121 research outputs found
On the evolution of the resonant planetary system HD128311
A significant number of the known multiple exoplanetary systems are
containing a pair of giant planets engaged in a low order mean motion
resonance. Such a resonant condition protects the dynamics of these planets
resulting in very stable orbits. According to recent studies the capture into a
resonance is the result of a planetary migration process induced by the
interaction of the planets with a protoplanetary disk. If the migration is slow
enough (adiabatic) next to a mean motion resonance, the two planets will also
be in apsidal corotation.
The recently refined orbital parameters of the system HD 128311 suggest that
the two giant planets are in a 2:1 mean motion resonance, however without
exhibiting apsidal corotation. Thus the evolution of this system can not be
described by an adiabatic migration process alone.
We present possible evolution scenarios of this system combining migration
processes and sudden perturbations. We model migration scenarios through
numerical integration of the gravitational N-body problem with additional
non-conservative forces. Planet-planet scattering has been investigated by
N-body simulations.
We show that the present dynamical state of the system HD128311 may be
explained by such evolutionary processes.Comment: 4 Pages, 7 Figures, accepted for AA Letter
Multinomial discrete choice models (in Russian)
This essay briefly describes the main features of some well-known multinomial discrete choice models: the standard logit, the mixed logit, and the probit.
On the Finite Sample Properties of Conditional Empirical Likelihood Estimators
We provide Monte Carlo evidence on the finite-sample behavior of the conditional empirical likelihood (CEL) estimator of Kitamura, Tripathi, and Ahn and the conditional Euclidean empirical likelihood (CEEL) estimator of Antoine, Bonnal, and Renault in the context of a heteroscedastic linear model with an endogenous regressor. We compare these estimators with three heteroscedasticity-consistent instrument-based estimators and the Donald, Imbens, and Newey estimator in terms of various performance measures. Our results suggest that the CEL and CEEL with fixed bandwidths may suffer from the no-moment problem, similarly to the unconditional generalized empirical likelihood estimators studied by Guggenberger. We also study the CEL and CEEL estimators with automatic bandwidths selected through cross-validation. We do not find evidence that these suffer from the no-moment problem. When the instruments are weak, we find CEL and CEEL to have finite-sample propertiesâin terms of mean squared error and coverage probability of confidence intervalsâpoorer than the heteroscedasticity-consistent Fuller (HFUL) estimator. In the strong instruments case, the CEL and CEEL estimators with automatic bandwidths tend to outperform HFUL in terms of mean squared error, while the reverse holds in terms of the coverage probability, although the differences in numerical performance are rather small
Nonsequential Search Equilibrium with Search Cost Heterogeneity
We generalize the model of Burdett and Judd (1983) to the case where an arbitrary finite number of firms sells a homogeneous good to buyers who have heterogeneous search costs. We show that a price dispersed symmetric Nash equilibrium always exists. Numerical results show that the behavior of prices with respect to the number of firms hinges upon the shape of the search cost distribution: when search costs are relatively concentrated (dispersed), entry of firms leads to higher (lower) average prices.nonsequential search, oligopoly, arbitrary search cost distributions
On the Identification of the Costs of Simultaneous Search
This paper studies the identification of the costs of simultaneous search in a class of (portfolio) problems studied by Chade and Smith (2006). We show that aggregate data from a single market, or disaggregate data from a single market segment, do not provide sufficient information to identify the costs of simultaneous search in any reasonable interval. We then show that by pooling aggregate data from multiple markets, or disaggregate data from multiple market segments, the econometrician can identify the costs of simultaneous search in a non-empty interval. Within the context of specific examples, we illustrate that identification of the search cost distribution in its full support may easily be obtained.search costs, portfolio choice, non-parametric identification
The effect of childhood obesity on social welfare
The young generation is the most influenced and vulnerable segment of the market. Food with high level of fat, sugar and/or salt are popularised for this segment. At the same time nearly 7 people die of obesity or from complications of obesity in Hungary each hour - one every 9 minutes. Approximately 119 million Americans, or 64.5 percent, of adult Americans are either overweight or obese. 17.5 million obese young persons live in the European Union. The result is the drastic elevation of the hygienic expenses. The average health care cost of overweight persons is higher by 42% than normal bodyweight ones. Per capita spending on fast foods is unbelievable and rising. The value of average spending was 2.5 ⏠in 2002. Fast food sales continue to boom despite warnings about obesity. The consumption of these products can contribute to the increased level of childhood obesity. 12.0% of young personâs visited a fast food restaurant at least with a weekly regularity. The value is 16.9% in case of young men higher than in case of young ladies (8.1%) to our research. We can state the respondents underestimate the costs of fast foods.fast food, childhood obesity, cost, youth, Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy, Marketing,
Jets in AGN at extremely high redshifts
A brief review of VLBI structures in extremely high-redshift AGN
(revised/edited).Comment: To appear in the Proceedings of the IAU Symposium No. 313:
Extragalactic jets from every angle, Galapagos, Ecuador, 15-19 September
2014, F. Massaro, C. C. Cheung, E. Lopez, and A. Siemiginowska (Eds.),
Cambridge University Pres
VLBI observations of a flared optical quasar CGRaBS J0809+5341
A bright optical flare was detected in the high-redshift () quasar
CGRaBS J0809+5341 on 2014 April 13. The absolute magnitude of the object
reached during the flare, making it the brightest one (in flaring
stage) among all known quasars so far. The 15 GHz flux density of CGRaBS
J0809+5341 monitored in the period from 2008 to 2016 also reached its peak at
the same time. To reveal any structural change possibly associated with the
flare in the innermost radio structure of the quasar, we conducted a pilot very
long baseline interferometry (VLBI) observation of CGRaBS J0809+5341 using the
European VLBI Network (EVN) at 5 GHz on 2014 November 18, about seven months
after the prominent optical flare. Three epochs of follow-up KaVA (Korean VLBI
Network and VLBI Exploration of Radio Astrometry Array) observations were
carried out at 22 and 43 GHz frequencies from 2015 February 25 to June 4, with
the intention of exploring a possibly emerging new radio jet component
associated with the optical flare. However, these high-resolution VLBI
observations revealed only the milliarcsecond-scale compact "core" that was
known in the quasar from earlier VLBI images, and showed no sign of any
extended jet structure. Neither the size, nor the flux density of the "core"
changed considerably after the flare according to our VLBI monitoring. The
results suggest that any putative radio ejecta associated with the major
optical and radio flare could not yet be separated from the "core" component,
or the newly-born jet was short-lived.Comment: 4 figures, 2 tables, accepted for publication in PAS
Simultaneous search for differentiated products:The impact of search costs and firm prominence
We extend the literature on simultaneous search by allowing for differentiated products and search cost heterogeneity. We show conditions under which a symmetric price equilibrium exists. We provide a necessary and sufficient condition under which an increase in search costs may result in a lower, equal or higher equilibrium price. We extend this analysis to the case with more than two firms. The effects of prominence on equilibrium prices are also studied. The prominent firm charges a higher price than the non-prominent firm and both their prices are below the symmetric equilibrium price. Consequently, market prominence increases the consumersâ surplus
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