rademacher_matrix_operator_norm_2p_moment_bound

B1 — the matrix-Khintchine operator-norm moment bound (trace-moment to operator-norm bridge). For a Hermitian family $H_c \in \mathbb{R}^{d\times d}$ ($d\ge 1$) with variance proxy bounded by $\mathrm{normV}$ (every eigenvalue of $\sum_c H_c^2$ is $\le \mathrm{normV}$), the Rademacher-average $2p$-th operator-norm moment satisfies, for $p\ge 1$,

where $\mathbb{E}_\varepsilon$ is the uniform average over the $2^{|\iota|}$ sign patterns (written as $\sum_{eps}(1/2)^{|\iota|}\,(\cdot)$). This is the standard Tropp/van Handel matrix-Khintchine operator-norm moment, obtained from the trace-moment engine general_rademacher_matrix_2p_trace_moment plus the crux $\lVert X\rVert_{op}^{2p}\le\operatorname{tr}(X^{2p})$, the constant bound $(2p)!/(2^p p!)\le(2p)^p$, Markov/monotonicity of $x\mapsto x^{1/2p}$, and $((2p)^p)^{1/2p}=\sqrt{2p}$. Needs $0<d$ and $1\le p$.