## Abstract

Let f ∈ L^{p}(R^{n}) and R > 0. The transform is considered that integrates the function f over (almost) all spheres of radius R in R^{n}. This operator is known to be non-injective (as one can see by taking Fourier transform). However, the counterexamples that can be easily constructed using Bessel functions of the 1st kind, only belong to L^{p} if p > 2n/(n − 1). It has been shown previously by S. Thangavelu that for p not exceeding the critical number 2n/(n − 1), the transform is indeed injective. A support theorem that strengthens this injectivity result can be deduced from the results of [12], [13]. Namely, if K is a convex bounded domain in R^{n}, the index p is not above 2n/(n − 1), and (almost) all the integrals of f over spheres of radius R not intersecting K are equal to zero, then f is supported in the closure of the domain K. In fact, convexity in this case is too strong a condition, and the result holds for any what we call R-convex domain. We provide a simplified and self-contained proof of this statement.

Original language | English |
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Pages (from-to) | 1-16 |

Number of pages | 16 |

Journal | Memoirs on Differential Equations and Mathematical Physics |

Volume | 52 |

State | Published - 2011 |

### Bibliographical note

Funding Information:The work of the first author was performed when he was visiting Texas A&M University and was partially supported by the ISF (Israel Science Foundation) grant 688/08. The second author was partially supported by the NSF grants DMS 0604778 and 0908208 and by the IAMCS. The authors express their gratitude to ISF, NSF, Texas A&M University, and IAMCS for the support. We are also grateful to the reviewer of the first version of the text for pointing to us the reference to [13] and to Y. Lyubarskii for useful comments and references.

Publisher Copyright:

© 2011, Razmadze Mathematical Institute. All rights reserved.

## Keywords

- Radon transform
- Spherical mean
- Support