Local Quantum Physics 52 and Mathematical Physics in the Heart of Germany VII

Contribution List

2. Chris Fewster: Local Quantum Physics: Ancient and Modern

5/7/26, 2:20 PM

I will give an outline of local quantum physics/algebraic quantum field theory, starting from basic operational ideas and leading to some modern perspectives concerning measurement in QFT. If time allows I will also discuss some situations in which the local paradigm must be loosened to include "semi-local" observables.

3. Christiane Klein: Coupled Proca theories - Green-hyperbolicity and application to quantum polarization measurement

5/7/26, 3:40 PM

The Proca equation describes a massive relativistic spin-1 particle, such as the Z-boson appearing in the Standard Model of particle physics. In this talk, we consider various extensions of the Proca equations on curved spacetimes, such as the equation of a charged Proca fields coupled to a background electromagnetic field or the one of a Proca field linearly coupled to a scalar field. We...

4. Matteo Bruno: Spin Structures and Cosmology in Loop Quantum Gravity

5/7/26, 4:45 PM

In this talk, we analyze the role of the spin structure in the Ashtekar–Barbero–Immirzi formulation of General Relativity. While not often taken into account in the full theory, it becomes crucial in cosmology. In particular, by employing a suitable notion of homogeneous connection, in the spirit of Wang’s theorem, we classify the homogeneous Ashtekar variables by computing the corresponding...

5. Gilles Jordan Pedieu Tcheuha: Non-Existence of Stationary Equilibrium Configurations of Three Aligned Rotating Black Holes

5/7/26, 5:20 PM

Following the foundational studies of Hennig and Neugebauer on the balance of binary black holes, this work addresses the long-standing question of whether a third body can stabilize a stationary configuration. By constructing the explicit Triple-Kerr-NUT solution and employing a generalized regularity criterion based on sub-extremality inequalities, we provide a rigorous proof for the...

6. Jesús Fernando Barbero González: The Husain-Kuchar model as the Carrollian limit of the Holst action

5/7/26, 5:55 PM

The Husain-Kuchar model is a useful auxilliary theory in the context of Loop Quantum Gravity. Its Hamiltonian formulation shares the same phase space as the Ashtekar formulation for General Relativity. In this talk I will show how this model can be understood as the Carrollian limit of the Holst action. This explains in a neat way some of its dynamical features and suggests other related...

7. Volker Bach: Renormalization Group based on the Smooth Feshbach-Schur Map

5/8/26, 9:00 AM

About three decades ago, a renormalization transformation based on the Feshbach--Schur Map was developed and applied to spectral problems in nonrelativistic QED. Among other things, the existence of ground states and resonances of these systems, and their computation to arbitrary accuracy by a convergent renormalization scheme was established. Starting from these results, further developments...

8. Jobst Ziebell: Functional renormalisation flows without regularisation

5/8/26, 10:35 AM

I present a very general framework in which Wetterich's equation can be applied to a vast class of probability measures on locally convex spaces. I will focus on the $\phi^4_2$ model as a particular example.

9. Denis Perice: Ground state of the Bose-Hubbard model with large coordination number

5/8/26, 11:10 AM

We consider the ground state energy of the Bose-Hubbard model on a graph with large and homogeneous coordination number. In the limit of infinite coordination number, we prove convergence of the ground state energy to the minimizer of a mean-field energy functional. This functional is obtained by averaging the hopping term over the large number of connected sites, while the interaction energy...

10. Fabian Nolte: Time-Dependent van Hove-Miyatake Model

5/8/26, 11:45 AM

The model’s simplicity and exact solvability enable a detailed analysis of its dynamics. Its semiclassical nature provides heuristic insight into obstacles to convergence toward scattering states, with insights that extend to more complex models. The use of cutoffs and regularization procedures, originating in Nelson’s model, leads to scattering amplitudes whose cutoff dependence becomes...

11. Maik Reddiger: A solution of the time of arrival problem via mathematical probability theory

5/8/26, 1:50 PM

Time of arrival refers to the time a particle takes after emission to impinge upon a suitably idealized detector surface. Within quantum theory, no generally accepted solution exists to date for the corresponding probability distribution of arrival times. Here I derive a general solution for a single body without spin impacting on a perfectly absorbing detector in the absence of any other...

