A Threshold Model of Real US GDP and the Problem of Constructing Confidence Intervals in TAR Models

We estimate real U.S. GDP growth as a threshold autoregressive process, and construct confidence intervals for the parameter estimates. However, there are various approaches that can be used in constructing the confidence intervals. Specifically, standard- t , bootstrap- t , and bootstrap-percentile confidence intervals are simulated for the slope coefficients and the estimated threshold. However, the results for the different methods have very different economic implications. We perform a Monte Carlo experiment to evaluate the various methods.Bootstrap GDP; Threshold Autoregression; Bootstrap Confidence Intervals

Spectral triples and Toeplitz operators

We give examples of spectral triples, in the sense of A. Connes, constructed using the algebra of Toeplitz operators on smoothly bounded strictly pseudoconvex domains in $C^n$, or the star product for the Berezin-Toeplitz quantization. Our main tool is the theory of generalized Toeplitz operators on the boundary of such domains, due to Boutet de Monvel and Guillemin.Comment: 31 page

The macroeconomic effects of exogenous fiscal policy shocks in Germany: a disaggregated SVAR analysis

We investigate the short-term effects of fiscal policy shocks on the German economy following the SVAR approach by Blanchard and Perotti (2002). We find that direct government expenditure shocks increase output and private consumption on impact with low statistical significance, while they decrease private investment, though insignificantly. For the sub-category government investment – in contrast to government consumption – a positive output effect is found, which is statistically significant until 12 quarters ahead. Allowing for anticipation effects of fiscal policy does not change the sign of the positive consumption response. Anticipated expenditure shocks have significant effects on output when the shock is realized, but not in the period of anticipation. In sum, effects of expenditure shocks are only short-lived. Government net revenue shocks do not affect output with statistical significance. However, when splitting up this aggregate, direct taxes lower output significantly, while small indirect tax revenue shocks have little effects. Compensation of public employees is equally not effective in stimulating the economy. --Fiscal policy,government spending,net revenue,policy anticipation,structural vector autoregression

Induction of IL 2 receptor expression and cytotoxicity of thymocytes by stimulation with TCF1

We investigated the role of T cell cytotoxicity inducing factor 1 (TCF1) in the induction of a cytotoxic T cell response. We found that help-deficient thymocyte cultures supplied with saturating amounts of purified IL 2 did not develop CTL in a 5-day culture. The expression of cytotoxicity was dependent on the addition of TCF1 derived from the T cell hybridoma K15. TCF1 also induced proliferation of thymocytes in the presence of IL 2. Only the PNA- thymocyte subpopulation responded to TCF1 with proliferation and cytotoxicity in the presence of IL 2. The monokine IL 1 also induced proliferation in this subpopulation but failed to induce cytotoxicity. IL 1 was further distinguished from TCF1 by inhibition of IL 1-induced but not TCF1-induced proliferation by anti-IL 1 antibodies. In addition, using anti-IL 2 receptor antibodies (AMT 13), we showed that TCF1 in the presence of IL 2 substantially increased IL 2 receptor expression in thymocytes. IL 1 had the same effect on induction of IL 2 receptor expression as TCF1. Because some effects of IL 1 and TCF1 are distinct and some overlap, we discuss whether IL 1 and TCF1 induce different subsets of PNA- thymocytes

Comparison of 1/mQ^2 Corrections in Mesons and Baryons

We extend our relativistic quark model to the study of the decay Lambda_b -> Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry constraints at order 1/mQ^2. We isolate a strong dependence on a parameter which measures the relative distortion in the light-quark wave functions of the Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be small. The dependence on a corresponding parameter in the meson case leads to large 1/mQ^2 corrections.Comment: 9 pages, LaTeX, 3 self-contained LaTeX figures in separate fil

Higher Order 1/m1/m Corrections at Zero Recoil

The general structure of the $1/m$ corrections at zero recoil is studied. The relevant matrix elements are forward matrix elements of local higher dimensional operators and their time ordered products with higher order terms from the Lagrangian. These matrix elements may be classified in a simple way and the analysis at the non recoil point for the form factor of heavy quark currents simplifies drastically. The second order recoil corrections to the form factor $h_{A1}$ of the axial vector current, relevant for the $|V_{cb}|$ determination from $B \to D^*$ decays, are estimated to be $-5\% < h_{A1} - 1 < 0$.Comment: LaTeX, 25 pages, one figure, appended after \end{document} as uu-encoded and compressed eps file, uses epsf, CERN-TH.7162/9

Moral hazard and bail-out in fiscal federations: evidence for the German Länder

We identify investor moral hazard in the German fiscal federation. Our identification strategy is based on a variable, which was used by the German Federal Constitutional Court as an indicator to determine eligibility of two German states (Länder) to a bail-out, the interest payments-to-revenue ratio. While risk premia measured in the German sub-national bond market react significantly to the relative debt level of a state (Land), we also find that a larger interest payments-to-revenue ratio counter-intuitively lowers risk premia significantly. Furthermore, with increasing values the risk premia decrease more strongly. This is evidence of investor moral hazard, because a larger indicator value increases the likelihood of receiving a bail-out payment. Quantitatively, the effects are, however, quite small. Our findings are robust to a variety of sample changes. In addition, we provide a case study of the recent Federal Constitutional Court ruling on the Land Berlin, which had filed for additional federal funds. The negative response of the court did not lead to a change in financial markets' bail-out expectations. In sum, our results indicate significant investor moral hazard in the sub-national German bond market. --moral hazard,bail-out,sovereign bond spreads,fiscal federalism,Germany

Dissipative Visco-plastic Deformation in Dynamic Fracture: Tip Blunting and Velocity Selection

Dynamic fracture in a wide class of materials reveals "fracture energy" $\Gamma$ much larger than the expected nominal surface energy due to the formation of two fresh surfaces. Moreover, the fracture energy depends on the crack velocity, $\Gamma=\Gamma(v)$. We show that a simple dynamical theory of visco-plasticity coupled to asymptotic pure linear-elasticity provides a possible explanation to the above phenomena. The theory predicts tip blunting characterized by a dynamically determined crack tip radius of curvature. In addition, we demonstrate velocity selection for cracks in fixed-grip strip geometry accompanied by the identification of $\Gamma$ and its velocity dependence.Comment: 4 pages, 1 figures; presentation improved, refs. changed, figure omitte