7,621 research outputs found
Fractal universe and quantum gravity
We propose a field theory which lives in fractal spacetime and is argued to
be Lorentz invariant, power-counting renormalizable, ultraviolet finite, and
causal. The system flows from an ultraviolet fixed point, where spacetime has
Hausdorff dimension 2, to an infrared limit coinciding with a standard
four-dimensional field theory. Classically, the fractal world where fields live
exchanges energy momentum with the bulk with integer topological dimension.
However, the total energy momentum is conserved. We consider the dynamics and
the propagator of a scalar field. Implications for quantum gravity, cosmology,
and the cosmological constant are discussed.Comment: 4 pages. v2: typos corrected; v3: discussion improved, intuitive
introduction added, matches the published versio
Triple-Star Candidates Among the Kepler Binaries
We present the results of a search through the photometric database of
eclipsing Kepler binaries (Prsa et al. 2011; Slawson et al. 2011) looking for
evidence of hierarchical triple star systems. The presence of a third star
orbiting the binary can be inferred from eclipse timing variations. We apply a
simple algorithm in an automated determination of the eclipse times for all
2157 binaries. The "calculated" eclipse times, based on a constant period
model, are subtracted from those observed. The resulting O-C (observed minus
calculated times) curves are then visually inspected for periodicities in order
to find triple-star candidates. After eliminating false positives due to the
beat frequency between the ~1/2-hour Kepler cadence and the binary period, 39
candidate triple systems were identified. The periodic O-C curves for these
candidates were then fit for contributions from both the classical Roemer delay
and so-called "physical" delay, in an attempt to extract a number of the system
parameters of the triple. We discuss the limitations of the information that
can be inferred from these O-C curves without further supplemental input, e.g.,
ground-based spectroscopy. Based on the limited range of orbital periods for
the triple star systems to which this search is sensitive, we can extrapolate
to estimate that at least 20% of all close binaries have tertiary companions.Comment: 19 pages, 13 figures, 3 tables; ApJ, 2013, 768, 33; corrected Fig. 7,
updated references, minor fixes to tex
A novel scalable hybrid architecture for MMOG
We present a novel MMOG Hybrid P2P architecture and detail its key components, topology and protocols. We highlight the main components which lie at the heart of the proposed solution, and their roles, and describe the methods of tackling the key scenarios which are faced by the architecture during gameplay. For each role, we discuss the interactions that exist between them and describe the protocols that will be used for inter-role communication to perform the atomic actions necessary for maintaining the consistency and responsiveness of an MMOG such as peer addition, peer removal, group transfer, object change persistency and many more. We conclude the chapter with a comparison of the architecture against several existing P2P MMOG frameworks, discussing the differences which exist between them and how the novel Hybrid-P2P architecture we propose aims to address their flaws
The complexities of electronic services implementation and institutionalisation in the public sector
This is the post-print version of the final paper published in Information & Management. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 Elsevier B.V.Electronic service implementation (ESI) in the public sector attempts to improve efficiency, effectiveness, and transparency of governmental departments. Despite having provided the necessary infrastructure and investment, many governments have struggled to realise such aims due to the various forces that challenge implementation and institutionalisation. Using institutional theory as a lens, we explored the forces influencing the implementation and institutionalisation of ESI in the public sector. While our results reinforced previous research in IT implementation and organisational transformation, they showed that the dynamic nature of technology poses unanticipated pressures, and that these can impede the implementation and institutionalisation process
On the nonlinear dynamics of the traveling-wave solutions of the Serre system
We numerically study nonlinear phenomena related to the dynamics of traveling
wave solutions of the Serre equations including the stability, the persistence,
the interactions and the breaking of solitary waves. The numerical method
utilizes a high-order finite-element method with smooth, periodic splines in
