No Ambulance Needed: Unexpected Diboson Excess at LHC Keeps Super-Symmetry Alive

The grapevines are buzzing again – and there is again a sliver of hope. Many believe that Super-Symmetry (SUSY), the purported next step in high-energy physics is almost dead, with the LHC, the big boy on the block, finding no signatures of it as yet. Just this week, however, a paper and a presentation at the prestigious global International Conference on High Energy Physics (ICHEP), happening in Valencia, Spain, aims to correct that situation a bit. They shout ‘Stop the Ambulance‘, employing a nice play on words.

An event consistent with the Higgs decay. It can decay into two Z-bosons, which can give the four muons (red lines in the pic).
An event consistent with the Higgs decay. It can decay into two Z-bosons, which can give the four muons (red lines in the pic).

What’s left to know?

Their claim is simple – we have seen an excess number of events, unexpected if the known Standard Model of Particle Physics is all there is. The Standard Model (SM) forms the backbone of known particle physics, and it has been rigorously verified over decades. With the discovery of the Higgs, almost exactly 2 years ago, it is believed to the ‘complete’. Physicists are now looking into the chinks in the armour of the SM, hoping to find a crack here or a broken seam there through which they can glimpse some new physics. So far, the armour has been imposing and flawless, but there are still checks to be done.

One of the most important particles in the SM is the W-boson. It can either be positive or negative. All processes producing these bosons are well-known and calculated. Basically we know how they are produced quite accurately. So far, all measurements confirm our theoretical calculations. However, this group reports on an excess of diboson production seen by the LHC, which basically means that there are more pairs of W-bosons being created than expected from the SM.

There’s more

What is more intriguing is that the single W-boson production rates, the single Z-boson (a companion to the W, but neutral in charge), WZ production and a pair of Z-boson productions rates have matches with the predicted SM rates. The pair of W-bosons just don’t seem to comply – and the discrepancy isn’t too small. What more, the discrepancies are in the same direction for both the CMS and ATLAS collaborations of the LHC.

The authors of the paper have taken up a simplified model, consisting of the SM and a few SUSY particles and have showed that their model fits the data way better than the SM. Their model has a light stop, winos and binos.

That said, the data is still quite inadequate to claim anything solid. Everyone is eyeing the 2015 restart of the LHC runs. Let’s hope that SUSY survives till then.

Discovered: Liquid Water Beneath Surface of Saturn’s Moon Enceladus

Saturn’s moon Enceladus may have liquid water hidden away at its South Pole. Or so say NASA’s Cassini, the spacecraft dedicated to map out different aspects of the beautiful planet Saturn.

Enceladus, as mapped by Cassini. Look at the craters and the ravine-like structures.  Photo Courtesy: NASA/Cassini
Enceladus, as mapped by Cassini. Look at the craters and the ravine-like structures.
Photo Courtesy: NASA/Cassini

Enceladus is a tiny moon of Saturn, barely measuring 500km across. It’s been a curious object for many years, since it shone brightly in reflected sunlight, the surface being covered by a white layer of water-ice (meaning, frozen water). The surface is fractured into various patterns, indicating erosion in the past. Much of the surface is cratered; objects, mostly small rocky bodies, pulled in by Saturn’s gravity slam into Enceladus. A spectacular display is seen at the South Pole of the moon, where giant plumes of liquid and gaseous water rise, after penetrating the fractured surface. These shine in the Sun’s rays and also provide material to Saturn’s E-ring.

Cassini picks up the plumes of water vapour and liquid water towards the south pole of the moon.  Photo Courtesy: NASA/Cassini
Cassini picks up the plumes of water vapour and liquid water towards the south pole of the moon.
Photo Courtesy: NASA/Cassini

How Cassini Discovered Water

Cassini has made several flybys past Enceladus, in 2010 and in 2012, mapping its surface in great detail as it flew less than 100 km from the surface. It has also mapped the gravitational field of the object and this is what led to the discovery of a possible liquid water reservoir right beneath the surface. During these flybys, the trajectory of Cassini changes slightly due to the gravitational field of the moon. Being a light object, Cassini is quite sensitive to local gravitational fields, and corrects its path accordingly. This means that one can use this information to map out the gravitational field of the moon. If there is a major concentration of mass, like a large mountain, we can feel a positive addition to the field, while a hollow will show up in a negative way.

