2,113 research outputs found
Unmixed bipartite graphs and sublattices of the Boolean lattices
The correspondence between unmixed bipartite graphs and sublattices of the
oolean lattice is discussed. By using this correspondence, we show the
existence of squarefree quadratic initial ideals of toric ideals arising from
minimal vertex covers of unmixed bipartite graphs.Comment: 5 page
A New Galactic Extinction Map of the Cygnus Region
We have made a Galactic extinction map of the Cygnus region with 5' spatial
resolution. The selected area is 80^\circ to 90^\circ in the Galactic longitude
and -4^\circ to 8^\circ in the Galactic latitude. The intensity at 140 \mum is
derived from the intensities at 60 and 100 \mum of the IRAS data using the
tight correlation between 60, 100, and 140 \mum found in the Galactic plane.
The dust temperature and optical depth are calculated with 5' resolution from
the 140 and 100 \mum intensity, and Av is calculated from the optical depth. In
the selected area, the mean dust temperature is 17 K, the minimum is 16 K, and
the maximum is 30 K. The mean Av is 6.5 mag, the minimum is 0.5 mag, and the
maximum is 11 mag. The dust temperature distribution shows significant spatial
variation on smaller scales down to 5'. Because the present study can trace the
5'-scale spatial variation of the extinction, it has an advantage over the
previous studies, such as the one by Schlegel, Finkbeiner, & Davis, who used
the COBE/DIRBE data to derive the dust temperature distribution with a spatial
resolution of 1^\circ. The difference of Av between our map and Schlegel et
al.'s is \pm 3 mag. A new extinction map of the entire sky can be produced by
applying the present method.Comment: 27 pages, 14 figures, accepted for publication in Ap
Betti number sequences of simplicial complexes, Cohen-Macaulay types and Mbius functions of partially ordered sets, and related topics
We give a survey of some recent results on bt·(k[6]) = dimk Torf(k[6], k) of the face ring (Stanley-Reisner ring) k[6] of a simplicial complex 6. In particular, we study Cohen-Macaulay types and canonical modules of partially ordered sets
Buchsbaum complexes with linear resolutions
We study the Betti numbers which appear in a minimal free resolution of the Stanley-Reisner ring k[.6.] of a Buchsbaum complex .6. and find a characterization of Buchsbaum complexes .6. for which a minimal free resolution of k[.6.] is linear
Hochster's formula on Betti numbers and Buchsbaum complexes
The Betti numbers dimk.ToriA(k[ ],k) with i > v - d of the Stanley-Reisner ring k[ ] = A/I of a Buchsbaum complex of dimension d - 1 ouer a field k with v uertices are studied
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