A finer view of the conditional galaxy luminosity function and magnitude-gap statistics

The gap between first and second ranked galaxy magnitudes in groups is often considered a tracer of their merger histories, which in turn may affect galaxy properties, and also serves to test galaxy luminosity functions (LFs). We remeasure the conditional luminosity function (CLF) of the Main Galaxy Sample of the SDSS in an appropriately cleaned subsample of groups from the Yang catalog. We find that, at low group masses, our best-fit CLF have steeper satellite high ends, yet higher ratios of characteristic satellite to central luminosities in comparison with the CLF of Yang et al. (2008). The observed fractions of groups with large and small magnitude gaps as well as the Tremaine & Richstone (1977) statistics, are not compatible with either a single Schechter LF or with a Schechter-like satellite plus lognormal central LF. These gap statistics, which naturally depend on the size of the subsamples, and also on the maximum projected radius, $R_{\rm max}$, for defining the 2nd brightest galaxy, can only be reproduced with two-component CLFs if we allow small gap groups to preferentially have two central galaxies, as expected when groups merge. Finally, we find that the trend of higher gap for higher group velocity dispersion, $\sigma_{\rm v}$, at given richness, discovered by Hearin et al. (2013), is strongly reduced when we consider $\sigma_{\rm v}$ in bins of richness, and virtually disappears when we use group mass instead of $\sigma_{\rm v}$. This limits the applicability of gaps in refining cosmographic studies based on cluster counts.Comment: 18 pages, 13 figures, 5 tables, submitted to MNRAS, comments are welcom

Path Dependence of the Quark Nonlocal Condensate within the Instanton Model

Within the instanton liquid model, we study the dependence of the gauge invariant two--point quark correlator on the path used to perform the color parallel transport between two points in the Euclidean space.Comment: 4 pages, 5 figure

Revisiting the two-mass model of the vocal folds

Realistic mathematical modeling of voice production has been recently boosted by applications to different fields like bioprosthetics, quality speech synthesis and pathological diagnosis. In this work, we revisit a two-mass model of the vocal folds that includes accurate fluid mechanics for the air passage through the folds and nonlinear properties of the tissue. We present the bifurcation diagram for such a system, focusing on the dynamical properties of two regimes of interest: the onset of oscillations and the normal phonation regime. We also show theoretical support to the nonlinear nature of the elastic properties of the folds tissue by comparing theoretical isofrequency curves with reported experimental data.Comment: 7 pages, 5 figure

Controlling instabilities along a 3DVar analysis cycle by assimilating in the unstable subspace: a comparison with the EnKF

A hybrid scheme obtained by combining 3DVar with the Assimilation in the Unstable Subspace (3DVar-AUS) is tested in a QG model, under perfect model conditions, with a fixed observational network, with and without observational noise. The AUS scheme, originally formulated to assimilate adaptive observations, is used here to assimilate the fixed observations that are found in the region of local maxima of BDAS vectors (Bred vectors subject to assimilation), while the remaining observations are assimilated by 3DVar. The performance of the hybrid scheme is compared with that of 3DVar and of an EnKF. The improvement gained by 3DVar-AUS and the EnKF with respect to 3DVar alone is similar in the present model and observational configuration, while 3DVar-AUS outperforms the EnKF during the forecast stage. The 3DVar-AUS algorithm is easy to implement and the results obtained in the idealized conditions of this study encourage further investigation toward an implementation in more realistic contexts