May 1988

Multiplication Signs

In the Physical Review, centered dots are used only for inner products of vectors, dyadics, and the like:

$k · p$ = $\sum\limits_{i} k_{i}p_{i}$

$l · \mathop{{\rm{g}}}\limits^{\leftrightarrow} · s = \sum\limits_{i,j}l_{i}g_{ij}s_j$

$k · p = k_{μ}p^{μ}$

Omit the multiplication sign between scalars unless it serves a useful purpose - in which case use a large ×. (Please do not type an x.)

$6 × 10^{−3}$

$1 × 3 × · · · × (2n + 1)$

When a product continues on a new line, use × at the beginning of the new line only.

$e^{−x}(x^2 + y^2)^{3/2}$

$×(X + Y )$

For the vector product of three-vectors, the same × is normal. ($\wedge$ is not used for this purpose in the American literature.)

r × p