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Comparing gaussian and Rademacher cotype for operators on the space of continous functions

Marius Junge
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Abstract

We will prove an abstract comparision principle which translates gaussian cotype in Rademacher cotype conditions and vice versa. More precisely, let $2\!<\!q\!<\!\infty$ and $T:\,C(K)\,\to\,F$ a linear, continous operator. T is of gaussian cotype q if and only if ( \summ_1^n (\frac{|| Tx_k||_F}{\sqrt{\log(k+1)}})^q )^{1/q} \, \le c || \summ_1^n \varepsilon_k x_k ||_{L_2(C(K))} , for all sequences with $(|| Tx_k ||)_1^n$ decreasing. T is of Rademacher cotype q if and only if (\summ_1^n (|| Tx_k||_F \,\sqrt{\log(k+1)})^q )^{1/q} \, \le c || \summ_1^n g_k x_k ||_{L_2(C(K))} , for all sequences with $(||Tx_k ||)_1^n$ decreasing. Our methods allows a restriction to a fixed number of vectors and complements the corresponding results of Talagrand.

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Marius Junge. 1993-02-04. Comparing gaussian and Rademacher cotype for operators on the space of continous functions. https://arxiv.org/abs/math/9302206

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