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arXiv 1104.4207math.LOmath.RA
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代数强同余-真簇之间临界点的可能值

The possible values of critical points between strongly congruence-proper varieties of algebras

Pierre Gillibert

摘要:

我们用Conc(A)表示一个(泛)代数A的所有Conc生成的同余的半格,并且我们定义Conc(V)为所有Conc(A)的所有同构副本的类,对于A在V中,对于任何代数簇V。设V和W是代数的局部有限簇,使得对于V中的每个有限代数A,在同构之前,W中只有2/3个B,使得A和B有同构的同余格,并且每个这样的B是有限的.如果Conc(V)不包含在Conc(W)中,则存在基数为aleph 2的半格在Conc(V)-Conc(W)中.我们的结果推广到一阶结构的拟簇,具有许多关系符号和相对同余格。特别地,如果W是代数的一个非平凡生成簇,则这发生在W省略了驯服的同余理论类型1和类型5的情况下;反过来,这发生在W满足非平凡的同余恒等式的情况下。绑定aleph 2是尖锐的。

英文摘要:

We denote by Conc(A) the semilattice of all finitely generated congruences of an (universal) algebra A, and we define Conc(V) as the class of all isomorphic copies of all Conc(A), for A in V, for any variety V of algebras. Let V and W be locally finite varieties of algebras such that for each finite algebra A in V there are, up to isomorphism, only finitely many B in W such that A and B have isomorphic congruence lattices, and every such B is finite. If Conc(V) is not contained in Conc(W), then there exists a semilattice of cardinality aleph 2 in Conc(V)-Conc(W). Our result extends to quasivarieties of first-order structures, with finitely many relation symbols, and relative congruence lattices. In particular, if W is a finitely generated variety of algebras, then this occurs in case W omits the tame congruence theory types 1 and 5; which, in turn, occurs in case W satisfies a nontrivial congruence identity. The bound aleph 2 is sharp.

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