If so, I have a question.
Why can’t physicists use the standard model to calculate exact decay constants for radionuclides, thus alleviating us geologists from having to measure them?

I am not sure if the study of the CMBR is your area of cosmological expertise, but I was wondering, what is your opinion of the conclusions reached in a recent paper titled “On the apparent lack of power in the CMB anisotropy at large angular scales” by Amir Hajian of Princeton University? (astro-ph/0702723) When the COBE data was released one of the puzzling unexpected aspects of the full-sky CMB maps was the absence of long wavelength fluctuations; this odd feature, odd in the sense that it is at odds with inflationary theory, also exists in the WMAP data (or does it?). In other words, if the Universe is infinite and homogeneous, as inflation predicts, it is awfully improbable that we should not be seeing long wavelengths in our tiny portion of the cosmos.

But now, as reported in the above mentioned paper, it appears that there is no deficit in large scale power in the full sky maps, and the explanation for the apparent lack of large scale power is that masking the sky near the galactic plane creates this appearance.

Shantanu– Measuring the “speed of gravity” is like measuring the “speed of blue”; the concept just doesn’t apply. You can talk about the speed of propagation of gravitational radiation — in that case, the prediction of GR is unambiguous that gravitational waves propagate at the speed of light. Arguing about whether some particular measurement is really probing the “speed of gravity” is a waste of time; the important thing is that no observation yet performed is inconsistent with the predictions of GR.

It ends with, “Quantum information cannot be completely hidden in correlations: Implications for the black-hole information paradox” appears in the latest Physical Review Letters.

Sorry for being so dumb on this, but just what does ‘information’ mean in this context?

You said: “I don’t know if it’s likely or not, but it’s certainly promising.” However, the dictionary.com definition of the word promising in the context you are using it is “giving favorable promise; LIKELY to turn out well.”

Talk of favorite models implies that we really don’t have any evidence guiding us toward a strong “suspect” for the dark matter. By analogy, if when a dectective is asked how likely is it that the murderer will be found and he responds by saying each detective has his favorite suspect, then we would rightly conclude that the police force really has no clue who committed the murder. So, are you saying that we really don’t have any clue what the dark matter is? and, if so, how can it be “certainly promising?”

“Eternal inflation and its implications”, by Alan Guth.
http://arxiv.org/abs/hep-th/0702178

It’s a great Introductory article.

I have no idea what’s practical and what’s not. Is getting stuff out of the Sun practical? There’s no obstacle in principle to getting stuff out of a neutron star.

Is there a way to determine how much normal matter is now stuck in black holes, neutron stars and other highly dense entities?

On a related note, once a neutron star forms, can you ever get anything out of it again? (practically, not theoretically)?

Thanks for doing this, by the way.

I would like to bring to your attention three interesting papers which discuss the prospects for us being able to detect dark matter in the near future. Each paper focuses on the most popular dark matter candidate WIMPs (Weakly Interacting Massive Particles). The first paper (astro-ph/0609126) takes all that we know e.g. the constraints from collider experiments and cosmology and does a state of the art bayesian analysis of the detectability of neutralino dark matter. The main result of this paper is well summarized in a probability bar graph which shows that there is a 95% probability that the particle cross section is between 10^-8 pb and 10^-10 pb. For reference, the two most sensitive direct searches are the Xenon10 and CDMS II, and during 2007, as discussed in the second paper (astro-ph/0611124), will just begin to probe the 10^-8 pb cross section. It will take 1 ton detectors to reach 10^-10 pb.

The last paper (hep-ph/0611065) discusses how there is a relationship between the ability of the Tevatron and the LHC to produce the heavy Higgs and the ability of dark matter direct detection experiments to detect the WIMPs. According to the paper, if the heavy Higgs is found in the LHC collider, and many people think it will be, then dark matter will likely be found in the near future by direct detection experiments. Of course, this study makes some assumptions also known as “priors”, but the take home message, at least to me, is that it seems likely that we will solve the dark matter mystery soon.

What do Sean and company think? Is it likely that the dark matter will be found soon?

http://arxiv.org/abs/astro-ph/0401547