Risk Aversion and Optimal Reserve Prices in First and Second-Price Auctions

This paper analyzes the effects of buyer and seller risk aversion in first and second-price auctions. The setting is the classic one of symmetric and independent private values, with ex ante homogeneous bidders. However, the seller is able to optimally set the reserve price. In both auctions the seller’s optimal reserve price is shown to decrease in his own risk aversion, and more so in the first-price auction. Thus, greater seller risk aversion increases the ex post efficiency of both auctions, and especially that of the first-price auction. The seller’s optimal reserve price in the first-price, but not in the second-price, auction decreases in the buyers’ risk aversion. Thus, greater buyer risk aversion also increases the ex post efficiency of the first but not the second-price auction. At the interim stage, the first-price auction is preferred by all buyer types in a lower interval, as well as by the seller.first-price auction, second-price auction, risk aversion, reserve price

Risk Aversion and Optimal Reserve Prices in First and Second-Price Auctions, Second Version

This paper analyzes the effects of buyer and seller risk aversion in first and second-price auctions. The setting is the classic one of symmetric and independent private values, with ex ante homogeneous bidders. However, the seller is able to optimally set the reserve price. In both auctions the seller’s optimal reserve price is shown to decrease in his own risk aversion, and more so in the first-price auction. Thus, greater seller risk aversion increases the ex post efficiency of both auctions, and especially that of the first-price auction. The seller’s optimal reserve price in the first-price, but not in the second-price, auction decreases in the buyers’ risk aversion. Thus, greater buyer risk aversion also increases the ex post efficiency of the first but not the second-price auction. At the interim stage, the first-price auction is preferred by all buyer types in a lower interval, as well as by the seller.first-price auction, second-price auction, risk aversion, reserve price

Generating Function For Network Delay

In this paper correspondence between experimental data for packet delay and two theoretical types of distribution is investigated. Statistical tests have shown that only exponential distribution can be used for the description of packet delays in global network. Precision experimental data to within microseconds are gathered by means of the RIPE Test Box. Statistical verification of hypothesis has shown that distribution parameters remain constants during 500 second intervals at least. In paper cumulative distribution function and generating function for packet delay in network are in an explicit form written down, the algorithm of search of parameters of distribution is resulted.Comment: 5 pages, 4 Tables, 5 Figure

On-demand or Spot? Selling the cloud to risk-averse customers

In Amazon EC2, cloud resources are sold through a combination of an on-demand market, in which customers buy resources at a fixed price, and a spot market, in which customers bid for an uncertain supply of excess resources. Standard market environments suggest that an optimal design uses just one type of market. We show the prevalence of a dual market system can be explained by heterogeneous risk attitudes of customers. In our stylized model, we consider unit demand risk-averse bidders. We show the model admits a unique equilibrium, with higher revenue and higher welfare than using only spot markets. Furthermore, as risk aversion increases, the usage of the on-demand market increases. We conclude that risk attitudes are an important factor in cloud resource allocation and should be incorporated into models of cloud markets.Comment: Appeared at WINE 201

Characterization of SiGe thin films using a laboratory X-ray instrument

The technique of reciprocal space mapping using X-rays is a recognized tool for the nondestructive characterization of epitaxial films. X-ray scattering from epitaxial Si0.4Ge0.6 films on Si(100) substrates using a laboratory X-ray source was investigated. It is shown that a laboratory source with a rotating anode makes it possible to investigate the material parameters of the super-thin 2–6 nm layers. For another set of partially relaxed layers, 50–200 nm thick, it is shown that from a high-resolution reciprocal space map, conditioned from diffuse scattering on dislocations, it is possible to determine quantitatively from the shape of a diffraction peak (possessing no thickness fringes) additional parameters such as misfit dislocation density and layer thickness as well as concentration and relaxation

Characterizing and Propagating Modeling Uncertainties in Photometrically-Derived Redshift Distributions

