Notation: brackets surrounding a matrix

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I am trying to answer a question about eigenvalues of a 2x2 Hermitian matrix H, and am being asked to find (H) in terms of the two eigenvalues.

However, I am not sure what the brackets around the H mean, outside of normal multiplication brackets.

Thanks!

The question is worded as follows:

$\lambda_1$ and $\lambda_2$ are the two distinct eigenvalues of a 2 x 2 Hermitian matrix H, with corresponding normalised eigenvectors $e_1$ and $e_2$. Find in terms of $\lambda_1$ and $\lambda_2$:

(i) det(H) -- already completed

(ii) (H).