One interesting way in which our cosmos may have formed is in a collision between two other universes with extra spatial dimensions called braneworlds.
In this scenario, known as the ekpyrotic model of the universe, our cosmos is just a small four-dimensional corner of a much more complex space.
The ekpyrotic model is interesting because it leads to a flat universe like our own without the need for inflation, the period just after the Big Bang in which our universe supposedly swelled by many orders of magnitude in the blink of an eye.
Without inflation, our universe is just too big to have been formed in a Big Bang-type event. But nobody knows what might cause such a dramatic increase in size. Hence the interest in another way of explaining our existence.
If you’re wondering what actually collides in the ekpyrotic version of events, the answer is Minkowski domain walls, essentially the edges of universes with different spatial dimensions.
It’s easy to imagine that Minkowski domain walls are entirely theoretical. And indeed they were until now.
Today, Igor Smolyaninov and Yu-Ju Hung at the University of Maryland, in College Park, say they’ve created Minkowski domain walls in the lab for the first time and even used them to simulate the collision of two braneworlds.
The trick these guys have used is a formal analogy between the mathematics of space time and of electromagnetic spaces. Physicists have known since Einstein’s day that it is possible to bend and distort the fabric of spacetime—our universe appears to be distorted in just this way on various cosmic scales.
But it is only in the last ten years or so that they’ve learnt how to do the same on a much smaller scale with electromagnetic spaces. What’s triggered this is the development of metamaterials: artificial substances that can bend light in almost any way imaginable.
Smolyaninov is fascinated by one version of this stuff called hyperbolic metamaterial. Inside this substance, monochromatic light propagates in a similar way to massive particles in a Minkowski spacetime, where one spatial coordinate takes on the role of time.
Hyperbolic metamaterials are essentially a series of metal layers separated by a dielectric. Smolyaninov has used this stuff to simulate a number of interesting aspects of cosmology including the Big Bang itself.
The collision between universe’s is a variation on this theme. “The “colliding universe” scenario can be realized as a simple extension of our earlier experiments simulating the spacetime geometry in the vicinity of big bang,” he says.
He simulates an expanding universe using concetric rings of gold separated by a dielectric. “When the two concentric ring (“universe”) patterns touch each other (“collide”), a Minkowski domain wall is created, in which the metallic stripes touch each other at a small angle,” he says.
Being able to recreate these exotic events in the lab is certainly interesting but it is beginning to lose its novelty. The problem is that this work is not telling us anything we didn’t know–the universe behaves the same way inside a metamaterial as it does outside.
What Smolyaninov needs is a way of using his exotic materials to do something interesting. In other words, he needs a killer app. Any ideas?
Ref: arxiv.org/abs/1201.5348: Collision Of “Metamaterial Universes”: Experimental Realization Of Minkowski Domain Wall