Minimal (clones with a Taylor operation)math.colorado.edu/algebralogic/marcin-kozik1.pdf · 2021....
Transcript of Minimal (clones with a Taylor operation)math.colorado.edu/algebralogic/marcin-kozik1.pdf · 2021....
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Minimal (clones with a Taylor operation)Marcin Kozikjoint work with: L. Barto, Z. Brady, A. Bulatov and D. Zhuk
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Notation and conventionsA clone C on A is a subset of
⋃i AAi which:
• contains all projections, and• is closed under composition.
I always identify a clone C on A with the algebra (A; C).
In 1977 Walter Taylor provided equations holding in every idempotentvariety, which “is not interpretable into Sets”.
Operations satsfying these equations are called Taylor operations.
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Notation and conventionsA clone C on A is a subset of
⋃i AAi which:
• contains all projections, and• is closed under composition.
I always identify a clone C on A with the algebra (A; C).
In 1977 Walter Taylor provided equations holding in every idempotentvariety, which “is not interpretable into Sets”.
Operations satsfying these equations are called Taylor operations.
Minimal (clones with a Taylor operation) | M. KozikPage 1
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Notation and conventionsA clone C on A is a subset of
⋃i AAi which:
• contains all projections, and• is closed under composition.
I always identify a clone C on A with the algebra (A; C).
In 1977 Walter Taylor provided equations holding in every idempotentvariety, which “is not interpretable into Sets”.
Operations satsfying these equations are called Taylor operations.
Minimal (clones with a Taylor operation) | M. KozikPage 1
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Notation and conventionsA clone C on A is a subset of
⋃i AAi which:
• contains all projections, and• is closed under composition.
I always identify a clone C on A with the algebra (A; C).
In 1977 Walter Taylor provided equations holding in every idempotentvariety, which “is not interpretable into Sets”.
Operations satsfying these equations are called Taylor operations.
Minimal (clones with a Taylor operation) | M. KozikPage 1
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We assume that:• all the universes are finite;• all the clones are idempotent (esentially for free).
A clone is Taylor if it contains a Taylor operation, or. . .
Definition (Taylor clone)A clone C on A is a Taylor clone if for every prime p > |A| there is c ∈ C:
c(x1, . . . , xp) = c(xp, x1, . . . , xp−1).
. . . and we know that, for a finite A, the definitions coincide.
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We assume that:• all the universes are finite;• all the clones are idempotent (esentially for free).
A clone is Taylor if it contains a Taylor operation, or. . .
Definition (Taylor clone)A clone C on A is a Taylor clone if for every prime p > |A| there is c ∈ C:
c(x1, . . . , xp) = c(xp, x1, . . . , xp−1).
. . . and we know that, for a finite A, the definitions coincide.
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We assume that:• all the universes are finite;• all the clones are idempotent (esentially for free).
A clone is Taylor if it contains a Taylor operation, or. . .
Definition (Taylor clone)A clone C on A is a Taylor clone if for every prime p > |A| there is c ∈ C:
c(x1, . . . , xp) = c(xp, x1, . . . , xp−1).
. . . and we know that, for a finite A, the definitions coincide.
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Definition (Minimal Taylor clone, MTC)A Taylor clone is minimal if it has no proper Taylor subclones.
Basic facts:
• Minimal Taylor clones do exist.• Every Taylor clone, has an MTC as a subclone.• Every Taylor operation of an MTC generates it.• . . .
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Definition (Minimal Taylor clone, MTC)A Taylor clone is minimal if it has no proper Taylor subclones.
Basic facts:• Minimal Taylor clones do exist.
• Every Taylor clone, has an MTC as a subclone.• Every Taylor operation of an MTC generates it.• . . .
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Definition (Minimal Taylor clone, MTC)A Taylor clone is minimal if it has no proper Taylor subclones.
Basic facts:• Minimal Taylor clones do exist.• Every Taylor clone, has an MTC as a subclone.
• Every Taylor operation of an MTC generates it.• . . .
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Definition (Minimal Taylor clone, MTC)A Taylor clone is minimal if it has no proper Taylor subclones.
Basic facts:• Minimal Taylor clones do exist.• Every Taylor clone, has an MTC as a subclone.• Every Taylor operation of an MTC generates it.
• . . .
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Definition (Minimal Taylor clone, MTC)A Taylor clone is minimal if it has no proper Taylor subclones.
Basic facts:• Minimal Taylor clones do exist.• Every Taylor clone, has an MTC as a subclone.• Every Taylor operation of an MTC generates it.• . . .
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Why?• Taylor clones are too complex.
• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;
• CSP dichotomy;• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
Minimal (clones with a Taylor operation) | M. KozikPage 4
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;
• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
Minimal (clones with a Taylor operation) | M. KozikPage 4
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;• structural descriptions?
• . . .• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
Minimal (clones with a Taylor operation) | M. KozikPage 4
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
Minimal (clones with a Taylor operation) | M. KozikPage 4
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Why?• Taylor clones are too complex.• MTCs are su�cient for e.g.
