Failure of Strong Convergence of Matrices with Fermionic Entries

Let $Q_N^{(k)}$ be an $N\times N$ matrices with entries satisfying CAR, normalized to have variance $1\mathrm{/}\sqrt{N}$ with respect to the trace of the CAR algebra. We show that, although the operator norm of the real part of an individual matrix $Q_N^{(k)}$ converges as $N\to \mathrm{\infty }$ to the semicircular limit, the family of matrices does not converge to the free probability limit strongly. In fact, even the operator space structure of the linear spans of the real and imaginary parts of $Q_N^{(k)}$’s, $k=1,\dots ,M$, does not converge to the semicircular limit.