SO(5)-Symmetric Description of the Low Energy Sector of a Ladder System

We study a system of two Tomonaga-Luttinger models coupled by a small transverse hopping (a two-chain ladder). We use Abelian and non-Abelian bosonisation to show that the strong coupling regime at low energies can be described by an SO(5)$_1$ WZW model (or equivalently 5 massless Majorana fermions) deformed by symmetry breaking terms that nonetheless leave the theory critical at T=0. The SO(5) currents of the theory comprise the charge and spin currents and linear combinations of the so-called pi operators (S.C. Zhang, Science 275, 1089 (1997)) which are local in terms both of the original fermions and those of the effective theory. Using bosonisation we obtain the asymptotic behaviour of all correlation functions. We find that the 5 component ``superspin'' vector has power law correlations at T=0; other fermion bilinears have exponentially decaying correlations and the corresponding tendencies are suppressed. Conformal field theory also allows us to obtain the energies, quantum numbers, and degeneracies of the low-lying states and fit them into deformed SO(5) multiplets.Comment: 17 pages, ReVTeX, 1 eps figure include

High field magnetotransport in composite conductors: the effective medium approximation revisited

The self consistent effective medium approximation (SEMA) is used to study three-dimensional random conducting composites under the influence of a strong magnetic field {\bf B}, in the case where all constituents exhibit isotropic response. Asymptotic analysis is used to obtain almost closed form results for the strong field magnetoresistance and Hall resistance in various types of two- and three-constituent isotropic mixtures for the entire range of compositions. Numerical solutions of the SEMA equations are also obtained, in some cases, and compared with those results. In two-constituent free-electron-metal/perfect-insulator mixtures, the magnetoresistance is asymptotically proportional to $|{\bf B}|$ at {\em all concentrations above the percolation threshold}. In three-constituent metal/insulator/superconductor mixtures a line of critical points is found, where the strong field magnetoresistance switches abruptly from saturating to non-saturating dependence on $|{\bf B}|$, at a certain value of the insulator-to-superconductor concentration ratio. This transition appears to be related to the phenomenon of anisotropic percolation.Comment: 16 pages, 3 figure

An Asymmetric B Factory at 10^(36) Luminosity

The physics opportunities at an asymmetric B Factory operating at the unprecedented luminosity of 10^(36) cm^(–2) s^(–1) are unique and attractive. The accelerator appears to be practical and the challenges of performing a sensitive experiment in this environment can be met

Sir Henry Thomas De la Beche and the founding of the British Geological Survey

The founding of the Geological Survey by Henry De la Beche in 1835 is a key event in the history of British geology. Yet the Survey’s initiation actually began three years earlier when De la Beche secured financial assistance from the Board of Ordnance to map the geology of Devon at a scale of one inch to the mile. The British Geological Survey has thus been in existence for at least 175 years and can justly claim to be the world’s oldest continuously functioning geological survey organisation. There were early government-funded geological surveys also in France, the United States, Ireland and Scotland. De la Beche’s notable success both in launching and sustaining the Geological Survey demanded a good deal of diplomacy, determination and deviousness! Even so, the Survey was nearly brought to an untimely end in 1837 when De la Beche was publicly criticised for his interpretation, based on lithology and field relations, of the difficult Culm strata of north Devon. The resolution of the ‘Devonian Controversy’ led to a fundamental change in geological practice, in which the value of fossils as stratigraphic markers, founded on an acceptance of organic change over time, was established beyond question. Fortunately the Survey survived its early trauma and De la Beche went on to extend his influence with the expansion of the Museum of Economic Geology (also formed in 1835), and the establishment of the Mining Record Office and the School of Mines

Common Sense is Not Common. So How Can A Leader Make Good Decisions?

In education today there is a move away from top-down leadership toward a more inclusive, shared or participative leadership model. This model includes shared decision-making, which has the potential to empower and radically change any organization willing to take the risk of implementing this type of leadership. This article combines another important aspect of leadership to the concept of shared decision-making: servant leadership. With a servant-leader at the helm and shared decision-making in place, a school has the potential to grow in sync with the needs and desires of its stakeholders