4,443 research outputs found
Creating exotic condensates via quantum-phase-revival dynamics in engineered lattice potentials
In the field of ultracold atoms in optical lattices a plethora of phenomena
governed by the hopping energy and the interaction energy have been
studied in recent years. However, the trapping potential typically present in
these systems sets another energy scale and the effects of the corresponding
time scale on the quantum dynamics have rarely been considered. Here we study
the quantum collapse and revival of a lattice Bose-Einstein condensate (BEC) in
an arbitrary spatial potential, focusing on the special case of harmonic
confinement. Analyzing the time evolution of the single-particle density
matrix, we show that the physics arising at the (temporally) recurrent quantum
phase revivals is essentially captured by an effective single particle theory.
This opens the possibility to prepare exotic non-equilibrium condensate states
with a large degree of freedom by engineering the underlying spatial lattice
potential.Comment: 9 pages, 6 figure
Effect of charmed meson loops on charmonium transitions
The effects of intermediate charmed mesons on charmonium transitions with the
emission of one pion or eta are studied systematically. Based on a
non-relativistic effective field theory we show that charmed meson loops are
enhanced compared to the corresponding tree-level contributions for transitions
between two S-wave charmonia as well as for transitions between two P-wave
charmonia. On the contrary, for the transitions between one S-wave and one
P-wave charmonium state, the loops need to be analyzed case by case and often
appear to be suppressed. The relation to and possible implications for an
effective Lagrangian approach are also discussed. This study at the same time
provides a cross check for the numerical evaluations.Comment: 50 pages, 13 figures. More discussions on the power counting, scaling
of the coupling constants discussed. Conclusions unchanged. Version accepted
for publication in PR
Ionization of clusters in intense laser pulses through collective electron dynamics
The motion of electrons and ions in medium-sized rare gas clusters (1000
atoms) exposed to intense laser pulses is studied microscopically by means of
classical molecular dynamics using a hierarchical tree code. Pulse parameters
for optimum ionization are found to be wavelength dependent. This resonant
behavior is traced back to a collective electron oscillation inside the charged
cluster. It is shown that this dynamics can be well described by a driven and
damped harmonic oscillator allowing for a clear discrimination against other
energy absorption mechanisms.Comment: 4 pages (4 figures
Prediction of gene–phenotype associations in humans, mice, and plants using phenologs
All authors are with the Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA. -- Ulf Martin Singh-Blom is with the Program in Computational and Applied Mathematics, The University of Texas at Austin, Austin, TX 78712, USA, and th Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm 171 76, Sweden. -- Kriston L. McGary is with the Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.Background: Phenotypes and diseases may be related to seemingly dissimilar phenotypes in other species by means of the orthology of underlying genes. Such “orthologous phenotypes,” or “phenologs,” are examples of deep homology, and may be used to predict additional candidate disease genes.
Results: In this work, we develop an unsupervised algorithm for ranking phenolog-based candidate disease genes through the integration of predictions from the k nearest neighbor phenologs, comparing classifiers and weighting functions by cross-validation. We also improve upon the original method by extending the theory to paralogous phenotypes. Our algorithm makes use of additional phenotype data — from chicken, zebrafish, and E. coli, as well as new datasets for C. elegans — establishing that several types of annotations may be treated as phenotypes. We demonstrate the use of our algorithm to predict novel candidate genes for human atrial fibrillation (such as HRH2, ATP4A, ATP4B, and HOPX) and epilepsy (e.g., PAX6 and NKX2-1). We suggest gene candidates for pharmacologically-induced seizures in mouse, solely based on orthologous phenotypes from E. coli. We also explore the prediction of plant gene–phenotype associations, as for the Arabidopsis response to vernalization phenotype.
Conclusions: We are able to rank gene predictions for a significant portion of the diseases in the Online Mendelian Inheritance in Man database. Additionally, our method suggests candidate genes for mammalian seizures based only on bacterial phenotypes and gene orthology. We demonstrate that phenotype information may come from diverse sources, including drug sensitivities, gene ontology biological processes, and in situ hybridization annotations. Finally, we offer testable candidates for a variety of human diseases, plant traits, and other classes of phenotypes across a wide array of species.Center for Systems and Synthetic BiologyInstitute for Cellular and Molecular [email protected]
A study of the parity-odd nucleon-nucleon potential
We investigate the parity-violating nucleon-nucleon potential as obtained in
chiral effective field theory. By using resonance saturation we compare the
chiral potential to the more traditional one-meson exchange potential. In
particular, we show how parameters appearing in the different approaches can be
compared with each other and demonstrate that analyses of parity violation in
proton-proton scattering within the different approaches are in good agreement.
In the second part of this work, we extend the parity-violating potential to
next-to-next-to-leading order. We show that generally it includes both
one-pion- and two-pion-exchange corrections, but the former play no significant
role. The two-pion-exchange corrections depend on five new low-energy constants
which only become important if the leading-order weak pion-nucleon constant
turns out to be very small.Comment: Published versio
Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the D_{s0}^*(2317)
We study the scattering of light pseudoscalar mesons (, ) off charmed
mesons (, ) in full lattice QCD. The S-wave scattering lengths are
calculated using L\"uscher's finite volume technique. We use a relativistic
formulation for the charm quark. For the light quark, we use domain-wall
fermions in the valence sector and improved Kogut-Susskind sea quarks. We
calculate the scattering lengths of isospin-3/2 , , ,
isospin-0 and isospin-1 channels on the lattice. For the
chiral extrapolation, we use a chiral unitary approach to next-to-leading
order, which at the same time allows us to give predictions for other channels.
It turns out that our results support the interpretation of the
as a molecule. At the same time, we also update a
prediction for the isospin breaking hadronic decay width
to keV.Comment: 22 pages, 5 figures; a typo in Table II corrected (for the
coefficients of the NLO amplitudes
Comment on "Quantum Friction - Fact or Fiction?"
If quantum friction existed [J.B. Pendry, New J. Phys. 12, 033028 (2010)] an
unlimited amount of useful energy could be extracted from the quantum vacuum
and Lifshitz theory would fail. Both are unlikely to be true.Comment: Comment on J.B. Pendry, New J. Phys. 12, 033028 (2010
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