Witam,

On Tue, 6 Jun 2006, Bartosz Lew wrote:

Is this something new ? The peper is like from one year ago.

No, but i hadn't seen it before.

...

Kn"odlseder et al. (2005) seems to be the main "discovery" article of the INTEGRAL/SPI results.

It has some very nice pictures - especially Figs 4, 5 and 7 - here i've put the closed links, but the figures are in the astro-ph versions too, of course:

Fig 4 http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img62.gif

Fig 5 http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img63.gif

Fig 7 http://www.edpsciences.org/articles/aa/full/2005/38/aa2063-04/img108.gif

We may soon be able to say that Fig.~4 was the "first picture of invisible matter" ;).

well, it's a picture of what's left of it: electrons, positrons ... and protons, neutrinos, etc.

I didn't have time to read this carefully, but what are the principles of the measurment giving hint on variation of fine structure constant ?

http://arXiv.org/abs/astro-ph/0507142

IIUC (if i understand correctly):

* introduction LDM hypothesis to explain INTEGRAL/SPI => mass estimated < 100 MeV => "scalar particle" coupled to light Z' boson

* sections 2, 3, 4 lead to:

* 5.1 "scalar particle" coupled to light Z' boson AND "scalar particle" coupled to heavy fermion

* 6.3 there is some small difference f(10^{-11}) [the function f is not given] between alpha measured by the Quantum Hall experiment

http://en.wikipedia.org/wiki/Quantum_Hall_effect

and a "theoretical" estimate made assuming the standard model of p.p. including QED and the results of the "g-2" muon experiments related to supersymmetry testing:

http://en.wikipedia.org/wiki/Supersymmetry#Muon_g.E2.88.922_experiment

The authors say that this difference could be due to different precision levels in the QH versus the experiments contributing to the QED "theoretical" estimate.

Equality between the two is obtained for m_LDM \sim 3-9 MeV.

In other words: the QH and g-2 experiments give different results for alpha. The difference is not (yet) statistically significant, but a light scalar coupled to a heavy particle, needed for the LDM hypothesis, would give this difference for m_LDM \sim 3-9 MeV. (The real mass might be higher since this assumes smooth distribution of matter in the DM halo, ignores the fact that some part of the emission might be from point sources, etc.)

So improvements in the QH effect experiments could support the LDM hypothesis and explain the present possible discrepancy in alpha estimates.

This is, coincidentally(?), roughly on the same order of magnitude as the alpha evolution claims in quasar absorption systems, since the QSO claims were of order 10^{-6} or over \sim 5 billion yr or so, and if convert this to 8kpc = 3000yr then we get

delta(alpha)/alpha \sim 10^{-12} between the Sun and the GC.

However, the last i remember of the QSO abs sys alpha evolution claims they were no longer looking interesting (one of Srianand's papers is pretty convincing - look in shape-univ and/or cosmo-torun archives... :). In any case, a more precise calculation would be needed to see if these really are on the same scale or whether i've rounded off too many orders of magnitude.

BTW, the estimate of the inner part of the MW DM profile is quite tight: * section 5.2 \gamma \gtapprox 1.03\pm 0.04

Again, clustering, contamination, etc. make this a lower limit only.

pozdr boud

...

Ascasibar et al 2005 has some very interesting conclusions - apart from the continued validity of LDM as only (so far) viable explanation, they say:

...

One consequence is that the value of the fine structure constant \alpha should differ from that recommended in the CODATA (Committee on Data for Science and Technology). This is a very strong test for the LDM scenario and an additional motivation in favour of experiments measuring \alpha directly. Our results finally indicate that an accurate measurement of the shape of the dark halo profile could have a tremendous impact on the determination of the origin of the 511-keV line and vice versa.

Both of these are very good for showing that evidence should build up either for or against the LDM hypothesis. :)

pozdr boud

Kn"odlseder et al. (2005) http://arXiv.org/abs/astro-ph/0506026 http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?bibcode=2005A%26A...441..51...

Ascasibar, Y et al. (2005) http://arXiv.org/abs/astro-ph/0507142 http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?bibcode=2006MNRAS.368.1695A...

hi all,

On Fri, 9 Jun 2006, Bartosz Lew wrote:

...

In other words: the QH and g-2 experiments give different results for alpha. The difference is not (yet) statistically significant, but a light scalar coupled to a heavy particle, needed for the LDM hypothesis, would give this difference for m_LDM \sim 3-9 MeV. (The real mass might be higher since this assumes smooth distribution of matter in the DM halo, ignores the fact that some part of the emission might be from point sources, etc.)

still it's elusive to me, but if I understand correctly you say only about two different , and possibly giving different results, methods of measuring alpha. where is the part about it's evolution ?

The LDM article says nothing at all about evolution of alpha.

and the alpha is made of three fundamental physical constants: due to change of which one is the hypotetised evolution ascribed to ?

It's not about evolution. It's about using two different experiments and different sets of physics assumptions. From what i understand, the QH experiment requires less physical assumptions than the g-2 experiment, but (at the moment) is less precise. The g-2 experiment is more precise, but requires assumptions of QED (standard model of pp).

If we add in the hypothesised pp explanation for LDM, which goes beyond the standard model of pp, then the two experiments come into agreement because the derived value of alpha from g-2 is modified by the difference from the standard model.

...

So improvements in the QH effect experiments could support the LDM hypothesis and explain the present possible discrepancy in alpha estimates.

This is, coincidentally(?), roughly on the same order of magnitude as the alpha evolution claims in quasar absorption systems, since the QSO claims were of order 10^{-6} or over \sim 5 billion yr or so, and if convert this to 8kpc = 3000yr then we get

delta(alpha)/alpha \sim 10^{-12} between the Sun and the GC.

hmm, so this is about the evolution but, this is a different experiment.

i'm not so convinced by alpha evolution, see the following paragraph:

...

However, the last i remember of the QSO abs sys alpha evolution claims they were no longer looking interesting (one of Srianand's papers is pretty convincing - look in shape-univ and/or cosmo-torun archives... :). In any case, a more precise calculation would be needed to see if these really are on the same scale or whether i've rounded off too many orders of magnitude.

well, anyway it's interesting enough to read more about over a morning coffee :))

Well, there was also something which came up during discussions at the cosm-pl meeting a few weeks ago. Just as a century ago, particle physics seemed to be nearly complete with everything made of protons, electrons, neutrons and four fundamental forces, and there was just a few minor problems such as the infrared catastrophe and the Michelson-Morley experiment, it could be that the explanation for nbDM is a whole bunch of different particles - so maybe both DAMA/NaI and INTEGRAL/SPI correctly reveal two of the main constituents of nbDM. And from what i understand from Ascasibar 2005, the \sim 6-7 MeV particle would have to interact with both a light Z' boson and a heavy particle, implying at least 3 particles present in significant densities in the DM halo.

So we might end up with a whole new zoo of astronomically significant particle populations... ;)

pozdr boud