Statement:

\(C(\infty,\infty)\):  The Axiom of Choice: Every  set  of  non-empty sets has a choice function.

Howard_Rubin_Number: 1

Parameter(s): This form does not depend on parameters

This form's transferability is: Unknown

This form's negation transferability is: Negation Transferable

Article Citations:

Book references

Note connections:

The following forms are listed as conclusions of this form class in rfb1: 107, 17, 408,

Back

Complete List of Equivalent Forms

Howard-Rubin Number Statement References
1 A

In every vector space, every generating set contains a basis.

Halpern [1966]

1 B

Every commutative ring with unit has a maximal ideal.

Hodges [1979]

1 C

For all infinite cardinals \(m\), \(UT(m,m,m)\):If every member of an infinite set \(A\) has power \(|A|\) then\(|\bigcup A| = |A|\). (Note that [1 C] implies \(m^{2} =m\) forall infinite cardinals m.)

Howard [1994]

1 D

Cardinal successors 3: For every cardinal \(m\) there isa cardinal \(n\) such that \(m < n\) and \((\forall p)( m < p \rightarrow n \le  p )\).

Tarski [1954a] Jech [1966a]

1 E

\(K(0)\):  For every set \(S\) there is an ordinal \(\alpha\) and a one to one function \(f: S \rightarrow \alpha\). (See Form 81(\(n\))).



1 F

For all ordinals \(\alpha\), \(DC(\aleph_{\alpha})\): Given a relation \(R\) such that for every subset \(Y\) of a set \(X\) with\(|Y| < \aleph_{\alpha}\), there is an \(x \in X \) with \(Y\mathrel R x\), then there is a function \(f:\aleph_{\alpha} \to X\) such that \(\forall\beta < \aleph_{\alpha}\), \(\{f(\gamma):\gamma < \beta\}\mathrel Rf(\beta)\).

Levy [1964]
Note [133]
1 G

Form 163 + Form 8.

Brunner [1982a]
Note [94]
1 H

Form 164 + Form 67.

Brunner [1982a]
Note [94]
1 I

In every metric space \((X,d)\) there is an\(\epsilon\)-lattice for some \(\epsilon >0\) which is not a strict upperbound of \(d\).

Brunner [1984e]
Note [17]
1 J

Form 49 \(+\)Form 51.

Morris [1969]
Note [121]
1 K

Form 133 \(+\)Form 64.  Clear



1 L

Hajnal's Free Set Principle:  For every set mapping \(f: X\rightarrow [X]^{<\lambda}\) where \(\lambda\) is a well orderable cardinal and \(\lambda< |X|\) there is a free set of cardinality \(|X|\). ((\([X]^{<\lambda}\) is the set of subsets of \(X\) of cardinality \(<\lambda\)).

Brunner [1989]
Note [22]
1 M

The ramification Lemma: If \(S: X^{\le\theta}\rightarrow {\cal P}(E)\) is a ramification system, then for each \(g \in E\) there is an \(f\) which is maximal (with respect to inclusion) in \(\{h \in X^{\le\theta}: g\in S(h)\}\).

Brunner [1989]
Note [22]
1 N

For every set mapping \(f: X\rightarrow [X]^{WO}\)(well ordered subsets of \(X\)) there is a co-well-orderable free subset\(H\). (\(H\) is co-well-orderable if \(X\setminus H\) is well orderable).

Brunner [1989]
Note [22]
1 O

\(A(D1,C)\): For every \(T_2\) topological space \((X,T)\),if \(X\) is covered by a well ordered family of closed, discrete sets theneach family \(U\subseteq T\) of pairwise disjoint sets is  well ordered.

Brunner [1983d]
Note [26]
1 P

\(A(P)\): (Depends on \(P\) for \(P\in\{W1,W2,B1,L1,L2,S,C,H1,A1\}\)) Every \(T_2\) topological space has property \(P\).

Brunner [1983d]
Note [26]
1 Q

For any partial order \((X,\le)\) there is a \(\sup\) function on the bounded (above), well ordered subsets of \(X\).

