Photo-induced gap closure in an excitonic insulator

We study the dynamical phase transition out of an excitonic insulator phase after photo-excitation using a time-dependent extension of the selfconsistent GW method. We connect the evolution of the photoemission spectra to the dynamics of the excitonic order parameter and identify two dynamical phase transition points marked by a slowdown in the relaxation: one critical point is connected with the trapping in a nonthermal state with reduced exciton density and the second corresponds to the thermal phase transition. The transfer of kinetic energy from the photoexcited carriers to the exciton condensate is shown to be the main mechanism for the gap melting. We analyze the low energy dynamics of screening, which strongly depends on the presence of the excitonic gap, and argue that it is difficult to interpret the static component of the screened interaction as the effective interaction of some low energy model. Instead we propose a phenomenological measure for the effective interaction which indicates that screening has minor effects on the low energy dynamics

Dynamics of screening in photo-doped Mott insulators

We use a nonequilibrium implementation of extended dynamical mean field theory to study the effect of dynamical screening in photo-excited Mott insulators. The insertion of doublons and holes adds low-energy screening modes and leads to a reduction of the Mott gap. The coupling to low-energy bosonic modes further- more opens new relaxation channels and significantly speeds up the thermalization process. We also consider the effect of the energy distribution of the doped carriers on the screening

Nonequilibrium GW+EDMFT: Antiscreening and inverted populations from nonlocal correlations

We study the dynamics of screening in photo-doped Mott insulators with long-ranged interactions using a nonequilibrium implementation of the $GW$ plus extended dynamical mean field theory ($GW$+EDMFT) formalism. Our study demonstrates that the complex interplay of the injected carriers with bosonic degrees of freedom (charge fluctuations) can result in long-lived transient states with properties that are distinctly different from those of thermal equilibrium states. Systems with strong nonlocal interactions are found to exhibit a self-sustained population inversion of the doublons and holes. This population inversion leads to low-energy antiscreening which can be detected in time-resolved electron-energy loss spectra

An analysis of EU and US productivity developments (a total economy and industry level perspective)

The 1990s witnessed some important shifts in the underlying growth performances of the EU and US economies, with a significant gap opening up in terms of GDP, and more importantly, GDP per capita, growth rates. From a situation over the period 1980-1995 when EU and US living standards were growing at roughly an equivalent rate, the second half of the 1990s saw the emergence of a significant growth gap in favour of the US. These EU-US differences are mirrored at the EU Member State level, with simple measures of dispersion indicating that individual country divergences relative to the average EU performance have grown by close to 50 per cent in the 1990s compared with the 1980s. These extra- and intra-EU divergences in economic fortunes have been the subject of intense research efforts in recent years, with policy makers keen to decipher the reasons for their own respective outturns and to further refine the “magic formula†for boosting their long run growth performances. The present study will contribute to this ongoing debate regarding the sources of growth in general, with specific attention being devoted to productivity determinants given their importance in shaping medium to long run changes in living standards.GDP, United States, US, productivity, labour productivity, industry, industry level analysis, Denis, McMorrow, R�ger

Production function approach to calculating potential growth and output gaps - estimates for the EU Member States and the US

This paper describes the methodology for calculating potential growth and output gaps using a production function approach. On the basis of the Commission services Spring 2002 economic forecasts, the approach is illustrated by providing estimates for the EU's Member States, the Euro Zone and EU15 aggregates as well as for the United States.production function, growth and output, economic forecasts, Denis, Mc Morrow, R�ger

Globalisation : trends, issues and macro implications for the EU

Globalisation, defined as an increasingly integrated world economy, has the potential to generate the largest structural upheaval in economies since the industrial revolution. As in the past, this process is being underpinned by both technological change and by a shift in policies in many countries towards a more open, market based, system of economic governance. These policies reflect the realities of a new world order where knowledge creation and absorption and the flexibility of the regulatory and institutional frameworks will be the key determinants of the economic fortunes of economies. This paper examines the historical empirical evidence regarding globalisation and quantifies the macro benefits and costs for the EU over the coming decades.globalisation, trade integration, global productivity, terms of trade, Denis , Mc Morrow, R�ger

