Picture (string theory)

In superstring theory, each state may be represented by many ways, depending on the way the ground state is defined. Each representation is called a picture, and is denoted by a number, such as 0 picture, -1 picture, etc. The difference between the ground states is according to the action of the superghosts oscillators on them, and the number of the picture (plus 1/2) reflects the highest superghost oscillator which does not annihilate the ground state.