Artists' impression of what Enceladus might look like on the inside.  Image Courtesy: NASA/Cassini,
Artists’ impression of what Enceladus might look like on the inside.
Image Courtesy: NASA/Cassini,

Cassini, mapping the gravitational field in the South Pole of Enceladus, found that there was a mass deficit on the surface, but a large mass excess abut 30-40 km below the surface. This ‘subsurface anomaly’, meaning a deviation from the standard mass distribution found below the surface, is, ‘compatible with the presence of a regional subsurface sea’, says the paper on the subject.


The next obvious question is this: does this sea of liquid water harbour life? The answer is that we don’t know. For a long time, Jupiter’s Europa was a happy hunting ground for alien-hunters; this status might be usurped by Saturn’s tiny Enceladus. A good, though quite a bit technical, answer can be found in a paper co-authored by Carolyn Porco, head of the Cassini mission here. This, however, predates the recent Cassini discovery and hinges its arguments on the plumes of liquid water seen emerging from the South Pole.

A nice video on the subject by JPL and NASA can be found here:

NASA’s Telescope Detects Strongest Hint Yet of Dark Matter Particles from Galactic Center

NASA’s Fermi Gamma Ray Telescope has spotted something which should interest every physicist. Looking at the heart of our Milky Way galaxy, Fermi has unequivocally showed a bright gamma-ray glow. Scientists have then removed all known gamma-ray sources and, while it removes quite a bit of the contributing source, it still leaves a bit unaccounted for. We don’t know what’s causing this excess gamma ray glow. Given that gamma rays are some of the most energetic radiations known, it is unlikely that they are caused by some thermal event. The best explanation at the moment is that something unknown – some unknown particles – are annihilating each other and giving off these radiations. The question is then, what are these particles.

The signal that Fermi saw. On the right, we have the same signal with all the known sources removed. A strong glow still remains - we don't know what that is!
The signal that Fermi saw. On the right, we have the same signal with all the known sources removed. A strong glow still remains – we don’t know what that is!

These particles ought to be quite heavy; the gamma ray emission hints at their mass. One very likely explanation for these particles is that they are Dark Matter particles. Humorously called WIMPs, short for Weakly Interacting Massive Particles, these heavy particles are likely candidates for Dark Matter (DM). In other words, the gamma ray lines seen by NASA’s Fermi telescope are because of DM annihilation.

Dark Matter 101

But what is DM you ask? DM is conjectured to be a type of matter beyond which we already know about, responsible for about 27% of the total mass-energy of the Universe. It was first hypothesized by Fritz Zwicky to explain why some galaxies can actually rotate as fast as they do without breaking apart. He surmised that there must be some invisible form of matter, which does not have any electromagnetic interaction, and thus doesn’t give off light, but are massive and, thus, can interact via the gravitational force. Today that conjecture stands on firmer grounds, with observations of known deviation from expected rotation speeds spanning thousands of galaxies. DM has been indirectly hinted at by many experiments such as the CoBE, WMAP and the recent Planck experiment, which all map out the distribution of Cosmic Microwave Background Radiation in our Universe. A host of other experiments also detect strong anomalies which can be easily explained away by the DM hypothesis.

In other words, we are quite sure that DM exists.

The mass-energy estimate of the Universe as given by the Planck experiment.  Courtesy: Planck/ESA
The mass-energy estimate of the Universe as given by the Planck experiment.
Courtesy: Planck/ESA

The clinching evidence would be to a actually detect it and one way is to let it annihilate each other into two known particles. These two particles then annihilate and produce some radiation which we can detect. The heavier the DM particles, the more energetic the final radiation; thus by knowing the final states, we can figure out the masses of the initial particles.

It is to be noted that no-one is jumping up and saying that DM has been found. While the evidence is highly suggestive, it’s not yet clinching, because, as most scientists like to say, not enough data has been collected. They would conservatively err on the side of mundane humility rather than make a mistake making an extraordinary claim.

