Flexibility at the margin and labor market volatility in OECD countries

We argue that segmented labor markets with flexibility at the margin (e.g., just affecting fixed-term employees) may achieve similar volatility than fully deregulated labor markets. Flexibility at the margin produces a gap in separation costs among matched workers that cause fixed-term employment to be the main workforce adjustment device. Moreover, in the presence of limitations in the duration and number of renewals of fixed-term contracts, firms respond by fostering labor turnover which further raises the volatility of the labor market. We present a matching model with temporary and permanent jobs where (i) the gap in firing costs and (ii) restrictions in the use of fixedterm contracts play the central role to explain the similar volatility observed in many regulated labor markets with flexibility at the margin vis-à-vis the fully deregulated ones

Comment on "Topological stability of the half-vortices in spinor exciton-polariton condensates"

We show that recent paper by Flayac et al. [Phys. Rev. B 81, 045318 (2010) and arXiv:0911.1650] is misleading. We demonstrate the existence of static half-quantum vortices in exciton-polariton condensates and calculate the warping of their polarization texture produced by TE-TM splitting of polariton band.Comment: 4 pages, 1 figure. More material was added (in particular, on the current flow)

Flexibility at the Margin and Labor Market Volatility in OECD Countries

We study whether segmented labor markets with flexibility at the margin (e.g., just affecting fixed-term employees) can achieve similar volatility than fully deregulated labor markets. Flexibility at the margin produces a gap in separation costs among matched workers that cause fixed-term employment to be the main workforce adjustment device, which in turn increases de labor market volatility. This increased volatility is partially reverted when limitations in the duration and number of renewals of fixed-term contracts are introduced. Under this scenario, firms respond by reducing the intensity of job destruction since it becomes more difficult to avoid firing costs in permanents contracts. We present a matching model with temporary and permanent jobs where (i) the gap in firing costs and (ii) restrictions in the use of fixed-term contracts helps explain the similar volatility observed in many regulated OECD labor markets with flexibility at the margin vis-à-vis the fully deregulated ones.separation costs, volatility, flexibility at the margin, matching model

Flexibility at the margin and labor market volatility in OECD countries

We argue that segmented labor markets with flexibility at the margin (e.g., just affecting fixed-term employees) may achieve similar volatility than fully deregulated labor markets. Flexibility at the margin produces a gap in separation costs among matched workers that cause fixed-term employment to be the main workforce adjustment device. Moreover, in the presence of limitations in the duration and number of renewals of fixed-term contracts, firms respond by fostering labor turnover which further raises the volatility of the labor market. We present a matching model with temporary and permanent jobs where (i) the gap in firing costs and (ii) restrictions in the use of fixedterm contracts play the central role to explain the similar volatility observed in many regulated labor markets with flexibility at the margin vis-à-vis the fully deregulated ones.

Upper Bound on the Hadronic Light-by-Light Contribution to the Muon g-2

There are indications that hadronic loops in some electroweak observables are almost saturated by parton level effects. Taking this as the hypothesis for this work, we propose a genuine parton level estimate of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, a_mu (LBL,had). Our quark mass definitions and values are motivated in detail, and the simplicity of our approach allows for a transparent error estimate. For infinitely heavy quarks our treatment is exact, while for asymptotically small quark masses a_mu (LBL,had) is overestimated. Interpolating, this suggests quoting an upper bound. We obtain a_mu (LBL,had) < 1.59 10^-9 (95% CL).Comment: 4 pages; 2 references added, some changes in text; final versio

Color screening in a constituent quark model of hadronic matter

The effect of color screening on the formation of a heavy quark-antiquark ($Q\bar{Q}$) bound state--such as the $J/\psi$ meson--is studied using a constituent-quark model. The response of the nuclear medium to the addition of two color charges is simulated directly in terms of its quark constituents via a string-flip potential that allows for quark confinement within hadrons yet enables the hadrons to separate without generating unphysical long-range forces. Medium modifications to the properties of the heavy meson, such as its energy and its mean-square radius, are extracted by solving Schr\"odinger's equation for the $Q\bar{Q}$ pair in the presence of a (screened) density-dependent potential. The density dependence of the heavy-quark potential is in qualitative agreement with earlier studies of its temperature dependence extracted from lattice calculations at finite temperature. In the present model it is confirmed that abrupt changes in the properties of the $J/\psi$-meson in the hadronic medium ({\it plasma}), correlate strongly with the deconfining phase transition.Comment: 7 pages, 3 figures, submitted to PRC for publication, uses revtex

Vortices in exciton-polariton condensates with polarization splitting

The presence of polarization splitting of exciton-polariton branches in planar semiconductor microcavities has a pronounced effect on vortices in polariton condensates. We show that the TE-TM splitting leads to the coupling between the left and right half-vortices (vortices in the right and left circular components of the condensate), that otherwise do not interact. We analyze also the effect of linear polarization pinning resulted from a fixed splitting between two perpendicular linear polarizations. In this case, half-vortices acquire strings (solitons) attached to them. The half-vortices with strings can be detected by observing the interference fringes of light emitted from the cavity in two circular polarizations. The string affects the fringes in both polarizations. Namely, the half-vortex is characterized by an asymmetric fork-like dislocation in one circular polarization; the fringes in the other circular polarization are continuous, but they are shifted by crossing the string.Comment: 4 pages, 2 figs, Optics of Excitons in Confined Systems 11 (Madrid, 7-11 september 2009