The measured abundance of helium in the universe (about 25% of all normal matter) suggests that there is about one proton for every 1010 photons. This in turn suggests that at some earlier phase of the universe an almost equal number of protons and anti-protons existed and gradually annihilated, but that because of some fundamental asymmetry (at the level of one part per ten billion) in the way that the weak nuclear force treats matter and antimatter, protons but not anti-protons survived to the present time.
The standard model of particle physics usually enshrines this asymmetry in the form of "CP violation," a mathematical convention concerning the interaction of particles in which one imagines what happens when the charge of all the particles is reversed (charge conjugation, abbreviated as C) and the coordinates of all particles is reversed (the parity operation, or P).The standard model is successful in predicting how CP violation works out in the decay of K mesons or B mesons (see Update 600) but not so good at predicting where the abundance of baryons (protons plus neutrons) comes from.
Phil Schewe | Physics news update 614
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For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
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For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
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Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
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