Keep watching this space for more.

The official paper:

The following video was released by NASA:

Human Genes Cannot Be Patented, Says A Landmark US Supreme Court Ruling

A Supreme Court ruling may change the landscape of genetic research forever. The US Supreme Court ruled that human genes cannot be patented, in a landmark hearing giving a huge victory to the American Civil Liberties Union (ACLU) while disheartening Myriad Genetics. The issue was the BRCA genes, the mutations on which are believed to be responsible for increasing the susceptibility to breast cancer.

The Contention

Myriad Genetics had claimed patent over this gene, claiming to have ‘invented’ this gene, which meant that all treatments and even detection of the BRCA gene would entail a royalty to Myriad. This would’ve raised the costs of detection, costs and treatment of breast cancer significantly. In a beautiful moment when calm commonsense prevailed, the Supreme Court struck down the ‘invention’ claim by saying:

Myriad did not create anything. To be sure, it found an important and useful gene, but separating that gene from its surrounding genetic material is not an act of invention… Myriad found the location of the BRCA1 and BRCA2 genes, but that discovery, by itself, does not render the BRCA genes … patent eligible.


The Consequences

This, of course, means huge losses for the pharmaceutical industries, but it’s the cancer patients who stand to benefit in the long run. The costs of detection tests and their subsequent treatment would come down, as no one company would have the monopoly on the technology and research. As it should be!

Myriad’s defence even involved a ludicrous ‘baseball’ argument, in which they argued that the “baseball bat doesn’t exist until it is isolated from a tree. But that’s still the product of human invention to decide where to begin the bat and where to end the bat”. This analogy fails on many levels and the court noted that merely deciding the start and end points of a gene sequence doesn’t deserve a patent. Official ruling said:

The baseball bat is quite different. You don’t look at a tree and say, well, I’ve cut a branch here and cut it here and all of a sudden I’ve got a baseball bat. You have to invent it.

However, Myriad did get part of the pie, when the court ruled that the Myriad can have its patent on the invention of the cDNA – complementary DNA – which is actually a synthetic form of DNA.

“The lab technician unquestionably creates something new when cDNA is made,” said the court.

The ruling here:

Is The Kepler Space Telescope Entering Its Last Days?

A darling of NASA and of the general public, the Kepler Space Telescopes, dedicated to looking at extra-solar planets, may be soon ending its run. A recent hardware failure on the Kepler has led experts to give Kepler just one more year.

Artist's rendition of Kepler Space Telescope
Artist’s rendition of Kepler Space Telescope

Kepler had four reaction wheels, which keep Kepler steady and able to focus unerringly at distant stars and planets. Kepler really needs three wheels to achieve this job, but has four just in case. Earlier, in July, 2012, one of these wheels had broken down, putting engineers slightly on the edge. Kepler, however, continued to function as well as it always did.

On 9th May, engineers found Kepler in automatic safe mode, since something was wrong. To their dismay, they found that one of the three remaining wheels had malfunctioned. Kepler’s days seemed numbered.

Kepler stares at faraway world, shielding its own cameras from the glare of the Sun. However, light from the Sun hits the craft (and, in fact, fuels it) and exerts pressure on it, called radiation pressure. No matter how small this is, this is enough to throw Kepler a bit off its line of sight. And this is where the wheels come in, ensuring that the photons are not the nuisance that they really are.

Engineers are scrambling for ideas to save Kepler. They are trying to use the boosters to compensate for the reaction wheels, but this won’t give the stability that Kepler enjoyed. Its planet watching days may be over.

NASA Detects A Burst Stronger Than Any Seen Before

A recent blast from a dying star has left astronomers, gaping in awe at the sheer magnitude. A distant eruption, classified now as a Gamma Ray Burst (GRB) and named GRB 130427A, has now set the record for the brightest GRB ever. NASA’s Swift satellite and Fermi-LAT, both specialized for the gamma ray part of the spectrum, have recorded this mind-boggling event. Julie McEnery, project scientist for NASA’s Fermi-LAT, said that this was a “shockingly, eye-wateringly bright” burst.

