\dArrThe \dArr command in LaTeX is used to produce a downward double arrow, which is often used in mathematical notation to indicate a mapping or transformation that occurs in a downward direction.
Indicates a transformation from A to B in a downward direction.
A \dArr BRepresents a mapping from x to y with a downward double arrow.
x \dArr yUsed to denote a limit process as n approaches infinity, with emphasis on the downward direction.
\dArr_{n \to \infty}