The set of functions may be considered a basis not belonging to L 2 x , labeled by the continuous index p. We write , or . This is an equivalent definition of the Dirac d function. Dirac Notation A vector is completely specified by its components in a given basis. The same vector can be represented by distinct sets of components corresponding to different choices of bases.
Dirac notation is a representation of a vector without an explicit choice of a basis.
Any element in V is called a ket vector or ket . But if we write A , we specify the vector without explicitly choosing a basis. The quantum state of any physical system is characterized by a state vector, belonging to a space E , which is the state space of the system. This correspondence is anti linear . Kets and bras are adjoints of each other.