An artist's impression of a GRB. Note the strong jets on either side of the collapsing star. (Courtesy: wikimedia commons)
An artist’s impression of a GRB. Note the strong jets on either side of the collapsing star. (Courtesy: wikimedia commons)

What are GRBs?

Gamma Ray Bursts are the most powerful explosions known to mankind that occur in the Universe, ranked second right after the Big Bang itself. GRBs occur when an extremely massive star collapses into a massive black hole, and the material falling into the black hole heats up so much that it radiates in the gamma ray region of the spectrum. These jets of gamma rays puncture the material envelope of the dying star and can be detected from a long distance. Unlike smaller supernova (which happen for moderately large stars), GRBs are responsible for throwing out a large amount of energy in the surrounding space, often energizing the gas around and making it glow. The duration for such a burst might last from a few milliseconds to minutes or even hours and the burning embers can often be seen for days and months. We generally count the time for which the radiation energy exceeds the GeV (giga-electron volt) threshold, which is about a billion times more energetic than visible light.


For our present GRB, the GeV radiation lasted for hours and it was observed by Fermi-LAT, a space based gamma ray telescope, for a long time. Even ground based telescopes caught more than a glimpse of the GRB. The Swift satellite caught the first glimpse, as it is designated to do, during one of its rounds. Energetic emissions were recorded by Fermi-LAT, with one of the gamma ray lines having an energy of 94 GeV.

This animation is made by stacking a large number of images taken by the Fermi-LAT satellite from 3 minutes before the burst to 14 hours later. You can clearly see the burst and then the radiation flux drops and plateaus off. The burst then rose in flux again and stayed bright (more then GeV energy lines were abundant) over several hours. (Courtesy: NASA/DOE/Fermi-LAT collaboration))
This animation is made by stacking a large number of images taken by the Fermi-LAT satellite from 3 minutes before the burst to 14 hours later. You can clearly see the burst and then the radiation flux drops and plateaus off. The burst then rose in flux again and stayed bright (GeV energy lines were abundant) over several hours. (Courtesy: NASA/DOE/Fermi-LAT collaboration)

Apart from the strong gamma emission lines in the spectrum, there are also lines present in the infrared, visible and radio wavelengths. These were detected by ground-based telescopes. The distance of the burst was estimated to be 3.6 billion light years away, which is actually quite small when it comes to GRBs. This falls within the 5% of the closest GRBs ever recorded.

This is exciting and a lot of backup measurements will follow this initial detection.

More info:

When Size Matters: Story of the Incredible Shrinking Proton!

The size of the proton matters in the field of the ultra-small and it seems that no one can agree on the correct value. The answer was long believed to be well-known, but the puzzle seems to be back to haunt the physics community. The proton seems to have suddenly shrunk in size.


How do we look?

The radius of the proton is found out by shooting high energy electrons at it and then finding how it forms a bound state. It’s very much like forming an atom, except that this atom is much smaller than the normal atoms which make up matter. Energetic electrons fired at protons often get bound to the proton, and form a hydrogen-like object. However, since the electron has a lot more energy than the ordinary hydrogen atom electron, it is attached much closer to the proton than the normal hydrogen electron. As a result, the proton can no longer be treated as a point particle, but its spatial extent become important.

So we can form a bound state and then measure the minute transition between energy levels and these now have an imprint of the proton magnetic moment and the proton radius. And thus, the proton radius can be determined.
For a long time, physicists were safe in their determination of the proton radius and their value was 0.8768 femtometers (a femtometer is a millionth of a billionth of a meter, or a meter divided by 10^15). Case closed, right? Wrong…

New experiment

A new experimental result threatens to blow this question of the radius wide open again. The muon is a close cousin of the electron. It has a negative charge and behave very much like the electron in a magnetic field, except that it is 200 times heavier than an electron. Recent experiments shoot these heavy electrons – or muons – at protons and these now form a bound state. The higher mass of the muon (by a factor of 200) means that at same energies, the muon is much closer to the proton (by a factor of 800 million). It can ‘see’ the proton much better and measure the radius to greater accuracy.

