ON THE OSCILLATION SPECTRA OF ULTRA COMPACT STARS

Quasinormal modes of ultra compact stars with uniform energy density have been calculated. For less compact stars, there is only one very slowly damped polar mode (corresponding to the Kelvin f-mode) for each spherical harmonic index $l$. Further long-lived modes become possible for a sufficiently compact star (roughly when $M/R \ge 1/3$). We compare the characteristic frequencies of these resonant polar modes to the axial modes first found by Chandrasekhar and Ferrari [{\em Proc. Roy. Soc. London A} {\bf 434} 449 (1991)]. We find that the two spectra approach each other as the star is made more compact. The oscillation frequencies of the corresponding polar and axial modes agree to within a percent for stars more compact than $M/R = 0.42$. At the same time, the damping times are slightly different. The results illustrate that there is no real difference between the origin of these axial and polar modes: They are essentially spacetime modes.Comment: 13 pages, LATEX format, 25Kb, 2 postscript figures, Proc. Roy. Soc. London in pres

Resonant growth of stellar oscillations by incident gravitational waves

Stellar oscillation under the combined influences of incident gravitational wave and radiation loss is studied in a simple toy model. The star is approximated as a uniform density ellipsoid in the Newtonian gravity including radiation damping through quadrupole formula. The time evolution of the oscillation is significantly controlled by the incident wave amplitude $h$, frequency $\nu$ and damping time $\tau$. If a combination $h \nu \tau$ exceeds a threshold value, which depends on the resonance mode, the resonant growth is realized.Comment: 11 pages, 6 figures, Accepted for the publication in Classical and Quantum Gravit

Cloning, expression, crystallization and preliminary X-ray crystallographic analysis of a human condensin SMC2 hinge domain with short coiled coils

Kawahara, K., Nakamura, S., Katsu, Y., Motooka, D., Hosokawa, Y., Kojima, Y., Matsukawa, K., Takinowaki, H., Uchiyama, S., Kobayashi, Y., Fukui, K. & Ohkubo, T. (2010). Acta Cryst. F66, 1067-1070

The Riemann-Hilbert problem associated with the quantum Nonlinear Schrodinger equation

We consider the dynamical correlation functions of the quantum Nonlinear Schrodinger equation. In a previous paper we found that the dynamical correlation functions can be described by the vacuum expectation value of an operator-valued Fredholm determinant. In this paper we show that a Riemann-Hilbert problem can be associated with this Fredholm determinant. This Riemann-Hilbert problem formulation permits us to write down completely integrable equations for the Fredholm determinant and to perform an asymptotic analysis for the correlation function.Comment: 21 pages, Latex, no figure

Data dependent energy modelling for worst case energy consumption analysis

Safely meeting Worst Case Energy Consumption (WCEC) criteria requires accurate energy modeling of software. We investigate the impact of instruction operand values upon energy consumption in cacheless embedded processors. Existing instruction-level energy models typically use measurements from random input data, providing estimates unsuitable for safe WCEC analysis. We examine probabilistic energy distributions of instructions and propose a model for composing instruction sequences using distributions, enabling WCEC analysis on program basic blocks. The worst case is predicted with statistical analysis. Further, we verify that the energy of embedded benchmarks can be characterised as a distribution, and compare our proposed technique with other methods of estimating energy consumption

A study of 15N14N isotopic exchange over cobalt molybdenum nitrides

The 14N/15N isotopic exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic exchange processes have been studied, and it has been shown that lattice nitrogen species are exchangeable. The exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being exchanged after 40 min at 600 °C after N2 pretreatment at 700 °C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under 15N2 at 600 °C occurs concurrently with 14N15N formation. These observations demonstrate the reactivity of nitrogen in the Co–Mo–N system to be a strong function of pretreatment and worthy of further consideration

Flavor-oscillation clocks, continuous quantum measurements and a violation of Einstein equivalence principle

The relation between Einstein equivalence principle and a continuous quantum measurement is analyzed in the context of the recently proposed flavor-oscillation clocks, an idea pioneered by Ahluwalia and Burgard (Gen. Rel Grav. Errata 29, 681 (1997)). We will calculate the measurement outputs if a flavor-oscillation clock, which is immersed in a gravitational field, is subject to a continuous quantum measurement. Afterwards, resorting to the weak equivalence principle, we obtain the corresponding quantities in a freely falling reference frame. Finally, comparing this last result with the measurement outputs that would appear in a Minkowskian spacetime it will be found that they do not coincide, in other words, we have a violation of Einstein equivalence principle. This violation appears in two different forms, namely: (i) the oscillation frequency in a freely falling reference frame does not match with the case predicted by general relativity, a feature previously obtained by Ahluwalia; (ii) the probability distribution of the measurement outputs, obtained by an observer in a freely falling reference frame, does not coincide with the results that would appear in the case of a Minkowskian spacetime.Comment: 16 pages, accepted in Mod. Phys. Letts.

Magnetic Phase Transitions in the double spin-chains compound LiCu2O2\rm LiCu_2O_2

We report high-resolution x-ray diffraction, muon-spin-rotation spectroscopic and specific heat measurements in the double spin-chains compound $\rm LiCu_2O_2$. The x-ray diffraction results show that the crystal structure of $\rm LiCu_2O_2$ ~is orthorhombic down to T=10K. Anisotropic line-broadening of the diffraction peaks is observed, indicating disorder along the spin chains. Muon spin relaxation and specific heat measurements show that $\rm LiCu_2O_2$ \~undergoes a phase transition to a magnetic ordered state at $\rm T_1\sim24K$. The specific heat data exhibits a second $\rm \lambda$-like peak at $\rm T_2\sim22.5 K$, which increases with increasing magnetic field similarly way to that found in spin-ladder compounds.Comment: 6 pages, 6 fifures, to appear in Physica

On the r-mode spectrum of relativistic stars

We present a mathematically rigorous proof that the r-mode spectrum of relativistic stars to the rotational lowest order has a continuous part. A rigorous definition of this spectrum is given in terms of the spectrum of a continuous linear operator. This study verifies earlier results by Kojima (1998) about the nature of the r-mode spectrum.Comment: 6 pages, no figure