Study of multi-particle states with tensor renormalization group method

TL;DR

This paper applies tensor renormalization group techniques to analyze multi-particle states in the (1+1)-dimensional Ising model, providing a detailed spectral and scattering analysis.

Contribution

It introduces a spectroscopy scheme based on tensor networks to identify multi-particle states and compute scattering phase shifts in the Ising model.

Findings

Successfully identified one-, two-, and three-particle states.

Computed scattering phase shifts consistent with exact predictions.

Demonstrated the effectiveness of tensor network methods for spectral analysis.

Abstract

We investigate the multi-particle states of the (1+1)-dimensional Ising model using a spectroscopy scheme based on the tensor renormalization group method. We start by computing the finite-volume energy spectrum of the model from the transfer matrix, which is numerically estimated using the coarse-grained tensor network. We then identify the quantum number and momentum of the eigenstates by using the symmetries of the system and the matrix elements of an appropriate interpolating operator. Next, we plot the energy for a particular quantum number and momentum as a function of system size to identify the number of particles in the corresponding energy eigenstates. With this method, we obtain one-, two-, and three-particle states. We also compute the two-particle scattering phase shift using L\"uscher's formula as well as the wave function approach, and compare the results with the exact prediction.