• Malcev conditions;• CSP dichotomy;• structural descriptions?• . . .
• and I will argue that MTCs are easier.
The idea follows Z. Brady’s work for “minimal SD(∧) clones”.
Minimal (clones with a Taylor operation) | M. KozikPage 4
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Overview
The plan of the talk:
• Some basic properties of MTCs.
• Absorption (Zhuk) in MTCs.• Edges (Bulatov) in MTCs.• Random properties of MTCs.• Open problems.
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Overview
The plan of the talk:
• Some basic properties of MTCs.• Absorption (Zhuk) in MTCs.
• Edges (Bulatov) in MTCs.• Random properties of MTCs.• Open problems.
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Overview
The plan of the talk:
• Some basic properties of MTCs.• Absorption (Zhuk) in MTCs.• Edges (Bulatov) in MTCs.
• Random properties of MTCs.• Open problems.
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Overview
The plan of the talk:
• Some basic properties of MTCs.• Absorption (Zhuk) in MTCs.• Edges (Bulatov) in MTCs.• Random properties of MTCs.
• Open problems.
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Overview
The plan of the talk:
• Some basic properties of MTCs.• Absorption (Zhuk) in MTCs.• Edges (Bulatov) in MTCs.• Random properties of MTCs.• Open problems.
Minimal (clones with a Taylor operation) | M. KozikPage 5
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Basic properties of MTCs
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FactLet C be an MTC on A, B ⊆ A and f ∈ C:• f (B, . . . ,B) = B,
• f|B is a Taylor operation on B.
Then B is a subuniverse of C.
Proof.
cA(cB(x1, . . . , xp), cB(x2, . . . , xp, x1), . . . , cB(xp, x1, . . . , xp−1))
is cyclic on A and preserves B.
In fact if C is an MTC, then so is every member of HSPfin(C).
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FactLet C be an MTC on A, B ⊆ A and f ∈ C:• f (B, . . . ,B) = B,• f|B is a Taylor operation on B.
Then B is a subuniverse of C.
Proof.
cA(cB(x1, . . . , xp), cB(x2, . . . , xp, x1), . . . , cB(xp, x1, . . . , xp−1))
is cyclic on A and preserves B.
In fact if C is an MTC, then so is every member of HSPfin(C).
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FactLet C be an MTC on A, B ⊆ A and f ∈ C:• f (B, . . . ,B) = B,• f|B is a Taylor operation on B.
Then B is a subuniverse of C.
Proof.
cA(cB(x1, . . . , xp), cB(x2, . . . , xp, x1), . . . , cB(xp, x1, . . . , xp−1))
is cyclic on A and preserves B.
In fact if C is an MTC, then so is every member of HSPfin(C).
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FactLet C be an MTC on A, B ⊆ A and f ∈ C:• f (B, . . . ,B) = B,• f|B is a Taylor operation on B.
Then B is a subuniverse of C.
Proof.
cA(cB(x1, . . . , xp), cB(x2, . . . , xp, x1), . . . , cB(xp, x1, . . . , xp−1))
is cyclic on A and preserves B.
In fact if C is an MTC, then so is every member of HSPfin(C).
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FactLet C be an MTC on A, B ⊆ A and f ∈ C:• f (B, . . . ,B) = B,• f|B is a Taylor operation on B.
Then B is a subuniverse of C.
Proof.
cA(cB(x1, . . . , xp), cB(x2, . . . , xp, x1), . . . , cB(xp, x1, . . . , xp−1))
is cyclic on A and preserves B.
In fact if C is an MTC, then so is every member of HSPfin(C).
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Absorption in MTCs
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Why do you keep talking aboutabsorption?
Theorem (Zhuk)Let C be a Taylor clone, then
1. C has a 2-absorbing subuniverse, or2. C has a 3-absorbing subuniverse, or3. C/α is abelian for some congruence α, or4. C/α is polynomially complete for some congruence α.
I.e.“Because we do not know anything better.”
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Why do you keep talking aboutabsorption?
Theorem (Zhuk)Let C be a Taylor clone, then
1. C has a 2-absorbing subuniverse, or2. C has a 3-absorbing subuniverse, or3. C/α is abelian for some congruence α, or4. C/α is polynomially complete for some congruence α.
I.e.“Because we do not know anything better.”
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Why do you keep talking aboutabsorption?
Theorem (Zhuk)Let C be a Taylor clone, then
1. C has a 2-absorbing subuniverse, or2. C has a 3-absorbing subuniverse, or3. C/α is abelian for some congruence α, or4. C/α is polynomially complete for some congruence α.
I.e.“Because we do not know anything better.”
