13,509 research outputs found
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
We study the motion of a vortex dipole in a Bose-Einstein condensate confined
to an anisotropic trap. We focus on a system of ordinary differential equations
describing the vortices' motion, which is in turn a reduced model of the
Gross-Pitaevskii equation describing the condensate's motion. Using a sequence
of canonical changes of variables, we reduce the dimension and simplify the
equations of motion. We uncover two interesting regimes. Near a family of
periodic orbits known as guiding centers, we find that the dynamics is
essentially that of a pendulum coupled to a linear oscillator, leading to
stochastic reversals in the overall direction of rotation of the dipole. Near
the separatrix orbit in the isotropic system, we find other families of
periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the
guiding center orbits, we derive an explicit iterated map that simplifies the
problem further. Numerical calculations are used to illustrate the phenomena
discovered through the analysis. Using the results from the reduced system we
are able to construct complex periodic orbits in the original, partial
differential equation, mean-field model for Bose-Einstein condensates, which
corroborates the phenomenology observed in the reduced dynamical equations
Parts of Quantum States
It is shown that generic N-party pure quantum states (with equidimensional
subsystems) are uniquely determined by their reduced states of just over half
the parties; in other words, all the information in almost all N-party pure
states is in the set of reduced states of just over half the parties. For N
even, the reduced states in fewer than N/2 parties are shown to be an
insufficient description of almost all states (similar results hold when N is
odd). It is noted that Real Algebraic Geometry is a natural framework for any
analysis of parts of quantum states: two simple polynomials, a quadratic and a
cubic, contain all of their structure. Algorithmic techniques are described
which can provide conditions for sets of reduced states to belong to pure or
mixed states.Comment: 10 pages, 1 figur
Neutrino masses, cosmological bound and four zero Yukawa textures
Four zero neutrino Yukawa textures in a specified weak basis, combined with
symmetry and type-I seesaw, yield a highly constrained and predictive
scheme. Two alternately viable light neutrino Majorana mass matrices
result with inverted/normal mass ordering. Neutrino
masses, Majorana in character and predicted within definite ranges with
laboratory and cosmological inputs, will have their sum probed cosmologically.
The rate for decay, though generally below the reach of
planned experiments, could approach it in some parameter region. Departure from
symmetry due to RG evolution from a high scale and consequent CP
violation, with a Jarlskog invariant whose magnitude could almost reach
, are explored.Comment: Published versio
The properties of the inner disk around HL Tau: Multi-wavelength modeling of the dust emission
We conducted a detailed radiative transfer modeling of the dust emission from
the circumstellar disk around HL Tau. The goal of our study is to derive the
surface density profile of the inner disk and its structure. In addition to the
Atacama Large Millimeter/submillimeter Array images at Band 3 (2.9mm), Band 6
(1.3mm), and Band 7 (0.87mm), the most recent Karl G. Jansky Very Large Array
(VLA) observations at 7mm were included in the analysis. A simulated annealing
algorithm was invoked to search for the optimum model. The radiative transfer
analysis demonstrates that most radial components (i.e., >6AU) of the disk
become optically thin at a wavelength of 7mm, which allows us to constrain, for
the first time, the dust density distribution in the inner region of the disk.
We found that a homogeneous grain size distribution is not sufficient to
explain the observed images at different wavelengths simultaneously, while
models with a shallower grain size distribution in the inner disk work well. We
found clear evidence that larger grains are trapped in the first bright ring.
Our results imply that dust evolution has already taken place in the disk at a
relatively young (i.e., ~1Myr) age. We compared the midplane temperature
distribution, optical depth, and properties of various dust rings with those
reported previously. Using the Toomre parameter, we briefly discussed the
gravitational instability as a potential mechanism for the origin of the dust
clump detected in the first bright ring via the VLA observations.Comment: Accepted for publication in A&A (10 pages
Limits on Associated Production of Visibly and Invisibly Decaying Higgs Bosons from Z Decays
Many extensions of the standard electroweak model Higgs sector suggest that
the main Higgs decay channel is "invisible", for example, where
denotes the majoron, a weakly interacting pseudoscalar Goldstone boson
associated to the spontaneous violation of lepton number. In many of these
models the Higgs boson may also be produced in association to a massive
pseudoscalar boson (HA), in addition to the standard Bjorken mechanism (HZ). We
describe a general strategy to determine limits from LEP data on the masses and
couplings of such Higgs bosons, using the existing data on acoplanar dijet
events as well as data on four and six jet event topologies. For the sake
of illustration, we present constraints that can be obtained for the ALEPH
data.Comment: FTUV/94-36, IFIC/94-31 TIFR/TH/94--25, 12 pages + 4 figures (included
as ps files at the end
Integrating imaging-based classification and transcriptomics for quality assessment of human oocytes according to their reproductive efficiency
PURPOSE: Utilising non-invasive imaging parameters to assess human oocyte fertilisation, development and implantation; and their influence on transcriptomic profiles. METHODS: A ranking tool was designed using imaging data from 957 metaphase II stage oocytes retrieved from 102 patients undergoing ART. Hoffman modulation contrast microscopy was conducted with an Olympus IX53 microscope. Images were acquired prior to ICSI and processed using ImageJ for optical density and grey-level co-occurrence matrices texture analysis. Single-cell RNA sequencing of twenty-three mature oocytes classified according to their competence was performed. RESULT(S): Overall fertilisation, blastulation and implantation rates were 73.0%, 62.6% and 50.8%, respectively. Three different algorithms were produced using binary logistic regression methods based on "optimal" quartiles, resulting in an accuracy of prediction of 76.6%, 67% and 80.7% for fertilisation, blastulation and implantation. Optical density, gradient, inverse difference moment (homogeneity) and entropy (structural complexity) were the parameters with highest predictive properties. The ranking tool showed high sensitivity (68.9-90.8%) but with limited specificity (26.5-62.5%) for outcome prediction. Furthermore, five differentially expressed genes were identified when comparing "good" versus "poor" competent oocytes. CONCLUSION(S): Imaging properties can be used as a tool to assess differences in the ooplasm and predict laboratory and clinical outcomes. Transcriptomic analysis suggested that oocytes with lower competence may have compromised cell cycle either by non-reparable DNA damage or insufficient ooplasmic maturation. Further development of algorithms based on image parameters is encouraged, with an increased balanced cohort and validated prospectively in multicentric studies
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