Wednesday, November 09, 2011

New constraints on cosmic strings from the South Pole Telescope

Cosmic strings are stable, one dimensional objects of high energy density that might populate our universe. Cosmic strings can arise in quantum field theories and would form networks that extend throughout the universe. They were discussed three decades ago as a possible origin of cosmological structures, but fell out of favor when that was not compatible with data.

Cosmic strings received renewed interest however since they might appear also in the early universe if superstring theory is taken into account. No longer thought to be necessary to explain present day observational cosmology, the question is now how tightly constrained a possible contribution of cosmic superstrings is and if they may become observable in the soon future, when looked for in the right place with the right means, thus providing a long sought for hint that string theorists are on the right track. For more details, see my earlier post.

A recent paper has now put forward new constraints on the density of such string networks
    Cosmic String constraints from WMAP and SPT
    By Cora Dvorkin, Mark Wyman and Wayne Hu
    arXiv:1109.4947

The brief summary is that the have taken into account new data from the South Pole Telescope and not found anything.

The somewhat longer summary is that cosmic string networks leave an imprint in the anisotropy of the Cosmic Microwave Background (CMB) by actively generating perturbations, even after recombination. Most importantly, they act as lenses for the CMB light, which makes a contribution to the spectrum at large multipole moments or small angular size respectively. See here for an explanation of the CMB anisotropies. The recent measurements from the South Pole Telescope have now much improved the previously available data at large multipole moments. The new data is however perfectly consistent with a string-free universe, which allowed the authors of the above paper to derive improved and tighter constraints on models with cosmic strings.

They are careful to point out however that their constraints directly apply only to the most straigh-forward model of cosmic string networks, and that there are more complicated models (in which cosmic strings are merely meta-stable or there are different types of strings) for which the constraints would look different. In any case, this is yet another negative result for the phenomenology of string theory.

14 comments:

Plato said...

Hi Bee,

As you know any foundational approach has to be theoretically consistent with what we see in nature too. Yes I understand that.

Now one is moved to see QFT in a particular sense always comes back too...particle reduction within the scope of the model with which one points too? Let's say the large structure scale of the universe has a topological pleasing view from outside the universe(?) how could one ever apply such a mode to the vastness of the program with which string's form a one dimensional prospect and deliver?

I am thinking about this more. My views have not change in regard to seeing in the context of the Chladni plates. These aided my understanding of what Wayne Hu accomplished for me. These demonstrate "a view" outside the universe?:) However displeasing this is to cosmologists.:)

Best,

Plato said...

Here is larger image.

You see, they needed a new explanation on how one can look at this map? My view has not changed, but becomes more applicable, just as much as one tries to avoid cosmic strings?;)

It is "topologically" pleasing too.

Best,

bizdiets! tovarich said...

It sure forces one to wonder whether or not all this string stuff is nothing more than institutionalized mathturbation.

Uncle Al said...

30 years of mathematical physics have zero empirical validation. No primordial stringies adds another nail to the coffin. Add IceCube. A decade of Super-Kamiokande's 50 kt of water observed no SUSY-demanded proton decay. Proton half-life was "recalculated." IceCube is a km^3 of ice, about 9x10^6 kt of water (remember ice density), 18,000 times larger. An IceCube day is up to 49 Super-K years. Noboy has seen a proton decay candidate. The neutrinos are there.

Wesley Crusher physics is not a pretty sight.

Robert L. Oldershaw said...

It is said that "nature abhors a vacuum".

Clearly nature also abhors string theory.

However the media and the public continue to gobble it up, as evidenced by Brian Greene's 4-part revival show for aging string theorists and golly-gee zombies.

Sigh.

Rhys said...

It would be really nice to see *something* exotic show up some time soon, either in cosmology, or astrophysics, or collider physics! All these negative results wear one down after a while.

Robert L. Oldershaw said...

But perhaps nature is trying desperately to tell us something important, metaphorically speaking.

David Brown said...

"... yet another negative result for the phenomenology of string theory."
What might string theory predict?
Is Milgrom’s MOND correct, and, if so, is some form of superstring theory the only plausible way to explain MOND?
http://www.astro.umd.edu/~ssm/mond The MOND pages (McGaugh)
http://www.astro.uni-bonn.de/~pavel/kroupa_cosmology.html Pavel Kroupa: Dark Matter, Cosmology and Progress
Can string theory explain the following numerical approximations?
.728**(1/64) = .99505206...
(8/5) * log(1.221/.652) = 1.00381...
(5/3) * log(.652/.357) = 1.00385...
((13.1) * (pi /180)) - (2/27) pi * (1 - 1/(5 pi**2)) = .000643267...
((2.4) * (pi /180)) - (2**(-3/2)) * (1/27) pi = .000750097...
((.2) * (pi /180)) - (1/32) * (1/27) pi = -.000145444...
(1 - .728)/.728 - 3/8 = -.001373626...
http://en.wikipedia.org/wiki/Lambda-CDM_model
http://en.wikipedia.org/wiki/Standard_Model

N said...

@ rhys

well OPERA (if confirmed) is certainly something along these lines

uair01 said...

Is getting rid of string theory as difficult as getting rid of Berlusconi? Or of Goldman Sachs?

Note:
I'm one of that "public" that you say loves string theory. But I don't ...

Robert L. Oldershaw said...

Ahhh, a black swan, perhaps?

Yes, some people like their science testable and at least somewhat connected to physically observed reality.

Rhys said...

@N
At this stage, I'm keeping half an eye on the OPERA-related shenanigans, but I feel that the experimental result is very unlikely to survive further tests.

Plato said...

Hello Robert,

Yes Black Swann....not the movie:)

a higher dimensional version of the Pringle's potato chip. Brian Greene, The Fabric of the Cosmos, pg 483, Para 2, line 29

Figure 5 below is nice too.

IN their figure 2. Hyperbolic space, and their comparative relation to the M.C.Escher's Circle Limit woodcut, Klebanov and Maldacena write, " but we have replaced Escher's interlocking fish with cows to remind readers of the physics joke about the spherical cow as an idealization of a real one. In anti-de Sitter/conformal theory correspondence, theorists have really found a hyperbolic cow." See:Solving quantum field theories via curved spacetimes by Igor R. Klebanov and Juan M. Maldacena

If you can think in relation to orbitals cosmologically written you can think of cosmic strings too?:)Look at the science behind it and you will understand what I mean in context of the larger picture supplied in relation to the universe as geometries hidden. Not Tegmarks soccer ball?;)

Best,

Plato said...

Oh Robert,

Statistics are important.

Best,