From Stavanger towards
the Big Bang

Research on the dynamics of strongly
correlated quantum systems

About me

Professional

I am a full professor in physics at the Faculty of Science and Technology at the University of Stavanger. My research area is theoretical high energy nuclear physics with a focus on real-time dynamics from lattice QCD. Broadly speaking, I am working on devising a thermometer for the relativistic-heavy-ion collisions carried out at the LHC, RHIC and upcoming FAIR facility via a better understanding of the bound states of heavy quarks, so called heavy quarkonium.

In December 2018 I have been awarded a highly competitive Young Research Talent grants from the Norwegian Research Council for my project proposal "DeepRTP - deep learning the real-time properties of strongly correlated quantum fields" and previously received the Nuclear Physics A Young Scientists Award at the XXV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2015) in Kobe, Japan.

As of 2022 I am member of the Young Academy of Norway and vice-chair of the JSPS Norway-Japan academic network. As the Stavanger city coordinator for Pint of Science Norway and together with enthusiastic volunteers I have recently organized the first in-person installment of the festival between May 9-11 2022. For the organization of two major physics conferences, vConf21 and ConfXV, I was selected as ambassador of the Stavanger region.

Personal

With family ties to South Korea and having obtained my doctorate at The University of Tokyo in Japan, East Asia is on my radar. When time permits I enjoy listening to recorder music of the baroque and renaissance era as well as the occasional electronica.

