### The bidimensional motions of a heavy metal moshing

During the APS March Meeting 2013, Matthew Bierbaum with Jesse Silverberg, James P. Sethna and Itai Cohen from Cornell University, presented a curious study about the heavy metal mosh pits: studing the people during the moshing, the researchers find two types of collective motions:
mosh pits, in which participants collide with each other randomly in a manner resembling an ideal gas, and circle pits, in which participants run collectively in a circle forming a vortex of people.
The results are published on arXiv (Collective Motion of Moshers at Heavy Metal Concerts):
Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gas-like state called a mosh pit and an ordered vortex-like state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.
(via Lucia Marino)

### The circle of life

An electron encountered a positron: they are inexorably drawn towards each other, but their combination is intended to be fatal, and from their union remains only a photon, traveling... and traveling... and traveling... and occasionally it disappears, it decomposes into an electron and a positron. These, however, are futile images, as long as they do not possess enough energy to go away, to far away from each other.
Until the next waltz.
The image (via Quantum Diaries) represent a Feynman's diagram about the electron-positron annihilation and a next pair production. In the middle of the diagram, there is the auto energy of the photon, and it is named loop, and the diagram, loop diagram.
Read also: Let’s draw Feynman diagrams! | Feynman diagrams (pdf)

### The boson, the spin and the graviton

Some days ago, ATLAS has been released a draft about the spin of the new boson. The decay channels studied are the fab four: $H \rightarrow \gamma \gamma$, $H \rightarrow WW^*$, $H \rightarrow l\nu l\nu$, $H \rightarrow ZZ^* \rightarrow 4l$. The idea is combining data from the four channels in order to understand the spin of the new boson, in detail to distinguish between two cases: spin 0 ($J^P = 0^+$), and so a boson compatible with the Standard Model, and spin 2 ($J^P = 2^+$), that it could be connected with a model (arXiv) that represents a light coupling between the Standard Model's fields and the hypothetical graviton.
These the ATLAS' conclusions:
The data are in good agreement with the expected distributions of a $J^P=0^+$ particle while the graviton-inspired $J^P=2^+$ model, that is expected to be produced dominantly via the gluon fusion process, is excluded at more than 99.9% conﬁdence level.
We could say that it starting the elimination process of the models that would lead the research of the new physics beyond the Standard Model for the next years. A good luck to all of them, but we don't forget the key role of the Standard Model, that is in some sense confirmed by this last draft from ATLAS.

### Turmoil in the heavens

This one-page comic story published on Race to the Moon #2, that is now in public domain, is referred to an old theory proposed by Heinrich Wilhelm Matthäus Olbers, a german astronomer:
His bold hypothesis of their origin by the disruption of a primitive large planet, although now discarded, received countenance from the finding of Juno by Harding, and of Vesta by himself, in the precise regions of Cetus and Virgo where the nodes of such supposed planetary fragments should be situated.
The hypothetical planet, instead of Polis like suggested in the comic, was named Phaeton by Yevgeny Leonidovich Krinov. Olbers' model is today substituted by the accretion model.

### Ted Turner Interviews Carl Sagan

Carl Sagan and Ted Turner discuss the issues that are vital to the survival of our species on earth. Sagan explains the benefits of our space program, the fascinating possibility of time travel, and our search for life on other worlds.