Simen Kvaal
I am a researcher at the Hylleraas centre. My main interests are analysis and development of variational principles and computational methods for the solution of the nonrelativistic Schrödinger equation for molecular systems, both stationary and explicitly timedependent systems. I have done fundamental research in densityfunctional theory, coupledcluster theory, multiconfigurational timedependent Hartree theory, and developed novel algorithms for the numerical solution of nonlinear eigenvalue problems.
Late 2014, I was awarded an ERC starting grant, which dived into the very fundamentals of quantum theory by studying the bivariational principle. This is a generalization of the standard variational principle that is the foundation for almost every computational scheme for quantum mechanics.
In the academic year 2021–2022 I am leading a project at the Centre for Advanced Study (CAS) at the Academy of Science and Letters (DNVA) together with Prof. Thomas Bondo Pedersen. Our aim is to develop novel methods for the study of attosecond dynamics of molecular systems beyond the Born–Oppenheimer approximation.
I 2022 the project QOMBINE  Mathematics for quantum computation and manybody theory was funded by the Research Council of Norway and the Faculty of Natural Sciences at UiO. The project, led by Prof. Nadia Slavila Larsen at the Department of Mathematics, is a unique interdisciplinary collaboration between researchers in mathematics, physics, and chemistry.
Publications

Kristiansen, Håkon Emil; Ofstad, Benedicte Sverdrup; Hauge, Eirill Strand; Aurbakken, Einar; Schøyen, Øyvind Sigmundson & Kvaal, Simen [Show all 7 contributors for this article] (2022). Linear and Nonlinear Optical Properties from TDOMP2 Theory. Journal of Chemical Theory and Computation. ISSN 15499618. doi: 10.1021/acs.jctc.1c01309. Full text in Research Archive

Kvaal, Simen; Laestadius, Andre; Tellgren, Erik Ingemar & Helgaker, Trygve (2021). Lower Semicontinuity of the Universal Functional in Paramagnetic CurrentDensity Functional Theory. The Journal of Physical Chemistry Letters. ISSN 19487185. 12(5), p. 1421–1425. doi: 10.1021/acs.jpclett.0c03422. Full text in Research Archive

Pedersen, Thomas Bondo; Kristiansen, Håkon Emil; Bodenstein, Tilmann; Kvaal, Simen & Schøyen, Øyvind Sigmundson (2021). Interpretation of CoupledCluster ManyElectron Dynamics in Terms of Stationary States. Journal of Chemical Theory and Computation. ISSN 15499618. 17(1), p. 388–404. doi: 10.1021/acs.jctc.0c00977. Full text in Research Archive Show summary

Bodenstein, Tilmann & Kvaal, Simen (2020). A statespecific multireference coupledcluster method based on the bivariational principle. Journal of Chemical Physics. ISSN 00219606. 153(2). doi: 10.1063/5.0009429. Full text in Research Archive

Kvaal, Simen; Laestadius, Andre & Bodenstein, Tilmann (2020). Guaranteed convergence for a class of coupledcluster methods based on Arponen's extended theory. Molecular Physics. ISSN 00268976. 118(1920). doi: 10.1080/00268976.2020.1810349. Full text in Research Archive

Kristiansen, Håkon Emil; Schøyen, Øyvind Sigmundson; Kvaal, Simen & Pedersen, Thomas Bondo (2020). Numerical stability of timedependent coupledcluster methods for manyelectron dynamics in intense laser pulses. Journal of Chemical Physics. ISSN 00219606. 152. doi: 10.1063/1.5142276. Full text in Research Archive

Faulstich, Fabian Maximilian; Laestadius, Andre; Legeza, Örs; Schneider, Reinhold & Kvaal, Simen (2019). Analysis of the Tailored CoupledCluster Method in Quantum Chemistry . SIAM Journal on Numerical Analysis. ISSN 00361429. 57(6), p. 2579–2607. doi: 10.1137/18M1171436. Full text in Research Archive

Faulstich, Fabian Maximilian; Máté, Mihály; Laestadius, Andre; Csirik, Mihály András; Veis, Libor & Antalik, Andrej [Show all 11 contributors for this article] (2019). Numerical and Theoretical Aspects of the DMRGTCC Method Exemplified by the Nitrogen Dimer. Journal of Chemical Theory and Computation. ISSN 15499618. 15(4), p. 2206–2220. doi: 10.1021/acs.jctc.8b00960. Show summary

Laestadius, Andre; Tellgren, Erik; Penz, Markus; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2019). Kohn–Sham Theory with Paramagnetic Currents: Compatibility and Functional Differentiability. Journal of Chemical Theory and Computation. ISSN 15499618. 15(7), p. 4003–4020. doi: 10.1021/acs.jctc.9b00141.

