29,538 research outputs found

    Measurement of Boson Self Couplings at LEP and Search for Anomalies

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    With center of mass energies up to 209 GeV of LEP II, massive W and Z bosons can be produced in pairs and jointly with photons. This allows to study boson-boson couplings. Since the W and Z bosons are unstable and decay into fermions, two- and four-fermion final states, accompanied possibly by photons, play an important role for these measurements. The couplings of the W to other bosons have been measured to be g1Z = 0.990+0.023-0.024, kappa_gamma = 0.896+0.058-0.056, and lambda_gamma = -0.023 +0.025 -0.023. They are in agreement with the Standard Model expectation of g1Z = 1, kappa_gamma = 1, and lambda_gamma = 0. No sign for couplings of three neutral bosons, parametrized by the couplings f_i^V and h_i^V, and for anomalous couplings of four gauge bosons, parametrized by a_0, a_n and a_c has been found.Comment: LaTex, 6 pages, 9 figures, to appear in the proceedings of the Conference: XXXVII Rencontres de Moriond: Electroweak Interactions and Unified Theories. Systematics added, more recent values for the neutral triple gauge boson couplings, sign swap correction for quartic boson couplings, new limits for quartic couplings from the Z gamma gamma final state, reference adde

    Two-dimensional Holstein-Hubbard model: Critical temperature, Ising universality, and bipolaron liquid

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    The two-dimensional Holstein-Hubbard model is studied by means of continuous-time quantum Monte Carlo simulations. Using renormalization-group-invariant correlation ratios and finite-size extrapolation, the critical temperature of the charge-density-wave transition is determined as a function of coupling strength, phonon frequency, and Hubbard repulsion. The phase transition is demonstrated to be in the universality class of the two-dimensional Ising model and detectable via the fidelity susceptibility. The structure of the ground-state phase diagram and the possibility of a bipolaronic metal with a single-particle gap above TcT_c are explored.Comment: 8 pages, 9 figures; expanded version including Holstein-Hubbard result

    Bank behavior based on internal credit ratings of borrowers

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    This study examines the relation of bank loan terms like interest rates, collateral, and lines of credit to borrower risk defined by the banks' internal credit rating. The analysis is not restricted to a static view. It also incorporates rating transition and its implications on the relation. Money illusion and phenomena linked with relationship banking are discovered as important factors. The results show that riskier borrowers pay higher loan rate premiums and rely more on bank finance. Housebanks obtain more collateral and provide more finance. Caused by money illusion in times of high market interest rates loan rate premiums are relatively small whereas in times of low market interest rates they are relatively high. There was no evidence for an appropriate adjustment of loan terms to rating changes. But bank market power represented by a weighted average of credit rating before and after a rating transition serves to compensate for low earlier profits caused by phenomena of interest rate smoothing. Klassifikation: G21

    Number of bank relationships : an indicator of competition, borrower quality, or just size?

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    In this study the firms' choice of the number of bank relationships is analyzed with respect to influential factors like borrower quality, size and the existence of a close housebank relationship. Then, the number of bank relationships is used as a proxy to examine if bank competition is reflected in loan terms. It is shown that the number of bank relationships is foremost determined by borrower size and the existence of a housebank relationship. Loan rate spreads are not effected by the number of bank relationships. However, borrowers with a small number of bank relationships provide more collateral and get more credit. These effects are amplified by a housebank relationship. Housebanks get more collateral and are ready to take a larger stake in the financing of their customers

    Communicating Asset Risk: How the format of historic volatility information affects risk perception and investment decisions

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    An experiment examined the effect that the type and presentation format of information about investment options have on expectations held by investors about asset risk, returns, and volatility. Some respondents were provided with the names of investment options in addition to historical (1987-97) volatility data, and some were not. Historical volatility was presented either as a bar graph of returns per year or as a continuous density distribution of returns over the 10-year period. Risk and volatility perceptions both varied significantly as a function of type and format of information, but in different ways. Biases in risk perception, but not in volatility forecasts, affected portfolio decisions.

    The Impact of Feedback Frequency on Risk Taking: How general is the Phenomenon?

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    In a recent QJE-article, Gneezy and Potters (1997) present experimental evidence for the impact of feedback frequency on individual risk taking behavior in repeated investment decisions. They find an increased willingness to invest into a risky asset if less frequent feedback about the outcome of previous investments is provided. The observed decision pattern is explained by myopic loss aversion, a combination of mental accounting and loss aversion. In this note, we argue that the findings of Gneezy and Potters on the relationship between feedback frequency and risk taking are not as general as they might seem. We provide theoretical arguments and experimental evidence to demonstrate that the reported phenomenon is not robust to changes in the risk profiles of the given investment options.

    Determinants of Risk Taking Behavior: The role of Risk Attitudes, Risk Perceptions and Beliefs

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    Our study analyzes determinants of investors' risk taking behavior. We find that investors' risk taking behavior, i.e. portfolio choices can be predicted using risk attitudes, risk perceptions and belief measures such as optimism and overconfidence. However, the predictive power of these determinants heavily depends on the domain in which it was elicited. More specifically, risk attitudes, risk perceptions and beliefs only allow us to predict investors' risk taking behavior if they are elicited in an investment related context. We think that our results could also benefit practitioners who could incorporate some of the determinants we have used in their investment advisory process.

    Building Sector: Stimulus Packages Make an Impact

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    The sharp slump of the German economy has left its mark on the building sector. Commercial construction has been especially affected by the significant decline in companies' propensity to invest - triggered by the macroeconomic downturn. However, due to the stable development of real wages and the overall labour market as well as targeted supporting programmes, the recession has more or less bypassed residential construction. Public sector construction even increased in 2009, most notably during the later half of the year when the effects of the second stimulus package came into force. Nevertheless, due to idle capacities in commercial construction, only moderate price increases are to be expected. Overall - and in real terms - , 2009 will see little change in German construction volumes compared to the previous year. In 2010, stimulus packages will encourage a noticeable recovery, which - in turn - will have a positive effect on the country's overall economy. All in all, construction volumes are expected to grow by more than two per cent (adjusted for price) in 2010 and the main construction industry will profit disproportionately. From an economic point of view, the investment programmes thus meet their intended goal: stabilisation of the construction sector.Housing demand, Construction industry, Forecast 2010
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