24,708 research outputs found
Arguments for exception in US security discourse
In his influential State of Exception, Giorgio Agamben proposes that, even in apparently liberal western democracies, the state will routinely use the contingency of national emergency to suspend civil liberties and justify expansion of military and police powers. We investigated rhetorical strategies deployed in the web pages of US security agencies, created or reformed in the aftermath of the 9/11 events, to determine whether they present argumentation conforming to Agamben’s model. To expose rhetorical content, we examined strategies operating at two levels within our corpus. Argument schemes and underlying warrants were identified through close examination of systematically selected core documents. Semantic fields establishing themes of threat and danger were also explored, using automatic corpus tools to expose patterns of lexical selection established across the whole corpus. The study recovered evidence of rhetoric broadly consistent with the logic predicted by State of Exception theory, but also presented nuanced findings whose interpretation required careful re-appraisal of core ideas within Agamben’s work
Zero-bias conductance anomaly in bilayer quantum Hall systems
Bilayer quantum Hall system at total filling factor shows a rich
variety of broken symmetry ground states because of the competition between the
interlayer and intralayer Coulomb interactions. When the layers are
sufficiently close, a bilayer system develops spontaneous interlayer
phase-coherence that manifests itself through a spectacular enhancement of the
zero-bias interlayer tunneling conductance. We present a theory of this
tunneling conductance anomaly, and show that the zero-bias conductance is
proportional to the square of the {\it quasiparticle} tunneling amplitude.Comment: 3 pages, 1 figure. To appear in the PPHMF-IV conference proceedings.
(For more details, see cond-mat/0103454) New version contains two added
reference
Roughness effects in turbulent forced convection
We conducted direct numerical simulations (DNSs) of turbulent flow over
three-dimensional sinusoidal roughness in a channel. A passive scalar is
present in the flow with Prandtl number , to study heat transfer by
forced convection over this rough surface. The minimal channel is used to
circumvent the high cost of simulating high Reynolds number flows, which
enables a range of rough surfaces to be efficiently simulated. The near-wall
temperature profile in the minimal channel agrees well with that of the
conventional full-span channel, indicating it can be readily used for
heat-transfer studies at a much reduced cost compared to conventional DNS. As
the roughness Reynolds number, , is increased, the Hama roughness
function, , increases in the transitionally rough regime before
tending towards the fully rough asymptote of , where
is a constant that depends on the particular roughness geometry and
is the von K\'arm\'an constant. In this fully rough
regime, the skin-friction coefficient is constant with bulk Reynolds number,
. Meanwhile, the temperature difference between smooth- and rough-wall
flows, , appears to tend towards a constant value,
. This corresponds to the Stanton number (the temperature
analogue of the skin-friction coefficient) monotonically decreasing with
in the fully rough regime. Using shifted logarithmic velocity and temperature
profiles, the heat transfer law as described by the Stanton number in the fully
rough regime can be derived once both the equivalent sand-grain roughness
and the temperature difference are known. In
meteorology, this corresponds to the ratio of momentum and heat transfer
roughness lengths, , being linearly proportional to ,
the momentum roughness length [continued]...Comment: Accepted (In press) in the Journal of Fluid Mechanic
On the equivalence between standard and sequentially ordered hidden Markov models
Chopin (2007) introduced a sequentially ordered hidden Markov model, for
which states are ordered according to their order of appearance, and claimed
that such a model is a re-parametrisation of a standard Markov model. This note
gives a formal proof that this equivalence holds in Bayesian terms, as both
formulations generate equivalent posterior distributions, but does not hold in
Frequentist terms, as both formulations generate incompatible likelihood
functions. Perhaps surprisingly, this shows that Bayesian re-parametrisation
and Frequentist re-parametrisation are not identical concepts
Order parameter suppression in double layer quantum Hall ferromagnets
Double-layer quantum Hall systems at Landau level filling factor have
a broken symmetry ground state with spontaneous interlayer phase coherence and
a gap between symmetric and antisymmetric subbands in the absence of interlayer
tunneling. We examine the influence of quantum fluctuations on the spectral
function of the symmetric Green's function, probed in optical absorption
experiments (cond-mat/9809373). We find that as the maximum layer separation at
which the quantum Hall effect occurs is approached, absorption in the
lowest Landau level grows in strength. Detailed line shapes for this absorption
are evaluated and related to features in the system's collective excitation
spectrum.Comment: 7 pages, 4 figures, To appear in Proceedings of 13th International
Conference on Electronic Properties of Two-Dimensional Systems (EP2DS-13
Tunneling current characteristics in bilayer quantum Hall systems
Weakly disordered bilayer quantum Hall systems at filling factor show
spontaneous interlayer phase coherence if the layers are sufficiently close
together. We study the collective modes in the system, the current-voltage
characteristics and their evolution with an in-plane magnetic field in the
phase-coherent regime.Comment: 4 pages, 2 figures, grammatical changes, To appear in SCES 2001
proceeding
Vortex Lattice Structure of Fulde-Ferrell-Larkin-Ovchinnikov Superconductors
In superconductors with singlet pairing, the inhomogeneous
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is expected to be stabilized by a
large Zeeman splitting. We develop an efficient method to evaluate the
Landau-Ginzburg free energies of FFLO-state vortex lattices and use it to
simplify the considerations that determine the optimal vortex configuration at
different points in the phasediagram. We demonstrate that the order parameter
spatial profile is completely determined, up to a uniform translation, by its
Landau level index n and the vortex Lattice structure and derive an explicit
expression for the order parameter spatial profile that can be used to
determine n from experimental data.Comment: 6 pages with one embedded color figure. Minor changes. Final version
as publishe
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