222 citations · 2k across the 49 of their papers we have counts for
50 papers
Avoided crossings in spin-boson systems: consequences for adiabatic state preparation
Joona Marjamäki, Robert van Leeuwen, Riku Tuovinen
Avoided crossings in the correlated many-body spectrum play a central role in determining the conditions for adiabatic state preparation in interacting quantum systems. We investig…
Revealing symmetries in quantum computing for many-body systems
Robert van Leeuwen
We develop a method to deduce the symmetry properties of many-body Hamiltonians when they are prepared in Jordan-Wigner form for evaluation on quantum computers. Symmetries, such a…
Geometrical Perspective on Spin-Lattice Density-Functional Theory
Markus Penz, Robert van Leeuwen
A recently developed viewpoint on the fundamentals of density-functional theory for finite interacting spin-lattice systems that centers around the notion of degeneracy regions is…
From S-matrix theory to strings: Scattering data and the commitment to non-arbitrariness
Robert van Leeuwen
The early history of string theory is marked by a shift from strong interaction physics to quantum gravity. The first string models and associated theoretical framework were formul…
Solution of the v-representability problem on a one-dimensional torus
Sarina M. Sutter, Markus Penz, Michael Ruggenthaler +2
We provide a solution to the v-representability problem for a non-relativistic quantum many-particle system on a ring domain in terms of Sobolev spaces and their duals. Any one-par…
In- and out-of-equilibrium {\em ab initio} theory of electrons and phonons
Gianluca Stefanucci, Robert van Leeuwen, Enrico Perfetto
We lay down the {\em ab initio} many-body quantum theory of electrons and phonons in- and out-of-equilibrium at any temperature. We begin by addressing a fundamental issue concerni…
Geometry of Degeneracy in Potential and Density Space
Markus Penz, Robert van Leeuwen
In a previous work [J. Chem. Phys. 155, 244111 (2021)], we found counterexamples to the fundamental Hohenberg-Kohn theorem from density-functional theory in finite-lattice systems…
Cutting rules and positivity in finite temperature many-body theory
Markku J. Hyrkäs, Daniel Karlsson, Robert van Leeuwen
For a given diagrammatic approximation in many-body perturbation theory it is not guaranteed that positive observables, such as the density or the spectral function, retain their p…
Time-linear scaling NEGF methods for real-time simulations of interacting electrons and bosons. II. Dynamics of polarons and doublons
Yaroslav Pavlyukh, Enrico Perfetto, Daniel Karlsson +2
Nonequilibrium dynamics of the open chain Holstein-Hubbard model is studied using the linear time-scaling GKBA+ODE scheme developed in the preceeding paper. We focus on the set of…
Time-linear scaling NEGF methods for real-time simulations of interacting electrons and bosons. I. Formalism
Yaroslav Pavlyukh, Enrico Perfetto, Daniel Karlsson +2
Simulations of interacting electrons and bosons out of equilibrium, starting from first principles and aiming at realistic multiscale scenarios, is a grand theoretical challenge. H…
Density-Functional Theory on Graphs
Markus Penz, Robert van Leeuwen
The principles of density-functional theory are studied for finite lattice systems represented by graphs. Surprisingly, the fundamental Hohenberg-Kohn theorem is found void in gene…
Fast Green's function method for ultrafast electron-boson dynamics
Daniel Karlsson, Robert van Leeuwen, Yaroslav Pavlyukh +2
The interaction of electrons with quantized phonons and photons underlies the ultrafast dynamics of systems ranging from molecules to solids, and it gives rise to a plethora of phy…
Time-dependent density-functional theory for strongly interacting electrons
Luis Cort, Daniel Karlsson, Giovanna Lani +1
We consider an analytically solvable model of two interacting electrons that allows for the calculation of the exact exchange-correlation kernel of time-dependent density functiona…
Vertex corrections for positive-definite spectral functions of simple metals
Y. Pavlyukh, A. -M. Uimonen, G. Stefanucci +1
We present a systematic study of vertex corrections in the homogeneous electron gas at metallic densities. The vertex diagrams are built using a recently proposed positive-definite…
Partial self-consistency and analyticity in many-body perturbation theory: particle number conservation and a generalized sum rule
Daniel Karlsson, Robert van Leeuwen
We consider a general class of approximations which guarantees the conservation of particle number in many-body perturbation theory. To do this we extend the concept of -derivab…
The adiabatic strictly-correlated-electrons functional: kernel and exact properties
Giovanna Lani, Simone di Marino, Augusto Gerolin +2
We investigate a number of formal properties of the adiabatic strictly-correlated electrons (SCE) functional, relevant for time-dependent potentials and for kernels in linear respo…
Computing Exact Self-Energies with Polynomial Expansion
M. Hyrkäs, D. Karlsson, R. van Leeuwen
We give details on how to calculate spectral functions and Green's functions for finite systems using the Chebyshev polynomial expansion method. We apply the method to a finite And…
Development of non-equilibrium Green's functions for use with full interaction in complex systems
Richard A. Lynn, Robert van Leeuwen
We present an ongoing development of an existing code for calculating ground-state, steady-state, and transient properties of many-particle systems. The development involves the ad…
Time-dependent Landauer-Büttiker formalism for superconducting junctions at arbitrary temperatures
Riku Tuovinen, Robert van Leeuwen, Enrico Perfetto +1
We discuss an extension of our earlier work on the time-dependent Landauer--Büttiker formalism for noninteracting electronic transport. The formalism can without complication be ex…
Many-body Green's function theory for electron-phonon interactions: the Kadanoff-Baym approach to spectral properties of the Holstein dimer
N. Säkkinen, Y. Peng, H. Appel +1
We present a Kadanoff-Baym formalism to study time-dependent phenomena for systems of interacting electrons and phonons in the framework of many-body perturbation theory. The forma…
First-principles nonequilibrium Green's function approach to transient photoabsorption: Application to atoms
E. Perfetto, A. -M. Uimonen, R. van Leeuwen +1
We put forward a first-principle NonEquilibrium Green's Function (NEGF) approach to calculate the transient photoabsorption spectrum of optically thin samples. The method can deal…
Curvature in graphene nanoribbons generates temporally and spatially focused electric currents
C. G. Rocha, R. Tuovinen, R. van Leeuwen +1
Today graphene nanoribbons and other graphene-based nanostructures can be synthesized with atomic precision. But while investigations have concentrated on straight graphene ribbons…
Quantum Control of Many-Body Systems by the Density
S. E. B. Nielsen, M. Ruggenthaler, R. van Leeuwen
In this work we focus on a recently introduced method [1] to construct the external potential that, for a given initial state, produces a prescribed time-dependent density in a…
Existence, Uniqueness, and Construction of the Density-Potential Mapping in Time-Dependent Density-Functional Theory
Michael Ruggenthaler, Markus Penz, Robert van Leeuwen
In this work we review the mapping from densities to potentials in quantum mechanics, which is the basic building block of time-dependent density-functional theory and the Kohn-Sha…