Sommerfeld Theory Colloquium (ASC)

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Can we tame the electronic Schrödinger equation? Jun 10, 2026

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One of the major problems of computational chemistry is the ab initio prediction of energies and properties of molecules. The electronic Schrödinger equations provides the in-principle solution, but because of intrinsic difficulties associated with the singular and long-ranged Coulomb interaction, this remains an extremely challenging task numerically. Here we outline a formalism called transcorrelation which provides a route out of the difficulties, whilst itself creating new problems (which have stumped the community for decades). We outline our work of the past few years in tackling these new problems, and show that the formalism has the potential to transform our ability to solve the Schrödinger problem in a general manner. In particular, by eliminating the Coulomb singularities, we show we can achieve both basis-set converged results, as well as thermodynamic limit results, with far fewer resources and less sophisticated many-body theories. Prospects to extend this methodology in the context of quantum computing will also be mentioned.

The massless limit of massive gauge fields Jun 10, 2026

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One of the simplest ways to make gauge fields massive is to add them a mass "by hand". Intuitively, one could expect that the corresponding massless theory would then be easy to recover. Yet, conventional methods indicate that such a limit is singular. In this talk, we will explore the massless limits of several massive gauge theories. We will identify the source of the apparent discontinuities and show that they are, in fact, simply an artifact of the perturbative approach. Then, we will discuss the consequences of this study on the relations between different gauge fields. Finally, we will conclude with a comment on the latest insights about these theories and their prospects.

Applications of Machine Learning and Neural Networks to Quantum Systems Jun 10, 2026

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Learning algorithms using deep neural networks are currently having a major impact on basic sciences. The physics of complex quantum systems is no exception, with multiple applications that constitute a new field of research. Examples include the representation and optimization of wave functions of quantum systems with large numbers of degrees of freedom (neural quantum states), the determination of wave functions from measurements (quantum tomography), and applications to the electronic structure of materials, such as the determination of more precise density functionals or the learning of force fields to accelerate molecular dynamics simulations. I will survey some of these applications, with an emphasis on neural quantum states.

Loop Blow-up Inflation Jun 10, 2026

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I will discuss recent progress in the study of cosmological applications of string compactifications with stabilised moduli, focusing in particular on inflation, reheating and dark energy.

Advances and Challenges in Solving the Two-Body Problem in General Relativity Jun 10, 2026

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Since the discovery of the first binary black-hole merger in 2015, analytical and numerical solutions to the relativistic two-body problem have been essential for the detection and interpretation of more than 100 gravitational-wave signals from compact-object binaries. Future experiments will detect black holes at cosmic dawn, probe the nature of gravity and reveal the composition of neutron stars with exquisite precision. Theoretical advances (of up to two orders of magnitude in the precision with which we can predict relativistic dynamics) are needed to turn gravitational-wave astronomy into precision laboratories of astrophysics, cosmology, and gravity. In this talk, I will discuss recent advances in modeling the two-body dynamics and gravitational radiation, review the science that accurate waveform models have enabled with LIGO-Virgo gravitational-wave observations, and highlight the theoretical challenges that lie ahead to fully exploit the discovery potential of increasingly sensitive detectors on the ground, such as the Einstein Telescope and Cosmic Explorer, and in space, such as the Laser Interferometer Space Antenna (LISA).

Ising’s Challenge and the Conformal Bootstrap Jun 10, 2026

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Throughout the century that has passed since Ernst Ising submitted his PhD thesis in 1924, the Ising (-Lenz) model has provided an incredibly fruitful challenge that gave rise to entirely new branches of physics and mathematics. In this colloquium I will focus on the conformal bootstrap program which was designed by Polyakov in 1974 as a mathematical method to access non-perturbative aspects of critical systems/fixed points of the renormalization groups. In the light of holography, such systems are also relevant for the study of quantum gravity. In my presentation I will review some of the milestone achievements of the modern conformal bootstrap and outline current frontiers. The advances will be benchmarked mostly within the context of the 3D Ising model.

What is String Theory? Jun 10, 2026

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String theory is around 50 years old and for much of that time it has been proclaimed as a quantum theory of gravity unified with all forces and matter. However, we still don’t know its fundamental formulation, although we do now know it is not just a theory of strings. Nonetheless, it has led to many new and surprising insights, with concepts that were once seen as absolute now seen as dependent on the “duality frame". In this talk I survey some of these insights and discuss their implications for physics and the fundamental formulation of string theory.

Thinking positively: the numerical quantum mechanical bootstrap Jun 10, 2026

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I will describe recent developments on the (numerical) computation of energy levels of various systems by the quantum mechanical bootstrap. The main way the bootstrap works is by using constraints that arise from positive matrices. Part of the goal is to turn the bootstrap problem into a problem that can be solved by semi-definite programming methods. I will describe how this method leads to solutions of the spectrum of various systems and will describe some additional applications of this way of solving problems to the study of quantum spin chains.

Effects of electronic correlations in BaOsO3 and tetragonal CuO Jun 10, 2026

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Strongly correlated electron systems, i.e. systems where the interaction between electrons cannot be treated as an effective potential, are an extremely fascinating, but also very challenging topic in modern solid state physics. The challenge arises in parts due to the simultaneous importance of non-local kinetic and local correlation effects, which make it important to treat both at equal footing. For this reason Dynamical Mean Field Theory (DMFT) has in the last decades become the state of the art method for electronic structure caluclations of strongly correlated electrons as it includes local correlation effects exactly, but also respects kinetic effects in terms of an embedding approach. In this talk, we will first motivate our interest in strongly correlated materials by giving an example regarding the fascinating properties that these materials can exhibit. This will be followed by an intuitive introduction to DMFT. Finally we present results from our DMFT studies of two strongly correlated systems: BaOsO3 [1] and tetragonal CuO (t-CuO) [2]. [1] MB, Jernej Mravlje, Martin Grundner, Ulrich Schollwoeck, and Manuel Zingl, Phys. Rev. B. 103, 165133 (2021) [2] MB, B. Bacq-Labreuil, M. Grundner, S. Biermann, U. Schollwoeck, S. Paeckel, and B. Lenz, SciPost Phys., 14, 010 (2023)

Multispherical shapes, constant-mean-curvature surfaces, and the endoplasmic reticulum Jun 10, 2026

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The cells of our body are divided up into separate subcompartments by fluid membranes with a thickness of only a few nanometers. Even though these membranes provide robust barriers for the exchange of molecules between different compartments, they can easily remodel their shape and topology. [1] A particularly interesting example of shape remodeling is the formation of multispherical shapes which represent constant- mean-curvature surfaceswith two values of the mean curvature. [2] The individual spheres are connected by membrane necks which are crucial for topology remodeling by membrane fission and fusion. Multispherical shapes can attain many distinct patterns with multispherical junctions. The latter geometry is reminiscent of the endoplasmic reticulum, a fascinating organelle that forms a large network of membrane nanotubes connected by three-way junctions. [1] R. Lipowsky. Remodeling of Membrane Shape and Topology by Curvature Elasticity and Membrane Tension. Adv. Biology 6, 2101020 (2022) [2] R. Lipowsky. Multispherical shapes of vesicles highlight the curvature elasticityof biomembranes. Adv. Colloid Interface Sci. 301, 102613 (2022)

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