20,853 research outputs found
Turbulence and turbulent mixing in natural fluids
Turbulence and turbulent mixing in natural fluids begins with big bang
turbulence powered by spinning combustible combinations of Planck particles and
Planck antiparticles. Particle prograde accretions on a spinning pair releases
42% of the particle rest mass energy to produce more fuel for turbulent
combustion. Negative viscous stresses and negative turbulence stresses work
against gravity, extracting mass-energy and space-time from the vacuum.
Turbulence mixes cooling temperatures until strong-force viscous stresses
freeze out turbulent mixing patterns as the first fossil turbulence. Cosmic
microwave background temperature anisotropies show big bang turbulence fossils
along with fossils of weak plasma turbulence triggered as plasma photon-viscous
forces permit gravitational fragmentation on supercluster to galaxy mass
scales. Turbulent morphologies and viscous-turbulent lengths appear as linear
gas-proto-galaxy-clusters in the Hubble ultra-deep-field at z~7. Proto-galaxies
fragment into Jeans-mass-clumps of primordial-gas-planets at decoupling: the
dark matter of galaxies. Shortly after the plasma to gas transition,
planet-mergers produce stars that explode on overfeeding to fertilize and
distribute the first life.Comment: 23 pages 12 figures, Turbulent Mixing and Beyond 2009 International
Center for Theoretical Physics conference, Trieste, Italy. Revision according
to Referee comments. Accepted for Physica Scripta Topical Issue to be
published in 201
Evolution of primordial planets in relation to the cosmological origin of life
We explore the conditions prevailing in primordial planets in the framework
of the HGD cosmologies as discussed by Gibson and Schild. The initial stages of
condensation of planet-mass H-4He gas clouds in trillion-planet clumps is set
at 300,000 yr (0.3My) following the onset of plasma instabilities when ambient
temperatures were >1000K. Eventual collapse of the planet-cloud into a solid
structure takes place against the background of an expanding universe with
declining ambient temperatures. Stars form from planet mergers within the
clumps and die by supernovae on overeating of planets. For planets produced by
stars, isothermal free fall collapse occurs initially via quasi equilibrium
polytropes until opacity sets in due to molecule and dust formation. The
contracting cooling cloud is a venue for molecule formation and the sequential
condensation of solid particles, starting from mineral grains at high
temperatures to ice particles at lower temperatures, water-ice becomes
thermodynamically stable between 7 and 15 My after the initial onset of
collapse, and contraction to form a solid icy core begins shortly thereafter.
Primordial-clump-planets are separated by ~ 1000 AU, reflecting the high
density of the universe at 30,000 yr. Exchanges of materials, organic molecules
and evolving templates readily occur, providing optimal conditions for an
initial origin of life in hot primordial gas planet water cores when adequately
fertilized by stardust. The condensation of solid molecular hydrogen as an
extended outer crust takes place much later in the collapse history of the
protoplanet. When the object has shrunk to several times the radius of Jupiter,
the hydrogen partial pressure exceeds the saturation vapour pressure of solid
hydrogen at the ambient temperature and condensation occurs.Comment: 14 pages 7 figures SPIE Conference 7819 Instruments, Methods, and
Missions for Astrobiology XIII Proceedings, Aug 3-5, 2010, San Diego, Ed.
Richard B. Hoove
Why don't clumps of cirrus dust gravitationally collapse?