Manka [1988a]
Note [38]
1 R

For any partial order \((X,\le)\) there is a \(\sup\) function on the bounded subsets of \(X\).

Manka [1988a]
Note [38]
1 S

For any partial order \((X,\le)\) if every well ordered subset of \(X\) is bounded then there is a \(\sup\) function on the well ordered subsets of \(X\).

Manka [1988a]
Note [38]
1 T

For every directed partial order \((X,\le)\) there is a\(\sup\) function on the bounded, well ordered subsets of \(X\).

Manka [1988a]
Note [38]
1 U

For every directed partial order, if every well ordered subset of \(X\) is bounded above then there is a \(\sup\) function on the well ordered subsets of \(X\).

Manka [1988a]
Note [38]
1 V

For  every  partially  ordered  set \((X,\le )\),  if every well ordered subset is bounded above then every function \(f : X \rightarrow  X\) satisfying \(\forall t\in X\), \(t\le f(t)\) has a fixed point.

Manka [1988a] Abian [1980]

1 W

Form 133 + Form 88.

Brunner [1982a]

1 X

Form 15 + Form 91.

Brunner [1982a]

1 Y

Refined Dual Cantor-Bernstein Theorem:  If \(f : X\rightarrow Y\) and \(g : Y \rightarrow  X\) are onto then there is a bijection \(h : X \rightarrow  Y\) such that \(h \subseteq f \cup g^{-1}\).

Banaschewski-Moore-1990

1 Z

If \((P,\le)\) is a quasi-order and \(P \neq \emptyset\) and every antichain is finite, then there is a \(P\) generic filter which is well orderable.

Shannon [1990]
Note [47]
1 AA

Assume \(f: S\rightarrow R\) where \(f\) is surjective and \(R\subseteq S\).Then every mapping \(g\) of \(S\) into \(R\) has the form \(g = f\circ h\) for some \(h: S \rightarrow S\).

Smith [1982]

1 AB

Assume \(f: S \rightarrow R\) where \(f\) is surjective and \(R\subseteq S\).Then the mappings of \(S\) onto \(R\) are precisely the mappings of the form \(f\circ h\)  where \(h: S\rightarrow S\) and \((\forall y\in R)(\exists x\in S)(h(x)\in f^{-1}(\{y\}))\).

Smith [1982]

1 AC

Assume \(f: S\rightarrow R\) where \(R\subseteq S\). Then the retractions of \(S\) onto \(R\) (that is, the mappings \(g: S \rightarrow R\) which are the identity on \(R\)) are precisely the mappings \(f\circ h\) where \(h: S \rightarrow S\) and \((\forall y\in R)(h(y)\in f^{-1}(\{y\}))\).

Smith [1982]

1 AD

For every class \(K\) of similar algebras \(SP^{g} K\supseteq P^{g}S\ K\).  (For any class \(K\) of similar algebras, \(S\ K\) is the class of all subalgebras of elements of \(K\) (not closed under isomorphism) and \(P^{g}K\) is the class of direct products of elements of \(K\) not closed under isomorphism).

Andreka-Nemeti-1980

1 AE

There is a set \(S\) such that \(SVC\) holds with \(S\) and such that \({\cal P}(S) - \{\emptyset\}\) has a choice function.  Also see Form 191.

Blass [1979]
Note [59]
1 AF

Form 191 + Form 8 + Form 193. Note 60.

Blass [1979]

1 AG

Form 192  + Form 191.


Note [60]
1 AH

\(E(V,VI)\): For all infinite cardinals \(m\), \(2m = m\) implies \(m^{2} = m\).

Howard-Yorke-1989
Note [94]
1 AI

  \(E(VI,VII)\):  For all infinite cardinals \(m\), \(m^{2} = m\) implies there is an ordinal \(\alpha\) such that \(m =\aleph _{\alpha }\).

