A Method To Remove Fringes From Images Using Wavelets

We have developed a new method that uses wavelet analysis to remove interference fringe patterns from images. This method is particularly useful for flat fields in the common case where fringes vary between the calibration and object data. We analyze the efficacy of this method by creating fake flats with fictitious fringes and removing the fringes. We find that the method removes 90% of the fringe pattern if its amplitude is equal to the random noise level and 60% if the fringe amplitude is $\approx 1/10$ of the noise level. We also present examples using real flat field frames. A routine written in the Interactive Data Language (IDL) that implements this algorithm is available from the authors and as an attachment to this paper.Comment: 7 pages, 14 figures. Accepted to the Astrophysical Journal. (The quality of the figures in this preprint has been downgraded in order to fulfill arXiv requirements. Check journal for the high-quality figures

TEA: A Code for Calculating Thermochemical Equilibrium Abundances

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. (1958) and Eriksson (1971). It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature-pressure pairs. We tested the code against the method of Burrows & Sharp (1999), the free thermochemical equilibrium code CEA (Chemical Equilibrium with Applications), and the example given by White et al. (1958). Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.Comment: 14 pages, 8 figures, article is submitted to ApJS, posted on arXiv for public commentary, please send comments to the lead autho

Private Monitoring and Communication in Cartels: Explaining Recent Collusive Practices

Motivated by recent cartel practices, a stable collusive agreement is characterized when firms' prices and quantities are private information. Conditions are derived whereby an equilibrium exists in which firms truthfully report their sales and then make transfers within the cartel based on these reports. The properties of this equilibrium fit well with the cartel agreements in a number of markets including citric acid, lysine, and vitamins. (JEL D43, D82, K21, L12, L61, L65)

Signaling and Tacit Collusion in an Infinitely Repeated Prisoners' Dilemma

In the context of an infinitely repeated Prisoners.Dilemma, we explore how cooperation is initiated when players signal and coordinate through their actions. There are two types of players - patient and impatient - and a player's type is private information. An impatient type is incapable of cooperative play, while if both players are patient types - and this is common knowledge - then they can cooperate with a grim trigger strategy. We find that the longer that players have gone without cooperating, the lower is the probability that they'll cooperate in the next period. While the probability of cooperation emerging is always positive, there is a positive probability that cooperation never occurs.

Private Monitoring and Communication in Cartels: Explaining Recent Collusive Practices

Motivated by recent cartel practices, a stable collusive agreement is characterized when firms' prices and quantities are private information. Conditions are derived whereby an equilibrium exists in which firms truthfully report their sales and then make transfers within the cartel based on these reports. The properties of this equilibrium fit well with the cartel agreements used in a number of markets including citric acid, lysine, and vitamins.

Signaling and Tacit Collusion in an Infinitely Repeated Prisoners' Dilemma

In the context of an infinitely repeated Prisoners' Dilemma, we explore how cooperation is initiated when players signal and coordinate through their actions. There are two types of players - patient and impatient - and a player's type is private information. An impatient type is incapable of cooperative play, while if both players are patient types - and this is common knowledge - then they can cooperate with a grim trigger strategy. We find that the longer that players have gone without cooperating, the lower is the probability that they'll cooperate in the next period. While the probability of cooperation emerging is always positive, there is a positive probability that cooperation never occurs.

The 1998 November 14 Occultation of GSC 0622-00345 by Saturn. I. Techniques for Ground-Based Stellar Occultations

On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345. We observed atmospheric immersion with NSFCAM at the National Aeronautics and Space Administration's Infrared Telescope Facility on Mauna Kea, Hawaii. Immersion occurred at 55.5\circ S planetocentric latitude. A 2.3 {\mu}m, methane-band filter suppressed reflected sunlight. Atmospheric emersion and ring data were not successfully obtained. We describe our observation, light-curve production, and timing techniques, including improvements in aperture positioning, removal of telluric scintillation effects, and timing. Many of these techniques are known within the occultation community, but have not been described in the reviewed literature. We present a light curve whose signal-to-noise ratio per scale height is 267, among the best ground-based signals yet achieved, despite a disadvantage of up to 8 mag in the stellar flux compared to prior work.Comment: LaTeX/emulateapj, 6 pages, 3 figures. Online items: The FITS-format light curve and the IDL code for the timing model are available from ApJ or the lead autho

Posted Pricing as a Plus Factor

This paper identifies conditions under which an industry-wide practice of posted (or list) pricing is a plus factor sufficient to conclude that firms violated Section 1 of the Sherman Act. For certain classes of markets, it is shown that, under competition, all firms setting a list price with a policy of no discounting is contrary to equilibrium. Thus, if all firms choose posted pricing, it is to facilitate collusion by making it easier for them to coordinate their prices. It is then argued that the adoption of posted pricing communicates the necessary intent and reliance to conclude concerted action.