Another Teeny Tiny Struggle

I recently wrote of my My Universal (and Expanding) Struggles.  The title is very tongue-in-cheek, but it is mildly amusing to think that some deranged skinhead might stumble on my page and think to himself “what the heil?”  (Oh ok, I admit it, that too was a joke.)

Back to the matter at hand – physics and more specifically, cosmology … even more specifically another one of my struggles associated with it.

I had forgotten about this particular struggle, but I was reminded by something said in skydivephil’s latest video, The Story of Loop Quantum Gravity - From the Big Bounce to Black Holes.  I think of the universe, in one sense, as being the eventual consequence of a prior universe in which matter has collected into a black hole over a period of eternity within that prior universe.  Time that other universe is orthogonal to time in our universe and you can think of all the mass energy being deposited instantaneously, or rather within the first quanta of time.

What I don’t envisage is that all this mass-energy appears in a singularity.  Instead, I see it all being compacted into the minimum amount of space consistent with the universe’s mass-energy being at the Planck density.

However, people are always going on about the initial singularity or the big bang starting with everything condensed down to infinite density.  There’s a corresponding argument regarding the centre of a black hole.

Imagine my joy then to hear that, in June 2001, there was a short paper by Martin Bojowald that suggests that in quantum geometry the singularity is removed (video reference | original paper).  Furthermore, in the video, the presenter specifically refers to planck density shortly after this image is shown:

Note that my conceptualisation isn’t completely consistent with this image, since I would not see the universe on the other side of the big bang as being in line with our universe, but rather orthogonal (ie perpendicular) to it.  This concept is however hinted at slightly later in the video, when the Hartle-Hawking No Boundary model is discussed.  “There is a real and an imaginary time.”  A feature of “imaginary” time is that it is orthogonal to “real” time.  Note that imaginary time isn’t made up, it’s a reference to imaginary numbers which are extremely handy for various tasks in physics and engineering.

The key point in the image is that there is no singularity, the size of universe decreases significantly, but not infinitely, and then expands back out again.  In respect to the planck density, the presenter refers to another paper by Ashtekar, Pawlowski and Singh (video reference | paper) – note that one of the people being interviewed for the video is the first listed on this paper.  The narrow tube shown to sort of link one universe with the other is an (almost certainly extremely brief) era in which planck density is achieved.

---

So, I did struggle with regard to the singularity, but it seems I didn’t need to.  If quantum loop theory is close to the money, there is no singularity.