177 research outputs found
The long delayed solution of the Bukhvostov Lipatov model
In this paper I complete the solution of the Bukhvostov Lipatov model by
computing the physical excitations and their factorized S matrix. I also
explain the paradoxes which led in recent years to the suspicion that the model
may not be integrable.Comment: 9 page
On the Integrability of the Bukhvostov-Lipatov Model
The integrability of the Bukhvostov-Lipatov four-fermion model is
investigated. It is shown that the classical model possesses a current of
Lorentz spin 3, conserved both in the bulk and on the half-line for specific
types of boundary actions. It is then established that the conservation law is
spoiled at the quantum level -- a fact that might indicate that the quantum
Bukhvostov-Lipatov model is not integrable, contrary to what was previously
believed.Comment: 11 pages, 1 figure, LaTeX2e, AMS; new references adde
Generalized sine-Gordon/massive Thirring models and soliton/particle correspondences
We consider a real Lagrangian off-critical submodel describing the soliton
sector of the so-called conformal affine Toda model coupled to
matter fields (CATM). The theory is treated as a constrained system in the
context of Faddeev-Jackiw and the symplectic schemes. We exhibit the parent
Lagrangian nature of the model from which generalizations of the sine-Gordon
(GSG) or the massive Thirring (GMT) models are derivable. The dual description
of the model is further emphasized by providing the relationships between
bilinears of GMT spinors and relevant expressions of the GSG fields. In this
way we exhibit the strong/weak coupling phases and the (generalized)
soliton/particle correspondences of the model. The case is also
outlined.Comment: 22 pages, LaTex, some comments and references added, conclusions
unchanged, to appear in J. Math. Phy
Boundary bound states and boundary bootstrap in the sine-Gordon model with Dirichlet boundary conditions.
We present a complete study of boundary bound states and related boundary
S-matrices for the sine-Gordon model with Dirichlet boundary conditions. Our
approach is based partly on the bootstrap procedure, and partly on the explicit
solution of the inhomogeneous XXZ model with boundary magnetic field and of the
boundary Thirring model. We identify boundary bound states with new ``boundary
strings'' in the Bethe ansatz. The boundary energy is also computed.Comment: 25 pages, harvmac macros Report USC-95-001
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
Tunneling in quantum wires I: Exact solution of the spin isotropic case
We show that the problem of impurity tunneling in a Luttinger liquid of
electrons with spin is solvable in the spin isotropic case (,
arbitrary). The resulting integrable model is similar to a two channel
anisotropic Kondo model, but with the impurity spin in a "cyclic
representation" of the quantum algebra associated with the
anisotropy. Using exact, non-perturbative techniques we study the RG flow, and
compute the DC conductance. As expected from the analysis of Kane and Fisher we
find that the IR fixed point corresponds to two separate leads. We also prove
an exact duality between the UV and IR expansions of the current at vanishing
temperature.Comment: Revtex, epsf, 14pgs, 4 figs. One reference adde
Smart soils track the formation of pH gradients across the rhizosphere
Aims
Our understanding of the rhizosphere is limited by the lack of techniques for in situ live microscopy. Current techniques are either destructive or unsuitable for observing chemical changes within the pore space. To address this limitation, we have developed artificial substrates, termed smart soils, that enable the acquisition and 3D reconstruction of chemical sensors attached to soil particles.
Methods
The transparency of smart soils was achieved using polymer particles with refractive index matching that of water. The surface of the particles was modified both to retain water and act as a local sensor to report on pore space pH via fluorescence emissions. Multispectral signals were acquired from the particles using a light sheet microscope, and machine learning algorithms predicted the changes and spatial distribution in pH at the surface of the smart soil particles.
Results
The technique was able to predict pH live and in situ within ± 0.5 units of the true pH value. pH distribution could be reconstructed across a volume of several cubic centimetres around plant roots at 10 μm resolution. Using smart soils of different composition, we revealed how root exudation and pore structure create variability in chemical properties.
Conclusion
Smart soils captured the pH gradients forming around a growing plant root. Future developments of the technology could include the fine tuning of soil physicochemical properties, the addition of chemical sensors and improved data processing. Hence, this technology could play a critical role in advancing our understanding of complex rhizosphere processes
Fluorinated Copolymers and Terpolymers Based on Vinylidene Fluoride and Bearing Sulfonic Acid Side-Group
International audienceThe radical co- and terpolymerization of perfluoro(4-methyl-3,6-dioxaoct- 7-ene) sulfonyl fluoride (PFSVE) with 1,1-difluoroethylene (or vinylidene fluoride, VDF or VF2), hexafluoropropene (HFP), chlorotrifluoroethylene (CTFE), and bromotrifluoroethylene (BrTFE) is presented. Although PFSVE could not homopolymerize under radical initiation, it could be copolymerized in solution under a radical initiator with VDF, while its copolymerizations with HFP or CTFE led to oligomers in low yields. The terpolymerizations of PFSVE with VDF and HFP, with VDF and CTFE, or with VDF and BrTFE also led to original fluorinated terpolymers bearing sulfonyl fluoride side-groups. The conditions of co- and terpolymerization were optimized in terms of the nature and the amount of the radical initiators, of the nature of solvents (fluorinated or nonhalogenated), and of the initial amounts of fluorinated comonomers. The different mol % contents of comonomers in the co- and terpolymers were assessed by 19F NMR spectroscopy. A wide range of co- and terpolymers containing mol % of PFSVE functional monomer ranging from 10 to 70% was produced. The kinetics of copolymerization of VDF with PFSVE enabled to assess the reactivity ratios of both comonomers: rVDF ¼ 0.57 6 0.15 and rPFSVE ¼ 0.07 6 0.04 at 120 8C. The thermal and physicochemical properties were also studied. Moreover, the glass transition temperatures (Tgs) of poly(VDF-co-PFSVE) copolymers containing different amounts of VDF and PFSVE were determined and the theoretical Tg of poly(PFSVE) homopolymer was deduced. Then, the hydrolysis of the SO2F into SO3H function was investigated and enabled the synthesis of fluorinated copolymers bearing sulfonic acid functions
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