Pedersen, Thomas Bondo & Kvaal, Simen (2019). Symplectic integration and physical interpretation of timedependent coupledcluster theory. Journal of Chemical Physics. ISSN 00219606. 150. doi: 10.1063/1.5085390. Full text in Research Archive Show summary

Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2018). Generalized KohnSham iteration on Banach spaces. Journal of Chemical Physics. ISSN 00219606. 149(16), p. 1–9. doi: 10.1063/1.5037790. Full text in Research Archive

Laestadius, Andre & Kvaal, Simen (2018). Analysis of the Extended CoupledCluster Method in Quantum Chemistry. SIAM Journal on Numerical Analysis. ISSN 00361429. 56(2), p. 660–683. doi: 10.1137/17M1116611. Full text in Research Archive

Tellgren, Erik; Laestadius, Andre; Helgaker, Trygve; Kvaal, Simen & Teale, Andrew Michael (2018). Uniform magnetic fields in densityfunctional theory. Journal of Chemical Physics. ISSN 00219606. 148(2), p. 1–19. doi: 10.1063/1.5007300.

Kvaal, Simen & Helgaker, Trygve (2015). Groundstate densities from the RayleighRitz variation principle and from densityfunctional theory. Journal of Chemical Physics. ISSN 00219606. 143(18). doi: 10.1063/1.4934797.

Jarlebring, Elias; Kvaal, Simen & Michiels, Wim (2014). An inverse iteration method for eigenvalue problems with eigenvector nonlinearities. SIAM Journal on Scientific Computing. ISSN 10648275. 36(4), p. A1978–A2001. doi: 10.1137/130910014.

Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2014). Differentiable but exact formulation of densityfunctional theory. Journal of Chemical Physics. ISSN 00219606. 140(18). doi: 10.1063/1.4867005.

Tellgren, Erik; Kvaal, Simen & Helgaker, Trygve (2014). Fermion N representability for prescribed density and paramagnetic current density. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 10502947. 89(1). doi: 10.1103/PhysRevA.89.012515. Full text in Research Archive

Kvaal, Simen (2013). Variational formulations of the coupledcluster method in quantum chemistry. Molecular Physics. ISSN 00268976. 111(911), p. 1100–1108. doi: 10.1080/00268976.2013.812254.

Kvaal, Simen (2012). Ab initio quantum dynamics using coupledcluster. Journal of Chemical Physics. ISSN 00219606. 136(19). doi: 10.1063/1.4718427.

Halvorsen, Tore Gunnar & Kvaal, Simen (2012). Manifestly gauge invariant discretizations of the Schrodinger equation. Physics Letters A. ISSN 03759601. 376(1213), p. 1107–1114. doi: 10.1016/j.physleta.2012.02.028.

Tellgren, Erik; Kvaal, Simen; Sagvolden, Espen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2012). Choice of basic variables in currentdensityfunctional theory. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 10502947. 86(6). doi: 10.1103/PhysRevA.86.062506. Full text in Research Archive

Jarlebring, Elias; Kvaal, Simen & Michiels, Wim (2011). Computing all Pairs (lambda, mu) Such That lambda is a Double Eigenvalue of A + mu B. SIAM Journal on Matrix Analysis and Applications. ISSN 08954798. 32, p. 902–927. doi: 10.1137/100783157. Full text in Research Archive

Kvaal, Simen (2011). Multiconfigurational timedependent Hartree method to describe particle loss due to absorbing boundary conditions. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 10502947. 84(2). doi: 10.1103/PhysRevA.84.022512.

Selstø, Sølve; Birkeland, Tore; Kvaal, Simen; Nepstad, Raymond & Førre, Morten (2011). A master equation approach to double ionization of helium. Journal of Physics B: Atomic, Molecular and Optical Physics. ISSN 09534075. 44(21). doi: 10.1088/09534075/44/21/215003.

Kvaal, Simen; Jarlebring, Elias & Michiels, Wim (2011). Computing singularities of perturbation series. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 10502947. 83(3). doi: 10.1103/PhysRevA.83.032505.

Pedersen Lohne, Magnus; Hagen, Gaute; HjorthJensen, Morten; Kvaal, Simen & Pederiva, Francesco (2011). Ab initio computation of the energies of circular quantum dots. Physical Review B. Condensed Matter and Materials Physics. ISSN 10980121. 84. doi: 10.1103/PhysRevB.84.115302. Show summary

HjorthJensen, Morten; Dean, David Jarvis; Hagen, G. & Kvaal, Simen (2010). Manybody interactions and nuclear structure. Journal of Physics G: Nuclear and Particle Physics. ISSN 09543899. 37(6). doi: 10.1088/09543899/37/6/064035.

