the “goldstino” superfield $^{3}$. X 2 NL = 0 , (2) X$_{NL}$ = G 2 2 F + √ 2 θ G + θ $^{2}$F. (3) V = e K M 2 ( K − 1 X, ¯ $_{X}$DW ¯ DW − 3 M $_{2}$| W | $^{2}$) (4) D W = ∂$_{X}$ W + 1 M $_{2}$∂$_{X}$ K W. (5) what is the underlying fundamental theory we can always identify the X − superfield as well as its scalar component x . More importantly, by making this assumption we are identifying the vacuum energy driven inflation with the actual SUSY breaking order parameter. In the supergravity context, once we have the K¨ ahler potential K ( X, ¯ X ) and the superpotential W ( X ), the full scalar potential is given by [30]: The scalar component x of X becomes a goldstino bilinear. Its fermionic component is the goldstino fermion G , and F is the auxiliary field that gets the vacuum expectation value. A major part in the anal- ysis in [27] is based on this novel nonlinear constraint satisfied by the superfield X in the IR. As shown there, the correct normalization of the goldstino su- perfield to derive all relevant low-energy theorems of broken supersymmetry is X$_{NL}$ = 3 8 $_{f}$X . with M is the high energy scale below which we can write the ef- fective action describing the dynamics of the X -superfield. It could be the Planck scale, or a GUT scale depending on the microscopic theory. We will work well below the scale M , and for simplicity take M = M$_{pl}$ In equation (4) we can see one of the basic problems in supergravity infla- tion [24]. As we will see later on, to satisfy the slow roll conditions, a necessary condition is that the η -parameter, defined by: • Finally, X generalizes the usual spurion couplings ap- pearing in the description of low-energy supersymmet- ric lagrangians. If m$_{soft}$ describes the soft supersym- metry breaking masses at low energies, the standard spurion in the lagrangian is replaced by m$_{soft}$ f X$_{NL}$ . This allows one to write the leading low-energy cou- plings of the goldtino to other matter fields. Since we are going to consider goldstino couplings, we will work with a field whose expectation values are well below the Planck scale. Our proposal is to identify in the UV the inflaton field with the scalar component of the superfield X . Since X is defined uniquely (up to the ambiguity mentioned in foot- note one) in the UV, this provides a well defined prescrip- tion. Furthermore, we will identify the inflationary period precisely with the flow of X from the UV to the IR i.e. X → X$_{NL}$ . Note that by making this assumption we do not need to think of the inflaton as any extra fundamental field. In fact, independently of how SUSY is broken, and η = M 2 pl V ′′ V , (6) be much smaller than one. If we choose a K¨ ahler potential K ( X, ¯ X ) with R-symmetry, for instance the canonical one K ( X, ¯ X ) = X ¯ X + ... , where the ... represents a function of X ¯ X , it is easy to see that from the exponent of (4) we always get a contribution to η equal to 1: η = 1 + ... , no matter which component of X is taken as the inflaton field. This of course violates the slow roll conditions. Since we are considering a situation with supersymmetry breaking and gravity (early universe), we cannot exclude supergrav- ity from the picture, and this leads to the η -problem in these theories. The simplest way out of this problem without unreason- able fine tuning, is to have explicit R-symmetry breaking $^{3}$A modified version of the nonlinear constraint (2) appears when one considers spontaneous R-symmetry breaking. In that case, the goldstino and the corresponding axion will be part of the same mul- tiplet. 3