Macdonald Index and Chiral Algebra

For any 4d N=2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. We conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type $(A_1, A_{2n})$ and $(A_1, D_{2n+1})$ where the chiral algebras are given by Virasoro and su(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.Comment: 25 pages, v2: major revision. Clarified the prescription to get the Macdonald grading; v3: corrected hyperlinks to the references. To appear in JHE

The Determinants of Labor Market Institutions: A Panel Data Study

This paper analyzes the argument that labor market institutions can be thought of devices for social insurance. It investigates the hypotheses that a country’s exposure to external risk and ethnic fractionalization are correlated with labor market institutions. Extreme bounds analysis with the panel data of 40 years indicates that there is no robust evidence of positive correlation between external risk and the structure of labor market institutions, while ethnic fractionalization is robust negatively correlated with the institutions.labor market institutions; external risk; ethnic fractionalization; extreme bounds analysis

N=1 Deformations and RG Flows of N=2 SCFTs

We study certain N=1 preserving deformations of four-dimensional N=2 superconformal field theories (SCFTs) with non-abelian flavor symmetry. The deformation is described by adding an N=1 chiral multiplet transforming in the adjoint representation of the flavor symmetry with a superpotential coupling, and giving a nilpotent vacuum expectation value to the chiral multiplet which breaks the flavor symmetry. This triggers a renormalization group flow to an infrared SCFT. Remarkably, we find classes of theories flow to enhanced N=2 supersymmetric fixed points in the infrared under the deformation. They include generalized Argyres-Douglas theories and rank-one SCFTs with non-abelian flavor symmetries. Most notably, we find renormalization group flows from the deformed conformal SQCDs to the $(A_1, A_n)$ Argyres-Douglas theories. From these "Lagrangian descriptions," we compute the full superconformal indices of the $(A_1, A_n)$ theories and find agreements with the previous results. Furthermore, we study the cases, including the $T_N$ and $R_{0,N}$ theories of class $\mathcal{S}$ and some of rank-one SCFTs, where the deformation gives genuine N=1 fixed points.Comment: 45 pages, v2: added a paragraph on SUSY enhancement from the index. Minor corrections. To appear in JHE

Why do Some Studies Show that Generous Unemployment Benefits Increase Unemployment Rates? A Meta-Analysis of Cross-Country Studies

This paper investigates the hypothesis that generous unemployment benefits give rise to high levels of unemployment by systematically reviewing 34 cross- country studies. In contrast to conventional literature surveys, I perform a meta-analysis which applies regression techniques to a set of results taken from the existing literature. The main finding is that the choice of the primary data and estimation method matter for the final outcome. The control variables in the primary studies also affect the results.meta-analysis; cross-country study; unemployment; benefits replacement rate; benefit duration

Impact of CARB\u27s Tailpipe Emission Standard Policy on CO2 Reduction among the US States

U.S.Environmental Protection Agency (EPA) set the nationwide emission standard policy, but each state in the U.S. has an option to follow the higher emission standard policy set by CARB (California Air Resources Board) in 2004. There are 14 “CARB states” that follow California’s more restrictive standards. The purpose of this paper is to examine the impact of CARB’s tailpipe emission standard policy. Using the panel dataset for 49 U.S. states over a 28-year study period (1987–2015), this paper found the long-term policy effect in reducing CO2 emission from CARB’s tailpipe standard, and its long-run effect is 5.4 times higher than the short-run effect. The equivalent policy effect of the CARB emission standard in CO2 reduction can be achieved by raising gasoline price by 145.43%. Also, if 26.0% of petroleum consumed for transportation is substituted by alternative clean fuels (natural gas or electricity), it will have a comparable policy effect in CO2 reduction. Findings in this study support to continue the collaborative efforts among the EPA, National Highway Traffic Safety Administration (NHTSA), and California in order to achieve the CO2 reduction goal set by CARB and adopted by the EPA in 2012. The packaged policy approach rooted in persistent public and political support is necessary for successful policy implementation

Defining and Evaluating Network Communities based on Ground-truth

Nodes in real-world networks organize into densely linked communities where edges appear with high concentration among the members of the community. Identifying such communities of nodes has proven to be a challenging task mainly due to a plethora of definitions of a community, intractability of algorithms, issues with evaluation and the lack of a reliable gold-standard ground-truth. In this paper we study a set of 230 large real-world social, collaboration and information networks where nodes explicitly state their group memberships. For example, in social networks nodes explicitly join various interest based social groups. We use such groups to define a reliable and robust notion of ground-truth communities. We then propose a methodology which allows us to compare and quantitatively evaluate how different structural definitions of network communities correspond to ground-truth communities. We choose 13 commonly used structural definitions of network communities and examine their sensitivity, robustness and performance in identifying the ground-truth. We show that the 13 structural definitions are heavily correlated and naturally group into four classes. We find that two of these definitions, Conductance and Triad-participation-ratio, consistently give the best performance in identifying ground-truth communities. We also investigate a task of detecting communities given a single seed node. We extend the local spectral clustering algorithm into a heuristic parameter-free community detection method that easily scales to networks with more than hundred million nodes. The proposed method achieves 30% relative improvement over current local clustering methods.Comment: Proceedings of 2012 IEEE International Conference on Data Mining (ICDM), 201