Select Research Highlights
2024
Exact symmetry conservation and automatic mesh refinement for initial boundary value problems
In this ground-breaking study, together with colleagues from Sweden (Jan Nordström) and from South Africa (Will Horowitz), we construct a novel action for classical scalar field theory, in which coordinate maps enter as dynamical degrees of freedom. Our approach is inspired by the world-line formalism of the general theory of relativity and offers three central advantages: space-time coordinates as dependent quantities remain continuous after discretization of the action and a discrete Noether theorem holds. In addition, the coordinate maps adapt dynamically to the fields leading to automatic mesh refinement guided by the symmetries of the system. Third, the presence of dynamical coordinate maps offers new freedom in constructing boundary conditions. We demonstrate the efficacy of the approach based on 1+1d wave propagation.
A non-hermitean momentum operator for the particle in a box
This study investigates a seemingly routine question in quantum mechanics, the particle in the box and how to represent its momentum. Despite being a topic discussed superficially in introductory quantum mechanics classes, this question remains unsolved to this day and is the focus of several international research groups. Together with Seyong Kim from Sejong University in South Korea we construct a novel candidate momentum operator, which offers advantages over operators previously discussed in the literature. This paper represents the outcome of a Korea - Nordic Research and Development Networking grant by the National Research Foundation of South Korea.
2023
Machine learning assisted real-time simulations of quantum dynamics
This ground-breaking study presents the final achievement of the DeepRTP project, a machine-learning strategy inspired by reinforcement learning, which amends complex Langevin real-time simulations by system specific prior knowledge, in order to tackle the sign problem. Together with PhD student Daniel Alvestad and collaborator Denes Sexty we demonstrate that our approach is able to significantly extend the range of validity of complex Langevin real-time simulations in thermal scalar field theory in 1+1 dimensions, beating long-standing record in the literature.
A novel geometric discretization of IVPs retaining continuum space-time symmetries
Continuing a fruitful collaboration with Jan Nordström at Linköping University I develop a novel discretization prescription for initial value problems retaining continuum space-time symmetries. Taking insight from the theory of general relativity, where space and time are treated on the same footing, a novel geometric variational discretization for second order initial value problems is developed. By discretizing the dynamics along a world-line parameter, instead of physical time directly, one retains manifest translation symmetry and conservation of the associated continuum Noether charge. A non-equidistant time discretization emerges dynamically, realizing a form of automatic adaptive mesh refinement (AMR), guided by the system symmetries. Using appropriately regularized summation by parts finite difference operators, the continuum Noether charge, defined via the Killing vector associated with translation symmetry, is shown to be exactly preserved in the interior of the simulated time interval.
2022
A novel strategy to attack the sign-problem
As part of my DeepRTP project and together with PhD student Daniel Alvestad and postdoc Rasmus Larsen we have developed a novel machine-learning based strategy to attack the sign problem in the context of Complex Langevin simulations. It marries the concept of kernelled Langevin, a non-neutral modification of the underlying stochastic process with an optimization algorithm that can guide the complex Langevin process towards correct convergence. Using a simple field independent kernel, we manage to extend the region of correct convergence in real-time by a factor three compared to the previous benchmark in the literature. An interesting connection between complex Langevin and Lefschetz thimbles is discussed.
A new discretization technique for initial value problems based on a variational principle
Together with my colleague Jan Nordström at Linköping University I developed a novel and highly versatile discretization strategy for initial value problems (IVPs), which is motivated by the fact that both the classical and quantum description of nature rest on causality and a variational principle. It is based on an optimization functional with doubled degrees of freedom, which is discretized using a single regularized summation-by-parts (SBP) operator. The variational principle provides a straight forward recipe to formulate the corresponding optimization functional for a large class of differential equations. The novel regularization we develop here is inspired by the weak imposition of initial data, often deployed in the modern treatment of IVPs and is implemented using affine coordinates. We demonstrate numerically the stability, accuracy and convergence properties of our approach in systems with classical equations of motion featuring both first and second order derivatives in time.
A puzzling study of the in-medium heavy quark potential from HISQ lattices
Together with our postdoc Rasmus Larsen, PhD student Gaurang Parker and colleagues from the HotQCD collaboration, we explore the complex potential acting between static color sources in the presence of a hot thermal medium. Using lattice QCD simulations by the HotQCD collaboration, based on the the Highly Improved Staggered Quark action, we compute Wilson line correlators in Coulomb gauge and extract their spectral representation using four different and complementary methods, Gaussian fits, Bala-Datta fits, the Pade- and Bayesian reconstruction. We find no indication that the real part of the potential changes with temperature, contrary to all prior results in the literature. The presence of positivity violation in the spectral functions due to the HISQ action is among the challenges encountered in the study. We are therefore exploring in follow up work finer discretizations and possibly different actions to shed light on this unexpected behavior.
Manuscript: Open access PDF
2021
First implementation of Complex Langevin with implicit solvers
This study explores the potential of modern implicit solvers for stochastic partial differential equations in the simulation of real-time complex Langevin dynamics. Not only do these methods offer inherent stability, rendering the issue of runaway solution moot, but they also allow us to simulate at comparatively large Langevin time steps, leading to lower computational cost. We compare different ways of regularizing the underlying path integral and estimate the errors introduced due to the finite Langevin time steps. Based on that insight, we implement benchmark (non-)thermal simulations of the quantum anharmonic oscillator on the canonical Schwinger-Keldysh contour of short real-time extent.
Manuscript: Open access PDF
First consistent implementation of lattice gauge theory for finite systems with non-trivial boundary conditions.
In this study I develop a novel action for lattice gauge theory for finite systems, which accommodates non-periodic boundary conditions, implements the proper integral form of Gauss’ law and exhibits an inherently symmetric energy momentum tensor, all while realizing automatic O(a) improvement. Taking the modern summation-by-parts formulation for finite differences as starting point and combining it with insight from the finite volume strategies of computational electrodynamics I show how the concept of a conserving discretization can be realized for non-Abelian lattice gauge theory. Major steps in the derivation are illustrated using Abelian gauge theory as example.
