Risk Spillovers and Hedging: Why Do Firms Invest Too Much in Systemic Risk?

In this paper we show that free entry decisions may be socially inefficient, even in a perfectly competitive homogeneous goods market with non-lumpy investments. In our model, inefficient entry decisions are the result of risk-aversion of incumbent producers and consumers, combined with incomplete financial markets which limit risk-sharing between market actors. Investments in productive assets affect the distribution of equilibrium prices and quantities, and create risk spillovers. From a societal perspective, entrants underinvest in technologies that would reduce systemic sector risk, and may overinvest in risk-increasing technologies. The inefficiency is shown to disappear when a complete financial market of tradable risk-sharing instruments is available, although the introduction of any individual tradable instrument may actually decrease efficiency. We therefore believe that sectors without well-developed financial markets will benefit from sector-specific regulation of investment decisions.investments in productive assets;hedging;systemic risk;risk spillovers

Reinvoking the past in the present: changing identities and appropriations of Joshua Nkomo in post-colonial Zimbabwe

This article discusses the histories, narratives and representations that have been produced by and on former ZAPU leader and Vice-President of Zimbabwe, Joshua Nkomo. We focus on the multiple identities and subject positions that Nkomo came to inhabit in the way in which he was represented in ZANU-PF’s discourse of the early 1980s; his self-representation in Nkomo’s 1984 autobiography Nkomo: the story of my life and subsequent appropriations of Nkomo by different political actors in the early 2000s. In line with Stuart Hall’s 1996 description, we consider identities not as essentialist and fixed categories but as positional, multiple, constantly evolving and constructed through difference. We argue that the changing identities of Nkomo served the purposes and interests of a variety of political actors, ranging from the ruling party ZANU-PF to the opposition MDC. Against the background of a mushrooming of popular historical narratives evidenced by both the publication and republishing of biographies, autobiographies and significant reports, and the serialisation and recirculation of these texts in newspapers and through websites, we also argue that the many uses and appropriations of Nkomo demonstrate the continued relevance of the past in the power struggles waged by different political actors in Zimbabwe

A comprehensive population synthesis study of post-common envelope binaries

We apply population synthesis techniques to calculate the present day population of post-common envelope binaries (PCEBs) for a range of theoretical models describing the common envelope (CE) phase. Adopting the canonical energy budget approach we consider models where the ejection efficiency, \alpha_{\rmn{CE}} is either a constant, or a function of the secondary mass. We obtain the envelope binding energy from detailed stellar models of the progenitor primary, with and without the thermal and ionization energy, but we also test a commonly used analytical scaling. We also employ the alternative angular momentum budget approach, known as the $\gamma$-algorithm. We find that a constant, global value of \alpha_{\rmn{CE}} \ga 0.1 can adequately account for the observed population of PCEBs with late spectral-type secondaries. However, this prescription fails to reproduce IK Pegasi, which has a secondary with spectral type A8. We can account for IK Pegasi if we include thermal and ionization energy of the giant's envelope, or if we use the $\gamma$-algorithm. However, the $\gamma$-algorithm predicts local space densities that are 1 to 2 orders of magnitude greater than estimates from observations. In contrast, the canonical energy budget prescription with an initial mass ratio distribution that favours unequal initial mass ratios gives a local space density which is in good agreement with observations, and best reproduces the observed distribution of PCEBs. Finally, all models fail to reproduce the sharp decline for orbital periods, P_{\rmn{orb}} \ga 1 d in the orbital period distribution of observed PCEBs, even if we take into account selection effects against systems with long orbital periods and early spectral-type secondaries.Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Society. 18 pages, 10 figures. Work concerning the reconstruction of the common envelope phase presented in the previous version will now be submitted in a separate paper in the near futur

Superconducting phase formation in random neck syntheses: a study of the Y-Ba-Cu-O system by magneto-optics and magnetometry

Magneto-optical imaging and magnetization measurements were applied to investigate local formation of superconducting phase effected by a random neck synthesis in Y-Ba-Cu-O system. Polished pellets of strongly inhomogeneous ceramic samples show clearly the appearance of superconducting material in the intergrain zones of binary primary particles reacted under different conditions. Susceptibility measurements allows evaluation of superconducting critical temperature, which turned out to be close to that of optimally doped YBCO.Comment: 6 pages, 11 figure

Thermal distortions of non-Gaussian beams in Fabry–Perot cavities

Thermal effects are already important in currently operating interferometric gravitational wave detectors. Planned upgrades of these detectors involve increasing optical power to combat quantum shot noise. We consider the ramifications of this increased power for one particular class of laser beams—wide, flat-topped, mesa beams. In particular we model a single mesa beam Fabry–Perot cavity having thermoelastically deformed mirrors. We calculate the intensity profile of the fundamental cavity eigenmode in the presence of thermal perturbations, and the associated changes in thermal noise. We also outline an idealized method of correcting for such effects. At each stage we contrast our results with those of a comparable Gaussian beam cavity. Although we focus on mesa beams the techniques described are applicable to any azimuthally symmetric system