Are there MACHOs in the Milky Way halo?

Microlensing searches aim to detect compact halo dark matter via its gravitational lensing effect on stars within the Large Magellanic Cloud. The most recent results have led to the claim that roughly one fifth of the galactic halo dark matter may be in the form of compact, solar-mass objects. We analyze this hypothesis by considering the goodness-of-fit of the best-fit halo dark matter solutions to the observational data. We show that the distribution of the durations of the observed microlensing events is narrower than that expected to result from a standard halo lens population at 90 to 95% confidence. Only when the fraction of expected background (non-halo) events is significantly increased does the discrepancy between the observed and theoretical event duration distributions disappear. This indicates that it is possible that most of the lenses responsible for the observed microlensing events are not located within the Milky Way halo.Comment: 5 pages, 2 figures, minor changes to discussion and additional references, version to appear in Astronomy and Astrophysic

Are financial services over-regulated?

As the Equitable Life saga drags on, accounting scandals break over Enron and WorldCom and allegations of self-serving analysts reports swirl around Merrill Lynch and other US investment banks, this may seem an extraordinary question to ask. But this is the very time that one must beware of the ‘dangerous dogs’ reaction1. It is easy to forget in the immediate aftermath of scandals that extra regulation may achieve little beyond satisfying the call for ‘something to be done’ and can cumulatively cost a lot, even perversely increase the chances of future disasters2. With the EU’s Financial Services Action Plan, the DTI’s consultation on Company Law, the Sandler review of savings and the FSA’s review of polarisation, Listing Rules and simplified product selling, the opportunity for radical change, good or bad, is all to apparent. This article seeks to give an overview of the current position and assess the danger of an over-reaction

Not enough stellar mass Machos in the Galactic halo

We present an update of results from the search for microlensing towards the Large Magellanic Cloud (LMC) by EROS (Experience de Recherche d'Objets Sombres). We have now monitored 25 million stars over three years. Because of the small number of observed microlensing candidates (four), our results are best presented as upper limits on the amount of dark compact objects in the halo of our Galaxy. We discuss critically the candidates and the possible location of the lenses, halo or LMC . We compare our results to those of the MACHO group. Finally, we combine these new results with those from our search towards the Small Magellanic Cloud as well as earlier ones from the EROS1 phase of our survey. The combined data is sensitive to compact objects in the broad mass range $10^{-7} - 10$ solar masses. The derived upper limit on the abundance of stellar mass MACHOs rules out such objects as the dominant component of the Galactic halo if their mass is smaller than 2 solar masses.Comment: 7 pages, 4 figures, presented at the XIX International Conference on Neutrino Physics and Astrophysics, Sudbury, Canada, June 200

Devolution or divergence? Third Sector policy across the UK since 2000

Since the end of the last century the United Kingdom has been a less united country than it was. In 1999 a separate Scottish Executive (from 2007 the Scottish Government) and Welsh Assembly Government were established, followed later by a new Northern Ireland Executive and Assembly, based on a power sharing agreement known from its date in 1998 as the ‘Good Friday Agreement’. A number of key policy making powers were devolved from Westminster to these new administrations; these include policy on and support for third sector activity in the different countries. Since 2000 therefore there have in effect been four separate policy regimes within the UK focused on the activity and organisation of third sector organisations, although, compared to the greater levels of regional devolution existing in many other developed industrial nations, the UK remains a largely centralised state in both political and policy terms. This paper explores some of the key implications of this recent devolution and examines the extent to which it has led to a divergence in policy development and delivery – asking the question, to what extent has devolution led to a divergence in third sector policy regimes across the UK

Market abuse

On 1st December 2001, the Financial Services and Markets Act 2000 (‘FSMA’) came into force. One of its most controversial sections is Part VIII which gives the Financial Services Authority (‘FSA’) the power to impose civil penalties for market abuse. Despite the many doubts raised about these provisions and their as yet untested nature, the European Commission has proposed a European Directive on Market Abuse1, to extend the concept of ‘administrative sanctions’ for market abuse across the whole European Economic Area (‘EEA’). This paper looks at the issues currently raised by the UK legislation and any further problems the European legislation may bring

