Essay:Inflation theory 101
Ed note: This is by no means an exhaustive explanation and merely represents a way to think about Inflation theory - A means to imagine the process as opposed to a full description of the process itself - Acei9 02:28, 23 June 2010 (UTC)
Imagine nothing. Not nothing in time as in a lack of matter and space, but no universe.
No time, no stuff, just a void or vacuum. But this void has a peculiar quality to it; it has a quantum state, a field. It is a field that is subjected to the uncertainty principle and probability. It’s a seething “foam” of particles - popping in and out of existence. These virtual particles borrow energy from the field, appear into existence and disappear back into it again, returning their energy so as not to violate the conservation of energy law. That’s what we call a quantum fluctuation. The appearance of matter (I use “matter” here broadly – for lack of a better term) is a fluctuation in the field.
The energy state of this field isn’t its true energy. While the energy of this field is zero sum (hence “nothing” because the energy is zero, balanced by two competing forces. One one hand there is the energy provided by the vacuum energy and on the other hand is the replusion of negative gravity caused by the fluctuations), with the energy of the vacuum matching exactly the energy taken by the fluctuations. But this is an unstable balance of energies. It is a more energetic state than would you’d have without these fluctuations. Something we know in physics is that particles, atoms, anything will always try to attain the lowest possible energy state, to entropy. So these fluctuations from the quantum field produce energy, a higher energy than what would be if the field were at rest.
This may sound like circular, “The energy comes from the quantum fluctuations which are caused by the energy” but that is a misunderstanding. The field, this nothing, has an energy state already but the quantum fluctuations produce a higher energy state through the brief creation of mass and even gravity, popping in and out producing a higher energy field than what it should be, it is called a false energy state.
We can see this in nature even; super cooled water will not freeze, even at levels well below 0c. Icing on airplane wings is caused by super cooled water hitting the wing and suddenly freezing. Liquid water at -20c (for example) is in a false energy state, poised to attain its real, lower energy status.
So the vacuum was in a state of false energy, its vacuum energy was much like the super cooled water, all that was needed was an airplane wing to drop that false energy state.
Imagine this false energy state is like a ball bearing inside a shot glass, rolling up and down the sides, back and forth like a skate boarder on a half pipe. Because of the deepness and the sheer sides of the shot glass, the ball bearing rolls up and down at speed. Next to this shot glass is a small bowl – it is shallower and its sides are a gentle gradient. For the ball bearing, the bowl is the lowest energy state. Much like the quantum field, the ball bearing is at a high energy state, a false energy. Try as it might the ball bearing cannot break over the rim; there is not enough energy available to get it over the rim and into a lower energy state. In the quantum world though, strange things can happen. Instead of rolling over the rim, the ball bearing tunnels though the side of the glass and appears in the bowl. This effect is called quantum-mechanical tunneling. Because of the uncertainty principle we cannot be sure where the particle is at any given time and its probability wave extends beyond its current energy state within the shot glass and into the lower, preferable state. Because lower energy state is a preferable state then there is more probability of the particle being in a low energy state as opposed to gaining more energy in order to cross over the rim. This sounds abstract but without tunneling the sun wouldn’t shine nor would your computer chip be working as it is right now.
So we have this virtual particle, like all the infinite others popping about around it however this one’s probability wave tunnels it through the barrier and into a lower energy state. Then it inflates like a bubble as the expansion decreases the energy within the expanding section increasing the new, lower energy universe in size in repulsion to the field it grew from. While this is happening quantum fluctuations are still occurring and, as the inflation continues, the quantum fluctuations are expanded; inflated with space itself causing clumps of the stuff that makes our universe aggregate. After 10-32 seconds the new” bubble universe” disconnects from the field, leaving no trace neither here nor there. Big Bang cosmology then takes over.
New theories in Inflation tend towards a different imagining. Instead of a shot glass, imagine a sombrero. At the top point there is a depression where our ball bearing sits, surrounded on all sides by the lower ring of the sombrero. When Inflation occurs in this model there is no need for quantum tunneling, the ball bearing instead simply rolls down the slope, inflating the universe as it heads for the lower energy state.
A way to imagine this as a larger picture is to think of a boiling pot of water – the water represents the vacuum, clear and transparent but filled with energy. The element at the bottom which heats the water represents the fluctuations. The bubbles in the water are the inflation of universes – seemingly from nothing. Some expand greatly and others immediately fall back again within, what some see, as a larger multiverse.
Inflation is important as it solves the Horizon problem, the flatness problem and also answers why the universe is homogenous with clumps of matter all in one without having to introduce anything. Unlike other cosmological theories, we can actually test some aspects of inflation using quantum mechanics. We know that quantum tunneling is a real phenomenon; we also know that virtual particles are created. Recent studies have measured the energy being created, seemingly from nothing before disappearing again. A leading theory suggests that 73% of the universe's energy is actually held within empty space (this is in fact one of the leading theories on what Dark energy is – one I subscribe to myself).
Virtual particles are popping in and out of existence all around us and, like in the field before Inflation began, empty space has a weight. In fact, recent studies and observations have shown that in empty space, between the electron and the nucleus – everywhere, particles and are being created and returning back into the vacuum continuously. Most of the weight and energy of the universe is thought to be held in inside the vacuum, inside this false vacuum state. This has curious aspects in that inflation of new universes, budding off others could be happening right now, in front of you – even inside of you, without anyone ever being the wiser.