Manuscript: Open access PDF
2020
First numerical determination of the binding potential between static quarks in classical statistical lattice gauge theory
We compute the proper real-time interaction potential between a static quark and antiquark in classical lattice gauge theory at finite temperature. Our central result is the determination of the screened real-part of this potential, and we reconfirm the presence of an imaginary part. The real part is intimately related to the back-reaction of the static sources onto the gauge fields, incorporated via Gauss’s law. Differences in the treatment of static sources in quantum and classical lattice gauge theory are discussed. The simulation code used in this study is available under open access at the Zenodo repository.
Manuscript: Open access PDF, Source Code: Zenodo repository link
A novel finite difference operator for accurate real-time quantum dynamics
We develop a novel numerical scheme for the simulation of dissipative quantum dynamics, following from two-body Lindblad master equations. It exactly preserves the trace of the density matrix and shows only mild deviations from hermiticity and positivity, which are the defining properties of the continuum Lindblad dynamics. The central ingredient is a new spatial difference operator, which not only fulfills the summation by parts (SBP) property, but also implements a continuum reparametrization property. Using the time evolution of a heavy-quark anti-quark bound state in a hot thermal medium as an explicit example, we show how the reparametrization neutral summation-by-parts (RN-SBP) operator enables an accurate simulation of the full dissipative dynamics of this open quantum system. The simulation code used in this study is available under open access at the Zenodo repository.
Manuscript: Open access PDF, Source Code: Zenodo repository link
Discovery of a flaw in the state-of-the-art implementation of the Maximum Entropy Method
The Maximum Entropy Method (MEM) is a popular data analysis technique based on Bayesian inference, which has found various applications in the research literature. While the MEM itself is well-grounded in statistics, I argue that its state-of-the-art implementation, suggested originally by Bryan, artificially restricts its solution space. This restriction leads to a systematic error often unaccounted for in contemporary MEM studies. The goal of this paper is to carefully revisit Bryan’s train of thought, point out its flaw in applying linear algebra arguments to an inherently nonlinear problem, and suggest possible ways to overcome it.
Manuscript: Open access PDF
A study on extracting dynamical properties of quantum systems via Deep Neural Networks
We explore artificial neural networks as a tool for the reconstruction of spectral functions from imaginary time Green’s functions, a classic ill-conditioned inverse problem. Our ansatz is based on a supervised learning framework in which prior knowledge is encoded in the training data and the inverse transformation manifold is explicitly parametrized through a neural network. We systematically investigate this novel reconstruction approach, providing a detailed analysis of its performance on physically motivated mock data, and compare it to established methods of Bayesian inference. The reconstruction accuracy is found to be at least comparable and potentially superior in particular at larger noise levels. We argue that the use of labeled training data in a supervised setting and the freedom in defining an optimization objective are inherent advantages of the present approach and may lead to significant improvements over state-of-the-art methods in the future. Potential directions for further research are discussed in detail.
Manuscript: Open access PDF
2019
First fully quantum and potential based real-time simulation of heavy quarkonium
In this paper we study the real-time evolution of heavy quarkonium in the quark-gluon plasma (QGP) on the basis of the open quantum systems approach. In particular, we shed light on how quantum dissipation affects the dynamics of the relative motion of the quarkonium state over time. To this end we present a novel nonequilibrium master equation for the relative motion of quarkonium in a medium, starting from Lindblad operators derived systematically from quantum field theory. In order to implement the corresponding dynamics, we deploy the well established quantum state diffusion method. In turn we reveal how the full quantum evolution can be cast in the form of a stochastic nonlinear Schrödinger equation. This for the first time provides a direct link from quantum chromodynamics to phenomenological models based on nonlinear Schrödinger equations. Proof of principle simulations in one dimension show that dissipative effects indeed allow the relative motion of the constituent quarks in a quarkonium at rest to thermalize. Dissipation turns out to be relevant already at early times well within the QGP lifetime in relativistic heavy ion collisions.
Manuscript: Open access PDF
Review on quarkonium in extreme conditions
In this report I review recent progress achieved in the understanding of heavy quarkonium under extreme conditions from a theory perspective. Its focus lies both on quarkonium properties in thermal equilibrium, as well as recent developments towards a genuine real-time description, valid also out-of-equilibrium. We will give an overview of the theory tools developed and deployed over the last decade, including effective field theories, lattice field theory simulations, modern methods for spectral reconstructions and the open quantum systems paradigm. The report will discuss in detail the concept of quarkonium melting, providing the reader with a contemporary perspective. In order to judge where future progress is needed we will also discuss recent results from experiments and phenomenological modeling of quarkonium in relativistic heavy-ion collisions.
Manuscript: Open access PDF
A study of parton distribution functions using Bayesian inference and Neural Networks
The computation of the parton distribution functions (PDF) or distribution amplitudes (DA) of hadrons from first principles lattice QCD constitutes a central open problem in high energy nuclear physics. In this study, we present and evaluate the efficiency of several numerical methods, well established in the study of inverse problems, to reconstruct the full x-dependence of PDFs. Our starting point are the so called Ioffe time PDFs, which are accessible from Euclidean time simulations in conjunction with a matching procedure. Using realistic mock data tests, we find that the ill-posed incomplete Fourier transform underlying the reconstruction requires careful regularization, for which both the Bayesian approach as well as neural networks are efficient and flexible choices.
Manuscript: Open access PDF
pre 2019
In medium heavy-quark potential from lattice QCD
In arXiv:1607.04049 (Phys.Rev. D95 (2017) 054511) we improve and extend our study of the complex in-medium heavy quark potential and its Debye mass mD in a gluonic medium with a finer scan around the deconfinement transition and newly generated ensembles closer to the thermodynamic limit. On the lattices with larger physical volume, Re[V] shows signs of screening, i.e. a finite mD, only in the deconfined phase, reminiscent of a genuine phase transition. Consistently Im[V] exhibits nonzero values also only above T_C.

