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