However, this has produced a shocking reduction in the accepted value – 0.84087 femtometers – a reduction of 4%. That is huge, well above the experimental uncertainties.

So, what’s going on?

Physicists are not very sure what’s going on. Why should the muon behave any differently from the electron? Is the muon, being closer to the proton experiencing some short range force, other than the usual long ranged electromagnetic and the short ranged weak force, that we just don’t know about? Is a new force of nature at work here? Is there new physics, something beyond the Standard Model of particle physics?

The muon measurements were made by a group of scientists at the Max Planck Institute of Quantum Optics, led by Randolf Pohl. Of course, the crudest explanation to all of this is that the experimentalists simply bungled and got the value wrong. No one’s ruling that explanation out right now, but other avenues are also being explored.

Muon scattering experiments like MuSE will only be ready in a few years, so this debate will continue for some time. When size does matter, we just don’t want it to change.

Hint of Discovery of a Dark Matter Particle – Is It Finally Reality?

“Tantalising hints” is a phrase high energy physicists have a love-hate relation with, and for good measure. Often all major discoveries remain tantalizing hints for a long time, creating a lot of confusion, generating a lot of debates and then either fade away into oblivion or become something so big that history just cannot ignore it. A recent demonstration of this phenomenon was given at the LHC during the hunt for the Higgs, where what remained as a ‘tantalising signal’ for months, grew steadily and offered the LHC physicists their first opportunity to say ‘Hurrah!’ A similar event may be afoot at the giant Super Cryogenic Dark Matter Search (SuperCDMS ) experiment, located deep inside a tunnel in the Soudan Mine in northern Minnesota. There is a ‘tantalizing hint’ of the detection of a particle which might be the elusive Dark Matter particle.

The CDMS detector
The CDMS detector

The recent tidings have excited physicists, as they have detected three events in the detector of a possibly weakly interacting massive particle (WIMP). However, they need more events. The surety of the discovery of these WIMPs is only 99.8 %, which amounts to a wee bit more than what physicists call 3-sigma confidence level. This is at the ‘tantalising hint’ level. At 4-sigma, it gets interesting and only at 5-sigma (which is a massive 99.9997% surety), do physicists say that they have a discovery.

The star is the central value.
The star is the central value.

The mass of the particle is somewhere about 8-10 GeV, which is about 8 to 10 times the mass of the proton. That’s low mass in the context and this particle, if present, should turn up in some of the other colliders and detectors, especially the LHC, in the near future.

Theorists are already busy at work figuring out how all of this fits into their theory. Can a supersymmetric theory, a theorist’s dream for a long time, accommodate the particle of mass 10 GeV? If so, which version and how has that version fared at the LHC?

For now, let this hint promote itself to the level of a discovery – we have seen too many tantalizing signals come and then disappear to be hasty.

Looking at our Universe: What the Planck Results Really Mean

The Universe seems to be just as queer as we could have supposed, or maybe less queer. The results from PLANCK, which came out in their first ever press conference, 15.5 months after the probe was launched, speaks of a Universe described almost entirely by what is known to be the Standard Model of Cosmology. In other words, there is nothing that should startle us, but a lot that should be enlightening and, frankly, quite exciting.

The progress of the Universe through its ages (Courtesy:
The progress of the Universe through its ages (Courtesy:

For cosmology virgins, Planck is a space probe launched into an orbit around Earth designed to pick up the radio and microwave radiations from the whole Universe. By charting out the whole sky, it creates a unique map, a map of the Universe, as seen from the microwave frequency regime, and not the optical regime that we are so used to. The Universe is extremely different in these frequencies from the star-filled Universe we know and love. But these frequencies tell a different tale – one of the early universe and what imprints of that we can see today. The story of Cosmology starts right at the beginning of the Universe, or rather, more accurately 10-32 seconds after it. The Universe underwent a sudden expansion phase, called inflation, and then stabilized, while continuing to expand. The radiation from the inflationary era have got both diluted (i.e. reduced in intensity) and ‘stretched’ (i.e. their wavelengths have increased, leading to a decrease in their energy) due to the expansion of the Universe which is continuing to this very day. So ‘cold’ have these radiations become that we need specialized probes to catch them, their temperature being just 3 K (i.e. 3 Kelvin above absolute zero). The redeeming fact about these strange low-energy waves is that they are everywhere – all over the Universe. They form a kind of ‘background’ radiation and are thus called ‘Cosmic Microwave Background Radiation’ (CMBR), the name being self-explanatory.

