No-scale supergravity inflation: A bridge between string theory and particle physics?

Abstract

The plethora of recent and forthcoming data on the cosmic microwave background (CMB) data are stimulating a new wave of inflationary model-building. Naturalness suggests that the appropriate framework for models of inflation is supersymmetry. This should be combined with gravity in a supergravity theory, whose specific no-scale version has much to commend it, e.g. its derivation from string theory and the flat directions in its effective potential. Simple no-scale supergravity models yield predictions similar to those of the Starobinsky R + R 2 model, though some string-motivated versions make alternative predictions. Data are beginning to provide interesting constraints on the rate of inflaton decay into Standard Model particles. In parallel, LHC and other data provide significant constraints on no-scale supergravity models, which suggest that some sparticles might have masses close to present experimental limits.

Relaxed Supergravity

“…The η problem [7] is an example of such a difficulty 2 . No-scale supergravity [8] may be a solution to the η problem because the corresponding F-term potential can exactly vanish, i.e. V F = 0.…”

“…In fact, the gravitino mass term "−3e G " plays a critical role in the no-scale cancellation. Interestingly, one can easily have such no-scale structure through a logarithmic Kähler potential of the volume modulus fields and constant superpotential in string theory [8,9,10]. However, certain choice of superpotential may spoil the "exact" cancellation of the F-term potential yielding a remnant as shown in Eq.…”