902 citations
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Showing 1998Show all
3 papers · 1 filter
math.GR1998
A note on doubles of groups
Nadia Benakli, Oliver T. Dasbach, Yair Glasner +1
Recently, Rips produced an example of a double of two free groups which has unsolvable generalized word problem. In this paper, we show that Rips's example fits into a large class…
astro-ph1998★ 18 cited
A Hidden Broad-Line Region in the Weak Seyfert 2 Galaxy NGC 788
Laura E. Kay, Edward C. Moran
We have detected a broad H alpha emission line in the polarized flux spectrum of the Seyfert 2 galaxy NGC 788, indicating that it contains an obscured Seyfert 1 nucleus. While such…
math.AC1998★ 3 cited
Extremal Betti Numbers and Applications to Monomial Ideals
Dave Bayer, Hara Charalambous, Sorin Popescu
In this short note we introduce a notion of extremality for Betti numbers of a minimal free resolution, which can be seen as a refinement of the notion of Mumford-Castelnuovo regul…