Downloads for quenched QCD (β=6.1,ξ=3.2108,323×Nτ)
Re[V] datasets [TXT], Im[V] datasets [TXT]

In arXiv:1410.2546 (Phys.Rev.Lett. 114 (2015) 8, 082001) we presented a state-of-the-art determination of the complex valued static quark-antiquark potential at phenomenologically relevant temperatures around the deconfinement phase transition. Its values were obtained from non-perturbative lattice QCD simulations using spectral functions extracted via a novel Bayesian inference prescription. Among our finding were that the real part, both in a gluonic medium as well as in realistic QCD with light u,d and s quarks, lies close to the color singlet free energies in Coulomb gauge and shows Debye screening above the (pseudo) critical temperature T_C.

Downloads for quenched QCD (anisotropic Wilson action)
Re[V] datasets [GZIP], Im[V] datasets [GZIP]
and F1 datasets [GZIP], as well as the raw
Polyakov Loop correlators [GZIP]

as shown in arXiv:1410.2546 (Phys.Rev.Lett. 114 (2015) 8, 082001) and used in arXiv:1506.08684 (Phys.Lett.B 753 (2016) 232)

Downloads for Nf=2+1 flavor QCD (asqtad action, HotQCD)
Re[V] datasets [GZIP] and F1 datasets [GZIP], as well as the raw Polyakov Loop correlators [GZIP]

as shown in arXiv:1410.2546 (Phys.Rev.Lett. 114 (2015) 8, 082001) and used in arXiv:1509.07366 (JHEP volume 2015, pages 1–34 (2015))
Quantum Particles and Fields on the Lattice
Many exciting and challenging questions remain open in contemporary theoretical physics. Two examples are the origin and underlying processes of high temperature superconductivity and the material properties of nuclear matter under conditions close to the Big Bang or in the interior of dense astrophysical objects, such as neutron stars. Both lines of inquiry relate to quantum systems, which exhibit strong correlations and in turn defy a treatment with the otherwise well-established methods of perturbation theory or other approximate techniques, such as mean-field theory. It is in these strongly correlated quantum systems that numerical simulations by means of lattice regularized field theory have made important contributions. In this lecture we set out to explore the basics of lattice field theory both from a theoretical and practical side, preparing you for and supporting you in your own independent research in the field. In order to access such an advanced topic we will start from a recap of statistical physics and spin models, continue by considering the simulation of few-body quantum systems and classical field theory, before embarking on the path towards understanding quantum field theory in the lattice regularization.
Learning Outcomes
  • I feel confident to discuss central concepts of statistical physics using a simple spin model.
  • I easily recall challenges in discretising common partial differential equations arising in physics.
  • I have a basic theoretical and practical understanding of Monte-Carlo methods to evaluate highly dimensional integrals.
  • I see no difficulty in explaining the basic concepts of lattice regularised field theory using scalar fields as an example.
  • I have a basic understanding of the concept of renormalization and am aware of its application in lattice field theory and spin models.
  • I have gained a first look into the structure and principles underlying lattice gauge theory as well as fermions on the lattice.
  • I feel excited and empowered to study real-world problems that I encounter in my master or PhD thesis work using lattice field theory methods.
    • Bayesian Methods ( lecture at the 2023 DPG EFT & Lattice School)
    Bayesian Methods, the application of Bayesian statstics to the task of inferring the properties of unobserved quantities from observed data are central to gaining insight in modern physics. In this lecture I give an elementary introduction to the subject of Bayesian inference and prediction with an emphasis on uncertainty quantification from model uncertatinties. A concrete example of Bayesian inference in the context of the strong-interactions is provided via the reconstruction of spectral functions from lattice QCD simulations.
    Learning Outcomes
  • I know several examples of recent EFT and lattice QCD research, benefitting from Bayesian methods.
  • I acquainted myself with the basics of constructing likelihood- and prior probabilities to set up Bayes theorem in simple systems.
  • I gained a first, both conceptual and computational, insight into evaluating posteriors either as point estimates or via full Monte-Carlo simulations.
  • I can investigate the predictive accuracy of simple models of different expressiveness using information criteria.
  • I have gained first hand conceptual and computational experience in using Monte-Carlo Bayesian inference to reconstruct QCD spectral functions.
  • I feel confident to continue deepening my knowledge on Bayesian methods via the literature and look forward to identifying applications of Bayesian methods in real-world problems in my master or PhD thesis.
    • Thermal Field Theory (block course at the 47th Graduate Days)
    Thermal field theory lies at the heart of many phenomena studied in frontier experiments, ranging from the production of the quark-gluon plasma in relativistic heavy-ion collisions to understanding the phases in ultracold quantum gases and the design of materials capable of high-temperature superconductivity. Field theory in thermal equilibrium, while being an idealized concept, offers valuable insight into phenomenologically relevant static properties of quantum systems, as well as their real-time dynamics, all affected by the presence of the heat bath environment. Last but not least it provides the base-line from which to embark on the study and characterization of out-of-equilibrium phenomena.

    Thermal fluctuations are not only able to generate macroscopic pressure in a quantum system but may lead to a characteristic modification of the carriers of interactions, endowing them with a thermal mass, referred to as Debye or screening mass. In this lecture we will explore the basics of thermal field theory, working our way from scalar fields to gauge theory, exploring how to theoretically implement the effects of thermal fluctuations and how to concretely compute relevant system properties with analytic and numeric methods.
    Learning Outcomes
  • I can identify different research fields in which thermal field theory is of relevance.
  • I gained a first, both conceptual and computational, insight into thermal field theory formulated in terms of Path Integrals in Euclidean time.
  • I can connect my knowledge of vacuum Feynman diagrams to the finite temnperature setting and feel confident to compute the pressure of scalar field theory to lowest order in the coupling.
  • I have gained a first look at Monte-Carlo methods used to evaluate highly dimensional integrals.
  • I acquainted myself with the state-of-the-art strategy to compute the pressure from lattice QCD simulations using original literature [link to Nucl.Phys.B 205 4 545 (1982)].
  • I feel confident to continue studies in thermal field theory and look forward to identifying real-world problems in my master or PhD thesis that can benefit from this formalism.
    • Lattice Effective Field Theory Methods for In-Medium Heavy Quarkonium
    These summer school lectures intend to introduce students to two effective field theories NRQCD and pNRQCD used in current research on in-medium heavy quarkonium. One of the four lectures contains an in-depth description of the Bayesian approach to spectral function reconstruction that is central to understanding in-medium modification of hadrons.
    Lecture Notes
  • Lecture 1: Introduction [PDF]
  • Lecture 2: NRQCD [PDF]
  • Lecture 3: Bayesian Spectral Reconstructions [PDF]
  • Lecture 4: pNRQCD - Schrödinger Equation [PDF]
    • Teaching
    Code