Selstø, Sølve & Kvaal, Simen (2010). Absorbing boundary conditions for dynamical manybody quantum systems. Journal of Physics B: Atomic, Molecular and Optical Physics. ISSN 09534075. 43(6). doi: 10.1088/09534075/43/6/065004. Full text in Research Archive

Kvaal, Simen (2009). Harmonic oscillator eigenfunction expansions, quantum dots, and effective interactions. Physical Review B. Condensed Matter and Materials Physics. ISSN 10980121. 80(4). doi: 10.1103/PhysRevB.80.045321.

Kvaal, Knut; Kucheryavski, Sergei V; Halstensen, Maths; Kvaal, Simen; Flø, Andreas Svarstad & Minkkinen, Pentti [Show all 7 contributors for this article] (2008). eAMTexplorer: a software package for texture and signal characterization using Angle Measure Technique. Journal of Chemometrics. ISSN 08869383. 22(1112), p. 717–721. doi: 10.1002/cem.1160. Show summary

Kvaal, Simen (2008). Geometry of effective Hamiltonians. Physical Review C. Nuclear Physics. ISSN 05562813. 78(4). doi: 10.1103/PhysRevC.78.044330.

Kvaal, Simen; HjorthJensen, Morten & Nilsen, Halvor Møll (2007). Effective interactions, largescale diagonalization, and onedimensional quantum dots. Physical Review B. Condensed Matter and Materials Physics. ISSN 10980121. 76. doi: 10.1103/PhysRevB.76.085421. Show summary

Kvaal, Simen (2022). Tie evolution using linear combinations of gaussians.

Bodenstein, Tilmann & Kvaal, Simen (2020). A multireference coupledcluster method based on the bivariational principle.

Faulstich, Fabian Maximilian; Máté, Mihály; Laestadius, Andre; Csirik, Mihály András; Veis, Libor & Antalik, Andrej [Show all 11 contributors for this article] (2019). Mathematical and numerical aspects of the coupledcluster method tailored by tensor network states.

Faulstich, Fabian Maximilian; Máté, Mihály; Laestadius, Andre; Csirik, Mihály András; Veis, Libor & Antalik, Andrej [Show all 11 contributors for this article] (2019). Numerical and theoretical aspects of the DMRGTCC method exemplified by the nitrogen dimer.

Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2019). Guaranteed convergence of a regularized KohnSham iteration in finite dimensions. Show summary

Faulstich, Fabian Maximilian; Laestadius, Andre; Legeza, Örs; Schneider, Reinhold & Kvaal, Simen (2018). Quadratic error bounds for the coupledcluster method tailored by tensornetwork states.

Faulstich, Fabian Maximilian; Laestadius, Andre; Legeza, Örs; Schneider, Reinhold & Kvaal, Simen (2018). Mathematical analysis of the coupledcluster method tailored by tensornetwork states.

Pedersen, Thomas Bondo & Kvaal, Simen (2018). Electron Dynamics with CoupledCluster Theory.

Pedersen, Thomas Bondo & Kvaal, Simen (2018). TimeDependent CoupledCluster Theory.

Laestadius, Andre; Faulstich, Fabian Maximilian; Kvaal, Simen; Legeza, Örs & Schneider, Reinhold (2018). Analysis of The CoupledCluster Method Tailored by TensorNetwork States in Quantum Chemistry.

Laestadius, Andre; Faulstich, Fabian Maximilian; Kvaal, Simen; Legeza, Örs & Schneider, Reinhold (2018). The Study of CoupledCluster Methods Using Strong Monotonicity.

Laestadius, Andre & Kvaal, Simen (2018). ANALYSIS OF THE EXTENDED COUPLEDCLUSTER METHOD IN QUANTUM CHEMISTRY.

Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2018). Generalized KohnSham iteration on Banach Spaces.

Tellgren, Erik; Lange, Kai Kaarvann; Sagvolden, Espen; Kvaal, Simen; Austad, Jon & Reimann, Sarah [Show all 9 contributors for this article] (2018). Quantum chemistry for strong magnetic fields.

Faulstich, Fabian Maximilian; Laestadius, Andre; Legeza, Örs; Schneider, Reinhold & Kvaal, Simen (2017). Mathematical aspects of the coupledcluster method tailored by tensornetwork states in quantum chemistry.

Laestadius, Andre & Kvaal, Simen (2016). Analysis of the Extended CoupledCluster Method.

Kvaal, Simen & Laestadius, Andre (2016). The extended coupledcluster method and its rigorous analysis.

Tellgren, Erik; Teale, Andrew Michael; Ekström, Ulf Egil; Kvaal, Simen; Sagvolden, Espen & Helgaker, Trygve (2015). Current density functional theory for molecular systems in strong magnetic fields.

