منابع مشابه
Surface Bundles over Surfaces with Arbitrarily Many Fiberings
In this paper we give the first example of a surface bundle over a surface with at least three fiberings. In fact, for each n ≥ 3 we construct 4-manifolds E admitting at least n distinct fiberings pi : E → Σgi as a surface bundle over a surface with base and fiber both closed surfaces of negative Euler characteristic. We give examples of surface bundles admitting multiple fiberings for which th...
متن کاملOn the U-WPF Acts over Monoids
Valdis Laan in [5] introduced an extension of strong flatness which is called weak pullback flatness. In this paper we introduce a new property of acts over monoids, called U-WPF which is an extension of weak pullback flatness and give a classification of monoids by this property of their acts and also a classification of monoids when this property of acts implies others. We also show that regu...
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ژورنال
عنوان ژورنال: Bulletin of the American Mathematical Society
سال: 1967
ISSN: 0002-9904
DOI: 10.1090/s0002-9904-1967-11832-9