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We introduce cppdlr, a C++ library implementing the discrete Lehmann representation (DLR) of functions in imaginary time and Matsubara frequency, such as Green's functions and self-energies. The DLR is based on a low-rank approximation of…

Computational Physics · Physics 2024-08-08 Jason Kaye , Hugo U. R. Strand , Nils Wentzell

We present an efficient basis for imaginary time Green's functions based on a low rank decomposition of the spectral Lehmann representation. The basis functions are simply a set of well-chosen exponentials, so the corresponding expansion…

Numerical Analysis · Mathematics 2023-07-31 Jason Kaye , Kun Chen , Olivier Parcollet

We present a generalization of the discrete Lehmann representation (DLR) to three-point correlation and vertex functions in imaginary time and Matsubara frequency. The representation takes the form of a linear combination of judiciously…

Computational Physics · Physics 2025-03-27 Dominik Kiese , Hugo U. R. Strand , Kun Chen , Nils Wentzell , Olivier Parcollet , Jason Kaye

We present a deterministic algorithm for the efficient evaluation of imaginary time diagrams based on the recently introduced discrete Lehmann representation (DLR) of imaginary time Green's functions. In addition to the efficient…

Strongly Correlated Electrons · Physics 2024-11-21 Jason Kaye , Zhen Huang , Hugo U. R. Strand , Denis Golež

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…

Computational Physics · Physics 2019-06-28 Naoya Chikano , Kazuyoshi Yoshimi , Junya Otsuki , Hiroshi Shinaoka

New model-independent compact representations of imaginary-time data are presented in terms of the intermediate representation (IR) of analytical continuation. This is motivated by a recent numerical finding by the authors [J. Otsuki et…

Strongly Correlated Electrons · Physics 2017-07-26 Hiroshi Shinaoka , Junya Otsuki , Masayuki Ohzeki , Kazuyoshi Yoshimi

Several recent works have introduced highly compact representations of single-particle Green's functions in the imaginary time and Matsubara frequency domains, as well as efficient interpolation grids used to recover the representations. In…

Strongly Correlated Electrons · Physics 2023-06-28 Nan Sheng , Alexander Hampel , Sophie Beck , Olivier Parcollet , Nils Wentzell , Jason Kaye , Kun Chen

Green's function methods lead to ab initio, systematically improvable simulations of molecules and materials while providing access to multiple experimentally observable properties such as the density of states and the spectral function.…

Quantum Physics · Physics 2023-09-19 Diksha Dhawan , Dominika Zgid , Mario Motta

Inspired by the recent proposed Legendre orthogonal polynomial representation of imaginary-time Green's functions, we develop an alternate representation for the Green's functions of quantum impurity models and combine it with the…

Strongly Correlated Electrons · Physics 2016-12-08 Li Huang , Liang Du

We study the expansion of single-particle and two-particle imaginary-time Matsubara Green's functions of quantum impurity models in the basis of Legendre orthogonal polynomials. We discuss various applications within the dynamical…

Strongly Correlated Electrons · Physics 2015-03-19 Lewin Boehnke , Hartmut Hafermann , Michel Ferrero , Frank Lechermann , Olivier Parcollet

In this article we use linear algebra to improve the computational time for the obtaining of Green's functions of linear differential equations with reflection (DER). This is achieved by decomposing both the `reduced' equation (the ODE…

Classical Analysis and ODEs · Mathematics 2017-07-05 F. Adrián F. Tojo

Discrete Diffusion Language Models (DLMs) offer a promising non-autoregressive alternative for text generation, yet effective mechanisms for inference-time control remain relatively underexplored. Existing approaches include sampling-level…

Computation and Language · Computer Science 2026-01-30 Eden Avrahami , Eliya Nachmani

Discrete Green's functions are the inverses or pseudo-inverses of combinatorial Laplacians. We present compact formulas for discrete Green's functions, in terms of the eigensystems of corresponding Laplacians, for products of regular graphs…

Combinatorics · Mathematics 2007-05-23 Robert B. Ellis

Dimensionality reduction (DR) is a popular method for preparing and analyzing high-dimensional data. Reduced data representations are less computationally intensive and easier to manage and visualize, while retaining a significant…

Machine Learning · Computer Science 2022-05-02 Avraam Bardos , Ioannis Mollas , Nick Bassiliades , Grigorios Tsoumakas

The library of practical abstractions (LIBPA) provides efficient implementations of conceptually simple abstractions, in the C programming language. We believe that the best library code is conceptually simple so that it will be easily…

cmp-lg · Computer Science 2009-09-25 Eric Sven Ristad , Peter N. Yianilos

We introduce ReservoirComputing.jl, an open source Julia library for reservoir computing models. The software offers a great number of algorithms presented in the literature, and allows to expand on them with both internal and external…

Computational Engineering, Finance, and Science · Computer Science 2023-07-04 Francesco Martinuzzi , Chris Rackauckas , Anas Abdelrehim , Miguel D. Mahecha , Karin Mora

Quantitative descriptions of strongly correlated materials pose a considerable challenge in condensed matter physics and chemistry. A promising approach to address this problem is quantum embedding methods. In particular, the dynamical…

Quantum Physics · Physics 2024-05-07 Rihito Sakurai , Wataru Mizukami , Hiroshi Shinaoka

We present a fast iterative solver for scattering problems in 2D, where a penetrable object with compact support is considered. By representing the scattered field as a volume potential in terms of the Green's function, we arrive at the…

Numerical Analysis · Mathematics 2023-03-28 Vaishnavi Gujjula , Sivaram Ambikasaran

Deep learning based latent representations have been widely used for numerous scientific visualization applications such as isosurface similarity analysis, volume rendering, flow field synthesis, and data reduction, just to name a few.…

Machine Learning · Computer Science 2023-08-10 Jingyi Shen , Haoyu Li , Jiayi Xu , Ayan Biswas , Han-Wei Shen

Using a map between the Lindbladian evolution of dephasing in free fermions and the time evolution of imaginary-interaction Fermi-Hubbard models in bipartite lattices, we present an efficient classical algorithm to solve the Schr\"{o}dinger…

Quantum Physics · Physics 2026-01-21 Raul A. Santos
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