Cross-Kerr interaction in a four-level atomic system

We derive the form of the cross-Kerr interaction in a four-level atomic system in the N-configuration. We use time-independent perturbation theory to calculate the eigenenergies and eigenstates of the Schrodinger equation for the system. The system is considered as a perturbation of a Raman resonant three-level lambda scheme for which exact solutions are known. We show that within the strong control field limit the cross-Kerr interaction can arise between two weak probe fields. The strength of this nonlinear coupling is several orders of magnitude larger than that achievable using optical fibres.Comment: 5 pages, resubmitted to Physical Review A with clarified style and correction to Fig

Elicitability and backtesting: Perspectives for banking regulation

Conditional forecasts of risk measures play an important role in internal risk management of financial institutions as well as in regulatory capital calculations. In order to assess forecasting performance of a risk measurement procedure, risk measure forecasts are compared to the realized financial losses over a period of time and a statistical test of correctness of the procedure is conducted. This process is known as backtesting. Such traditional backtests are concerned with assessing some optimality property of a set of risk measure estimates. However, they are not suited to compare different risk estimation procedures. We investigate the proposal of comparative backtests, which are better suited for method comparisons on the basis of forecasting accuracy, but necessitate an elicitable risk measure. We argue that supplementing traditional backtests with comparative backtests will enhance the existing trading book regulatory framework for banks by providing the correct incentive for accuracy of risk measure forecasts. In addition, the comparative backtesting framework could be used by banks internally as well as by researchers to guide selection of forecasting methods. The discussion focuses on three risk measures, Value-at-Risk, expected shortfall and expectiles, and is supported by a simulation study and data analysis

Decrease of vanillin sucrose intake by victorious and defeated mice: development of anhedonia?

Hedonic reactions to various rewards play a key role in various forms of motivated behavior. The influence of repeated experience of social victories or defeats in daily agonistic interactions between male mice on voluntary consumption of vanillin sucrose solution used as hedonic reinforcer was studied. Intake of vanillin sucrose solution was shown to decrease in the winners and losers exposed to social confrontations as compared with the controls. Three days of deprivation failed to restore the intake of vanillin sucrose solution to the control level in the losers and did so in the winners. The results obtained imply that similar reaction of animals to a hedonic non-drug reinforcer may have different motivational origin depending on positive or negative social experience

Structurally complex Frank-Kasper phases and quasicrystal approximants: electronic origin of stability

Metal crystals with tetrahedral packing are known as Frank-Kasper phases with large unit cells with the number of atoms from hundreds to thousands. The main factors of the formation and stability of these phases are the atomic size ratio and the number of valence electrons per atom. The significance of the electronic energy contribution is analyzed within the Fermi sphere - Brillouin zone interactions model for several typical examples: Cu4Cd3, Mg2Al3 with over thousand atoms per cell, and for icosahedral quasicrystal approximants with 146 to 168 atoms per cell. Our analysis shows that to minimize the crystal energy, it is important that the Fermi sphere (FS) is in contact with the Brillouin zones that are related to the strong diffraction peaks: the zones either inscribe the FS or are circumscribed by the FS creating contact at edges or vertices.Comment: 10 pages, 3 figures, 1 tabl

Necessary conditions for linear noncooperative N-player delta differential games on time scales

We present necessary conditions for linear noncooperative N-player delta dynamic games on a generic time scale. Necessary conditions for an open-loop Nash-equilibrium and for a memoryless perfect state Nash-equilibrium are proved.Comment: Partially presented at the "Fifth Symposium on Nonlinear Analysis" (SNA 2007), Torun, Poland, September 10-14, 200

Panama's growth diagnostics

"In this context, the objective of the paper is to propose a set of recommendations on whatneeds to be done in order to assure success of the current growth strategy. We have nodoubts on the value of strengthening Panama´s geographical comparative advantage withthe Canal´s expansion. The key question is to identify the additional steps which could promote growth in the non-canal economy. In addition to making growth more sustainable,growth acceleration in the traditional sectors can result in a reduction of inequality, whichis extremely high in Panama.To answer these questions the paper proceeds in the following way. Section 2 discussessome key features of Panama´s economic structure that are important for the analysis.Section 3 analyzes Panama´s growth using conventional techniques. In particular, we lookat the role of the `fundamental´ determinants of growth, such as institutions, geography,and human capital. Also, the time series analysis shows that growth has experiencedreversals while a standard sources-of-growth decomposition suggests that Panama has asevere productivity problem. Sections 4 to 8 deal with the GDM. Section 4 presents somegeneral evidence from the Investment Climate Survey (ICS) on the main concerns ofPanama´s entrepreneurs. Section 5 discusses all the problems that could imply low socialreturns to investment. Section 6 analyzes the issues related to problems of appropriability.Section 7 introduces the problems of self-discovery, and Section 8 looks at financingissues. Section 9 concludes"Crecimiento Económico, Panamá

Anhedonia in the shadow of chronic social defeat stress, or When the experimental context matters

One of the core symptoms of major depression in human is anhedonia. For that reason, one of the main requirements towards experimental depression models is that they be able to demonstrate anhedonia in animals, that have been exposed to stressful events, and other behavioral changes attributable to a depression-like state. However, the results presented in the literature are contradictory: sweet solution intake, which is considered as a parameter of hedonic/anhedonic behavior in animals, responds quite differently to stressful situations in that it is either unaffected or increased or decreased. Different experimental designs used for the study of anhedonia in male mice exposed to chronic social defeat stress were tried to understand the reasons for so contradictory responses. Anhedonia appears as an abrupt reduction in sweet solution consumption in stressed animals and by failure to attain recovery after deprivation. However, it was also demonstrated that sucrose solution intake and preference strongly depend on the experimental context; that the possible critical factor may be prior acquaintance with the hedonic stimulus – or the lack whereof. Analysis of literature data and ours allowed us to conclude that the lack of a significant decrease in sweet solution intake in stressed animals is no evidence of lack of depression. This decrease is evidence of anhedonia only provided other symptoms of depression are present. Hedonic consumable intake can be decreased over various motivations, conditions or diseases, in particular, a high level of anxiety or pathological aggression