The Planck Satellite measurement have increased the accuracy of cosmological observations to a level which allows to constrain cosmological models with unprecedented precision. The aim of this workshop is to discuss the implications of these recent results combined with other (i.e. Planck, but also WMAP, galaxy surveys, SNIa data…) on models that aim at describing the primordial epochs and the origin and formation of large scale structures of the Universe. Continua a leggere Fundamental Issues of the Standard Cosmological Model
Un gruppo di astronomi che si dedicano allo studio delle condizioni fisiche dell’Universo primordiale hanno ottenuto nuovi indizi sui processi di formazione delle prime strutture cosmiche, cioè stelle e galassie, andando ad analizzare la composizione chimica di alcune ‘stelle fossili’ che sono distribuite nelle regioni più esterne ed interne dell’alone galattico.
La ricerca dei modi-B, relativi alla componente della polarizzazione della radiazione cosmica di fondo associata alla propagazione delle onde gravitazionali nella mappa della radiazione cosmica, rappresenta una prova fondamentale che potrebbe dare credito al modello dell’inflazione cosmica. Nonostante i calcoli prevedono una intensità del segnale molto debole, oggi alcuni ricercatori del South Pole Telescope (SPT) hanno pubblicato i dati di uno studio in cui dichiarano di aver rivelato deboli fluttuazioni associate ai modi-B della componente di polarizzazione.
Scientists believe that approximately half a million years after the Big Bang, the Universe began switching from a state of plasma and energy to one where temperatures had dropped to a point where the universe became transparent enough for light to pass through. That light is known as cosmic microwave background (CMB) and is still visible today. Cosmologists studying it have formed the basis of a theory known as inflation, where the Universe came to exist as it does today through a process of very rapid expansion just after the Big Bang. In order to prove that the inflation theory is correct, scientists have been studying minute fluctuations in the temperature of the CMB, they revel fluctuations in density of the early Universe. They also study fluctuations of the polarization of the CMB which is due, it is believed, to radiation being scattered across the Universe by the energy of the Big Bang. Fluctuations in polarization were for a time merely theory, but in 2002, they were actually detected, giving credence to inflation theory. Those fluctuations were given the name E-mode polarizations. Theory has also suggested that there are also B-mode fluctuations in polarization, which are far more subtle, they are thought to describe the rotation of CMB polarization.
Finding evidence of them has been extremely difficult, however, as they exist as just one part in ten million in the CMB temperature distribution. But now it appears the team at SPT has done just that, adding further credence to the inflation theory.
The researchers report that they were able to detect E-mode polarization due mostly to improvements in detector technology. Adding credence isn’t the same as finding proof of a theory, of course, and that’s why scientists believe the detection of E-mode polarizations is so important. Many believe it will ultimately lead to the detection of primordial gravitational waves, immense ripples in spacetime that theory suggests should have come about as a result of the force of inflation. If they can be detected, the theory of inflation would likely become the accepted theory regarding the early formation of the Universe.
arXiv: Detection of B-mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope
- B-mode polarization spotted in cosmic microwave background (physicsworld.com)