Tuesday, May 13, 2014

Recommended by us: "Is BICEP wrong?"


Blockbuster Big Bang Result May Fizzle, Rumor Suggests

The biggest discovery in cosmology in a decade could turn out to be an experimental artifact—at least according to an Internet rumor. The team that reported the discovery is sticking by its work, however.
Eight weeks ago, researchers working with a specialized telescope at the South Pole reported the observation of pinwheel-like swirls in the polarization of the afterglow of the big bang, or cosmic microwave background (CMB). Those swirls are traces of gravitational waves rippling through the fabric of spacetime a sliver of a second after the big bang, argue researchers working with the Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) telescope. Such waves fulfilled a prediction of a wild theory called inflation, which says that in the first 10-32 seconds, the universe underwent a mind-boggling exponential growth spurt. Many scientists hailed the result as a "smoking gun" for inflation.
However, scientists cautioned that the result would have to be scrutinized thoroughly. And now a potential problem with the BICEP analysis has emerged, says Adam Falkowski, a theoretical particle physicist at the Laboratory of Theoretical Physics of Orsay in France and author of the Résonaances blog. The BICEP researchers mapped the polarization of the CMB across a patch of sky measuring 15° by 60°. To study the CMB signal, however, they first had to subtract the "foreground" of microwaves generated by dust within our galaxy, and the BICEP team may have done that incorrectly, Falkowski reports on his blog today.
To subtract the galactic foreground, BICEP researchers relied on a particular map of it generated by the European Space Agency's spacecraft Planck, which mapped the CMB across the entire sky from 2009 until last year. However, the BICEP team apparently interpreted the map as showing only the galactic emissions. In reality, it may also contain the largely unpolarized hazy glow from other galaxies, which has the effect of making the galactic microwaves coming from any particular point of the sky look less thoroughly polarized than they actually are. So using the map to strip out the galactic foreground may actually leave some of that foreground in the data where it could produce a spurious signal, Falkowski explains. "Apparently, there is something that needs to be corrected, so at this point the BICEP result cannot be taken at face value," he tells Science.
Continue to read on Science 

See also http://resonaances.blogspot.fr/2014/05/is-bicep-wrong.html

Monday, May 5, 2014

Radiazione Cherenkov: non si smette mai di imparare! La svista nel programma di divulgazione scientifica Cosmos.

Recentemente ho scritto un articolo riguardo al programma televisivo di divulgazione scientifica “Cosmos: a spacetime odyssey” trasmesso su National Geographic Channel (in Italia è trasmesso sul canale 403 di Sky) e da FOX. Nella sesta puntata della serie intitolata “Dove tutto si crea” (“Deeper, Deeper, Deeper Still” invece il titolo inglese [1]) si parla, tra le altre cose, di supernovae, e dei neutrini ed antineutrini emessi in queste spettacolari esplosioni stellari (per rivedere lo spezzone relativo alle supernovae clicca qui e guarda dal minuto 30 in poi, ma vale la pena di guardare tutta la puntata). In questo precedente articolo, di cui consiglio la lettura prima di continuare la lettura di quest’ultimo, mi sono soffermato nell’analisi dell’incredibile ricostruzione, realizzata con l’ausilio della computer grafica [2], della rivelazione di queste particelle emesse a seguito dell’esplosione di supernova.