English

$H^\infty$ functional calculus and maximal inequalities for semigroups of contractions on vector-valued $L_p$-spaces

Functional Analysis 2014-05-27 v2 Classical Analysis and ODEs

Abstract

Let {Tt}t>0\{T_t\}_{t>0} be a strongly continuous semigroup of positive contractions on Lp(X,μ)L_p(X,\mu) with 1<p<1<p<\infty. Let EE be a UMD Banach lattice of measurable functions on another measure space (Ω,ν)(\Omega,\nu). For fLp(X;E)f\in L_p(X; E) define M(f)(x,ω)=supt>01t0tTs(f(,ω))(x)ds,(x,ω)X×Ω.\mathcal M(f)(x, \omega)=\sup_{t>0}\frac1t\Big|\int_0^tT_s(f(\cdot,\omega))(x)ds\Big|,\quad (x,\omega)\in X\times\Omega. Then the following maximal ergodic inequality holds M(f)Lp(X;E)fLp(X;E),fLp(X;E).\big\|\mathcal M(f)\big\|_{L_p(X; E)}\lesssim \big\|f\big\|_{L_p(X; E)},\quad f\in L_p(X; E). If the semigroup {Tt}t>0\{T_t\}_{t>0} is additionally assumed to be analytic, then {Tt}t>0\{T_t\}_{t>0} extends to an analytic semigroup on Lp(X;E)L_p(X; E) and M(f)\mathcal M(f) in the above inequality can be replaced by the following sectorial maximal function Tθ(f)(x,ω)=suparg(z)<θTz(f(,ω))(x)\mathcal T_\theta(f)(x, \omega)=\sup_{|{\rm arg}(z)|<\theta}\big|T_z(f(\cdot,\omega))(x)\big| for some θ>0\theta>0. Under the latter analyticity assumption and if EE is a complex interpolation space between a Hilbert space and a UMD Banach space, then {Tt}t>0\{T_t\}_{t>0} extends to an analytic semigroup on Lp(X;E)L_p(X; E) and its negative generator has a bounded H(Σσ)H^\infty(\Sigma_\sigma) calculus for some σ<π/2\sigma<\pi/2.

Keywords

Cite

@article{arxiv.1402.2344,
  title  = {$H^\infty$ functional calculus and maximal inequalities for semigroups of contractions on vector-valued $L_p$-spaces},
  author = {Quanhua Xu},
  journal= {arXiv preprint arXiv:1402.2344},
  year   = {2014}
}