The Simpsons Movie debuted this weekend to higher-than-expected sales, bearing testament to the show's enduring popularity. If you needed any convincing that after 18 years on the air The Simpsons has thoroughly penetrated the popular consciousness, consider the following usage of the word "embiggen," one of the many fine references with which one Simpsons fan can detect another.

The term comes from the 1996 episode Lisa the Iconoclast, in which we learn that a young Jebediah Springfield is supposed to have spoken it after wrestling a bison, or "land cow."

Jebediah: [on film] A noble spirit embiggens the smallest man.
Edna: Embiggens? I never heard that word before I moved to Springfield
Ms. Hoover: I don't know why. It's a perfectly cromulent word.

Here is the word in a rather different context:

While in both cases for P anti-D3-branes the probe approximation is clearly not good, in the set up of this paper we could argue that there is a competing effect which can overcome the desire of the anti-D3s to embiggen, namely their attraction towards the wrapped D5s. Hence, also on the gravity side, the non-supersymmetric states would naively be meta-stable.

That's string theory-ese, for the uninitiated.



This passage comes from a paper by Stanford University physicist Shamit Kachru and three colleagues, entitled (duh) Gauge/gravity duality and meta-stable dynamical supersymmetry breaking. [Hat tip to Kottke.org by way of the illustrious Chris Mims.]

String theory is physicists' best guess at how to unify quantum mechanics with gravity, which ought to be swell for understanding what happens inside black holes and before the big bang, as well as why nature has the different forces it does. Unfortunately, researchers have had a hard time putting it to the test because it is consistent with many different possible universes, of which more later.

I emailed Kachru, one of the most prominent younger researchers working on string theory, to get the back-story. Here's what he told me, in Q-and-A form. (Hint: it only has to do with the biggest development in string theory in the last 10 years.)

SA: How did you come across the word embiggen?

SK: I first came across this word in "The Simpsons," a source of knowledge for all serious theoretical physicists. It was used in the sentence "A noble spirit embiggens the smallest man." So by context I assume it means "to enlarge or expand in size."

The passage deals with something called a D-brane. What is that, exactly, and why is it important?

You can imagine two types of strings, closed loops and "open strings" (like jump ropes, with two ends). The open strings can only end on objects called D-branes, which are objects in the theory that can have any spatial dimension from 0 (a point) to 9 (filling all 10 spacetime dimensions). So e.g. a 2-brane is like a sheet of paper, on which open strings are allowed to end.

In many string theories, although gravity arises "for free," the only way to get gauge interactions [i.e., other forces--ed.] analogous to electromagnetism and the strong and weak nuclear forces, is by having D-branes present in the vacuum [meaning spacetime].

A 3-brane could fill all of our observed 3 spatial dimensions, and if the right gauge interactions arise on it from careful study of the open strings, we could even imagine that we live on such a D3 brane.

Later, in my research (starting in [this 2001 paper]), I encountered a phenomenon where D-branes in certain string backgrounds [or shapes of spacetime] like to expand into "larger" D-branes (which is known in general as the Myers effect). A rough analogue is the behavior of an atom in an electric field: although the atom is electrically neutral, the field polarizes the constituent electrons and protons, and pulls the atom apart a little bit, making it bigger. (I.e. there is [what is called] a dipole moment <ins>[or an overall separation of positive and negative charge]</ins>.

Similarly, D-branes in string theory can carry dipoles of higher D-brane charges. The relevant case for us was that a D3 brane can carry D5 dipole charge; in the right circumstances, background fields (analogous to the electric field above) then cause it to "expand" into a D5 brane wrapping some two-dimensional curve in the geometry.

You can see that in this situation, it is ideal to use the phrase "...the
anti-D3 brane embiggens into a D5 brane wrapping..." and that is roughly the context in which we used the phrase.

Why is it important if an anti-D3 brane embiggens into a D5 brane?

In the circumstance we were studying, the presence of the anti-D3
brane breaks supersymmetry, which is a symmetry of the 10d string theory (but is broken in our world for sure [sort of like the way the Earth "breaks" the spatial symmetry of empty space, in which there is no "up" or "down." If supersymmetry (SUSY) was unbroken, particle accelerators would have found a bunch of particles that they haven't--(still) ed]).

The embiggening into a D5 brane is an attempt by the object to relax the supersymmetry breaking and get back to a supersymmetric (zero energy) vacuum. However, in the circumstance we studied, it cannot "embiggen" enough to decay and restore supersymmetry.

So is this part of an attempt to match up string theory with the real world?

The anti-D3 brane SUSY breaking actually played an important role in the KKLT paper of 2003 (hep-th/0301240) [named for the initials of Kachru and three co-authors], which was one of the first constructions of de Sitter space [or an accelerating universe] in string theory and was in many ways rather influential.

In that sense, these "embiggened" states have played an important role in attempts to model one of the qualitatively new phenomena (accelerated expansion of the Universe) that was just discovered in the late 1990s.

["Rather influential" is right. Molding string theory to fit any sort of universe that is expanding in an accelerated fashion--such as our own--was long a stumbling block. In achieving their result, KKLT helped realize the concept of a "landscape" of possible universes in string theory (paywall, sorry), the controversy surrounding which became a huge story last year.--ed.]

Have any of your colleagues recognized your use of the word?

When I gave a draft of one of the papers using this word to [fellow Simpsons fan] Joe Polchinski [of the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara] and asked him to among other things to comment on the referencing in the paper, he replied "Your referencing looks perfectly cromulent." I didn't remember cromulent and had to look it up myself!

Ok, now for the serious stuff. What's your favorite physics moment from the show?

I think my favorite physics moment in the Simpsons is the episode (I think it was one of the Halloween episodes) where Homer discovers the 3rd dimension" behind a bookcase. He then "falls into the 3rd dimension" and experiences weird laws of physics. Eventually, the 3rd dimension collapses into a black hole and spits him out into an alternate reality.

Do you intend to see the Simpsons Movie?

Definitely! I can tell just from the previews with the Spider Pig that I will really like it.