158 research outputs found
Conservation and divergence in modules of the transcriptional programs of the human and mouse immune systems [preprint]
Studies in mouse have shed important light on human hematopoietic differentiation and disease. However, substantial differences between the two species often limit the translation of findings from mouse to human. Here, we compare modules of co-expressed genes in human and mouse immune cells based on compendia of genome-wide profiles. We show that the overall modular organization of the transcriptional program is conserved. We highlight modules of co-expressed genes in one species that dissolve or split in the other species. Many of the associated regulatory mechanisms - as reflected by computationally inferred trans regulators, or enriched cis-regulatory elements - are conserved between the species. Nevertheless, the degree of conservation in regulatory mechanism is lower than that of expression, suggesting that distinct regulation may underlie some of the conserved transcriptional responses
X-ray scaling relations of early-type galaxies in IllustrisTNG and a new way of identifying backsplash objects
We investigate how feedback and environment shapes the X-ray scaling
relations of early-type galaxies (ETGs), especially at the low-mass end. We
select central-ETGs from the IllustrisTNG-100 box that have stellar masses
. We derive mock X-ray
luminosity () and spectroscopic-like temperature
() of hot gas within of the ETG haloes using
the MOCK-X pipeline. The scaling between and the total
mass within 5 effective radii () agrees well with observed ETGs
from Chandra. IllustrisTNG reproduces the observed increase in scatter of
towards lower masses, and we find that ETGs with
with
above-average experienced systematically lower cumulative
kinetic AGN feedback energy historically (vice versa for below-average ETGs).
This leads to larger gas mass fractions and younger stellar populations with
stronger stellar feedback heating, concertedly resulting in the above-average
. The --
relation shows a similar slope to the observed ETGs but the simulation
systematically underestimates the gas temperature. Three outliers that lie far
below the -- relation all interacted with larger galaxy
clusters recently and demonstrate clear features of environmental heating. We
propose that the distinct location of these backsplash ETGs in the -- plane could provide a new way of identifying backsplash
galaxies in future X-ray surveys.Comment: 16 pages, 10 figures. Submitted to MNRA
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Trapped Inflation
We analyze a distinctive mechanism for inflation in which particle production slows down a scalar field on a steep potential, and show how it descends from angular moduli in string compactifications. The analysis of density perturbations - taking into account the integrated effect of the produced particles and their quantum fluctuations - requires somewhat new techniques that we develop. We then determine the conditions for this effect to produce sixty e-foldings of inflation with the correct amplitude of density perturbations at the Gaussian level, and show that these requirements can be straightforwardly satisfied. Finally, we estimate the amplitude of the non-Gaussianity in the power spectrum and find a significant equilateral contribution
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Holographic Systematics of D-brane Inflation
We provide a systematic treatment of possible corrections to the inflaton potential for D-brane inflation in the warped deformed conifold. We consider the D3-brane potential in the presence of the most general possible corrections to the throat geometry sourced by coupling to the bulk of a compact Calabi-Yau space. This corresponds to the potential on the Coulomb branch of the dual gauge theory, in the presence of arbitrary perturbations of the Lagrangian. The leading contributions arise from perturbations by the most relevant operators that do not destroy the throat geometry. We find a generic contribution from a non-chiral operator of dimension {Delta} = 2 associated with a global symmetry current, resulting in a negative contribution to the inflaton mass-squared. If the Calabi-Yau preserves certain discrete symmetries, this is the dominant correction to the inflaton potential, and fine-tuning of the inflaton mass is possible. In the absence of such discrete symmetries, the dominant contribution comes from a chiral operator with {Delta} = 3/2, corresponding to a {phi}{sup 3/2} term in the inflaton potential. The resulting inflationary models are phenomenologically identical to the inflection point scenarios arising from specific D7-brane embeddings, but occur under far more general circumstances. Our strategy extends immediately to other warped geometries, given sufficient knowledge of the Kaluza-Klein spectrum
On the influence of the cosmological constant on gravitational lensing in small systems
The cosmological constant Lambda affects gravitational lensing phenomena. The
contribution of Lambda to the observable angular positions of multiple images
and to their amplification and time delay is here computed through a study in
the weak deflection limit of the equations of motion in the Schwarzschild-de
Sitter metric. Due to Lambda the unresolved images are slightly demagnified,
the radius of the Einstein ring decreases and the time delay increases. The
effect is however negligible for near lenses. In the case of null cosmological
constant, we provide some updated results on lensing by a Schwarzschild black
hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation,
references added, results unchanged, in press on PR
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