Comparing the performance of stellar variability filters for the detection of planetary transits

We have developed a new method to improve the transit detection of Earth-sized planets in front of solar-like stars by fitting stellar microvariability by means of a spot model. A large Monte Carlo numerical experiment has been designed to test the performance of our approach in comparison with other variability filters and fitting techniques for stars of different magnitudes and planets of different radius and orbital period, as observed by the space missions CoRoT and Kepler. Here we report on the results of this experiment.Comment: 4 pages, 3 postscript figures, Transiting Planets Proceeding IAU Symposium No.253, 200

Optimal Rules under Adjustment Cost and Infrequent Information

A large number of microeconomic decision variables such as investments, prices, inventories or employment are characterized by intermittent large adjustments. The behavior of those variables has been often modeled as following state-dependent rules. The optimality of such state-dependent rules depends crucially on the continuous observation of the relevant state, an assumption which is far from being fulfilled in practice. We propose an alternative model, where at least part of information about the relevant state variable is infrequent. We study several alternatives. We start with the special case where innovations are infrequent, but are readily observed. Only in this case are optimal rules state-dependent. We then explore the common case of infrequent and delayed information. It may arrive at deterministic times, like periodic macroeconomic statistics, or stochastically, when some events trigger announcements. Part of the relevant information may be continuously observed, while the other part is only observed infrequently. The resulting rules are time and state dependent, characterized by trigger and target points that are functions of the time spent since the last time of information arrival. We derive the conditions which characterize the optimal rules and provide numerical algorithms for each caseAdjustment costs, Infrequent information, Optimal rules

Political Business Cycles through Lobbying

In this paper we build a framework where the interplay between the lobby power of special interest groups and the voting power of the majority of the population leads to political business cycles. We apply our set up to explain electoral cycles in government expenditure composition as well as to cycles in aggregate expenditures and in real exchange rates.

The physicist's guide to one of biotechnology's hottest new topics: CRISPR-Cas

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) constitute a multi-functional, constantly evolving immune system in bacteria and archaea cells. A heritable, molecular memory is generated of phage, plasmids, or other mobile genetic elements that attempt to attack the cell. This memory is used to recognize and interfere with subsequent invasions from the same genetic elements. This versatile prokaryotic tool has also been used to advance applications in biotechnology. Here we review a large body of CRISPR-Cas research to explore themes of evolution and selection, population dynamics, horizontal gene transfer, specific and cross-reactive interactions, cost and regulation, non-immunological CRISPR functions that boost host cell robustness, as well as applicable mechanisms for efficient and specific genetic engineering. We offer future directions that can be addressed by the physics community. Physical understanding of the CRISPR-Cas system will advance uses in biotechnology, such as developing cell lines and animal models, cell labeling and information storage, combatting antibiotic resistance, and human therapeutics.Comment: 75 pages, 15 figures, Physical Biology (2018

The Political Economy of Exchange Rate Policy in Brazil: 1964-1997

This paper analyzes political economy determinants of exchange rate policy in Brazil over the past thirty years. Two complementary methodologies are used. The first consists of investigating the exchange rate policy historical context over this period. Thus, part of the paper is dedicated to an historical account of the political economy of the exchange rate policy in Brazil from 1964 to 1997. The driving force affecting exchange rate policy was the tradeoff between the positive effect of a depreciated exchange rate on the balance of payments and its negative effect on inflation. The exchange rate policy resulting from this tradeoff depended on the political environment. An analytical framework is sketched to interpret the real exchange rate policy history, and then it is extended to encompass short-run election cycles. The second methodology is statistical. A Markov Switching Model is used to characterize statistically the exchange rate regimes, defined as valued or devalued real exchange rates, and the influence of political economy variables on regime changes. The results support the interpretation pursued in the analytical part. We found statistical evidence that the probability of an appreciated exchange rate is higher under democracy than under dictatorship. Furthermore, according to our statistical results there is also an election cycle: the probability of having an appreciated exchange rate is higher in the months preceding elections while the probability of having a depreciated exchange rate is higher in the months succeeding elections.

Endogenous Time-Dependent Rules and Inflation Inertia

In this paper we endogenize fixed price time-dependent rules to examine the output effects of monetary disinflation. We derive the optimal rules in and out of inflationary steady states, and develop a methodology to aggregate individual pricing rules which vary through time. Because of strategic complementarities we have to solve both problems simultaneously. This allows us to reassess the output costs of monetary disinflations, including aspects such as the roles of the initial level of inflation, and of the degree of strategic complementarity in price. Finally, we relax the strict assumption of pure time-dependent rules by allowing price setters to reevaluate their rules at the time disinflation is announced.