Sign convention
Annoyingly often in physics, some textbooks and articles use definitions for certain quantities with the opposite sign from other textbook/articles. This lack of standardization is a frequent source of confusion, misunderstandings and even outright errors. A choice of signs in the definition is called a sign convention. Sometimes, this term is used more sloppily to include factors of i and 2
.
A noncomprehensive list of sign conventions:
- In relativity, the metric signature could either be +--- or -+++.
- The choice of
in the Dirac equation.
- The sign of the Faraday 2-form in gauge theories.
- The sign of work in the first law of thermodynamics.
- Time dependence of an electromagnetic wave:
- exp(iωt) (mainly used by physicists)
- exp( - jωt) (mainly used by engineers)
It is often considered good form to explicitly state which sign convention you are using at the beginning of every article/book.
Warning: Since this encyclopedia is written by hundreds of different mathematicians/physicists, there is absolutely no guarantee of consistency in sign conventions here. Proceed at your own peril.