String Theory

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Notation

The metric has signature ${\displaystyle (+,-,-,-,...)}$ .

Greek letters from the middle of the alphabet ${\displaystyle (\mu ,\nu ,...)}$  denote coordinates in spacetime. Roman letters taken from the beginning of the alphabet ${\displaystyle (a,b,...)}$  denote coordinates on the worldsheet.

The metric is denoted ${\displaystyle g_{\mu \nu }}$ . In the case where there is a metric of spacetime and a metric of the worldsheet, the worldsheet metric is denoted ${\displaystyle h_{ab}}$

A lower-case ${\displaystyle d}$  is the number of dimensions. An upper-class ${\displaystyle D}$  represents the number of spacial dimensions.