Jürg Fröhlich
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View article: Boundary effects and the stability of the low energy spectrum of the AKLT model
Boundary effects and the stability of the low energy spectrum of the AKLT model Open
View article: Cosmological Magnetic Fields from Ultralight Dark Matter
Cosmological Magnetic Fields from Ultralight Dark Matter Open
We propose a mechanism for the generation of magnetic fields on cosmological scales that is operative after recombination. An essential ingredient is an instability (of parametric resonance type) of the electromagnetic field driven by an o…
View article: 6. Die neue rechte Bewegung: a very short story
6. Die neue rechte Bewegung: a very short story Open
View article: 7. Die Dauer des Volkes: Die Zeitdimension der neuen rechten Bewegung
7. Die Dauer des Volkes: Die Zeitdimension der neuen rechten Bewegung Open
View article: The Euclidean $\phi^{4}_{2}$ theory as a limit of an interacting Bose gas
The Euclidean $\phi^{4}_{2}$ theory as a limit of an interacting Bose gas Open
We prove that the complex Euclidean field theory with local quartic self-interaction in two dimensions arises as a limit of an interacting Bose gas at positive temperature, when the density of the gas becomes large and the range of the int…
View article: The Euclidean $\phi^{4}_{2}$ theory as a limit of an interacting Bose gas
The Euclidean $\phi^{4}_{2}$ theory as a limit of an interacting Bose gas Open
We prove that the complex Euclidean field theory with local quartic self-interaction in two dimensions arises as a limit of an interacting Bose gas at positive temperature, when the density of the gas becomes large and the range of the int…
View article: Two Results in the Quantum Theory of Measurements
Two Results in the Quantum Theory of Measurements Open
Two theorems with applications to the quantum theory of measurements are stated and proven. The first one clarifies and amends von Neumann's Measurement Postulate used in the Copenhagen interpretation of quantum mechanics. The second one c…
View article: Phase transitions, spontaneous symmetry breaking, and Goldstone's theorem
Phase transitions, spontaneous symmetry breaking, and Goldstone's theorem Open
View article: Boundary effects and the stability of the low energy spectrum of the AKLT model
Boundary effects and the stability of the low energy spectrum of the AKLT model Open
In this paper we study the low-lying spectrum of the AKLT model perturbed by small, finite-range potentials and with open boundary conditions imposed at the edges of the chain. Our analysis is based on the \emph{local, iterative Lie Schwin…
View article: Low energy spectrum of the XXZ model coupled to a magnetic field
Low energy spectrum of the XXZ model coupled to a magnetic field Open
For a class of Hamiltonians of $XXZ$ spin chains in a uniform external magnetic field that are small quantum perturbations of an Ising Hamiltonian, it is shown that the spectral gap above the ground-state energy remains strictly positive w…
View article: Gauge Invariance and Anomalies in Condensed Matter Physics
Gauge Invariance and Anomalies in Condensed Matter Physics Open
This paper begins with a summary of a powerful formalism for the study of electronic states in condensed matter physics called "Gauge Theory of States/Phases of Matter." The chiral anomaly, which plays quite a prominent role in that formal…
View article: A Completion of Quantum Mechanics
A Completion of Quantum Mechanics Open
A proposal of how to complete non-relativistic quantum mechanics to a physically meaningful, mathematically precise and logically coherent theory is reviewed. Our proposal leads to a general, non-linear stochastic law for the time-evolutio…
View article: Gauge invariance and anomalies in condensed matter physics
Gauge invariance and anomalies in condensed matter physics Open
This paper begins with a summary of a powerful formalism for the study of electronic states in condensed matter physics called “gauge theory of states/phases of matter.” The chiral anomaly, which plays quite a prominent role in that formal…
View article: On the Evolution of States in a Quantum-Mechanical Model of Experiments
On the Evolution of States in a Quantum-Mechanical Model of Experiments Open
The postulates of von Neumann and Lüders concerning measurements in quantum mechanics are discussed and criticized in the context of a simple model proposed by Gisin. The main purpose of our paper is to analyze some mathematical aspects of…
