# New valuation of ΛCDM Cosmology by 41 authors...

1. Dec 20, 2015

### grauitate

P.Bull, Y. Akrami, et al. "Beyond ΛCDM: Problems, solutions, and the road ahead" 77 pages + 517 references
arXiv:1512.05356
Written not without humour: e.g. pg. 67:
"As Tom Shanks once said, there are only two things wrong with ΛCDM: Λ and CDM."
" ΛCDM is like Hotel California: it is very hard to leave, and most, if not all, efforts to do so have ended with some insurmountable obstacle."
I'd like to recommend this paper for reading between the years for some discussions in 2016.

2. Dec 20, 2015

### marcus

For balance, I'd suggest reading this paper along with it:
http://arxiv.org/pdf/1002.3966v3.pdf
maybe "the cosmological constant problem" as a "great mystery" needs a little debunking : ^)

3. Dec 21, 2015

### RUTA

I agree with Bianchi and Rovelli that as far as cosmology per GR is concerned, there is no mystery surrounding $\Lambda$, it's simply a constant per Einstein's equations to be measured. We don't have a better theory for cosmology per classical (non-quantum) physics than GR, so they say simply that $\Lambda$ is not a problem for the best classical physics. But, they do acknowledge that it's a problem for whatever quantum physics underwrites GR. They write:

Third, we do not yet fully understand interacting quan-
tum field theory, its renormalization and its interaction
with gravity when spacetime is not Minkowski (that is, in
our real universe). But these QFT difficulties have little
bearing on the existence of a non vanishing cosmological
constant in low-energy physics, because it is a mistake
to identify the cosmological constant with the vacuum
energy density.

This is what bothers those who are bothered by non-zero $\Lambda$. Particle physics gives us an argument for $\Lambda = 0$, but nothing for the value currently measured. While that's not a problem for "low-energy physics," it's certainly a problem/mystery for quantum physics.

4. Dec 21, 2015

### George Jones

Staff Emeritus
Where?

5. Dec 21, 2015

### RUTA

6. Dec 21, 2015

### RUTA

7. Dec 23, 2015

### Chronos

A point along the lines of those by Bianchi and Rovelli in http://arxiv.org/abs/1002.3966 might be - why is the matter anti matter assymmetry of the universe so tiny [1 ppb]. Could lamba be somehow related?