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BACK TO KINSHIP III: A GENERAL INTRODUCTION
Back to Kinship III is the third Special Issue of the e-journal, Structure and Dynamics sponsored by the group, Kinship Circle. Each issue is dedicated to current kinship research.There are 5 articles in this Special Issue, covering a wide range of kinship research questions and topics The first two articles, by William Young and Warren Shapiro, respectively, employ ethnographic evidence as the reason for revising previous kinship ideas. The next two articles, by Robert Parkin and Dwight Read, respectively, focus on kinship terminology and revisit theoretical issues. The last article, by Alain Matthey de lâEtang, discusses theorizing by Dwight Read challenging the âreceived viewâ of kin terms being derived through a genealogical framework and proposing, in its place, that kin terms are structurally organized through a generative logic for the terminolog
Multi-element cylindrical electrostatic lens systems for focusing and controlling charged particles
This paper describes theoretical modelling of electrostatic lenses based on
3, 4 and 5 closely spaced cylindrical electrodes, respectively. In each case,
modelling is carried out numerically using commercial packages SIMION and
LENSYS, and a variety of performance parameters are obtained. These include the
magnification, the 3rd order spherical and chromatic aberration coefficients.
Special cases such as zoom lens (i.e., lenses whose magnification may be
changed without losing focus) are considered. Results are obtained as a
function of the ratios of the electrode lengths and gaps, and as a function of
ratios of the controlling voltages.
As a result, it is shown that how a multi-element lens system can be operated
with the whole focal properties in a useful mode for using in experimental
studies.Comment: 20 pages, 15 figure
Halo heating from fluctuating gas in a model dwarf
The cold dark matter (CDM) structure formation scenario faces challenges on
(sub)galactic scales, central among them being the `cusp-core' problem. A known
remedy, driving CDM out of galactic centres, invokes interactions with baryons,
through fluctuations in the gravitational potential arising from feedback or
orbiting clumps of gas or stars. Here we interpret core formation in a
hydrodynamic simulation in terms of a theoretical formulation, which may be
considered a generalisation of Chandrasekhar's theory of two body relaxation to
the case when the density fluctuations do not arise from white noise; it
presents a simple characterisation of the effects of complex hydrodynamics and
`subgrid physics'. The power spectrum of gaseous fluctuations is found to
follow a power law over a range of scales, appropriate for a fully turbulent
compressible medium. The potential fluctuations leading to core formation are
nearly normally distributed, which allows for the energy transfer leading to
core formation to be described as a standard diffusion process, initially
increasing the velocity dispersion of test particles as in Chandrasekhar's
theory. We calculate the energy transfer from the fluctuating gas to the halo
and find it consistent with theoretical expectations. We also examine how the
initial kinetic energy input to halo particles is redistributed to form a core.
The temporal mass decrease inside the forming core may be fit by an exponential
form; a simple prescription based on our model associates the characteristic
timescale with an energy relaxation time. We compare the resulting theoretical
density distribution with that in the simulation.Comment: 15 pages, 17 figures. Comments welcome
Does the Fornax dwarf spheroidal have a central cusp or core?
The dark matter dominated Fornax dwarf spheroidal has five globular clusters
orbiting at ~1 kpc from its centre. In a cuspy CDM halo the globulars would
sink to the centre from their current positions within a few Gyrs, presenting a
puzzle as to why they survive undigested at the present epoch. We show that a
solution to this timing problem is to adopt a cored dark matter halo. We use
numerical simulations and analytic calculations to show that, under these
conditions, the sinking time becomes many Hubble times; the globulars
effectively stall at the dark matter core radius. We conclude that the Fornax
dwarf spheroidal has a shallow inner density profile with a core radius
constrained by the observed positions of its globular clusters. If the phase
space density of the core is primordial then it implies a warm dark matter
particle and gives an upper limit to its mass of ~0.5 keV, consistent with that
required to significantly alleviate the substructure problem.Comment: 6 pages, 5 figures, accepted for publication in MNRAS, high
resolution simulations include
Effective action for strongly correlated electron systems
The su(2|1) coherent-state path-integral representation of the partition
function of the t - J model of strongly correlated electrons is derived at
finite doping. The emergent effective action is compared to the one proposed
earlier on phenomenological grounds by Shankar to describe holes in an
antiferromagnet (Nucl.Phys. B330 (1990) 433). The t - J model effective action
is found to have an important "extra" factor with no analogue in Shankar's
action. It represents the local constraint of no double electron occupancy and
reflects the rearrangement of the underlying phase-space manifold due to the
presence of strong electron correlation. This important ingredient is shown to
be essential to describe the physics of strongly correlated electron systems.
