Specialist knowledge practices of craftsmen and clerics in Senegal

Special Issue: Knowledge in Practice: Expertise and the Transmission of Knowledge. Guest Editor: Kai Kresse and Trevor H. J. MarchandThis article examines the specialized knowledge practices of two sets of culturally recognized ‘experts’ in Senegal: Islamic clerics and craftsmen. Their respective bodies of knowledge are often regarded as being in opposition, and in some respects antithetical, to one another. The aim of this article is to examine this claim by means of an investigation of how knowledge is conceived by each party. The analysis attempts to expose local epistemologies, which are deduced from an investigation of ‘expert’ knowledge practices and indigenous claims to knowledge. The social processes of knowledge acquisition and transmission are also examined with reference to the idea of initiatory learning. It is in these areas that commonalities between the bodies of knowledge and sets of knowledge practices are to be found. Yet, despite parallels between the epistemologies of both bodies of expertise and between their respective modes of knowledge transmission, the social consequences of ‘expertise’ are different in each case. The hierarchical relations of power that inform the articulation of the dominant clerics with marginalized craftsmen groups serve to profile ‘expertise’ in different ways, each one implying its own sense of authority and social range of legitimacy.Publisher PDFPeer reviewe

Naturally heavy superpartners and a Little Higgs

We construct an extension of the MSSM in which scalar superpartners can naturally be as heavy as 1 TeV. In the MSSM, the most significant fine tuning stems from the logarithmically enhanced top-stop loop contribution to the soft Higgs mass. We combine supersymmetry with the "simplest little Higgs" to render this loop finite, thereby removing the large logarithm even in models in which superpartner masses are generated at high scales such as in supergravity. Our model predicts an extended Higgs sector, superpartner masses near a TeV and little Higgs partners at a few TeV.Comment: 18 pages, 1 figur

A hidden solution to the mu/B_mu problem in gauge mediation

We propose a solution to the mu/B_mu problem in gauge mediation. The novel feature of our solution is that it uses dynamics of the hidden sector, which is often present in models with dynamical supersymmetry breaking. We give an explicit example model of gauge mediation where a very simple messenger sector generates both mu and B_mu at one loop. The usual problem, that B_mu is then too large, is solved by strong renormalization effects from the hidden sector which suppress B_mu relative to mu. Our mechanism relies on an assumption about the signs of certain incalculable anomalous dimensions in the hidden sector. Making these assumptions not only allows us to solve the mu/B_mu problem but also leads to a characteristic superpartner spectrum which would be a smoking gun signal for our mechanism.Comment: minor clarifications, examples added, version to appear in PR

Froissart Bound on Total Cross-section without Unknown Constants

We determine the scale of the logarithm in the Froissart bound on total cross-sections using absolute bounds on the D-wave below threshold for $\pi\pi$ scattering. E.g. for $\pi^0 \pi^0$ scattering we show that for c.m. energy $\sqrt{s}\rightarrow \infty$, $\bar{\sigma}_{tot}(s,\infty)\equiv s\int_{s} ^{\infty} ds'\sigma_{tot}(s')/s'^2 \leq \pi (m_{\pi})^{-2} [\ln (s/s_0)+(1/2)\ln \ln (s/s_0) +1]^2$ where $m_\pi^2/s_0= 17\pi \sqrt{\pi/2}$ .Comment: 6 page

