14,152 research outputs found
Boundary effects in entanglement entropy
We present a number of explicit calculations of Renyi and entanglement
entropies in situations where the entangling surface intersects the boundary in
-dimensional Minkowski spacetime. When the boundary is a single plane we
compute the contribution to the entropy due to this intersection, first in the
case of the Neumann and Dirichlet boundary conditions, and then in the case of
a generic Robin type boundary condition. The flow in the boundary coupling
between the Neumann and Dirichlet phases is analyzed in arbitrary dimension
and is shown to be monotonic, the peculiarity of case is noted. We argue
that the translational symmetry along the entangling surface is broken due the
presence of the boundary which reveals that the entanglement is not
homogeneous. In order to characterize this quantitatively, we introduce a
density of entanglement entropy and compute it explicitly. This quantity
clearly indicates that the entanglement is maximal near the boundary. We then
consider the situation where the boundary is composed of two parallel planes at
a finite separation and compute the entanglement entropy as well as its density
in this case. The complete contribution to entanglement entropy due to the
boundaries is shown not to depend on the distance between the planes and is
simply twice the entropy in the case of single plane boundary. Additionally, we
find how the area law, the part in the entropy proportional to the area of
entire entangling surface, depends on the size of the separation between the
two boundaries. The latter is shown to appear in the UV finite part of the
entropy.Comment: 22 pages, 3 figures; v2: new references adde
Multi-band spectroscopy of inhomogeneous Mott-insulator states of ultracold bosons
In this work, we use inelastic scattering of light to study the response of
inhomogeneous Mott-insulator gases to external excitations. The experimental
setup and procedure to probe the atomic Mott states are presented in detail. We
discuss the link between the energy absorbed by the gases and accessible
experimental parameters as well as the linearity of the response to the
scattering of light. We investigate the excitations of the system in multiple
energy bands and a band-mapping technique allows us to identify band and
momentum of the excited atoms. In addition the momentum distribution in the
Mott states which is spread over the entire first Brillouin zone enables us to
reconstruct the dispersion relation in the high energy bands using a single
Bragg excitation with a fixed momentum transfer.Comment: 19 pages, 7 figure
Management of Humeral Shaft Fractures; Non-Operative Versus Operative
Context: Functional humeral bracing remains the gold standard for treatment of humeral shaft fractures. There is an increasing trend in the literature to perform operative fixation of these fractures.
Evidence Acquisition: The aim of this systematic review was to compare the level one evidence for the outcome of non-operative with operative management of humeral shaft fractures in adults. A comprehensive electronic literature search of Medline and PubMed was performed with specific inclusion criteria to identify randomized controlled trials.
Results: In total, seventeen different studies were identified from the search terms and combinations used. Only one study met the inclusion criteria; however, this was a published study protocol of an ongoing trial currently being conducted. One additional published protocol for an ongoing trial was also identified, but this was for a prospective comparative observational study. Although this latter study may not be level one evidence, it would offer great insight into the functional outcome of humeral shaft fractures and economic implications of operative management, which is currently not addressed in the literature. Two retrospective comparative studies were also identified, one of which demonstrated a significantly lower rate of nonunion and malunion in those patients undergoing operative management.
Conclusions: This systematic review demonstrated a deficiency in the current literature of level one evidence available for the management of humeral shaft fractures. The current ongoing randomized control trail would offer a greater insight into the management of humeral shaft fractures and help confirm or refute the current literature. If this randomized control trial affirms the reduction in the rate of nonunion with operative fixation, a cost economic analysis is essential. As it would seem to offer operative management to all patients may be over treatment and not to offer this at all would undertreat
Getting into Uni in England and Australia: who you know, what you know or knowing the ropes?
Both England and Australia have displayed strong social democratic traditions in their approaches to
higher education expansion in the second half of the twentieth century, but are now continuing that expansion as part of a ‘neo-liberal’ reform agenda. This paper traces how the rhetoric of widening participation and equitable access to higher education has remained a key feature of policy discourse in both contexts, albeit with different inflections and effects over time and indeed between the two countries. It also shows how the longstanding relationship between higher education and social and cultural reproduction has endured despite a series of ‘social democratic’ and ‘neo-liberal’ policy initiatives that have ostensibly sought to weaken that link. It concludes that more needs to be done if the rhetoric of equity and social justice is to impact upon the reality of contemporary higher education in these two countries
Visualizing probabilistic models: Intensive Principal Component Analysis
Unsupervised learning makes manifest the underlying structure of data without
curated training and specific problem definitions. However, the inference of
relationships between data points is frustrated by the `curse of
dimensionality' in high-dimensions. Inspired by replica theory from statistical
mechanics, we consider replicas of the system to tune the dimensionality and
take the limit as the number of replicas goes to zero. The result is the
intensive embedding, which is not only isometric (preserving local distances)
but allows global structure to be more transparently visualized. We develop the
Intensive Principal Component Analysis (InPCA) and demonstrate clear
improvements in visualizations of the Ising model of magnetic spins, a neural
network, and the dark energy cold dark matter ({\Lambda}CDM) model as applied
to the Cosmic Microwave Background.Comment: 6 pages, 5 figure
Statistical modeling of HIV, tuberculosis, and Hepatitis B transmission in Ghana
Most mortality studies usually attribute death to single disease, while various other diseases could also act in the same individual or a population at large. Few works have been done by considering HIV, Tuberculosis (TB), and Hepatitis B (HB) as jointly acting in a population in spite of their high rate of infections in Ghana. This study applied competing risk methods on these three diseases by assuming they were the major risks in the study population. Among all opportunistic infections that could also act within HIV-infected individuals, TB has been asserted to be the most predominant. Other studies have also shown cases of HIV and Hepatitis B coinfections. The validity of these comorbidity assertions was statistically determined by exploring the conditional dependencies existing among HIV, TB, and HB through Bayesian networks or directed graphical model. Through Classification tree, sex and age group of individuals were found as significant demographic predictors that influence the prevalence of HIV and TB. Females were more likely to contract HIV, whereas males were prone to contracting TB
Long lasting instabilities in granular mixtures
We have performed experiments of axial segregation in the Oyama's drum. We
have tested binary granular mixtures during very long times. The segregation
patterns have been captured by a CCD camera and spatio-temporal graphs are
created. We report the occurence of instabilities which can last several hours.
We stress that those instabilities originate from the competition between axial
and radial segregations. We put into evidence the occurence of giant
fluctuations in the fraction of grain species along the surface during the
unstable periods.Comment: 10 pages, 10 figures, (2002
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