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Boolean lattice (Definition)

In this entry, the notions of a Boolean lattice, a Boolean algebra, and a Boolean ring are defined, compared and contrasted.

Boolean Lattices

A Boolean lattice $ B$ is a distributive lattice in which for each element $ x\in B$ there exists a complement $ x'\in B$ such that

$\displaystyle x \land x'$ $\displaystyle =0$    
$\displaystyle x \lor x'$ $\displaystyle =1$    
$\displaystyle (x')'$ $\displaystyle =x$    
$\displaystyle (x \land y)'$ $\displaystyle =x'\lor y'$    
$\displaystyle (x \lor y)'$ $\displaystyle =x'\land y'$    

In other words, a Boolean lattice is the same as a complemented distributive lattice. A morphism between two Boolean lattices is just a lattice homomorphism (so that $ 0,1$ and $ '$ may not be preserved).

Boolean Algebras

A Boolean algebra is a Boolean lattice such that $ '$ and 0 are considered as operators (unary and nullary respectively) on the algebraic system. In other words, a morphism (or a Boolean algebra homomorphism) between two Boolean algebras must preserve $ 0,1$ and $ '$. As a result, the category of Boolean algebras and the category of Boolean lattices are not the same (and the former is a subcategory of the latter).

Boolean Rings

A Boolean ring is an (associative) unital ring $ R$ such that for any $ r\in R$, $ r^2=r$. It is easy to see that

Boolean rings (with identity, but allowing 0=1) are equivalent to Boolean lattices. To view a Boolean ring as a Boolean lattice, define

$\displaystyle x \land y = xy,\qquad x \lor y = x + y + xy,$   and$\displaystyle \qquad x'=1+x.$
To view a Boolean lattice as a Boolean ring, define
$\displaystyle xy = x \land y$    and $\displaystyle \qquad x + y = (x' \land y) \lor (x \land y').$

The category of Boolean algebras is naturally equivalent to the category of Boolean rings.

Bibliography

1
G. Grätzer, General Lattice Theory, 2nd Edition, Birkhäuser (1998).
2
R. Sikorski, Boolean Algebras, 2nd Edition, Springer-Verlag, New York (1964).



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See Also: Boolean ring

Other names:  Boolean algebra

Attachments:
Boolean ideal (Definition) by CWoo
example of Boolean algebras (Example) by CWoo
Boolean subalgebra (Definition) by CWoo
derived Boolean operations (Definition) by CWoo
Boolean quotient algebra (Definition) by CWoo
complete Boolean algebra (Definition) by CWoo
free Boolean algebra (Definition) by CWoo
Boolean algebra homomorphism (Definition) by CWoo
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Cross-references: naturally equivalent, equivalent, identity, commutative ring, characteristic, easy to see, unital ring, associative, subcategory, category, preserve, Boolean algebra homomorphism, algebraic system, unary, operators, lattice homomorphism, Boolean, morphism, complemented, complement, distributive lattice, Boolean ring
There are 60 references to this entry.

This is version 15 of Boolean lattice, born on 2002-02-24, modified 2008-04-29.
Object id is 2594, canonical name is BooleanLattice.
Accessed 19058 times total.

Classification:
AMS MSC03G10 (Mathematical logic and foundations :: Algebraic logic :: Lattices and related structures)
 06B20 (Order, lattices, ordered algebraic structures :: Lattices :: Varieties of lattices)
 03G05 (Mathematical logic and foundations :: Algebraic logic :: Boolean algebras)
 06E05 (Order, lattices, ordered algebraic structures :: Boolean algebras :: Structure theory)

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