space and explicit Runge-Kutta methods in time. Other forms of solutions such
as cnoidal waves and dispersive shock waves are also considered. The
differences between solutions of the Serre equations and the Euler equations
are also studied.Comment: 28 pages, 20 figures, 3 tables, 33 references. Other author's papers
can be downloaded at http://www.denys-dutykh.com
The Size and Shape of Local Voids
We study the size and shape of low density regions in the local universe
which we identify in the smoothed density field of the PSCz flux limited IRAS
galaxy catalogue. After quantifying the systematic biases that enter in the
detection of voids using our data set and method, we identify, using a
smoothing length of 5 Mpc, 14 voids within 80 Mpc and using a
smoothing length of 10 Mpc, 8 voids within 130 Mpc. We study
the void size distribution and morphologies and find that there is roughly an
equal number of prolate and oblate-like spheroidal voids. We compare the
measured PSCz void shape and size distributions with those expected in six
different CDM models and find that only the size distribution can discriminate
between models. The models preferred by the PSCz data are those with
intermediate values of , independent of cosmology.Comment: final version, Accepted in MNRA
Cartilage degeneration in the human patellae and its relationship to the mineralisation of the underlying bone
Generating a Novel Scene-Graph for a Modern GIS Rendering Framework
Within this paper we discuss and present a novel modern 3D Geographical Information System (GIS) framework Project-Vision-Support (PVS). The framework is capable of processing large amounts of geo-spatial data to procedurally extract, extrapolate, and infer properties to create realistic real-world 3D virtual urban environments. The paper focuses on the generation of a novel scene-graph structure used in a number of algorithms and novel procedures for the increased rendering speeds of large virtual scenes and the increased processing capabilities as well as ease of use to manipulate a worlds worth of data. The scene-graph structure, made of two sections, depicts the spatial boundaries of the UKs Ordnance Survey (OS) scheme down to 1km2. Each 1km2 node contains the second section of the scene-graph structure, generated from the OpenStreetMap (OSM) classifications; involving buildings, highways, amenities, boundaries, and terrain. Leaf nodes contain the model mesh data. Generation of the spatial scene-graph for the UK takes 7.99 seconds for 6,313,150 nodes. The scene-graph structure allows for fast dispersal of render states, as well as scene manipulation by pre-categorising the data into branches of the scene-graph structure. Searching a node by name is evaluated using depth-first-search and breadth-first-search giving 0.000186 and 0.036914 seconds respectively within a scene-graph of 3257 nodes
Networking Middleware and Online-Deployment Mechanisms for Java-Based Games
Currently, web-based online gaming applications are predominately utilising Adobe Flash or Java Applets as their core technologies. These games are often casual, two-dimensional games and do not utilise the specialist graphics hardware which has proliferated across modern PCs and Consoles. Multi-user online game play in these titles is often either non-existent or extremely limited. Computer games applications which grace the current generation of consoles and personal computers are designed to utilise the increasingly impressive hardware power at their disposal. However, these are commonly distributed using a physical medium or deployed through custom, proprietary networking mechanisms and rely upon platform-specific networking APIs to facilitate multi-user online game play. In order to unify the concepts of these disparate styles of gaming, this paper presents two interconnected systems which are implemented using Java Web Start and JXTA P2P technologies, providing a platform-independent framework capable of deploying hardware accelerated cross-platform, cross-browser online-enabled Java games, as part of the Homura Project
Pion-proton scattering and isospin breaking in the system
We determine the mass and width of the resonance
from data on scattering both, in the pole of the
-matrix and conventional Breit-Wigner approaches to the scattering
amplitude. We provide a simple formula that relates the two definitions for the
parameters of the . Isospin symmetry breaking in the \d0-\dm system
depends on the definition of the resonant properties: we find in
the pole approach while $\wt{M}_0-\wt{M}_{++} = 2.25 \pm 0.68\ {\rm MeV},\
\wt{\Gamma}_0 - \wt{\Gamma}_{++} = 8.45 \pm 1.11\ {\rm MeV}$ in the
conventional approach.Comment: Latex, 23 pages, two figures upon reques
- …