Jürg Fröhlich

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Fröhlich

First Name

Jürg

ORCID

0000-0002-4388-5166

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Publications 1 - 10 of 11

A Tentative Completion of Quantum Mechanics
Fröhlich, Jürg; Gang, Zhou; Pizzo, Alessandro (2025)
Encyclopedia of Mathematical Physics
A proposal - referred to as the “ETH - Approach” - of how to complete non-relativistic quantum mechanics to a physically meaningful, mathematically precise and logically coherent theory is reviewed. This proposal leads to a general, non-linear stochastic law for the time-evolution of states of individual physical systems. An application of the general formalism to the quantum theory of fluorescence of an atom coupled to the radiation field is sketched. An outline of some elements of our approach to relativistic quantum theory concludes this review.
Fractional statistics, gauge invariance and anomalies in condensed matter physics
Fröhlich, Jürg (2024)
Encyclopedia of Condensed Matter Physics
A general formalism, dubbed “Gauge Theory of States/Phases of Matter,” which serves to partially classify electronic states in systems of condensed matter physics, and the theory of fractional statistics in low-dimensional systems are reviewed. Applications to the quantum Hall effect, to 2D time-reversal invariant insulators, and to certain 2D wave guides with chiral edge modes are sketched. The theory of 3D topological insulators, including Halperin's 3D quantized Hall effect and axionic insulators, is discussed too. The chiral magnetic effect is recalled and applied to Weyl semimetals.
Reminescences of Gianni Morchio
Fröhlich, Jürg (2023)
Trails in Modern Theoretical and Mathematical Physics: A Volume in Tribute to Giovanni Morchio
Two Results in the Quantum Theory of Measurements
Del Vecchio, Simone; Fröhlich, Jürg; Pizzo, Alessandro; et al. (2023)
Trails in Modern Theoretical and Mathematical Physics
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 clarifies the relationship between “events” and “measurements” and the meaning of measurements in the ETH-Approach to quantum mechanics.
Phase transitions, spontaneous symmetry breaking, and Goldstone's theorem
Fröhlich, Jürg (2024)
Encyclopedia of Condensed Matter Physics
Some important rigorous results on phase transitions accompanied by the spontaneous breaking of symmetries in statistical mechanics and relativistic quantum field theory are reviewed. Basic ideas, mainly inspired by quantum field theory, underlying the proofs of some of these results are sketched. The Goldstone theorem is proven, and the Mermin-Wagner-Hohenberg theorem concerning the absence of continuous symmetry breaking in one and two dimensions is recalled. Comments concerning rigorous results on the Kosterlitz-Thouless transition in the two-dimensional classical XY model are made.
A Theory of Quantum Jumps
Fröhlich, Jürg; Gang, Zhou; Pizzo, Alessandro (2025)
Communications in Mathematical Physics
Using the principles of the so-called ETH-Approach to Quantum Mechanics we describe fluorescence and the phenomenon of “quantum jumps” in idealized models of atoms coupled to the quantized electromagnetic field. In a limiting regime where the orbital motion of the atoms is neglected and the velocity of light tends to ∞ we derive explicit non-linear stochastic differential equations describing the effective time evolution of states of individual atoms. These equations give rise to a measure on state trajectories exhibiting quantum jumps representing a quantum-mechanical analogue of the Wiener measure on Brownian paths in the theory of diffusion.
Absolute values for cerebral blood flow and oximetry applying near infrared extinction: Elimination of the extracerebral signal by transcutaneous and parenchymatous measurements in parallel
Keller, Emanuela; Fröhlich, Jürg; Baumann, Dirk; et al. (2010)
Neurocritical Care
Gauge invariance and anomalies in condensed matter physics
Fröhlich, Jürg (2023)
Journal of Mathematical Physics
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 formalism, is recalled. I then sketch an application of the chiral anomaly in 1 + 1 dimensions to quantum wires. Subsequently, some elements of the quantum Hall effect in two-dimensional (2D) gapped ("incompressible") electron liquids are reviewed. In particular, I discuss the role of anomalous chiral edge currents and of the anomaly inflow in 2D gapped electron liquids with explicitly or spontaneously broken time reversal, i.e., in Hall and Chern insulators. The topological Chern-Simons action yielding transport equations valid in the bulk of such systems and the associated anomalous edge action are derived. The results of a general classification of "Abelian"Hall insulators are outlined. After some remarks on induced Chern-Simons actions, I sketch results on certain 2D chiral photonic wave guides. I then continue with an analysis of chiral edge spin-currents and bulk response equations in time-reversal invariant 2D topological insulators of electron gases with spin-orbit interactions. The "chiral magnetic effect"in 3D systems and axion-electrodynamics are reviewed next. This prepares the ground for an outline of a general theory of 3D topological insulators, including "axionic insulators."Some remarks on Weyl semi-metals, which exhibit the chiral magnetic effect, and on Mott transitions in 3D systems with dynamical axion-like degrees of freedom conclude this review.
Traveling-Wave RF Shimming and Parallel MRI
Brunner, David O.; Paška, Jan; Fröhlich, Jürg; et al. (2011)
Magnetic Resonance in Medicine
At sufficiently high Larmor frequencies, traveling electromagnetic waves along a magnet bore can be used for remote magnetic resonance excitation and detection, effectively using the bore as a waveguide. So far, this approach has relied only on the lowest waveguide modes and thus has not supported multiple-channel operation for radiofrequency shimming and parallel imaging. In this work, this limitation is addressed by establishing a larger number of propagating modes and tapping their spatial field diversity with multiple waveguide ports. The number of available modes is increased by loading with dielectric inserts; the ports are implemented by stub and loop couplers at the end of a waveguide extension. The resulting traveling-wave array, operated at 298 MHz in a 7T whole-body magnet, is shown to enable radiofrequency shimming as well as parallel imaging with commonly used acceleration factors. The last part of the study concerns the amount of dielectric loading that is required. For the given Larmor frequency and bore dimensions, it is found that rather few water-filled inserts, occupying ∼5% of the bore cross-section, are sufficient for effective parallel imaging.
Cytotoxic effects of indocyanine green and combined irradiation with near infrared light on cultered human endothelial cells
Sikorski, Christopher; Frei, Karl; Fröhlich, Jürg; et al. (2010)
Neurocritical Care

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