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1. Conformal field theories in a magnetic field

   https://doi.org/10.1103/PhysRevResearch.6.043093  

   Boyack, Rufus; Delacrétaz, Luca; Dupuis, Éric; Witczak-Krempa, William (November 2024, Physical Review Research)

   We study the properties of 2+1d conformal field theories (CFTs) in a background magnetic field. Using generalized particle-vortex duality, we argue that in many cases of interest the theory becomes gapped, which allows us to make a number of predictions for the magnetic response, background monopole operators, and more. Explicit calculations at large $N$for Wilson-Fisher and Gross-Neveu CFTs support our claim, and yield the spectrum of background (defect) monopole operators. Finally, we point out that other possibilities exist: certain CFTs can become metallic in a magnetic field. Such a scenario occurs, for example, with a Dirac fermion coupled to a Chern-Simons gauge field, where a non-Fermi liquid is argued to emerge. Published by the American Physical Society2024 

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2. Magnetic field imaging in a laboratory plasma

   https://doi.org/10.1063/5.0052957  

   Gilbert, T_J; Stevenson, K_J; Paul, M_C; Steinberger, T_E; Scime, E_E (May 2021, AIP Advances)

   In laboratory plasmas, arrays of probes have typically been used to measure the evolution of the magnetic field topology. Here, we present initial image-based measurements of the magnetic topology in a low-temperature plasma using a purely optical diagnostic. Laser induced fluorescence measurements of neutral velocity distribution functions are made using a fast camera, imaging the Zeeman splitting of σ-peaks in neutral argon. The separation of σ-peaks provides spatially resolved magnetic field magnitude measurements with a detection threshold on the order of 10 G. 

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3. Topological symmetry in quantum field theory

   https://doi.org/10.4171/qt/223  

   Freed, Daniel S; Moore, Gregory W; Teleman, Constantin (October 2024, Quantum Topology)

   We introduce a definition and framework for internal topological symmetries in quantum field theory, including “noninvertible symmetries” and “categorical symmetries”. We outline a calculus of topological defects which takes advantage of well-developed theorems and techniques in topological field theory. Our discussion focuses on finite symmetries, and we give indications for a generalization to other symmetries. We treat quotients and quotient defects (often called “gauging” and “condensation defects”), finite electromagnetic duality, and duality defects, among other topics. We include an appendix on finite homotopy theories, which are often used to encode finite symmetries and for which computations can be carried out using methods of algebraic topology. Throughout we emphasize exposition and examples over a detailed technical treatment. 

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4. Field Line Resonances in Jupiter's Magnetosphere

   https://doi.org/10.1029/2020GL089473  

   Lysak, R. L.; Song, Y. (September 2020, Geophysical Research Letters)

   Abstract The arrival of the Juno satellite at Jupiter has led to an increased interest in the dynamics of the Jovian magnetosphere. Jupiter's auroral emissions often exhibit quasiperiodic oscillations with periods of tens of minutes. Magnetic observations indicate that ultralow‐frequency (ULF) waves with similar periods are often seen in data from Galileo and other satellites traversing the Jovian magnetosphere. Such waves can be associated with field line resonances, which are standing shear Alfvén waves on the field lines. Using model magnetic fields and plasma distributions, the frequencies of field line resonances and their harmonics on field lines connecting to the main auroral oval have been determined. Time domain simulations of Alfvén wave propagation have illustrated the evolution of such resonances. These studies indicate that harmonics of the field line resonances are common in the 10–40 min band. 

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5. ELVIS: A Correlated Light-Field and Digital Holographic Microscope for Field and Laboratory Investigations – Field Demonstration

   https://doi.org/10.1017/S1551929520001133  

   Kim, Taewoo; Serabyn, Eugene; Liewer, Kurt; Oborny, Nathan; Wallace, J. Kent; Rider, Stephanie; Bedrossian, Manuel; Lindensmith, Christian; Nadeau, Jay (July 2020, Microscopy Today)

   Following the previous article, here we describe the first field demonstration of the ELVIS system, performed at Newport Beach, CA. We examined ocean water to detect microorganisms using the combined holographic and light-field fluorescence microscope and successfully detected both eukaryotes and prokaryotes. The shared field of view provided simultaneous bright-field (amplitude), phase, and fluorescence information from both chlorophyll autofluorescence and acridine orange staining. The entire process was performed in a nearly autonomous manner using a specifically designed sample processing unit (SPU) and custom acquisition software. We also discuss improvements to the system made after the field test that will make it more broadly useful to other types of fluorophores and samples. 

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