11,650 research outputs found
HI Epoch of Reionization Arrays
There are few data available with which to constrain the thermal history of
the intergalactic medium (IGM) following global recombination. Thus far, most
constraints flow from analyses of the Cosmic Microwave Background and optical
spectroscopy along a few lines of sight. However, direct study of the IGM in
emission or absorption against the CMB via the 1S hyperfine transition of
Hydrogen would enable broad characterization thermal history and source
populations. New generations of radio arrays are in development to measure this
line signature. Bright foreground emission and the complexity of instrument
calibration models are significant hurdles. How to optimize these is uncertain,
resulting in a diversity in approaches. We discuss recent limits on line
brightness, array efforts including the new Large Aperture Experiment to Detect
the Dark Ages (LEDA), and the next generation Hydrogen Reionization Array
(HERA) concept.Comment: 8 pages, 4 figures, 1 table. Invited review to the 11th Asian-Pacific
Regional IAU Meeting 2011, NARIT Conference Series, Vol. 1 eds. S.
Komonjinda, Y. Kovalev, and D. Ruffolo (2012
Isochores Merit the Prefix 'Iso'
The isochore concept in human genome sequence was challenged in an analysis
by the International Human Genome Sequencing Consortium (IHGSC). We argue here
that a statement in IGHSC analysis concerning the existence of isochore is
incorrect, because it had applied an inappropriate statistical test. To test
the existence of isochores should be equivalent to a test of homogeneity of
windowed GC%. The statistical test applied in the IHGSC's analysis, the
binomial test, is however a test of a sequence being random on the base level.
For testing the existence of isochore, or homogeneity in GC%, we propose to use
another statistical test: the analysis of variance (ANOVA). It can be shown
that DNA sequences that are rejected by binomial test may not be rejected by
the ANOVA test.Comment: 14 pages (including 1 figure), submitte
Sum rules of codon usage probabilities
In the crystal basis model of the genetic code, it is deduced that the sum of
usage probabilities of the codons with C and A in the third position for the
quartets and/or sextets is independent of the biological species for
vertebrates. A comparison with experimental data shows that the prediction is
satisfied within about 5 %.Comment: 7 page
A Statistical Semi-Empirical Model: Satellite galaxies in Groups and Clusters
We present STEEL a STatistical sEmi-Empirical modeL designed to probe the
distribution of satellite galaxies in groups and clusters. Our fast statistical
methodology relies on tracing the abundances of central and satellite haloes
via their mass functions at all cosmic epochs with virtually no limitation on
cosmic volume and mass resolution. From mean halo accretion histories and
subhalo mass functions the satellite mass function is progressively built in
time via abundance matching techniques constrained by number densities of
centrals in the local Universe. By enforcing dynamical merging timescales as
predicted by high-resolution N-body simulations, we obtain satellite
distributions as a function of stellar mass and halo mass consistent with
current data. We show that stellar stripping, star formation, and quenching
play all a secondary role in setting the number densities of massive satellites
above . We further show that observed
star formation rates used in our empirical model over predict low-mass
satellites below , whereas, star
formation rates derived from a continuity equation approach yield the correct
abundances similar to previous results for centrals.Comment: 21 pages, 17 Figures. MNRAS, in pres
A new estimate on Evans' Weak KAM approach
We consider a recent formulation of weak KAM theory proposed by Evans. As
well as for classical integrability, for one dimensional mechanical Hamiltonian
systems all the computations can be explicitly done. This allows us on the one
hand to illustrate the geometric content of the theory, on the other hand to
prove new lower bounds which extend also to the generic n degrees of freedom
case
Critical exponents in Ising spin glasses
We determine accurate values of ordering temperatures and critical exponents
for Ising Spin Glass transitions in dimension 4, using a combination of finite
size scaling and non-equilibrium scaling techniques. We find that the exponents
and vary with the form of the interaction distribution, indicating
non-universality at Ising spin glass transitions. These results confirm
conclusions drawn from numerical data for dimension 3.Comment: 6 pages, RevTeX (or Latex, etc), 10 figures, Submitted to PR
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