Kvaal, Simen (2014). Bivariational approximations & the orbitaladaptive coupledcluster method.

Helgaker, Trygve; Borgoo, Alex; Ekström, Ulf Egil; Furness, James; Hoffmann, Mark & Kvaal, Simen [Show all 12 contributors for this article] (2014). DensityFunctional Theory in Magnetic Fields.

Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andy (2014). Differentiable but Exact Formulation of DensityFunctional Theory.

Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andrew Michael (2014). Differentiable but Exact Formulation of DensityFunctional Theory.

Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael; Ekström, Ulf Egil; Jørgensen, Poul & Olsen, Jeppe (2014). Differentiable but Exact Formulation of DensityFunctional Theory.

Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael & Ekström, Ulf Egil (2014). Differentiable but Exact Formulation of DensityFunctional Theory.

Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2013). Building blocks of Current Density Functional Theory.

Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2013). Building blocks of Current Density Functional Theory.

Ekström, Ulf Egil; Kvaal, Simen; Borgoo, Alex; Helgaker, Trygve; Sagvolden, Espen & Tellgren, Erik (2013). MoreauYosida regularization of DFT.

Kvaal, Simen (2013). Abels Tårn. [Radio]. NRK P2.

Kvaal, Simen; Ekström, Ulf Egil; Tellgren, Erik; Borgoo, Alex; Helgaker, Trygve & Sagvolden, Espen (2013). MoreauYosida regularization of DFT.

Kvaal, Simen (2013). Ab initio dynamics using the coupled cluster method.

Selstø, Sølve; Kvaal, Simen; Birkeland, Tore; Nepstad, Raymond & Førre, Morten (2012). Double ionization with absorbers. EurophysicsNews. ISSN 05317479. 43(1), p. 15–16.

Kvaal, Simen; Jarlebring, Elias & Michiels, Wim (2010). A numerical method for computing the radius of convergence of Rayleigh Schroedinger Perturbation theory without the need for the terms in the series.

Kvaal, Simen (2010). Timedependent coupledcluster approach to manybody quantum dynamics.

Kvaal, Simen (2010). Timedependent Coupled Cluster for ManyBody Quantum Dynamics.

Kvaal, Simen (2010). Variational Principles for CoupledCluster Methods.

Kvaal, Simen (2010). Adaptive timedependent coupled cluster method for wavepacket propagation of manyfermion systems.

Selstø, Sølve & Kvaal, Simen (2010). Absorbing boundary conditions for dynamical manyparticles systems.

Selstø, Sølve; Førre, Morten; Kvaal, Simen; Nepstad, Raymond & Birkeland, Tore (2010). Describing double photoionization of helium bymeans of absorbing boundaries.

Selstø, Sølve; Kvaal, Simen; Nepstad, Raymond & Førre, Morten (2010). Nonsequential double ionization of helium: Extracting the cross section.

Selstø, Sølve & Kvaal, Simen (2010). Absorbing boundaries for more than one particle.

Kvaal, Simen (2009). Usynlig Verden.

Kvaal, Simen (2009). Rigorous analysis of ab initio calculations for parabolic quantum dots. Full text in Research Archive

HjorthJensen, Morten & Kvaal, Simen (2009). Effective interactions and convergence criteria for configuration interaction methods.

Kvaal, Simen & Halvorsen, Tore Gunnar (2009). One gauge to rule them all  Gaugeinvariant grid discretizations.

HjorthJensen, Morten & Kvaal, Simen (2007). Similarity Transformations, Flow Equations and ManyBody Perturbation Theory: Role of ManyBody Forces.

Hansen, Audun Skau; Pedersen, Thomas Bondo; Helgaker, Trygve & Kvaal, Simen (2021). Local correlation methods for infinite systems. Universitetet i Oslo, Det matematisknaturvitenskapelige fakultet. ISSN 15017710. 2021(2380). Full text in Research Archive

Bore, Sigbjørn Løland; Cascella, Michele & Kvaal, Simen (2020). Advances in the Hybrid ParticleField Approach: Towards Biological Systems. Matematisk Naturvitenskapelig fakultet, Universitetet i Oslo. ISSN 15017710. 2020(2245). Show summary

Halvorsen, Tore Gunnar & Kvaal, Simen (2009). Manifestly gauge invariant discretizations of the Schrödinger equation. http://arxiv.org.

Jarlebring, Elias; Kvaal, Simen & Michiels, Wim (2009). Computing all pairs (lambda,mu) such that lambda is a double eigenvalue of A + mu B. Katholieke Universiteit Leuven. Full text in Research Archive Show summary

Kvaal, Simen (2009). Analysis of manybody methods for quantum dots. Det matematisk naturvitenskapelige fakultet.