Improved phase locked loop receiver

Improved phase locked loop receiver tracks and demodulates a signal whose signal-to-noise ratio may be low and whose information sidebands are close in frequency. This receiver recovers the carrier from input signals and applies it to a demodulator which recovers the sidebands

Percolation of hard disks

Random arrangements of points in the plane, interacting only through a simple hard core exclusion, are considered. An intensity parameter controls the average density of arrangements, in analogy with the Poisson point process. It is proved that at high intensity, an infinite connected cluster of excluded volume appears with positive probability.Comment: 16 pages, 6 figure

Quantum trajectories and open many-body quantum systems

The study of open quantum systems has become increasingly important in the past years, as the ability to control quantum coherence on a single particle level has been developed in a wide variety of physical systems. In quantum optics, the study of open systems goes well beyond understanding the breakdown of quantum coherence. There, the coupling to the environment is sufficiently well understood that it can be manipulated to drive the system into desired quantum states, or to project the system onto known states via feedback in quantum measurements. Many mathematical frameworks have been developed to describe such systems, which for atomic, molecular, and optical (AMO) systems generally provide a very accurate description of the open quantum system on a microscopic level. In recent years, AMO systems including cold atomic and molecular gases and trapped ions have been applied heavily to the study of many-body physics, and it has become important to extend previous understanding of open system dynamics in single- and few-body systems to this many-body context. A key formalism that has already proven very useful in this context is the quantum trajectories technique. This was developed as a numerical tool for studying dynamics in open quantum systems, and falls within a broader framework of continuous measurement theory as a way to understand the dynamics of large classes of open quantum systems. We review the progress that has been made in studying open many-body systems in the AMO context, focussing on the application of ideas from quantum optics, and on the implementation and applications of quantum trajectories methods. Control over dissipative processes promises many further tools to prepare interesting and important states in strongly interacting systems, including the realisation of parameter regimes in quantum simulators that are inaccessible via current techniques.Comment: 66 pages, 29 figures, review article submitted to Advances in Physics - comments and suggestions are welcom

Even if it's not Bribery: The Case for Campaign Finance Reform

We develop a dynamic multidimensional signaling model of campaign finance in which candidates can signal their ability by enacting policy and/or by raising and spending campaign funds, both of which are costly. Our model departs from the existing literature in that candidates do not exchange policy influence for campaign contributions; rather, they must decide how to allocate their efforts between policymaking and fundraising. If high-ability candidates are better policymakers and better fundraisers, then they will raise and spend campaign funds even if voters care only about legislation. Campaign finance reform alleviates this phenomenon and improves voter welfare at the expense of politicians. Thus, we expect successful politicians to oppose true campaign finance reform. We also show that our model is consistent with findings in the empirical and theoretical campaign finance literature

A “Local” Model of the Firm: Sticky prices and the Phillips Curve

Assume a firm concerns itself exclusively with local shocks (copious citations including Lucas 1972 and Bomhoff 1983 validate that this type of assumption may be reasonable). Changes in a firm's production policy should occur when the actual demand in a period Dt suggests that the underlying demand function has shifted from expected demand E(Dt). Since firms face uncertainty, this is non-trivial and they must find a way to determining (given information from a single, current period) whether or not the underlying demand has changed or whether the firm has simply obtained a draw from its expected demand distribution. In a simplified model, a firm can use a concept similar to a Statistical Hypothesis Test on E(Dt) = Dt to come to this conclusion. Rather than select an arbitrary confidence threshold (alpha), a firm can reverse the process and use the "marginal" alpha (where the hypothesis is just rejected or accepted) as its confidence that the mean has changed, allowing it to update its expectations to E(Dt+1) = (1-a) * E(Dt) + a * (Dt) and price accordingly. By weighting new demand information using this "confidence factor," the model introduces significant and persistent rigidity around NAIRU/equilibrium. This model is also powerful because it explains the qualified success of threshold like behaivor in classical "menu cost" theories (as the threshold reflects the classic hypothesis test strategy), behavior similar to a learning model (via the weighted introduction of new data) and seeming information lags (via the low confidence in new information immediately after shifts), among others.phillips curve

The moment index of minima (II)

The moment index of a nonnegative random variable X has the property that the moment index of the minimum of two independent r.v.s X and Y is greater than or equal to the sum of the moment indices of X and Y. We characterize conditions under which equality holds for a given r.v. X and every independent nonnegative r.v. Y, and discuss extensions to related r.v.s and their distributions

The Accounting Industry in the Age of Globalization and Offshore Outsourcing

The phenomenon of outsourcing has engulfed the accounting industry and offers a wide range of services from bookkeeping, accounts payable, debt collection, invoicing, to tax return preparation. As companies become more comfortable with the services provided by outsourcing facilitators, the level of outsourcing in the accounting industry will increase to allow U.S. firms to focus on higher margin services and meet client demands in more technical areas of tax, estate, and retirement planning. This research uses a survey to collect primary data focusing on three areas, namely outsourcing drivers, concerns stakeholders have about outsourcing, and the perspectives about the offshorability of specific functions. The study concludes that firms that are engaging in outsourcing activities realize benefits in and ease their perceptions about doing so. Firms who outsource have been able to cut costs and increase staff. These same firms also are less concerned about most of the issues (privacy, client relationships, etc.) which may be as a result of their positive experience with outsourcing activities. Furthermore, these firms also have a higher confidence about the outsourecability of most of the functions in the accounting industry. The study further presents policy implications to all stakeholders in the accounting industry: students, professors, accounting professionals and firms, regulatory bodies, and politicians