Cosmology

The sensitivity of inflationary models to Planck-suppressed operators motivates modeling inflation in string theory. The case of high-scale inflation is particularly interesting both theoretically and observationally. Observationally it yields a gravity wave (B mode polarization) signature, and theoretically it requires a large field excursion which is particularly sensitive to UV physics. I\'ll present a simple mechanism derived recently in collaboration with A. Westphal for obtaining large-field inflation, and hence a gravitational wave signature, from string theory. The simplest version of this mechanism, arising on twisted torus compactifications of string theory, yields an observationally distinctive version of chaotic inflation with a potential proportional to the 2/3 power of the inflaton, falsifiable on the basis of upcoming CMB measurements. This mechanism for extending the field range arises widely in string compactifications, though in all cases it requires sufficient symmetry to control the corrections to the slow-roll parameters. I will finish by describing further developments in this direction.

The atomic hydrogen gas left over from the Big Bang was affected by processes ranging from quantum fluctuations during the early epoch of inflation to irradiation by the first galaxies at late times. Mapping this gas through its resonant 21cm line serves a dual role as a powerful probe of both fundamental physics and astrophysics. Current cosmological data sets (such as galaxy surveys or the microwave background) cover only 0.1% of the comoving volume of the observable Universe. 21cm observations hold the potential of mapping matter through most of the remaining volume. Radio observatories are currently being designed and constructed with this goal in mind. The three-dimensional 21cm maps could potentially set unprecedented statistical constraints on the power spectrum of cosmic density fluctuations and its gravitational growth with cosmic time. The reduced uncertainties could allow for precise measurements of fundamental parameters, such as the mass of the neutrino or the equation of state of the dark energy (from acoustic oscillations in the 21cm power spectrum), and will test generic predictions of cosmic inflation for deviations of the density fluctuations from scale invariance and gaussianity. The measured gravitational growth of the fluctuations with cosmic time would constrain the nature of the dark matter or alternative theories of gravity.

After a brief introduction, where I review the properties of the \'good Dark Matter candidate\' and the status of accelerator, direct and indirect Dark Matter searches, I will show that a conclusive identification of DM particles can most likely be achieved only through a \'multidisciplinary\' approach, that combines together different detection techniques. I will place special emphasis on the upcoming Large Hadron Collider, and on the gamma-ray satellite GLAST (scheduled for launch on June 3, i.e. the day after the talk...)

The CERN Large Hadron Collider is nearing completion. Both the ATLAS and CMS experiments are being completed, and the accelerator is proceeding through cool-down to cryogenic temperatures in preparation for first beam. The timescales and prospects for first beam, collisions and physics will be discussed, and the early physics program of the LHC high PT experiments reviewed.