12,596 research outputs found
Computing A Glimpse of Randomness
A Chaitin Omega number is the halting probability of a universal Chaitin
(self-delimiting Turing) machine. Every Omega number is both computably
enumerable (the limit of a computable, increasing, converging sequence of
rationals) and random (its binary expansion is an algorithmic random sequence).
In particular, every Omega number is strongly non-computable. The aim of this
paper is to describe a procedure, which combines Java programming and
mathematical proofs, for computing the exact values of the first 64 bits of a
Chaitin Omega:
0000001000000100000110001000011010001111110010111011101000010000. Full
description of programs and proofs will be given elsewhere.Comment: 16 pages; Experimental Mathematics (accepted
The Lyman Break Galaxies: their Progenitors and Descendants
We study the evolution of Lyman Break Galaxies (LBGs) from z=5 to z=0 by
tracing the merger trees of galaxies in a large-scale hydrodynamic simulation
based on a Lambda cold dark matter model. In particular, we emphasize on the
range of properties of the sample selected by the rest-frame V band luminosity,
in accordance with recent near-IR observations. The predicted rest-frame V band
luminosity function agrees well with the observed one when dust extinction is
taken into account. The stellar content and the star formation histories of
LBGs are also studied. We find that the LBGs intrinsically brighter than
Mv=-21.0 at z=3 have stellar masses of at least 10^9\Msun, with a median of
10^{10}h^{-1}\Msun. The brightest LBGs (Mv<-23) at z=3 merge into
clusters/groups of galaxies at z=0, as suggested from clustering studies of
LBGs. Roughly one half of the galaxies with -23<Mv<-22 at z=3 fall into
groups/clusters, and the other half become typical L* galaxies at z=0 with
stellar mass of ~10^{11}\Msun. Descendants of LBGs at the present epoch have
formed roughly 30% of their stellar mass by z=3, and the half of their current
stellar population is 10 Gyr old, favoring the scenario that LBGs are the
precursors of the present day spheroids. We find that the most luminous LBGs
have experienced a starburst within 500 Myr prior to z=3, but also have formed
stars continuously over a period of 1 Gyr prior to z=3 when all the star
formation in progenitors is coadded. We also study the evolution of the mean
stellar metallicity distribution of galaxies, and find that the entire
distribution shifts to lower metallicity at higher redshift. The observed
sub-solar metallicity of LBGs at z=3 is naturally predicted in our simulation.Comment: 29 pages, including 11 figures, ApJ in press. One reference adde
Realistic Magnetohydrodynamical Simulation of Solar Local Supergranulation
Three-dimensional numerical simulations of solar surface magnetoconvection
using realistic model physics are conducted. The thermal structure of
convective motions into the upper radiative layers of the photosphere, the main
scales of convective cells and the penetration depths of convection are
investigated. We take part of the solar photosphere with size of 60x60 Mm in
horizontal direction and by depth 20 Mm from level of the visible solar
surface. We use a realistic initial model of the Sun and apply equation of
state and opacities of stellar matter. The equations of fully compressible
radiation magnetohydrodynamics with dynamical viscosity and gravity are solved.
We apply: 1) conservative TVD difference scheme for the magnetohydrodynamics,
2) the diffusion approximation for the radiative transfer, 3) dynamical
viscosity from subgrid scale modeling. In simulation we take uniform
two-dimesional grid in gorizontal plane and nonuniform grid in vertical
direction with number of cells 600x600x204. We use 512 processors with
distributed memory multiprocessors on supercomputer MVS-100k in the Joint
Computational Centre of the Russian Academy of Sciences.Comment: 6 pages, 5 figures, submitted to the proceedings of the GONG 2008 /
SOHO XXI conferenc
U(1) symmetry and elimination of spin-0 gravitons in Horava-Lifshitz gravity without the projectability condition
In this paper, we show that the spin-0 gravitons appearing in Horava-Lifshitz
gravity without the projectability condition can be eliminated by extending the
gauge symmetries of the foliation-preserving diffeomorphisms to include a local
U(1) symmetry. As a result, the problems of stability, ghost, strong coupling,
and different speeds in the gravitational sector are automatically resolved. In
addition, with the detailed balance condition softly breaking, the number of
independent coupling constants can be significantly reduced (from more than 70
down to 15), while the theory is still UV complete and possesses a healthy IR
limit, whereby the prediction powers of the theory are considerably improved.
The strong coupling problem in the matter sector can be cured by introducing an
energy scale , so that , where denotes
the suppression energy of high order derivative terms, and
the would-be strong coupling energy scale.Comment: Revtex4, no figures. Some typos are corrected. Phys. Rev. D84, 101502
(R) (2011
Signals in Single-Event Pion Interferometry for Granular Sources of Quark-Gluon Plasma Droplets
We investigate two-pion Bose-Einstein correlations of quark-gluon plasma
droplet sources in single-event measurements. We find that the distribution of
the fluctuation between correlation functions of the single- and mixed-events
provide useful signals to detect the granular structure of the source.Comment: 6 pages, 6 figures, in LaTe
^{59}Co NMR evidence for charge ordering below T_{CO}\sim 51 K in Na_{0.5}CoO_2
The CoO layers in sodium-cobaltates NaCoO may be viewed as
a spin triangular-lattice doped with charge carriers. The underlying
physics of the cobaltates is very similar to that of the high cuprates.
We will present unequivocal Co NMR evidence that below ,
the insulating ground state of the itinerant antiferromagnet
NaCoO () is induced by charge ordering.Comment: Phys. Rev. Lett. 100 (2008), in press. 4 figure
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