Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,082 questions , 2,232 unanswered
5,353 answers , 22,786 comments
1,470 users with positive rep
820 active unimported users
More ...

  What current alternatives are there to the standard concordance model of cosmology?

+ 5 like - 0 dislike
2215 views

The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and an inflationary period at very early times.

What alternative theories are also consistent with current observational data?

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user ihuston
asked Nov 2, 2010 in Theoretical Physics by ihuston (25 points) [ no revision ]

3 Answers

+ 3 like - 0 dislike

What alternative theories are also consistent with current observational data?

There is an alternative line of thought according to which inhomogeneities in large-scale structure, known as voids, are responsible for the "perceived" or "apparent" acceleration on large time scales. This viewpoint was first advocated by Celerier and Inoue and Silk, among others.

A numerical comparison of WMAP3 data with LCDM and non-Lambda model is done here. It is found that the likelihood of the non-Lambda model is comparable to that of the LCDM one. However such a fit requires a very low Hubble rate ( $ \sim 0.40 - 0.45 h^{-1} $ ) compared to the widely accepted $ \sim 0.73 h^{-1} $, and also requires a significant amount of negative curvature.

These shortcomings aside, a very recent work by Hael Collins allows an analytic approach to the problem, albeit in a simplified setting. To quote from the abstract:

This example provides an illustration of a universe where the inhomogeneities can affect its average expansion rate; and its simplicity allows a condition to be derived that tells when their presence should begin to become important. Since the averages of the non-uniform parts of the metric and the matter density grow faster than their uniform parts, the average expansion rate accelerates with the advent of the era governed by the inhomogeneities. (emphasis mine).

So as they say, you free to "worship at the church of your choice" :-D

[Update: Nov. 14, 2010]

... but if these (1, 2) references to papers by David Wiltshire have anything to say about the question of "apparent" vs. "actual" cosmic acceleration, it would appear that many in the cosmology community have been worshipping the false god of "dark energy" !

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user user346
answered Nov 13, 2010 by Deepak Vaid (1,985 points) [ no revision ]
+ 2 like - 0 dislike

Penrose's Conformal Cyclic Cosmology‎ is such an example. There is late time acceleration due to Lambda, but no inflationary period in the beginning. The late universe is equated to the beginning (of the next big bang cycle) through a conformal factor which maintains the physics.

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user Sklivvz
answered Nov 3, 2010 by anonymous [ no revision ]
To what extent has this been compared to observational data?

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user j.c.
It does make some predictions regarding the distribution of irregularities in the CMB. Basically black holes in the previous aeon should show up as circular patches of colder or hotter radiation. Some such irregularities have been found but more investigation is needed.

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user Sklivvz
+ 0 like - 0 dislike

Prof. Alex Mayer has proposed a new cosmology that matches observables and which does not require dark energy. Google "Alex Mayer" (his website is the first hit) and then first review the "An Introduction to the New Cosmology" talk he gave in September. You can also download a preview of his new book.

This post imported from StackExchange Physics at 2014-04-01 16:48 (UCT), posted by SE-user Dave
answered Nov 14, 2010 by anonymous [ no revision ]

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysics$\varnothing$verflow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...