Scale-invariance in gravity and implications for the cosmological constant

Recently a scale invariant theory of gravity was constructed by imposing a conformal symmetry on general relativity. The imposition of this symmetry changed the configuration space from superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms - to conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. However, despite numerous attractive features, the theory suffers from at least one major problem: the volume of the universe is no longer a dynamical variable. In attempting to resolve this problem a new theory is found which has several surprising and atractive features from both quantisation and cosmological perspectives. Furthermore, it is an extremely restrictive theory and thus may provide testable predictions quickly and easily. One particularly interesting feature of the theory is the resolution of the cosmological constant problem.Comment: Replaced with final version: minor changes to text; references adde

Beef Cattle Instance Segmentation Using Fully Convolutional Neural Network

In this paper we present a novel instance segmentation algorithm that extends a fully convolutional network to learn to label objects separately without prediction of regions of interest. We trained the new algorithm on a challenging CCTV recording of beef cattle, as well as benchmark MS COCO and Pascal VOC datasets. Extensive experimentation showed that our approach outperforms the state-of-the-art solutions by up to 8% on our data

Scale-invariant gravity: Spacetime recovered

The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Recently a manifestly 3-dimensional theory was constructed with conformal superspace as the configuration space. Here a fully 4-dimensional action is constructed so as to be invariant under conformal transformations of the 4-metric using general relativity as a guide. This action is then decomposed to a (3+1)-dimensional form and from this to its Jacobi form. The surprising thing is that the new theory turns out to be precisely the original 3-dimensional theory. The physical data is identified and used to find the physical representation of the theory. In this representation the theory is extremely similar to general relativity. The clarity of the 4-dimensional picture should prove very useful for comparing the theory with those aspects of general relativity which are usually treated in the 4-dimensional framework.Comment: Replaced with final version: minor changes to tex

The physical gravitational degrees of freedom

When constructing general relativity (GR), Einstein required 4D general covariance. In contrast, we derive GR (in the compact, without boundary case) as a theory of evolving 3-dimensional conformal Riemannian geometries obtained by imposing two general principles: 1) time is derived from change; 2) motion and size are relative. We write down an explicit action based on them. We obtain not only GR in the CMC gauge, in its Hamiltonian 3 + 1 reformulation but also all the equations used in York's conformal technique for solving the initial-value problem. This shows that the independent gravitational degrees of freedom obtained by York do not arise from a gauge fixing but from hitherto unrecognized fundamental symmetry principles. They can therefore be identified as the long-sought Hamiltonian physical gravitational degrees of freedom.Comment: Replaced with published version (minor changes and added references

Dominating cliques in graphs

AbstractA set of vertices is a dominating set in a graph if every vertex not in the dominating set is adjacent to one or more vertices in the dominating set. A dominating clique is a dominating set that induces a complete subgraph. Forbidden subgraph conditions sufficient to imply the existence of a dominating clique are given. For certain classes of graphs, a polynomial algorithm is given for finding a dominating clique. A forbidden subgraph characterization is given for a class of graphs that have a connected dominating set of size three

Economic Aspects of the Irish Exchange Control Regime. Quarterly Economic Commentary Special Article, April 1980

From the foundation of the State until March 1979, the Irish currency was maintained in a fixed one-to-one parity with the pound sterling. Aside from the 50% deposit requirement on capital inflows through the banking system imposed by the Central Bank in recent years, there were no significant restrictions on the movement of funds between Ireland and the sterling area. Capital movements between Ireland and non-sterling countries were subject to exchange control regulations broadly similar to the UK's own, although in practice they were administered in a somewhat more liberal fashion. The Irish controls could be seen as, in effect, part of the price of our membership of the sterling zone, since the UK's own controls would have been circumvented very readily if Ireland had presented an uncontrolled "window" to the rest of the world. So purchases of financial assets in non-sterling countries had to be financed through the dollar premium pool or through foreign currency loans

Evaluation of lightweight wheelchairs using ANSI/RESNA testing standards

Lightweight wheelchairs are characterized by their low cost and limited range of adjustment. Our study evaluated three different folding lightweight wheelchair models using the American National Standards Institute/Rehabilitation Engineering Society of North America (ANSI/RESNA) standards to see whether quality had improved since the previous data were reported. On the basis of reports of increasing breakdown rates in the community, we hypothesized that the quality of these wheelchairs had declined. Seven of the nine wheelchairs tested failed to pass the multidrum test durability requirements. An average of 194,502 +/- 172,668 equivalent cycles was completed, which is similar to the previous test results and far below the 400,000 minimum required to pass the ANSI/ RESNA requirements. This was also significantly worse than the test results for aluminum ultralight folding wheelchairs. Overall, our results uncovered some disturbing issues with these wheelchairs and suggest that manufacturers should put more effort into this category to improve quality. To improve the durability of lightweight wheelchairs, we suggested that stronger regulations be developed that require wheelchairs to be tested by independent and certified test laboratories. We also proposed a wheelchair rating system based on the National Highway Transportation Safety Administration vehicle crash ratings to assist clinicians and end users when comparing the durability of different wheelchairs

The Maryland Hospital Regulation System and Its Effect on Hospital Pricing and Costs

Thesis advisor: Francis M. McLaughlinThis thesis examines the impact of the hospital regulatory system in the state of Maryland. The system has been highly successful in lowering the gross charge-to-cost ratios that hospitals charge to their patients. In many states, these charge markups appear to be exorbitantly high, which is a great concern since the cost of health care is becoming more and more expensive for Americans. This thesis will include a description of the regulatory agency in Maryland, an explanation of how it works, and how it affects the Maryland hospital sector. Econometric analysis will then be employed in order to determine whether or not the regulatory system successfully helps hospitals reduce costs, a high priority objective of the system. In this model, Maryland hospital costs will be compared with nearby hospitals in Virginia. The paper will conclude with an evaluation of the merits of the system, and a recommendation on whether or not it would be useful in other states.Thesis (BS) — Boston College, 2008.Submitted to: Boston College. College of Arts and Sciences.Discipline: Economics.Discipline: College Honors Program.Discipline: Economics Honors Program