irbasis: Open-source database and software for intermediate-representation basis functions of imaginary-time Green's function

TL;DR

irbasis is an open-source library that provides tools and a database for intermediate representation basis functions, enabling compact representation and efficient computation of Matsubara Green's functions in quantum models.

Contribution

The paper introduces irbasis, a library with pre-computed IR basis functions and tools, facilitating easier and more efficient quantum Green's function calculations.

Findings

Provides a database of high-precision IR basis functions

Enables compact representation of Green's functions

Facilitates efficient quantum model computations

Abstract

The open-source library, irbasis, provides easy-to-use tools for two sets of orthogonal functions named intermediate representation (IR). The IR basis enables a compact representation of the Matsubara Green's function and efficient calculations of quantum models. The IR basis functions are defined as the solution of an integral equation whose analytical solution is not available for this moment. The library consists of a database of pre-computed high-precision numerical solutions and computational code for evaluating the functions from the database. This paper describes technical details and demonstrates how to use the library.