7,131 research outputs found
Colors and magnitudes of quasar host galaxies at high redshift
We discuss the results so far of a program to image in the rest-frame optical and near-UV the host galaxies of a sample of 5 high redshift (z ~ 2–3) radio-quiet quasars with nuclear luminosities lower than most samples studied at high z. We found that in the rest-frame optical the hosts have luminosities of about L*, comparable to the Lyman break galaxies at similar redshifts. From the rest-frame UV imaging, we can derive optical–UV colors, and find they show a great deal of variation, but may be somewhat redder and less starforming than the LBGs. We are supplementing this work at high z with study of the hosts of z ~ 1 radio-quiet quasars with similar low nuclear luminosities
Hyperbolic Structures and Root Systems
We discuss the construction of a one parameter family of complex hyperbolic
structures on the complement of a toric mirror arrangement associated with a
simply laced root system. Subsequently we find conditions for which parameter
values this leads to ball quotients
New Methods for Estimating Labor Supply Functions: A Survey
This paper surveys new methods for estimatifg labor supply functions. A unified framework of analysis is presented. All recent models of labor supply are special cases of a general index function model developed for the analysis o dummy endogenous variables.
A Note on Adapting Propensity Score Matching and Selection Models to Choice Based Samples
The probability of selection into treatment plays an important role in matching and selection models. However, this probability can often not be consistently estimated, because of choice-based sampling designs with unknown sampling weights. This note establishes that the selection and matching procedures can be implemented using propensity scores fit on choice-based samples with misspecified weights, because the odds ratio of the propensity score fit on the choice-based sample is monotonically related to the odds ratio of the true propensity scores.choice-based sampling, matching models, propensity scores, selection models
Grand Unified Yukawa Matrix Ansatz: The Standard Model Fermion Mass, Quark Mixing and CP Violation Parameters
We propose a new mass matrix ansatz: At the grand unified (GU) scale, the
standard model (SM) Yukawa coupling matrix elements are integer powers of the
square root of the GU gauge coupling constant \varepsilon \equiv
\sqrt{\alpha_{\text{GU}}}, multiplied by order unity random complex numbers. It
relates the hierarchy of the SM ermion masses and quark mixings to the gauge
coupling constants, greatly reducing the SM parameters, and can give good
fitting results of the SM fermion mass, quark mixing and CP violation
parameters. This is a neat but very effective ansatz.Comment: 4 pages (two columns), by REVTeX 4, 2 tables, no figures, version for
publication in CP
Earnings Functions and Rates of Return
The internal rate of return to schooling is a fundamental economic parameter that is often used to assess whether expenditure on education should be increased or decreased. This paper considers alternative approaches to estimating marginal internal rates of return for different schooling levels. We implement a general nonparametric approach to estimate marginal internal rates of return that take into account tuition costs, income taxes and nonlinearities in the earnings-schooling-experience relationship. The returns obtained by the more general method differ substantially from Mincer returns in levels and in their evolution over time. They indicate relatively larger returns to graduating from high school than from graduating from college, although both have been increasing over time.schooling, marginal internal rate of return, nonparametric estimation
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