Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Existence of endo-rigid Boolean algebras   In [Sh:89] we, answering a question of Monk, have explicated the notion of
``a Boolean algebra with no endomorphisms except the ones induced by
ultrafilters on it'' (see section 2 here) and proved the existence of one with
character density aleph_0, assuming first diamondsuit_{aleph_1} and then only
CH. The idea was that if h is an endomorphism of B, not among the ``trivial''
ones, then there are pairwise disjoint D_n in B with h(d_n) not subset d_n.
Then we can, for some S subset omega, add an element x such that d <= x for n
in S, x cap d_n=0 for n not in S while forbidding a solution for {y cap
h(d_n):n in S} cup {y cap h(d_n)=0:n not in S}. Further analysis showed that
the point is that we are omitting positive quantifier free types. Continuing
this Monk succeeded to prove in ZFC, the existence of such Boolean algebras of
cardinality 2^{aleph_0}.
  We prove (in ZFC) the existence of such B of density character lambda and
cardinality lambda^{aleph_0} whenever lambda > aleph_0. We can conclude answers
to some questions from Monk's list. We use a combinatorial method from
[Sh:45],[Sh:172], that is represented in Section 1.

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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: econ
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin