Calibration of River Gauge at Afdeyu Research Station, Eritrea: A study conducted by MOA NARI and SLM

Afdeyu Station is one of the few river gauging stations in the highlands of Eritrea where daily measurements are taken. As a result of damages, the station was refurbished, and the cross section of the gauge was changed to have better control of minimal runoff. The gauge therefore had to be re-calibrated. This publication documents this process and also provides the new calibration curve, based on extensive field work carried out in the rainy season 2009

On supercurrent superfields and Fayet–Iliopoulos terms in N=1N=1 gauge theories

We revisit the supermultiplet structure of Noether currents for N=1 supersymmetric gauge theories. Using superfield identities and the field equations we show how to derive a superfield equation for the divergences of the Noether currents in terms of the supercurrent and anomaly superfields containing 16_B+16_F components. We refer to this as the natural supercurrent structure as it is invariant under all local symmetries of the theory. It corresponds to the S-multiplet of Komargodski and Seiberg. We clarify the on/off-shell nature of the currents appearing in this multiplet and we study in detail the effect of specific improvement transformations leading to 1) a Ferrara-Zumino multiplet and to 2) a multiplet containing the new improved energy-momentum tensor of Callan, Coleman and Jackiw. Our methods also apply to supersymmetric gauge theories with a Fayet-Iliopoulos term. We construct the natural supercurrent multiplet for such a theory and show how to improve this to a formally gauge-invariant Ferrara-Zumino multiplet by introducing a non-dynamical chiral superfield S to ensure superfield gauge invariance. Finally we study the coupling of this theory to supergravity and show that S remains non-dynamical if the theory is R-symmetric and that S becomes propagating if the theory is not R-symmetric, leading to non-minimal 16_B+16_F supergravity

Recovery of visual field and acuity after removal of epiretinal and inner limiting membranes

BACKGROUND: Visual acuity serves as only a rough gauge of macular function. The aim therefore was to ascertain whether central an assessment of the central visual field afforded a closer insight into visual function after removal of epiretinal membranes and Infracyanine-Green- or Trypan-Blue-assisted peeling of the inner limiting membrane. Patients and methods: Fourty-three patients undergoing pars-plana vitrectomy for the removal of epimacular membranes and dye-assisted peeling of the inner limiting membrane using either Infracyanine Green (n = 29; group 1) or Trypan Blue (n = 14; group 2) were monitored prospectively for 12 months. Preoperatively, and 1, 6 and 12 months postoperatively, distance and reading visual acuities were evaluated; the central visual field was assessed by automated static perimetry. RESULTS: Twelve months after surgery, distance and reading visual acuities had improved in both groups, but to a significant degree only in Trypan-Blue-treated eyes. The difference between the two groups was not significant. Likewise at this juncture, the mean size of the visual-field defect remained unchanged in Trypan-Blue-treated eyes (preoperative: 4.3 (SD 2.1) dB; 12 months: 4.0 (2.1) dB (p = 0.15)), but had increased in Infracyanine-Green-treated ones (from 5.3 (3.7) dB to 8.0 (5.2) dB (p = 0.027)). CONCLUSION: Unlike visual acuity, the central visual field had deteriorated in Infracyanine-Green-treated eyes but not in Trypan-Blue-treated eyes 12 months after surgery. Hence, as a predictor of functional outcome, testing of the central visual field may be a more sensitive gauge than visual acuity. Furthermore, Infracyanine Green may have a chronic and potentially clinically relevant effect on the macula which is not reflected in the visual acuity.

Exploring double field theory

We consider a flux formulation of Double Field Theory in which fluxes are dynamical and field-dependent. Gauge consistency imposes a set of quadratic constraints on the dynamical fluxes, which can be solved by truly double configurations. The constraints are related to generalized Bianchi Identities for (non-)geometric fluxes in the double space, sourced by (exotic) branes. Following previous constructions, we then obtain generalized connections, torsion and curvatures compatible with the consistency conditions. The strong constraint-violating terms needed to make contact with gauged supergravities containing duality orbits of non-geometric fluxes, systematically arise in this formulation.

Two-dimensional Lattice Gauge Theories with Superconducting Quantum Circuits

A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability.

From doubled Chern–Simons–Maxwell lattice gauge theory to extensions of the toric code

We regularize compact and non-compact Abelian Chern–Simons–Maxwell theories on a spatial lattice using the Hamiltonian formulation. We consider a doubled theory with gauge fields living on a lattice and its dual lattice. The Hilbert space of the theory is a product of local Hilbert spaces, each associated with a link and the corresponding dual link. The two electric field operators associated with the link-pair do not commute. In the non-compact case with gauge group R, each local Hilbert space is analogous to the one of a charged “particle” moving in the link-pair group space R2 in a constant “magnetic” background field. In the compact case, the link-pair group space is a torus U(1)2 threaded by k units of quantized “magnetic” flux, with k being the level of the Chern–Simons theory. The holonomies of the torus U(1)2 give rise to two self-adjoint extension parameters, which form two non-dynamical background lattice gauge fields that explicitly break the manifest gauge symmetry from U(1) to Z(k). The local Hilbert space of a link-pair then decomposes into representations of a magnetic translation group. In the pure Chern–Simons limit of a large “photon” mass, this results in a Z(k)-symmetric variant of Kitaev’s toric code, self-adjointly extended by the two non-dynamical background lattice gauge fields. Electric charges on the original lattice and on the dual lattice obey mutually anyonic statistics with the statistics angle . Non-Abelian U(k) Berry gauge fields that arise from the self-adjoint extension parameters may be interesting in the context of quantum information processing.