12,196 research outputs found
Geometric Exponents of Dilute Logarithmic Minimal Models
The fractal dimensions of the hull, the external perimeter and of the red
bonds are measured through Monte Carlo simulations for dilute minimal models,
and compared with predictions from conformal field theory and SLE methods. The
dilute models used are those first introduced by Nienhuis. Their loop fugacity
is beta = -2cos(pi/barkappa}) where the parameter barkappa is linked to their
description through conformal loop ensembles. It is also linked to conformal
field theories through their central charges c = 13 - 6(barkappa +
barkappa^{-1}) and, for the minimal models of interest here, barkappa = p/p'
where p and p' are two coprime integers. The geometric exponents of the hull
and external perimeter are studied for the pairs (p,p') = (1,1), (2,3), (3,4),
(4,5), (5,6), (5,7), and that of the red bonds for (p,p') = (3,4). Monte Carlo
upgrades are proposed for these models as well as several techniques to improve
their speeds. The measured fractal dimensions are obtained by extrapolation on
the lattice size H,V -> infinity. The extrapolating curves have large slopes;
despite these, the measured dimensions coincide with theoretical predictions up
to three or four digits. In some cases, the theoretical values lie slightly
outside the confidence intervals; explanations of these small discrepancies are
proposed.Comment: 41 pages, 32 figures, added reference
Ground State and Tkachenko Modes of a Rapidly Rotating Bose-Einstein Condensate in the Lowest Landau Level State
The Letter considers the ground state and the Tkachenko modes for a rapidly
rotating Bose-Einstein condensate (BEC), when its macroscopic wave function is
a coherent superposition of states analogous to the lowest Landau levels of a
charge in a magnetic field. As well as in type II superconductors close to the
critical magnetic field , this corresponds to a periodic vortex
lattice. The exact value of the shear elastic modulus of the vortex lattice,
which was known from the old works on type II superconductors, essentially
exceeds the values calculated recently for BEC. This is important for
comparison with observation of the Tkachenko mode in the rapidly rotating BEC.Comment: 5 pages, 1 figure; discussion edited, references added, numerical
factors and typos correcte
Single File Diffusion enhancement in a fluctuating modulated 1D channel
We show that the diffusion of a single file of particles moving in a
fluctuating modulated 1D channel is enhanced with respect to the one in a bald
pipe. This effect, induced by the fluctuations of the modulation, is favored by
the incommensurability between the channel potential modulation and the moving
file periodicity. This phenomenon could be of importance in order to optimize
the critical current in superconductors, in particular in the case where mobile
vortices move in 1D channels designed by adapted patterns of pinning sites.Comment: 4 pages, 4 figure
Biochemical characterization of proopiomelanocortin variants in human and owls
In humans the proopiomelanocortin (POMC) gene is located on the short arm of the chromosome 2 at the 23.3 position and encodes a 39kDa peptide with 241 amino acids. This peptide is the precursor of the proopiomelanocortin prohormone and it is produced in both the anterior and posterior lobes of the pituitary, as well as the arcuate nucleus of the hypothalamus.
Maturation of POMC involves glycosylation, acetylation, and selective, sequential and tissue specific processing events mediated by proprotein convertases PC-1/3 and PC-2. Proteolytic cleavage of POMC at 9 different locations produces a variety of hormones, including adrenocorticotrophin (ACTH), α-, β- and γ-melanocyte-stimulating hormones (α-MSH, β-MSH, γ-MSH), corticotrophin-like intermediate peptide (CLIP), β-lipotropin (β-LPH), and β-endorphin (Fig. 1.)
Single File Diffusion of particles with long ranged interactions: damping and finite size effects
We study the Single File Diffusion (SFD) of a cyclic chain of particles that
cannot cross each other, in a thermal bath, with long ranged interactions, and
arbitrary damping. We present simulations that exhibit new behaviors
specifically associated to systems of small number of particles and to small
damping. In order to understand those results, we present an original analysis
based on the decomposition of the particles motion in the normal modes of the
chain. Our model explains all dynamic regimes observed in our simulations, and
provides convincing estimates of the crossover times between those regimes.Comment: 30 pages, 9 figure
Interaction of multiple particles with a solidification front : from compacted particle layer to particle trapping
The interaction of solidification fronts with objects such as particles,
droplets, cells, or bubbles is a phenomenon with many natural and technological
occurrences. For an object facing the front, it may yield various fates, from
trapping to rejection, with large implications regarding the solidification
pattern. However, whereas most situations involve multiple particles
interacting with each other and the front, attention has focused almost
exclusively on the interaction of a single, isolated object with the front.
