What is orthonormality: Definition and 1 Discussions
In linear algebra, two vectors in an inner product space are orthonormal if they are orthogonal unit vectors. A unit vector means that the vector has a length of 1, which is also known as normalized. Orthogonal means that the vectors are all perpendicular to each other. A set of vectors form an orthonormal set if all vectors in the set are mutually orthogonal and all of unit length. An orthonormal set which forms a basis is called an orthonormal basis.
I'm reading Stefanucci's Nonequilibrium Many Body Theory of Quantum Systems.
In the first chapter, where it goes over basic quantum mechanics, it first defines the usual orthonormality condition I'm familiar with,
$$\langle n' | n \rangle = \delta_{n, n'} $$
where $$ | n \rangle$$ is the ket...