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basic_tools:symbols [2018/03/28 16:09] jakobadmin |
basic_tools:symbols [2018/04/15 12:20] (current) ida |
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====== Symbols ====== | ====== Symbols ====== | ||
+ | |||
+ | * Derivatives with respect to the four-vector $x^{\mu}=(ct,\vec{x})$ are denoted by | ||
+ | \begin{eqnarray} | ||
+ | \partial_{\mu}\equiv {\partial\over \partial x^{\mu}} | ||
+ | =\left({1\over c}{\partial\over\partial t},\vec{\nabla}\right). | ||
+ | \end{eqnarray} | ||
+ | * Space-time indices are labelled by Greek letters ($\mu,\nu,\ldots=0,1,2,3$) | ||
+ | * Latin indices are used for spatial directions ($i,j,\ldots=1,2,3$). | ||
+ | * Moreover, $\sigma^{\mu}=(\mathbf{1},\sigma^{i})$ where $\sigma^{i}$ are the Pauli matrices $$ | ||
+ | \sigma^{1}=\left( | ||
+ | \begin{array}{rr} | ||
+ | 0 & 1 \\ | ||
+ | 1 & 0 | ||
+ | \end{array} | ||
+ | \right), \quad \sigma^{2}=\left( | ||
+ | \begin{array}{rr} | ||
+ | 0 & -i \\ | ||
+ | i & 0 | ||
+ | \end{array} | ||
+ | \right), \quad | ||
+ | \sigma^{3}=\left( | ||
+ | \begin{array}{rr} | ||
+ | 1 & 0 \\ | ||
+ | 0 & -1 | ||
+ | \end{array} | ||
+ | \right).$$ | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | **Math Symbols** | ||
\begin{align} | \begin{align} | ||
&\mathbb{N} = \{0, 1, 2, 3, \ldots\} \\ | &\mathbb{N} = \{0, 1, 2, 3, \ldots\} \\ | ||
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&\subset \; \rm is \; ``subset\; of" \\ | &\subset \; \rm is \; ``subset\; of" \\ | ||
&\equiv \; \rm is\;``defined\; as" \\ | &\equiv \; \rm is\;``defined\; as" \\ | ||
- | = & \quad \text{exactly equal} \notag \\ | + | &= \quad \text{exactly equal} \notag \\ |
- | \propto & \quad \text{equality except perhaps for a factor with dimension} \notag\\ | + | &\propto \quad \text{equality except perhaps for a factor with dimension} \notag\\ |
- | \sim & \quad \text{equality except perhaps for a factor without dimensions} \notag \\ | + | &\sim \quad \text{equality except perhaps for a factor without dimensions} \notag \\ |
- | \approx & \quad \text{equality except perhaps for a factor close to 1} | + | &\approx \quad \text{equality except perhaps for a factor close to 1} |
\end{align} | \end{align} | ||
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