Froissart Bound on Inelastic Cross Section Without Unknown Constants

Assuming that axiomatic local field theory results hold for hadron scattering, Andr\'e Martin and S. M. Roy recently obtained absolute bounds on the D-wave below threshold for pion-pion scattering and thereby determined the scale of the logarithm in the Froissart bound on total cross sections in terms of pion mass only. Previously, Martin proved a rigorous upper bound on the inelastic cross-section $\sigma_{inel}$ which is one-fourth of the corresponding upper bound on $\sigma_{tot}$, and Wu, Martin,Roy and Singh improved the bound by adding the constraint of a given $\sigma_{tot}$. Here we use unitarity and analyticity to determine, without any high energy approximation, upper bounds on energy averaged inelastic cross sections in terms of low energy data in the crossed channel. These are Froissart-type bounds without any unknown coefficient or unknown scale factors and can be tested experimentally. Alternatively, their asymptotic forms,together with the Martin-Roy absolute bounds on pion-pion D-waves below threshold, yield absolute bounds on energy-averaged inelastic cross sections. E.g. for $\pi^0 \pi^0$ scattering, defining $\sigma_{inel}=\sigma_{tot} -\big (\sigma^{\pi^0 \pi^0 \rightarrow \pi^0 \pi^0} + \sigma^{\pi^0 \pi^0 \rightarrow \pi^+ \pi^-} \big )$,we show that for c.m. energy $\sqrt{s}\rightarrow \infty$, $\bar{\sigma}_{inel }(s,\infty)\equiv s\int_{s} ^{\infty } ds'\sigma_{inel }(s')/s'^2 \leq (\pi /4) (m_{\pi })^{-2} [\ln (s/s_1)+(1/2)\ln \ln (s/s_1) +1]^2$ where $1/s_1= 34\pi \sqrt{2\pi }\>m_{\pi }^{-2}$ . This bound is asymptotically one-fourth of the corresponding Martin-Roy bound on the total cross section, and the scale factor $s_1$ is one-fourth of the scale factor in the total cross section bound. The average over the interval (s,2s) of the inelastic $\pi^0 \pi^0$cross section has a bound of the same form with $1/s_1$ replaced by $1/s_2=2/s_1$.Comment: 9 pages. Submitted to Physical Review

Maximally Realistic Causal Quantum Mechanics

We recently constructed a causal quantum mechanics in 2 dim. phase space which is more realistic than the de Broglie-Bohm mechanics as it reproduces not just the position but also the momentum probability density of ordinary quantum theory. Here we present an even more ambitious construction in 2n dim. phase space. We conjecture that the causal Hamiltonian quantum mechanics presented here is `maximally realistic'. The positive definite phase space density reproduces as marginals the correct quantum probability densities of $n+1$ different complete commuting sets of observables (e.g. $\vec q$, $\vec p$ and $n-1$ other sets). In general the particle velocities do not coincide with the de Broglie-Bohm velocities.Comment: Published versio

Loop Quantum Gravity and the Cyclic Universe

Loop quantum gravity introduces strong non-perturbative modifications to the dynamical equations in the semi-classical regime, which are responsible for various novel effects, including resolution of the classical singularity in a Friedman universe. Here we investigate the modifications for the case of a cyclic universe potential, assuming that we can apply the four-dimensional loop quantum formalism within the effective four-dimensional theory of the cyclic scenario. We find that loop quantum effects can dramatically alter the near-collision dynamics of the cyclic scenario. In the kinetic-dominated collapse era, the scalar field is effectively frozen by loop quantum friction, so that the branes approach collision and bounce back without actual collision.Comment: 6 pages, 4 figures; v2: minor changes to match PRD versio

Phenomenology of SUSY with scalar sequestering

The defining feature of scalar sequestering is that the MSSM squark and slepton masses as well as all entries of the scalar Higgs mass matrix vanish at some high scale. This ultraviolet boundary condition - scalar masses vanish while gaugino and Higgsino masses are unsuppressed - is independent of the supersymmetry breaking mediation mechanism. It is the result of renormalization group scaling from approximately conformal strong dynamics in the hidden sector. We review the mechanism of scalar sequestering and prove that the same dynamics which suppresses scalar soft masses and the B_mu term also drives the Higgs soft masses to -|mu|^2. Thus the supersymmetric contribution to the Higgs mass matrix from the mu-term is exactly canceled by the soft masses. Scalar sequestering has two tell-tale predictions for the superpartner spectrum in addition to the usual gaugino mediation predictions: Higgsinos are much heavier (mu > TeV) than scalar Higgses (m_A ~ few hundred GeV), and third generation scalar masses are enhanced because of new positive contributions from Higgs loops.Comment: 16 pages and 3 figure