View article: <i>Local</i> iterative block-diagonalization of gapped Hamiltonians: A new tool in singular perturbation theory
<i>Local</i> iterative block-diagonalization of gapped Hamiltonians: A new tool in singular perturbation theory Open
In this paper, the local iterative Lie–Schwinger block-diagonalization method, introduced and developed in our previous work for quantum chains, is extended to higher-dimensional quantum lattice systems with Hamiltonians that can be writte…
View article: The appearance of particle tracks in detectors. II. The semi-classical realm
The appearance of particle tracks in detectors. II. The semi-classical realm Open
The appearance of tracks, close to classical orbits, left by charged quantum particles propagating inside a detector, such as a cavity periodically illuminated by light pulses, is studied for a family of idealized models. In the semi-class…
View article: The time-dependent Hartree–Fock–Bogoliubov equations for Bosons
The time-dependent Hartree–Fock–Bogoliubov equations for Bosons Open
View article: Irreversibility and the Arrow of Time
Irreversibility and the Arrow of Time Open
Within the general formalism of quantum theory irreversibility and the arrow of time in the evolution of various physical systems are studied. Irreversible behavior often manifests itself in the guise of entropy production. This motivates …
View article: Towards a Dark Sector Model from String Theory
Towards a Dark Sector Model from String Theory Open
An embedding of a unified dark sector model into string theory with the following features is proposed: The model-independent axion descending from the Kalb-Ramond 2-form field is identified with the dark-matter field, and the real part of…
View article: The Time-Evolution of States in Quantum Mechanics according to the ETH-Approach
The Time-Evolution of States in Quantum Mechanics according to the ETH-Approach Open
It is argued that the Schrödinger equation does not yield a correct description of the quantum-mechanical time evolution of states of isolated physical systems featuring events. A general statistical law replacing unitary Schrödinger evolu…
View article: In Memoriam: Freeman Dyson (1923–2020)
In Memoriam: Freeman Dyson (1923–2020) Open
View article: The mean-field limit of quantum Bose gases at positive temperature
The mean-field limit of quantum Bose gases at positive temperature Open
We prove that the grand canonical Gibbs state of an interacting quantum Bose gas converges to the Gibbs measure of a nonlinear Schrödinger equation in the mean-field limit, where the density of the gas becomes large and the interaction str…
View article: The appearance of particle tracks in detectors
The appearance of particle tracks in detectors Open
View article: The Time-Evolution of States in Quantum Mechanics
The Time-Evolution of States in Quantum Mechanics Open
It is argued that the Schrödinger equation does not yield a correct description of the quantum-mechanical time evolution of states of isolated (open) systems featuring events. A precise general law for the time evolution of states replacin…
View article: Interacting loop ensembles and Bose gases
Interacting loop ensembles and Bose gases Open
We study interacting Bose gases in thermal equilibrium on a lattice. We establish convergence of the grand canonical Gibbs states of such gases to their mean-field (classical field) and large-mass (classical particle) limits. The former is…
View article: Introduction to the Special Issue in Honor of Joel Lebowitz
Introduction to the Special Issue in Honor of Joel Lebowitz Open
View article: The mean-field limit of quantum Bose gases at positive temperature
The mean-field limit of quantum Bose gases at positive temperature Open
We prove that the grand canonical Gibbs state of an interacting quantum Bose gas converges to the Gibbs measure of a nonlinear Schr\"odinger equation in the mean-field limit, where the density of the gas becomes large and the interaction s…
View article: A microscopic derivation of time-dependent correlation functions of the 1D cubic nonlinear Schrödinger equation
A microscopic derivation of time-dependent correlation functions of the 1D cubic nonlinear Schrödinger equation Open
View article: A microscopic derivation of time-dependent correlation functions of the 1D cubic nonlinear Schrödinger equation
A microscopic derivation of time-dependent correlation functions of the 1D cubic nonlinear Schrödinger equation Open
View article: Asymptotic completeness in dissipative scattering theory
Asymptotic completeness in dissipative scattering theory Open