524 research outputs found
Frand and Compulsory Licenses: Analysis and Comparison
This section compares two different forms of licenses being FRAND and complusory license. Both forms of licenses are critical to achieve access to otherwise difficult to access technologies. The FRAND licenses have been widely embraced, especially in the software, mobile phones, and communications sectors. Compulsory licenses have been sparingly used by Governments where the public\u27s need for the invention was considered to over-weigh the needs of the patentee, essentially for pharmaceuticals. Compulsory licenses have been universally criticized for being an imposed burden on the patentee. In comparing these two forms of licenses, this section outlines that despite the obvious differences operationally both of these have stark similarities and highlights areas where complusory licenses operate more efficiently. In doing so, this section highlights that perhaps each of the forms of licenses can borrow from the other to minimize the weaknesses to ulitmately enable more access for critical inventions
The Reionization of Carbon
Observations suggest that CII was more abundant than CIV in the intergalactic
medium towards the end of the hydrogen reionization epoch. This transition
provides a unique opportunity to study the enrichment history of intergalactic
gas and the growth of the ionizing background (UVB) at early times. We study
how carbon absorption evolves from z=10-5 using a cosmological hydrodynamic
simulation that includes a self-consistent multifrequency UVB as well as a
well-constrained model for galactic outflows to disperse metals. Our predicted
UVB is within 2-4 times that of Haardt & Madau (2012), which is fair agreement
given the uncertainties. Nonetheless, we use a calibration in post-processing
to account for Lyman-alpha forest measurements while preserving the predicted
spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way
that it always exceeds the volume average in regions where metals are found.
This implies both that a spatially-uniform UVB is a poor approximation and that
metal absorption is not sensitive to the epoch when HII regions overlap
globally even at column densites of 10^{12} cm^{-2}. We find, consistent with
observations, that the CII mass fraction drops to low redshift while CIV rises
owing the combined effects of a growing UVB and continued addition of carbon in
low-density regions. This is mimicked in absorption statistics, which broadly
agree with observations at z=6-3 while predicting that the absorber column
density distributions rise steeply to the lowest observable columns. Our model
reproduces the large observed scatter in the number of low-ionization absorbers
per sightline, implying that the scatter does not indicate a partially-neutral
Universe at z=6.Comment: 16 pages, 14 figures, accepted to MNRA
Frand and Compulsory Licenses: Analysis and Comparison
This section compares two different forms of licenses being FRAND and complusory license. Both forms of licenses are critical to achieve access to otherwise difficult to access technologies. The FRAND licenses have been widely embraced, especially in the software, mobile phones, and communications sectors. Compulsory licenses have been sparingly used by Governments where the public\u27s need for the invention was considered to over-weigh the needs of the patentee, essentially for pharmaceuticals. Compulsory licenses have been universally criticized for being an imposed burden on the patentee. In comparing these two forms of licenses, this section outlines that despite the obvious differences operationally both of these have stark similarities and highlights areas where complusory licenses operate more efficiently. In doing so, this section highlights that perhaps each of the forms of licenses can borrow from the other to minimize the weaknesses to ulitmately enable more access for critical inventions
X-ray Observations of the Warm-Hot Intergalactic Medium
We present Chandra observations that provide the most direct evidence to date
for the pervasive, moderate density, shock-heated intergalactic medium
predicted by leading cosmological scenarios. We also comment briefly on future
observations with Constellation-X.Comment: To be published in the proceedings of the conference "IGM/Galaxy
Connection- The Distribution of Baryons at z=0". 6 page
SIGAME simulations of the [CII], [OI] and [OIII] line emission from star forming galaxies at z ~ 6
Of the almost 40 star forming galaxies at z>~5 (not counting QSOs) observed
in [CII] to date, nearly half are either very faint in [CII], or not detected
