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 $d$-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 $d$ and is shown to be monotonic, the peculiarity of $d=3$ 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