New approaches to quantum many-body theory
Main funder
Funder's project number: 317139
Funds granted by main funder (€)
- 468 863,00
Funding program
Project timetable
Project start date: 01/09/2018
Project end date: 31/12/2022
Summary
The present project wants to make a significant advance in the study of the properties of many-body systems in general, and electronic systems in particular. To do this we aim to develop several conceptually new approaches within the context of many-body perturbation theory in order to solve a number of long-standing issues that have hindered progress in the field. These approaches, based on recent work carried out by the applicant and collaborators, have a wide scope and range of applicability and considerably extend the toolbox of theoretical methods to investigate the physical properties of condensed matter systems.
The strength of the first theoretical tool that was developed, that is the extension of many-body theory to general initial states, makes it possible to deal with a larger class of systems in condensed matter theory, including ones with degenerate or nearly degenerate many-particle states and can further deal with general initial states in non-equilibrium systems. The second tool, a newly developed positive semi-definite perturbation theory, solves the long-standing issue of properly incorporating physically complex excitation processes involving multiple plasmons, excitons and general multiple excited states in a systematic fashion and further allows for self-consistent applications of standard and more sophisticated approximations in perturbation theory without the violations of physical properties that have plagued conventional approaches. Finally, importing techniques of the emerging field of resurgent perturbation theory to condensed matter physics, will make it possible to go beyond the perturbative limit, generating non-perturbative physics from perturbation theory and open up a new field of applications.
The aforementioned approaches, once implemented in ab-initio codes, will be applied to accurately describe a vast range of old and new phenomena in solid state and molecular physics.
The strength of the first theoretical tool that was developed, that is the extension of many-body theory to general initial states, makes it possible to deal with a larger class of systems in condensed matter theory, including ones with degenerate or nearly degenerate many-particle states and can further deal with general initial states in non-equilibrium systems. The second tool, a newly developed positive semi-definite perturbation theory, solves the long-standing issue of properly incorporating physically complex excitation processes involving multiple plasmons, excitons and general multiple excited states in a systematic fashion and further allows for self-consistent applications of standard and more sophisticated approximations in perturbation theory without the violations of physical properties that have plagued conventional approaches. Finally, importing techniques of the emerging field of resurgent perturbation theory to condensed matter physics, will make it possible to go beyond the perturbative limit, generating non-perturbative physics from perturbation theory and open up a new field of applications.
The aforementioned approaches, once implemented in ab-initio codes, will be applied to accurately describe a vast range of old and new phenomena in solid state and molecular physics.
Principal Investigator
Primary responsible unit
Follow-up groups
Related publications and other outputs
1 of 2
- Geometry of Degeneracy in Potential and Density Space (2023) Penz, Markus; et al.; A1; OA
- In and Out-of-Equilibrium Ab Initio Theory of Electrons and Phonons (2023) Stefanucci, Gianluca; et al.; A1; OA
- Cutting rules and positivity in finite temperature many-body theory (2022) Hyrkäs, Markku; et al.; A1; OA
- Time-linear scaling nonequilibrium Green's function method for real-time simulations of interacting electrons and bosons. II : Dynamics of polarons and doublons (2022) Pavlyukh, Y.; et al.; A1; OA
- Time-linear scaling nonequilibrium Green's function methods for real-time simulations of interacting electrons and bosons. I : Formalism (2022) Pavlyukh, Y.; et al.; A1; OA
- Density-functional theory on graphs (2021) Penz, Markus; et al.; A1; OA
- Fast Green’s Function Method for Ultrafast Electron-Boson Dynamics (2021) Karlsson, Daniel; et al.; A1; OA
- Quantum interference and the time-dependent radiation of nanojunctions (2021) Ridley, Michael; et al.; A1; OA
- Dynamically screened vertex correction to GW (2020) Pavlyukh, Yaroslav; et al.; A1; OA
- Diagrammatic Expansion for Positive Spectral Functions in the Steady-State Limit (2019) Hyrkäs, Markku; et al.; A1; OA