12. Fridolin Melong: q-Deformed Topological Recursion: Quantum Curves and Non-perturbative Analysis

5/8/26, 2:25 PM

This work investigates the $q$-deformation of $(r, s)$-Airy structures and their realization via symmetric $q$-difference operators, providing a bridge between quantum spectral curves and integrable systems. We construct an all-order $q$-WKB solution for the matrix systems associated with the $q$-quantized curve $E_q (x, y) = 0$. We demonstrate that the resulting non-perturbative connected...

13. Carmine De Rosa: Achronal localization and representations of the causal logic

5/8/26, 3:00 PM

Achronal localization has recently been proposed as a natural framework for relativistic quantum localization. In this talk, I will present a general covariant construction of achronal localizations from conserved currents via their flux through achronal surfaces. I will discuss the case of the massive scalar boson, showing how probability currents with causal kernel and the stress-energy...

14. Christiaan Jozef Farielda van de Ven: Coupling of the continuum and semiclassical limit. Part I: convergence of eigenvalues

5/8/26, 4:05 PM

In this talk we analyze the semiclassical d-dimensional Schrödinger operator in the continuum $-1/2\Delta + \lambda_N^2 V$ discretized on a mesh with spacing proportional to $1/N$. The semi-classical parameter $\lambda_N$ is chosen as $\lambda_N = N^{1 - \gamma}$, with $\gamma \in (-1,1)$, which ensures that $N$ governs both the semiclassical and continuum limit simultaneously. We prove that...

15. Lorenzo Pettinari: Damping of phonons in Bose gas at low temperature

5/8/26, 4:40 PM

Condensed Bose gases can be effectively described in terms of quasi-particles, commonly referred to as \textit{phonons}. Their dynamics are captured by a \textit{c-number condensate Hamiltonian} consisting of a quadratic term supplemented by third- and fourth-order perturbative corrections. These additional interaction terms render the phonons unstable, giving rise to two distinct decay...

16. Marcel Griesemer: On Rayleigh scattering in the massless Nelson model

5/8/26, 5:15 PM

Asymptotic completeness of Rayleigh scattering in models of atoms and molecules of non-relativistic QED is expected, but to prove it, we still lack sufficient control over the number of emitted soft photons. So far, this obstacle has only been overcome for the spin-boson model. In a general class of models, asymptotic completeness holds provided the expectation value of the photon number $N$...

18. Francesco Fidaleo: Twisted C*-tensor product

5/9/26, 9:00 AM

We describe the (infinite) C*-tensor product as the generalization of the usual tensor product and the Fermi one (that is what based on the Fermi bicharacter). After constructing the infinite chain tensor product, we show that the investigation of the set of the symmetric states (that is those invariant under the action of the finitary symmetric group), can be fruitfully carried out in only...

19. Christoph Minz: A scheme to bound relative modular Hamiltonians in QFT

5/9/26, 10:05 AM

Relative modular Hamiltonians are operators in quantum field theory to compute relative entropy, relating to a key concept in quantum information theory. Since explicit expression for these operators are known to be very difficult to find, we describe a scheme to estimate relative modular Hamiltonians between two states, both related to a reference state (like the vacuum) for which the modular...

21. Alessandro Pietro Contini: Timelike boundaries and the Hadamard condition

5/9/26, 11:10 AM

In this talk we review the setting of globally hyperbolic manifolds with timelike boundaries and discuss the Klein-Gordon field on them. We will then discuss work in progress with Alexander Strohmaier concerning the extension of the Hadamard condition for states to include, among others, fields satisfying the Dirichlet boundary condition.

22. Markus B. Fröb: News on relative entropy

5/9/26, 11:45 AM

I present recent work on a new integral representation for the relative entropy (or Kullback-Leibler divergence) for general tracial von Neumann algebras, generalizing results for matrix algebras. This representation allows easy proofs of its properties such as joint convexity and an extended version of the data processing inequality, namely monotonicity under positive unit-preserving maps....

23. Daniela Cadamuro: The massive modular Hamiltonian in the case of fermions

5/9/26, 12:20 PM

The Tomita-Takesaki modular operator for local algebras plays an important role in quantum field theory, and more recently in the study of relative entropy. However, the explicit expression of this operator, except for the case of wedges, is difficult to describe mathematically. We have obtained numerical results for the form of the modular Hamiltonian for free massive Majorana fermions in 1+1...