773 research outputs found
Network of Earthquakes and Recurrences Therein
We quantify the correlation between earthquakes and use the same to
distinguish between relevant causally connected earthquakes. Our correlation
metric is a variation on the one introduced by Baiesi and Paczuski (2004). A
network of earthquakes is constructed, which is time ordered and with links
between the more correlated ones. Data pertaining to the California region has
been used in the study. Recurrences to earthquakes are identified employing
correlation thresholds to demarcate the most meaningful ones in each cluster.
The distribution of recurrence lengths and recurrence times are analyzed
subsequently to extract information about the complex dynamics. We find that
the unimodal feature of recurrence lengths helps to associate typical rupture
lengths with different magnitude earthquakes. The out-degree of the network
shows a hub structure rooted on the large magnitude earthquakes. In-degree
distribution is seen to be dependent on the density of events in the
neighborhood. Power laws are also obtained with recurrence time distribution
agreeing with the Omori law.Comment: 17 pages, 5 figure
Comment on "1/f noise in the Bak-Sneppen model"
Contrary to the recently published results by Daerden and Vanderzande [Phys.
Rev. E 53, 4723 (1996)], we show that the time correlation function in the
random-neighbor version of the Bak-Sneppen model can be well approximated by an
exponential giving rise to a 1/f2 power spectrum.Comment: 2 pages, 2 figure
Attractor and Basin Entropies of Random Boolean Networks Under Asynchronous Stochastic Update
We introduce a numerical method to study random Boolean networks with
asynchronous stochas- tic update. Each node in the network of states starts
with equal occupation probability and this probability distribution then
evolves to a steady state. Nodes left with finite occupation probability
determine the attractors and the sizes of their basins. As for synchronous
update, the basin entropy grows with system size only for critical networks,
where the distribution of attractor lengths is a power law. We determine
analytically the distribution for the number of attractors and basin sizes for
frozen networks with connectivity K = 1.Comment: 5 pages, 3 figures, in submissio
Anmeldelse af Daren Kemp & James R. Lewis (red.), Handbook of New Age (2007) og Murphy Pizza & James R. Lewis (red.), Handbook of Contemporary Paganism (2009)
Modernity (Religion and Modernity
Anmeldelse af Carole M. Cusack, Invented Religions: Imagination, Fiction and Faith (2010)
Modernity (Religion and Modernity
Jediism: a convergence of Star Wars fan culture and salad bar spirituality
Modernity (Religion and Modernity
Book review of Carole M. Cusack, Invented Religions: Imagination, Fiction and Faith (2010)
Modernity (Religion and Modernity
Far-UV Observations of NGC 4151 during the ORFEUS-SPAS II Mission
We observed the Seyfert 1 galaxy NGC 4151 on eleven occasions at 1-2 day
intervals using the Berkeley spectrometer during the ORFEUS-SPAS II mission in
1996 November. The mean spectrum covers 912-1220 A at ~0.3 A resolution with a
total exposure of 15,658 seconds. The mean flux at 1000 A was 4.7e-13
erg/cm^2/s/A. We identify the neutral hydrogen absorption with a number of
components that correspond to the velocity distribution of \ion{H}{1} seen in
our own Galaxy as well as features identified in the CIV 1549 absorption
profile by Weymann et al. The main component of neutral hydrogen in NGC 4151
has a total column density of log N_HI = 18.7 +/- 1.5 cm^{-2} for a Doppler
parameter b=250 +/- 50 km/s, and it covers 84 +/- 6% of the source. This is
consistent with previous results obtained with the Hopkins Ultraviolet
Telescope. Other intrinsic far-UV absorption features are not resolved, but the
CIII* 1176 absorption line has a significantly higher blueshift relative to NGC
4151 than the CIII 977 resonance line. This implies that the highest velocity
region of the outflowing gas has the highest density. Variations in the
equivalent width of the CIII* 1176 absorption line anticorrelate with continuum
variations on timescales of days. For an ionization timescale <1 day, we set an
upper limit of 25 pc on the distance of the absorbing gas from the central
source. The OVI 1034 and HeII 1085 emission lines also vary on timescales of
1-2 days, but their response to the continuum variations is complex. For some
continuum variations they show no response, while for others the response is
instantaneous to the limit of our sampling interval.Comment: 4 pages, 2 PostScript figures, uses emulateapj.sty, apjfonts.sty. To
appear in the Astrophysical Journal (Letters) special issue for ORFEU
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