Inflation in R2R^2 supergravity with non-minimal superpotentials

We investigate the cosmological inflation in a class of supergravity models that are generalizations of non-supersymmetric $R^2$ models. Although such models have been extensively studied recently, especially after the launch of the PLANCK and BICEP2 data, the class of models that can be constructed has not been exhausted. In this note, working in a supergravity model that is a generalization of Cecotti's model, we show that the appearance of new superpotential terms, which are quadratic in the superfield $\, \Lambda$ that couples to the Ricci supermultiplet, alters substantially the form of the scalar potential. The arising potential has the form of the Starobinsky potential times a factor that is exponential in the inflaton field and dominates for large inflaton values. We show that the well-known Starobinsky inflation scenario is maintained only for unnaturally small fine-tuned values of the coupling describing the $\Lambda^2$ superpotential terms. A welcome feature is the possible increase of the tensor to scalar ratio $r$, within the limits set by the new Planck and BICEP2 data.Comment: 13 pages, 9 figures, text and references added, version submitted to Phys. Lett.

A linear programming-based method for job shop scheduling

We present a decomposition heuristic for a large class of job shop scheduling problems. This heuristic utilizes information from the linear programming formulation of the associated optimal timing problem to solve subproblems, can be used for any objective function whose associated optimal timing problem can be expressed as a linear program (LP), and is particularly effective for objectives that include a component that is a function of individual operation completion times. Using the proposed heuristic framework, we address job shop scheduling problems with a variety of objectives where intermediate holding costs need to be explicitly considered. In computational testing, we demonstrate the performance of our proposed solution approach

Deforming the Starobinsky model in ghost-free higher derivative supergravities

We consider higher derivative supergravities that are dual to ghost-free N=1 supergravity theories in the Einstein frame. The duality is implemented by deforming the Kähler function, and/or the superpotential, to include nonlinear dependences on chiral fields that, in other approaches, play the role of the Lagrange multipliers employed to establish this duality. These models are of the no-scale type, and in the minimal case, they require the presence of four chiral multiplets, with a Kähler potential having the structure of the SU(4,1)/SU(4)×U(1) coset manifold. In the standard N=1 supergravity formulation, these models are described by a multifield scalar potential, featuring Starobinsky-like behavior in particular directions. © 2017 American Physical Society

Inflation in R2 supergravity with non-minimal superpotentials

We investigate the cosmological inflation in a class of supergravity models that are generalizations of non-supersymmetric R2 models. Although such models have been extensively studied recently, especially after the launch of the PLANCK and BICEP2 data, the class of models that can be constructed has not been exhausted. In this note, working in a supergravity model that is a generalization of Cecotti's model, we show that the appearance of new superpotential terms, which are quadratic in the superfield Λ that couples to the Ricci supermultiplet, alters substantially the form of the scalar potential. The arising potential has the form of the Starobinsky potential times a factor that is exponential in the inflaton field and dominates for large inflaton values. We show that the well-known Starobinsky inflation scenario is maintained only for unnaturally small fine-tuned values of the coupling describing the Λ2 superpotential terms. A welcome feature is the possible increase of the tensor to scalar ratio r, within the limits set by the new Planck and BICEP2 data. © 2015 The Authors