Keywords: t - J model of strongly correlated electrons; su(2|1)
coherent-state path integralComment: 22 page
How supernova feedback turns dark matter cusps into cores
We propose and successfully test against new cosmological simulations a novel
analytical description of the physical processes associated with the origin of
cored dark matter density profiles. In the simulations, the potential in the
central kiloparsec changes on sub-dynamical timescales over the redshift
interval 4 > z > 2 as repeated, energetic feedback generates large underdense
bubbles of expanding gas from centrally-concentrated bursts of star formation.
The model demonstrates how fluctuations in the central potential irreversibly
transfer energy into collisionless particles, thus generating a dark matter
core. A supply of gas undergoing collapse and rapid expansion is therefore the
essential ingredient. The framework, based on a novel impulsive approximation,
breaks with the reliance on adiabatic approximations which are inappropriate in
the rapidly-changing limit. It shows that both outflows and galactic fountains
can give rise to cusp-flattening, even when only a few per cent of the baryons
form stars. Dwarf galaxies maintain their core to the present time. The model
suggests that constant density dark matter cores will be generated in systems
of a wide mass range if central starbursts or AGN phases are sufficiently
frequent and energetic.Comment: 9 pages, 6 figures, accepted by MNRAS. No change in results. Expanded
discussion and more reference
The effects of baryon physics, black holes and AGN feedback on the mass distribution in clusters of galaxies
The spatial distribution of matter in clusters of galaxies is mainly
determined by the dominant dark matter component, however, physical processes
involving baryonic matter are able to modify it significantly. We analyse a set
of 500 pc resolution cosmological simulations of a cluster of galaxies with
mass comparable to Virgo, performed with the AMR code RAMSES. We compare the
mass density profiles of the dark, stellar and gaseous matter components of the
cluster that result from different assumptions for the subgrid baryonic physics
and galaxy formation processes. First, the prediction of a gravity only N-body
simulation is compared to that of a hydrodynamical simulation with standard
galaxy formation recipes, then all results are compared to a hydrodynamical
simulation which includes thermal AGN feedback from Super Massive Black Holes
(SMBH). We find the usual effects of overcooling and adiabatic contraction in
the run with standard galaxy formation physics, but very different results are
found when implementing SMBHs and AGN feedback. Star formation is strongly
quenched, producing lower stellar densities throughout the cluster, and much
less cold gas is available for star formation at low redshifts. At redshift z =
0 we find a flat density core of radius 10 kpc in both of the dark and stellar
matter density profiles. We specu- late on the possible formation mechanisms
able to produce such cores and we conclude that they can be produced through
the coupling of different processes: (I) dynamical friction from the decay of
black hole orbits during galaxy mergers; (II) AGN driven gas outflows producing
fluctuations of the gravitational potential causing the removal of
collisionless matter from the central region of the cluster; (III) adiabatic
expansion in response to the slow expulsion of gas from the central region of
the cluster during the quiescent mode of AGN activity.Comment: Published on MNRAS - 13 pages, 4 tables, 9 figure
Formation and evolution of dwarf galaxies in the CDM Universe
We first review the results of the tidal stirring model for the
transformation of gas-rich dwarf irregulars into dwarf spheroidals, which turns
rotationally supported stellar systems into pressure supported ones. We
emphasize the importance of the combined effect of ram pressure stripping and
heating from the cosmic ultraviolet background in removing the gas and
converting the object into a gas poor system as dSphs. We discuss how the
timing of infall of dwarfs into the primary halo determines the final
mass-to-light ratio and star formation history. Secondly we review the results
of recent cosmological simulations of the formation of gas-rich dwarfs. These
simulations are finally capable to produce a realistic object with no bulge, an
exponential profile and a slowly rising rotation curve. The result owes to the
inclusion of an inhomogeneous ISM and a star formation scheme based on regions