Gravitational Microlensing by the Ellis Wormhole

A method to calculate light curves of the gravitational microlensing of the Ellis wormhole is derived in the weak-field limit. In this limit, lensing by the wormhole produces one image outside the Einstein ring and one other image inside. The weak-field hypothesis is a good approximation in Galactic lensing if the throat radius is less than $10^{11} km$. The light curves calculated have gutters of approximately 4% immediately outside the Einstein ring crossing times. The magnification of the Ellis wormhole lensing is generally less than that of Schwarzschild lensing. The optical depths and event rates are calculated for the Galactic bulge and Large Magellanic Cloud fields according to bound and unbound hypotheses. If the wormholes have throat radii between 100 and $10^7 km$, are bound to the galaxy, and have a number density that is approximately that of ordinary stars, detection can be achieved by reanalyzing past data. If the wormholes are unbound, detection using past data is impossible.Comment: 27 pages, 4 figures, ApJ accepte

Aid, development and English language teaching : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Development Studies at Massey University, Palmerston North, New Zealand

The past few decades have seen the ascendancy of English as the global language of business and international interaction and as a result it has come to be viewed in the minds of many policy makers as fundamental to development. Accordingly English language instruction programmes have increasingly been integrated into development programmes both at a domestic recipient and international donor level. These programmes are frequently framed within the paradigms of empowerment and capacity building yet little readily accessible research seems to be available regarding the practical role English language aid programmes may play in these processes with most examination seeming to be centred either on discourse debate or cost/benefit analysis of programmes. This thesis endeavours to examine the perceptions of recipients and providers regarding the provision of English language instruction programmes. It finds that despite a provider focus on institutional capacity building extrinsic, primarily economic, considerations ensure that there is a strong recipient demand for these programmes. It also finds that, even with an increasing provider desire to use participatory paradigms, programme parameters are still largely determined by providers due to their control of funds. By reason of this the efficacy of English language instruction in promoting recipient empowerment and capacity building remains open to question

Magellanic Cloud Gravitational Microlensing Results: What Do They Mean?

I review recent results from gravitational microlensing surveys of the Large Magellanic Cloud. The combined microlensing optical depth of the MACHO and EROS-1 surveys is tau_LMC = 2.1{+1.3/-0.8}* 10^{-7} which is substantially larger than the background of tau < 0.5* 10^{-7} from lensing by known stars but is below the expected microlensing optical depth of tau = 4.7*10^{-7} for a halo composed entirely of Machos. The simplest interpretation of this result is that nearly half of the dark halo is composed of Machos with a typical mass of order 0.5 Msun. These Machos could be old white dwarfs, but it is not obvious that the generation of stars that preceded these white dwarfs could have gone undetected. Perhaps, the Machos could be non-baryonic, but there is no compelling model for the formation of non-baryonic Machos. Therefore, some authors have tried to develop alternative models which attempt to explain the LMC microlensing results with non-halo lenses. Many of these models postulate previously unknown dark stellar populations which contribute significantly to the total mass of the Galaxy and are therefore simply variations of the dark matter solution. However, models which postulate an unknown dwarf galaxy along the line of sight to the LMC or a distortion of the LMC which significantly enhances the LMC self-lensing optical depth can potentially explain the LMC lensing results with only a small amount of mass, so these can be regarded as true non-dark matter solutions to the Macho puzzle. All such models that have been proposed so far have serious problems, so there is as yet no compelling alternative to the dark matter interpretation. However, the problem can be solved observationally with a second generation gravitational microlensing survey that is significantly more sensitive than current microlensing surveys.Comment: 12 pages, to appear in the Proceedings of the 3rd International Symposium on Sources and Detection of Dark Matter in the Universe (DM98), Feb. 1998, ed. D. Clin

The Sagittarius dwarf galaxy as a microlensing target

We estimate the optical depth, time-scale distribution and fraction of microlensing events originating from sources in the Sagittarius dwarf galaxy (Sgr) lensed by deflectors in the Milky Way. These events have a time-scale longer by a factor ~1.3 than the MW/MW events and occur mainly on sources fainter than V~21 mag below Sgr's turn off. The fraction of events involving a source in Sgr depends on the location and extinction of the field and on the limiting magnitude of the survey. The contribution of the MW/Sgr events is negligible (<1%) at very low latitudes (|b|<2 deg.) but increases continuously towards higher |b| and becomes dominant near the highest density region of the dwarf galaxy. Sgr is present within the fields of current microlensing surveys and any optical depth map inferred from observations will become biased by the presence of Sgr towards higher |b| where the contribution of MW/Sgr events is significant. Systematic spectroscopic measurements on the sources of all the microlensing events may allow detection of this kind of event for which the degeneracy on the lens mass can be significantly reduced.Comment: 9 pages, 8 figures. Accepted for publication in A&A Main Journa