21 research outputs found
Ring graphs and complete intersection toric ideals
We study the family of graphs whose number of primitive cycles equals its
cycle rank. It is shown that this family is precisely the family of ring
graphs. Then we study the complete intersection property of toric ideals of
bipartite graphs and oriented graphs. An interesting application is that
complete intersection toric ideals of bipartite graphs correspond to ring
graphs and that these ideals are minimally generated by Groebner bases. We
prove that any graph can be oriented such that its toric ideal is a complete
intersection with a universal Groebner basis determined by the cycles. It turns
out that bipartite ring graphs are exactly the bipartite graphs that have
complete intersection toric ideals for any orientation.Comment: Discrete Math., to appea
Design of an Artificial Neural Network for the Analysis of Stellar Spectra
We have developed an artificial neural network, whose purpose is to automatically find in a database of synthetic stellar spectra the one which best reproduces an observed spectrum. Using the equivalent widths of selected spectral lines, the network fits a set of lines related to the physical parameters in the stellar atmosphere (i.e., temperature, gravity and mass loss rate). The main advantage of this approach is its scalability