What notation and symbols are commonly used here?

What notation and symbols are commonly used here?

Physics relies heavily on math. Many posts include mathematical notation, written using LaTeX commands and delimited by dollar signs. If you see dollar signs with what appears to be gibberish between them, it just means that MathJax, the math rendering we use, isn't working properly for you.

Some basics for people new to LaTeX. Inline formulas are surrounded by single dollar signs ($f(x) = ax^2 + bx + c$ renders as $f(x) = ax^2 + bx + c$), and block formulas by double dollar signs so that $$x = \frac{-b \pm \sqrt{b^2 - 4ac} }{2a}$$ renders as

$$x = \frac{-b \pm \sqrt{b^2 - 4ac} }{2a}$$

Greek letters are mostly written by simply spelling them after a backslash with capitalization indicated by first letter. That is \alpha \beta \Gamma \Delta renders as αβΓΔ.