The standard model of Cosmology invokes the idea of Inflation to explain why the Universe is flat, as well as other problems.

During Inflation, the Universe undergoes an extremely rapid, exponential expansion, as illustrated by the blue band in the plot to the left. This rapid expansion stretches out the radius of curvature of the Universe, pushing it towards flatness.

   Inflation predicts a nearly-invariant spectrum for the primordial density fluctuations, a prediction that has now been confirmed by observations. These fluctuations are the seeds that eventually grow into galaxies and the other structures we see today.

  The rapid stretching of space-time during Inflation should lead to a cosmic background of gravitational waves, with wavelengths comparable to the size of the Universe. These gravitational waves have been called the “smoking gun” of Inflation, and were one of the first

predictions of Inflation models.  However, they are yet to be observed. Detecting these “inflationary gravitational waves” would conclusively prove that Inflation occurred.  

  The most-promising way to detect these gravitational waves is through the unique imprint they would leave in the polarization pattern of the cosmic microwave background. Searches for the Inflationary gravitational waves is one of the key science goals of all the experiments we work on in the Observational Cosmology group at Melbourne.