This just got sent out to the physics department mailing list…

Well, no turning back now…

PhD Thesis Defense

Candidate:  Yonatan Zunger
Advisor:  Leonard Susskind

Tuesday, May 20, 9 AM
Varian 3rd Floor Conference Room

TITLE:
Building Branes Out of Matrices

ABSTRACT:
We examine the set of objects which can be built in type IIA string theory by
matrix methods using an infinite number of D0-branes. In addition to
stacks of ordinary Dp-branes and branes in background fields, we find
exotic states which cannot be constructed by other means. These states
exhibit strongly noncommutative geometry, (e.g., partial derivatives on them
do not commute) and some are conjectured to have Z_N–valued
charges similar to those of the type I D-instanton. Real-valued charges are
forbidden by Dirac quantization, leading to a nontrivial relationship
between noncommutative topological invariants.

Published in: on May 14, 2003 at 14:57  Comments (12)  
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Winner for the “bad article titles of the week” award: “Homeotic Supersymmetry,” by Barenboim and Lykken. I made it halfway through the abstract before I realized that I’d misread the title. (And that it wasn’t nearly as interesting as I’d first expected)

Published in: on April 1, 2003 at 17:22  Comments (4)  
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Interesting discovery…

Some recorded music uses stereo rather extensively: The two sound channels don’t sound much alike at all. You don’t notice this quite as much on speakers as you do on headphones.

Apparently, when I listen to such music on headphones, if I wear them the “right” way the music sounds slightly choppy and disorienting – but if I flip the headphones, so the right channel goes to my left ear and vice-versa, the music suddenly sounds completely natural. Apparently ear dominance is a real and easily detected thing.

Creepy.

Published in: on March 20, 2003 at 21:15  Comments (2)  
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…

Still trying to come to terms with the loss of the Columbia earlier today. I was the sort of kid who borrowed the worn old copy of the shuttle’s pilot’s manual from the library, and always had it checked out even after memorizing the whole thing. And manned spaceflight has always seemed to me to be a far more important thing than, well, almost anything else. For reasons I won’t go into here and now.

long/rant

Published in: on February 1, 2003 at 14:47  Comments (3)  
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Ill-chosen book titles

Our math library has a new book in stock: “Monte Carlo methods in finance.”

I’m just going to assume that this book is about numerical simulations, and not about taking the company till and running off to play blackjack…

Published in: on December 3, 2002 at 11:40  Comments (4)  
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Whew…

Well, that’s it… my paper is finally up on the web, available to the public, now with its very own preprint number, hep-th/0210175. It’s funny, it didn’t feel like it was really sent out until now… there’s just something about seeing my name on the daily papers list that just amplifies the reality.

OK, now to go submit it to a journal…

Updated: And it’s off… submitted to Physical Review D. Plus got to talk on the phone with my father, which is always good.

Published in: on October 20, 2002 at 18:20  Comments (2)  
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Thought for the day…

From the Annals of Improbable Research, today’s edition:

Investigator Ron Josephson alerted us to the following mathematics-related dispatch, which appeared in the October 11, 2002 issue of “The Salt Lake Tribune”:

The menu at the Coffee Garden at 900 East and 900 South in Salt Lake City has included a scrumptious selection of quiche for about 10 years.
The recipe calls for four fresh eggs for each quiche.
A Salt Lake County Health Department inspector paid a visit recently and pointed out that research by the Food and Drug Administration indicates that one in four eggs carries salmonella bacterium, so restaurants should never use more than three eggs when preparing quiche.
The manager on duty wondered aloud if simply throwing out three eggs from each dozen and using the remaining nine in four-egg-quiches would serve the same purpose.
The inspector wasn’t sure, but she said she would research it.

Published in: on October 18, 2002 at 10:31  Comments (4)  
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It is complete.

Wow.

After way too many months of work, I just sent my latest paper up to the archive. (Not accessible to the public yet; it’ll be available starting Sunday night)

hep-th/0210175

The basic result:

In string theory (type IIA string theory, to be precise) there exist certain higher-dimensional objects called D-branes, whose important dynamical property is that strings (the basic objects of the theory) can end on them. (Normally strings are little closed loops; there can also be open loops if the ends are on these D-branes. Closed strings behave like gravitons, open strings behave like photons and gluons and other force particles, and their endpoints on the D-brane behave like matter particles such as electrons and quarks) In type IIA string theory, these exist in even-dimensional variants: There are point particles (D0-branes, 0-dimensional) membranes (2-d) and so on up to 8-dimensional branes.

It’s been known for some time that certain collections of D0-branes can form a membrane: because of their interactions (imagine strings stretched from one D0-brane to another) they develop a tension, and fluctuate like a single membrane. This membrane is known to be the same as the D2-brane. (So you can think of a D2-brane as a bound state of a bunch of D0-branes)

My research was examining the most general configuration that can show up as a bound state of (infinitely many) D0-branes. The answer turns out to be that all of the ordinary branes (Dp-branes for p even) can be thought of as bound states of D0-branes. In addition to these, there seem to exist “exotic” branes which don’t fall into this usual category: Strings can end on them (like ordinary D-branes) but they have more complicated dynamics, their shapes being described by noncommutative geometry. (Which is kinda hard to explain – think of the points of space “fuzzing out” into patches in an irreducible way)

And, after something like 9 months on this, it’s finally ready to go. Submission to a journal (Phys. Rev. D) for peer review the moment it’s up on the web…

Yipee!

Published in: on October 17, 2002 at 23:56  Comments (11)  
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