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 $\nu=1$ 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 $Pr=0.7$, 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, $k^+$, is increased, the Hama roughness function, $\Delta U^+$, increases in the transitionally rough regime before tending towards the fully rough asymptote of $\kappa_m^{-1}\log(k^+)+C$, where $C$ is a constant that depends on the particular roughness geometry and $\kappa_m\approx0.4$ is the von K\'arm\'an constant. In this fully rough regime, the skin-friction coefficient is constant with bulk Reynolds number, $Re_b$. Meanwhile, the temperature difference between smooth- and rough-wall flows, $\Delta\Theta^+$, appears to tend towards a constant value, $\Delta\Theta^+_{FR}$. This corresponds to the Stanton number (the temperature analogue of the skin-friction coefficient) monotonically decreasing with $Re_b$ 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 $k_s/k$ and the temperature difference $\Delta \Theta^+_{FR}$ are known. In meteorology, this corresponds to the ratio of momentum and heat transfer roughness lengths, $z_{0m}/z_{0h}$, being linearly proportional to $z_{0m}^+$, 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 $\nu=1$ 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 $\nu=1$ 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 $\nu=1$ 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