Tarski monoids: Matui's spatial realization theorem

We introduce a class of inverse monoids, called Tarski monoids, that can be regarded as non-commutative generalizations of the unique countable, atomless Boolean algebra. These inverse monoids are related to a class of etale topological groupoids under a non-commutative generalization of classical Stone duality and, significantly, they arise naturally in the theory of dynamical systems as developed by Matui. We are thereby able to reinterpret a theorem of Matui on a class of \'etale groupoids as an equivalent theorem about a class of Tarski monoids: two simple Tarski monoids are isomorphic if and only if their groups of units are isomorphic. The inverse monoids in question may also be viewed as countably infinite generalizations of finite symmetric inverse monoids. Their groups of units therefore generalize the finite symmetric groups and include amongst their number the classical Thompson groups.Comment: arXiv admin note: text overlap with arXiv:1407.147

The EU Rights Based Approach to Disability: Some Strategies for Shaping an Inclusive Society

[Excerpt] The past ten years have witnessed a marked change in the legal and policy responses of many European countries, and of the EU itself, to the issue of disability. This new (and still emerging) response is often termed the ‘rights based approach’. In this paper I will attempt to clarify the nature of this approach and to suggest a number of ways in which disability organisations might work towards establishing it in their own countries. My starting point will be a brief examination of the more traditional approach to disability, however, as it is difficult to grasp the essence of the new approach without an appreciation of its contrast with the old

Atmospheric Radio Signals From Galactic Dark Matter

If the dark matter of our galaxy is composed of nuggets of quarks or antiquarks in a colour superconducting phase there will be a small but non-zero flux of these objects through the Earth's atmosphere. A nugget of quark matter will deposit only a small fraction of its kinetic energy in the atmosphere and is unlikely to be detectable. If however the impacting object is composed of antiquarks the energy deposited can be quite large and contain a significant charged particle content. These relativistic secondary particles will subsequently be deflected by the earth's magnetic field resulting in the emission of synchrotron radiation. This work will argue that this radiation should be detectable at radio frequencies and that present and proposed experiments are capable of detecting such a signal.Comment: Matches published versio

Quark Matter Induced Extensive Air Showers

If the dark matter of our galaxy is composed of nuggets of quarks or antiquarks in a colour superconducting phase there will be a small but non-zero flux of these objects through the Earth's atmosphere. A nugget of quark matter will deposit only a small fraction of its kinetic energy in the atmosphere and is likely to be undetectable. If however the impacting object is composed of antiquarks the energy deposited can be quite large. In this case nuclear annihilations within the nugget will trigger an extensive air shower the particle content of which is similar to that produced by an ultrahigh energy cosmic ray. This paper gives a qualitative description of the basic properties of such a shower. Several distinctions from an air shower initiated by a single ultra high energy nucleus will be described allowing these events to be distinguished from the cosmic ray background. The subtlety of these features may mean that some fraction of the high energy cosmic ray spectrum may in fact be due to this type of dark matter interaction. The estimated flux of dark matter nuggets and the energy deposited in the atmosphere are such that the Pierre Auger Observatory may prove an ideal facility to place constraints on the flux of heavy quark matter objects. This paper attempts to highlight the best techniques to search for a quark matter signature through an extensive air shower signal.Comment: 9 pages, 2 figures, Version accepted by Phys. Rev.

Margaret Court and the Hypocrisy of Professional Tennis

A short article calling attention to the wanton hypocrisy plaguing professional tennis

The global 1989?: the year that changed the world

As we approach the twentieth anniversary of ‘1989 and all that’, it might be worth ducking for cover. Lest we forget, the year ‘1989’ has become something of a cliché, caught in a sense of its own triumphalism, considered by all and sundry (or at least by most) to be the ur-contemporary demarcation point in world historical time, a normative, analytical and empirical referent point par excellence