12: Eigenvalues and Eigenvectors
- Page ID
- 1734
Given only a vector space and no other structure, save for the zero vector, no vector is more important than any other. Once one also has a linear transformation the situation changes dramatically. Consider a vibrating string,
whose displacement at point \(x\) is given by a function \(y(x,t)\). The space of all displacement functions for the string can be modelled by a vector space \(V\). At this point, only the zero vector---the function \(y(x,t)=0\) drawn in grey---is the only special vector.
The wave equation
\[\frac{\partial^{2} y}{\partial t^{2}}=\frac{\partial^{2} y}{\partial x^{2}}\, ,\]
is a good model for the string's behavior in time and space. Hence we now have a linear transformation
\[\left(\frac{\partial^{2} }{\partial t^{2}}-\frac{\partial^{2} }{\partial x^{2}}\right):V\rightarrow V\, .\]
For example, the function
\[y(x,t)=\sin t \sin x\]
is a very special vector in \(V\), which obeys \(L y = 0\). It is an example of an eigenvector of \(L\).
Thumbnail: Mona Lisa with shear, eigenvector, and grid. Imaged used with permission (Public domain; TreyGreer62).
Contributor
David Cherney, Tom Denton, and Andrew Waldron (UC Davis)