Isometries and Hermitian Operators on Zygmund spaces

In this paper we characterize the isometries of subspaces of the little Zygmund space. We show that the isometries of these spaces are surjective and represented as integral operators. We also show that all hermitian operators on these settings are bounded

Pricing strategies in software platforms : video consoles vs. operating systems

We study software platforms for which the total amount that users spend depends on the twosided pricing strategy of the platform firm, and on the pricing strategy of application developers. When setting prices, developers may be constrained by one of two margins: the demand margin and the competition margin. By analyzing how these margins affect pricing strategies we find some conditions which explain features of the market of operating systems and its differences with the one corresponding to the video consoles. The problem that arises when the platform does not set prices (as an open platform) is considered. We show that policy makers should promote open source in operating systems platforms but not necessarily in video consoles. We also analyze the incentives for a platform to integrate with applications as a function of the extent of substitutability among them and provide a possible explanation for the observed fact of vertical disintegration in these industries

Temperature, gravity and bolometric correction scales for non-supergiant OB stars

Context. Precise and accurate determinations of effective temperature and surface gravity are mandatory to derive reliable chemical abundances and fundamental parameters like distances, masses, radii, luminosities of OB stars. Aims. Atmospheric parameters recently determined at high precision with several independent spectroscopic indicators in NLTE are employed to calibrate photometric relationships. Methods. Temperatures and gravities of 30 calibrators are compared to reddening-independent quantities of the Johnson and Stroemgren photometric systems. We also examine the spectral and luminosity classification of the star sample and compute bolometric corrections. Results. Calibrations of temperatures and gravities are proposed for various photometric indices and spectral types. Effective temperatures can be determined at a precision of ~400 K for luminosity classes III/IV and ~800 K for luminosity class V. Surface gravities can reach internal uncertainties as low as ~0.08 dex when using our calibration to the Johnson Q-parameter. Similar precision is achieved for gravities derived from the beta-index and the precision is lower for both atmospheric parameters when using the Stroemgren indices c1 and [u-b]. Our uncertainties are smaller than typical differences among other methods in the literature, reaching values up to ~2000 K for temperature and ~0.25 dex for gravity, and in extreme cases, ~6000 K and ~0.4 dex, respectively. A parameter calibration for sub-spectral types is also proposed. We present a new bolometric correction relation to temperature based on our empirical data. Conclusions. The photometric calibrations presented here are useful tools to estimate effective temperatures and surface gravities of non-supergiant OB stars in a fast manner. We recommend to use these calibrations as a first step, with subsequent refinements based on spectroscopy (abridged).Comment: 14 pages, 11 figures, accepted to be published in A&

What happens when a woman wins an election? Evidence from close races in Brazil

This paper analyzes the effect of the gender of local policymakers on policy outcomes. Analyzing a rich dataset from Brazilian municipalities and using a regression discontinuity design, we find that municipalities ruled by female mayors have better health outcomes, receive more federal discretionary transfers, and have lower corruption. Additionally, male mayors hire more temporary public employees than their female counterparts when they are allowed to run for re-election, and when municipal elections are approaching. These findings suggest that male mayors may promote more political patronage than female mayors and that men and women may respond differently to local election incentives

Two-sided platforms with endogenous quality differentiation

In this paper we construct a simple model of platform price competition with two main novel features. First, platforms endogenously decide the quality of their 'access service' and second, each group exhibits preferences not only about the number of agents in the opposite group, but also about their type or quality. Additionally, sellers also care about the type of agents in their own group. Our interest is to examine the set of conditions under which, in spite of the network externalities, more than one plaftorm coexist in equilibrium. We show that when quality is endogenously determined by the choices of agents these platforms could be asymmetric

Foreign stock holdings: the role of information

The household finance literature documents a large fraction of the population not participating in stock markets. It is also puzzling that a much greater share of households do not participate in foreign stock markets. Recent empirical evidence points towards the role of information in determining agents' portfolio choices. I test these results into a model that incorporates information on agents' portfolio allocation decision. In the model, consumers can invest in both domestic and foreign stocks and to update their information set, agents have to pay a cost implying that consumers update their portfolio only infrequently. In addition, to account for the initial costs of acquiring information about stock investments, a version of the model also features an entry-cost to be paid at the first period by agents that decide to enter stock market. Agents that invest in foreign stocks are more attentive, updating their portfolio more frequently. After calibrating the model to match returns and volatility for the U.S. economy and di¤erent foreign stock investments, I obtain that the minimum entry cost necessary to drive households completely out of stock markets is large (and in line with the equity premium puzzle literature). However, once agents already invest in domestic stock markets, the minimum cost that would drive investors out of foreign stocks market is much smaller. The size of the latter minimum entry cost depends on model parameters assumptions, and small variations on risk aversion and uncertaintly about foreign asset returns can bring this entry cost down enough to justify the substancial non-participation in foreign stock markets.Stockholders ; Stock market