on symmetric spaces and related group representations Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.71, 1965, published by the American Mathematical Society 1965-01-01T00:00:00Z A duality in integral geometry; some generalizations of the Radon transform https://hdl.handle.net/1721.1/26685 A duality in integral geometry; some generalizations of the Radon transform Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.70, 1964, published by the American Mathematical Society 1964-01-01T00:00:00Z Duality and Radon transform for symmetric spaces https://hdl.handle.net/1721.1/26684 Duality and Radon transform for symmetric spaces Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.69, 1963, published by the American Mathematical Society 1963-07-01T00:00:00Z Fundamental solutions of invariant differential operators on symmetric spaces https://hdl.handle.net/1721.1/26683 Fundamental solutions of invariant differential operators on symmetric spaces Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in 1963, published by the American Mathematical Society 1963-01-01T00:00:00Z Some results on invariant theory https://hdl.handle.net/1721.1/26682 Some results on invariant theory Helgason, Sigurdur First published in the Bulletin of the American Mathematical Society in Vol.68 1962, published by the American Mathematical Society 1962-01-01T00:00:00Z