380 research outputs found
Spinor BECs in a double-well: population transfer and Josephson oscillations
The dynamics of an F=1 spinor condensate in a two-well potential is studied
within the framework of the Gross-Pitaevskii equation. We derive two-mode
equations relating the population imbalances, the phase differences among the
condensates at each side of the barrier and the time evolution of the different
Zeeman populations for the case of small population imbalances. The case of
zero total magnetization is scrutinized in this limit demonstrating the ability
of a two mode analysis to describe to a large extent the dynamics observed in
the Gross-Pitaevskii equations. It is also demonstrated that the time evolution
of the different total populations fully decouples from the Josephson tunneling
phenomena. All the relevant time scales are clearly identified with microscopic
properties of the atom-atom interactions
Dynamic generation of spin-squeezed states in bosonic Josephson junctions
We analyze the formation of squeezed states in a condensate of ultracold
bosonic atoms confined by a double-well potential. The emphasis is set on the
dynamical formation of such states from initially coherent many-body quantum
states. Two cases are described: the squeezing formation in the evolution of
the system around the stable point, and in the short time evolution in the
vicinity of an unstable point. The latter is shown to produce highly squeezed
states on very short times. On the basis of a semiclassical approximation to
the Bose-Hubbard Hamiltonian, we are able to predict the amount of squeezing,
its scaling with and the speed of coherent spin formation with simple
analytical formulas which successfully describe the numerical Bose-Hubbard
results. This new method of producing highly squeezed spin states in systems of
ultracold atoms is compared to other standard methods in the literature.Comment: 12 pages, revised discussion + added reference
New research and trends in higher education
New methodologies, contexts, and technologies are generating a lot of interest in the field of higher education, and this Special Issue intends to address the current research and trends in all dimensions of higher education. It will serve as a global focal point for the examination and reporting of a wide range of issues affecting higher education learning processes: innovations in learning, new pedagogical methods and new learning contexts. The Special Issue includes original research contributions, such as research papers, case studies and demonstrations with original scientific results, methodological aspects, concepts and educational technologies on the following topics: (a) Technological Developments in Higher Education: mobile technology, virtual environments, augmented reality, automation and robotics and other tools for universal learning, focusing on issues that are not addressed by existing research. (b) Digital Higher Education: mobile learning, eLearning, Game-based Learning, social media in education, new learning models and technologies and wearable technologies for education. (c) Case Studies in Higher Education: empirical studies in higher education regarding digital technologies, new methodologies, new evaluation techniques and tools, perceptions of learning processes efficiency and digital learning best practices.info:eu-repo/semantics/publishedVersio
Spin-driven spatial symmetry breaking of spinor condensates in a double-well
The properties of an F=1 spinor Bose-Einstein condensate trapped in a
double-well potential are discussed using both a mean-field two-mode approach
and a simplified two-site Bose-Hubbard Hamiltonian. We focus in the region of
phase space in which spin effects lead to a symmetry breaking of the system,
favoring the spatial localization of the condensate in one well. To model this
transition we derive, using perturbation theory, an effective Hamiltonian that
describes N/2 spin singlets confined in a double-well potential.Comment: 12 pages, 5 figure
A dipolar self-induced bosonic Josephson junction
We propose a new scheme for observing Josephson oscillations and macroscopic
quantum self-trapping phenomena in a toroidally confined Bose-Einstein
condensate: a dipolar self-induced Josephson junction. Polarizing the atoms
perpendicularly to the trap symmetry axis, an effective ring-shaped,
double-well potential is achieved which is induced by the dipolar interaction.
