Pattern formation of quantum jumps with Rydberg atoms

We study the nonequilibrium dynamics of quantum jumps in a one-dimensional chain of atoms. Each atom is driven on a strong transition to a short-lived state and on a weak transition to a metastable state. We choose the metastable state to be a Rydberg state so that when an atom jumps to the Rydberg state, it inhibits or enhances jumps in the neighboring atoms. This leads to rich spatiotemporal dynamics that are visible in the fluorescence of the strong transition. It also allows one to dissipatively prepare Rydberg crystals

Hysteresis and economics - taking the economic past into account

The goal of this article is to discuss the rationale underlying the application of hysteresis to economic models. In particular, we explain why many aspects of real economic systems are hysteretic is plausible. The aim is to be explicit about the difficulties encountered when trying to incorporate hysteretic effects into models that can be validated and then used as possible tools for macroeconomic control. The growing appreciation of the ways that memory effects influence the functioning of economic systems is a significant advance in economic thought and, by removing distortions that result from oversimplifying specifications of input-output relations in economics, has the potential to narrow the gap between economic modeling and economic reality

The Bank's balance sheet during the crisis

This article sets out how monetary policy implementation and liquidity provision during the financial crisis have affected the size and composition of the Bank of England’s balance sheet. It extends and updates a recent speech by Paul Fisher, Executive Director Markets, and describes the main components of the Bank’s balance sheet prior to and during the crisis.

Synchronization of groups of coupled oscillators with sparse connections

Synchronization of groups of coupled oscillators with sparse connections are explored. It is found that different topologies of intergroup couplings may lead to different synchronizability. In the strong-coupling limit, an analytical treatment and criterion is proposed to judge the synchronization between communities of oscillators, and an optimal connection scheme for the group synchronization is given. By varying the intergroup and intragroup coupling strengths, different synchronous phases, i.e., the unsynchronized state, intragroup synchronization, intergroup synchronization, and global synchronization are revealed. The present discussions and results can be applied to study the pattern formation and synchronization of coupled spatiotemporal systems

Measuring the Drivers of Metropolitan Growth: The Export Price Index

The Export Price Index (EPI) is a measure of exogenous price shocks to a city’s export industries. Thus far the EPI has been used to estimate models of metropolitan statistical area employment demand and appears to capture exogenous demand shocks to the regional economy. This article explains the intuition behind and construction of the EPI. Glaeser (2008) has noted that because “the economic theory of cities emphasizes a search for exogenous causes of endogenous outcomes like local wages, housing prices, and city growth, it is unsurprising that the economic empirics on cities have increasingly focused on the quest for exogenous sources of variation.” The EPI is such an exogenous cause. The EPI data discussed in this note are available through The George Washington University Center for Economic Research website at http://www.gwu.edu/~cer1/datasets/datasets.html

The Role of Geographic Proximity And Industrial Structure In Metropolitan Area Business Cycles

Measurement and prediction of aggregate economic fluctuations at the region, state, and metropolitan area level is a major challenge. As data quality and analytical techniques have improved, the analysis of coincident economic cycle indicators (CEI) has progressed from national to regional to state levels. This paper continues the trend of geographic disaggregation by constructing and analyzing CEI at the MSA level. The theoretical advantage of MSA level indexes is that they reflect labor market areas. Given lack of quarterly economic time series at the MSA level, we construct a new variable, the EPI (export price index). The EPI is an index number constructed to measure changes in the prices of goods produced by major industries located in metropolitan areas. Using non-agricultural employment and the EPI as MSA-specific variables, we are able to estimate following a Stock/Watson type single factor models. We find that, for larger states, with multiple MSAs, there is substantial variation in the amplitude and timing of cycles across MSAs. Further tests group MSAs within states by applying cluster analysis to the state series for the MSAs within a state. The groupings are interesting for two reasons. First, they confirm the differences observed within states. Secondly, and perhaps most important, the groupings of cyclically similar MSAs are not always based on geographic proximity as might be expected. It appears that industrial similarity of the MSA economies is also important for cyclical performance

Opto-Mechanical Chaotic Behaviour of Micron-Scaled On-Chip Resonators

Opto-mechanical vibration of an on-chip oscillator is experimentally excited by radiation-pressure nonlinearity to a regime where oscillation is chaotic. Period-doubling and broad power spectra are measured in spherical and toroidal-resonators

Two-dimensional aerodynamic characteristics of the OLS/TAAT airfoil

Two flight tests have been conducted that obtained extension pressure data on a modified AH-1G rotor system. These two tests, the Operational Loads Survey (OLS) and the Tip Aerodynamics and Acoustics Test (TAAT) used the same rotor set. In the analysis of these data bases, accurate 2-D airfoil data is invaluable, for not only does it allow comparison studies between 2- and 3-D flow, but also provides accurate tables of the airfoil characteristics for use in comprehensive rotorcraft analysis codes. To provide this 2-D data base, a model of the OLS/TAAT airfoil was tested over a Reynolds number range from 3 x 10 to the 6th to 7 x 10 to the 7th and between Mach numbers of 0.34 to 0.88 in the NASA Langley Research Center's 6- by 28-Inch Transonic Tunnel. The 2-D airfoil data is presented as chordwise pressure coefficient plots, as well as lift, drag, and pitching moment coefficient plots and tables

A Nanoscale Parametric Feedback Oscillator

We describe and demonstrate a new oscillator topology, the parametric feedback oscillator (PFO). The PFO paradigm is applicable to a wide variety of nanoscale devices and opens the possibility of new classes of oscillators employing innovative frequency-determining elements, such as nanoelectromechanical systems (NEMS), facilitating integration with circuitry and system-size reduction. We show that the PFO topology can also improve nanoscale oscillator performance by circumventing detrimental effects that are otherwise imposed by the strong device nonlinearity in this size regime