Let T be a closed surface. It is proven that any decomposition of 1(T,x) into an amalgamated product (or, more generally, into the fundamental group of a finite graph of groups) with f.g. edge group(s) is almost geometric. A problem of H. Zieschang is solved and the edge rigidity property is investigated. 相似文献
Let F be an Abelian number field and S the set of primes of F that are either ramified or over p, with p an odd prime. In this paper we compute the (first) Fitting ideal of K2i–2ét
(O
FS
() for i 2, where O
FS
is the ring of S-integers of F and is a character of Gal(F/) of order prime to p different from the ith power of the Teichmüller character. This Fitting ideal proves to be principal and generated by a Stickelberger element. 相似文献
The ideals of effect algebras induce a topology on effect algebras. The operations and of effect algebras are continuous with respect to this topology. 相似文献
The X-ray absorption jump factor and jump ratio of Gd, Dy, Ho and Er were measured with a Si(Li) detector by attenuation, with Gd, Dy, Ho and Er foil, a Compton peak produced by the scattering of the Am-241 Gamma rays. Al was chosen as secondary exciter. The experimental absorption jump factors and jump ratios are compared with the theoretical estimates of WinXcom (Radiat. Phys. Chem. 60 (2001) 23), McMaster (Compilation of X-ray cross sections UCRL-50174, 1969; Sec. II. Rev. I), Broll (X-ray Spectrom 15 (1986) 271), Hubbel and Seltzer (NISTIR (1995) 5632) and Budak (Radiat. Meas. accepted for publication). The present results constitute the first measurement for this combination of energy and elements, and good agreement is obtained between experiment and theory. 相似文献
This paper is concerned with tight closure in a commutative Noetherian ring of prime characteristic , and is motivated by an argument of K. E. Smith and I. Swanson that shows that, if the sequence of Frobenius powers of a proper ideal of has linear growth of primary decompositions, then tight closure (of ) `commutes with localization at the powers of a single element'. It is shown in this paper that, provided has a weak test element, linear growth of primary decompositions for other sequences of ideals of that approximate, in a certain sense, the sequence of Frobenius powers of would not only be just as good in this context, but, in the presence of a certain additional finiteness property, would actually imply that tight closure (of ) commutes with localization at an arbitrary multiplicatively closed subset of .
Work of M. Katzman on the localization problem for tight closure raised the question as to whether the union of the associated primes of the tight closures of the Frobenius powers of has only finitely many maximal members. This paper develops, through a careful analysis of the ideal theory of the perfect closure of , strategies for showing that tight closure (of a specified ideal of ) commutes with localization at an arbitrary multiplicatively closed subset of and for showing that the union of the associated primes of the tight closures of the Frobenius powers of is actually a finite set. Several applications of the strategies are presented; in most of them it was already known that tight closure commutes with localization, but the resulting affirmative answers to Katzman's question in the various situations considered are believed to be new.
An m-restricted edge cut is an edge cut that separates a connected graph into a disconnected one with no components having order less than m. m-restrict edge connectivity λm is the cardinality of a minimum m-restricted edge cut. Let G be a connected k-regular graph of order at least 2m that contains m-restricted edge cuts and X be a subgraph of G. Let θ(X) denote the number of edges with one end in X and the other not in X and ξm=min{θ(X) ;X is a connected vertex-induced subgraph of order m}.It is proved in this paper that if G has girth at least m/2 2,then λm≤ξm.The upper bound of λm is sharp. 相似文献
The solution of the Stokes problem in three-dimensional domainswith edges has anisotropic singular behaviour which is treatednumerically by using anisotropic finite element meshes. Thevelocity is approximated by CrouzeixRaviart (nonconformingP1 ) elements and the pressure by piecewise constants. Thismethod is stable for general meshes (without minimal or maximalangle condition). Denoting by Ne the number of elements in themesh, the interpolation and consistency errors are of the optimalorder hNe1/3 which is proved for tensor product meshes.As a by-product, we analyse also nonconforming prismatic elementswith P1 [oplus ] span {x32} as the local space for the velocitywhere x3 is the direction of the edge. 相似文献