Exchange Rate Models Are Not as Bad as You Think

Standard models of exchange rates, based on macroeconomic variables such as prices, interest rates, output, etc., are thought by many researchers to have failed empirically. We present evidence to the contrary. First, we emphasize the point that "beating a random walk" in forecasting is too strong a criterion for accepting an exchange rate model. Typically models should have low forecasting power of this type. We then propose a number of alternative ways to evaluate models. We examine in-sample fit, but emphasize the importance of the monetary policy rule, and its effects on expectations, in determining exchange rates. Next we present evidence that exchange rates incorporate news about future macroeconomic fundamentals, as the models imply. We demonstrate that the models might well be able to account for observed exchange-rate volatility. We discuss studies that examine the response of exchange rates to announcements of economic data. Then we present estimates of exchange-rate models in which expected present values of fundamentals are calculated from survey forecasts. Finally, we show that out-of-sample forecasting power of models can be increased by focusing on panel estimation and long-horizon forecasts.

Charging of ice-vapor interfaces

International audienceThe time resolved chemical composition of aerosol particles, formed by the oxidation of alpha-pinene has been investigated by liquid chromatography/mass spectrometry (LC-MS) using negative and positive ionisation methods (ESI(-) and APCI(+)). The experiments were performed at the EUPHORE facility in Valencia (Spain) under various experimental conditions, including dark ozone reactions, photosmog experiments with low NOx mixing ratios and reaction with OH radicals in the absence of NOx (H2O2-photolysis). Particles were sampled on PTFE filters at different stages of the reaction and extracted with methanol. The predominant products from alpha-pinene in the particulate phase are cis-pinic acid, cis-pinonic acid and hydroxy-pinonic acid isomers. Another major compound with molecular weight 172 was detected, possibly a hydroxy-carboxylic acid. These major compounds account for 50% to 80% of the identified aerosol products, depending on the time of sampling and type of experiment. In addition, more than 20 different products have been detected and structures have been tentatively assigned based on their molecular weight and responses to the different ionisation modes. The different experiments performed showed that the aerosol formation is mainly caused by the ozonolysis reaction. The highest aerosol yields were observed in the dark ozone experiments, for which also the highest ratios of mass of identified products to the formed aerosol mass were found (30% to 50%, assuming a density of 1 g cm-3)

Thermodynamics and the Global Optimization of Lennard-Jones clusters

Theoretical design of global optimization algorithms can profitably utilize recent statistical mechanical treatments of potential energy surfaces (PES's). Here we analyze the basin-hopping algorithm to explain its success in locating the global minima of Lennard-Jones (LJ) clusters, even those such as \LJ{38} for which the PES has a multiple-funnel topography, where trapping in local minima with different morphologies is expected. We find that a key factor in overcoming trapping is the transformation applied to the PES which broadens the thermodynamic transitions. The global minimum then has a significant probability of occupation at temperatures where the free energy barriers between funnels are surmountable.Comment: 13 pages, 13 figures, revte

The double-funnel energy landscape of the 38-atom Lennard-Jones cluster

The 38-atom Lennard-Jones cluster has a paradigmatic double-funnel energy landscape. One funnel ends in the global minimum, a face-centred-cubic (fcc) truncated octahedron. At the bottom of the other funnel is the second lowest energy minimum which is an incomplete Mackay icosahedron. We characterize the energy landscape in two ways. Firstly, from a large sample of minima and transition states we construct a disconnectivity tree showing which minima are connected below certain energy thresholds. Secondly we compute the free energy as a function of a bond-order parameter. The free energy profile has two minima, one which corresponds to the fcc funnel and the other which at low temperature corresponds to the icosahedral funnel and at higher temperatures to the liquid-like state. These two approaches show that the greater width of the icosahedral funnel, and the greater structural similarity between the icosahedral structures and those associated with the liquid-like state, are the cause of the smaller free energy barrier for entering the icosahedral funnel from the liquid-like state and therefore of the cluster's preferential entry into this funnel on relaxation down the energy landscape. Furthermore, the large free energy barrier between the fcc and icosahedral funnels, which is energetic in origin, causes the cluster to be trapped in one of the funnels at low temperature. These results explain in detail the link between the double-funnel energy landscape and the difficulty of global optimization for this cluster.Comment: 12 pages, 11 figures, revte

Dilaton Contact Terms in the Bosonic and Heterotic Strings

Dilaton contact terms in the bosonic and heterotic strings are examined following the recent work of Distler and Nelson on the bosonic and semirigid strings. In the bosonic case dilaton two-point functions on the sphere are calculated as a stepping stone to constructing a `good' coordinate family for dilaton calculations on higher genus surfaces. It is found that dilaton-dilaton contact terms are improperly normalized, suggesting that the interpretation of the dilaton as the first variation of string coupling breaks down when other dilatons are present. It seems likely that this can be attributed to the tachyon divergence found in \TCCT. For the heterotic case, it is found that there is no tachyon divergence and that the dilaton contact terms are properly normalized. Thus, a dilaton equation analogous to the one in topological gravity is derived and the interpretation of the dilaton as the string coupling constant goes through.Comment: 44 pages, Figures now included. This replacement version includes the 7 figures as PostScript files appended to the end and the macros to insert them into the text. Also some typos in intermediate formulae were correcte

A qualitative analysis of the interfaces between urban underground metro infrastructure and its environment in London

Peer reviewedPostprin

On the role of frameworks and smart mobility in addressing the rural mobility problem

Acknowledgements: We would like to acknowledge the European Commission in funding the SMARTA project (Contract n. No MOVE/B4/SER/2017-473/S 12.780134), which has enabled this research to take place. The insight papers and good practice cases referred to in this paper have been completed by members of the SMARTA Consortium: MemEx (IT), University of Aberdeen (UK), Transport & Mobility Leuven (BE), Vectos (UK) and European Integrated Projects (RO).Peer reviewedPostprin

Build an app and they will come? Lessons learnt from trialling the GetThereBus app in rural communities

Acknowledgements The research described here was supported by the award made by the RCUK Digital Economy programme to the dot.rural Digital Economy Hub; award reference: EP/G066051/1.Peer reviewedPostprin

World-Sheet Supersymmetry Without Contact Terms

Green and Seiberg showed that, in simple treatments of fermionic string theory, it is necessary to introduce contact interactions when vertex operators collide. Otherwise, certain superconformal Ward identities would be violated. In this note, we show how these contact terms arise naturally when proper account is taken of the superconformal geometry involved when punctures collide. More precisely, we show that there is no contact term at all! Rather, corrections arise to the ``na\"\i ve" formula when the boundary of moduli space is described correctly.Comment: 14pp., 2 figures (included