Here we address experimentally the interaction of multiple particles with a
solidification front by performing solidification experiments of a monodisperse
particle suspension in a Hele-Shaw cell, with precise control of growth
conditions and real-time visualization. We evidence the growth of a particle
layer ahead of the front at a close-packing volume fraction and we document its
steady state value at various solidification velocities. We then extend single
particle models to the situation of multiple particles by taking into account
the additional force induced on an entering particle by viscous friction in the
compacted particle layer. By a force balance model, this provides an indirect
measure of the repelling mean thermomolecular pressure over a particle entering
the front. The presence of multiple particles is found to increase it following
a reduction of the thickness of the thin liquid film that separates particles
and front. We anticipate the findings reported here to provide a relevant basis
to understand many complex solidification situations in geophysics,
engineering, biology, or food engineering, where multiple objects interact with
the front and control the resulting solidification patterns.Comment: 13 pages, 10 figures, submitted to Langmui
FFLO states and quantum oscillations in mesoscopic superconductors and superfluid ultracold Fermi gases
We have studied the distinctive features of the
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) instability and phase transitions in
two--dimensional (2D) mesoscopic superconductors placed in magnetic field of
arbitrary orientation and rotating superfluid Fermi gases with imbalanced state
populations. Using a generalized version of the phenomenological
Ginzburg-Landau theory we have shown that the FFLO states are strongly modified
by the effect of the trapping potential confining the condensate. The
phenomenon of the inhomogeneous state formation is determined by the interplay
of three length scales: (i) length scale of the FFLO instability; (ii) 2D
system size; (iii) length scale associated with the orbital effect caused
either by the Fermi condensate rotation or magnetic field component applied
perpendicular to the superconducting disc. We have studied this interplay and
resulting quantum oscillation effects in both superconducting and superfluid
finite -- size systems with FFLO instability and described the hallmarks of the
FFLO phenomenon in a restricted geometry. The finite size of the system is
shown to affect strongly the conditions of the observability of switching
between the states with different vorticities.Comment: 11 pages, 5 figures, Submitted to PR
A homomorphism between link and XXZ modules over the periodic Temperley-Lieb algebra
We study finite loop models on a lattice wrapped around a cylinder. A section
of the cylinder has N sites. We use a family of link modules over the periodic
Temperley-Lieb algebra EPTL_N(\beta, \alpha) introduced by Martin and Saleur,
and Graham and Lehrer. These are labeled by the numbers of sites N and of
defects d, and extend the standard modules of the original Temperley-Lieb
algebra. Beside the defining parameters \beta=u^2+u^{-2} with u=e^{i\lambda/2}
(weight of contractible loops) and \alpha (weight of non-contractible loops),
this family also depends on a twist parameter v that keeps track of how the
defects wind around the cylinder. The transfer matrix T_N(\lambda, \nu) depends
on the anisotropy \nu and the spectral parameter \lambda that fixes the model.
(The thermodynamic limit of T_N is believed to describe a conformal field
theory of central charge c=1-6\lambda^2/(\pi(\lambda-\pi)).)
The family of periodic XXZ Hamiltonians is extended to depend on this new
parameter v and the relationship between this family and the loop models is
established. The Gram determinant for the natural bilinear form on these link
modules is shown to factorize in terms of an intertwiner i_N^d between these
link representations and the eigenspaces of S^z of the XXZ models. This map is
shown to be an isomorphism for generic values of u and v and the critical
curves in the plane of these parameters for which i_N^d fails to be an
isomorphism are given.Comment: Replacement of "The Gram matrix as a connection between periodic loop
models and XXZ Hamiltonians", 31 page
Amorphous ferromagnetism and re-entrant magnetic glassiness in SmMoO: new insights into the electronic phase diagram of pyrochlore molybdates
We discuss the magnetic properties of a SmMoO single
crystal as investigated by means of different experimental techniques. In the
literature, a conventional itinerant ferromagnetic state is reported for the
Mo sublattice below K. However, our results of dc
magnetometry, muon spin spectroscopy (SR) and high-harmonics magnetic
ac susceptibility unambiguously evidence highly disordered conditions in this
phase, in spite of the crystalline and chemical order. This disordered magnetic
state shares several common features with amorphous ferromagnetic alloys. This
scenario for SmMoO is supported by the anomalously high
values of the critical exponents, as mainly deduced by a scaling analysis of
our dc magnetization data and confirmed by the other techniques. Moreover,
SR detects a significant static magnetic disorder at the microscopic
scale. At the same time, the critical divergence of the third-harmonic
component of the ac magnetic susceptibility around K leads to
additional evidence towards the glassy nature of this magnetic phase. Finally,
the longitudinal relaxation of spin polarization (also supported by
results of ac susceptibility) evidences re-entrant glassy features similar to
amorphous ferromagnets.Comment: 15 pages, 13 figure
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