Sign convention
From Biocrawler, the free encyclopedia.
In some physics textbooks and articles, certain quantities are defined with the opposite sign from that which is used in other publications. This lack of standardization is a frequent source of confusion, misunderstandings, and even outright errors. A standard choice of sign for a definition is called a sign convention. Sometimes, this term is used more broadly to include factors of i and 2π.
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 field strength tensor in gauge theories and classical electrodynamics.
- The sign of work in the first law of thermodynamics.
- Time dependence of a positive-frequency wave:
- exp( − iωt) (mainly used by physicists)
- exp( + jωt) (mainly used by engineers)
It is often considered good form to state explicitly which sign convention is to be used at the beginning of each book or article.
