Existence of Fermion Zero Modes and Deconfinement of Spinons in Quantum Antiferromagnetism resulting from Algebraic Spin Liquid

We investigate the quantum antiferromagnetism arising from algebraic spin liquid via spontaneous chiral symmetry breaking. We claim that in the antiferromagnet massive Dirac spinons can appear to make broad continuum spectrum at high energies in inelastic neutron scattering. The mechanism of spinon deconfinement results from the existence of fermion zero modes in single monopole potentials. Neel vectors can make a skyrmion configuration around a magnetic monopole of compact U(1) gauge fields. Remarkably, in the monopole-skyrmion composite potential the Dirac fermion is shown to have a zero mode. The emergence of the fermion zero mode forbids the condensation of monopoles, resulting in deconfinement of Dirac spinons in the quantum antiferromagnet.Comment: K. -S. Kim is much indebted to Dr. A. Tanaka who pointed out a mistake in association with the gradient expansion in Eq. (C3) and Eq. (C4

High-energy bremsstrahlung and pair production in the Coulomb field : Bethe and Maximon versus Cheng and Wu approaches

High-energy bremsstrahlung and pair production in the Coulomb field are investigated. The Cheng and Wu impact formula for the amplitude (obtained for a screened potential) is evaluated in the limit when the screening is removed; it is compared then with the high-energy limit of the amplitude calculated by Bethe and Maximon for the unscreened potential. The two limits are shown to be identical provided we calculate correctly the no-screening limit of the Coulomb scattering amplitude. In Cheng and Wu paper this calculation was wrong what led to double counting of the Bethe-Heitler amplitude for pair creation

Quantization of the Chern-Simons Coupling Constant

We investigate the quantum consistency of p-form Maxwell-Chern-Simons electrodynamics in 3p+2 spacetime dimensions (for p odd). These are the dimensions where the Chern--Simons term is cubic, i.e., of the form FFA. For the theory to be consistent at the quantum level in the presence of magnetic and electric sources, we find that the Chern--Simons coupling constant must be quantized. We compare our results with the bosonic sector of eleven dimensional supergravity and find that the Chern--Simons coupling constant in that case takes its corresponding minimal allowed value.Comment: 15 pages, 1 figure, JHEP3.cls. Equation (8.6) corrected and perfect agreement with previous results is obtaine

Analytic and Numerical Aspects of the Nonsingular Laplacian Representation of the Asymptotic Part of the Layered-Medium Green Function in the Mixed Potential Formulation

We report on developments in the evaluation of matrix elements of the electric and magnetic field operators involving the asymptotic (large transverse wave-number or small transverse distances) components of the mixed-potential Green's function of a layered medium. Subtracting these asymptotic terms significantly accelerates numerical computation of the Sommerfeld-type integrals required in constructing Green's function and then the matrix elements [1]

New Simplified Analytic Expressions for the Matrix Elements of the Asymptotic Part of the Layered Medium Green Function in the Mixed Potential Formulation

We report new developments in the analytical evaluation of the near-field contribution to the matrix elements of the electric and magnetic field operators for planar conducting structures embedded in a layered medium. The method is applicable to Rao-Wilton-Glisson (RWG) basis functions supported on parallel interfaces in the medium. Our method is an extension of the approach described in [1] of representing a Green function as a two-dimensional Laplacian of an auxiliary function. Such Laplacian representations can be obtained for the asymptotic forms of the Green functions, which are being subtracted in order to regularize the behavior of the Sommerfeld-type integrals. Matrix elements resulting from these asymptotic forms, given originally as quadruple surface integrals with singular integrands, are then reduced to double contour integrals over the perimeters of the surface elements, involving simple closed-form non-singular auxiliary functions

Natural abundance 14N and 15N solid-state NMR of pharmaceuticals and their polymorphs