Howard-Yorke-1989
Note [94]
1 AJ

Let \({\cal F}\) be a family of mappings of a  poset \((X,\le )\) into itself such that \(\forall f\in{\cal F}\), \(\forall x\in X\),\(f(x)\le x\). If for some element \(e\) of \(X\) each chain in \(X\) containing \(e\) has a lower bound, then the family \({\cal F}\) has a common fixed point.

Kasahara [1976]

1 AK

There is an ordinal \(\beta\) such that for all cardinals \(x\), \(\alpha(x+\aleph(x), x\cdot\aleph(x))<\beta\).

Truss [1973b]
Note [98]
1 AL

There is an ordinal \(\beta\) such that for all cardinals\(x\), \(\alpha(x,x^2) < \beta\).

Truss [1973b]
Note [98]
1 AM

There is an ordinal \(\beta\) such that for no cardinal \(x\) is there a strictly increasing sequence of cardinals \(\left \{ \,y_{\gamma} : \gamma < \beta \, \right \}\) such that \(y_{\gamma}^2 = x\).

Truss [1973b]
Note [98]
1 AN

Every lattice \(\langle L,\cap,\cup, \subseteq\rangle\)of sets (that is, \(L\) is a family of sets and \(\cap,\ \cup\) and \(\subseteq\) are the usual operations) with a greatest element has a maximal, proper ideal.

Bell-Fremlin-1972

1 AO

Any continuous surjection between compact spaces, where the range space is Hausdorff, has an irreducible restriction to a closed subset of its domain.

Bell [1988]
Note [114]
1 AP

For any type \(\tau\) of the form \(\tau = (M)\), everyhomomorphism of an algebra of type \(\tau\) is closed.

Diener [1989]
Note [115]
1 AQ

For any type \(\tau\) of the form \(\tau = (M)\), every homomorphism of an algebra A of type \(\tau\) into an algebra B of type \(\tau\) maps A onto a subalgebra of B.

Diener [1989]
Note [105]
1 AR

Let \(S\) be any family of disjoint non-empty sets andlet \(\tau = (\bigcup S)\), then any homomorphism from \(\frak P(\tau;\bigcup S)\)into \(\frak P(\tau;S)\) maps \(\frak P(\tau;\bigcup S)\) onto a subalgebra of \(\frak P(\tau;S)\).

Diener [1989]
Note [115]
1 AS

Turinici's Fixed Point Theorem:  If \((X,\le)\) is a directed, partially ordered set and \(\tau\) is a topology on \(X\) such that

  1. \((X,\le)\) is upper semicontinuous with respect to \(\tau\),
  2. Every well ordered subset of \((X,\le)\) is convergent as a net,
then every function \(f:X\to X\) such that \(\forall x\in X\),\(x\le f(x)\) has a fixed point.

Manka [1988b]
Note [38]
1 AT

For all cardinal numbers \(\kappa_1\) and \(\kappa_2\), if a graph is both \(\kappa_1\) and \(\kappa_2\) colorable then it is also\(\kappa\) colorable for some \(\kappa\) such that \(\kappa\le^*\kappa_1\) and \(\kappa\le^*\kappa_2\). (\(\le^*\) is the surjective cardinal ordering).

Komj'ath-Galvin-1991

1 AU

Every graph has an irreducible, good coloring.

Komj'ath-Galvin-1991
Note [118]
1 AV

Every graph of the form \(G(A,H(A))\) has an irreducible, good coloring.  (\(H\) is the Hartogs aleph function.)

Komj'ath-Galvin-1991
Note [118]
1 AW

Every graph has a chromatic number.

Komj'ath-Galvin-1991
Note [118]
1 AX

Birkhoff Representation Theorem: Every algebra isisomorphic to a subdirect product of subdirectly irreducible algebras.

Birkhoff [1944] Gratzer [1986]

Book: Universal Algebra [1979]
1 AY

For each \(\lambda\in\Lambda\) let \(S_\lambda\) be a subset of some topological space \(X_\lambda\). Then

cl\(\left(\prod_{\lambda\in\Lambda}S_\lambda\right)=\prod_{\lambda\in\Lambda}\hbox{cl}\left(S_{\lambda}\right)\),
where the first ``cl'' is closure in the product topology and the second ``cl'' is closure in \(X_\lambda\).

