815 research outputs found
Universal scaling behavior of the single electron box in the strong tunneling limit
We perform a numerical analysis of recently proposed scaling functions for
the single electron box. Specifically, we study the ``magnetic'' susceptibility
as a function of tunneling conductance and gate charge, and the effective
charging energy at zero gate charge as a function of tunneling conductance in
the strong tunneling limit. Our Monte Carlo results confirm the accuracy of the
theoretical predictions.Comment: Published versio
Transport of interacting electrons through a potential barrier: nonperturbative RG approach
We calculate the linear response conductance of electrons in a Luttinger
liquid with arbitrary interaction g_2, and subject to a potential barrier of
arbitrary strength, as a function of temperature. We first map the Hamiltonian
in the basis of scattering states into an effective low energy Hamiltonian in
current algebra form. Analyzing the perturbation theory in the fermionic
representation the diagrams contributing to the renormalization group (RG)
\beta-function are identified. A universal part of the \beta-function is given
by a ladder series and summed to all orders in g_2. First non-universal
corrections beyond the ladder series are discussed. The RG-equation for the
temperature dependent conductance is solved analytically. Our result agrees
with known limiting cases.Comment: 6 pages, 5 figure
An Equation of State of a Carbon-Fibre Epoxy Composite under Shock Loading
An anisotropic equation of state (EOS) is proposed for the accurate
extrapolation of high-pressure shock Hugoniot (anisotropic and isotropic)
states to other thermodynamic (anisotropic and isotropic) states for a shocked
carbon-fibre epoxy composite (CFC) of any symmetry. The proposed EOS, using a
generalised decomposition of a stress tensor [Int. J. Plasticity \textbf{24},
140 (2008)], represents a mathematical and physical generalisation of the
Mie-Gr\"{u}neisen EOS for isotropic material and reduces to this equation in
the limit of isotropy. Although a linear relation between the generalised
anisotropic bulk shock velocity and particle velocity was
adequate in the through-thickness orientation, damage softening process
produces discontinuities both in value and slope in the -
relation. Therefore, the two-wave structure (non-linear anisotropic and
isotropic elastic waves) that accompanies damage softening process was proposed
for describing CFC behaviour under shock loading. The linear relationship
- over the range of measurements corresponding to non-linear
anisotropic elastic wave shows a value of (the intercept of the
- curve) that is in the range between first and second
generalised anisotropic bulk speed of sound [Eur. Phys. J. B \textbf{64}, 159
(2008)]. An analytical calculation showed that Hugoniot Stress Levels (HELs) in
different directions for a CFC composite subject to the two-wave structure
(non-linear anisotropic elastic and isotropic elastic waves) agree with
experimental measurements at low and at high shock intensities. The results are
presented, discussed and future studies are outlined.Comment: 12 pages, 9 figure
Interference in presence of Dissipation
We study a particle on a ring in presence of various dissipative
environments. We develop and solve a variational scheme assuming low frequency
dominance. We analyze our solution within a renormalization group (RG) scheme
to all orders which reproduces a 2 loop RG for the Caldeira-Legget environment.
In the latter case the Aharonov-Bohm (AB) oscillation amplitude is exponential
in -R^2 where R is the ring's radius. For either a charge or an electric dipole
coupled to a dirty metal we find that the metal induces dissipation, however
the AB amplitude is ~ R^{-2} for large R, as for free particles. Cold atoms
with a large electric dipole may show a crossover between these two behaviors.Comment: 5 pages, added motivations and reference
Explicit Construction of Spin 4 Casimir Operator in the Coset Model
We generalize the Goddard-Kent-Olive (GKO) coset construction to the
dimension 5/2 operator for and compute the fourth order
Casimir invariant in the coset model with the generic unitary minimal
series that can be viewed as perturbations of the
limit, which has been investigated previously in the realization of
free fermion model.Comment: 11 page
Poisson structures on the center of the elliptic algebra A_{p,q}(sl(2)_c)
It is shown that the elliptic algebra A_{p,q}(sl(2)_c) has a non trivial
center at the critical level , generalizing the result of Reshetikhin and
Semenov-Tian-Shansky for trigonometric algebras. A family of Poisson structures
indexed by a non-negative integer is constructed on this center.Comment: LaTeX 2.09 Document (should be run twice
Particle-Field Duality and Form Factors from Vertex Operators
Using a duality between the space of particles and the space of fields, we
show how one can compute form factors directly in the space of fields. This
introduces the notion of vertex operators, and form factors are vacuum
expectation values of such vertex operators in the space of fields. The vertex
operators can be constructed explicitly in radial quantization. Furthermore,
these vertex operators can be exactly bosonized in momentum space. We develop
these ideas by studying the free-fermion point of the sine-Gordon theory, and
use this scheme to compute some form-factors of some non-free fields in the
sine-Gordon theory. This work further clarifies earlier work of one of the
authors, and extends it to include the periodic sector.Comment: 17 pages, 2 figures, CLNS 93/??
Boundary contributions to specific heat and susceptibility in the spin-1/2 XXZ chain
Exact low-temperature asymptotic behavior of boundary contribution to
specific heat and susceptibility in the one-dimensional spin-1/2 XXZ model with
exchange anisotropy 1/2 < \Delta \le 1 is analytically obtained using the
Abelian bosonization method. The boundary spin susceptibility is divergent in
the low-temperature limit. This singular behavior is caused by the first-order
contribution of a bulk leading irrelevant operator to boundary free energy. The
result is confirmed by numerical simulations of finite-size systems. The
anomalous boundary contributions in the spin isotropic case are universal.Comment: 6 pages, 3 figures; corrected typo
Color transitions in coral's fluorescent proteins by site-directed mutagenesis
BACKGROUND: Green Fluorescent Protein (GFP) cloned from jellyfish Aequorea victoria and its homologs from corals Anthozoa have a great practical significance as in vivo markers of gene expression. Also, they are an interesting puzzle of protein science due to an unusual mechanism of chromophore formation and diversity of fluorescent colors. Fluorescent proteins can be subdivided into cyan (~ 485 nm), green (~ 505 nm), yellow (~ 540 nm), and red (>580 nm) emitters. RESULTS: Here we applied site-directed mutagenesis in order to investigate the structural background of color variety and possibility of shifting between different types of fluorescence. First, a blue-shifted mutant of cyan amFP486 was generated. Second, it was established that cyan and green emitters can be modified so as to produce an intermediate spectrum of fluorescence. Third, the relationship between green and yellow fluorescence was inspected on closely homologous green zFP506 and yellow zFP538 proteins. The following transitions of colors were performed: yellow to green; yellow to dual color (green and yellow); and green to yellow. Fourth, we generated a mutant of cyan emitter dsFP483 that demonstrated dual color (cyan and red) fluorescence. CONCLUSIONS: Several amino acid substitutions were found to strongly affect fluorescence maxima. Some positions primarily found by sequence comparison were proved to be crucial for fluorescence of particular color. These results are the first step towards predicting the color of natural GFP-like proteins corresponding to newly identified cDNAs from corals
One-point functions in integrable quantum field theory at finite temperature
We determine the form factor expansion of the one-point functions in
integrable quantum field theory at finite temperature and find that it is
simpler than previously conjectured. We show that no singularities are left in
the final expression provided that the operator is local with respect to the
particles and argue that the divergences arising in the non-local case are
related to the absence of spontaneous symmetry breaking on the cylinder. As a
specific application, we give the first terms of the low temperature expansion
of the one-point functions for the Ising model in a magnetic field.Comment: 10 pages, late
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