72,708 research outputs found
Prospects for Stochastic Background Searches Using Virgo and LSC Interferometers
We consider the question of cross-correlation measurements using Virgo and
the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search
for a stochastic gravitational-wave background. We find that inclusion of Virgo
into the network will substantially improve the sensitivity to correlations
above 200 Hz if all detectors are operating at their design sensitivity. This
is illustrated using a simulated isotropic stochastic background signal,
generated with an astrophysically-motivated spectrum, injected into 24 hours of
simulated noise for the LIGO and Virgo interferometers.Comment: 11 pages, uses IOP style files, submitted to CQG for GWDAW11
proceedings; revised in response to referee comment
Challenges and confusion in media and communication regulation: a four country comparison.
In this chapter we discuss recent developments and challenges in European media and communication policy, focussing on the period since the 2008 global financial crisis. We are especially interested in the implications of the financial crisis and its political repercussions nationally (austerity measures and cuts to public services as well as growing anti-politics sentiments and widespread dissatisfaction with free-market capitalism and representative democracy) for media and communication policy, understood here in a broad sense, so to include all electronic communications, such as the Internet, mobile communications, social media etc. Our overarching concern is with the implications of developments in media and communication policy for the democratic functions of the media in Europe
Toward an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence
Observations of an optical source coincident with gravitational wave emission
detected from a binary neutron star coalescence will improve the confidence of
detection, provide host galaxy localisation, and test models for the
progenitors of short gamma ray bursts. We employ optical observations of three
short gamma ray bursts, 050724, 050709, 051221, to estimate the detection rate
of a coordinated optical and gravitational wave search of neutron star mergers.
Model R-band optical afterglow light curves of these bursts that include a
jet-break are extrapolated for these sources at the sensitivity horizon of an
Advanced LIGO/Virgo network. Using optical sensitivity limits of three
telescopes, namely TAROT (m=18), Zadko (m=21) and an (8-10) meter class
telescope (m=26), we approximate detection rates and cadence times for imaging.
We find a median coincident detection rate of 4 yr^{-1} for the three bursts.
GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic
rate of 13 coincident detections yr^{-1}, and would be detectable by Zadko up
to five days after the trigger. Late time imaging to m=26 could detect off-axis
afterglows for GRB 051221 like bursts several months after the trigger. For a
broad distribution of beaming angles, the optimal strategy for identifying the
optical emissions triggered by gravitational wave detectors is rapid response
searches with robotic telescopes followed by deeper imaging at later times if
an afterglow is not detected within several days of the trigger.Comment: 6 pages, 1 figure, Accepted for publication in MNRAS Letters (2011
April 22
Search for axions in streaming dark matter
A new search strategy for the detection of the elusive dark matter (DM) axion
is proposed. The idea is based on streaming DM axions, whose flux might get
temporally enormously enhanced due to gravitational lensing. This can happen if
the Sun or some planet (including the Moon) is found along the direction of a
DM stream propagating towards the Earth location. The experimental requirements
to the axion haloscope are a wide-band performance combined with a fast axion
rest mass scanning mode, which are feasible. Once both conditions have been
implemented in a haloscope, the axion search can continue parasitically almost
as before. Interestingly, some new DM axion detectors are operating wide-band
by default. In order not to miss the actually unpredictable timing of a
potential short duration signal, a network of co-ordinated axion antennae is
required, preferentially distributed world-wide. The reasoning presented here
for the axions applies to some degree also to any other DM candidates like the
WIMPs.Comment: 5 page
Access to the Internet and Regional Structures: The Case of Italy
I study the effects of Internet access on regional structures and provide some insights into the complex question of the role of technology in regional development. The paper analyzes the distribution of access to the Internet in Italy, highlighting the differences among regions and sub-regional areas and with respect to categories of users. This is an aspect of the so-called \u201cdigital divide\u201d. I concentrate on the stability and change of regional structures in Italy, pointing at conclusions of general relevance. My analysis confirms the dynamism of the regions of the so-called \u201cThird Italy\u201d and the fundamental distinction between the North-Center with respect to the South, the Italian Mezzogiorno. My preliminary conclusions on the effects of the Internet in promoting economic development suggest lines for further investigation.
Key Words: Regional development, Italy, Internet, digital divide
JEL Classifications: R11, R12, O3
Benchmarking and viability assessment of optical packet switching for metro networks
Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained
DEMON: a Proposal for a Satellite-Borne Experiment to study Dark Matter and Dark Energy
We outline a novel satellite mission concept, DEMON, aimed at advancing our
comprehension of both dark matter and dark energy, taking full advantage of two
complementary methods: weak lensing and the statistics of galaxy clusters. We
intend to carry out a 5000 sqdeg combined IR, optical and X-ray survey with
galaxies up to a redshift of z~2 in order to determine the shear correlation
function. We will also find ~100000 galaxy clusters, making it the largest
survey of this type to date. The DEMON spacecraft will comprise one IR/optical
and eight X-ray telescopes, coupled to multiple cameras operating at different
frequency bands. To a great extent, the technology employed has already been
partially tested on ongoing missions, therefore ensuring improved reliability.Comment: 12 pages, 3 figures, accepted for publication in the SPIE conference
proceeding
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