The Sign convention reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

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 Complex number and 2Pi.

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:
  • (mainly used by physicists)
  • (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.

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