As usual the announcement of the recipients of the Nobel Prizes for 2011 happened with almost no fanfare in the mainstream press. As I did last year, here’s a summary of this year’s winners.

• The Physics prize goes to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess for a discovery that all astronomy buffs now knows: that the universe is not only expanding but the rate of expansion itself continues to accelerate. This was worked out by studying distant supernovae and noting the Doppler Effect on its light as the distance between the supernovae and the Earth increases. Today, physicists still have no real explanation of why the universe continues to expand at an increasing rate, indicating that some force, other than the residual energy of the Big Bang, is pushing space apart. This is what physicists label “dark energy” for now while they search for a better understanding of what is going on.
• The Chemistry prize goes to a single individual, Daniel Shechtman, for a discovery that will make mathematicians as well as chemists proud. While studying a slice of aluminium-manganese alloy, he inadvertently stumbled on quasicrystals a heretofore unknown form of materials. Normal crystals consist of atoms that are packed together in a symmetrical and repeating pattern. Shechtman however discovered a type of crystal that have orders of symmetry that  that were previously thought to be impossible, allowing them to fit together in such a way that the pattern never perfectly repeats itself. In 2D form, mathematicians know this as Penrose tiling, named after the British mathematician Roger Penrose, who first formally formulated this form of geometry. Islamic artists however have been known to use this sort of motif in their work for centuries. Today, quasicrystals are used in many areas of materials science, such as the liquid crystals in display screens and some types of steel.
• The Physiology prize goes to three persons who all worked on the immune system though the discoveries are not directly related. Bruce Beutler and Jules Hoffmann discovered a protein-binding mechanism that helps the immune system recognize invaders and trigger a defensive response. Ralph Steinman discovered the dendritic cell, which he found helps to activate T-lymphocytes, which play a role in the immune system’s ability to adapt to different types of threats. The prize underwent a bit of controversy this year as the rules state that Nobel Prizes may not be awarded to deceased individuals. As it turned out, Steinman passed away just before he received the news that he had been awarded the prize. As the Nobel committee was unaware of his death at the time of their decision, the decision was allowed to stand.
• The Economics prize goes to Thomas Sargent and Christopher Sims. Both economists worked on uncovering cause and effect in macroeconomics, in particular addressing how to incorporate changing expectations by rational actors in a macroeconomic model. Sargent showed how businesses and households learn about economic conditions and adjust their expectations accordingly and how this in turn should be taken into account of within macroeconometrics. Sims developed the statistical tool of vector autoregression that is used to work out the effects of how a change in economic conditions affects both the supply and demand curve in complex ways.
• The Literature prize goes to a Swedish poet, Tomas Tranströmer, who is not well-known outside of his home country. His oeuvre, which is not large, is characterized by the committee as being economical and granting fresh access to reality. This is the first time that a poet has won the prize since 1996.

As usual, detailed information on the recipients and explanations of their work can be found on the official Nobel Prize website.