1,253 research outputs found
Exact Friedel oscillations in the g=1/2 Luttinger liquid
A single impurity in the 1D Luttinger model creates a local modification of
the charge density analogous to the Friedel oscillations. In this paper, we
present an exact solution of the case (the equivalent of the
Toulouse point) at any temperature and impurity coupling, expressing the
charge density in terms of a hypergeometric function. We find in particular
that at , the oscillatory part of the density goes as at small
distance and at large distance.Comment: 1 reference added. 13 pages, harvma
Haldane Gapped Spin Chains: Exact Low Temperature Expansions of Correlation Functions
We study both the static and dynamic properties of gapped, one-dimensional,
Heisenberg, anti-ferromagnetic, spin chains at finite temperature through an
analysis of the O(3) non-linear sigma model. Exploiting the integrability of
this theory, we are able to compute an exact low temperature expansion of the
finite temperature correlators. We do so using a truncated `form-factor'
expansion and so provide evidence that this technique can be successfully
extended to finite temperature. As a direct test, we compute the static
zero-field susceptibility and obtain an exact match to the susceptibility
derived from the low temperature expansion of the exact free energy. We also
study transport properties, computing both the spin conductance and the
NMR-relaxation rate, 1/T_1. We find these quantities to show ballistic
behaviour. In particular, the computed spin conductance exhibits a non-zero
Drude weight at finite temperature and zero applied field. The physics thus
described differs from the spin diffusion reported by Takigawa et al. from
experiments on the Haldane gap material, AgVP_2S_6.Comment: 51 pages, 5 figure
Non-equilibrium DC noise in a Luttinger liquid with impurity
We compute exactly the non-equilibrium DC noise in a Luttinger liquid with an
impurity and an applied voltage. By generalizing Landauer transport theory for
Fermi liquids to interacting, integrable systems, we relate this noise to the
density fluctuations of quasiparticles. We then show how to compute these
fluctuations using the Bethe ansatz. The non-trivial density correlations from
the interactions result in a substantial part of the non-equilibrium noise. The
final result for the noise is a scaling function of the voltage, temperature
and impurity coupling. It may eventually be observable in tunneling between
edges of a fractional quantum Hall effect device.Comment: 10 pages with one figure, uses revtex and eps
Integrable supersymmetric correlated electron chain with open boundaries
We construct an extended Hubbard model with open boundaries from a -matrix
based on the superalgebra. We study the reflection equation and
find two classes of diagonal solutions. The corresponding one-dimensional open
Hamiltonians are diagonalized by means of the Bethe ansatz approach.Comment: latex, 14 page
Life cycle assessment of Polychlorinated Biphenyl contaminated soil remediation processes
Goal and scope. A life-cycle assessment (LCA) was performed to evaluate the environmental impacts of the remediation of industrial soils contaminated by polychlorobiphenyl (PCB). Two new bioremediation treatment options were compared with the usual incineration process. In this attributional LCA, only secondary impacts were considered. The contaminated soil used for the experiments contained 200 mg of PCB per kg. Methods. Three off-site treatments scenarios were studied: 1) bioremediation with mechanical aeration, 2) bioremediation with electric aeration and 3) incineration with natural gas. Bioremediation processes were designed from lab-scale, scale-up and pilot experiments. The incineration technique was inspired by a French plant. A semi-quantitative uncertainty analysis was performed on the data. Environmental impacts were evaluated with the CML 2001 method using the Simapro software program. Results and discussion. In most compared categories, the bioremediation processes are favorable. Of the bioremediation options, the lowest environmental footprint was observed for electric aeration. The uncertainty analysis supported the results that compared incineration and bioremediation but decreased the difference between the options of aeration. The distance of transportation was one of the most sensitive parameters, especially for bioremediation. At equal distances between the polluted sites and the treatment plant, bioremediation had fewer impacts than incineration in eight out of thirteen categories. Conclusions. The use of natural gas for the incineration process generated the most impacts. Irrespective of the aeration option, bioremediation was better than incineration. Recommendations. The time of treatment should be taken into account. More precise and detailed data are required for the incineration scenario. More parameters of biological treatments should be measured. LCA results should be completed using ecological and health risk assessment and an acceptability evaluation
Low-temperature behavior of a Magnetic Impurity in a Heisenberg Chain
Using the bosonization technique, we have studied a spin-1/2 magnetic
impurity in Heisenberg chain, and shown that the impurity specific heat and
spin susceptibility have an anomalous temperature dependence.Comment: 12 pages, Revtex, no figure, to be published in Phys. Rev. Let
The selectivity, voltage-dependence and acid sensitivity of the tandem pore potassium channel TASK-1 : contributions of the pore domains
We have investigated the contribution to ionic
selectivity of residues in the selectivity filter and pore
helices of the P1 and P2 domains in the acid sensitive
potassium channel TASK-1. We used site directed mutagenesis
and electrophysiological studies, assisted by structural
models built through computational methods. We have
measured selectivity in channels expressed in Xenopus
oocytes, using voltage clamp to measure shifts in reversal
potential and current amplitudes when Rb+ or Na+ replaced
extracellular K+. Both P1 and P2 contribute to selectivity,
and most mutations, including mutation of residues in the
triplets GYG and GFG in P1 and P2, made channels nonselective.
