nLab
Einstein summation convention

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Context

Linear algebra

homotopy theory, (∞,1)-category theory, homotopy type theory

flavors: stable, equivariant, rational, p-adic, proper, geometric, cohesive, directed

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see also algebraic topology

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monoidal categories

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In higher category theory

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 nn-dimensional vector vv and covector ee, we write v ie i 1inv ie iv_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.