TY - JOUR

T1 - A thin-tall boolean algebra which is isomorphic to each of its uncountable subalgebras

AU - Bonnet, Robert

AU - Rubin, Matatyahu

N1 - Funding Information:
E-mail addresses: [email protected] (R. Bonnet), [email protected] (M. Rubin). 1 Robert Bonnet was supported by the “Center for Advanced Studies in Mathematics” of Ben Gurion University.

PY - 2011/8/15

Y1 - 2011/8/15

N2 - Theorem A{lozenge, open}א1There is a Boolean algebra B with the following properties:(1)B is thin-tall, and(2)B is downward-categorical. That is, every uncountable subalgebra of B is isomorphic to B. The algebra B from Theorem A has some additional properties. For an ideal K of B, set cmplB(K):={a∈B|a.b=0 for all b∈K}. We say that K is almost principal if K∪cmplB(K) generates B.(3)B is rigid in the following sense. Suppose that I, J are ideals in B and f:B/I→B/J is a homomorphism with an uncountable range. Then there is an almost principal ideal K of B such that |cmpl(K)|≤א0, I∩K⊆J∩K, and for every a∈K, f(a/I)=a/J.(4)The Stone space of B is sub-Ostaszewski. Boolean-algebraically, this means that: if I is an uncountable ideal in B, then B/I has cardinality ≤א0.(5)Every uncountable subalgebra of B contains an uncountable ideal of B.(6)Every subset of B consisting of pairwise incomparable elements has cardinality ≤א0.(7)Every uncountable quotient of B has properties (1)-(6).Assuming {lozenge, open}א1 we also construct a Boolean algebra C such that:. (1)C has properties (1) and (4)-(6) from Theorem A, and every uncountable quotient of C has properties (1) and (4)-(6).(2)C is rigid in the following stronger sense. Suppose that I, J are ideals in C and f:C/I→C/J is a homomorphism with an uncountable range. Then there is a principal ideal K of C such that |cmpl(K)|≤א0, I∩K⊆J∩K, and for every a∈K, f(a/I)=a/J.

AB - Theorem A{lozenge, open}א1There is a Boolean algebra B with the following properties:(1)B is thin-tall, and(2)B is downward-categorical. That is, every uncountable subalgebra of B is isomorphic to B. The algebra B from Theorem A has some additional properties. For an ideal K of B, set cmplB(K):={a∈B|a.b=0 for all b∈K}. We say that K is almost principal if K∪cmplB(K) generates B.(3)B is rigid in the following sense. Suppose that I, J are ideals in B and f:B/I→B/J is a homomorphism with an uncountable range. Then there is an almost principal ideal K of B such that |cmpl(K)|≤א0, I∩K⊆J∩K, and for every a∈K, f(a/I)=a/J.(4)The Stone space of B is sub-Ostaszewski. Boolean-algebraically, this means that: if I is an uncountable ideal in B, then B/I has cardinality ≤א0.(5)Every uncountable subalgebra of B contains an uncountable ideal of B.(6)Every subset of B consisting of pairwise incomparable elements has cardinality ≤א0.(7)Every uncountable quotient of B has properties (1)-(6).Assuming {lozenge, open}א1 we also construct a Boolean algebra C such that:. (1)C has properties (1) and (4)-(6) from Theorem A, and every uncountable quotient of C has properties (1) and (4)-(6).(2)C is rigid in the following stronger sense. Suppose that I, J are ideals in C and f:C/I→C/J is a homomorphism with an uncountable range. Then there is a principal ideal K of C such that |cmpl(K)|≤א0, I∩K⊆J∩K, and for every a∈K, f(a/I)=a/J.

KW - Ostaszewski space

KW - Rigid boolean algebra

KW - Scattered space

KW - Superatomic boolean algebra

KW - Thin-tall

UR - http://www.scopus.com/inward/record.url?scp=79960025386&partnerID=8YFLogxK

U2 - 10.1016/j.topol.2011.05.003

DO - 10.1016/j.topol.2011.05.003

M3 - Article

AN - SCOPUS:79960025386

SN - 0166-8641

VL - 158

SP - 1503

EP - 1525

JO - Topology and its Applications

JF - Topology and its Applications

IS - 13

ER -