14N ultra-wideline (UW), 1H{15N} indirectly-detected HETCOR (idHETCOR) and 15N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in combination with plane-wave density functional theory (DFT) calculations of 14N EFG tensors, were utilized to characterize a series of nitrogen-containing active pharmaceutical ingredients (APIs), including HCl salts of scopolamine, alprenolol, isoprenaline, acebutolol, dibucaine, nicardipine, and ranitidine. A case study applying these methods for the differentiation of polymorphs of bupivacaine HCl is also presented. All experiments were conducted upon samples with naturally-abundant nitrogen isotopes. For most of the APIs, it was possible to acquire frequency-stepped UW 14N SSNMR spectra of stationary samples, which display powder patterns corresponding to pseudo-tetrahedral (i.e., RR′R′′NH+ and RR′NH2+) or other (i.e., RNH2 and RNO2) nitrogen environments. Directly-excited 14N NMR spectra were acquired using the WURST-CPMG pulse sequence, which incorporates WURST (wideband, uniform rate, and smooth truncation) pulses and a CPMG (Carr-Purcell Meiboom-Gill) refocusing protocol. In certain cases, spectra were acquired using 1H → 14N broadband cross-polarization, via the BRAIN-CP (broadband adiabatic inversion – cross polarization) pulse sequence. These spectra provide 14N electric field gradient (EFG) tensor parameters and orientations that are particularly sensitive to variations in local structure and intermolecular hydrogen-bonding interactions. The 1H{15N} idHETCOR spectra, acquired under conditions of fast magic-angle spinning (MAS), used CP transfers to provide 1H–15N chemical shift correlations for all nitrogen environments, except for two sites in acebutolol and nicardipine. One of these two sites (RR′NH2+ in acebutolol) was successfully detected using the DNP-enhanced 15N{1H} CP/MAS measurement, and one (RNO2 in nicardipine) remained elusive due to the absence of nearby protons. This exploratory study suggests that this combination of techniques has great potential for the characterization of solid APIs and numerous other organic, biological, and inorganic systems

Novel Sensor Design Using Photonic Crystal Fibres for Monitoring the Onset of Corrosion in Reinforced Concrete Structures

In this paper, a novel sensing technique has been designed and investigated for the direct, in-situ detection of steel corrosion distributed in reinforced concrete structures. At present, structural health monitoring (SHM) in reinforced concrete structures is generally focused on monitoring the corrosion risk of the reinforcing steel. It is of significant importance, however, to inform industry of both the onset of corrosion and the corrosion rate as these are key contributors to structural degradation and thus evaluating the service life of the structures. This paper aims to address the above challenges by describing a novel corrosion sensor design using birefringent photonic crystal fibres (PCFs). The technique exploits fully both the birefringence of the fibres for force/pressure measurement and their very low temperature sensitivity to detect the onset of corrosion. This new type of sensor not only determines the onset of corrosion but also allows for better monitoring along the length of a reinforcement bar

Properties of neutron doped multicrystalline silicon for solar cells

The technology of neutron transmutation doping of silicon wafers in MARIA nuclear research reactor is described. The studies of the radiation defects performed with positron annihilation confirmed that divacancies dominate in the irradiated material. Thermal treatment of irradiated silicon at 700-1000°C produces void - phosphorus complexes and void aggregates. The resistivity of the samples produced by neutron transmutation doping was found to be uniform within 2.5% limits. The severe reduction of the minority carrier lifetime in irradiated samples was confirmed

Polarized proton-neutron total cross sections from proton-deuteron data

Simple expressions are derived for the polarized proton-deuteron total cross sections. Possibilities of extraction of the polarized proton-neutron cross sections from the proton-deuteron data are discussed. 19 references

Chiral non-linear sigma-models as models for topological superconductivity

We study the mechanism of topological superconductivity in a hierarchical chain of chiral non-linear sigma-models (models of current algebra) in one, two, and three spatial dimensions. The models have roots in the 1D Peierls-Frohlich model and illustrate how the 1D Frohlich's ideal conductivity extends to a genuine superconductivity in dimensions higher than one. The mechanism is based on the fact that a point-like topological soliton carries an electric charge. We discuss a flux quantization mechanism and show that it is essentially a generalization of the persistent current phenomenon, known in quantum wires. We also discuss why the superconducting state is stable in the presence of a weak disorder.Comment: 5 pages, revtex, no figure