Schechter [1992]

1 AZ

For each \(\lambda\in\Lambda\), let \(X_\lambda\) be a complete uniform space. Then, the product \(\prod_{\lambda\in\Lambda}X_\lambda\) equipped with the product uniform structure, is also complete.(See, for example, Kelley [1955] pp 176ff for definitions.)

Schechter [1992]

Book: General Topology
1 BA

(Depends on the prime \(p\)) Every group has a maximal \(p\)-subgroup.

Howard-Yorke-1987
Note [24]
1 BB

Strong Nielsen-Schreier Theorem II: If \(G\) is a group which is freely generated by \(X\) and \(U\) is a subgroup of \(G\),then there is a subset \(A\) of \(G\) which freely generates \(U\) and is level with respect to \(X\).

Howard [1985]
Note [129]
1 BC

Assume \(P\) is a partially ordered set in which every non-empty chain has an upper bound and \(f: P\to P\) satisfies \(\forall x\in f(P) \cup \{\,a\in P : a\) is an upper bound for some chain in \(f(P)\,\}\),\(x\le f(f(x))\).  Then \(f\) has a fixed apex \(u\) (that is, there is some \(v\in P\) such that \(f(u)=v\) and \(f(v)=u\).)

Taskovi'c [1988] Taskovi'c [1992a]

1 BD

Let \(P\) be a partially ordered set in which every increasing sequence has an upper bound and \(f:P\to P\) satisfies \(x \le f(f(x))\) for all \(x\in f(P) \cup \{x\in P : x\) is an upper bound for some increasing sequence in \(f(P)\}\). Then \(f\) has a fixed apex \(u\)(that is, \(\exists v\in P\), such that \(f(u) = v\) and \(f(v) = u\)). (For purposes of [1 BD], ``sequence'' means a function whose domain is an ordinal.)

Taskovi'c [1992b]

1 BE

Every unique factorization domain can be mapped homomorphically onto a non-zero subdirectly irreducible ring. Gratzer [1979] pp 122-124.

Rav [1988]
Note [84]
Book: Universal Algebra [1979]
1 BF

(\(DT_0)\): Every topological space \(X\) has a \(T_0\) subspace that is dense in \(X\). (\(Y\) is dense in \(X\) if there is no non-empty open subset \(O\subseteq X\) such that \(O\cap Y=\emptyset\).)

McCarten [1988]
Note [106]
1 BG

(C\(T_0\)): Every topological space \(X\) has a \(T_0\)subspace that is codense in \(X\). (\(Y\) is codense in \(X\) if there is nonon-empty closed subset \(C\subseteq X\) such that \(C\cap Y=\emptyset\).)

McCarten [1988]
Note [106]
1 BH

\((TT_0)\): Every topological space \(X\) has a \(T_0\) subspace that is thick in \(X\). (\(Y\) is thick in \(X\) if there is nonon-empty open and closed (clopen) subset \(H\subseteq X\) such that\(H\cap Y=\emptyset\).)

McCarten [1988]
Note [106]
1 BI \((MT_0)\): Every topological space has a maximal \(T_0\)subspace.

Schnare [1968]
Note [106]
1 BJ

In every vector space over the two element field, every generating set contains a basis.

Keremedis [1996a]

1 BK

Every open cover \(\cal{U}\) of a metric space \((X,d)\) can be written as a well ordered union \(\bigcup\{U_\alpha :\alpha\in\gamma\}\) where \(\gamma\) is an ordinal and each \(U_\alpha\) is pairwise disjoint. Howard/Keremedis/Rubin/Stanley [1999].



1 BL

Every family of closed sets in a \(T_2\) topological space includes a maximal subfamily with the finite intersectionproperty.  H.Rubin/J.Rubin [1985], p 60, \(M14\).

Keremedis [1998a]

Book: Equivalents of the Axiom of Choice II
1 BM

For every family \(\{(X_i,T_i): i\in k\}\) of \(T_1\) topological spaces, the box topology contains an element \(\prod_{i\in k}O_i\), such that \(\emptyset\ne O_i\) and \(O_i\ne X_i\) for all \(i\in k\).

