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Upper and Lower Semimodularity of theSupercharacter Theory Lattices of Cyclic Groups
Samuel Benidt, William Hall, & Anders Hendrickson
ΠME ConferenceSt. John’s University
April 17, 2010
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DefinitionsOur Work
Two main theorems
Outline
1 DefinitionsLatticesSupercharacter Theories
2 Our WorkGoals and StrategyAnalysis of Specific Cases
3 Two main theoremsUpper SemimodularityLower Semimodularity
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Lattices
As you may know, a partially ordered set is a set with an order thatrequires the following for elements a, b in the set:
either a ≤ b
or a ≥ b
or a and b are incomparable
A good example of a poset is set inclusion: either A ⊆ B, or B ⊆ A, orneither.
Definition
A lattice is a partially ordered set in which any two elements a and bhave a unique least upper bound, a ∨ b, and greatest lower bound, a ∧ b.We read a ∨ b as “a join b” and a ∧ b as “a meet b”.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples
e
d
cb
a
e
d
cb
a
A Lattice
Not a lattice
Definition
We say an element b of a lattice covers another element d if b ≥ d andthere are no elements between b and d . We write d � b.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples
e
d
cb
a
e
d
cb
a
A Lattice Not a lattice
Definition
We say an element b of a lattice covers another element d if b ≥ d andthere are no elements between b and d . We write d � b.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples
e
d
cb
a
e
d
cb
a
A Lattice Not a lattice
Definition
We say an element b of a lattice covers another element d if b ≥ d andthere are no elements between b and d . We write d � b.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 7: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/7.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Upper Semimodularity
Definition
A lattice L of finite length, is said to be upper semimodular if thefollowing condition is satisfied:
if a ∧ b � a, b then a, b � a ∨ b.
⇒
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Upper Semimodularity
Definition
A lattice L of finite length, is said to be upper semimodular if thefollowing condition is satisfied:
if a ∧ b � a, b then a, b � a ∨ b.
⇒
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples of some USM Lattices
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 10: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/10.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Lower Semimodularity
Definition
Let L be a lattice of finite length. Then L is lower semimodular if for alla, b ∈ L,
if a, b � a ∨ b then a ∧ b � a, b
⇒
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Lower Semimodularity
Definition
Let L be a lattice of finite length. Then L is lower semimodular if for alla, b ∈ L,
if a, b � a ∨ b then a ∧ b � a, b
⇒
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples of some LSM Lattices
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 13: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/13.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples of some LSM Lattices
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 14: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/14.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Examples of some LSM Lattices
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 15: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/15.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Notes on Groups
In our presentation, we’ll be focusing exclusively on finite cyclicgroups and their subgroups.
Note that since every group we’ll be discussing is Abelian, eachsubgroup N is normal.
This means that the quotient group G/N exists.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Supercharacter Theory
Definition
Let G be a finite group and let K be a partition of G .Then we say K is a superchacter theory if the following three conditionshold:
{1} is a part of K .
A product of sums of parts of K is a linear combination of sums ofparts of K .
Each part of K is a union of some conjugacy classes of G .
Sup(G ) denotes the set of all supercharacter theories of the group G ; itforms a lattice.
Supercharacter theories were defined in a 2008 paper by P. Diaconisand I.M. Isaacs.
They are the subject of very active study and the topic of anAmerican Institute of Mathematics workshop this May.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Supercharacter Theory
Definition
Let G be a finite group and let K be a partition of G .Then we say K is a superchacter theory if the following three conditionshold:
{1} is a part of K .
A product of sums of parts of K is a linear combination of sums ofparts of K .
Each part of K is a union of some conjugacy classes of G .
Sup(G ) denotes the set of all supercharacter theories of the group G ; itforms a lattice.
Supercharacter theories were defined in a 2008 paper by P. Diaconisand I.M. Isaacs.
They are the subject of very active study and the topic of anAmerican Institute of Mathematics workshop this May.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 18: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/18.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Supercharacter Theory
Definition
Let G be a finite group and let K be a partition of G .Then we say K is a superchacter theory if the following three conditionshold:
{1} is a part of K .
A product of sums of parts of K is a linear combination of sums ofparts of K .
Each part of K is a union of some conjugacy classes of G .
Sup(G ) denotes the set of all supercharacter theories of the group G ; itforms a lattice.