    The Bayesian Reconstruction (BR) Method
    This software implements the Bayesian reconstruction (BR) method for the Bayesian inference of spectral functions from Euclidean correlation functions. The underlying method, including the explcit form of the regulator functional and the procedure for marginalization of the hyperparameter alpha is described in the publication ( Y. Burnier and A. Rothkopf, "Bayesian Approach to Spectral Function Reconstruction for Euclidean Quantum Field Theories" arXiv:1307.6106, Phys. Rev. Lett. 111, 182003 (2013) ). The code is written using arbitrary precision arithmetic to allow exploration of reconstruction problems with exponential kernels and is not limited in these cases to positive frequencies. The GMP and MPFR libraries are required for compilation. In addition the code also implements the extended Maximum Entropy Method discussed in detail in (A. Rothkopf, "Improved Maximum Entropy Analysis with an Extended Search Space", arXiv:1110.6285, J.Comput.Phys. 238 (2013) 106-114 ) which overcomes the artificial limitation of the search space in Bryan's MEM approach ( for a detailed discussion see A. Rothkopf, Bryan's Maximum Entropy Method -- diagnosis of a flawed argument and its remedy arXiv:2002.09865, Data 2020, 5(3), 85 ).
    Open access source code: Link
    Classical statistical SU(3) gauge theory in the presence of sources
    This software implements the classical statistical simulation of SU(3) Yang-Mills theory in (classical) thermal equilibrium in (3+1)d, based on the naive Wilson plaquette action. Formulated as Hamiltonian equations of motion in temporal gauge, the time evolution is implemented via the symplectic leap-frog scheme. Distribution of the computation among different computing nodes relies on the PETSC library (tested on v.3.14).
    Open access source code: Link
    1d High Temperature Quarkonium Lindblad Dynamics Solver
    This program implements a 1d version of the master equation for heavy quarkonium derived in arXiv:1403.5783 on the level of the density matrix and includes full dissipative effects. The code deploys a novel discrete finite difference operator, specifically designed to guarantee the trace conservation of the Lindblad dynamics called a reparametrization neutral summation-by-parts operator. Its derivation is outlined in arXiv:2004.04406.
    Open access source code: Link
    Solver for 2PI evolution equations at NLO in large N
    This program implements the thrre-dimensional 2PI quantum equations of motion of the nonlinear quark meson model in real-time, including both scalar fermion dynamics in the presence of a scalar field expectation value. (code developed together with Linda Shen)
    Source code: Link
    aEFT: A Langevin-type effective theory with chiral fermions on the lattice
    This code implements the classical statistical evolution of gauge fields in the presence of chiral fermions via an effective field theory prescription deployed in arXiv:1512.02374. In addition it determines the topological charge of the system over time using standard techniques of gauge cooling.
    Source code: Download, Run Script
    ExtMEM: Maximum Entropy Method with extended search space
    The standard implementation of the Maximum Entropy Method (MEM) follows Bryan and deploys a Singular Value Decomposition (SVD) to limit the dimensionality of the underlying solution space apriori. In arXiv:1110.6285 (J.Comput.Phys. 238 (2013) 106-114) we have presented arguments based on the shape of the SVD basis functions and numerical evidence from a mock data analysis, which show that the correct Bayesian solution is not in general recovered with this approach. As a remedy we propose to extend the search basis systematically, which will eventually recover the full solution space and the correct solution. In order to adequately approach problems where an exponentially damped kernel is used, we provide an open-source implementation, using the C/C++ language that utilizes high precision arithmetic adjustable at run-time. The LBFGS algorithm is included in the code in order to attack problems without the need to resort to a particular search space restriction.
    2024
    1st CERN-Nordic summer school: Continuum Foundations of Lattice Gauge Theories (July 22nd-26th 2024)
    This school aims to strengthen the interface between continuum methods and lattice quantum field theory (QFT). The mathematical foundations of four topics frequently appearing at the forefront of current lattice QFT research will be explored in a 6-hour couse. We welcome speakers on: Modern use of unitarity constraints for phenomenology (Gilberto Colangelo - Bern), Inverse problems and their applications to the lattice (Luigi Del Debbio - Edinburgh), Foundations of quantum computing (Zohreh Davoudi - Maryland), as well as on Resurgence and the need for non-perturbative methods (Gerald Dunne - Connecticut).
    These lectures will provide the participants with a deeper understanding of the underpinning concepts and will create opportunities for interdisciplinarity between lattice practitioners and specialists in these related fields. (Organized together with Justus Tobias Tsang (CERN), Michele Della Morte (SDU), Matteo Di Carlo (CERN), Felix Erben (CERN), Andreas Jüttner (CERN/Southampton) and Simon Kuberski (CERN) ).
    Homepage: Link
    INT Workshop: Inverse problems and Uncertainty quantification (July 8th-12th 2024)
    Realizing the full potential of experimental and observational studies of nuclear matter requires a comprehensive understanding of the dynamics of its microscopic constituents, within the theory of quantum chromodynamics (QCD). Nuclear physics affects matter on scales that span neutron stars to the collision centers of a heavy-ion collision. Consequently a large variety of techniques has been developed to study these systems including lattice QCD, effective field theory, and data-driven phenomenology.
