Notation for bilinear form $y^t M z$, where $M$ is a matrix and $y,z$ are vectors. - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-18T22:28:13Z http://mathoverflow.net/feeds/question/46641 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/46641/notation-for-bilinear-form-yt-m-z-where-m-is-a-matrix-and-y-z-are-vectors Notation for bilinear form $y^t M z$, where $M$ is a matrix and $y,z$ are vectors. Louigi Addario-Berry 2010-11-19T15:29:48Z 2010-11-19T18:05:00Z <p>I'm working on a problem where I need to consider a bilinear form of the form $y^t M z$ where $M$ is an $n$-by-$n$ real symmetric matrix and <code>$y,z \in \mathbb{R}^n$</code> are vectors. I also need to consider restricted forms of such a product, of the form $$\sum_{i,j=1}^n y_i m_{ij} z_j \mathbf{I}_{(y_i,z_j) \in E},$$ where $E$ is some subset of $\mathbb{R}^2$. We recover $y^t M z$ by taking $E=\mathbb{R}^2$. I want a common notation for $y^t M z$ and for these restricted sums, so I have been writing $y^t M z = \langle y,z\rangle_M$, and writing $\langle y,z\rangle_{M,E}$ for the restricted sum above. </p> <p>I see nothing wrong with the notation I'm using. However, if there's a standard notation for such things that I am unaware of, I would like to know about it. Is there? If you know of another notation, can you give me a reference?</p>