Chapter 2Many Body Problem § Second quantization The identical particles cannot be distinguished § Second quantization The essence of the identical principle is that the state of a system should be described in terms of the particle number in a certain quantum state and the many-body problem should be discussed in the particle number representation instead of the original coordinate representation § Second quantization We need to introduce the creation and the annihilation operators to deal with various problem in the many-body system § Second quantization Bose system § Second quantization