Cosmological perturbations post-Planck - wrap up (TToD)

I'm very sorry. As I wrote last week, we just hosted a conference here in Helsinki. I wanted to cover it as the conference happened and I just didn't have the combination of time and mental energy to do so. I won't be covering it in any detail retrospectively either because I need to get on with research. Nevertheless, this blog is slightly more than a hobby for me, it is also slightly ideological, so I will try to work out how to do it all better next time and try again then (this will be the annual theoretical cosmology conference "COSMO" in early September).

Here's a summary of some of the more interesting aspects that I'll quickly write up, starting with some closure concerning the topic I was halfway through in my last post...

David Lyth, the curvaton and the power asymmetry

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CPPP 13

from Blank On The Map

This week I am attending this workshop in Helsinki. The focus of the workshop is on re-evaluating theoretical issues in cosmology in light of the new data from the Planck satellite. 

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Inspiring Science: The viruses that made us

Viruses make their living by breaking into cells and using the machinery and energy in the cell to reproduce. Once inside, some viruses immediately hijack the cell and make copies of themselves which burst out into the world to infect new cells. Other viruses take a staid approach, though. Instead of taking over the cell, they quietly slip a copy of their genes into its DNA. When the cell divides, it copies the newly acquired viral genes along with the rest of its genome. It’s a better deal for the virus, since all of the cell’s descendants will be carrying viral genes which can eventually come out of hiding to commandeer the cell and replicate. A really lucky virus is one that finds itself inside an egg cell. Getting into the DNA of a single cell means getting copied into all of its daughter cells, but getting into the DNA of an egg cell means getting copied into every cell in the organism that grows from the egg…and from there into all of the organism’s offspring. Lucky viruses that succeed in pulling off that trick can still break out and cause trouble, but they can also become integrated into their host’s genome; instead of struggling to reproduce, they can then just kick back and enjoy the ride while we lumber along, making copies of them whenever we make new cells or have children.

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An inconsistent CMB?

from Blank On The Map

When the Planck science team announced their results in March, they also put out a great flood of papers. You can find the list here; there are 29 of them, plus an explanatory statement.

Except if you look carefully, only 28 of the papers have actually been released. Paper XI, 'Consistency of the data', is still listed as "in preparation". Now, what this paper was supposed to cover was the question of how consistent Planck results were with previous CMB experiments, such as WMAP. We already knew that there were some inconsistencies, both in the derived cosmological parameters such as  the dark energy density and the Hubble parameter, and in the overall normalization of the power seen on large scales. We might expect this missing paper to tell us the reason for the inconsistencies, and perhaps to indicate which experiment got it wrong (if any). The problem is that at present there is no indication when we can expect this paper to arrive – when asked, members of the Planck team only say "soon". I presume that the reason for the delay is that they are having some unforeseen difficulty in the analysis.

However, if you were paying attention last week, you might have noticed a new submission to the arXiv that provided an interesting little insight into what might be going on.

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Inspiring Science: Whose genome is it anyway?

Fifteen years ago it was the stuff of science fiction. Now, you can just swab your cheek, send it to a company and, for only a few hundred euros, have your DNA analyzed. You'll find out about your ancestry and your predisposition towards certain inherited diseases or conditions (from cancer and diabetes to myopia). You'll also learn if you're a 'carrier' -- that is, if you're carrying a gene that won't affect you but might affect your children. You can even get information about more light-hearted issues like whether you're likely to have fast- or slow-twitch muscles or your ability to taste certain bitter flavours. The technology is pretty great, but it also raises some interesting questions which I thought would be worth discussing (especially since I really enjoyed our previous discussion).

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The Trenches of Discovery: stem cells 2.0

Head over the the Trenches to learn about a groundbreaking new method for generating human embryonic stem cells from adults in the treatment of myriad disorders ranging from paralysis to kidney failure.

Read more here.

Inspiring Science: How are humans like ants?

