## Posts tagged ‘Borde-Vilenkin-Guth Theorem’

January 2nd, 2015

## Legitimate Models for an Infinite-Past Universe

The Borde-Guth-Vilenkinb Theorem states that any universe, which has, on average, a rate of expansion greater 0 that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

You can listen to the podcast version of this with greater detail via the Eavesdropping Podcast.

April 26th, 2013

## Exceptions to a Finite Universe

The Borde-Vilenkin-Guth Theorem states that any universe, which has, on average, a rate of expansion greater 0 that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

1. First Exception: Initial Contraction (Havg<0) … (The average rate of the Hubble expansion is less than zero)

• Main Problem: Another problem this raises is that this requires acausal fine-tuning.  Any attempt to explain the fine-tuning apart from a fine-tuner is left bereft of any explanation.

2. Second Exception: Asymptotically static (Havg=O)

• Main Problem: The exception is that it does not allow for an expanding or evolutionary universe.  This model cannot be true.  The best evidence and empirical observations indicate that the universe is not static; rather, it is expanding and evolving.  This might have been a great model under Newton but not since Einstein’s field equation concerning the energy-momentum of the universe.

December 10th, 2012

## Q&A 1: Kalam and The Flying Spaghetti Monster

Hey Max,

I guess since I requested the Q&A section, I’ll start it off!

I recently had a conversation with an atheist in which I walked him through the Kalam Cosmological Argument. This inevitably led into a conversation about what criteria a “first cause” must meet. It was difficult for me to explain, and for him to understand how God exists as a necessary being, or out of His own nature.

The atheist resorted to a version of  “Flying Spaghetti Monster” argumentation, in which he said, “How do we know that the first cause wasn’t a giant pink unicorn, or that two universes didn’t just mate and form ours?”. For obvious reasons, his argument is absurd. But what’s the best way to explain the concept of the first cause, and why it couldn’t be a “giant pink unicorn”?

Thanks a lot,

Richie Worrell (USA)

Richie,

I’m always amazed at some of the philosophical lunacy some atheists come up with. The mockery of using phrases like “flying spaghetti monster” or a “giant pink unicorn” weren’t originally developed in response to the kalam. They were developed in response to intelligent design suggesting the designer could be a spaghetti monster. I recall Dawkins using it several times and it has gained popularity in response to the ontological argument.

Nonetheless, let’s accept his flying pasta, pink unicorn, and sexual universes for the sake of discussion. Let’s recap the the kalam argument:

1. Whatever begins to exist has a cause of its existence.
2. The universe began to exist.
3. Therefore, the universe has a cause of its existence.

June 19th, 2012

## The Exceptions to the BVG Theorem

The Borde-Vilenkin-Guth Theorem states that if any universe, which has, on average, a rate of expansion greater than zero then that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

1. First Exception: Initial Contraction (Havg<0) … (The average rate of the Hubble expansion is less than zero)

• Main Problem: Another problem this raises is that this requires acausal fine-tuning.  Any attempt to explain the fine-tuning apart from a fine-tuner is left bereft of any explanation.

2. Second Exception: Asymptotically static (Havg=O)

• Main Problem: The exception is that it does not allow for an expanding or evolutionary universe.  This model cannot be true.  The best evidence and empirical observations indicate that the universe is not static; rather, it is expanding and evolving.  This might have been a great model under Newton but not since Einstein’s field equation concerning the energy-momentum of the universe.

June 18th, 2012

## A Fourth Exception to the BVG Theorem

The Borde-Vilenkin-Guth Theorem states that any universe, which has, on average, a rate of expansion greater 1 that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

Time reversal at singularity

Example: Aguirre-Gratton

(Regarding BVG): The Intuitive reason why de Sitter inflation cannot be past eternal is that in the full de Sitter space, exponential expansion is preceded by exponential contraction.  Such a contracting phase is not part of standard inflationary models, and does not appear to be consistent with the physics of inflation.  If thermalized regions were able to form all the way to past infinity in the contracting spacetime, the whole universe would have been thermalized before inflationary expansion could begin.  In our analysis we will exclude the possibility of such a contracting phase by considering spacetimes for which the past region obeys an averaged expansion condition, by which we mean that the average expansion rate in the past is greater than zero: Havg > 0. (Borde, Guth, and Vilenkin 2003, p1)

June 15th, 2012

## A Third Exception to the BVG Theorem

The Borde-Vilenkin-Guth Theorem states that any universe, which has, on average, a rate of expansion greater 1 that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

For a greater context please see the first exception to the BVG theorem, which is Initial Contraction (Havg<0).

The third exception: Infinite Cyclicity (Havg=0)

Example: Baum-Frampton “phantom bounce”

These models suggest that the universe goes through a cycle in which it grows from zero (or non-zero) size to a maximum and then contracts back to its starting condition.  The average expansion rate would be a pure zero.

June 14th, 2012

## A Second Exception to the BVG Theorem

The Borde-Vilenkin-Guth Theorem states that any universe, which has, on average, a rate of expansion greater 1 that system had to have a finite beginning. This would apply in any multiverse scenario as well.  There are four exceptions to the theorem.*

For a greater context please see the first exception to the BVG theorem, which is Initial Contraction (Havg<0).

The second exception: Asymptotically static (Havg=O)

Example: asymptotically static universe is an emergent model class.

An asymptotically static space is one in which the average expansion rate of the universe over its history is equal to zero, since the expansion rate of the universe “at” infinity is zero.  The problem is that we observe expansion today and if at any moment there is expansion then the Havg must be greater than 0.