Supercharacter theories were defined in a 2008 paper by P. Diaconisand I.M. Isaacs.
They are the subject of very active study and the topic of anAmerican Institute of Mathematics workshop this May.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 19: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/19.jpg)
DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Sup(G ) as a Lattice
Given X , Y ∈ Sup(G ), we can find their join and meet, so Sup(G ) is alattice.
a1
���a2, a3
���a4 a1, a2
���a3
���a4
X ∧ Y
X ∨ Y
X Y
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Sup(G ) as a Lattice
Given X , Y ∈ Sup(G ), we can find their join and meet, so Sup(G ) is alattice.
a1
���a2, a3
���a4 a1, a2
���a3
���a4
a1, a2, a3
���a4
X ∧ Y
X ∨ Y
X Y
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Sup(G ) as a Lattice
Given X , Y ∈ Sup(G ), we can find their join and meet, so Sup(G ) is alattice.
a1
���a2, a3
���a4 a1, a2
���a3
���a4
a1, a2, a3
���a4
a1
���a2
���a3
���a4
X ∧ Y
X ∨ Y
X Y
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Some Examples: Sup(Z3)
Figure: The graph of Sup(Z3)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Some Examples: Sup(Z17)
Figure: The graph of Sup(Z17)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Some Examples: Sup(Z51)
Figure: The graph of Sup(Z51)Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
Finding Supercharacter Theories
There are several methods of constructing supercharacter theories of agroup, including the following:
minimal supercharacter theory: m(Zn)m(Zn) is formed by placing each group element in its own part.This partition will always be the least element in the lattice.
maximal supercharacter theory: M(Zn)M(Zn) is formed by placing all group elements in two parts:{1}, and all other group elements.This partition will always be the greatest element in the lattice.
inverse supercharacter theory: Inv(Zn) = {1/g , g−1/g2, g−2/...}We define the inverse supercharacter theory by placing each groupelement and its inverse together in their own part.
partition the elements by their orders: A(Zn)
∗-product supercharacter theory: X ∗ Y ,where X ∈ Sup(N) and Y ∈ Sup(G/N).
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
∗-product
As mentioned on the previous slide, one way to find supercharactertheories is a method called the ∗-product.
Let N be normal in G with X ∈ Sup(N), Y ∈ Sup(G/N).Then X ∗ Y ∈ Sup(G ).
X Y
X ∗ Y
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
∗-product
As mentioned on the previous slide, one way to find supercharactertheories is a method called the ∗-product.
Let N be normal in G with X ∈ Sup(N), Y ∈ Sup(G/N).Then X ∗ Y ∈ Sup(G ).
X Y
X ∗ Y
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
LatticesSupercharacter Theories
∗-product
As mentioned on the previous slide, one way to find supercharactertheories is a method called the ∗-product.
Let N be normal in G with X ∈ Sup(N), Y ∈ Sup(G/N).Then X ∗ Y ∈ Sup(G ).
X Y
X ∗ YBenidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Research Goal
Research Goal
We seek necessary and sufficient conditions for when Sup(G )is upper- and lower-semimodular.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Inheritance Lemma
Lemma (Inheritance)
Let N be a subgroup of cyclic group G. Then
1 If Sup(N) is not upper semimodular, then Sup(G ) is not uppersemimodular.
2 If Sup(N) is not lower semimodular, then Sup(G ) is not lowersemimodular.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p
p2 pq pqr 4p 4
USM
Yes No∗ No No No Yes
LSM
Yes No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p
Lemma
Given a group G of order p, Sup(G ) is isomorphic to the subgroup latticeof the automorphism group of G.
Lemma
It is a well-known fact in lattice theory that the subgroup lattice of anAbelian group is both USM and LSM.
Therefore, Sup(G ) is both USM and LSM.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p
Lemma
Given a group G of order p, Sup(G ) is isomorphic to the subgroup latticeof the automorphism group of G.
Lemma
It is a well-known fact in lattice theory that the subgroup lattice of anAbelian group is both USM and LSM.
Therefore, Sup(G ) is both USM and LSM.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p
Lemma
Given a group G of order p, Sup(G ) is isomorphic to the subgroup latticeof the automorphism group of G.
Lemma
It is a well-known fact in lattice theory that the subgroup lattice of anAbelian group is both USM and LSM.
