Characterization of Banach spaces $Y$ satisfying that the pair $ (\ell_\infty^4,Y )$ has the Bishop-Phelps-Bollobás property for operators

Abstract: We study the Bishop-Phelps-Bollob\'as property for operators from $\ell_\infty ⁴ $ to a Banach space. For this reason we introduce an appropiate geometric property, namely the AHSp-$\ell_\infty ^4$. We prove that spaces $Y$satisfying AHSp-$\ell_\infty ^4$ are precisely those spaces $Y$ such that $(\ell_\infty^4,Y)$ has the Bishop-Phelps-Bollob\'as property. We also provide classes of Banach spaces satisfying this condition. For instance, finite-dimensional spaces, uniformly convex spaces, $C_0(L)$ and $L_1 (\mu)$ satisfy AHSp-$\ell_\infty ⁴ $.