## Wednesday, March 28, 2007

### Jordan Algebras and Extremal Black Holes

Back in 2003, Pierre Ramond wrote a classic paper entitled Exceptional Groups and Physics where he considered the mysterious relationship between M-theory and the exceptional Lie groups. On pages 8 and 9, he discussed the exceptional Jordan algebra (EJA) and its automorphism group F4, arguing that the SO(9) subgroup of F4 should be interpreted as the light-cone little group in eleven dimensions. He concluded with the statement:

"If the SO(9) subgroup of [the] EJA automorphism group F4 can indeed be identified with the light-cone little group in eleven space-time dimensions, it will suggest the EJA as the charge space of a very special system."

In February 2005, Murat Gunaydin showed the EJA is actually the charge space of an extremal black hole in N=2, d=5 Maxwell-Einstein supergravity. Come summer 2005, Andrew Neitzke, Boris Pioline and Andrew Waldron joined forces with Murat Gunaydin and formulated a method for counting microstates of four-dimensional BPS black holes in N >= 2 Maxwell-Einstein supergravities. Gunaydin gave a December 9th talk on the approach at the KITP and by December 22 the work culminated in a paper entitled BPS black holes, quantum attractor flows and automorphic forms.

It turns out there are more Jordan algebraic goodies that add to the story, so I put together a paper and posted it here. :)

(Note: The image above is a depiction of the Bajoran wormhole from the Star Trek: Deep Space Nine series)

## Thursday, March 22, 2007

### Ternary Logic

Earlier this week, Kyle (a fellow physics grad student) got me thinking about the set of single variable functions from a finite set A={a,b,c} to a finite set B={0,1,2}. Such functions involve triples of elements of A x B, and take for example the form f_012={(a,0), (b,1), (c,2)}. I ended up using shorthand for such functions, writing f_012 as 012 for instance, to reveal the nice single variable ternary function structure. Ultimately, I came up with the above diagram to show how multiple copies of the parity cube vertices arise in this set of functions. I guess one can also look at it as a Qutrit function diagram. Kea and Carl may see further applications in particle physics. ;)

## Monday, March 19, 2007

### AIM Team Maps E8

Congratulations to the Atlas team for their fine work in computing the Kazhdan-Lusztig-Vogan polynomials for the large block of the split real form of E8. AIM's popular overview can be found on their E8 page. For the wonderful details see the Atlas overview.

## Friday, March 16, 2007

### 3D Discrete Dynamical Systems

Shown above are 3D scatter plots of several trajectories for a saddle point origin. The program is written in C, based on an old computer graphics project. The L triplet denotes the eigenvalues used to generate the system.

## Sunday, March 11, 2007

### Standard Model Particle Masses

For all of you that suddenly awaken at night (in a cold sweat) because you forgot your SM particle masses, make sure to check out the PDG page for a refresher.