Last year, I wrote about how some ants can find their way home after finding food. They have the remarkable ability to account for all the twists and turns they made while foraging and calculate a direct path leading straight back to their nest. A reader emailed to ask if I thought humans would ever be able to do something similar or to achieve the level of co-ordination shown by ants. This post is based on my reply, where I pointed out several things that humans are amazingly good at doing -- in fact, we do them so well and with such ease that you might be surprised by how difficult they actually are! I've spent a lot of time on Inspiring Science talking about behaviours and abilities which show that other animals aren't just simple automata because I think it's important to make the point that although humans are unique, we aren't special; we're just another species with our own particular tricks for surviving in this world. I'll take a different tack in this post and talk about some of the ways we stand out!

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Inspiring Science: The wasp and the cockroach: a zombie story

The world of parasites is full of incredible tales of manipulation and mind-control as these creatures twist their hosts to their needs. Ever since I first heard of parasitoid wasps, I've been drawn to them by a delicious mixture of schadenfreude and intellectual fascination. (Technically, parasitoids are slightly different from parasites, but that's not important right now.) Some of the examples of manipulation by parasitoid wasps are just wonderfully, horribly macabre. I briefly mentioned the emerald cockroach wasp in a previous post; this time I'll give a few other examples and explain the emerald wasp more thoroughly. Hopefully I'll manage to share some of my excitement about these amazing creatures, which made Darwin once write: "I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae [a group of parasitoid wasps] with the express intention of their feeding within the living bodies of caterpillars, or the cat should play with mice."

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Inspiring Science: Sex, hormones, and the microbiome

The microbiome -- the kilogram of microbes that each of us carries around -- has been shown to be involved in everything from obesity and type 2 diabetes to behaviour and sexual preferences. The composition and effects of the microbiome are very active areas of research, producing results which have challenged the way we think about the evolution and interactions of organisms, including ourselves. In a paper recently published in the journal Science, researchers showed for the first time that the make up of the microbiome differs between the sexes, linking these differences to changes in hormone levels and disease resistance.

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Inspiring Science: Falling faster than gravity

In 2011, a team of physicists at Cornell University in Ithaca, New York showed that when a falling chain hits something (say, a table), it might, contrary to all intuition, speed up and fall faster than it would if it fell freely. By carefully studying its mechanics, they showed how the impact could actually pull the remainder of the chain downwards. As this picture from their experiment shows, they were right. The two strange-looking chains were simultaneously dropped from the same height, but the one on the left, which fell into a pile on a table, fell faster than an identical chain falling past the table.

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The Trenches of Discovery: setting the dials on the human machine

In the trenches this week we're exploring how genes can be turned on or off throughout our lives and how we can consciously influence it to make us happier and healthier. Welcome to the complex world of epigenetics!

Read more in the Trenches.

The Trenches of Discovery: The universe as seen by Planck - Days Three and Fo...

Sorry for the delay on this. I was pretty tired on Friday, travelling home on Saturday and doing physics on Sunday. I figured it would be better to write something with a little more care today.

Those who were following last week will know that on March 21 ESA finally released some cosmological results from the measurements they were taking with the Planck satellite. And, last week, they had their first scientific conference. I decided to blog about this. I had the initial ambition of one post for each day, but the conference dinner on Thursday beat me and all I got out was a brief teaser post. This post now will be comprised of a summary of what I found interesting on both Thursday and Friday, along with a summary of the whole conference at the end.

I hope you enjoy it (and thanks for the feedback during the week).

Highlights

• What has Planck told us about inflation?
• What should we make of Planck vs SPT and Planck vs the local universe?
• What is next for CMB science?

Read the rest at---> The Trenches of Discovery

Unnecessary spin

from Blank On The Map

A few people have asked me why I have not blogged about the recent announcement about, and publication of, results from the Alpha Magnetic Spectrometer, which were widely touted as a possible breakthrough in the search for dark matter.

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The Trenches of Discovery: The universe as seen by Planck - Day one

I am currently attending the ESA run conference "The Universe as seen by Planck". I will be trying to write a summary each day of what I found interesting. To read about my motivation for this, please read yesterday's post. Below is the summary of the first day's talks. I apologise if the posts this week are overly technical. I don't have much time for writing these and this is the best I can do given the constraints. As always, if you don't understand, just ask questions in the comments.