Keremedis [1998a]
Note [77]
1 BN

For every family \(\{(X_i,T_i): i\in k\}\) of disjoint \(T_1\) topological spaces, the free union contains an open set \(O\) such that \(\emptyset\ne O\cap X_i\) and \( O\cap X_i\ne X_i\) for all\(i\in k\).

Keremedis [1998a]
Note [77]
1 BO

For every \(T_1\) topological space \((X,T)\) and every base (subbase) \(B\) for \(X\) there exists a \(\subseteq\)-maximal cellular family \(Q\subseteq B\).

Keremedis [1998a]
Note [77]
1 BP

For every dense in itself topological space \((X, T)\) and every base \(B\) for \(X\) there exists a nest \(N\) included in \(B\).

Keremedis [1998a]
Note [77]
1 BQ

For every dense in itself topological space \((X,T)\) and every base \(B\) for \(X\) there exists a tower \(R\) included in \(B\).

Keremedis [1998a]
Note [77]
1 BR

For every \(T_2\) space \((X,T)\) and every subbase \(\cal B\) for \(X\), if \(\cal C\) and \(\cal D\) are cellular families of \(X\) included in \(\cal B\), then there is a cellular family \(\cal E\subseteq\cal B\) such that \(\cal C\) and \(\cal D\) are equipollent to subsets of\(\cal E\).

Keremedis [1998a]
Note [77]
1 BS

For every Abelian group \((G,+)\), for every \(H \subseteq G\), the infinite system of equations \[x_i + y_i = a_i,\ i\in I,\ a_i\in G\] has a solution in \(H\) iff each of its equations has a solution in \(H\).

Keremedis [1996b]

1 BT

For every Boolean ring \((B,+,\cdot)\) and every \(H \subseteq  B\)  which is closed under \(+\) there exists a \(\subseteq\)-maximal ideal \(Q\subseteq B\) such that \(H\cap Q=\{0\}\).

Keremedis [1996b]

1 BU

In every vector space over \({\Bbb Q}\), every generating  set includes a basis.

Blass [1984a]
Note [137]
1 BV

If \((X,T)\) is a \(T_4\) topological space and \(G =\{G_i: i\in K\}\), \(|G_i|\ge 2\), is a locally finite family of compact sets with non-empty pairwise disjoint interiors, then there is a continuous real valued function \(f\) on \(X\) which assumes at least two distinct values on each \(G_i\).

Keremedis [1997]
Note [43]
1 BW

If \((X,T)\) is a \(T_4\) topological space and \(U =\{U_i: i\in K\}\), \(|U_i|\ge 2\), is a locally finite family ofopen non-empty pairwise disjoint sets, then there is a continuous real valued function \(f\) on \(X\) which assumes at least two distinct values on each \(U_i\).

Keremedis [1997]
Note [43]
1 BX

For every Abelian group \(G\) and every subgroup \(H\) of \(G\) there exists a set of representatives for the quotient \(G/H\).

Keremedis [1996b]

1 BY

If \(x\) is a set of sets of cardinality at least 2, then there exists a function \(f\) such that for each \(u\in x\), \(f(u)\) is a finite, non-empty, proper subset of \(u\). (Form [1 BY] implies [62 E] (\(KW(\infty,<\aleph_0)\)) and Form 67 (MC) and Form 62 \(+\) Form 67 \(\to\) AC.)

Blass [1979]

1 BZ

Vector Space Multiple Choice:  For every family \(V = \{\,V_i : i \in K\,\}\) of non-trivial vector spaces there is a family \(F = \{\, F_i : i\in K\,\}\) such that for each \(i\in K\),\(F_i\) is a non-empty, finite, independent subset of \(V_i\).


Note [127]
1 CA

Strong Nielsen-Schreier Theorem I:  If \(G\) is a groupwhich is freely generated by \(X\) and \(U\) is a subgroup of \(G\), then there is a subset \(A\) of \(G\) which freely generates \(U\) and has the Nielsen property with respect to \(X\).

