3,304 research outputs found
Sputtered gold mask for deep chemical etching of silicon
Sputtered mask resists chemical attack from acid and has adherence to withstand prolonged submergence in etch solution without lifting from silicon surface. Even under prolonged etch conditions with significant undercutting, gold mask maintained excellent adhesion to silicon surface and imperviousness to acid
‘In shape and mind transformed’? Televised teaching and learning Shakespeare
Reality television offers the BBC the opportunity to fulfil its dual imperatives of education and entertainment, frequently constructed as anathematic. This article considers three recent examples of televised teaching and learning Shakespeare: When Romeo Met Juliet, Macbeth, the movie star and me, and Off By Heart: Shakespeare. It demonstrates the programmes’ fit with the reality genre through their common ingredients of authenticity, contained locations, hybridity, experts, fallible and flawed participants, articulation and reconciliation of social difference. Moreover, all three share an emphasis on a reality television staple: transformation, in terms of the participants’ knowledge, skills and personal growth, but also in relation to television audiences and the British education system. The programmes might thus usefully be understood as part of a reality television subgenre, evolving in Britain since the late 1970s, of Shmake-over. This article is published as part of a collection to commemorate the 400th anniversary of William Shakespeare’s death
Effects of a fundamental mass term in two-dimensional super Yang-Mills theory
We show that adding a vacuum expectation value to a gauge field left over
from a dimensional reduction of three-dimensional pure supersymmetric
Yang-Mills theory generates mass terms for the fundamental fields in the
two-dimensional theory while supersymmetry stays intact. This is similar to the
adjoint mass term that is generated by a Chern-Simons term in this theory. We
study the spectrum of the two-dimensional theory as a function of the vacuum
expectation value and of the Chern-Simons coupling. Apart from some symmetry
issues a straightforward picture arises. We show that at least one massless
state exists if the Chern-Simons coupling vanishes. The numerical spectrum
separates into (almost) massless and very heavy states as the Chern-Simons
coupling grows. We present evidence that the gap survives the continuum limit.
We display structure functions and other properties of some of the bound
states.Comment: 17 pp., 10 figs; substantially revised version to be published in
Phys. Rev.
Dual Projection and Selfduality in Three Dimensions
We discuss the notion of duality and selfduality in the context of the dual
projection operation that creates an internal space of potentials. Contrary to
the prevailing algebraic or group theoretical methods, this technique is
applicable to both even and odd dimensions. The role of parity in the kernel of
the Gauss law to determine the dimensional dependence is clarified. We derive
the appropriate invariant actions, discuss the symmetry groups and their proper
generators. In particular, the novel concept of duality symmetry and
selfduality in Maxwell theory in (2+1) dimensions is analysed in details. The
corresponding action is a 3D version of the familiar duality symmetric
electromagnetic theory in 4D. Finally, the duality symmetric actions in the
different dimensions constructed here manifest both the SO(2) and
symmetries, contrary to conventional results.Comment: 20 pages, late
Integral group actions on symmetric spaces and discrete duality symmetries of supergravity theories
For a split, simply connected, semisimple Lie group of rank
and the maximal compact subgroup of , we give a method for computing
Iwasawa coordinates of using the Chevalley generators and the Steinberg
presentation. When is a scalar coset for a supergravity theory in
dimensions , we determine the action of the integral form
on . We give explicit results for the action of the
discrete --duality groups and on the
scalar cosets and
for type IIB supergravity
in ten dimensions and 11--dimensional supergravity in dimensions,
respectively. For the former, we use this to determine the discrete U--duality
transformations on the scalar sector in the Borel gauge and we describe the
discrete symmetries of the dyonic charge lattice. We determine the
spectrum--generating symmetry group for fundamental BPS solitons of type IIB
supergravity in dimensions at the classical level and we propose an
analog of this symmetry at the quantum level. We indicate how our methods can
be used to study the orbits of discrete U--duality groups in general
Frequentist Analysis of the Parameter Space of Minimal Supergravity
