Persistence in Corporate Networks

We examine the bipartite graphs of German corporate boards in 1993, 1999 and 2005, and identify cores of directors who are highly central in the entire network while being densely connected among themselves. The novel feature of this paper is the focus on the dynamics of these networks. Germany's corporate governance has experienced significant changes during this time, and there is substantial turnover in the identity of core members, yet we observe the persistent presence of a network core, which is even robust to changes in the tail distribution of multiple board memberships. Anecdotal evidence suggests that core persistence originates from the board appointment decisions of largely capitalized corporations

The Effect of Income on Democracy Revisited a Flexible Distributional Approach

We reexamine the effect of economic development on the level of democracy based on the data sets of Acemoglu et al. (2008) with a novel regression specification utilizing a zero-one-inflated beta distribution for the response variable democracy. The zero-one-inflated beta distribution is more appropriate for continuous but bounded responses with non-zero probabilities for the boundaries of the support than the other frequently used distributions such as the normal. Contrary to the results of Acemoglu et al. (2008), some support of causality is found particularly when explaining the variance of the democracy variables. Since our analysis highlights that the distribution of democracy is bimodal, we approximate the modes using two separate samples of OECD and non-OECD countries. Our results indicate that there are differences not only in the mean but also in other features of the response distribution between the two groups. For instance, higher incomes are associated with higher democracy levels in the OECD sub-sample, however for non-OECD the association is insignificant

A search for transit timing variation

Photometric follow-ups of transiting exoplanets (TEPs) may lead to discoveries of additional, less massive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. In 2009 we launched an international observing campaign, the aim of which is to detect and characterise signals of transit timing variation (TTV) in selected TEPs. The programme is realised by collecting data from 0.6--2.2-m telescopes spread worldwide at different longitudes. We present our observing strategy and summarise first results for WASP-3b with evidence for a 15 Earth-mass perturber in an outer 2:1 orbital resonance.Comment: Poster contribution to Detection and Dynamics of Transiting Exoplanets (Haute Provence Observatory Colloquium, 23-27 August 2010

How to Measure Subdiffusion Parameters

We propose a method to measure the subdiffusion parameter $\alpha$ and subdiffusion coefficient $D_{\alpha}$ which are defined by means of the relation $=\frac{2D_\alpha} {\Gamma(1+\alpha)} t^\alpha$ where $$ denotes a mean square displacement of a random walker starting from $x=0$ at the initial time $t=0$. The method exploits a membrane system where a substance of interest is transported in a solvent from one vessel to another across a thin membrane which plays here only an auxiliary role. We experimentally study a diffusion of glucose and sucrose in a gel solvent, and we precisely determine the parameters $\alpha$ and $D_{\alpha}$, using a fully analytic solution of the fractional subdiffusion equation.Comment: short version of cond-mat/0309072, to appear in Phys. Rev. Let

A near-IR [Fe II] line imaging survey of supernova remnants in M33

We report on the first near-IR [Fe II] line imaging survey of extragalactic SNRs. Observations of a sample of 42 objects drawn from an optically-selected catalogue of SNRs in M33 provide evidence for a wide range in the [Fe II] 1.644 microns luminosities. This can be understood as being primarily due to variations in the chemical abundances and density of the local ISM, although shock conditions may also play a significant role. We briefly discuss how these results may be used to better calibrate the supernova rate of star-forming galaxies.Comment: To be published in the proceedings of the conference: ``The Interstellar Medium in M31 and M33'' (E. M. Berkhuijsen and R. Beck eds.). 4 pages, 1 figur

Relic Radiation from an Evaporating Black Hole

We present a non-string-theoretic calculation of the microcanonical entropy of relic integer-spin Hawking radiation -- at fixed total energy $E$. The only conserved macroscopic quantity is the total energy $E$ (the total energy of the relic radiation). Data for a boundary-value approach, with massless, integer-spin perturbations, are set on initial and final space-like hypersurfaces. In the resulting 1-dimensional statistical-mechanics problem, the real part of the (complex) time separation at spatial infinity, $T = {\mid}T{\mid}\exp(-i\delta), \delta >0$, is the variable conjugate to the total energy. We count the number of weak-field configurations on the final space-like hypersurface with energy $E$. One recovers the Cardy formula and the Bekenstein-Hawking entropy, if Re(T) is of the order of the black-hole life- time, leading to a statistical interpretation of black-hole entropy. The microcanonical entropy includes a logarithmic correction to the black-hole area law, which is {\it universal} (independent of black-hole parameters). Here, the discreteness of the energy levels is crucial. This approach is compared with that of string theory for the transition to the fundamental-string r\'egime in the final stages of evaporation. The squared coupling, $g^2$, regulating the transition to a highly-excited string state and {\it vice versa}, can be related to the angle, $\delta$, of complex-time rotation above. The strong-coupling r\'egime corresponds to a Euclidean black hole, while the physical limit of a Lorentzian space-time (as $\delta \to 0_+$) corresponds to the weak-coupling r\'egime. This resembles the transition to a highly-excited string-like state which subsequently decays into massless particles, thereby avoiding the naked singularity.Comment: To appear in International Journal of Modern Physics

Dynamical trapping and relaxation of scalar gravitational fields

We present a framework for nonlinearly coupled scalar-tensor theory of gravity to address both inflation and core-collapse supernova problems. The unified approach is based on a novel dynamical trapping and relaxation of scalar gravity in highly energetic regimes. The new model provides a viable alternative mechanism of inflation free from various issues known to affect previous proposals. Furthermore, it could be related to observable violent astronomical events, specifically by releasing a significant amount of additional gravitational energy during core-collapse supernovae. A recent experiment at CERN relevant for testing this new model is briefly outlined.Comment: 4 pages; version to appear in PL

Abundance Uncertainties Obtained With the PizBuin Framework For Monte Carlo Reaction Rate Variations

Uncertainties in nucleosynthesis models originating from uncertainties in astrophysical reaction rates were estimated in a Monte Carlo variation procedure. Thousands of rates were simultaneously varied within individual, temperature-dependent errors to calculate their combined effect on final abundances. After a presentation of the method, results from application to three different nucleosynthesis processes are shown: the $\gamma$-process and the s-process in massive stars, and the main s-process in AGB stars (preliminary results). Thermal excitation of nuclei in the stellar plasma and the combined action of several reactions increase the final uncertainties above the level of the experimental errors. The total uncertainty, on the other hand, remains within a factor of two even in processes involving a large number of unmeasured rates, with some notable exceptions for nuclides whose production is spread over several stellar layers and for s-process branchings.Comment: 8 pages, 4 figures; Proceedings of OMEG 2017, Daejeon, Korea, June 27-30, 2017; to appear in AIP Conf. Pro