Therefore, Sup(G ) is both USM and LSM.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Example of |G | = p
〈[1]〉
〈[18]〉 〈[7]〉
〈[8]〉 〈[4]〉
〈[2]〉
Lattice of Sup(Z19) Lattice of subgroupsof Aut(Z19)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p
p2 pq pqr 4p 4
USM
Yes No∗ No No No Yes
LSM
Yes No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p
p2 pq pqr 4p 4
USM Yes
No∗ No No No Yes
LSM Yes
No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2
pq pqr 4p 4
USM Yes
No∗ No No No Yes
LSM Yes
No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p2, if p is odd
If G is cyclic of order p2, p an odd prime,then Sup(G ) contains the following sublattice.
m(Zp2 )
m(Zp) ∗m(Zp) Inv(Zp2 )
Inv(Zp) ∗m(Zp)m(Zp) ∗ Inv(Zp)
Inv(Zp) ∗ Inv(Zp)
Note that each line drawn in on this particular diagram indicates acovering relation, and each element listed is distinct from the others.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 40: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/40.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p2, if p is odd
If G is cyclic of order p2, p an odd prime,then Sup(G ) contains the following sublattice.
m(Zp2 )
m(Zp) ∗m(Zp) Inv(Zp2 )
Inv(Zp) ∗m(Zp)m(Zp) ∗ Inv(Zp)
Inv(Zp) ∗ Inv(Zp)
Note that each line drawn in on this particular diagram indicates acovering relation, and each element listed is distinct from the others.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 41: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/41.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = p2, if p is odd
If G is cyclic of order p2, p an odd prime,then Sup(G ) contains the following sublattice.
m(Zp2 )
m(Zp) ∗m(Zp) Inv(Zp2 )
Inv(Zp) ∗m(Zp)m(Zp) ∗ Inv(Zp)
Inv(Zp) ∗ Inv(Zp)
Note that each line drawn in on this particular diagram indicates acovering relation, and each element listed is distinct from the others.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 42: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/42.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = 4
m(Z4)
M(Z2) ∗M(Z2)
M(Z4)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2
pq pqr 4p 4
USM Yes
No∗ No No No Yes
LSM Yes
No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2
pq pqr 4p
4USM Yes No∗
No No No
YesLSM Yes No∗
Yes No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 45: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/45.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq
pqr 4p
4USM Yes No∗
No No No
YesLSM Yes No∗
Yes No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
USM Case for |G | = pq
m(Zpq)
m(Zp) ∗m(Zq) m(Zq) ∗m(Zp)
M(Zp) ∗M(Zq)
M(Zpq)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 47: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/47.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
USM Case for |G | = pq
m(Zpq)
m(Zp) ∗m(Zq) m(Zq) ∗m(Zp)
M(Zp) ∗M(Zq)
M(Zpq)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 48: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/48.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq
pqr 4p
4USM Yes No∗
No No No
YesLSM Yes No∗
Yes No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 49: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/49.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq
pqr 4p
4USM Yes No∗ No
No No
YesLSM Yes No∗
Yes No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
LSM Case for |G | = pq
Lemma
Let G be a cyclic group of order pq. Then Sup(G ) is lower semimodular.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq
pqr 4p
4USM Yes No∗ No
No No
YesLSM Yes No∗
Yes No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 52: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/52.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq
pqr 4p
4USM Yes No∗ No
No No
YesLSM Yes No∗ Yes
No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 53: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/53.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No
No No
YesLSM Yes No∗ Yes
No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 54: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/54.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes
No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 55: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/55.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = pqr
Aut(Zpq) ∗M(Zr )
M(Zp) ∗M(Zq) ∗M(Zr )
M(Zq) ∗M(Zpr )M(Zp) ∗M(Zqr )
M(Zpqr )
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 56: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/56.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = pqr
Aut(Zpq) ∗M(Zr )
M(Zp) ∗M(Zq) ∗M(Zr )
M(Zq) ∗M(Zpr )M(Zp) ∗M(Zqr )
M(Zpqr )
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 57: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/57.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes
No No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 58: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/58.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No
No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 59: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/59.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = 4p, if p is odd
A(Z2p) ∗M(Z2)
M(Z2) ∗M(Zp) ∗M(Z2) M(Zp) ∗M(Z2) ∗M(Z2)
M(Z2) ∗M(Z2p) M(Zp) ∗M(Z4)
M(Z4p)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = 4p, if p is odd
A(Z2p) ∗M(Z2)
M(Z2) ∗M(Zp) ∗M(Z2) M(Zp) ∗M(Z2) ∗M(Z2)
M(Z2) ∗M(Z2p) M(Zp) ∗M(Z4)
M(Z4p)
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = 4p, if p is even
G ∼= Z8
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 62: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/62.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Case where |G | = 4p, if p is even
G ∼= Z8
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 63: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/63.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No
No
Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 64: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/64.jpg)
DefinitionsOur Work
Two main theorems
Goals and StrategyAnalysis of Specific Cases
Summary Table
Summary Table
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
∗for odd primes p
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 65: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/65.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
Upper Semimodularity Theorem
Theorem (USM)
Let G be a cyclic group. Then Sup(G ) is upper semimodular if and onlyif the order of G is prime or four.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is USM:
If |G | = p, then we proved that Sup(G ) is USM.
