13,486 research outputs found

    The use of narrative to provide a cohesive structure for a web based computing course

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    Narrative has long been used as an educational tool. This article explains how narrative, in the form of popular accounts, has been used to provide context, structure and broad appeal to a large-scale, entry-level university course on Information and Communication Technology (ICT). This course is delivered via the web with online tuition. Students' responses to the use of narrative and the scope of the material has been encouraging. It is argued that narrative performs an enculturation function that is often under-utilised in ICT education

    Constraining inverse-curvature gravity with supernovae

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    We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07 <=omega(m)<= 0.21 (95% C.L.). Hence the inverse-curvature gravity models considered cannot explain the dynamics of the Universe just with a baryonic matter component

    The Cosmic Microwave Background and the Ionization History of the Universe

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    Details of how the primordial plasma recombined and how the universe later reionized are currently somewhat uncertain. This uncertainty can restrict the accuracy of cosmological parameter measurements from the Cosmic Microwave Background (CMB). More positively, future CMB data can be used to constrain the ionization history using observations. We first discuss how current uncertainties in the recombination history impact parameter constraints, and show how suitable parameterizations can be used to obtain unbiased parameter estimates from future data. Some parameters can be constrained robustly, however there is clear motivation to model recombination more accurately with quantified errors. We then discuss constraints on the ionization fraction binned in redshift during reionization. Perfect CMB polarization data could in principle distinguish different histories that have the same optical depth. We discuss how well the Planck satellite may be able to constrain the ionization history, and show the currently very weak constraints from WMAP three-year data.Comment: Changes to match MNRAS accepted versio

    Central bank intervention with limited arbitrage

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    Shleifer and Vishny (1997) pointed out some of the practical and theoretical problems associated with assuming that rational risk-arbitrage would quickly drive asset prices back to long-run equilibrium. In particular, they showed that the possibility that asset price disequilibrium would worsen, before being corrected, tends to limit rational speculators. Uniquely, Shleifer and Vishny (1997) showed that “performance-based asset management” would tend to reduce risk-arbitrage when it is needed most, when asset prices are furthest from equilibrium. We analyze a generalized Shleifer and Vishny (1997) model for central bank intervention. We show that increasing availability of arbitrage capital has a pronounced effect on the dynamic intervention strategy of the central bank. Intervention is reduced during periods of moderate misalignment and amplified at times of extreme misalignment. This pattern is consistent with empirical observation.

    Predicting exchange rate volatility: genetic programming vs. GARCH and RiskMetrics

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    This article investigates the use of genetic programming to forecast out-of-sample daily volatility in the foreign exchange market. Forecasting performance is evaluated relative to GARCH(1,1) and RiskMetrics models for two currencies, DEM and JPY. Although the GARCH/RiskMetrics models appear to have a inconsistent marginal edge over the genetic program using the mean-squared-error (MSE) and R2 criteria, the genetic program consistently produces lower mean absolute forecast errors (MAE) at all horizons and for both currencies.Foreign exchange rates ; Forecasting ; Programming (Mathematics)

    Technical analysis in the foreign exchange market

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    This article introduces the subject of technical analysis in the foreign exchange market, with emphasis on its importance for questions of market efficiency. Technicians view their craft, the study of price patterns, as exploiting traders’ psychological regularities. The literature on technical analysis has established that simple technical trading rules on dollar exchange rates provided 15 years of positive, risk-adjusted returns during the 1970s and 80s before those returns were extinguished. More recently, more complex and less studied rules have produced more modest returns for a similar length of time. Conventional explanations that rely on risk adjustment and/or central bank intervention are not plausible justifications for the observed excess returns from following simple technical trading rules. Psychological biases, however, could contribute to the profitability of these rules. We view the observed pattern of excess returns to technical trading rules as being consistent with an adaptive markets view of the world.Foreign exchange rates

    Lessons from the evolution of foreign exchange trading strategies

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    The adaptive markets hypothesis posits that trading strategies evolve as traders adapt their behavior to changing circumstances. This paper studies the evolution of trading strategies for a hypothetical trader who chooses portfolios from foreign exchange (forex) technical rules in major and emerging markets, the carry trade, and U.S. equities. The results show that forex trading alone dramatically outperforms the S&P 500 but there is little gain to coordinating forex and equity strategies, which explains why practitioners consider these tools separately. In addition, a backtesting procedure to choose optimal portfolios does not select carry trade strategies until well into the 1990s, which helps to explain the relatively recent surge in interest in this strategy. Forex trading returns dip significantly in the 1990s but recover by the end of the decade and have greatly outperformed an equity position since 1998. Overall, trading rule returns still exist in forex markets—with substantial stability in the types of rules—though they have migrated to emerging markets to a considerable degree.Foreign exchange ; Trade

    Intraday technical trading in the foreign exchange market

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    This paper examines the out-of-sample performance of intraday technical trading strategies selected using two methodologies, a genetic program and an optimized linear forecasting model. When realistic transaction costs and trading hours are taken into account, we find no evidence of excess returns to the trading rules derived with either methodology. Thus, our results are consistent with market efficiency. We do, however, find that the trading rules discover some remarkably stable patterns in the data.Foreign exchange
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