Day 38

Tuesday.  The Capak Subaru reduction script is running smoothly, I hope it continues to do so.


1106.6049
Using CMB data to constrain non-isotropic Planck-scale modifications to electrodynamics
Gubitosi, Migliaccio, Pagano, Amelino-Camelia, Melchiorri, Natoli, Polenta


Some quantum gravity effects on light propagation causes non-isotropic features of the CMB polarization.  Describe the expected signatures of this anomalous light propagation on CMB photons, which produces a non-isotropic birefringence effect, and is dependent on the observation direction.  Planck can test this, if the magnitude is set by the minute Planck length.


1106.6052
Discovery of energy dependent x-ray miroclensing in Q2237+0305
Chen, Dai, Kochanik, Chartas, Blackburne, Kozlowski


20 epochs spanning 10 years of Q2237+0305 x-ray observation with Chandra.  Detect variability at all bands, and chromatic microlensing (that doesn't make sense) between soft and hard bands.  Hard is more strongly microlensed; suggests corona above the accretion disk (which generates x-rays) has a non-uniform electron distribution: hotter/energetic e- occupy more compact regions surrounding BH.  Both hard and soft x-ray more strongly microlensed than the optical (restframe UV) emission; x-ray emission must be more compact than optical, in agreement with other lenses.


* the chromatic microlensing is due to the different distribution of sources--typically, the more compact the source is, the stronger the variability.


1106.6075
Global-scale simulations of stellar convection and their observational predictions
Brown


MHD simulation study of stellar convection coupled with rotation in F=>M stars, whose global-scale structure may be observable with interferometers that resolve stellar disks.  Differential rotation the most easily observable, with prograde equator and retrograde poles, in rapidly rotating stars.  Slow spinning stars may have "anti-solar rotation" profiles with fast poles and slow equators.  Thermal wind balance makes hot and bright poles in rapid rotators and coolor, darker poles in slow rotators.  Convection and differential rotation build global-scale magnetic structures in the bulk of the convection zone, which may be observable near the stellar surface.


* what to they mean by "global-scale"?  simply ~the size of the star?


1106.6231
Standard Cosmology Delayed
Choudhury, Ghoshal, Sen


* what do they mean by "introduction of a delay in the Friedmann equation of cosmological evolution?"
* energy condition: in relativistic classical field theories of graviatation (GR), one of various alternative conditions which can be aplied to the matter content of the theory
* strong energy condition: for every future-pointing timelike vector field X, the trace of the tidal tensor measured by the corresponding observers is always non-negative.  There are many matter configurations which violate the strong energy condition (e.g., a scalar field with a positive potential).


The introduction of delay in the Friedmann equation may obviate the need for a scalar field driven inflationary epoch--it shows the very early universe undergoing the accelerated expansion inthe usual radiation/matter dominated phase.  This expansion slows down naturally to the decelerated phase (Hubble expansion).


* what about DE (late time expansion)?  Does it explain that?


1106.5791
Detected fluctuations in SDSS LRG magnitudes: bulk flow signature or systematic?
Abate, Feldman


* I've read this one before.  Need to check for systematics in the LRG photometry to see if it's causing the bulk flow signature.


1107.0491
Towards a fully consistent parameterization of modified gravity
Baker, Ferreira, Skordis, Zuntz


General parameterization of modified gravity: similar to PPN approach.  Majority of such parameterizations are only exactly applicable in the quasistatic regime (?).  On larger scales they fail to encapsulate the full behaviour of typical models currently ounder consideration.  May be possible to capture the additions to the PPF by treating them akin to fluid perturbations.


1107.1255
Terapixel imaging of cosmological simulations
Feng, ... Springel, et al.


New visualization techniques for cosmological simulations.  Web interface to spatial and temporal images of Gadget hydro sims of 100 Tb or more.  Two examples presented: (1) MassiveBlack, and sim with >1000 frames.  Publicly accessible through the GigaPan website.


1107.1498
How accurate is our knowledge of galaxy bias?
Surhud More


Knowledge of bias needed to use galaxy clustering for cosmological parameter estimation.  Large scale bias: quantified by measuring the large-scale power spectrum of galaxies (lambda > 60 Mpc/h) or by modeling the HOD of galaixes using their clustering on small scales (lambda < 30 Mpc/h).  Compare luminosity dependence of galaxy bias, and check for consistency.  Comparison show: bias of galaxies from small scale clustering measurements is systematically larger than that obtained from large scale power spectrum measurements.  Also: systematic discrepancies in the shape of the galaxy bias-luminosity relation.  


* this is an interesting paper I want to read.