If |G | = 4, we verified that this supercharacter theory lattice is USM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 67: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/67.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof
p p2 pq pqr 4p 4USM YesYes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is USM:
If |G | = p, then we proved that Sup(G ) is USM.
If |G | = 4, we verified that this supercharacter theory lattice is USM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 68: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/68.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesYesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is USM:
If |G | = p, then we proved that Sup(G ) is USM.
If |G | = 4, we verified that this supercharacter theory lattice is USM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 69: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/69.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is USM:
If |G | = p, then we proved that Sup(G ) is USM.
If |G | = 4, we verified that this supercharacter theory lattice is USM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 70: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/70.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
If |G | is not prime or four, then it is either a multiple of two distinctprimes or a prime power.
For |G | = k · pq, where p 6= q, then we showed that Sup(Zpq) is notUSM. By the Inheritance Lemma, Sup(G ) is not USM either.
For |G | = pn, where p 6= 2 and n ≥ 2, we again showed thatSup(Zp2) is not USM. Then, by the Inheritance Lemma, Sup(G ) isnot USM.
This leaves |G | = 2n with n ≥ 3. We verified that Sup(Z8) is notUSM, and thus, for all higher 2-powers, Sup(G ) is not USM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ NoNo No No YesLSM Yes No∗ Yes No No Yes
If |G | is not prime or four, then it is either a multiple of two distinctprimes or a prime power.
For |G | = k · pq, where p 6= q, then we showed that Sup(Zpq) is notUSM. By the Inheritance Lemma, Sup(G ) is not USM either.
For |G | = pn, where p 6= 2 and n ≥ 2, we again showed thatSup(Zp2) is not USM. Then, by the Inheritance Lemma, Sup(G ) isnot USM.
This leaves |G | = 2n with n ≥ 3. We verified that Sup(Z8) is notUSM, and thus, for all higher 2-powers, Sup(G ) is not USM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗No∗ No No No YesLSM Yes No∗ Yes No No Yes
If |G | is not prime or four, then it is either a multiple of two distinctprimes or a prime power.
For |G | = k · pq, where p 6= q, then we showed that Sup(Zpq) is notUSM. By the Inheritance Lemma, Sup(G ) is not USM either.
For |G | = pn, where p 6= 2 and n ≥ 2, we again showed thatSup(Zp2) is not USM. Then, by the Inheritance Lemma, Sup(G ) isnot USM.
This leaves |G | = 2n with n ≥ 3. We verified that Sup(Z8) is notUSM, and thus, for all higher 2-powers, Sup(G ) is not USM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No NoNo YesLSM Yes No∗ Yes No No Yes
If |G | is not prime or four, then it is either a multiple of two distinctprimes or a prime power.
For |G | = k · pq, where p 6= q, then we showed that Sup(Zpq) is notUSM. By the Inheritance Lemma, Sup(G ) is not USM either.
For |G | = pn, where p 6= 2 and n ≥ 2, we again showed thatSup(Zp2) is not USM. Then, by the Inheritance Lemma, Sup(G ) isnot USM.
This leaves |G | = 2n with n ≥ 3. We verified that Sup(Z8) is notUSM, and thus, for all higher 2-powers, Sup(G ) is not USM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 74: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/74.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
USM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
If |G | is not prime or four, then it is either a multiple of two distinctprimes or a prime power.
For |G | = k · pq, where p 6= q, then we showed that Sup(Zpq) is notUSM. By the Inheritance Lemma, Sup(G ) is not USM either.
