3,505 research outputs found
Image retrieval by hypertext links
This paper presents a model for retrieval of images from a large World Wide Web based collection. Rather than considering complex visual recognition algorithms, the model presented is based on combining evidence of the text content and hypertext structure of the Web. The paper shows that certain types of query are amply served by this form of representation. It also presents a novel means of gathering relevance judgements
Highlights of the Beam Energy Scan from STAR
The first part of the beam energy scan (BES) program at RHIC was successfully
completed in the years 2010 and 2011. First STAR results from particle yield
measurements are in good agreement with previously published data from SPS and
AGS experiments whereas other results like azimuthal HBT and
event-by-event fluctuations differ at some energies. In addition, new
observations like the centrality dependence of chemical freeze-out parameters
( and ) or the smoothly increasing difference with
decreasing energy in the elliptic flow between particles and
corresponding anti-particles, are discussed.Comment: CPOD 2011 proceedings, 5 pages, 4 figure
The Role of Starbursts in the Formation of Galaxies & Active Galactic Nuclei
Starbursts are episodes of intense star-formation in the central regions of
galaxies, and are the sites of roughly 25% of the high-mass star-formation in
the local universe. In this contribution I review the role starbursts play in
the formation and evolution of galaxies, the intergalactic medium, and active
galactic nuclei. Four major conclusions are drawn. 1) Starburst galaxies are
good analogues (in fact, the only plausible local analogues) to the known
population of star-forming galaxies at high-redshift. 2) Integrated over cosmic
time, supernova-driven galactic-winds (`superwinds') play an essential role in
the evolution of galaxies and the inter-galactic medium. 3) Circumnuclear
starbursts are an energetically-significant component of the Seyfert
phenomenon. 4) The evolution of the population of the host galaxies of
radio-quiet quasars is significantly different than that of powerful radio
galaxies, and is at least qualitatively consistent with the standard picture of
the hierarchical assembly of massive galaxies at relatively late times.Comment: 16 pages, 4 figures, Royal Society discussion meeting `The formation
of galaxies
Towards efficient modelling of optical micromanipulation of complex structures
Computational methods for electromagnetic and light scattering can be used
for the calculation of optical forces and torques. Since typical particles that
are optically trapped or manipulated are on the order of the wavelength in
size, approximate methods such as geometric optics or Rayleigh scattering are
inapplicable, and solution or either the Maxwell equations or the vector
Helmholtz equation must be resorted to. Traditionally, such solutions were only
feasible for the simplest geometries; modern computational power enable the
rapid solution of more general--but still simple--geometries such as
axisymmetric, homogeneous, and isotropic scatterers. However, optically-driven
micromachines necessarily require more complex geometries, and their
computational modelling thus remains in the realm of challenging computational
problems. We review our progress towards efficient computational modelling of
optical tweezers and micromanipulation, including the trapping and manipulation
of complex structures such as optical micromachines. In particular, we consider
the exploitation of symmetry in the modelling of such devices.Comment: 5 pages, 4 figure
Roadmap on structured light
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version
Strong Lensing Probabilities in a Cosmological Model with a Running Primordial Power Spectrum
The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP)
data with other finer scale cosmic microwave background (CMB) experiments (CBI
and ACBAR) and two structure formation measurements (2dFGRS and Lyman
forest) suggest a CDM cosmological model with a running spectral power
index of primordial density fluctuations. Motivated by this new result on the
index of primordial power spectrum, we present the first study on the predicted
lensing probabilities of image separation in a spatially flat CDM
model with a running spectral index (RSI-CDM model). It is shown that
the RSI-CDM model suppress the predicted lensing probabilities on
small splitting angles of less than about 4 compared with that of
standard power-law CDM (PL-CDM) model.Comment: 11 pages including 1 figures. Accepted for publication in Modern
Physics Letters A (MPLA), minor revision
Analysis of dynamical tunnelling experiments with a Bose-Einstein condensate
Dynamical tunnelling is a quantum phenomenon where a classically forbidden
process occurs, that is prohibited not by energy but by another constant of
motion. The phenomenon of dynamical tunnelling has been recently observed in a
sodium Bose-Einstein condensate. We present a detailed analysis of these
experiments using numerical solutions of the three dimensional Gross-Pitaevskii
equation and the corresponding Floquet theory. We explore the parameter
dependency of the tunnelling oscillations and we move the quantum system
towards the classical limit in the experimentally accessible regime.Comment: accepted for publication in Physical Review
Age Problem in the Holographic Dark Energy Model
In this note, we test the original holographic dark energy model with some
old high redshift objects. The main idea is very simple: the universe cannot be
younger than its constituents. We find that the original holographic dark
energy model can be ruled out, unless a lower Hubble constant is taken.Comment: 12 pages, 3 tables, 3 figures, revtex4; v2: accepted for publication
in Phys. Rev. D; v3: published versio
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