On the plasticity of the unit spheres of ${\ell }_1$, ${\ell }_{\infty }$, $c$, and Hilbert spaces

Abstract

This paper demonstrates the expand-contract plasticity of the unit spheres of ${\ell }_1$, ${\ell }_{\infty }$, and $c$. Furthermore, it establishes the strong plasticity of the unit spheres of Hilbert spaces.