New Limits on the Big Bang

[bystander]

New Limits on the Big Bang
Sky and Telescope - August 19, 2009

The first few moments of the Big Bang — according to most theories of how it actually worked — should have produced gravitational waves in the fabric of space-time that are still rippling through all of space today. But by now they should be extremely weak, and no detector has had the capability to detect them at any plausible predicted level.

Gravitational waves, according to Einstein's general relativity, are produced by any large masses violently changing speed. A "gravitational-wave backgound" is expected from the violent early moments of the Big Bang, rather like the cosmic microwave background that fills the sky with radio waves from the early universe. In recent years the microwave background has yielded the universe's age, density, composition, and much else to high precision.

But while the microwave background originated about 380,000 years after the Big Bang, the gravitational-wave background should come directly from events in the first one minute. The waves' strength, spectrum of frequencies, and other details should tell about the behavior of the universe during that brief, critical time.

The researchers' results, published in Nature for August 20th, set an upper limit on the gravitational-wave background by combining data from LIGO and a similar detector in Europe named Virgo. The limit also puts constraints on the existence of "cosmic strings": immensely long, line-like flaws in space-time that, theorists have proposed, might also be left over from the universe's very beginning.

New research limits Big Bang's output of gravitational waves
Astronomy.com - August 19, 2009

Lack of Gravity Waves Puts Limits on Exotic Cosmology Theories
Space.com - August 19, 2009

[harry]

G'day bystander

It seems as though that the both links you posted assume that the BBT is a fact and than proceed to assume the data to fit. We sometime forget that the BBT although being the standard model is still theoretical.

Regarless gravitational waves has been on the books for many years, particularly during phase transition, from normal matter to Neutron matter and also to quark matter.

This paper may be of interest.

http://arxiv.org/abs/0907.3075
A new possible quark-hadron mixed phase in protoneutron stars

Authors: G. Pagliara, M. Hempel, J. Schaffner-Bielich
(Submitted on 17 Jul 2009)

Abstract: The phase transition from hadronic matter to quark matter at high density might be a strong first order phase transition in presence of a large surface tension between the two phases. While this implies a constant-pressure mixed phase for cold and catalyzed matter this is not the case for the hot and lepton rich matter formed in a protoneutron star. We show that it is possible to obtain a mixed phase with non-constant pressure by considering the global conservation of lepton number during the stage of neutrino trapping. In turn, it allows for the appearance of a new kind of mixed phase as long as neutrinos are trapped and its gradual disappearance during deleptonization. This new mixed phase, being composed by two electric neutral phases, does not develop a Coulomb lattice and it is formed only by spherical structures, drops and bubbles, which can have macroscopic sizes. The disappearance of the mixed phase at the end of deleptonization might lead to a delayed collapse of the star into a more compact configuration containing a core of pure quark phase. In this scenario, a significant emission of neutrinos and, possibly, gravitational waves are expected.

[bystander]

http://arxiv.org/abs/0907.3075
A new possible quark-hadron mixed phase in protoneutron stars

Authors: G. Pagliara, M. Hempel, J. Schaffner-Bielich
(Submitted on 17 Jul 2009)

Maybe I'm just being dense, but I fail to see what this paper has to do with the research at LIGO and Virgo, other than it mentions gravity waves.

[Chris Peterson]

It seems as though that the both links you posted assume that the BBT is a fact and than proceed to assume the data to fit.

That's how normal science works. You start with an assumption- in this case that the Universe started with the Big Bang, and then you test this assumption, or certain limits of this assumption, by observation.

There is no issue of "facts" other than the facts of the observations themselves. The right way to read this is very simple, and utterly correct: if there was a Big Bang, it was defined by parameters in some range R2, which is narrower than the range R1 that was possible before these new observations.

The initial observation about the Big Bang is reasonable, since it is consistent with the best available theory. But there's nothing that prevents somebody else from starting with a different assumption and using these new data to either support or reject that assumption. Indeed, I'd be surprised if these data don't place limits on certain alternate theories as well.

[Chris Peterson]

Maybe I'm just being dense, but I fail to see what this paper has to do with the research at LIGO and Virgo, other than it mentions gravity waves.

The paper is extremely dense; you are not. It has nothing at all to do with the topic at hand.

[bystander]

... Indeed, I'd be surprised if these data don't place limits on certain alternate theories as well.

They have already mentioned such a constraint on "cosmic strings".

[Chris Peterson]

... Indeed, I'd be surprised if these data don't place limits on certain alternate theories as well.

They have already mentioned such a constraint on "cosmic strings".

Well, cosmic strings aren't really an alternative to the Big Bang in general, although they may be part of BB theories other than L-CDM. But it is true that whenever you get new information about how nature works, it can trickle down and influence all sorts of existing theory- sometimes in very unexpected areas.

[harry]

G'day bystander

The point being is:

How do gravitational waves come about?

Hello Chris, I kind of agree with your response, there is science logic behind it.

[harry]

G'day from the land of ozzzzzzz

On the topic of Gravitational Waves and their probable origin. By understanding these events maybe we can understand the initial events predicted by the BBT.

TOPICAL REVIEW: The gravitational-wave signature of core-collapse supernovae
Mar-09
http://adsabs.harvard.edu/abs/2009CQGra..26f3001O
http://adsabs.harvard.edu/cgi-bin/nph-d ... db_key=AST

We review the ensemble of anticipated gravitational-wave (GW) emission processes in stellar core collapse and postbounce core-collapse supernova evolution. We discuss recent progress in the modeling of these processes and summarize most recent GW signal estimates. In addition, we present new results on the GW emission from postbounce convective overturn and protoneutron star g-mode pulsations based on axisymmetric radiation-hydrodynamic calculations. Galactic core-collapse supernovae are very rare events, but within 3 5 Mpc from Earth, the rate jumps to 1 in ~2 years. Using the set of currently available theoretical gravitational waveforms, we compute upper-limit optimal signal-to-noise ratios based on current and advanced LIGO/GEO600/VIRGO noise curves for the recent SN 2008bk which exploded at ~3.9 Mpc. While initial LIGOs cannot detect GWs emitted by core-collapse events at such a distance, we find that advanced LIGO-class detectors could put significant upper limits on the GW emission strength for such events. We study the potential occurrence of the various GW emission processes in particular supernova explosion scenarios and argue that the GW signatures of neutrino-driven, magneto-rotational, and acoustically-driven core-collapse SNe may be mutually exclusive. We suggest that even initial LIGOs could distinguish these explosion mechanisms based on the detection (or non-detection) of GWs from a galactic core-collapse supernova.

[bystander]

Yes, Harry, any number of things may cause gravitational waves; the collapse of super massive stars into supernova, the infall of mass into black holes, the orbit of super massive binary stars around their barycenter, or even the orbit of the planets about the sun. All that is required is an asymmetric acceleration of a massive body. However, none of the afore mentioned are the topic of this discussion. This discussion was about the setting of an upper limit on the strength of gravitational waves left over from the beginning of the universe, kind of a KGB (Kosmic Gravitational wave Background).

[bystander]

How do gravitational waves come about?

The asymmetric acceleration of mass.

Hello Chris, I kind of agree with your response

Is this becoming a habit?

[harry]

G'day Bystander.

Darn!!!!!!!!!

When someone is right what do you do?

I know lets push him over a cliff.