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Norm inequalities involving geometric means

Functional Analysis 2024-01-02 v1

Abstract

Let AiA_i and BiB_i be positive definite matrices for every i=1,,m.i=1,\cdots,m. Let Z=[Zij]Z=[Z_{ij}] be the block matrix, where Zij=Bi12(k=1mAk)Bj12Z_{ij}=B_i^{^\frac{1}{_2}}\left(\displaystyle\sum_{k=1}^mA_k\right)B_j^{^\frac{1}{_2}} for every i,j= 1,,m i,j=~1,\cdots,m. It is shown that i=1m(AisBis)rZsr2((i=1mAi)srp4(i=1mBi)srp2(i=1mAi)srp4)1p,\left|\left|\left|\sum_{i=1}^m\left(A_i^{s}\sharp B_i^{s}\right)^r\right|\right|\right|\leq\left|\left|\left| Z^{^\frac{sr}{_2}} \right|\right|\right| \leq \left|\left|\left|\left(\left(\sum_{i=1}^mA_i\right)^\frac{srp}{_4}\left(\sum_{i=1}^mB_i\right)^\frac{srp}{_2}\left(\sum_{i=1}^mA_i\right)^\frac{srp}{_4}\right)^{\frac{1}{_p}}\right|\right|\right|, for all s2s\geq2, for all p>0p>0 and r1r\geq1 such that rp1rp\geq1 and for all unitarily invariant norms. This result generalizes the results in \cite{ONIR} and gives an affirmative answer to a conjecture in \cite{OACRT} for all s2s\geq2 and for all p>0p>0 and r1r\geq1 such that rp1rp\geq1 and t=12t=\frac{1}{2}. This result also leads directly to Dinh, Ahsani, and Tam's conjecture in \cite{GAI} and proves Audenaert's result in \cite{ANIFP}.

Keywords

Cite

@article{arxiv.2401.00337,
  title  = {Norm inequalities involving geometric means},
  author = {Shaima'a Freewan and Mostafa Hayajneh},
  journal= {arXiv preprint arXiv:2401.00337},
  year   = {2024}
}
R2 v1 2026-06-28T14:05:20.287Z