    This workshop will bring together practitioners working on inference problems in fields across theoretical nuclear physics and astrophysics to address new developments in, and approaches to, tackling inverse problems and uncertainty quantification in fields across theoretical nuclear physics and astrophysics. Collectively, these topics are crucial to extract reliable information on fundamental properties of strong interactions and nuclear matter from experimental and observational data. This, in turn, is key to reliable predictions for nuclear systems ranging from quarks and gluons to neutron-rich nuclei, neutron stars, and beyond-the-standard-model physics like neutrinoless double-beta decay. (Organized together with Martha Constantinou, Christopher Monahan and Ingo Tews)
    Homepage: Link
    2022
    The XIVth Quark confinement and the Hadron spectrum conference (August 1st - 6th, 2022)
    Inaugurated in 1994 in Como, Italy, this series of conferences has become an important forum for scientists working on strong interactions, stimulating exchanges among theorists and experimentalists as well as across related fields.
    The aim of the conference is to bring together people working on strong interactions from different approaches, ranging from lattice QCD to perturbative QCD, from models of the QCD vacuum to QCD phenomenology and experiments, from effective theories to physics beyond the Standard Model.
    The scope of the conference also includes the interface between QCD, nuclear physics and astrophysics, and the wider landscape of strongly coupled physics. In particular, the conference will focus on the fruitful interactions and mutual benefits between QCD and the physics of condensed matter and strongly correlated systems.
    The fifteenth edition of this conference series is jointly hosted by the University of Stavanger and the Academy of Science Stavanger. The event takes place at the Ullandhaug Campus of the University of Stavanger, Norway, August 1st - 6th, 2022.
    (Chair, organized together with Nora Brambilla, designed the website)
    Homepage: Link
    XQCD 2022 and PhD School (July 22nd-29th 2022)
    The 18th International Conference on QCD in Extreme Conditions (XQCD 2022), organized by The Norwegian University of Science and Technology in Trondheim, Norway, from July 27-29 2022. XQCD is part of a series of international workshop-style conferences, held annually, which aims at covering recent advances in the theory and phenomenology of QCD under extreme conditions of temperature and/or baryon density, together with related topics.
    The XCQD2022 PhD school was held at the University of Stavanger from July 22 to July 25 2022, right before the XQCD 2022 conference. The school featured block lectures 6 x 45min on four research areas, which are central elements of the studies presented at the XQCD conference, providing an in-depth review of these fields for PhD students.
    (Organized togehter with Jens Oluf Andersen; co-chair of XQCD, chair of PhD school)
    Homepage XQCD: Link
    Homepage XQCD PhD school: Link
    2021
    ECT* Workshop: Tackling the real-time challenge in strongly correlated systems (September 13th-17th 2021)
    Experiments at the forefront of physics elucidate the real-time properties of strongly correlated quantum systems from the transport of quarks and gluons in a Quark-Gluon Plasma created in a heavy-ion collision to the conduction of electrons in a highly complex functional material. While simulations of Euclidean path integrals already provide unprecedented non-perturbative insight into the static properties of strongly correlated systems, access to real-time properties in the form of spectral information is still severely limited. Over the past decade the field has however witnessed significant progress in tackling this real-time challenge based on both conceptual developments, as well as improved data analysis strategies involving probabilistic reasoning. It is the goal of this workshop to bring together experts from different fields of physics, to discuss and explore synergies among these recently developed methods and chart a path towards robust determination of spectral real-time information from Euclidean path integrals. (Organized together with Anthony Francis and Sinead Ryan)
    Homepage: Link
    YouTube Playlist: Link
    A virtual tribute to Quark Confinement and the Hadron Spectrum (August 2nd-6th 2021)
    With the Corona pandemic far from over and the prospect for a return to a perceived normal only at the end of 2021, the organizers of the 14th Quark Confinement and Hadron Spectrum conference have decided to postpone the in-person conference in Stavanger, Norway between August 1st - 6th, 2022 (for updates see the ConfXIV website).
    At the same time the community is weathering the storm and those of us who are privileged enough can uphold their research activities. To keep the momentum of the community alive and to further exchange among practitioners in the field amidst limited options for travel, we thus invite you to join our virtual event from August 2nd-6th 2021. In the spirit of the QCHS conference series it will feature plenary talks, roundtable discussion and parallel contributed talks. Its schedule will consist of a program of reduced length of 4 hours each day, staggered from day to day, in order to accommodate a global audience. (Chair, organized together with Nora Brambilla, designed the website)
    Homepage: Link
    The 2021 biennial meeting of the Norwegian Physical Society (June 21st-24th 2021)
    The "Fysikermøte" is the central biennial meeting of the Norwegian Physical Society, attended by physicists working in academia, industry and secondary education in Norway. This year it takes place at the University of Stavanger between June 21st-24th 2021. The program consists of plenary presentations showcasing the latest in physics in Norway, as well as parallel sessions for the various topical subgroups represented in the society. We are thrilled to welcome a diverse group of researchers for a dedicated outreach program on the Science of Energy on June 23rd. (Organized together with Anders Tranberg, designed the website)