Long-term labour productivity and GDP projections for the EU25 Member States : a production function framework

This paper presents the results of long run labour productivity and GDP growth rate projections (until 2050) for each of the 25 EU Member States and provides a detailed overview of the forecast methodology used. These projections were undertaken in order to provide an internationally comparable macroeconomic framework against which to assess the potential economic and fiscal effects of ageing populations. The projections presented in this paper, using a common production function methodology for all 25 countries, show the GDP growth rate effects of an assumptions-driven extrapolation of recent trends in employment and labour productivity. These base case projections reflect the working assumption of “no policy change”.Various sensitivity tests are carried out to check the GDP per capita impact of some factors which have been excluded from the baseline scenario for reasons of simplicity or because of a lack of consensus in the academic literature. Some of the interesting conclusions that emerge from these sensitivity tests include : • Firstly, the GDP per capita impact of changes in the participation rate assumption used in the projections is much greater than for assumed changes in the share of part-time employment (i.e. in average hours worked per worker). • Secondly, the negative effect of a change in the age-structure of the population is fairly limited, although it is accepted that the labour productivity of an individual is likely to decline after the age of 55. A very strong fall in the productivity of older workers compared with that of prime-age workers would be required to significantly depress total labour productivity. Such an outcome, on the basis of current evidence, appears rather unlikely. • Thirdly, changing the TFP growth rate targets (e.g. use of the 1990’s average instead of the long-term 1970-2004 average) could strongly affect the projections. • Finally, an assumption of productivity convergence in levels substantially alters the projections for most EU10 countries but leaves the EU15 almost unchanged. JEL classificProductivity; ageing; long-term projections; production function; labour productivity; older workers

Calculating potential growth rates and output gaps - A revised production function approach

Any meaningful analysis of cyclical developments, of medium term growth prospects or of the stance of fiscal and monetary policies are all predicated on either an implicit or explicit assumption concerning the rate of potential output growth. Given the importance of the concept, the measurement of potential output is the subject of contentious and sustained research interest. All the available methods have "pros" and "cons" and none can unequivocally be declared better than the alternatives in all cases. Thus, what matters is to have a method adapted to the problem under analysis, with well defined limits and, in international comparisons, one that deals identically with all countries. This is the approach adopted in the present paper where it is stated clearly that the objective is to produce an economics based, production function, method which can be used for operational EU policy surveillance purposes.growth rates, cyclical developments, production function, potential output, Denis, Grenouilleau, Mc Morrow, R�ger

A self consistent chemically stratified atmosphere model for the roAp star 10 Aquilae

Context: Chemically peculiar A type (Ap) stars are a subgroup of the CP2 stars which exhibit anomalous overabundances of numerous elements, e.g. Fe, Cr, Sr and rare earth elements. The pulsating subgroup of the Ap stars, the roAp stars, present ideal laboratories to observe and model pulsational signatures as well as the interplay of the pulsations with strong magnetic fields and vertical abundance gradients. Aims: Based on high resolution spectroscopic observations and observed stellar energy distributions we construct a self consistent model atmosphere, that accounts for modulations of the temperature-pressure structure caused by vertical abundance gradients, for the roAp star 10 Aquilae (HD 176232). We demonstrate that such an analysis can be used to determine precisely the fundamental atmospheric parameters required for pulsation modelling. Methods: Average abundances were derived for 56 species. For Mg, Si, Ca, Cr, Fe, Co, Sr, Pr, and Nd vertical stratification profiles were empirically derived using the ddafit minimization routine together with the magnetic spectrum synthesis code synthmag. Model atmospheres were computed with the LLModels code which accounts for the individual abundances and stratification of chemical elements. Results: For the final model atmosphere Teff=7550 K and log g=3.8 were adopted. While Mg, Si, Co and Cr exhibit steep abundance gradients Ca, Fe and Sr showed much wider abundance gradients between log tau_5000=-1.5 and 0.5. Elements Mg and Co were found to be the least stratified, while Ca and Sr showed strong depth variations in abundance of up to ~ 6 dex.Comment: 9 pages, 15 figure