Radio-loudness in black hole transients: evidence for an inclination effect

Accreting stellar-mass black holes appear to populate two branches in a radio:X-ray luminosity plane. We have investigated the X-ray variability properties of a large number of black hole low-mass X-ray binaries, with the aim of unveiling the physical reasons underlying the radio-loud/radio-quiet nature of these sources, in the context of the known accretion-ejection connection. A reconsideration of the available radio and X-ray data from a sample of black hole X-ray binaries confirms that being radio-quiet is the more normal mode of behaviour for black hole binaries. In the light of this we chose to test, once more, the hypothesis that radio loudness could be a consequence of the inclination of the X-ray binary. We compared the slope of the `hard-line' (an approximately linear correlation between X-ray count rate and rms variability, visible in the hard states of active black holes), the orbital inclination, and the radio-nature of the sources of our sample. We found that high-inclination objects show steeper hard-lines than low-inclination objects, and tend to display a radio-quiet nature (with the only exception of V404 Cyg), as opposed to low-inclination objects, which appear to be radio-loud(er). While in need of further confirmation, our results suggest that - contrary to what has been believed for years - the radio-loud/quiet nature of black-hole low mass X-ray binaries might be an inclination effect, rather than an intrinsic source property. This would solve an important issue in the context of the inflow-outflow connection, thus providing significant constraints to the models for the launch of hard-state compact jets.Comment: 16 pages, 6 figures, accepted for pubblication on MNRA

An Experimental Study of Storable Votes

The storable votes mechanism is a method of voting for committees that meet periodically to consider a series of binary decisions. Each member is allocated a fixed budget of votes to be cast as desired over the multiple decisions. Voters are induced to spend more votes on those decisions that matter to them most, shifting the ex ante probability of winning away from decisions they value less and towards decisions they value more, typically generating welfare gains over standard majority voting with non-storable votes. The equilibrium strategies have a very intuitive feature---the number of votes cast must be monotonic in the voter's intensity of preferences---but are otherwise difficult to calculate, raising questions of practical implementation. In our experiments, realized efficiency levels were remarkably close to theoretical equilibrium predictions, while subjects adopted monotonic but off-equilibrium strategies. We are lead to conclude that concerns about the complexity of the game may have limited practical relevance.

Women and Nationalism in Indigenous Irish Filmmaking of the Silent Period

Women in Ireland came into focus and onto the political stage during and as a result of nationalist and socialist movements that began in the mid-1700s and continued through the 1920s. Women like Anna Parnell, Constance Markievicz, and Hannah Sheehy-Skeffington participated in the land wars, struggles for independence from Britain and the suffragist movement. Indigenous silent feature filmmaking in Ireland was born out of this critical period of political and social change. From 1916 to 1935, Irish filmmakers produced over forty silent feature films only six of which have survived. A close study of these films, fragments of three others, and contemporary film reviews and archival synopses of the non-surviving films reveals how early Irish silent films tackled nationalist issues, but did little to represent the active participation of women. Women in these films are passive sisters, lovers, and mothers, impacted by rather than impacting historical events. This is not surprising. Irish silent cinema was a male-dominated industry with a nationalist agenda that perpetuated gender stereotypes. This study links nationalism and women in Irish silent cinema by looking at how female representation in these early films reflected a gendered ideology that existed in Irish culture alongside other narratives of the nation

Evolution of the bursting-layer wave during a Type 1 X-ray burst

In a popular scenario due to Heyl, quasi periodic oscillations (QPOs) which are seen during type 1 X-ray bursts are produced by giant travelling waves in neutron-star oceans. Piro and Bildsten have proposed that during the burst cooling the wave in the bursting layer may convert into a deep crustal interface wave, which would cut off the visible QPOs. This cut-off would help explain the magnitude of the QPO frequency drift, which is otherwise overpredicted by a factor of several in Heyl's scenario. In this paper, we study the coupling between the bursting layer and the deep ocean. The coupling turns out to be weak and only a small fraction of the surface-wave energy gets transferred to that of the crustal-interface wave during the burst. Thus the crustal-interface wave plays no dynamical role during the burst, and no early QPO cut-off should occur.Comment: 8 pages, submitted to MNRA

Trading Votes for Votes: A Laboratory Study

Vote trading is ubiquitous in committees and legislatures, and yet we know very little about its properties. We explore this subject with a laboratory experiment. We propose a model of vote trading in which pairs of voters exchange votes whenever doing so is mutually advantageous. The resulting trading dynamics always converge to stable vote allocations–allocations where no further improving trades exist. The data show that stability has predictive power: vote allocations in the lab converge towards stable allocations, and individual vote holdings at the end of trading are in line with theoretical predictions. There is less support for the finer details of the trade-by-trade dynamics

An Experimental Study of Vote Trading

Vote trading is believed to be ubiquitous in committees and legislatures, and yet we know very little of its properties. We return to this old question with a laboratory experiment. We posit that pairs of voters exchange votes whenever doing so is mutually advantageous. This generates trading dynamics that always converge to stable vote allocations--allocations where no further improving trades exist. The data show that stability has predictive power: vote allocations in the lab converge towards stable allocations, and individual vote holdings at the end of trading are in line with theoretical predictions. However, there is only weak support for the dynamic trading process itself

Trading Votes for Votes: A Laboratory Study

Vote trading is ubiquitous in committees and legislatures, and yet we know very little about its properties. We explore this subject with a laboratory experiment. We propose a model of vote trading in which pairs of voters exchange votes whenever doing so is mutually advantageous. The resulting trading dynamics always converge to stable vote allocations–allocations where no further improving trades exist. The data show that stability has predictive power: vote allocations in the lab converge towards stable allocations, and individual vote holdings at the end of trading are in line with theoretical predictions. There is less support for the finer details of the trade-by-trade dynamics

An XML representation of DAE systems obtained fromcontinuous-time Modelica models

This contribution outlines an XML format for representation of differential-algebraic equations (DAE) models obtained from continuous time Modelica models and possibly also from other equation-based modeling languages. The purpose is to offer a standardized model exchange format which is based on the DAE formalism and which is neutral with respect to model usage. Many usages of models go beyond what can be obtained from an execution interface offering evaluation of the model equations for simulation purposes. Several such usages arise in the area of control engineering, where dynamic optimization, Linear Fractional Transformations (LFTs), derivation of robotic controllers, model order reduction, and real time code generation are some examples. The choice of XML is motivated by its de facto standard status and the availability of free and efficient tools. Also, the XSLT language enables a convenient specification of the transformation of the XML model representation into other formats