Hello, i’ll give some context first:

Let \mathscr{P} be a partition of the domain \Omega into N_{E} disjoint open elements \Omega_{e} :

where \bar{\Omega} is the closure of \Omega. Each element \Omega_{e} has a boundary \partial \Omega_{e} and the outward unit normal to \partial \Omega_{e} is \mathbf{n}_{e}. Let \Gamma be the ensemble of interelement boundaries \Gamma_{l}=\partial \Omega_{e} \cap \partial \Omega_{f} with e>f inside the domain, with all possible combinations:

where N_{\Gamma} is the number of elements in \Gamma. Each \Gamma_{l} \in \Gamma is associated with a unique unit normal vector \mathbf{n} which points from \Omega_{e} to \Omega_{f}.

Now i’m triyng to define

and

I know i can write \langle\mathbf{s}\rangle as

```
avg(s)
```

How can i write \langle\mathbf{s}\rangle_{\lambda}? Thanks for the help!