For |G | = pn, where p 6= 2 and n ≥ 2, we again showed thatSup(Zp2) is not USM. Then, by the Inheritance Lemma, Sup(G ) isnot USM.
This leaves |G | = 2n with n ≥ 3. We verified that Sup(Z8) is notUSM, and thus, for all higher 2-powers, Sup(G ) is not USM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 75: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/75.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
Lower Semimodularity Theorem
Theorem (LSM)
Let G be a cyclic group. Then Sup(G ) is lower semimodular if and only ifthe order of G is prime, the product of two distinct primes, or four.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 76: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/76.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is LSM:
When |G | = p, Sup(G ) is lattice-isomorphic to the lattice C ofsubgroups of Aut(G ). Since C is LSM, Sup(G ) is also.
When |G | = pq, where p 6= q, a previously-stated lemma provedthat Sup(G ) is LSM.
When |G | = 4, we verified that this supercharacter theory lattice isLSM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 77: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/77.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM YesYes No∗ Yes No No Yes
Cases where cyclic group G is LSM:
When |G | = p, Sup(G ) is lattice-isomorphic to the lattice C ofsubgroups of Aut(G ). Since C is LSM, Sup(G ) is also.
When |G | = pq, where p 6= q, a previously-stated lemma provedthat Sup(G ) is LSM.
When |G | = 4, we verified that this supercharacter theory lattice isLSM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 78: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/78.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ YesYes No No Yes
Cases where cyclic group G is LSM:
When |G | = p, Sup(G ) is lattice-isomorphic to the lattice C ofsubgroups of Aut(G ). Since C is LSM, Sup(G ) is also.
When |G | = pq, where p 6= q, a previously-stated lemma provedthat Sup(G ) is LSM.
When |G | = 4, we verified that this supercharacter theory lattice isLSM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 79: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/79.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No YesYes
Cases where cyclic group G is LSM:
When |G | = p, Sup(G ) is lattice-isomorphic to the lattice C ofsubgroups of Aut(G ). Since C is LSM, Sup(G ) is also.
When |G | = pq, where p 6= q, a previously-stated lemma provedthat Sup(G ) is LSM.
When |G | = 4, we verified that this supercharacter theory lattice isLSM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 80: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/80.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Cases where cyclic group G is LSM:
When |G | = p, Sup(G ) is lattice-isomorphic to the lattice C ofsubgroups of Aut(G ). Since C is LSM, Sup(G ) is also.
When |G | = pq, where p 6= q, a previously-stated lemma provedthat Sup(G ) is LSM.
When |G | = 4, we verified that this supercharacter theory lattice isLSM.
What happens for other orders of G?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 81: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/81.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 82: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/82.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 83: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/83.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 84: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/84.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No NoNo Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 85: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/85.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 86: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/86.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 87: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/87.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No NoNo Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 88: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/88.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes NoNo No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 89: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/89.jpg)
DefinitionsOur Work
Two main theorems
Upper SemimodularityLower Semimodularity
LSM Proof cont.
p p2 pq pqr 4p 4USM Yes No∗ No No No YesLSM Yes No∗ Yes No No Yes
Suppose |G | is not p, pq, or 4.Consider the number of distinct prime factors of |G |.
1: If |G | = pa, then
If p is odd, then p2��|G |. So Sup(G) is not LSM.
If p is even, then 4p = 8��|G |, so Sup(G) is not LSM.
2: If |G | = paqb, then wlog a ≥ 2.
If p is odd, then p2��|G |, so Sup(G) is not LSM.
If p = 2, then 4q��|G | so Sup(G) is not LSM.
≥ 3: If |G | has at least 3 distinct prime factors,then pqr
��|G |, so Sup(G ) is not LSM. 2
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
![Page 90: Upper and Lower Semimodularity of the Supercharacter ...faculty.cord.edu/ahendric/studenttalks/BenidtHallCollegeville2010.pdf · We say an element b of a lattice covers another element](https://reader033.vdocuments.mx/reader033/viewer/2022050114/5f4b05f7d79eb544f85821d4/html5/thumbnails/90.jpg)
Acknowledgments
We’d like to thank Dr. Hendrickson for inviting us to research withhim and guiding us through the project.
Also, thanks to Concordia College for the financial support.
Lastly, we’d like to thank the organizers of the St. John’s Pi MuEpsilon conference.
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups
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Questions?
Benidt, Hall, Hendrickson Modularity Conditions of Lattices of Cyclic Groups