Recommended by us: "Is BICEP wrong?"

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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 

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

Paper of the week: Quanto è stabile il fotone?

In questo articolo, pubblicato su Physical Review Letters, viene discussa la stabilità del fotone, testando la possibilità che esso possa decadere. Per fare ciò chiaramente dovrebbe possedere una seppur piccola massa, il chè non è a priori vietato da alcuna legge fisica (a parte qualche piccolo "dettaglio" sulla rinormalizzabilità della teoria, che però può essere risolto).

Ma facciamo un po’ di chiarezza: innanzitutto ciò che potrebbe suonare strano è il concetto di massa del fotone, infatti tutti o quasi tutti sappiamo che il fotone è una particella priva di massa, tuttavia asserzioni di questo tipo in fisica vanno corroborate da risultati sperimentali.

Esistono dei limiti sperimentali alla massa del fotone che possono essere determinati in svariati modi.

Un fotone con una massa non nulla avrebbe degli effetti osservabili, per esempio la legge di Coulomb ne verrebbe modificata e il campo elettromagnetico avrebbe un ulteriore grado di libertà. Se la legge di Coulomb non fosse esattamente valida, allora potrebbe causare la presenza di un campo elettrico all'interno di un conduttore cavo sottoposto ad un campo elettrico esterno. In questo modo è quindi possibile testare la legge di Coulomb con altissima precisione [2]. Un risultato nullo di tale esperimento ha fissato un limite di \(m \lesssim 10^{-14} eV\) [3].

Tune to Planck

There is quite a hype in the corridors around the upcoming presentation of Planck results.

A press conference is scheduled on Thursday at 10am CET and it will be streamed directly from the ESA Headquarters.

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The Planck space telescope was launched in May 2009 to obtain the most detailed map of the oldest light in the universe, the Cosmic Microwave Background (CMB). Several rumors circulate these days about Planck having found several unexpected features of this radiation, which could drastically change our understanding of the Early Universe.

Needless to say, no semiofficial news leaked so far and there's nothing to do but tuning to the ESA streaming next Thursday!