We interpret the effects of these—and of other
mutations—in terms of the way the pore is likely to be
stabilised structurally. We show also that residues in the
outer pore mouth contribute to selectivity in TASK-1.
Mutations resulting in loss of selectivity (e.g. I94S, G95A)
were associated with slowing of the response of channels to
depolarisation. More important physiologically, pH sensitivity
is also lost or altered by such mutations. Mutations
that retained selectivity (e.g. I94L, I94V) also retained their
response to acidification. It is likely that responses both to
voltage and pH changes involve gating at the selectivity filter
Applications of quantum integrable systems
We present two applications of quantum integrable systems. First, we predict
that it is possible to generate high harmonics from solid state devices by
demostrating that the emission spectrum for a minimally coupled laser field of
frequency to an impurity system of a quantum wire, contains multiples
of the incoming frequency. Second, evaluating expressions for the conductance
in the high temperature regime we show that the caracteristic filling fractions
of the Jain sequence, which occur in the fractional quantum Hall effect, can be
obtained from quantum wires which are described by minimal affine Toda field
theories.Comment: 25 pages of LaTex, 4 figures, based on talk at the 6-th international
workshop on conformal field theories and integrable models, (Chernogolovka,
September 2002
Quasi-particles in Fractional Quantum Hall Effect Edge Theories
We propose a quasi-particle formulation of effective edge theories for the
fractional quantum Hall effect. For the edge of a Laughlin state with filling
fraction \nu=1/m, our fundamental quasi-particles are edge electrons of charge
-e and edge quasi-holes of charge +e/m. These quasi-particles satisfy exclusion
statistics in the sense of Haldane. We exploit algebraic properties of edge
electrons to derive a kinetic equation for charge transport between a \nu=1/m
fractional quantum Hall edge and a normal metal. We also analyze alternative
`Boltzmann' equations that are directly based on the exclusion statistics
properties of edge quasi-particles. Generalizations to more general filling
fractions (Jain series) are briefly discussed.Comment: 20 pages, 2 eps figures, revtex, references updated, Phys. Rev. B in
pres
A unified framework for the Kondo problem and for an impurity in a Luttinger liquid
We develop a unified theoretical framework for the anisotropic Kondo model
and the boundary sine-Gordon model. They are both boundary integrable quantum
field theories with a quantum-group spin at the boundary which takes values,
respectively, in standard or cyclic representations of the quantum group
. This unification is powerful, and allows us to find new results for
both models. For the anisotropic Kondo problem, we find exact expressions (in
the presence of a magnetic field) for all the coefficients in the
``Anderson-Yuval'' perturbative expansion. Our expressions hold initially in
the very anisotropic regime, but we show how to continue them beyond the
Toulouse point all the way to the isotropic point using an analog of
dimensional regularization. For the boundary sine-Gordon model, which describes
an impurity in a Luttinger liquid, we find the non-equilibrium conductance for
all values of the Luttinger coupling.Comment: 36 pages (22 in double-page format), 7 figures in uuencoded file,
uses harvmac and epsf macro
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