1,429 research outputs found
A combinatorial smoothness criterion for spherical varieties
We suggest a combinatorial criterion for the smoothness of an arbitrary
spherical variety using the classification of multiplicity-free spaces,
generalizing an earlier result of Camus for spherical varieties of type .Comment: 14 pages, 2 table
Nanofibre-based trap for Rb molecule
We describe a theoretical proposal of a nanofibre-based trap for a Rb
molecule prepared in the metastable state . The trapping
potential results from the combination of a travelling and a standing-wave
fields, both carried by the fundamental guided mode HE of the fibre. We
show that, with an experimentally realistic choice of laser frequencies and
powers, one can implement a K-deep well at nm
from the fibre surface accomodating for translational molecular
states
Stress deformations and structural quenching in Sm0.5Ca0.5MnO3 thin films allow a huge decrease of the charge order melting magnetic field
Thin films of Sm0.5Ca0.5MnO3 manganites with charge ordering (CO) properties
and colossal magnetoresistance were synthesized by pulsed laser deposition
technique on (100)-SrTiO3 and (100)-LaAlO3 substrates. We first compare the
structural modifications as function of the substrate and film thickness.
Secondly, measuring transport properties in magnetic fields up to 24T, we
establish the temperature-field phase diagram describing the stability of the
CO state and compare it to bulk material. We show that some structural
modification induced by the substrate occurs and that the CO melting magnetic
field is greatly reduced. Moreover, with the temperature decrease, no
modification of the lattice parameters is observed. We then propose an
explanation based on the quenching of the unit cell of the film that adopts the
in-plane lattice parameters of the substrate and thus, prevents the complete
growth of the CO state at low temperature.Comment: to be published in Journal of Applied Physic
Marked influence of the nature of chemical bond on CP-violating signature in molecular ions and
Heavy polar molecules offer a great sensitivity to the electron Electric
Dipole Moment(EDM). To guide emerging searches for EDMs with molecular ions, we
estimate the EDM-induced energy corrections for hydrogen halide ions
and in their respective ground states. We find that the energy corrections due to EDM for the two
ions differ by an unexpectedly large factor of fifteen. We demonstrate that a
major part of this enhancement is due to a dissimilarity in the nature of the
chemical bond for the two ions: the bond that is nearly of ionic character in
exhibits predominantly covalent nature in .
We conclude that because of this enhancement the HI ion may be a
potentially competitive candidate for the EDM search.Comment: This manuscript has been accepted for publication in Physical Review
Letters. The paper is now being prepared for publicatio
Phonons in the multiferroic langasite BaNbFeSiO : evidences for symmetry breaking
The chiral langasite BaNbFeSiO is a multiferroic
compound. While its magnetic order below T=27 K is now well characterised,
its polar order is still controversial. We thus looked at the phonon spectrum
and its temperature dependence to unravel possible crystal symmetry breaking.
We combined optical measurements (both infrared and Raman spectroscopy) with ab
initio calculations and show that signatures of a polar state are clearly
present in the phonon spectrum even at room temperature. An additional symmetry
lowering occurs below 120~K as seen from emergence of softer phonon modes in
the THz range. These results confirm the multiferroic nature of this langasite
and open new routes to understand the origin of the polar state
Large phenotype jumps in biomolecular evolution
By defining the phenotype of a biopolymer by its active three-dimensional
shape, and its genotype by its primary sequence, we propose a model that
predicts and characterizes the statistical distribution of a population of
biopolymers with a specific phenotype, that originated from a given genotypic
sequence by a single mutational event. Depending on the ratio g0 that
characterizes the spread of potential energies of the mutated population with
respect to temperature, three different statistical regimes have been
identified. We suggest that biopolymers found in nature are in a critical
regime with g0 in the range 1-6, corresponding to a broad, but not too broad,
phenotypic distribution resembling a truncated Levy flight. Thus the biopolymer
phenotype can be considerably modified in just a few mutations. The proposed
model is in good agreement with the experimental distribution of activities
determined for a population of single mutants of a group I ribozyme.Comment: to appear in Phys. Rev. E; 7 pages, 6 figures; longer discussion in
VII, new fig.
Relations between Rydberg-valence interactions in the Oâ‚‚ molecule
Using a single-configuration formulation, analytical expressions are derived for the (X²Πg) nsσg, npπu, and npσu Rydberg-valence interaction matrix elements in O₂. In addition, new results from diabatic, coupled-channel deperturbations of experimental data dependent on these interactions are reported for n=3 and 4. Using these results, the large differences in magnitude between the Rydberg-valence couplings for the constituent states of the npπuRydberg complex that are predicted by the analytical expressions are verified experimentally. Effective values for several two-electron integrals are obtained semiempirically through comparison between analytical expressions and deperturbed experimental values for the Rydberg-state energies and Rydberg-valence couplings, allowing predictions to be made for the spectroscopy of the npπu ¹Σ−uRydberg states which have yet to be observed
High-resolution Fourier-transform XUV photoabsorption spectroscopy of 14N15N
The first comprehensive high-resolution photoabsorption spectrum of 14N15N
has been recorded using the Fourier-transform spectrometer attached to the
Desirs beamline at the Soleil synchrotron. Observations are made in the extreme
ultraviolet (XUV) and span 100,000-109,000 cm-1 (100-91.7 nm). The observed
absorption lines have been assigned to 25 bands and reduced to a set of
transition energies, f values, and linewidths. This analysis has verified the
predictions of a theoretical model of N2 that simulates its photoabsorption and
photodissociation cross section by solution of an isotopomer independent
formulation of the coupled-channel Schroedinger equation. The mass dependence
of predissociation linewidths and oscillator strengths is clearly evident and
many local perturbations of transition energies, strengths, and widths within
individual rotational series have been observed.Comment: 14 pages, 8 figures, one data archiv
Formation of collective spins in frustrated clusters
Using magnetization, specific heat and neutron scattering measurements, as
well as exact calculations on realistic models, the magnetic properties of the
\lacuvo compound are characterized on a wide temperature range. At high
temperature, this oxide is well described by strongly correlated atomic =1/2
spins while decreasing the temperature it switches to a set of weakly
interacting and randomly distributed entangled pseudo spins and
. These pseudo-spins are built over frustrated clusters, similar to
the kagom\'e building block, at the vertices of a triangular superlattice, the
geometrical frustration intervening then at different scales.Comment: 10 page
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