11,673 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
Strain-Modified RKKY Interaction in Carbon Nanotubes
For low-dimensional metallic structures, such as nanotubes, the exchange
coupling between localized magnetic dopants is predicted to decay slowly with
separation. The long-range character of this interaction plays a significant
role in determining the magnetic order of the system. It has previously been
shown that the interaction range depends on the conformation of the magnetic
dopants in both graphene and nanotubes. Here we examine the RKKY interaction in
carbon nanotubes in the presence of uniaxial strain for a range of different
impurity configurations. We show that strain is capable of amplifying or
attenuating the RKKY interaction, significantly increasing certain interaction
ranges, and acting as a switch: effectively turning on or off the interaction.
We argue that uniaxial strain can be employed to significantly manipulate
magnetic interactions in carbon nanotubes, allowing an interplay between
mechanical and magnetic properties in future spintronic devices. We also
examine the dimensional relationship between graphene and nanotubes with
regards to the decay rate of the RKKY interaction.Comment: 7 pages, 6 figures, submitte
Water calcium concentration modifies whole-body calcium uptake in sea bream larvae during short-term adaptation to altered salinities
Whole-body calcium uptake was studied in gilthead sea bream larvae (9–83·mg) in response to changing environmental salinity and [Ca2+]. Calcium uptake increased with increased fish size and salinity. Fish
exposed to calcium-enriched, diluted seawater showed increased calcium uptake compared with fish in diluted seawater alone. Calcium uptake was unchanged in Na+-
enriched, diluted seawater. Overall, [Ca2+], and not salinity/osmolarity per se, appears to be the main factor contributing to calcium uptake. By contrast, drinking was
reduced by a decrease in salinity/osmolarity but was little affected by external [Ca2+]. Calculations of the maximum contribution from drinking-associated calcium uptake
showed that it became almost insignificant (less than 10%) through a strong decrease in drinking rate at low salinities (0–8‰). Diluted seawater enriched in calcium to the
concentration present in full-strength seawater (i.e. constant calcium, decreasing salinity) restored intestinal calcium uptake to normal. Extra-intestinal calcium uptake
also benefited from calcium addition but to a lesser extent
Improved LeRoy-Bernstein near-dissociation expansion formula. Tutorial application to photoassociation spectroscopy of long-range states
NDE (Near-dissociation expansion) including LeRoy-Bernstein formulas are
improved by taking into account the multipole expansion coefficients and the
non asymptotic part of the potential curve. Applying these new simple
analytical formulas to photoassociation spectra of cold alkali atoms, we
improve the determination of the asymptotic coefficient, reaching a 1%
accuracy, for long-range relativistic potential curve of diatomic molecules.Comment: This article is part of Daniel Comparat's PhD thesis available at
http://tel.ccsd.cnrs.fr
Volatility Surface and Skewness in Live Cattle Futures Price Distributions with Application to North American BSE Announcements
options markets, live cattle, volatility, pricing density function, Financial Economics, Livestock Production/Industries, Risk and Uncertainty,
Mining and extractive urbanism: Postdevelopment in a Mozambican boomtown
Mozambique has attracted international attention in recent years following the discovery of huge reserves of coal and gas deposits. A major focus of Mozambique’s extractives boom is the province of Tete, once a remote outpost but now a hub of power generation for the southern African region and an emerging centre of global investment in coal extraction. Some of the world’s largest mining firms from both established and emerging economies have descended on Tete, investing billions of dollars in developing concessions to extract some of the world’s largest untapped coal reserves with wide-ranging implications for the region’s political economy and effecting significant shifts in relations between state, capital and territorial control. At the urban scale, Tete city and its expanding periphery are increasingly characterised by enclaves and spaces of enclosure, as some groups benefit from and are integrated into global circuits of production whilst others suffer displacement and dispossession. In seeking to trace the emergence of Tete’s resource economy, the paper contends that three distinctive spatialities have resulted from these developments, including the infrastructure networks being constructed around the extractive industries, the enclave spaces arising from the coal boom (and the particular labour geographies that shape them) and the new and distinctive urban geographies that are the product of Tete’s rapid urbanisation. The paper seeks to assess the impacts, stakes and challenges linked to investments in extractive activities and looks at how the costs and risks are being differentially distributed within and between the affected communities
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
Spaceflight Hazards of Escape-Velocity-Domain Impact Ejecta in the CR3BP
As a consequence of planned/proposed human lunar activity, the long-term effects of lunar debris and ejecta resulting from large-body (> 1000 kg) impacts on the lunar surface is investigated. The Escape-Velocity-Domain (EVD) ejecta behavior is characterized in terms of destination, duration in lunar orbit, and total displaced mass. Likewise, the amount of mass sent into geosynchronous orbit is also characterized and assessed as a function of impact location in terms of Sun-Earth-Moon angle, lunar latitude and longitude, and impact angle. Finally, a threat analysis is performed on critical assets in Earth and Lunar orbit such as the I.S.S., geosynchronous satellites, prospective lunar base, and the Deep Space Gateway now under construction
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