23,460 research outputs found
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
scattering. E.g. for scattering we show that for c.m. energy
, where .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 which is one-fourth of the
corresponding upper bound on , and Wu, Martin,Roy and Singh
improved the bound by adding the constraint of a given . 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
scattering, defining ,we show that for c.m. energy ,
where . This bound is
asymptotically one-fourth of the corresponding Martin-Roy bound on the total
cross section, and the scale factor is one-fourth of the scale factor in
the total cross section bound. The average over the interval (s,2s) of the
inelastic cross section has a bound of the same form with
replaced by .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
different complete commuting sets of observables (e.g. , and
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
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