What Does the Notation <k>^N Represent in Mathematical Contexts?

[Canavar]

Hello,

i have found a notation, which i never saw before and i can't give some reasonable definition for it.
Perhaps some of you guys have seen it before and can help me.

let $$k \in \mathbb{Z}^n$$ and N be a constant, what does $$<k>^N$$ mean?

I will put more of the context, where this appears:
Let P(x) be a polynomial of order m on $$\mathbb{R}^n$$. For almost every $$\alpha \in A$$, there are constants C,N s.t.$$\left| P(k+\alpha)\right| \leq C<k>^N \forall k \in \mathbb{Z}^n$$.

Can you help me?

Regards

 

[hunt_mat]

I think that maybe that $<k>^{N}$ denotes the average of the elements of k raised to the power N.

 

[micromass]

Can you give a reference where this appears?