    Homepage: Link
    Muon g-2 in the precision era (April 22nd)
    The unveiling of updated g-2 measurements by Fermilab in 2021 has intensified the interest in this exciting area of precision physics among many physicists. To provide a sober assessment of the impact of these new measurements, we are organizing a virtual NPACT seminar at the University of Stavanger on Thursday April 22nd from 11:00h – 14:15h. The seminar will feature four key speakers: one colleague who is member of the Fermilab muon g-2 collaboration (Prof. Martin Fertl), one colleague working in data-driven approaches to the muon g-2 (Prof. Gilberto Colangelo), one colleague from the lattice QCD community working on the muon g-2 (Dr. Bálint Tóth) and one colleague from the BSM community (Prof. Andreas Crivellin).
    This topical seminar welcomes physicist from all research areas, i.e. not necessarily from particle or nuclear physics. To accommodate such an audience we have allotted 40 minutes to each of the presentations. A 30 minutes panel discussion is scheduled at the end of the seminar, which allows discussions among practitioners and experts in the field. (Sole organizer)
    Homepage: Link
    2020
    ACFI Workshop: QCD Real-Time Dynamics and Inverse Problems (October 19th-22nd 2020)
    Realizing the full potential of experimental studies of nuclear matter requires a comprehensive understanding of the dynamics of its microscopic constituents, within the theory of quantum chromodynamics (QCD). Lattice QCD calculations have made significant contributions to our understanding of the strong interaction, but little is known from ab initio calculations about the dynamical properties of quarks and gluons. A central challenge for such calculations is the need to solve ill-posed inverse problems. This workshop will bring together practitioners in the field of lattice QCD and other communities working with inverse problems to address recent progress and remaining challenges in the extraction of dynamical properties from both numerical calculations and from experiment. (Organized together with Martha Constantinou and Christopher Monahan)
    Homepage: Link
    Conferences & Wokshops
    Networking
    The Young Academy of Norway (ACN)
    The Young Academy of Norway is an interdisciplinary organization for young researchers dedicated to research policy and dissemination. The members of the academy are hightly active and visible in sceince communication and are vital contributors to the national conversation on early researcher's careers. A new member as of 2022, I am looking forward to working together with excellent colleagues at the Academy to both further strengthen science communication in Norway and to communicate the value of science and research to decision-makers. (photo: David Jensen)
    Academy homepage: Link
    The JSPS Alumni Club Norway (ACN)
    The JSPS Alumni Club in Norway (ACN) was established in 2019 in collaboration with the JSPS Stockholm Office and aims at promoting exchange between researchers in Norway and Japan. I am a founding board member of the club and currently serve as its vice chair.
    In 2019 I have organized a very well received club seminar on the topic of Science-based innovation, while in 2021 I organized a JSPS ACN virtual social event to rekindle the networking activities of our club during the pandemic using the wonder.me platform.
    Club homepage: Link
    The #futureofresearch open letter campaign
    In September 2019, the von der Leyen commission announced that the portfolio of commissioner Mariya Gabriel will not contain the terms research and education. This decision foreshadowed possible budget cuts to research and education and significantly weakened commissioner Mariya Gabriel's position in negotiating research funding in the future EU budget. As reaction, I initiated and together with several colleagues carried out a signature campaign to convince the European parliament to demand from the commission to reinstate the terms education and research in the portfolio title. Our campaign collected a record number of 13.000 signatures from researchers all over Europe, including 19 Nobel prize laureates and a wealth of research organizations and played an important role in the decision of the von der Leyen commission to ultimately reinstate the terms research and education in Mariya Gabriel's portfolio title on November 27th 2019.
    Campaign homepage: Link
    2024
    The 2024 Pint of Science (May 13th-15th 2024)
    Pint of Science is an annual science festival that takes place every May and brings researchers to your local bar to tell you about the latest happenings in the world of science. It is the perfect opportunity to meet the women and men shaping the science of tomorrow. This year marks the third in-person edition of the festival in Stavanger, taking place at Blåveis in the Stavanger city center. Under this year's theme of "Transitions", we welcomed speakers from the University, the University Hospital, local companies and the arts scene. (Organized the Stavanger program together with Mark van der Giezen, Lisa Watson, Thilina Pathirana, Vera Sideraki, Alina Meloyan, Daria Larsson and Veronika Abdulina. The 2024 poster was designed by Veronika Abdulina.)
    2023
    Wonderful World Festival (June 1st-4th 2023)
    Wonderful World is a Science and Philosophy outreach festival organized by Kåkå, a non-profit organization with a focus on freedom of speech and open debate. This year at its inaugural edition, I gave a presentation on the science of fusion energy: from physical concepts to technical implementations (and a bit of investment advice). The presentation was followed by a round-table discussion on nuclear power, climate change and the energy transition with Sunniva Rose, Eirik Wærness and Jonas Kristiansen Nøland, moderated by Hilde Øvrebekk.
