Day 3

Day 3 of blog and Nice vacation (went to Italy, then Monaco, one day after the Grand Prix).


http://arxiv.org/abs/1105.3980
Cosmic-shear covariance:  The log-normal approximation
Hilbert, Hartlap, Schneider


* Is this the same idea about power law "gaussianization", but applied to WL shear power?


Covariance of the cosmic shear correlation functions is needed to get accurate error estimates on the cosmological parameters.  Assume that the underlying convergence field follow log-normal statistics, then derive expressions for the cosmic shear covariance.  A simplified version:  retain only the "most important terms" beyond normal statistics.  This has been compared against simulated WL measurements for all 3 cases (normal, log-normal, simplified log-normal). Normal approximation underestimates the confidence region.  Log-normal approximation give more realistic confidence regions, but [takes longer--it mentions evaluating complex expressions]?  The simplified log-normal approximation has the same confidence region accuracy.


* Answer: yes, it seems to be the case.




http://arxiv.org/abs/1105.4099
On a novel approach using massive clusters at hight redshifts as cosmological probe
Waizmann, Ettori, Moscardini


* Something other than the cluster mass function's dependence (namely the high-mass tail) on the cosmological parameters?


Measure the cumulative distribution of the most massive halos in a sample of sub-volumes tiled in the sky at fixed redshift (just like a set of "test cosmologies")---to validate the fiducial LCDM model.  Use the high-mass tail of the mass function, along with general extreme value statistics (GEV) to obtain cumulative distribution function of the massive halos in a given volume.  The distribution within the test-cosmology volumes gives a different probe.  Need accuracy of 20-30% in cluster mass required, as well as a large area survey over z=1 (1.5) for 10^14.5 M_sun/h (10^14M_sun/h) halos.


* I guess it's more robust to check for the "extreme statistics" over many independent volumes, than just doing so from a single volume.  Using the cumulative distribution function helps with reducing the uncertainty.




http://arxiv.org/abs/1105.5421
Towards and observational appraisal of string cosmology
Mulryne, Ward


* Why am I bothering with an abstract that I probably won't understand?


They discuss the observational footprints of several string theory models in the paper.  Unfortunately, no details given in the abstract.  As you may have noticed, I'm only doing an abstract reading, not a paper reading.


* ...and that's that.




http://arxiv.org/abs/1105.5596
A dynamical model of the local group
Peebles, Tully, Shaya


* What does Peebles have to say?


The dynamics of the Local Group is modeled:  28 galaxies, distances less than 1.5 Mpc.  They must have had small peculiar velocities at high redshift, which grew according to standard cosmology.  Model mostly consistent (MW rotation speed), with the following notes:  10 of the LG galaxies seem to be remnants from failed galaxy assembly.  NGC6822 was closest to MW at z~0.27.  Leo I has large angular velocity that may be measurable by the mean stellar motion.  15 galaxies have proper motions greater than 0.05 mas/yr, measurable for with masers.


* Cool.




http://arxiv.org/abs/1105.5599
Long-term transit timing monitoring and refined light curve parameters of HAT-P-13b
Fulton, Shporer, Winn, Holman, Pal, Zachary, Gazak


* Uh oh, is this going to be about cosmology?  At least maybe SNe?


It's about a hot Jupiter transit curve