at all, and fall well below expectations based on locally derived relations
between star formation rate (SFR) and [CII] luminosity. Combining cosmological
zoom simulations of galaxies with SIGAME (SImulator of GAlaxy
Millimeter/submillimeter Emission) we have modeled the multi-phased
interstellar medium (ISM) and its emission in [CII], [OI] and [OIII], from 30
main sequence galaxies at z~6 with star formation rates ~3-23Msun/yr, stellar
masses ~(0.7-8)x10^9Msun, and metallicities ~(0.1-0.4)xZsun. The simulations
are able to reproduce the aforementioned [CII]-faintness at z>5, match two of
the three existing z>~5 detections of [OIII], and are furthermore roughly
consistent with the [OI] and [OIII] luminosity relations with SFR observed for
local starburst galaxies. We find that the [CII] emission is dominated by the
diffuse ionized gas phase and molecular clouds, which on average contribute
~66% and ~27%, respectively. The molecular gas, which constitutes only ~10% of
the total gas mass is thus a more efficient emitter of [CII] than the ionized
gas making up ~85% of the total gas mass. A principal component analysis shows
that the [CII] luminosity correlates with the star formation activity as well
as average metallicity. The low metallicities of our simulations together with
their low molecular gas mass fractions can account for their [CII]-faintness,
and we suggest these factors may also be responsible for the [CII]-faint normal
galaxies observed at these early epochs.Comment: 24 pages, 14 figures. Accepted for publication in the Astrophysical
Journa
The cosmic baryon partition between the IGM and CGM in the SIMBA simulations
We use the SIMBA suite of cosmological hydrodynamical simulations to investigate the importance of various stellar and active galactic nuclei (AGN) feedback mechanisms in partitioning the cosmic baryons between the intergalactic (IGM) and circumgalactic (CGM) media in the z †1 Universe. We identify the AGN jets as the most prominent mechanism for the redistribution of baryons between the IGM and CGM. In contrast to the full feedback models, deactivating AGN jets results in â20 per cent drop in fraction of baryons residing in the IGM and a consequent increase of CGM baryon fraction by â50 per cent.We find that stellar feedback modifies the partition of baryons on a 10 per cent level. We further examine the physical propertiesof simulated haloes in different mass bins, and their response to various feedback models. On average, a sixfold decrease inthe CGM mass fraction due to the inclusion of feedback from AGN jets is detected in 1012 M †M200 †1014 M haloes. Examination of the average radial gas density profiles of M200 > 1012 M haloes reveals up to an order of magnitude decrease in gas densities due to the AGN jet feedback. We compare gas density profiles from SIMBA simulations to the predictions of the modified NavarroâFrenkâWhite model, and show that the latter provides a reasonable approximation within the virial radii of the full range of halo masses, but only when rescaled by the appropriate mass-dependent CGM fraction of the halo. The relative partitioning of cosmic baryons and, subsequently, the feedback models can be constrained observationally with fast radio bursts in upcoming surveys
Lyman-alpha Forest Constraints on the Mass of Warm Dark Matter and the Shape of the Linear Power Spectrum
High resolution N-body simulations of cold dark matter (CDM) models predict
that galaxies and clusters have cuspy halos with excessive substructure.
Observations reveal smooth halos with central density cores. One possible
resolution of this conflict is that the dark matter is warm (WDM); this will
suppress the power spectrum on small scales. The Lyman-alpha forest is a
powerful probe of the linear power spectrum on these scales. We use
collisionless N-body simulations to follow the evolution of structure in WDM
models, and analyze artificial Lyman-alpha forest spectra extracted from them.
By requiring that there is enough small-scale power in the linear power
spectrum to reproduce the observed properties of the Lyman-alpha forest in
quasar spectra, we derive a lower limit to the mass of the WDM particle of 750
eV. This limit is robust to reasonable uncertainties in our assumption about
the temperature of the mean density gas (T0) at z=3. We argue that any model
that suppresses the CDM linear theory power spectrum more severely than a 750
eV WDM particle cannot produce the Lyman-alpha forest.Comment: 13 pages including 4 color Figures and 1 Table, submitted to ApJ
Letter
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