Enlarged Galilean symmetry of anyons and the Hall effect

Enlarged planar Galilean symmetry, built of both space-time and field variables and also incorporating the ``exotic'' central extension is introduced. It is used to describe non-relativistic anyons coupled to an electromagnetic field. Our theory exhibits an anomalous velocity relation of the type used to explain the Anomalous Hall Effect. The Hall motions, characterized by a Casimir of the enlarged algebra, become mandatory for some critical value(s) of the magnetic field. The extension of our scheme yields the semiclassical effective model of the Bloch electron.Comment: LaTeX, 7 pages. No figures. One more reference adde

Construction of the Pauli-Villars-regulated Dirac vacuum in electromagnetic fields

Using the Pauli-Villars regularization and arguments from convex analysis, we construct solutions to the classical time-independent Maxwell equations in Dirac's vacuum, in the presence of small external electromagnetic sources. The vacuum is not an empty space, but rather a quantum fluctuating medium which behaves as a nonlinear polarizable material. Its behavior is described by a Dirac equation involving infinitely many particles. The quantum corrections to the usual Maxwell equations are nonlinear and nonlocal. Even if photons are described by a purely classical electromagnetic field, the resulting vacuum polarization coincides to first order with that of full Quantum Electrodynamics.Comment: Final version to appear in Arch. Rat. Mech. Analysi

Parity nonconservation in heavy atoms: The radiative correction enhanced by the strong electric field of the nucleus

Parity nonconservation due to the nuclear weak charge is considered. We demonstrate that the radiative corrections to this effect due to the vacuum fluctuations of the characteristic size larger than the nuclear radius $r_0$ and smaller than the electron Compton wave-length $\lambda_C$ are enhanced because of the strong electric field of the nucleus. The parameter that allows one to classify the corrections is the large logarithm $\ln(\lambda_C/r_0)$. The vacuum polarization contribution is enhanced by the second power of the logarithm. Although the self-energy and the vertex corrections do not vanish, they contain only the first power of the logarithm. The value of the radiative correction is 0.4% for Cs and 0.9% for Tl, Pb, and Bi. We discuss also how the correction affects the interpretation of the experimental data on parity nonconservation in atoms.Comment: 4 pages, 3 figures, RevTe

Strategies to build a positive and inclusive Antarctic field work environment

Support from National Science Foundation (NSF: Grants 1738913, 1738896, 1738942, 1738992, 1738896, 1738934) and Natural Environment Research Council (NERC: Grants NE/S006788/1, NE/S006605/1, NE/S00677X/1). This research was supported in part by the NOAA cooperative agreement NA17OAR4320101. Logistics provided by NSF-U.S. Antarctic Program and NERC-British Antarctic Survey. ITGC Contribution No. ITGC-084.To increase inclusivity, diversity, equity and accessibility in Antarctic science, we must build more positive and inclusive Antarctic field work environments. The International Thwaites Glacier Collaboration (ITGC) has engaged in efforts to contribute to that goal through a variety of activities since 2018, including creating an open-access 'Field and Ship Best Practices' guide, engaging in pre-field season team dynamics meetings, and surveying post-field season reflections and experiences. We report specific actions taken by ITGC and their outcomes. We found that strong and supported early career researchers brought new and important perspectives regarding strategies for transforming culture. We discovered that engaged and involved senior leadership was also critical for expanding participation and securing funding to support efforts. Pre-field discussions involving all field team members were particularly helpful for setting expectations, improving sense of belonging, describing field work best practices, and co-creating a positive work culture.Publisher PDFPeer reviewe

Localization corrections to the anomalous Hall effect in a ferromagnet

We calculate the localization corrections to the anomalous Hall conductivity related to the contribution of spin-orbit scattering into the current vertex (side-jump mechanism). We show that in contrast to the ordinary Hall effect, there exists a nonvanishing localization correction to the anomalous Hall resistivity. The correction to the anomalous Hall conductivity vanishes in the case of side-jump mechanism, but is nonzero for the skew scattering. The total correction to the nondiagonal conductivity related to both mechanisms, does not compensate the correction to the diagonal conductivity.Comment: 7 pages with 7 figure

New Results in Four and Five Loop QED calculations

We report on two recent multiloop results in QED: (i) the four-loop corrections to the conversion relations between the QED charge renormalized in the on-shell and MS-bar schemes; (ii) analytical evaluation of a class of asymptotic contributions to the muon anomaly at five-loops.Comment: Talk presented at 9th DESY Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Sondershausen, Germany, 20-25 April 200

How the specificity for pyridine nucleotides of ferredoxin-NADP+ reductase could be modified by engineering the portion of the binding site common to both coenzymes

Varese, Ital

High resolution studies of hydride transfer in the ferredoxin: NADP+ reductase superfamily

Ferredoxin-NADP+ reductase (FNR) is an FAD-containing enzyme that catalyzes the transfer of electrons from photoreduced ferredoxin (Fd) to NADP+ during photosynthesis. It is also the prototype for a broad superfamily of enzymes, including nictric oxide synthase, cytochrome P450 reductase, and the NOX family of NADPH oxidases, that all catalyze hydride transfer between NADPH and FAD. The goal of our research is to define the mechanistic details of that hydride transfer reaction. Previous studies using a pea FNR active site mutant revealed a 1.8 \uc5 resolution view of productive NADP(H) binding, and differences in the electron density around the C4 position of NADP+ and NADPH suggested that mobility at this carbon is important for efficient hydride transfer. In order to obtain higher resolution views of the nicotinamide-flavin interaction, we turned to the corn root FNR system for which crystals grown in the absence of NADP(H) diffracted to 1.05 \uc5 resolution. We created the Y316A and Y316S mutants of corn root FNR and have now determined structures at better than 1.5 \uc5 resolution of their complexes with NADP+, NADPH, and nicotinamide. The mutant protein crystallizations required nicotinamide, and the other complexes were generated by subsequent soaks with NADP+ or NADPH. Comparisons among the FNR complexes reveals systematic, but subtle shifts in the active site packing and covalent distorsion that allow us to conclude there is significant compression that pushes the reactant together, thereby enhancing catalysis. Furthermore, the anisotropic B-factors confirm a stricking increase in mobility of the nicotinamide C4 atom in NADP+ as compared to NADPH, and the directionality of the disorder matches the expected motions needed to adopt the boat-like conformation of the nicotinamide ring that is known to enhance hydride transfer