Spectral Geometry and Causality

For a physical interpretation of a theory of quantum gravity, it is necessary to recover classical spacetime, at least approximately. However, quantum gravity may eventually provide classical spacetimes by giving spectral data similar to those appearing in noncommutative geometry, rather than by giving directly a spacetime manifold. It is shown that a globally hyperbolic Lorentzian manifold can be given by spectral data. A new phenomenon in the context of spectral geometry is observed: causal relationships. The employment of the causal relationships of spectral data is shown to lead to a highly efficient description of Lorentzian manifolds, indicating the possible usefulness of this approach. Connections to free quantum field theory are discussed for both motivation and physical interpretation. It is conjectured that the necessary spectral data can be generically obtained from an effective field theory having the fundamental structures of generalized quantum mechanics: a decoherence functional and a choice of histories.Comment: AMS-Latex, 14 pages, 3 figures, using epsf macr

Restoring financial stability in the euro area. CEPS Policy Brief No. 237, 15 March 2011

The pricing of sovereign credit risk is a necessary component of the financial architecture of the European Monetary Union. However, unnecessarily high and volatile risk premia on government bonds are currently preventing effective financial intermediation within the euro area, thereby inhibiting its economic recovery. Several proposals have been made on how these risk premia should be brought down, namely i) permanent pooling of funding through joint bond issuance, ii) temporary liquidity assistance through multilateral funds, iii) debt buybacks using multilateral funds, and iv) debt restructuring. This paper attempts to evaluate these four proposals. It argues that joint bond issuance will not achieve a meaningful reduction of liquidity premia in the sovereign bond market; these instruments would either create perverse incentives or accelerate the sovereign debt crisis for peripheral Europe. An institution to provide temporary liquidity assistance is a necessary addition to the institutional framework of EMU – there needs to be an EMF to complement the ECB. Debt buybacks using multilateral funds can be a very useful tool for solvent countries such as Spain; they can prevent an overshooting of risk premia that could turn a sovereign liquidity crisis into a solvency crisis. A quantitative assessment shows that debt buybacks at market prices are insufficient to correct Greece’s debt overhang, however. In the case of Greece, a voluntary exchange of existing government bonds into new obligations, complemented by a buyback option at a steep discount to face value, could restore sovereign creditworthiness and allow the private sector to regain market access at acceptable interest rates. In the absence of such an orderly and controlled reduction of public debt, highly indebted euro area governments will likely opt to restructure their sovereign debt unilaterally, if they fail to regain market access after several years. This could have unwelcome consequences for financial stability in the euro area, which should be avoided through a creative and cooperative approach to the problem

Population characteristics and biology of striped marlin, Tetrapturus audax in the New Zealand fishery : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science (MSc) in Physiology at Massey University, Palmerston North, New Zealand

Striped marlin (Tetrapturus audax) are apex predators in the pelagic ecosystem and are seasonally abundant in the off-shore waters of New Zealand during December through May. Data presented in this thesis were derived from a variety of fishing databases from New Zealand, Australia and United States as well as biological samples collected from east Northland New Zealand. This thesis may be used to help answer questions about growth and size structure, factors influencing conventional tag recoveries, and the trophic dynamics of striped marlin in the New Zealand fishery. Results show that the average weight of striped marlin in the New Zealand recreational fishery has declined between 1925-1944 (117.9 ± 0.6 kg) and 1985-2003 (96.6 ± 0.3 kg) (Means ± S.E.). The root causes of this average size decline are unknown but appear to be related to the expansion of a surface longline fishery in the southwest Pacific Ocean during 1958. Despite the large average size (104.9 ± 0.2 kg) of striped marlin from New Zealand, parameters estimated in the von Bertalanffy growth model (L∞3010 mm, K=0.22 annual and t 0=-0.04) do not show higher growth rates compared to Hawaii or Mexico. During their residency in the New Zealand Exclusive Economic Zone (EEZ) the condition Wr (relative weight) of striped marlin improves from 95.1 ± 1.2 to 109.4 ± 3.4 and average weight increases from 98.1 ± 2.0 kg to 114.6 = 0.4 kg. These data imply that striped marlin migrate to New Zealand in order to take advantage of the abundant food resources and to improve condition after spawning in warmer waters to the north. Arrow squid (Nototodarus spp.), jack mackerel (Trachurus murphyi) and saury (Scomberesox saurus) comprised a large portion of the diet from (n=20) striped marlin stomachs during March of 2004. Additionally, with a consumption rate of 0.962 to 1.28 kg of prey per day, striped marlin may consume the equivalent of 2.8-3.5% of New Zealand's current commercial catch of arrow squid and jack mackerel respectively. With concerns about declining pelagic fish stocks, tag-and-recovery programmes have become increasingly popular and over 50% of recreationally captured marlin in New Zealand are tagged and released annually. However, low tag recovery rates (<1.0%) have hindered progress in understanding growth, stock structure and migration patterns important for managing this species. Data from this study suggests that tag returns from striped marlin would increase if more fish were captured and released in less than 39 min and a greater number of small (< 89 kg) individuals were released. Tag recoveries and presumably post-release survivorship of striped marlin was reduced by increasing capture time and fish size. Rates of injury were lowest during capture times ranging from 20-29 min and in fish weighing 60-89 kg

