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