Howard [1985]
Note [129]
1 CB

For every infinite cardinal \(\kappa\), if \((X,T)\) is a \(T_2\) space having a base \(B\) such that no \(Q\subseteq B\), \(|Q| <\kappa\), is a tower, then for every family \(\cal D=\{D_i:i\in\kappa\}\) of dense open sets of \(X\) there is a filter \(F\subseteq T\) such thatfor every \(i\in\kappa\) there  is a \(b\in F\) with \(b\subseteq D_i\).

Keremedis [1998a]
Note [77]
1 CC

\(PC(\aleph_0,\hbox{odd},\infty)\) +\(MC_{\omega^+}\). \(PC(\aleph_0,\hbox{odd},\infty)\) is ``Every denumerable family of odd sized (finite) sets has an infinite subfamily with a choice function.'' and \(MC_{\omega^+}\)is ``For every natural number \(n \ge 1\) and forevery set of non-empty sets, there is a function \(f\) such that for each \(u\in x\), \(f(u)\) is a non-empty finite subset of \(u\)  suchthat \(|f(u)|\) and \(n\) are relatively prime.''


Note [133]
1 CD

In a commutative ring, every proper ideal can be extended to a maximal ideal. ([1 CD] implies
[1 B]).

Krull [1929]

1 CE

Every open cover \(\cal{U}\) of a metric space \((X,d)\)can be written as a well ordered union \(\bigcup\{U_\alpha :\alpha\in\gamma\}\) where \(\gamma\) is an ordinal and each \(U_\alpha\) is discrete. Howard/Keremedis/Rubin/Stanley [1999] .


Note [141]
1 CF

If a topological space is \(cwH\), then it is \(cwH(B)\)for every basis \(B\).

Howard-Rubin-Keremedis-Rubin-1998b
Note [141]
1 CG

The disjoint union of \(cwH\) spaces is \(cwH(B)\) for every basis \(B\).

Howard-Rubin-Keremedis-Rubin-1998b
Note [141]
1 CH

If a topological space is \(cwN\), then it is \(cwH(B)\) for any basis \(B\).

Howard-Rubin-Keremedis-Rubin-1998b
Note [141]
1 CI

Every compact space is A-U compact.

Herrlich [1996a] Howard [1990]
Note [6]
1 CJ

Every B compact Hausdorff space is A-U compact.

Herrlich [1996a]
Note [6]
1 CK Products of A-U compact (Hausdorff) spacesare A-U compact.  Herrlich [1996a] and Note 6.

1 CL Finite products of A-U compact spaces are A-Ucompact.  Herrlich [1996a] and Note 6.

1 CM Spaces with finite topologies are A-U compact.Herrlich [1996a] and Note 6.

1 CN Products of spaces with finite topologies arecompact.  Alas [1969].

1 CO(X,Y) The product of \(X\) spaces is \(Y\),where \(X\) is either ``compact'', ``S-B compact'', or ``linearly compact''and \(Y\) is either ''compact'' or ``S-B compact''.  Howard [1990] and Note 6.

1 CP Form 384 +Form 8.  Herrlich/Steprans [1997].

1 CQ Closed Filter Extendability for \(T_0\) Spaces.Every closed filter in a \(T_0\) topological space can be extended toa maximal closed filter.  Keremedis/Tachtsis [1999b] and note10.

1 CR The Ascoli Theorem for A-U compactness. See form[14 CU], Note 6 and Herrlich [1997c]

1 CS Every W compact pseudometric space is A-U compact.See Howard [1990] (the proof of Theorem 3) and Note 6.

1 CT Every sequentially compact pseudometric space isA-U compact.  Herrlich [1997a]

1 CU Products of topological spaces with finite topologiesare A-U compact.  Herrlich [1997a] and Note 6.

1 CV Products of finite discrete topological spaces areA-U compact. Herrlich [1996a] and Note 6.

1 CW Every closed (open) filter in a \(T_1\) topologicalspace extends to a maximal closed (open) filter with a well orderablefilter base.  Keremedis/Tachtsis [2000].

