Lisa Randall: A greater design?

Lisa Randall: Where does anything come from? I don’t even know what that question means. It could be that there just are these extra dimensions. Where do three dimensions come from? You know it’s funny. I think when we do our research, I mean some people might be thinking about that, and maybe afterwards you sit back and reflect. But when you’re actually solving a problem, you say assume these basic ingredients and proceed from there. What happens? You don’t ask . . . I mean after we did our work and then went back with another collaborator, _____, and asked why do we see three dimensions? Cosmologically could it be that three dimensions are special? And then we thought about how the universe would evolve with branes. But we try to turn it into scientific questions, not sort of just philosophical like, “Why are things the way they are?” But could . . . what would be the connections between? So the thing . . . I mean so . . . I mean you could be kept up at night by a minus sign, but it has nothing to do with some mundane particle physics problem. It’s sort of the problems themselves that are compelling in some sense when you’re actually doing your research. How could these pieces fit together? As I say when I started doing research, this type of particle physics, I didn’t think I would be working in extra dimensions. I probably would have felt as skeptical as you. Like . . . like yeah okay, sure. You can do anything with extra dimensions. But it’s not true that you can do anything. You can do some things, and it’s interesting to see what are those new phenomena. People had worked on general relativity for years without realizing you could have this infinite extra dimension. So by approaching things from very specific particle physics problems, we actually have discovered implications that you wouldn’t have seen otherwise. So it’s sort of a question of what are the connections among these . . . what are the implications of the equations that describe the gravitational field? What are the implications of particle physics in the scenario? So it’s trying to really see what the consequences would be. I’m not saying we know they exist. We don’t know they exist, but we wanna go in and test it. And I should say that, you know, I don’t know that this is the right answer to the hierarchy problem. But we are about to test experimentally what is happening at the scale – this scale that is about the massive Higgs particle. And when we do that, it could be this theory that we find. It could be other theories. But we wanna be ready. We wanna know what should they be looking for. And the only way to answer those questions is to think about what is the spectrum of possibilities. And I think this is a little bit hard for people to fathom that we’re working on all these theories. We don’t necessarily believe we know which one is right. But while you’re working on it, you just have to get into the mode and say, “Suppose the world is like this,” and try to figure it out. Recorded On: 11/2/07

Who put all those multiple dimensions out there anyway?

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The competition between forces from protons and neutrons inside a neutron star create super-dense shapes that look like long cylinders or flat planes, referred to as "spaghetti" and "lasagna," respectively. That's also where we get the overall name of nuclear pasta.

Caplan & Horowitz/arXiv

Diagrams illustrating the different types of so-called nuclear pasta.

The researchers' computer simulations needed 2 million hours of processor time before completion, which would be, according to a press release from McGill University, "the equivalent of 250 years on a laptop with a single good GPU." Fortunately, the researchers had access to a supercomputer, although it still took a couple of years. The scientists' simulations consisted of stretching and deforming the nuclear pasta to see how it behaved and what it would take to break it.

While they were able to discover just how strong nuclear pasta seems to be, no one is holding their breath that we'll be sending out missions to mine this substance any time soon. Instead, the discovery has other significant applications.

One of the study's co-authors, Matthew Caplan, a postdoctoral research fellow at McGill University, said the neutron stars would be "a hundred trillion times denser than anything on earth." Understanding what's inside them would be valuable for astronomers because now only the outer layer of such starts can be observed.

"A lot of interesting physics is going on here under extreme conditions and so understanding the physical properties of a neutron star is a way for scientists to test their theories and models," Caplan added. "With this result, many problems need to be revisited. How large a mountain can you build on a neutron star before the crust breaks and it collapses? What will it look like? And most importantly, how can astronomers observe it?"

Another possibility worth studying is that, due to its instability, nuclear pasta might generate gravitational waves. It may be possible to observe them at some point here on Earth by utilizing very sensitive equipment.

The team of scientists also included A. S. Schneider from California Institute of Technology and C. J. Horowitz from Indiana University.

Check out the study "The elasticity of nuclear pasta," published in Physical Review Letters.