On some properties of elements in hypergroup algebras

Document Type : Research Paper

Author

Department of Mathematics, University of Semnan, P. O. Box 35195-363, Semnan, Iran

Abstract

Let $H$ be a hypergroup with left Haar measure and let $L^1(H)$ be the complex Lebesgue space associated with it. Let $L^\infty(H)$ be the set of all locally measurable functions that are bounded except on a locally null set, modulo functions that are zero locally a.e. Let $\mu\in M(H)$. We want to find out when $\mu F\in L^\infty(H)^*$ implies that $F\in L^1(H)$. Some necessary and sufficient conditions is found for a measure $\mu$ for which if $\mu F\in L^1(H)$ for every $F\in L^\infty(H)^*$, then $F\in L^1(H)$.

Keywords

[1] M. Amini and C.H. Chu, Harmonic functions on hypergroups, J. Funct. Anal. 261 (2011), 1835–1864.
[2] M. Amini and A.R. Medghalchi, Amenability of compact hypergroup algebras, Math. Nach. 287 (2014), 1609–1617.
[3] M. Amini, H. Nikpey and S.M. Tabatabaie, Crossed product of C*-algebras by hypergroups, Math. Nach. 292 (2019), 1897–1910.
[4] J.F. Berglund, H.D. Junghenn and P. Milnes, Analysis on Semigroups: Function Spaces, Compatifications, Representations, Wiley-Interscience and Canadian Mathematics Series of Monographs and Texts, 1988.
[5] W.R. Bloom and H. Heyer, Harmonic analysis of probability measures on hypergroups, vol. 20, de Gruyter Studies in Mathematics, Walter de Gruyter & Co., Berlin, 1995.
[6] H.G. Dales, Banach algebra and automatic continuity, London Math. Soc. Monogr. Ser. Clarendon Press, 2000.
[7] A. Ghaffari, T. Haddadi, S. Javadi and M. Sheybani, On the structure of hypergroups with respect to the induced topology, Rocky Mount. J. Math. 52 (2022), 519–533.
[8] A. Ghaffari and M.B. Sahabi, Characterizations of amenable hypergroups, Wavelets Linear Algebras 4 (2017), 1–9.
[9] R.A. Kamyabi-Gol, Topological center of dual Banach algebras associated to hypergroups and invariant complemented subspaces, Ph.D. Thesis, University of Alberta, 1997.
[10] W. Rudin, Functional analysis, McGraw Hill, New York, 1991.
[11] N. Tahmasebi, Fixed point properties, invariant means and invariant projections related to hypergroups, J. Math. Anal. Appl. 437 (2016), 526–544.
[12] B. Willson, A fixed point theorem and the existence of a Haar measure for hypergroups satisfying conditions related to amenability, Canad. Math. Bull. 58 (2015), 415–422.
[13] B. Willson, Configurations and invariant nets for amenable hypergroups and related algebras, Trans. Amer. Math. Soc. 366 (2014), 5087–5112.
Volume 13, Issue 2
July 2022
Pages 3307-3312
  • Receive Date: 04 April 2021
  • Revise Date: 17 June 2021
  • Accept Date: 19 October 2021