By numerically solving the three-dimensional time-dependent Gross-Pitaevskii
equation we show that coherent tunneling phenomena such as Josephson
oscillations and quantum self-trapping can take place. The dynamics in the
self-induced junction can be qualitatively described by a two-mode model taking
into account both s-wave and dipolar interactions.Comment: Major changes. Accepted for publication in EP
Data science strategies leading to the development of data scientists’ skills in organizations
The purpose of this paper is to compare the strategies of companies with data science practices and methodologies and the data specificities/variables that can influence the definition of a data science strategy in pharma companies. The current paper is an empirical study, and the research approach consists of verifying against a set of statistical tests the differences between companies with a data science strategy and companies without a data science strategy. We have designed a specific questionnaire and applied it to a sample of 280 pharma companies. The main findings are based on the analysis of these variables: overwhelming volume, managing unstructured data, data quality, availability of data, access rights to data, data ownership issues, cost of data, lack of pre-processing facilities, lack of technology, shortage of talent/skills, privacy concerns and regulatory risks, security, and difficulties of data portability regarding companies with a data science strategy and companies without a data science strategy. The paper offers an in-depth comparative analysis between companies with or without a data science strategy, and the key limitation is regarding the literature review as a consequence of the novelty of the theme; there is a lack of scientific studies regarding this specific aspect of data science. In terms of the practical business implications, an organization with a data science strategy will have better direction and management practices as the decision-making process is based on accurate and valuable data, but it needs data scientists skills to fulfil those goals.info:eu-repo/semantics/acceptedVersio
Self-trapping of a binary Bose-Einstein condensate induced by interspecies interaction
The problem of self-trapping of a Bose-Einstein condensate (BEC) and a binary
BEC in an optical lattice (OL) and double well (DW) is studied using the
mean-field Gross-Pitaevskii equation. For both DW and OL, permanent
self-trapping occurs in a window of the repulsive nonlinearity of the GP
equation: . In case of OL, the critical nonlinearities
and correspond to a window of chemical potentials
defining the band gap(s) of the periodic OL. The
permanent self-trapped BEC in an OL usually represents a breathing oscillation
of a stable stationary gap soliton. The permanent self-trapped BEC in a DW, on
the other hand, is a dynamically stabilized state without any stationary
counterpart. For a binary BEC with intraspecies nonlinearities outside this
window of nonlinearity, a permanent self trapping can be induced by tuning the
interspecies interaction such that the effective nonlinearities of the
components fall in the above window
Influence of water availability in the distributions of branched glycerol dialkyl glycerol tetraether in soils of the Iberian Peninsula
The combined application of the MBT (degree of methylation) and CBT (degree
of cyclization) indices, based on the distribution of branched glycerol
dialkyl glycerol tetraethers (brGDGTs) in soils, has been proposed as a
paleoproxy to estimate mean annual temperature (MAT). CBT quantifies the
degree of cyclization of brGDGTs and relates to soil pH. MBT and the
simplified version MBT' quantify the degree of methylation of brGDGTs and
relate to MAT and soil pH. However, other factors such as soil water
availability have also been suggested to influence MBT' and possibly restrict
the combined application of the MBT' and CBT indices as a paleotemperature
proxy. To assess the effect of hydrological conditions on MBT' and CBT, a set
of 23 Iberian Peninsula soil samples, covering a MAT range from
10 to 18 °C and a mean annual precipitation (MAP) range of 405 mm to
1455 mm, was analyzed. We found that the CBT was indeed significantly
correlated with soil pH in our sample set. In contrast, MBT' was not correlated
with MAT but had a significant correlation with the aridity index (AI), a
parameter related to water availability in soils. The AI can explain 50%
of the variation of the MBT', and 70% of the residuals of MAT estimated
with the MBT/CBT proxy as compared to instrumentally measured MAT. We propose
that, in arid settings, where water may be an ecologically limiting factor,
MBT' is influenced by hydrological conditions rather than temperature. Thus,
our results suggest that the combination of MBT' and CBT indices should be
applied with caution in paleotemperature reconstructions in soils from dry
subhumid to hyperarid environments
Branched GDGT variability in sediments and soils from catchments with marked temperature seasonality
acceptedVersio
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