Estimating Residual Faults from Code Coverage

Many reliability prediction techniques require an estimate for the number of residual faults. In this paper, a new theory is developed for using test coverage to estimate the number of residual faults. This theory is applied to a specific example with known faults and the results agree well with the theory. The theory is used to justify the use of linear extrapolation to estimate residual faults. It is also shown that it is important to establish the amount of unreachable code in order to make a realistic residual fault estimate

Optimal Strategies for Prudent Investors

We consider a stochastic model of investment on an asset of a stock market for a prudent investor. She decides to buy permanent goods with a fraction \a of the maximum amount of money owned in her life in order that her economic level never decreases. The optimal strategy is obtained by maximizing the exponential growth rate for a fixed \a. We derive analytical expressions for the typical exponential growth rate of the capital and its fluctuations by solving an one-dimensional random walk with drift.Comment: 14 pages, LaTeX, epsfig.sty, 7 eps figures, minor changes; accepted for International J. of Theoretical and Applied Financ

The Be-test in the Li-rich star \#1657 of NGC 6397: evidence for Li-flash in RGB stars?

The Li-rich turn-off star in the globular cluster NGC 6397 could represent the smoking gun for some very rare episode of Li enrichment in globular clusters. We aim to understand the nature of the Li enrichment by performing a spectroscopic analysis of the star, in particular of its beryllium (Be) abundance, and by investigating its binary nature. We observe the near UV region where the Beii resonance doublet and the NH bands are located. We could not detect the Beii lines and derive an upper limit of log (Be/H)< -12.2, that is consistent with the Be observed in other stars of the cluster. We could detect a weak G-band, which implies a mild carbon enhancement [C/Fe]$+0.4\pm0.2$. We could not detect the UV NH band, and we derive an upper limit [N/Fe]$< 0.0$. For oxygen we could notdetect any of the near UV OH lines, which implies that oxygen cannot be strongly enhanced in this star. This is consistent with the detection of the Oi triplet at 777nm, which is consistent with [O/Fe]~0.5. Combining the UVES and Mike data, we could not detect any variation in the radial velocity greater than 0.95 kms$^{-1}$ over 8 years. The chemical composition of the star strongly resembles that of `first generation' NGC6397 stars, with the huge Li as the only deviating abundance. Not detecting Be rules out two possible explanations of the Li overabundance: capture of a substellar body and spallation caused by a nearby type II SNe. Discrepancies are also found with respect to other accretion scenarios,except for contamination by the ejecta of a star that has undergone the RGB Li-flash.Comment: Accepted for publication in A&

Azimuthal spin asymmetries in light-cone constituent quark models

We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with available experimental data and present predictions to be further tested by future CLAS, COMPASS and HERMES data.Comment: 23 pages, 14 figures, 1 tabl

Testing LCDM with the Growth Function \delta(a): Current Constraints

We have compiled a dataset consisting of 22 datapoints at a redshift range (0.15,3.8) which can be used to constrain the linear perturbation growth rate f=\frac{d\ln\delta}{d\ln a}. Five of these data-points constrain directly the growth rate f through either redshift distortions or change of the power spectrum with redshift. The rest of the datapoints constrain f indirectly through the rms mass fluctuation \sigma_8(z) inferred from Ly-\alpha at various redshifts. Our analysis tests the consistency of the LCDM model and leads to a constraint of the Wang-Steinhardt growth index \gamma (defined from f=\Omega_m^\gamma) as \gamma=0.67^{+0.20}_{-0.17}. This result is clearly consistent at $1\sigma$ with the value \gamma={6/11}=0.55 predicted by LCDM. A first order expansion of the index \gamma in redshift space leads to similar results.We also apply our analysis on a new null test of LCDM which is similar to the one recently proposed by Chiba and Nakamura (arXiv:0708.3877) but does not involve derivatives of the expansion rate $H(z)$. This also leads to the fact that LCDM provides an excellent fit to the current linear growth data.Comment: 7 pages, 4 figures. Added comments on the data of Table I (after eq. (2.16)). Corrected a typo on eq. (2.15). The mathematica files with the numerical analysis of this study may be found at http://nesseris.physics.uoi.gr/growth/growth.ht

TMDs and Azimuthal Spin Asymmetries in a Light-Cone Quark Model

The main properties of the leading-twist transverse momentum dependent parton distributions in a light-cone constituent quark model of the nucleon are reviewed, with focus on the role of the spin-spin and spin-orbit correlations of quarks. Results for azimuthal single spin asymmetries in semi-inclusive deep inelastic scattering are also discussed.Comment: Proceedings of SPIN2008, 6-11 October 2008, Charlottesville, VA, US

Transverse momentum dependent parton distributions and azimuthal asymmetries in light-cone quark models

We review the information on the spin and orbital angular momentum structure of the nucleon encoded in the T-even transverse momentum dependent parton distributions within light-cone quark models. Model results for azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering are discussed, showing a good agreement with available experimental data and providing predictions to be further tested by future CLAS, COMPASS and HERMES data.Comment: 6 pages, 4 figures; proceedings of the "XIII Workshop On High Energy Spin Physics Dubna Spin 2009", 1-5 September 2009, Dubna, Russi

Beaming Binaries - a New Observational Category of Photometric Binary Stars

The new photometric space-borne survey missions CoRoT and Kepler will be able to detect minute flux variations in binary stars due to relativistic beaming caused by the line-of-sight motion of their components. In all but very short period binaries (P>10d), these variations will dominate over the ellipsoidal and reflection periodic variability. Thus, CoRoT and Kepler will discover a new observational class: photometric beaming binary stars. We examine this new category and the information that the photometric variations can provide. The variations that result from the observatory heliocentric velocity can be used to extract some spectral information even for single stars.Comment: 15 pages, 4 figures, accpeted for publication in The Astrophysical Journa