3,753 research outputs found
Dynamics and Asymptotics of Correlations in a Many-Body Localized System
We examine the dynamics of nearest-neighbor bipartite concurrence and total
correlations in the spin-1/2 model with random fields. We show, starting
from factorized random initial states, that the concurrence can suffer
entanglement sudden death in the long time limit and therefore may not be a
useful indicator of the properties of the system. In contrast, we show that the
total correlations capture the dynamics more succinctly, and further reveal a
fundamental difference in the dynamics governed by the ergodic versus many-body
localized phases, with the latter exhibiting dynamical oscillations. Finally,
we consider an initial state composed of several singlet pairs and show that by
fixing the correlation properties, while the dynamics do not reveal noticeable
differences between the phases, the long-time values of the correlation
measures appear to indicate the critical region.Comment: 5 pages, 5 figures. Close to published versio
Nonclassicality and criticality in symmetry-protected magnetic phases
Quantum and global discord in a spin-1 Heisenberg chain subject to single-ion
anisotropy (uniaxial field) are studied using exact diagonalisation and the
density matrix renormalisation group (DMRG). We find that these measures of
quantum nonclassicality are able to detect the quantum phase transitions
confining the symmetry protected Haldane phase and show critical scaling with
universal exponents. Moreover, in the case of thermal states, we find that
quantum discord can increase with increasing temperature.Comment: 7 pages, 6 figures, Close to published version. Includes a link to
data used for the figure
<i>In Situ</i> Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions
During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (~46.5% and ~61% of all particles; ~76.5 wt % and ~89 wt % of the relative particle load). Furthermore, ~69% and ~82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of ‘‘sand skirts.’’ Both sampled dust devils were relatively small (~15m and ~4–5m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ~58.5% to 73.5% of all lifted particles were small enough to go into suspension (<31 mm, depending on the used grain size classification). This relatively high amount represents only ~0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected
Optical addressing of an individual erbium ion in silicon
The detection of electron spins associated with single defects in solids is a
critical operation for a range of quantum information and measurement
applications currently under development. To date, it has only been
accomplished for two centres in crystalline solids: phosphorus in silicon using
electrical readout based on a single electron transistor (SET) and
nitrogen-vacancy centres in diamond using optical readout. A spin readout
fidelity of about 90% has been demonstrated with both electrical readout and
optical readout, however, the thermal limitations of the electrical readout and
the poor photon collection efficiency of the optical readout hinder achieving
the high fidelity required for quantum information applications. Here we
demonstrate a hybrid approach using optical excitation to change the charge
state of the defect centre in a silicon-based SET, conditional on its spin
state, and then detecting this change electrically. The optical frequency
addressing in high spectral resolution conquers the thermal broadening
limitation of the previous electrical readout and charge sensing avoids the
difficulties of efficient photon collection. This is done with erbium in
silicon and has the potential to enable new architectures for quantum
information processing devices and to dramatically increase the range of defect
centres that can be exploited. Further, the efficient electrical detection of
the optical excitation of single sites in silicon is a major step in developing
an interconnect between silicon and optical based quantum computing
technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of
"Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to
Can sexual selection theory inform genetic management of captive populations? A review
International audienceCaptive breeding for conservation purposes presents a serious practical challenge because several conflicting genetic processes (i.e., inbreeding depression, random genetic drift and genetic adaptation to captivity) need to be managed in concert to maximize captive population persistence and reintroduction success probability. Because current genetic management is often only partly successful in achieving these goals, it has been suggested that management insights may be found in sexual selection theory (in particular, female mate choice). We review the theoretical and empirical literature and consider how female mate choice might influence captive breeding in the context of current genetic guidelines for different sexual selection theories (i.e., direct benefits, good genes, compatible genes, sexy sons). We show that while mate choice shows promise as a tool in captive breeding under certain conditions, for most species, there is currently too little theoretical and empirical evidence to provide any clear guidelines that would guarantee positive fitness outcomes and avoid conflicts with other genetic goals. The application of female mate choice to captive breeding is in its infancy and requires a goal-oriented framework based on the needs of captive species management, so researchers can make honest assessments of the costs and benefits of such an approach, using simulations, model species and captive animal data
Multilocus sequence and microsatellite identification of intra-specific hybrids and ancestor-like donors among natural Ethiopian isolates of Leishmania donovani.
Protozoan parasites of the genus Leishmania (Kinetoplastida: Trypanosomatidae) cause widespread and devastating human diseases. Visceral leishmaniasis is endemic in Ethiopia where it has also been responsible for fatal epidemics. It is postulated that genetic exchange in Leishmania has implications for heterosis (hybrid vigour), spread of virulent strains, resistance to chemotherapeutics, and exploitation of different hosts and vectors. Here we analyse 11 natural Ethiopian Leishmania donovani isolates consisting of four putative hybrids, seven parent-like isolates and over 90 derived biological clones. We apply a novel combination of high resolution multilocus microsatellite typing (five loci) and multilocus sequence typing (four loci) that together distinguish parent-like and hybrid L. donovani strains. Results indicate that the four isolates (and their associated biological clones) are genetic hybrids, not the results of mixed infections, each possessing heterozygous markers consistent with inheritance of divergent alleles from genetically distinct Ethiopian L. donovani lineages. The allelic profiles of the putative hybrids may have arisen from a single hybridisation event followed by inbreeding or gene conversion, or alternatively from two or more hybridisation events. Mitochondrial sequencing showed uniparental maxicircle inheritance for all of the hybrids, each possessing a single mitochondrial genotype. Fluorescence activated cell sorting analysis of DNA content demonstrated that all hybrids and their associated clones were diploid. Together the data imply that intra-specific genetic exchange is a recurrent feature of natural L. donovani populations, with substantial implications for the phyloepidemiology of Leishmania
Studies of Relativistic Jets in Active Galactic Nuclei with SKA
Relativistic jets in active galactic nuclei (AGN) are among the most powerful
astrophysical objects discovered to date. Indeed, jetted AGN studies have been
considered a prominent science case for SKA, and were included in several
different chapters of the previous SKA Science Book (Carilli & Rawlings 2004).
Most of the fundamental questions about the physics of relativistic jets still
remain unanswered, and await high-sensitivity radio instruments such as SKA to
solve them. These questions will be addressed specially through analysis of the
massive data sets arising from the deep, all-sky surveys (both total and
polarimetric flux) from SKA1. Wide-field very-long-baseline-interferometric
survey observations involving SKA1 will serve as a unique tool for
distinguishing between extragalactic relativistic jets and star forming
galaxies via brightness temperature measurements. Subsequent SKA1 studies of
relativistic jets at different resolutions will allow for unprecedented
cosmological studies of AGN jets up to the epoch of re-ionization, enabling
detailed characterization of the jet composition, magnetic field, particle
populations, and plasma properties on all scales. SKA will enable us to study
the dependence of jet power and star formation on other properties of the AGN
system. SKA1 will enable such studies for large samples of jets, while VLBI
observations involving SKA1 will provide the sensitivity for pc-scale imaging,
and SKA2 (with its extraordinary sensitivity and dynamic range) will allow us
for the first time to resolve and model the weakest radio structures in the
most powerful radio-loud AGN.Comment: 19 pages, 4 figures; to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14_093
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