    The 2023 Pint of Science (May 22nd-24th 2023)
    Pint of Science is an annual science festival that takes place every May and brings researchers to your local bar to tell you about the latest happenings in the world of science. It is the perfect opportunity to meet the women and men shaping the science of tomorrow. This year marks the second in-person edition of the festival, taking place at Blåveis in the Stavanger city center. Under this year's theme of "Zero", I contributed a well-received outreach presentation on "Zero Temperature: Ultracold Matter". (Organized the Stavanger program together with Mark van der Giezen, Lisa Watson, Thilina Pathirana and Vera Sideraki.)
    2022
    The 2022 UiS Nobel Pub (Dec. 9th)
    Every year, the Nobel Prizes are awarded to ideas that have had extraordinary impact in the fields of medicine or physiology, physics, chemistry, literature, peace and economics. At the University of Stavanger we celebrate these ideas on the evening before the award ceremony, December 9th, with an annual series of outreach presentations by university staff. These presentations are geared at the general public and showcase the ideas behind each Nobel prize in everyday language. This year the event was held at the Archeological Museum Stavanger and it was my pleasure to present the physics Nobel prize with its far-reaching implications for the reality of microscopic particles. (Organized the event together with Mark van der Giezen and Olav Eggebø.)
    The 2022 Pint of Science (May 9th-11th 2022)
    Pint of Science is an annual science festival that takes place every May and brings researchers to your local bar to tell you about the latest happenings in the world of science. It is the perfect opportunity to meet the women and men shaping the science of tomorrow. This year marks the first in-person edition of the festival, taking place in collaboration with Nordic Edge at the Salon du Nord in the Stavanger city center. To share my passion for all things quantum, I contributed a well-received outreach presentation on "Quantum Computing". (Organized the Stavanger program together with Mark van der Giezen and student volunteer organizers. Poster designed collaboratively with Jassem Abbasi.)
    2021
    Adventures in Particle Physics (August 2nd, 4th and 6th 2021)
    As part of the 2021 virtual Tribute to Quark Confinement and the Hadron Spectrum conference, I organized an outreach program for the general public titled "Adventures in Particle Physics", aimed at sharing some of the physics research topics discussed at the conference. To this end it was a pleasure to welcome Eckard Elsen, former director of research and computing of the CERN laboratory in Switzerland, Chris Quigg, distinguished scientist emeritus at the Fermi National Accelerator Laboratory in the USA and Zhongbo Kang, group leader at the University of California Los Angeles, who in their presentations conveyed in everyday language the role particles play in nature and the strong forces binding them together. (I implemented the technical setup for 4k 360 degree live streaming to YouTube, designed the poster, choreographed the program and hosted all three of the evenings.)
    Homepage: vConf21
    "The CERN Laboratory" - Eckhard Elsen
    "Symmetries in Nature" - Chris Quigg
    "The Strong Force" - Zhongo Kang
    The Science of Energy (June 23rd 2021)
    As part of the 2021 biennial meeting of the Norwegian Physical Society (Fysikermøte 2021) I organized an outreach symposium on the topic of energy. The goal of this outreach event was to provide the audience with a scientific view on the different forms of energy that are and potentially can be part of the global energy mix in the future. As researcher and educator I also intended to provide teachers in high schools, their students and undergraduate lecturers impulses, which physics skills will be important to focus on, in order for the upcoming generation of physicists to have what it takes to contribute to solving the outstanding challenges in the field of energy. (Organized together with Anders Tranberg.)
    "The Science of Fission Energy" - June 23rd 2021
    The 2021 Pint of Science Stavanger (May 19th-21st 2021)
    Pint of Science is an annual science festival that takes place every May and brings researchers to your local bar to tell you about the latest happenings in the world of science. It is the perfect opportunity to meet the women and men shaping the science of tomorrow. I shared my passion for studying fundamental particles, by contributing an aoutreach presentation on "Dying particles in the little Bang" (360° VR video) on May 21st. (Organized the Stavanger program together with Mark van der Giezen. I implemented the technical setup for 4k 360 degree live streaming to YouTube, designed the poster, choreographed the program and hosted two of the evenings, while presenting on the third.)
    "Where the sun don't shine" - May 19th 2021
    "Dog eat dog" - May 20th 2021
    "Til death do us part" - May 21st 2021
    2020
    Celebrating the science of the 2020 Nobel prizes (December 9th 2020)
    Every year, the Nobel Prizes are awarded to people who have made extraordinary achievements in their field of work. The prize winners are hailed at award ceremonies of grandeur, but not everyone outside the prize winners' own field understand the achievements that form the basis of the prize. The University of Stavanger is therefore hosting a Nobel Prize event on Wednesday December 9th where researchers affiliated with UiS will present this year's six prize winners and explain to us outside the prize winners' professional circle why this year's prize winners have earned the prize. We have chosen December 9th as this is the evening before the official award ceremony. The presenters at the UiS event have all worked with topics related to this year's awards. (Organized together with Unni Berland, Olav Eggebø and Mark van der Giezen)
    Outreach lecture video: Link
    Outreach