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My question is regarding mean widths. For a set $\mathcal{T}$ define the mean width

\begin{align*} \omega(T)=\mathbb{E}_{\mathbf{g}\sim\mathcal{N}(0,\mathbf{I})}\bigg[\underset{\mathbf{u}\in\mathcal{T}}{\sup}\text{ } \mathbf{u}^T\mathbf{g}\bigg]. \end{align*}

My question is what is the mean width of two ellipsoid i.e. mean width of the following set \begin{align*} \mathcal{T}=\mathcal{T}_1\cap\mathcal{T}_2 \end{align*} where \begin{align*} \mathcal{T}_1=\{\mathbf{A}_1\mathbf{u}| \|\mathbf{u}\|_{\ell_2}\le 1\}\quad\text{and}\quad \mathcal{T}_2=\{\mathbf{A}_2\mathbf{u}+\mathbf{c}|\|\mathbf{u}\|_{\ell_2}\le 1\} \end{align*} I'm interested in a good upperbound on $\omega(\mathcal{T})$.

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  • $\begingroup$ Trivial upper-bound is $\omega(T) \le \min(\omega(T_1),\omega(T_2))$. $\endgroup$
    – dohmatob
    Commented Oct 7, 2022 at 17:35

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