Infinite Renormalization of Theta-Term and Jarlskog Invariant for CP-Violation

The logarithmic ultraviolet divergence in the theta-term induced by electroweak interactions in the Kobayashi-Maskawa model of CP-violation, found by Ellis and Gaillard, is discussed. We relate it to the Jarlskog CP-odd invariant of quark mass matrix. The divergence arises in 14th order in Higgs coupling as well as in 12th order plus 2nd order in U(1) gauge boson coupling.Comment: 6 pages + 1 figure (included), LaTex, TPI-MINN-93/91-T, UMN-TH-1212/9

MIMO free-space optical communication employing subcarrier intensity modulation in atmospheric turbulence channels

In this paper, we analyse the error performance of transmitter/receiver array free-space optical (FSO) communication system employing binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in clear but turbulent atmospheric channel. Subcarrier modulation is employed to eliminate the need for adaptive threshold detector. Direct detection is employed at the receiver and each subcarrier is subsequently demodulated coherently. The effect of irradiance fading is mitigated with an array of lasers and photodetectors. The received signals are linearly combined using the optimal maximum ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SelC). The bit error rate (BER) equations are derived considering additive white Gaussian noise and log normal intensity fluctuations. This work is part of the EU COST actions and EU projects

Electromagnetic characteristics of bilayer quantum Hall systems in the presence of interlayer coherence and tunneling

The electromagnetic characteristics of bilayer quantum Hall systems in the presence of interlayer coherence and tunneling are studied by means of a pseudospin-texture effective theory and an algebraic framework of the single-mode approximation, with emphasis on clarifying the nature of the low-lying neutral collective mode responsible for interlayer tunneling phenomena. A long-wavelength effective theory, consisting of the collective mode as well as the cyclotron modes, is constructed. It is seen explicitly from the electromagnetic response that gauge invariance is kept exact, this implying, in particular, the absence of the Meissner effect in bilayer systems. Special emphasis is placed on exploring the advantage of looking into quantum Hall systems through their response; in particular, subtleties inherent to the standard Chern-Simons theories are critically examined.Comment: 9 pages, Revtex, to appear in Phys. Rev.

Optical spectroscopy and current detection during warm-up and destruction of impurity–helium condensates

New experimental results on detection of optical spectra and ion currents during destruction of impurity–helium condensates (IHCs) have been obtained. It is shown that emission during IHC sample destruction is accompanied by current pulses, pressure peaks and temperature changes. The molecular bands of excimer molecules XeO* are assigned to molecules stabilized in films of molecular nitrogen covering the heavier cores of impurity clusters which form impurity–helium condensates

Dynamics of thermoluminescence spectra of impurity– helium condensates containing stabilized nitrogen and oxygen atoms

The results of investigations of thermoluminescence dynamics during destruction of neon–helium and krypton–helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton–helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra were found to increase simultaneously during destruction processes in the temperature range 1.5–15 K. Observation of the NO molecules provides clear evidence for chemical reactions in the nanoclusters comprising the sample at low temperatures. Destruction of neon–helium samples occurred in two stages. During the first stage the α-group of N atoms surrounded by Ne and N₂ molecules dominated the spectra. During the second stage, the spectra contained intense bands of N and O atoms stabilized in a molecular nitrogen matrix. The unusual characteristics of the thermoluminescence spectra were observed, and their changes were explained in terms of the shell structure of impurity nanoclusters which comprised the impurity–helium condensates

Interaction of desulfovibrio desulfuricans biofilms with stainless steel surface and its impact on bacterial metabolism

Aims: To study the influence of some metallic elements of stainless steel 304 (SS 304) on the development and activity of a sulfate-reducing bacterial biofilm, using as comparison a reference nonmetallic material polymethylmethacrylate (PMMA). Methods and Results: Desulfovibrio desulfuricans biofilms were developed on SS 304 and on a reference nonmetallic material, PMMA, in a flow cell system. Steady-state biofilms were metabolically more active on SS 304 than on PMMA. Activity tests with bacteria from both biofilms at steady state also showed that the doubling time was lower for bacteria from SS 304 biofilms. The influence of chromium and nickel, elements of SS 304 composition, was also tested on a cellular suspension of Des. desulfuricans. Nickel decreased the bacterial doubling time, while chromium had no significant effect. Conclusions: The following mechanism is hypothesized: a Des. desulfuricans biofilm grown on a SS 304 surface in anaerobic conditions leads to the weakening of the metal passive layer and to the dissolution in the bulk phase of nickel ions that have a positive influence on the sulfate-reducing bacteria metabolism. This phenomenon may enhance the biocorrosion process. Significance and Impact of the Study: A better understanding of the interactions between metallic surfaces such as stainless steel and bacteria commonly implied in the corrosion phenomena which is primordial to fight biocorrosion.Programme Praxis XXI; University of Santiago de Compostela

Extracting Br(omega->pi^+ pi^-) from the Time-like Pion Form-factor

We extract the G-parity-violating branching ratio Br(omega->pi^+ pi^-) from the effective rho-omega mixing matrix element Pi_{rho omega}(s), determined from e^+e^- -> pi^+ pi^- data. The omega->pi^+ pi^- partial width can be determined either from the time-like pion form factor or through the constraint that the mixed physical propagator D_{rho omega}^{mu nu}(s) possesses no poles. The two procedures are inequivalent in practice, and we show why the first is preferred, to find finally Br(omega->pi^+ pi^-) = 1.9 +/- 0.3%.Comment: 12 pages (published version

On the Degradation of Retained Austenite in Transformation Induced Plasticity Steel

© 2020, The Minerals, Metals & Materials Society and ASM International. A transformation-induced plasticity steel was thermomechanically processed and then transformed to bainite at an isothermal transformation temperature of 723 K for 1800 seconds, which exceeds the time required for completion of the bainite transformation. The formation of lenticular-shaped carbides with a triclinic lattice and internal substructure was found after thermomechanical processing. After 16 years of storage at room temperature, the decomposition of retained austenite into pearlite was observed for the first time at this temperature

Neutralino Dark Matter in a Class of Unified Theories

The cosmological significance of the neutralino sector is studied for a class of models in which electroweak symmetry breaking is seeded by a gauge singlet. Extensive use is made of the renormalisation group equations to significantly reduce the parameter space, by deriving analytic expressions for all the supersymmetry-breaking couplings in terms of the universal gaugino mass $m_{1/2}$, the universal scalar mass $m_0$ and the coupling $A$. The composition of the LSP is determined exactly below the W mass, no approximations are made for sfermion masses, and all particle exchanges are considered in calculating the annihilation cross-section; the relic abundance is then obtained by an analytic approximation. We find that in these models, stable neutralinos may make a significant contribution to the dark matter in the universe.Comment: 24 Pages, OUTP-92-10