Lieb–Liniger model
Physics models of a 1D gas of bosons From Wikipedia, the free encyclopedia
In physics, the Lieb–Liniger model describes a gas of particles moving in one dimension and satisfying Bose–Einstein statistics. More specifically, it describes a one dimensional Bose gas with Dirac delta interactions. It is named after Elliott H. Lieb and Werner Liniger who introduced the model in 1963.[1] The model was developed to compare and test Nikolay Bogolyubov's theory of a weakly interaction Bose gas.[2]
Definition
Given bosons moving in one-dimension on the -axis defined from with periodic boundary conditions, a state of the N-body system must be described by a many-body wave function . The Hamiltonian, of this model is introduced as
where is the Dirac delta function. The constant denotes the strength of the interaction, represents a repulsive interaction and an attractive interaction.[3] The hard core limit is known as the Tonks–Girardeau gas.[3]
For a collection of bosons, the wave function is unchanged under permutation of any two particles (permutation symmetry), i.e., for all and satisfies for all .
The delta function in the Hamiltonian gives rise to a boundary condition when two coordinates, say and are equal. The condition is that as approaches from above (), the derivative satisfies
- .
Solution
Summarize
Perspective

The time-independent Schrödinger equation , is solved by explicit construction of . Since is symmetric it is completely determined by its values in the simplex , defined by the condition that .
The solution can be written in the form of a Bethe ansatz as[2]
- ,
with wave vectors , where the sum is over all permutations, , of the integers , and maps to . The coefficients , as well as the 's are determined by the condition , and this leads to a total energy
- ,
with the amplitudes given by
These equations determine in terms of the 's. These lead to equations:[2]
where are integers when is odd and, when is even, they take values . For the ground state the 's satisfy
Thermodynamic limit
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References
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