Skewness and Kurtosis as Indicators of Non-Gaussianity in Galactic Foreground Maps

Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non- Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the local properties of both maps are predominantly Gaussian. This result was expected for the SMICA map; that it also applies for the Haslam map is surprising. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.Comment: 15 pages, 7 figures, minor change, as published in JCA

The Short- and Long-Term Career Effects of Graduating in a Recession: Hysteresis and Heterogeneity in the Market for College Graduates

The standard neo-classical model of wage setting predicts short-term effects of temporary labor market shocks on careers and low costs of recessions for both more and less advantaged workers. In contrast, a vast range of alternative career models based on frictions in the labor market suggests that labor market shocks can have persistent effects on the entire earnings profile. This paper analyzes the long-term effects of graduating in a recession on earnings, job mobility, and employer characteristics for a large sample of Canadian college graduates with different predicted earnings using matched university-employer-employee data from 1982 to 1999, and uses its results to assess the importance of alternative career models. We find that young graduates entering the labor market in a recession suffer significant initial earnings losses that eventually fade, but after 8 to 10 years. We also document substantial heterogeneity in the costs of recessions and important effects on job mobility and employer characteristics, but small effects on time worked. These adjustment patterns are neither consistent with a neo-classical spot market nor a complete scarring effect, but could be explained by a combination of time intensive search for better employers and long-term wage contracting. All results are robust to an extensive sensitivity analysis including controls for correlated business cycle shocks after labor market entry, endogenous timing of graduation, permanent cohort differences, and selective labor force participation.

Monotone cellular automata in a random environment

In this paper we study in complete generality the family of two-state, deterministic, monotone, local, homogeneous cellular automata in $\mathbb{Z}^d$ with random initial configurations. Formally, we are given a set $\mathcal{U}=\{X_1,\dots,X_m\}$ of finite subsets of $\mathbb{Z}^d\setminus\{\mathbf{0}\}$, and an initial set $A_0\subset\mathbb{Z}^d$ of `infected' sites, which we take to be random according to the product measure with density $p$. At time $t\in\mathbb{N}$, the set of infected sites $A_t$ is the union of $A_{t-1}$ and the set of all $x\in\mathbb{Z}^d$ such that $x+X\in A_{t-1}$ for some $X\in\mathcal{U}$. Our model may alternatively be thought of as bootstrap percolation on $\mathbb{Z}^d$ with arbitrary update rules, and for this reason we call it $\mathcal{U}$-bootstrap percolation. In two dimensions, we give a classification of $\mathcal{U}$-bootstrap percolation models into three classes -- supercritical, critical and subcritical -- and we prove results about the phase transitions of all models belonging to the first two of these classes. More precisely, we show that the critical probability for percolation on $(\mathbb{Z}/n\mathbb{Z})^2$ is $(\log n)^{-\Theta(1)}$ for all models in the critical class, and that it is $n^{-\Theta(1)}$ for all models in the supercritical class. The results in this paper are the first of any kind on bootstrap percolation considered in this level of generality, and in particular they are the first that make no assumptions of symmetry. It is the hope of the authors that this work will initiate a new, unified theory of bootstrap percolation on $\mathbb{Z}^d$.Comment: 33 pages, 7 figure

The Short- and Long-Term Career Effects of Graduating in a Recession: Hysteresis and Heterogeneity in the Market for College Graduates

This paper analyzes the long-term effects of graduating in a recession on earnings, job mobility, and employer characteristics for a large sample of Canadian college graduates using matched university-employer-employee data from 1982 to 1999. The results are used to assess the role of job mobility and firm quality in the propagation of shocks for different groups in the labor market. We find that young graduates entering the labor market in a recession suffer significant initial earnings losses that, on average, eventually fade after 8 to 10 years. Labor market conditions at graduation affect firm quality and job mobility, which can account for 40-50% of losses and catch-up in our sample. We also document that higher skilled graduates suffer less from entry in a recession because they switch to better firms quickly. Lower skilled graduates are permanently affected by being down ranked to low-wage firms. These adjustment patterns are consistent with differential choices of intensity of search for better employers arising from comparative advantage and time-increasing search costs. All results are robust to an extensive sensitivity analysis including controls for correlated business cycle shocks after labor market entry, endogenous timing of graduation, permanent cohort differences, and selective labor force participation.job search, hysteresis, college graduates, cost of recessions

Budgetary Consolidation in EMU.

There is a general consensus that monetary stability in Economic and Monetary Union (EMU) requires sustainable public finances of the member states. But how can a sufficient degree of budgetary discipline be maintained in Stage three of EMU?To answer this question, this study provides an empirical analysis of the budgetary consolidations in the EU member states by carrying out an analysis of: the importance of the quality of the budgetary adjustment for the success of the consolidations; the anatomy of fiscal adjustment processes in the EMU member states during the 1990s; the quality of the budgetary institutions of the member states and the changes in these institutions that have occurred during the 1990s; the macroeconomic aspects of fiscal consolidations. The results of the analysis support the proposition that, in order to maintain a high degree of sustainability in Stage three of EMU, attention might shift away from the numerical criteria regarding overall deficits and debts, and focus more on the quality of fiscal adjustments and of the institutions governing public finances in the member states.national budgets, emu, economic and monetary union, public finances

A (Bounded) Bestiary of Feynman Integral Calabi-Yau Geometries

We define the rigidity of a Feynman integral to be the smallest dimension over which it is non-polylogarithmic. We argue that massless Feynman integrals in four dimensions have a rigidity bounded by 2(L-1) at L loops, and we show that this bound may be saturated for integrals that we call marginal: those with (L+1)D/2 propagators in (even) D dimensions. We show that marginal Feynman integrals in D dimensions generically involve Calabi-Yau geometries, and we give examples of finite four-dimensional Feynman integrals in massless $\phi^4$ theory that saturate our predicted bound in rigidity at all loop orders.Comment: 5+2 pages, 11 figures, infinite zoo of Calabi-Yau manifolds. v2 reflects minor changes made for publication. This version is authoritativ

Bootstrapping a Five-Loop Amplitude Using Steinmann Relations

The analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.Comment: 5 pages, 2 figures, 1 impressive table, and 2 ancillary files. v2: a few clarifications and references added; version to appear in PR