3,113 research outputs found
Precise time and frequency intercomparison between NPL, India and PTB, Federal Republic of Germany via satellite symphonie-1
A time and frequency intercomparison experiment conducted using Earth stations in New Delhi, India and Raisting, FRG is described. The NPL clock was placed at New Delhi Earth Station and the Raisting Clock was calibrated with PTB/Primary standard via LORAN-C and travelling clocks. The random uncertainity of time comparisons, represented by two sample Allan Variance sigma (30 seconds), was less than 10 nanoseconds. The relative frequency difference between the NPL and Raisting Clocks, SNPL, RAIS, as measured over the 44 days period was found to be -15.7 x 10 to the -13th power. The relative frequency difference between PTB Primary Standard and Raisting Clock, SPTB, RAIS, during this period, was measured to be -22.8 x 10 to the -13th power. The relative frequency difference between NPL clock and PTB Primary Standard, SNPL, PTB, thus, is +7.1 x 10 to the -13th power. The clock rate (UTC, India) of +7.1 + or - 0.5 x 10 to the -13th power, agrees well with that obtained via VLF phase measurements over one year period and with USNO travelling clock time comparisons made in September, 1980
Is the `IR Coincidence' Just That?
(Abridged) Motch (1985) suggested that in the hard state of GX 339-4 the soft
X-ray power-law extrapolated backward in energy agrees with the IR flux. Corbel
& Fender (2002) showed that the hard state radio power-law extrapolated forward
in energy meets the extrapolated X-ray power-law at an IR break, which was
explicitly observed twice in GX 339-4. This `IR coincidence' has been cited as
further evidence that a jet might make a significant contribution to the X-rays
in hard state systems. We explore this hypothesis with a series of simultaneous
radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002
hard states. We fit these spectra, in detector space, with a simple, but
remarkably successful, doubly broken power-law that requires an IR spectral
break. For these observations, the break position and the integrated radio/IR
flux have stronger dependences upon the X-rays than the simplest jet
predictions. If one allows for a softening of the X-ray power law with
increasing flux, then the jet model agrees with the correlation. We also find
evidence that the radio/X-ray fcorrelation previously observed in GX 339-4
shows a `parallel track' for the 2002 hard state. The slope of the 2002
correlation is consistent with prior observations; however, the radio amplitude
is reduced. We then examine the correlation in Cyg X-1 through the use of radio
data, obtained with the Ryle radio telescope, and RXTE data, from the ASM and
pointed observations. We again find evidence of `parallel tracks', and here
they are associated with `failed transitions' to the soft state. We also find
that for Cyg X-1 the radio flux is more fundamentally correlated with the hard
X-ray flux.Comment: To Appear in the July 2005 Astrophysical Journal; 9 Pages, uses
emulateapj.st
Trapping in complex networks
We investigate the trapping problem in Erdos-Renyi (ER) and Scale-Free (SF)
networks. We calculate the evolution of the particle density of
random walkers in the presence of one or multiple traps with concentration .
We show using theory and simulations that in ER networks, while for short times
, for longer times exhibits a more
complex behavior, with explicit dependence on both the number of traps and the
size of the network. In SF networks we reveal the significant impact of the
trap's location: is drastically different when a trap is placed on a
random node compared to the case of the trap being on the node with the maximum
connectivity. For the latter case we find
\rho(t)\propto\exp\left[-At/N^\frac{\gamma-2}{\gamma-1}\av{k}\right] for all
, where is the exponent of the degree distribution
.Comment: Appendix adde
Evolutionary dynamics on degree-heterogeneous graphs
The evolution of two species with different fitness is investigated on
degree-heterogeneous graphs. The population evolves either by one individual
dying and being replaced by the offspring of a random neighbor (voter model
(VM) dynamics) or by an individual giving birth to an offspring that takes over
a random neighbor node (invasion process (IP) dynamics). The fixation
probability for one species to take over a population of N individuals depends
crucially on the dynamics and on the local environment. Starting with a single
fitter mutant at a node of degree k, the fixation probability is proportional
to k for VM dynamics and to 1/k for IP dynamics.Comment: 4 pages, 4 figures, 2 column revtex4 format. Revisions in response to
referee comments for publication in PRL. The version on arxiv.org has one
more figure than the published PR
An electron paramagnetic resonance study of Pr_{0.6}Ca_{0.4}MnO_{3} across the charge ordering transition
We report the first electron paramagnetic resonance studies of single
crystals and powders of Pr_{0.6}Ca_{0.4}MnO_{3} in the 300-4.2 K range,
covering the charge ordering transition at ~ 240 K and antiferromagnetic
transition (T_N) at ~ 170 K. The asymmetry parameter for the Dysonian single
crystal spectra shows anomalous increase at T_{co}. Below T_{co} the g-value
increases continuously, suggesting a gradual strengthening of orbital ordering.
The linewidth undergoes a sudden increase at T_{co} and continues to increase
down to T_N. The intensity increases as the temperature is decreased till
T_{co} due to the renormalization of magnetic susceptibility arising from the
build up of ferromagnetic correlations. The value of the exchange constant, J,
is estimated to be 154 K.Comment: Uses Revtex3.
Rapidity distribution as a probe for elliptical flow at intermediate energies
Interplay between the spectator and participant matter in heavy-ion
collisions is investigated within isospin dependent quantum molecular dynamics
(IQMD) model in term of rapidity distribution of light charged particles. The
effect of different types and size rapidity distributions is studied in
elliptical flow. The elliptical flow patterns show important role of the nearby
spectator matter on the participant zone. This role is further explained on the
basis of passing time of the spectator and expansion time of the participant
zone. The transition from the in-plane to out-of-plane is observed only when
the mid-rapidity region is included in the rapidity bin, otherwise no
transition occurs. The transition energy is found to be highly sensitive
towards the size of the rapidity bin, while weakly on the type of the rapidity
distribution. The theoretical results are also compared with the experimental
findings and are found in good agreement.Comment: 8 figure
Mean-field analysis of the q-voter model on networks
We present a detailed investigation of the behavior of the nonlinear q-voter
model for opinion dynamics. At the mean-field level we derive analytically, for
any value of the number q of agents involved in the elementary update, the
phase diagram, the exit probability and the consensus time at the transition
point. The mean-field formalism is extended to the case that the interaction
pattern is given by generic heterogeneous networks. We finally discuss the case
of random regular networks and compare analytical results with simulations.Comment: 20 pages, 10 figure
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