The exterior degree of a pair of finite groups

The exterior degree of a pair of finite groups $(G,N)$, which is a generalization of the exterior degree of finite groups, is the probability for two elements $(g,n)$ in $(G,N)$ such that $g\wedge n=1$. In the present paper, we state some relations between this concept and the relative commutatively degree, capability and the Schur multiplier of a pair of groups.Comment: To appear in Mediterr. J. Mat

Effects of crosstalk in WDM optical label switching networks due to wavelength switching of a tunable laser

rosstalk caused by switching events in fast tunable lasers in an optical label switching (OLS) system is investigated for the first time. A wavelength-division-multiplexed OLS system based on subcarrier multiplexed labels is presented which employs a 40-Gb/s duobinary payload and a 155-Mb/s label on a 40-GHz subcarrier. Degradation in system performance as the transmitters switch between different channels is then characterized in terms of the frequency drift of the tunable laser

Time-resolved linewidth measurements of a wavelength switched SG-DBR laser for optical packet switched networks

We report time-resolved linewidth measurements of different sizes of optical packets under wavelength-switching for the first time and show that laser linewidth is significantly broadened during switching transition requiring ~3 mus to attain its minimum value

Cost efficient narrow linewidth laser transmitter for coherent detection

Authors present a cost efficient narrow linewidth laser transmitter for future coherent detection systems. The spectral purity of the laser allows the phase modulation of data signals at bit rates as low as 155 Mb/s

On Anomaly-free Supergravity as an Effective String Theory

The equations of motion of anomaly-free supergravity are shown to fulfil (to all orders in $\alpha'$) a differential condition corresponding to the one relating the Weyl anomaly coefficients for a non-linear sigma model representing a (heterotic) string propagating in a non-trivial background. This supports the possibility that anomaly-free supergravity could provide the complete massless effective theory for the heterotic string.Comment: 7 pages, Latex, CERN-TH.6686/9

SCM optical label switching scheme in a WDM packet transmitter employing a switching SG-DBR laser

We demonstrate an SCM optical label switching scheme with spectral efficiency of 0.4bit/s/Hz and a spectral density figure of merit of 1. We then employ this scheme in a WDM transmitter subsystem and we investigate the detrimental effects that switching events in tunable lasers can have on such systems. The label performance is shown to hit an error floor when the tunable laser switches channels and this would cause incorrect routing of packets. The bit error rate is time resolved in order to better understand the problem and some possible solutions are discussed

Aspects of meson properties in dense nuclear matter

We investigate the modification of meson spectral densities in dense nuclear matter at zero temperature. These effects are studied in a fully relativistic mean field model which goes beyond the linear density approximation and also includes baryon resonances. In particular, the role of N*(1520) and N*(1720) on the rho meson spectral density is highlighted. Even though the nucleon-nucleon loop and the nucleon-resonance loop contribute with the opposite sign, an overall reduction of rho meson mass is still observed at high density. Importantly, it is shown that the resonances cause substantial broadening of the rho meson spectral density in matter and also induces non-trivial momentum dependence. The spectral density of the a0 meson is also shown. We study the dispersion relations and collective oscillations induced by the rho meson propagation in nuclear matter together with the influence of the mixing of rho with the a0 meson. The relevant expression for the plasma frequency is also recovered analytically in the appropriate limit.Comment: 19 pages, 17 figure

Effect of FCNC mediated Z boson on lepton flavor violating decays

We study the three body lepton flavor violating (LFV) decays $\mu^- \to e^- e^+ e^-$, $\tau^- \to l_i^- l_j^+ l_j^-$ and the semileptonic decay $\tau \to \mu \phi$ in the flavor changing neutral current (FCNC) mediated $Z$ boson model. We also calculate the branching ratios for LFV leptonic B decays, $B_{d,s} \to \mu e$, $B_{d,s} \to \tau e$, $B_{d,s} \to \tau \mu$ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on $\mu^- \to e^- e^+ e^-$ and $\tau^- \to \mu^- \mu^+ \mu^-$. We find that the branching ratios for $\tau \to eee$ and $\tau \to \mu \phi$ processes could be as large as $\sim {\cal O}(10^{-8})$ and ${\rm Br}B_{d,s} \to \tau \mu, \tau e) \sim {\cal O}(10^{-10})$. For other LFV B decays the branching ratios are found to be too small to be observed in the near future.Comment: 15 pages, 8 figures, typos corrected, one more section added, version to appear in EPJ

Archaeological Landscapes during the 10–8 ka Lake Stanley Lowstand on the Alpena‐Amberley Ridge, Lake Huron

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136243/1/gea21590.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136243/2/gea21590_am.pd

LIMITS ON ANISOTROPY AND INHOMOGENEITY FROM THE COSMIC BACKGROUND RADIATION,

We consider directly the equations by which matter imposes anisotropies on freely propagating background radiation, leading to a new way of using anisotropy measurements to limit the deviations of the Universe from a Friedmann-Robertson-Walker (FRW) geometry. This approach is complementary to the usual Sachs-Wolfe approach: the limits obtained are not as detailed, but they are more model-independent. We also give new results about combined matter-radiation perturbations in an almost-FRW universe, and a new exact solution of the linearised equations.Comment: 18 pages Latex