7,833 research outputs found
Different critical points of chiral and deconfinement phase transitions in (2+1)-dimensional fermion-gauge interacting model
Based on the truncated Dyson-Schwinger equations for fermion and massive
boson propagators in QED, the fermion chiral condensate and the mass
singularities of the fermion propagator via the Schwinger function are
investigated. It is shown that the critical point of chiral phase transition is
apparently different from that of deconfinement phase transition and in Nambu
phase the fermion is confined only for small gauge boson mass.Comment: 5 Pages and 3 figure
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Immigration System, Labor Market Structures, and Overeducation of High-Skilled Immigrants in the United States and Canada
Why do high-skilled Canadian immigrants lag behind their US counterparts in labor-market outcomes despite Canada’s merit-based immigration selection system and more integrative context? This article investigates a mismatch between immigrants' education and occupations, operationalized by overeducation, as an explanation. Using comparable data and three measures of overeducation, we find that university-educated immigrant workers in Canada are consistently much more likely to be overeducated than their US peers and that the immigrant-native gap in the overeducation rate is remarkably higher in Canada than in the United States. This article further examines how the cross-national differences are related to labor-market structures and selection mechanisms for immigrants. Whereas labor-market demand reduces the likelihood of overeducation in both countries, the role of supply-side factors varies: a higher supply of university-educated immigrants is positively associated with the likelihood of overeducation in Canada but not in the United States, pointing to an oversupply of high-skilled immigrants relative to Canada’s smaller economy. Also, in Canada the overeducation rate is significantly lower for immigrants who came through employer selection (i.e., those who worked in Canada before obtaining permanent residence) than for those admitted directly from abroad through the point system. Overall, the findings suggest that a merit-based immigration system likely works better when it takes into consideration domestic labor-market demand and the role of employer selection
General formula for the four-quark condensate and vacuum factorization assumption
By differentiating the dressed quark propagator with respect to a variable
background field, the linear response of the dressed quark propagator in the
presence of the background field can be obtained. From this general method,
using the vector background field as an illustration, we derive a general
formula for the four-quark condensate . This formula contains the
corresponding fully dressed vector vertex and it is shown that factorization
for holds only when the dressed vertex is taken to be the bare one.
This property also holds for all other type of four-quark condensate.Comment: Revtex4, 11 pages, no figure
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