8,390 research outputs found
Chemodynamics of dwarf galaxies under ram-pressure
By implementing a dynamic wind-tunnel model in a smoothed-particle
chemodynamic/hydrodynamic simulation suite, we have investigated the effects of
ram pressure and tidal forces on dwarf galaxies similar to the Magellanic
Clouds, within host galaxies with gas and dark matter halos that are varied, to
compare the relative effects of tides and ram pressure. We concentrate on how
the distributions of metals are affected by interactions. We find that while
ram pressure and tidal forces have some effect on dwarf galaxy outflows, these
effects do not produce large differences in the metal distributions of the
dwarf disks other than truncation in the outer regions in some cases, and that
confinement from the host galaxy gas halo appears to be more significant than
ram pressure stripping. We find that stochastic variations in the star
formation rate can explain the remaining variations in disk metal properties.
This raises questions on the cause of low metallicities in dwarf galaxies.Comment: Submitted to ApJ, under 2nd review (very minor revisions
3D Radiation hydrodynamics of a dynamical torus
We have developed a new dynamical model of the torus region in active
galactic nucleus (AGN), using a three-dimensional radiation hydrodynamics
algorithm. These new simulations have the specific aim to explore the role of
radiatively-driven outflows, which is hotly debated in current literature as a
possible explanation for the observed infrared emission from the polar regions
of AGN. In this first paper, we only consider radiative effects induced by the
primary radiation from the AGN. The simulations generate a disk & outflow
structure that qualitatively agrees with observations, although the outflow is
radial rather than polar, likely due to the lack of radiation pressure from hot
dust. We find cut-offs between the wind and disk at gas temperatures of 1000 K
and dust temperatures of 100 K, producing kinematic signatures that can be used
for interpretation of high resolution infrared observations. We also produce
line emission maps to aid in the interpretation of recent ALMA observations and
future JWST observations. We investigate a number of simulation parameters, and
find that the anisotropy of the radiation field is equally important to the
Eddington factor, despite the anisotropy often being assumed to have a single
sometimes arbitrary form in many previous works. We also find that supernovae
can have a small but significant impact, but only at extremely high star
formation rates.Comment: 2nd revision, Accepted in Ap
Foliated Field Theory and String-Membrane-Net Condensation Picture of Fracton Order
Foliated fracton order is a qualitatively new kind of phase of matter. It is
similar to topological order, but with the fundamental difference that a
layered structure, referred to as a foliation, plays an essential role and
determines the mobility restrictions of the topological excitations. In this
work, we introduce a new kind of field theory to describe these phases: a
foliated field theory. We also introduce a new lattice model and
string-membrane-net condensation picture of these phases, which is analogous to
the string-net condensation picture of topological order.Comment: 22+15 pages, 8 figures; v3 added a summary of our model near the end
of the introductio
India's De-Industrialization Under British Rule: New Ideas, New Evidence
India was a major player in the world export market for textiles in the early 18th century, but by the middle of the 19th century it had lost all of its export market and much of its domestic market. Other local industries also suffered some decline, and India underwent secular de-industrialization as a consequence. While India produced about 25 percent of world industrial output in 1750, this figure fell to only 2 percent by 1900. We use an open, specific-factor model to organize our thinking about the relative role played by domestic and foreign forces in India's de-industrialization. The construction of new relative price evidence is central to our analysis. We document trends in the ratio of export to import prices (the external terms of trade) from 1800 to 1913, and that of tradable to non-tradable goods and own-wages in the tradable sectors going back to 1765. With this new relative price evidence in hand, we ask how much of the de-industrialization was due to local supply-side influences (such as the demise of the Mughal empire) and how much to world price shocks (such as world market integration and rapid productivity advance in European manufacturing), both of which had to deal with an offset the huge net transfer from India to Britain before 1815. Whether the Indian de-industrialization shocks and responses were big or small is then assessed by comparisons with other parts of the periphery.
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