The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from multi-band imaging surveys. The accuracy of the photometric redshifts measured in these surveys depends not only on the quality of the flux data, but also on a number of modeling assumptions that enter into both the training set and SED fitting methods of photometric redshift estimation. In this work we focus on the latter, considering two types of modeling uncertainties: uncertainties in the SED template set and uncertainties in the magnitude and type priors used in a Bayesian photometric redshift estimation method. We find that SED template selection effects dominate over magnitude prior errors. We introduce a method for parameterizing the resulting ignorance of the redshift distributions, and for propagating these uncertainties to uncertainties in cosmological parameters.Comment: 13 pages, 12 figures, version published in Ap

Cryptographic requirements for chaotic secure communications

In recent years, a great amount of secure communications systems based on chaotic synchronization have been published. Most of the proposed schemes fail to explain a number of features of fundamental importance to all cryptosystems, such as key definition, characterization, and generation. As a consequence, the proposed ciphers are difficult to realize in practice with a reasonable degree of security. Likewise, they are seldom accompanied by a security analysis. Thus, it is hard for the reader to have a hint about their security. In this work we provide a set of guidelines that every new cryptosystems would benefit from adhering to. The proposed guidelines address these two main gaps, i.e., correct key management and security analysis, to help new cryptosystems be presented in a more rigorous cryptographic way. Also some recommendations are offered regarding some practical aspects of communications, such as channel noise, limited bandwith, and attenuation.Comment: 13 pages, 3 figure

Limits on the detectability of the CMB B-mode polarization imposed by foregrounds

We investigate which practical constraints are imposed by foregrounds to the detection of the B-mode polarization generated by gravitational waves in the case of experiments of the type currently being planned. Because the B-mode signal is probably dominated by foregrounds at all frequencies, the detection of the cosmological component depends drastically on our ability for removing foregrounds. We provide an analytical expression to estimate the level of the residual polarization for Galactic foregrounds, according to the method employed for their subtraction. We interpret this result in terms of the lower limit of the tensor-to-scalar ratio r that allows to disentangle the cosmological B-mode polarization from the foregrounds contribution. Polarized emission from extragalactic radio sources and gravitational lensing is also taken into account. As a first approach, we consider the ideal limit of an instrumental noise--free experiment: for a full--sky coverage and a degree resolution, we obtain a limit of r~10^(-4). This value can be improved by high--resolution experiments and, in principle, no clear fundamental limit on the detectability of gravitational waves polarization is found. Our analysis is also applied to planned or hypothetical future polarization experiments, taking into account expected noise levels.Comment: 15 pages, 9 figures, version accepted for publication in MNRA

Infrared Observations of the Candidate LBV 1806-20 & Nearby Cluster Stars

We report near-infrared photometry, spectroscopy, and speckle imaging of the hot, luminous star we identify as candidate LBV 1806-20. We also present photometry and spectroscopy of 3 nearby stars, which are members of the same star cluster containing LBV 1806-20 and SGR 1806-20. The spectroscopy and photometry show that LBV 1806-20 is similar in many respects to the luminous ``Pistol Star'', albeit with some important differences. They also provide estimates of the effective temperature and reddening of LBV 1806-20, and confirm distance estimates, leading to a best estimate for the luminosity of this star of $> 5 \times 10^6 L_{\odot}$. The nearby cluster stars have spectral types and inferred absolute magnitudes which confirm the distance (and thus luminosity) estimate for LBV 1806-20. If we drop kinematic measurements of the distance ($15.1 ^{+1.8}_{-1.3}$ kpc), we have a lower limit on the distance of $>9.5$ kpc, and on the luminosity of $>2 \times 10^6 L_{\odot}$, based on the cluster stars. If we drop both the kinematic and cluster star indicators for distance, an ammonia absorption feature sets yet another lower limit to the distance of $>5.7$ kpc, with a corresponding luminosity estimate of $>7 \times 10^5 L_{\odot}$ for the candidate LBV 1806-20. Furthermore, based on very high angular-resolution speckle images, we determine that LBV 1806-20 is not a cluster of stars, but is rather a single star or binary system. Simple arguments based on the Eddington luminosity lead to an estimate of the total mass of LBV 1806-20 (single or binary) exceeding $190 M_{\odot}$. We discuss the possible uncertainties in these results, and their implications for the star formation history of this cluster.Comment: 36 pages, including 8 figures (Figures 1 and 7 in JPG format due to space); Accepted for publication in Ap