# nLab Einstein summation convention

Contents

### Context

#### Monoidal categories

monoidal categories

# Contents

## Idea

In situations such as the tensor calculus, the Einstein summation convention allows for compact expression of sums over common upper and lower indices. For example, for $n$-dimensional vector $v$ and covector $e$, we write $v_i e^i \coloneqq \sum_{1 \le i \le n} v_i e^i$.

## References

See also

Last revised on October 16, 2017 at 11:25:54. See the history of this page for a list of all contributions to it.