Posts tagged ‘BVG theorem’

September 14th, 2014

Podcast: What Kinds of Multiverses are There?

by Max Andrews

Podcast: https://soundcloud.com/sententias/eavesdropping-ep25-levels-of-the-multiverse

Contemporary physics seem to indicate that there are good reasons, theoretically and physically, for an idea that there is a plurality of worlds. This concept has come to be understood as the multiverse. The multiverse is not monolithic but it is modeled after the contemporary understanding of an inflationary model of the beginning of this universe. Max Tegmark has championed the most prominent versions of the multiverse. Tegmark has made a four-way distinction.

Levels of the Multiverse

November 20th, 2013

When Asked if I was Surprised to Find Evidence for a Young Earth

by Max Andrews

Several years ago I was taking a [required] course that teaches creationism. I have a few comments about the course I’ll keep to myself [as in it shouldn’t be in the university] but I think most readers know where I stand on university and academia issues and standards. I was asked the question, “Is it surprising that scientific evidence supports a young earth perspective?”

My response is simply that this is a loaded question.  I don’t think I can say there’s no evidence for a young earth; however, I find the record of nature to support the proposition that the universe is old (billions of years) by overwhelming evidence.  There is hardly any evidence for a young earth, if indeed there is any at all.

July 12th, 2012

The Multiverse Directory

by Max Andrews

I have gathered together all my posts relevant to the multiverse. Since this is one of the biggest topics on the blog, I thought having all the posts gathered into one place would make finding the content much easier.

  1. Quantum Entanglement and the Many Worlds Interpretation
  2. Cosmic Darwinism: Evolving Laws of Nature?
  3. A Theological Argument for Many Worlds
  4. Fine-Tuning of the Multiverse Lecture and PPT
  5. The Multiverse and Causal Abstract Objects
  6. An Outline of Tegmark’s Four Levels of the Multiverse
  7. This History of the Multiverse and the Philosophy of Science
  8. The Theological Attraction of the Multiverse
  9. Hugh Everett and the Many Worlds Interpretation
  10. Decoherence
  11. Physical Evidence of the Multiverse
  12. The Multiverse, Fine-Tuning, and Nomic Probabilities
  13. The Exceptions to the BVG Theorem
  14. Loop Quantum Cosmology in the Cosmic Microwave Background
  15. I’m Presenting a Paper at EPS on God and the Multiverse
  16. Plantingan Modal Realism
  17. Nonlocality as Evidence for a Multiverse Cosmology
    read more »

June 18th, 2012

A Fourth Exception to the BVG Theorem

by Max Andrews

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

by Max Andrews

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

by Max Andrews

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.

May 17th, 2012

An Exception to the BVG Theorem

by Max Andrews

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.*

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

An example of this would be found in de Sitter cosmology. In mathematics and physics, a de Sitter space is similar to Minkoswkian spacetime.  It is maximally symmetric and has constant positive curvature. Assume that a spatially infinite universe contracted down to a singularity and then bounced into our present expansion.  In such a case, the universe cannot be said to be, on average, in a state of cosmic expansion through its history since the expansion phase, even if infinite, is canceled out by the contraction phase.  Though this is permissible under the BVG it is not a viable or popular option.

George Ellis, one of the world’s leading cosmologists, has two objections:

February 1st, 2012

Is There Scientific Evidence for Young Earth Creationism?

by Max Andrews

To answer the question, “Is it surprising that scientific evidence supports a young earth perspective?” I would respond saying that I would almost consider this a loaded question.  I don’t think I can find no evidence for a young earth; however, I find the record of nature to support the proposition that the universe is old (billions of years) by overwhelming evidence.  There is hardly any evidence for a young earth, if indeed there is any at all.

Before getting to the geologic record of nature one needs to address the cosmological record of nature (the earth cannot be older than the universe).  I initially gained my interest in cosmology (and I must say I really enjoy discussing cosmology) was the Kalam cosmological argument, which is an apologetic argument for a beginning of the universe.[1]  I’ll put aside the mathematical and philosophical arguments for a beginning of the universe for that would be off topic and I’ll stick with the scientific evidence.  If one were to analyze an extrapolation of space and time then that initial singularity for the universe would take us back 13.73 GYA (giga, billion years ago).  There are many models of the universe such as the steady state, oscillating, quantum fluctuation, and other string theory models that coincide with former.[2]  The most prominent model with the most philosophical, mathematical, and scientific evidence is the standard model (due to cosmic inflation, the big bang).  Prominent cosmologist Paul Davies comments,