The Universe as Planck sees it.
The Universe as Planck sees it.

The theory goes that there arose minute quantum fluctuations in the radiation soup right after the inflationary phase. As the Universe expanded, these expanded, then gravity took over and clumped matter in these pockets of disturbed equilibrium. These manifest as galaxies or clusters we see today – the tiny quantum fluctuations have grown to giant scale. The imprint of these early fluctuations will be found in the radiation seen by Planck.

The Age of the Universe

First big observation – the Universe seems to be just a bit older than we thought it to be – about 70 million years older. So the official age of the Universe become 13.82 billion years, raised from the 13.75 (or 13.77) billion it was assigned earlier.

The constituents of the Universe

It seems that the known constitution of the Universe has changed slightly from previous estimates. The matter percentage of the Universe is slightly higher than what we had known. The constitution of the Universe is mostly unknown to us and we can only put in some percentages on the amount we know and the part we are ignorant about. For example, we know that matter forms a very small percentage, followed by dark matter which forms a large chunk and that dark energy – a strange form of energy responsible for the accelerated expansion of the Universe currently – forms the largest chunk of the matter-energy pie. The earlier estimates have been bettered by Planck which quotes 4.9% ordinary matter, 26.8% dark matter and the rest 68.3% as dark energy. This is a decrease in the estimate for dark energy from previous estimates and an increase in the estimate of normal matter and dark matter. This implies that we know a bit more about the Universe (we only know about the ordinary matter part) and that the Universe is expanding at a slightly less accelerated rate than what we thought. Our ignorance about most of the Universe is only slightly abated.

The Cosmic Recipe before and after Planck results (Courtesy: ESA, Planck)
The Cosmic Recipe before and after Planck results (Courtesy: ESA, Planck)

Closely related to this is the value of the Hubble’s Constant which Planck calculates to be 67.3 +/- 1.2 km per second per megaparsec. This is a big surprise from the earlier value of the Hubble’s constant 71.0 +/- 2.5 km per second per megaparsec. The lower value of the Hubble’s constant means that the Universe is expanding slower than earlier thought.

CMB Spectrum: Cosmic Fingerprint

The whole Cosmic Microwave Spectrum as predicted by theory matches that seen by Planck to very high precision. We see the Universe at very high angular width as well as very narrow width. What Planck says is that at high multipoles, corresponding to very narrow angular width, the data matches experiment exactly. At low values of multipoles, the error bars are large, but Planck has seen as much as can be seen.

The power spectrum of the Cosmic Background Radiation and how well data fits with theory (Courtesy: Resonaances blog:
The power spectrum of the Cosmic Background Radiation and how well data fits with theory (Courtesy: Resonaances blog:

No probe in the future will be able to see at finer resolution, since the limit on resolution is not placed by the instrument anymore, rather by the Universe itself as a whole. Our Universe not only seems perfect, it seems good at hiding possible imperfections as well.

Asymmetry and Anisotropy

Planck gives an asymmetry in temperature over the two hemispheres of the Universe. This is a startling find, but nothing absolutely new. It’s just that Planck has confirmed – at high resolution – something that WMAP had already hinted at.

