The double bar symbol is used to denote certain kinds of norms in mathematics (e.g., or ). It is also used to denote parallel lines, as in , and in an older notation for the covariant derivative. In this work, the notation or is reserved for matrix and function norms, respectively.
Double Bar
See also
Bar, Covariant Derivative, Norm, Matrix Norm, Parallel, Single BarExplore with Wolfram|Alpha
References
Bringhurst, R. The Elements of Typographic Style, 2nd ed. Point Roberts, WA: Hartley and Marks, p. 277, 1997.Referenced on Wolfram|Alpha
Double BarCite this as:
Weisstein, Eric W. "Double Bar." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/DoubleBar.html