Short-term training variety for welfare recipients: the effects of different training types

"Since 2005, jobless employable individuals have to be available for the labour market with various activation programmes helping them. One major programme is short-term training teaching certain skills or assisting in job search. However, little is known about the effectiveness of such a short programme for welfare recipients. This study evaluates the effects of seven short-term training types in the introduction period of the reform in spring 2005 on the individual probability of being regularly employed. I use large German administrative datasets and propensity score matching. The results show that within-company training has large positive effects. Furthermore, skill training is more effective than other types. However, comparing skill training participants pair-wise with others does not result in consistent positive effects." (Author's abstract, IAB-Doku) ((en))Trainingsmaßnahme - Erfolgskontrolle, arbeitsmarktpolitische Maßnahme, berufliche Reintegration, Arbeitslosengeld II-Empfänger, Integrierte Erwerbsbiografien, IAB-Leistungsempfängerhistorik

Spectral Quadruples

A set of data supposed to give possible axioms for spacetimes. It is hoped that such a proposal can serve to become a testing ground on the way to a general formulation. At the moment, the axioms are known to be sufficient for cases with a sufficient number of symmetries, in particular for 1+1 de Sitter spacetime.Comment: AMS-LaTeX, 7 pages, presented at the Euroconference "BRANE NEW WORLD and Noncommutative Geometry", Torino, Villa Gualino (Italy), October 2 - 7, 200

Spectral geometry of spacetime

Spacetime, understood as a globally hyperbolic manifold, may be characterized by spectral data using a 3+1 splitting into space and time, a description of space by spectral triples and by employing causal relationships, as proposed earlier. Here, it is proposed to use the Hadamard condition of quantum field theory as a smoothness principle.Comment: AMS-LaTeX, 6 pages,Talk presented at the Euroconference on "Non-Commutative Geometry And Hopf Algebras In Field Theory And Particle Physics" Torino, Villa Gualino, September 20 - 30, 199

Zeeman-Tomography of the Solar Photosphere -- 3-Dimensional Surface Structures Retrieved from Hinode Observations

AIMS :The thermodynamic and magnetic field structure of the solar photosphere is analyzed by means of a novel 3-dimensional spectropolarimetric inversion and reconstruction technique. METHODS : On the basis of high-resolution, mixed-polarity magnetoconvection simulations, we used an artificial neural network (ANN) model to approximate the nonlinear inverse mapping between synthesized Stokes spectra and the underlying stratification of atmospheric parameters like temperature, line-of-sight (LOS) velocity and LOS magnetic field. This approach not only allows us to incorporate more reliable physics into the inversion process, it also enables the inversion on an absolute geometrical height scale, which allows the subsequent combination of individual line-of-sight stratifications to obtain a complete 3-dimensional reconstruction (tomography) of the observed area. RESULTS : The magnetoconvection simulation data, as well as the ANN inversion, have been properly processed to be applicable to spectropolarimetric observations from the Hinode satellite. For the first time, we show 3-dimensional tomographic reconstructions (temperature, LOS velocity, and LOS magnetic field) of a quiet sun region observed by Hinode. The reconstructed area covers a field of approximately 12000 by 12000 km and a height range of 510 km in the photosphere. An enormous variety of small and large scale structures can be identified in the 3-D reconstructions. The low-flux region (B_{mag} = 20G) we analyzed exhibits a number of "tube-like" magnetic structures with field strengths of several hundred Gauss. Most of these structures rapidly loose their strength with height and only a few larger structures can retain a higher field strength to the upper layers of the photosphere.Comment: accepted for A&A Letter

A new method for detecting differential item functioning in the Rasch model

Differential item functioning (DIF) can lead to an unfair advantage or disadvantage for certain subgroups in educational and psychological testing. Therefore, a variety of statistical methods has been suggested for detecting DIF in the Rasch model. Most of these methods are designed for the comparison of pre-specified focal and reference groups, such as males and females. Latent class approaches, on the other hand, allow to detect previously unknown groups exhibiting DIF. However, this approach provides no straightforward interpretation of the groups with respect to person characteristics. Here we propose a new method for DIF detection based on model-based recursive partitioning that can be considered as a compromise between those two extremes. With this approach it is possible to detect groups of subjects exhibiting DIF, which are not prespecified, but result from combinations of observed covariates. These groups are directly interpretable and can thus help understand the psychological sources of DIF. The statistical background and construction of the new method is first introduced by means of an instructive example, and then applied to data from a general knowledge quiz and a teaching evaluation