having the typical density of molecular cloud complexes. Supernovae-driven
winds become more effective in such mode, driving low angular momentum baryons
outside the virial radius at high redshift and turning the dark matter cusp
into a core. Finally we show the first tidal stirring experiments adopting
dwarfs formed in cosmological simulations as initial conditions. The latter are
gas dominated and have have turbulent thick gaseous and stellar disks disks
that cannot develop strong bars, yet they are efficiently heated into spheroids
by tidal shocks.Comment: 14 pages, 4 Figures, o appear in the proceedings of the CRAL
conference, Lyon, June 2010, "A Universe of Dwarf Galaxies", eds. Philippe
Prugniel & Mina Koleva; EDP Sciences in the European Astronomical Society
Publications Series. (invited talk
Collisional dark matter density profiles around supermassive black holes
We solve the spherically symmetric time dependent relativistic Euler
equations on a Schwarzschild background space-time for a perfect fluid, where
the perfect fluid models the dark matter and the space-time background is that
of a non-rotating supermassive black hole. We consider the fluid obeys an ideal
gas equation of state as a simple model of dark matter with pressure. Assuming
out of equilibrium initial conditions we search for late-time attractor type of
solutions, which we found to show a constant accretion rate for the non-zero
pressure case, that is, the pressure itself suffices to produce stationary
accretion regimes. We then analyze the resulting density profile of such
late-time solutions with the function . For different values of
the adiabatic index we find different slopes of the density profile, and we
study such profile in two regions: a region one near the black hole, located
from the horizon up to 50 and a region two from up to , which for a black hole of corresponds to pc. The profile depends on the adiabatic index or equivalently on the
pressure of the fluid and our findings are as follows: in the near region the
density profile shows values of and in the limit of the
pressure-less case ; on the other hand, in region two,
the value of in all the cases we studied. If these results are to
be applied to the dark matter problem, the conclusion is that, in the limit of
pressure-less gas the density profile is cuspy only near the black hole and
approaches a non-cuspy profile at bigger scales within 1pc. These results show
on the one hand that pressure suffices to provide flat density profiles of dark
matter and on the other hand show that the presence of a central black hole
does not distort the density profile of dark matter at scales of 0.1pc.Comment: 7 pages, 8 eps figures, accepted for publication in MNRA
Photon echo studies of photosynthetic light harvesting
The broad linewidths in absorption spectra of photosynthetic complexes obscure information related to their structure and function. Photon echo techniques represent a powerful class of time-resolved electronic spectroscopy that allow researchers to probe the interactions normally hidden under broad linewidths with sufficient time resolution to follow the fastest energy transfer events in light harvesting. Here, we outline the technical approach and applications of two types of photon echo experiments: the photon echo peak shift and two-dimensional (2D) Fourier transform photon echo spectroscopy. We review several extensions of these techniques to photosynthetic complexes. Photon echo peak shift spectroscopy can be used to determine the strength of coupling between a pigment and its surrounding environment including neighboring pigments and to quantify timescales of energy transfer. Two-dimensional spectroscopy yields a frequency-resolved map of absorption and emission processes, allowing coupling interactions and energy transfer pathways to be viewed directly. Furthermore, 2D spectroscopy reveals structural information such as the relative orientations of coupled transitions. Both classes of experiments can be used to probe the quantum mechanical nature of photosynthetic light-harvesting: peak shift experiments allow quantification of correlated energetic fluctuations between pigments, while 2D techniques measure quantum beating directly, both of which indicate the extent of quantum coherence over multiple pigment sites in the protein complex. The mechanistic and structural information obtained by these techniques reveals valuable insights into the design principles of photosynthetic light-harvesting complexes, and a multitude of variations on the methods outlined here
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