Monday, February 8, 2010

A Helpful Way To Understand Inflation Induced Perturbations

I heard an intuitive explanation about what is going on with inflation induced perturbations that I enjoy:

During inflation, the spacetime is expanding at an exponential rate (faster then the speed of light) driven by quantum fields.   These quantum fields are in some sense conveying information to the spacetime which reacts by expanding exponentially.

However, when the inflation field(s) turn off, that new information is communicated to the expanding spacetime with an amount of uncertainty that matches Heisenberg's uncertainty principle.  Given this "Heisenberg's uncertainty principle's" amount of uncertainty in knowing when to stop, some points in space stop inflating slightly differently than others.

If you do the math, this uncertainty should lead to fluctuations in the spacetime on the order of one part in 10^5, which is exactly what we see. (Go inflation getting another prediction right again!)

(If the above words made no sense), look at the picture.  (The picture is technically of something else, but it should get the job done.)  Each slice can be thought of as a patch inflating bigger and bigger.  Soon the quantum fields tell the spacetime to stop inflating.  Given there is some quantum uncertainty in this command, different regions stop inflating at slightly different times leading to the noticeable fluctuations in spacetime seen at the top.

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