11 research outputs found
Inflation in supergravity with non-minimal superpotentials
We investigate the cosmological inflation in a class of supergravity models
that are generalizations of non-supersymmetric 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 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 superpotential terms. A welcome
feature is the possible increase of the tensor to scalar ratio , 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