\text{\textbardbl}The symbol \text{\textbardbl} represents a double vertical bar, often used in mathematical notation to denote norms, parallel lines, or other specific operations depending on the context. It is a versatile symbol that can be applied in various mathematical expressions and equations.
Denoting the Euclidean norm of a vector x.
\|x\| = \sqrt{x_1^2 + x_2^2 + \cdots + x_n^2}Representing parallel lines A and B in geometry.
A \text{\textbardbl} BFrobenius norm of a matrix A.
\|A\|_F = \sqrt{\sum_{i,j} |a_{ij}|^2}