# 겔만 행렬(Gell-Mann matrices)

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## 개요

• a family of traceless Hermitian -matrices, orthonormalized$\left( \begin{array}{ccc} 0 & 1 & 0 \\ 1 & 0 & 0 \\ 0 & 0 & 0 \end{array} \right),\left( \begin{array}{ccc} 0 & -i & 0 \\ i & 0 & 0 \\ 0 & 0 & 0 \end{array} \right),\left( \begin{array}{ccc} 1 & 0 & 0 \\ 0 & -1 & 0 \\ 0 & 0 & 0 \end{array} \right),\left( \begin{array}{ccc} 0 & 0 & 1 \\ 0 & 0 & 0 \\ 1 & 0 & 0 \end{array} \right),\left( \begin{array}{ccc} 0 & 0 & -i \\ 0 & 0 & 0 \\ i & 0 & 0 \end{array} \right),\left( \begin{array}{ccc} 0 & 0 & 0 \\ 0 & 0 & 1 \\ 0 & 1 & 0 \end{array} \right),\left( \begin{array}{ccc} 0 & 0 & 0 \\ 0 & 0 & -i \\ 0 & i & 0 \end{array} \right),\left( \begin{array}{ccc} \frac{1}{\sqrt{3}} & 0 & 0 \\ 0 & \frac{1}{\sqrt{3}} & 0 \\ 0 & 0 & -\frac{2}{\sqrt{3}} \end{array} \right)$
• 리대수 $$\mathfrak{su}(3)$$ 의 기저
• 쿼크를 다루기 위해 도입됨
• SU(3) 대칭성이 등장하는 게이지 이론 에서 사용된다

## 성질

• $$[g_i, g_j] = if^{ijk} g_k$$
• $$f^{123} = 1 \ , \quad f^{147} = f^{165} = f^{246} = f^{257} = f^{345} = f^{376} = \frac{1}{2} \ , \quad f^{458} = f^{678} = \frac{\sqrt{3}}{2}$$
• $$\mathrm{tr}(\lambda_i \lambda_j) = 2\delta_{ij}$$

## 관련도서

• M. Gell-Mann, Y. Ne'eman, "The eightfold way" , Benjamin (1964)