Archive for April, 2007

In what I can only imagine was a moment of inspired procrastination, Steffen, my friend and fellow Part III student, did a demographic survey of this year’s Part III theoretical physicists (hep/gr). There’s some small wiggle room for error in the data, but the rough results are as follows: Total number of Part III theoretical […]


A few months ago some of the Part III students were having a good time calculating the symmetry factors of silly Feynman diagrams. Perhaps there are others out there who would be amused by the game. References For those who don’t spend much time thinking about symmetry factors, section 9 of Mark Srednicki’s QFT book […]


How to get left/right-handed 4D theories from an ambidexterous 5D theory… demote the 5th dimension from a manifold to an orbifold. In a previous post I introduced the 5D chirality problem. The problem was that there is no such thing as a 5D parity operator, and hence 5D spinors are Dirac spinors. In other words, […]


This post is not about physics; the post on orbifolding in extra dimensions has been delayed. This is also a post on a current event and possibly a sensitive/political subject. My intent is to discuss, hopefully without causing any offense. Topics in this post came from a conversation with a colleague in Los Angeles. The […]


Message from the 5th dimension: “We’re ambidexterous up here. Why are you left/right-handed?” There are lots of neat little problems that pop up when you play with models of extra dimensions. One such problem that one might not have expected is how to write down a 4D chiral theory. For simiplicity let’s play with a […]


The NASA/Stanford University Gravity Probe B (GPB) team has made its first public announcement at the 2007 American Physical Society April Meeting, and they have announced that the geodetic effect predicted by general relativity has been confirmed to within 1%. Analysis on the `frame-dragging’ effect is ongoing, complete results are expected to be announced in […]


My good friend Adam is a postgrad at the Cambridge Institute of Astronomy. He’s active in science outreach and is good at identifying key points where the general public and practicing scientists often misunderstand one another. One particular point that has come up several times is the use of the word “theory” in high energy […]