Speaker: Abie Flaxman
Time: Wednesday 12-1pm
Place: NSH 1507
Title: Expansion and lack thereof in perturbed random graphs
Abstract:
Whenever the CMU Theory Lunch has a talk about “real-world” random graphs, someone in the audience asks if the graphs under consideration are expanders. This talk will address the question directly with respect to perturbed random graphs, which are formed by starting with an arbitrary base graph and adding a sparse random graph. The techniques used also reveal a suprising fact about the small-world graphs studied by Jon Kleinberg [Proc. of 32nd ACM STOC (2000), 163--170]: the expansion undergoes a phase transition exactly at the point where the graph is efficiently navigable by a decentralized algorithm.
Recently I have started a research project that requires quite a bit of Excel. Now if you don’t use Excel for research, maybe you still use it for keeping class grades once in a while? 
The first thing I do on every Excel installation is to change it to the R1C1 style. In Excel, each cell can be referenced in two styles: A1 and R1C1. (See a bit of history here.)
The former is the default (as of Version 2003). Each cell is referenced by its column name and then row number. So the first cell is called A1.
The latter is my preferred style. Each cell is referenced by its row number and column number. So the first cell is called R1C1.
Now some people may think that “E3″ is more intuitive than “R3C5″, and I can probably agree with them when the spreadsheet is small. But when the spreadsheet gets big and spans a couple hundred columns, I cannot contemplate seeing “BK439″…
To switch to the R1C1 style, go to tools->Options->General->R1C1 Reference Style.
The two styles are equivalent in power (if you use them right), but I will show you later why R1C1 has an advantage when it comes to formula editing.
My recent harddrive crashes (four times in three months) forced me to reinstall a lot of softwares on several machines. As a side-benefit, I get to upgrade all my softwares to the the latest versions. For the most part, this is a good thing. For example, Vim is now in version 7; WinMerge has seen a lot of improvement in its user interface; and Ipe 6pre26 actually works very nicely. I have also upgraded Miranda, FreeMind, TortoiseSVN and 7-zip. I thank the authors/contributors of these softwares and many others that I do not have the time to list. I know how much effort it takes. Thank you!
But then, there are also other “developments”. The most notable one is TexPoint. I think version 2.0.3 is the one I had and is the last free version. I also notice that GSView now has a “nag screen”. But its licence suggests that no payment is required. In any case, I still want to thank the authors of these softwares. They have indeed made my life better.
