Simen Kvaal
My background is from physics and applied mathematics, and in 2012 I moved to quantum chemistry. My main interests are analysis and development of computational methods for nonrelativistic systems.
I am currently a researcher on Trygve Helgaker's ERC advanced grant ABACUS, where I study formal aspects of densityfunctional theory. In particular, I study currentdensity functional theory for molecules in external magnetic fields.
Late 2014, I was awarded an ERC starting grant. The project BIVAQUM dives into the very fundamentals of quantum theory via the socalled bivariational principle. This is a generalization of the standard variational principle that is the foundation for almost every computational scheme for quantum mechanics, and represents a highly unconventional approach, yet it has great potential. The bivariational principle opens up completely new ways of deriving and analyzing methods. In particular, coupledcluster theory (single and multireference) may be approached in new ways using the bivariational approach.
BIVAQUM has its own web site, see www.bivaqum.no.
Publications

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

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, p. 1421–1425. doi: 10.1021/acs.jpclett.0c03422.

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

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

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

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; 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.

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; 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.

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.

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.

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

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

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 (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.

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; 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.

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

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.

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

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; 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

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). Numerical and theoretical aspects of the DMRGTCC method exemplified by the nitrogen dimer.

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.

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

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.

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

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

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

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.

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

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.

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 (2014). Differentiable but Exact Formulation of DensityFunctional Theory.

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

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

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

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.

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.

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

Kvaal, Simen (2009). Usynlig Verden.

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.

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.