We make a frequentist analysis of the parameter space of minimal supergravity
(mSUGRA), in which, as well as the gaugino and scalar soft
supersymmetry-breaking parameters being universal, there is a specific relation
between the trilinear, bilinear and scalar supersymmetry-breaking parameters,
A_0 = B_0 + m_0, and the gravitino mass is fixed by m_{3/2} = m_0. We also
consider a more general model, in which the gravitino mass constraint is
relaxed (the VCMSSM). We combine in the global likelihood function the
experimental constraints from low-energy electroweak precision data, the
anomalous magnetic moment of the muon, the lightest Higgs boson mass M_h, B
physics and the astrophysical cold dark matter density, assuming that the
lightest supersymmetric particle (LSP) is a neutralino. In the VCMSSM, we find
a preference for values of m_{1/2} and m_0 similar to those found previously in
frequentist analyses of the constrained MSSM (CMSSM) and a model with common
non-universal Higgs masses (NUHM1). On the other hand, in mSUGRA we find two
preferred regions: one with larger values of both m_{1/2} and m_0 than in the
VCMSSM, and one with large m_0 but small m_{1/2}. We compare the probabilities
of the frequentist fits in mSUGRA, the VCMSSM, the CMSSM and the NUHM1: the
probability that mSUGRA is consistent with the present data is significantly
less than in the other models. We also discuss the mSUGRA and VCMSSM
predictions for sparticle masses and other observables, identifying potential
signatures at the LHC and elsewhere.Comment: 18 pages 27 figure
Accurate Neutralino Relic Density Computations in Supergravity Models
We investigate the question of the proper thermal averaging of neutralino
annihilation amplitudes which possess poles and thresholds, as they impact on
the calculated neutralino relic density and therefore on the cosmological
viability of supersymmetric models. We focus on two typical resonances, namely
the boson and the lightest Higgs boson (). In the context of
supergravity models with radiative electroweak symmetry breaking, an
exploration of the whole parameter space of the model is possible and the
overall relevance of these sophisticated analyses can be ascertained. As an
example we chose the minimal supergravity model since the presence of
such poles is essential to obtain a cosmologically acceptable model. We find
that the proper thermal averaging is important for individual points in
parameter space and that the fraction of cosmologically acceptable points is
increased somewhat by the accurate procedure. However, qualitatively the new
set of points is very similar to that obtained previously using the usual
series approximations to the thermal average. We conclude that all
phenomenological analyses based on the previously determined cosmologically
allowed set remain valid.Comment: 15 pages, 9 figures (available upon request as uuencoded file or
separate ps files), tex (harvmac) CTP-TAMU-14/9
Sharpening the predictions of big-bang nucleosynthesis
Motivated by the recent measurement of the primeval abundance of deuterium,
we re-examine the nuclear inputs to big-bang nucleosynthesis (BBN). Using
Monte-Carlo realization of the nuclear cross-section data to directly estimate
the theoretical uncertainties for the yields of D, 3-He and 7-Li, we show that
previous estimates were a factor of 2 too large. We sharpen the BBN
determination of the baryon density based upon deuterium, rho_B = (3.6 +/- 0.4)
* 10^{-31} g/cm^3 (Omega_B h^2 = 0.019 +/- 0.0024), which leads to a predicted
4-He abundance, Y_P = 0.246 +/- 0.0014 and a stringent limit to the equivalent
number of light neutrino species: N_nu < 3.20 (all at 95% cl). The predicted
7-Li abundance, 7-Li/H = (3.5 + 1.1 - 0.9) * 10^{-10}, is higher than that
observed in pop II stars, (1.7 +/- 0.3) * 10^{-10} (both, 95% cl). We identify
key reactions and the energies where further work is needed.Comment: 5 pages, 4 figures (epsfig), REVTeX; submitted to Phys. Rev. Let
Detailed study of BBN implications of neutrino oscillation generated neutrino asymmetries in some four neutrino models
We re-examine the evolution of neutrino asymmetries in several four neutrino
models. The first case involves the direct creation of by oscillations. In the second case, we consider the mass
hierarchy where oscillations generate a large and some of
this asymmetry is converted into by oscillations. We estimate the implications for BBN for a range of
cosmologically interesting values. The present paper improves on
previous published work by taking into account the finite repopulation rate and
the time dependence of the distortions to the neutrino momentum distributions.
The treatment of chemical decoupling is also improved.Comment: Expanded discussion on the sign of the neutrino asymmetr
- …