Overall summary

Today was mostly about introducing the Planck experiment and its data. This is the first conference ESA has held since the data was released and in fact the first conference about Planck open to non-Planck scientists like myself at all. Therefore today was actually the first chance for the Planck collaboration to be honest about what their telescope has and has not been able to do. As a result, many of the talks that can lead to the most speculation will not come until tomorrow and Thursday. Still, there were some interesting things to come out of today. For example:

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Planck results: Boring or Anomalous?

The Planck Collaboration released a 29-paper avalanche on the cosmology community just over a week ago, comprising their first set of CMB results. Along with a lot of people in the field (I imagine…), I’ve been letting the implications of this data release sink in for a few days and, on the face of it, the results are a little boring: no detection of non-Gaussianity, no extra neutrino species, “robust support for the standard, six parameter LCDM model of cosmology” — standard, standard, standard.

Continue reading at Lumps 'n' Bumps...

The Trenches of Discovery: The universe as seen by Planck (conference)

The 47th ESLAB symposium. All the cool kids will either be there, or watching it live on the webcast. Are you one of the cool kids?

This week I will be at a scientific conference, organised by ESA. In ESA's words, this conference is "An international conference dedicated to an in-depth look at the initial scientific results from the Planck mission". The conference is taking place in the small Dutch down of Noordwijk. At this conference there will be many people from within the Planck collaboration, who I'm sure will be delighted to finally be able to talk about their work and many people like myself who have spent the last few years eagerly anticipating the Planck collaboration's results.

The conference will have a live webcast here, you should watch some of it.

I will also be blogging during the conference. My goal is to try to write a new post here each day summarising the most interesting talks and discussions from the conference that day.

Read the rest at--->The Trenches of Discovery

Inspiring Science: An amazing critter with seven sexes!

If you’ve never heard of Tetrahymena thermophila, your world is about to get much stranger. This little beauty, a single-celled creature that’s been at the heart of many major discoveries, has seven sexes that can mate with each other! In a paper just published in PLoS Biology, a team of scientists have described the intricate dance of DNA editing and rearrangement which determines the sex of a new T. thermophila.

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Explaining Planck by analogy

from Blank On The Map

Explaining physics to the public is hard. Most physicists do a lousy job of conveying a summary of what their research really means and why it is important, without the use of jargon and in terms that can be readily understood. So it is not particularly surprising that occasionally non-experts trying to translate these statements for the benefit of other non-experts come up with misleading headlines such as this, or this.

Just to be clear: Planck has not mapped the universe as it was in the first tiny fraction of a second. (To be fair, most other reports correctly make this distinction, though they differ widely on when inflation is supposed to have occurred.) I think this is an important thing to get right, and I'm going to try to explain why, and what the CMB actually is.

However, I'm going to try to do so with the help of an analogy. This analogy is not my original invention – I heard Simon White use it during the Planck science briefing – but I think it is brilliant, simple to understand and not vastly misleading. So, despite the health warning about analogies above, I'm going to run with it and see how far we get.

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Planck: All we need is six numbers to describe the entire universe (TToD)

As I'm sure most of the readers of this blog are aware, the Planck data is now out. It turns out I was correct with two out of three of my rumours. I said that the "ISW mystery" was still present, it was. I said that Planck would present ~3\(\sigma\) evidence for non-zero neutrino masses, they did (though, as I suggested in my rumour, only after including information from galaxy clusters Planck has detected). Finally, I said that there would be 2-3\(\sigma\) evidence for some type of "non-Gaussianity", there wasn't. I will duly update my should-I-trust-that-rumour? algorithm in the following way: explicit remarks from Planck members, good rumour; wishful thinking from other theorists, bad rumour.

So what were those results? What big news is there?

The answer is that...

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Inspiring Science: Planck looks back at the first billion, billion, billionth of a second

On Thursday morning, the European Space Agency (ESA) released the results from the Planck mission, a satellite designed to peer back at the earliest fraction of a second of the universe. It’s not our first glimpse of those early moments, but it’s the best look we’ve had to date. While the data from the Planck mission doesn’t overturn our understanding of the universe, it’s a treasure trove for theoretical physicists and brings some exciting questions to the fore.

Continue reading at Inspiring Science...