#24172 ⟨
a
,
b
|
aa
=
a
,
babbbab
=
a
⟩
Up:
Monoids with two generators and two relations
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#24171
⟨
a
,
b
|
aa
=
a
,
babbabb
=
b
⟩
Next:
#24173
⟨
a
,
b
|
aa
=
a
,
babbbab
=
b
⟩
Quick links
Properties
Staircase diagram
Rewriting system
Properties
Presentation has sum-of-sides 11
Infinite non-cancellative commutative monoid
Not cancellative, because multiplication by
ab
is not injective:
ab
⋅
a
=
ab
and
ab
⋅ 1 =
ab
, however
a
≠ 1
Commutative Gröbner basis: ⟨
a
,
b
|
a
2
=
a
,
a
b
5
=
a
⟩
Cancellative quotient is isomorphic to ℤ
5
Enveloping group is isomorphic to ℤ
5
Group of units is isomorphic to ℤ
1
3 Archimedian components:
1,
a
,
b
Staircase diagram
Rewriting system
Format:
Pretty
Plain
Word to reduce:
Tips:
Lowercase letters stand for generators.
Spaces are ignored.
Numbers repeat the previous letter, e.g.
b90
.
Reduction strategy:
Leftmost
Rightmost
Path to normal form:
1
1
Reduction order:
Left-to-right shortlex with
a
<
b
Certificate
: derivations of all rewriting rules from the defining relations.
#
Rule
Proof
1.
a
2
⇒
a
[1]
2.
ba
⇒
ab
[10]
3.
a
b
5
⇒
a
[11]
# ab:aa=a,babbbab=a ab aa=a ba=ab abbbbb=a
