# Does a symbol exist for this operation?

1. Dec 17, 2011

### brydustin

(*)_pq = 1 if p> q else 0

This is kinda like kronecker delta in that its a relational operation. Any clue?

2. Dec 17, 2011

### spamiam

I think something with characteristic functions would work. Maybe something like

$$a_{pq} = \chi_{(q, \infty)}(p)$$

where
$$\chi_A(x) = \begin{cases} 0 & \text{if} \; \; x \notin A \\ 1 & \text{if} \; \; x \in A \; . \end{cases}$$
Does that help? Are p and q real numbers?

3. Dec 22, 2011

### jasonRF

the Heaviside step function can also be used for this (just a special case of a characteristic function):

$u(t)$ is 1 for $t>0$ and 0 for $t<0$.

Some folks capitalize the U.

jason