Gravitational lensing results from the fact that General Relativity describes our universe: mass bends light and can function in effect like a lens, bending light in ways that can be used to infer the mass distribution itself. Gravitational microlensing is due to this same effect, but refers to the detection of objects which are of […]Read more "Finding earth like planets from the comfort of our own planet"
This is a review of the recent paper, to be published in Nature, by Andrew Potzen and Fabio Governato Cold dark matter heats up. The paper is itself a review, containing information published in previous studies. I gave a presentation about it at our weekly Astrophysics journal club. The figure in the header is M82, […]Read more "Cold dark matter heats up – a review of a review"
Using the new Voxcharta.org system, I was the only physicist at my institute to upvote this paper, Dynamic Bayesian Combination of Multiple Imperfect Classifiers (pdf), more in the realm of machine learning or computer science than traditional astrophysics or astronomy. As such I was nominated to discuss it at our weekly journal club. Here I give a brief review of concepts needed to follow the paper, and then go in depth into how we can use the opinions of multiple lay people as to whether an object is a supernova or not to achieve a highly accurate classification at the expert level.Read more "Dynamic Bayesian Combination of Multiple Imperfect Classifiers"
I use the Stay Focused Chrome extension to block Wordpress, Google Reader, Hacker News, Twitter and Facebook at work, beyond 2 minutes of aggregate usage.Read more "Scientific Paper Reading, Voxcharta, Excellent Notation"
Since last we spoke a couple of months ago, I had a hell of a time personally: I moved house, went from one location to another too often, had a major and very stressful financial crisis and had some rough times with friends which rocked the emotional boat. Although there are many things which didn’t […]Read more "The Intersection of Productivity and Joy (over the past months)"
A few days ago in gr-qc journal club we discussed an interesting paper by a member of our own institute, Probing the dark matter issue in f(R)-gravity via gravitational lensing.1. Background Dark Matter We theoretically expect dark matter to exist based largely on extensive observations of both dynamics (rotation curves and objects such as the […]Read more "Probing the dark matter issue in f(R)-gravity via gravitational lensing"
Walls, filaments and voids: it is thought that the large scale distribution of matter is a complex network of galaxies and galaxy clusters connected by elongated filaments and sheetlike walls, outlining vast underdense regions known as voids and meeting at dense and compact regions known as haloes. Aragon-Calvo et. al. in  build upon the SpineWeb framework outlined in  , which has the capability of identifying these walls, filaments and clusters in cosmological simulations to examine the effect of environment (namely whether a galaxy is “living” in a wall or a void) on the dispersion of the Hubble flow around the Milky, which is significantly lower than theoretical expectations. They show that the measured dispersion could be a result of the fact that Milky Way resides inside a wall of radius around 10Mpc, which is supported by data.Read more "Locally Cold Flows from Large-Scale Structure"
A few weeks ago, Astrophysics Master’s student Tina Wentz gave a great overview of the phenomenon known as the Pioneer Anomaly in our gr-qc journal club. I’m indebted to her for that overview as well as pointing me to relevant papers in the preparation of this post. Background Launched in 1972 and 1973 respectively, the […]Read more "The Pioneer Anomaly"
Globular Clusters (GCs) Globular clusters are groups of roughly spherical, densely packed stars. They are thought to have formed at the same time as most galaxies and the stars which make them up are some of the oldest known–thus GCs are an excellent probe of galaxy formation and evolution. They have a high central stellar […]Read more "The Andromeda Galaxy’s Globular Cluster System"
QFT I’m lucky to have a job in which I can take two weeks of mornings of work to study a nominally tangential subject in greater depth. These past two weeks I attended a series of lectures at the ETH on physics beyond the standard model, the first week was very technical but exciting to […]Read more "Quantum Field Theory (QFT), General Relativity (GR), and Other Exciting Diversions (OED)"