The Anomalies as seen by Planck. Notice the clear blue and red regions on opposite hemispheres. (Courtesy: ESA, Planck)
The Anomalies as seen by Planck. Notice the clear blue and red regions on opposite hemispheres. (Courtesy: ESA, Planck)

An important point to be made here: The distribution of the fluctuations are exactly random, even though we might not feel it to be so. They pass all tests of randomness. Just to emphasize, the angular distribution of the fluctuations is really exactly random. The fluctuations could have been anywhere and they just happen to be where they are! What is important is that the amplitudes of the fluctuations are not random. The amplitudes – i.e. the real temperature of the fluctuations – are not random and one hemisphere seems to be on the whole hotter than the other. This wasn’t expected! Note that a small patch of sky could’ve been warmer than the other, but this is seeing a whole trend in the temperature – one side is colder and the other hotter – and we have nothing to explain that. In fact, our cherished notions of isotropy of space (I.e. cosmological phenomena and features don’t have a preferred direction) contradict this finding. We have to wait for a verdict on this. There is also a cold spot detected in the Universe – a region of space considerably colder than the other parts. No one knows why this is the case – is it just random or is there some forces at play there?

Let’s look at a couple of more topics, both being a bit more technical.

Neutrino masses and the limit on them:

Planck puts a stern limit on the sum of the neutrino masses – a value of 0.23 eV. This is at a 95% Confidence level and this result is completely consistent with the neutrino mass being zero. However, the phenomenon of neutrino oscillation says that neutrino mass cannot be zero, no matter how small. Planck also says that the number of neutrino species is 3 and no more, well almost. This rules out those elusive sterile neutrinos, the possible fourth species of neutrinos which don’t even interact via weak interaction and their effect is felt only through the gravity that they exert.

Spectral Index and Inflationary Theories

Inflation as a theory receives a major boost from these results. The simplest inflationary models predict that knowing the two-point correlation function would be enough since the whole spectrum of the fluctuations right after inflation can be modelled by a Gaussian. Planck reinforces that. The models also say that spectrum is scale invariant (or ‘conformal’) and Planck shows slight deviation from that. A quantity called ‘spectral index’, ns, quantifies the scale invariance. If ns=1, then the scale invariance is perfect, otherwise there is deviation. Planck gives the value of ns = 0.9603 +/- 0.0073. So inflation is also nearly as simple as we can imagine and all ‘complicated’ models of inflation can be ruled out. So Planck reveals our Universe in details we have never seen before. However, even after looking at the Universe this closely, we find that the Universe is indeed plain vanilla, with a couple of chocolate chips thrown in. People are calling it the MBU or Maximally Boring Universe. Is the Universe really less queer than we thought?

[For more technical references, I refer you to the clutch of papers published by the Planck collaboration. They can be found here: project=PLANCK&page=Planck_Published_Papers]

Neurons Caught in Action: Zebrafish Brain Filmed While Firing Signals

It’s the brain like never seen before. A group of researchers – Misha Ahrens, neurobiologist, and Phillipp Keller, microbiologist from Howard Hughes medical Institute’s Janelia Farm Research Campus, have been able to see individual neurons firing in the brain of a larval zebra-fish, recording activities across the entire fish brain.

And they’ve made a cool video of the whole thing (below).

They have mapped the exact firing pattern for 80% of the 100,000 neurons in the brain, suggesting that, should an upscaling of this mapping be done, the human brain might finally be in the imaging line.

The brain map - taken from the paper (link at the bottom)
The brain map – taken from the paper (link at the bottom)

The Imaging Technique

The imaging technique is ingenious, but theoretically simple. The researchers created genetically modified zebrafish, so that the neurons make a protein which fluoresces when there is a change in the concentration of the calcium ions. Calcium ion concentrations change when a neuron fires, meaning that there will be a small fluorescence when a neuron fires.

Now, a thin sheet of light was sent through the brain and this captures any optical activity in the brain and then records it on a screen. This imaging technique is called ‘light-sheet microscopy’ and the Janelia team was able to upgrade it count at a rate tenfold its original rate. The entire brain of the larval fish was mapped every 1.3 seconds. One whole experiment lasted for 10 hours, generating as much a few terabytes of data.

Ahrens commented on his pet method, explaining why it is so much better than conventional techniques. Available techniques allow one to image at most 2000 neurons at one go, but this one can see the entire circuitry in the brain. As Ahrens puts it:

you don’t need to guess what is happening — you can see it.

There is definitely room for improvement. One would be distinguish between one neuron firing and multiple firings in a short interval. Also, researchers would like to try it on other organisms.

Is the human brain up next? Not for quite some time, surely.

The work appeared here: