Massive scalar fields in the early Universe

We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003), Olinda-PE, Brazi

Adversarial Robustness: Softmax versus Openmax

Deep neural networks (DNNs) provide state-of-the-art results on various tasks and are widely used in real world applications. However, it was discovered that machine learning models, including the best performing DNNs, suffer from a fundamental problem: they can unexpectedly and confidently misclassify examples formed by slightly perturbing otherwise correctly recognized inputs. Various approaches have been developed for efficiently generating these so-called adversarial examples, but those mostly rely on ascending the gradient of loss. In this paper, we introduce the novel logits optimized targeting system (LOTS) to directly manipulate deep features captured at the penultimate layer. Using LOTS, we analyze and compare the adversarial robustness of DNNs using the traditional Softmax layer with Openmax, which was designed to provide open set recognition by defining classes derived from deep representations, and is claimed to be more robust to adversarial perturbations. We demonstrate that Openmax provides less vulnerable systems than Softmax to traditional attacks, however, we show that it can be equally susceptible to more sophisticated adversarial generation techniques that directly work on deep representations.Comment: Accepted to British Machine Vision Conference (BMVC) 201

Are Accuracy and Robustness Correlated?

Machine learning models are vulnerable to adversarial examples formed by applying small carefully chosen perturbations to inputs that cause unexpected classification errors. In this paper, we perform experiments on various adversarial example generation approaches with multiple deep convolutional neural networks including Residual Networks, the best performing models on ImageNet Large-Scale Visual Recognition Challenge 2015. We compare the adversarial example generation techniques with respect to the quality of the produced images, and measure the robustness of the tested machine learning models to adversarial examples. Finally, we conduct large-scale experiments on cross-model adversarial portability. We find that adversarial examples are mostly transferable across similar network topologies, and we demonstrate that better machine learning models are less vulnerable to adversarial examples.Comment: Accepted for publication at ICMLA 201

What does it take to be a star? The role of performance and the media for German soccer players

We test existing superstar theories for the German soccer league. We use various measures for individual players’ performance and media presence to analyze whether performance and popularity can explain salaries and superstars in soccer. Moreover, we argue that quantile regression technique should be applied to analyze superstar phenomena instead of OLS used hitherto.Superstars, soccer, quantile regressions, Rosen, Adler

Urbanization and the Wealth of Nations

The proportion of a country's population living in urban areas is highly correlated with its level of income. Urban areas offer economies of scale and richer market structures, and there is strong evidence that workers in urban areas are individually more productive, and earn more, than rural workers. However, rapid urbanization is also associated with crowding, environmental degradation, and other impediments to productivity. Overall, we find no evidence that the level of urbanization affects the rate of economic growth. Our findings weaken the rationale for either encouraging or discouraging urbanization as part of a strategy for economic growth.urbanization, economic growth, development.

Fertility, Female Labor Force Participation, and the Demographic Dividend

We estimate the effect of fertility on female labor force participation in a cross-country panel data set using abortion legislation as an instrument for fertility. We find a large negative effect of the fertility rate on female labor force participation. The direct effect is concentrated among those aged 20–39, but we find that cohort participation is persistent over time giving an effect among older women. We present a simulation model of the effect of fertility reduction on income per capita, taking into account these changes in female labor force participation as well as population numbers and age structure.

Does Age Structure Forecast Economic Growth?

Increases in the proportion of the working age population can yield a "demographic dividend" that enhances the rate of economic growth. We estimate the parameters of an economic growth model with a cross section of countries over the period 1960 to 1980 and investigate whether the inclusion of age structure improves the model's forecasts for the period 1980 to 2000. We find that including age structure improves the forecast, although there is evidence of parameter instability between periods with an unexplained growth slowdown in the second period. We use the model to generate growth forecasts for the period 2000 to 2020.

Demographic Change, Institutional Settings, and Labor Supply

This paper analyzes cross-country panel data to examine the effect of key institutional features of social security systems on male labor supply. Our findings indicate that the labor supply of older males covaries negatively with replacement rates and system coverage, with the replacement rate effects being stronger for pay-as-you-go systems than for fully funded systems. The results also reveal a surprisingly small and often negative response of the labor supply of older males to improvements in life expectancy.Global health, labor, Aging, Economics, Demography.