We consider the Herschel-Planck infrared observations of presumed
condensations of interstellar material at a measured temperature of
approximately 14 K (Juvela et al., 2012), the triple point temperature of
hydrogen. The standard picture is challenged that the material is cirrus-like
clouds of ceramic dust responsible for Halo extinction of cosmological sources
(Finkbeiner, Davis, and Schlegel 1999). Why would such dust clouds not collapse
gravitationally to a point on a gravitational free-fall time scale of
years? Why do the particles not collide and stick together, as is fundamental
to the theory of planet formation (Blum 2004; Blum and Wurm, 2008) in pre-solar
accretion discs? Evidence from 3.3 m and UIB emissions as well as ERE
(extended red emission) data point to the dominance of PAH-type macromolecules
for cirrus dust, but such fractal dust will not spin in the manner of rigid
grains (Draine & Lazarian, 1998). IRAS dust clouds examined by Herschel-Planck
are easily understood as dark matter Proto-Globular-star-Cluster (PGC) clumps
of primordial gas planets, as predicted by Gibson (1996) and observed by Schild
(1996).Comment: 8 pages, 2 figures, Conference FQMT'1
Gravitational hydrodynamics of large scale structure formation
The gravitational hydrodynamics of the primordial plasma with neutrino hot
dark matter is considered as a challenge to the bottom-up cold dark matter
paradigm. Viscosity and turbulence induce a top-down fragmentation scenario
before and at decoupling. The first step is the creation of voids in the
plasma, which expand to 37 Mpc on the average now. The remaining matter clumps
turn into galaxy clusters. Turbulence produced at expanding void boundaries
causes a linear morphology of 3 kpc fragmenting protogalaxies along vortex
lines. At decoupling galaxies and proto-globular star clusters arise; the
latter constitute the galactic dark matter halos and consist themselves of
earth-mass H-He planets. Frozen planets are observed in microlensing and
white-dwarf-heated ones in planetary nebulae. The approach also explains the
Tully-Fisher and Faber-Jackson relations, and cosmic microwave temperature
fluctuations of micro-Kelvins.Comment: 6 pages, no figure
Regaining the FORS: optical ground-based transmission spectroscopy of the exoplanet WASP-19b with VLT+FORS2
In the past few years, the study of exoplanets has evolved from being pure
discovery, then being more exploratory in nature and finally becoming very
quantitative. In particular, transmission spectroscopy now allows the study of
exoplanetary atmospheres. Such studies rely heavily on space-based or large
ground-based facilities, because one needs to perform time-resolved, high
signal-to-noise spectroscopy. The very recent exchange of the prisms of the
FORS2 atmospheric diffraction corrector on ESO's Very Large Telescope should
allow us to reach higher data quality than was ever possible before. With
FORS2, we have obtained the first optical ground-based transmission spectrum of
WASP-19b, with 20 nm resolution in the 550--830 nm range. For this planet, the
data set represents the highest resolution transmission spectrum obtained to
date. We detect large deviations from planetary atmospheric models in the
transmission spectrum redwards of 790 nm, indicating either additional sources
of opacity not included in the current atmospheric models for WASP-19b or
additional, unexplored sources of systematics. Nonetheless, this work shows the
new potential of FORS2 for studying the atmospheres of exoplanets in greater
detail than has been possible so far.Comment: 7 pages, 9 figures, 3 tables. Accepted for publication in A&
The history of stellar metallicity in a simulated disc galaxy
We explore the chemical distribution of stars in a simulated galaxy. Using simulations of the same initial conditions but with two different feedback schemes (McMaster Unbiased Galaxy Simulations – MUGS – and Making Galaxies in a Cosmological Context – MaGICC), we examine the features of the age–metallicity relation (AMR), and the three-dimensional age– [Fe/H]–[O/Fe] distribution, both for the galaxy as a whole and decomposed into disc, bulge, halo and satellites. The MUGS simulation, which uses traditional supernova feedback, is replete with chemical substructure. This substructure is absent from the MaGICC simulation, which includes early feedback from stellar winds, a modified initial mass function and more efficient feedback. The reduced amount of substructure is due to the almost complete lack of satellites in MaGICC. We identify a significant separation between the bulge and disc AMRs, where the bulge is considerably more metal-rich with a smaller spread in metallicity at any given time than the disc. Our results suggest, however, that identifying the substructure in observations will require exquisite age resolution, of the order of 0.25 Gyr. Certain satellites show exotic features in the AMR, even forming a ‘sawtooth’ shape of increasing metallicity followed by sharp declines which correspond to pericentric passages. This fact, along with the large spread in stellar age at a given metallicity, compromises the use of metallicity as an age indicator, although alpha abundance provides a more robust clock at early times. This may also impact algorithms that are used to reconstruct star formation histories from resolved stellar populations, which frequently assume a monotonically increasing AMR
Rim curvature anomaly in thin conical sheets revisited
This paper revisits one of the puzzling behaviors in a developable cone
(d-cone), the shape obtained by pushing a thin sheet into a circular container
of radius by a distance [E. Cerda, S. Chaieb, F. Melo, and L.
Mahadevan, {\sl Nature} {\bf 401}, 46 (1999)]. The mean curvature was reported
to vanish at the rim where the d-cone is supported [T. Liang and T. A. Witten,
{\sl Phys. Rev. E} {\bf 73}, 046604 (2006)]. We investigate the ratio of the
two principal curvatures versus sheet thickness over a wider dynamic range
than was used previously, holding and fixed. Instead of tending
towards 1 as suggested by previous work, the ratio scales as .
Thus the mean curvature does not vanish for very thin sheets as previously
claimed. Moreover, we find that the normalized rim profile of radial curvature
in a d-cone is identical to that in a "c-cone" which is made by pushing a
regular cone into a circular container. In both c-cones and d-cones, the ratio
of the principal curvatures at the rim scales as ,
where is the pushing force and is the Young's modulus. Scaling
arguments and analytical solutions confirm the numerical results.Comment: 25 pages, 12 figures. Added references. Corrected typos. Results
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