China's Higher Education Expansion and its Labor Market Consequences

Using a 1/5 random draw of the 1% census of 2005, we investigate how China’s higher education expansion commenced in 1999 affects the education opportunities of various population groups and how this policy affects the labor market. Treating the expansion as an experiment and using a LATE framework, we find that higher education expansion increased the probability of go to college tremendously. Different populations “benefit” from this policy differently however. Minority female, those from central-western region and from rural areas are less likely to benefit from it. One-child families are more responsive to this policy. Using higher education resources at the provincial level as another dimension of variation, and using a difference-in-difference strategy, we find that the education expansion decreased the within sector inequality of population with above high school (inclusive) education. This is primarily due to the increase of the income level for high school graduate. That of the college graduate deceased, but only slightly and not significantly.China, higher education expansion, LATE, difference in difference, income level

The fluctuations of the giant cluster for percolation on random split trees

A split tree of cardinality $n$ is constructed by distributing $n$ "balls" in a subset of vertices of an infinite tree which encompasses many types of random trees such as $m$-ary search trees, quad trees, median-of-$(2k+1)$ trees, fringe-balanced trees, digital search trees and random simplex trees. In this work, we study Bernoulli bond percolation on arbitrary split trees of large but finite cardinality $n$. We show for appropriate percolation regimes that depend on the cardinality $n$ of the split tree that there exists a unique giant cluster, the fluctuations of the size of the giant cluster as $n \rightarrow \infty$ are described by an infinitely divisible distribution that belongs to the class of stable Cauchy laws. This work generalizes the results for the random $m$-ary recursive trees in Berzunza (2015). Our approach is based on a remarkable decomposition of the size of the giant percolation cluster as a sum of essentially independent random variables which may be useful for studying percolation on other trees with logarithmic height; for instance in this work we study also the case of regular trees.Comment: 43 page

Cosmological implications of modified gravity induced by quantum metric fluctuations

We investigate the cosmological implications of modified gravities induced by the quantum fluctuations of the gravitational metric. If the metric can be decomposed as the sum of the classical and of a fluctuating part, of quantum origin, then the corresponding Einstein quantum gravity generates at the classical level modified gravity models with a nonminimal coupling between geometry and matter. As a first step in our study, after assuming that the expectation value of the quantum correction can be generally expressed in terms of an arbitrary second order tensor constructed from the metric and from the thermodynamic quantities characterizing the matter content of the Universe, we derive the (classical) gravitational field equations in their general form. We analyze in detail the cosmological models obtained by assuming that the quantum correction tensor is given by the coupling of a scalar field and of a scalar function to the metric tensor, and by a term proportional to the matter energy-momentum tensor. For each considered model we obtain the gravitational field equations, and the generalized Friedmann equations for the case of a flat homogeneous and isotropic geometry. In some of these models the divergence of the matter energy-momentum tensor is non-zero, indicating a process of matter creation, which corresponds to an irreversible energy flow from the gravitational field to the matter fluid, and which is direct consequence of the nonminimal curvature-matter coupling. The cosmological evolution equations of these modified gravity models induced by the quantum fluctuations of the metric are investigated in detail by using both analytical and numerical methods, and it is shown that a large variety of cosmological models can be constructed, which, depending on the numerical values of the model parameters, can exhibit both accelerating and decelerating behaviors.Comment: 21 pages, 11 figures, accepted for publication in EPJ

Isospin symmetry breaking of K and K* mesons

We use the method of QCD sum rules to investigate the isospin symmetry breaking of K and K* mesons. The electromagnetic effect, difference between up and down current-quark masses and difference between up and down quark condensates are important. We perform sum rule analyses of their masses and decay constant differences, which are consistent with experimental values. Our results yield Delta f_K = f_{K^0} - f_{K^\pm} = 1.5 MeV.Comment: 9 pages, 7 figures, one reference adde