1 CX For every set \(A\ne\emptyset\), every filter $\cal F\subseteq \cal P(A)$ extends to an ultrafilter with a well orderablefilter base.  Keremedis/Tachtsis [2000].

1 CY Every partial function on a set \(A\) can bedefined as follows: Let \(\varrho\), \(\sigma\), \(\varphi\), \(\tau_1\),\(\tau_2\), \(\tau_3\) be equivalence relations on \(A\) such that \(\sigma\)has a distinguished equivalence class \(D\) which is a set of distinctrepresentatives for the equivalence classes of \(\varrho\), \(\varphi\)has at most three equivalence classes \(D_1\), \(D_2\), and \(D_3\), andthe equivalence classes of \(\tau_n\), \(n=1,2,3\), have at most twoelements. If \(x\in A\) has a \(\varrho\)-representative \(u\in D\) andthere is an \(n=1,2,3\) such that \(u\in D_n\), then choose the smallest \(n\)with this property and define \(f(x)=u\), where \(\{u,f(x)\}\in D_n\).Armbrust [1986].

1 CZ Every compact frame has a maximal element.Banaschewski [1990] and Note 29.

1 DA Every large subspace of the spectrum of acompact frame is compact. (A subspace is large if it containsall minimal elements.) Banaschewski [1990] and Note 29.

1 DB Any large homomorphic image of a compact frameis compact.  (A frame homomorphism \(\phi: L\to M\) is calledlarge if \(\phi(s) < e\) (the unit) for all maximal elements\(s\in L\).) Banaschewski [1990] and Note 29.

1 DC In any complete lattice with at least two elementsthere exists an ultrafilter. Banaschewski [1961].

1 DD If \((L_i)_{i\in I}\) is a family of completelattices, each of which has at least two elements, then there existsa family \((M_i)_{i\in I}\) of filters such that \(M_i\) is anultrafilter in \(L_i\).  Banaschewski [1961].

1 DE Let \(L\) be a complete distributive lattice withat least two elements and let \(A\) be a proper subset of \(L\) such thatfor all \(x\in L\) and \(a\in A\), \(x\le a\) implies \(x\in a\). Then thereis an ultrafilter \(M\) disjoint form \(A\). Banaschewski [1961].

1 DF For any set \(X\), if \(\cal C\) is a set ofconditionally \(\cap\)-closed subsets of \(\cal P(X)\), then \(\cal C\)contains a maximal filter (not necessarily proper). (If $\cal C\subseteq\cal P(X)\(, \)\cal C\( is called conditionally \)\cap$-closed if forall \(A\), \(B\), \(C\) in \(\cal C\), \(C\subseteq A\cap B\) implies $A\cap B\in\cal C$.) Banaschewski [1961].

1 DG

Vector Space Kinna-Wagner Principle: For every family \(V = \{V_i : i \in K\}\) of non-trivial vector spaces there is a family \(F = \{F_i : i\in K\}\) such that for each \(i\in K\), \(F_i\) is a non-empty, independent subset of \(V_i\).

Keremedis [2001a]
Note [127]
1 DH

Every complete lattice is constructively complete. \ac{Ern\'e} \cite{2000}


Note [154]
1 DI-$Z$

(Where \(\cal Z\) is a subset selection such that for all partial orders \((P,\le)\), \(\cal E P\subseteq \cal Z P\subseteq \cal D P\).) Every complete lattice is \(\cal Z^\lor\)-constructively complete. \ac{Ern\'e} \cite{2000}.


Note [154]
1 DJ

Every directed partially ordered set is constructively directed. \ac{Ern\'e} \cite{2000}.


Note [154]
1 DK

For all \(X\), if \(X\neq\emptyset\), then there is a binary operation on \(X\) that makes \(X\) a group. Rubin, H./Rubin, J. [1985], p.110, AL14}.

Hickman [1976]

Book: Equivalents of the Axiom of Choice II