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;
2. . . . as above and B is a subuniverse (2-absorption);3. . . . as above and every binary f ∈ C satisfies 1. (except projections);4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;2. . . . as above and B is a subuniverse (2-absorption);
3. . . . as above and every binary f ∈ C satisfies 1. (except projections);4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;2. . . . as above and B is a subuniverse (2-absorption);3. . . . as above and every binary f ∈ C satisfies 1. (except projections);
4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;2. . . . as above and B is a subuniverse (2-absorption);3. . . . as above and every binary f ∈ C satisfies 1. (except projections);4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;2. . . . as above and B is a subuniverse (2-absorption);3. . . . as above and every binary f ∈ C satisfies 1. (except projections);4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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2-absorption
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B) ∪ f (B,A) ⊆ B;2. . . . as above and B is a subuniverse (2-absorption);3. . . . as above and every binary f ∈ C satisfies 1. (except projections);4. if t ∈ C depends on i-th coordinate and ai ∈ B, then t(a1, . . . ,a?) ∈ B.
The clone C acts on B “as max on {0, 1}”.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;
2. . . . as above and B is a subuniverse (3-absorption);3. for every prime p > |A| there is a cyclic c ∈ C such that
c(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.Center = “3-absorbing subuniverse” in MTCs.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;2. . . . as above and B is a subuniverse (3-absorption);
3. for every prime p > |A| there is a cyclic c ∈ C such thatc(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.Center = “3-absorbing subuniverse” in MTCs.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;2. . . . as above and B is a subuniverse (3-absorption);3. for every prime p > |A| there is a cyclic c ∈ C such that
c(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.Center = “3-absorbing subuniverse” in MTCs.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;2. . . . as above and B is a subuniverse (3-absorption);3. for every prime p > |A| there is a cyclic c ∈ C such that
c(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.Center = “3-absorbing subuniverse” in MTCs.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;2. . . . as above and B is a subuniverse (3-absorption);3. for every prime p > |A| there is a cyclic c ∈ C such that
c(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.
Center = “3-absorbing subuniverse” in MTCs.
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3-absorption and center
FactLet C be an MTC on A and B ⊆ A. TFAE:
1. there is f ∈ C such that f (A,B,B) ∪ f (B,A,B) ∪ f (B,B,A) ⊆ B;2. . . . as above and B is a subuniverse (3-absorption);3. for every prime p > |A| there is a cyclic c ∈ C such that
c(a1, . . . ,ap) ∈ B whenever majority of arguments is in B.
The clone C acts on B “as maj on {0, 1}”.Center = “3-absorbing subuniverse” in MTCs.
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Absorption is strong in MTCsFactLet C be a MTC and B a 2-absorbing subuniverse, then• x = y ∨ (x ∈ B ∧ y ∈ B) is a congruence of C;
• if D is a subuniverse then so is D ∪ B.
There exist a unique, smallest 2-absorbing subuniverse of A.
FactLet C be a MTC and B,D be 3-absorbing subuniverses, then
• B ∪ D is a subuniverse;• if B ∩ D = ∅ then B2 ∪ D2 is a congruence on B ∪ D.
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Absorption is strong in MTCsFactLet C be a MTC and B a 2-absorbing subuniverse, then• x = y ∨ (x ∈ B ∧ y ∈ B) is a congruence of C;• if D is a subuniverse then so is D ∪ B.
There exist a unique, smallest 2-absorbing subuniverse of A.
FactLet C be a MTC and B,D be 3-absorbing subuniverses, then
• B ∪ D is a subuniverse;• if B ∩ D = ∅ then B2 ∪ D2 is a congruence on B ∪ D.
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Absorption is strong in MTCsFactLet C be a MTC and B a 2-absorbing subuniverse, then• x = y ∨ (x ∈ B ∧ y ∈ B) is a congruence of C;• if D is a subuniverse then so is D ∪ B.
There exist a unique, smallest 2-absorbing subuniverse of A.
FactLet C be a MTC and B,D be 3-absorbing subuniverses, then
• B ∪ D is a subuniverse;• if B ∩ D = ∅ then B2 ∪ D2 is a congruence on B ∪ D.
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Absorption is strong in MTCsFactLet C be a MTC and B a 2-absorbing subuniverse, then• x = y ∨ (x ∈ B ∧ y ∈ B) is a congruence of C;• if D is a subuniverse then so is D ∪ B.
There exist a unique, smallest 2-absorbing subuniverse of A.
FactLet C be a MTC and B,D be 3-absorbing subuniverses, then• B ∪ D is a subuniverse;
• if B ∩ D = ∅ then B2 ∪ D2 is a congruence on B ∪ D.
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Absorption is strong in MTCsFactLet C be a MTC and B a 2-absorbing subuniverse, then• x = y ∨ (x ∈ B ∧ y ∈ B) is a congruence of C;• if D is a subuniverse then so is D ∪ B.
There exist a unique, smallest 2-absorbing subuniverse of A.
FactLet C be a MTC and B,D be 3-absorbing subuniverses, then• B ∪ D is a subuniverse;• if B ∩ D = ∅ then B2 ∪ D2 is a congruence on B ∪ D.
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Edges in MTCs
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and
• θ a congruence on E,
there is
• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is
• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};
• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};
• abelian type: C on E/θ is an abelian clone.An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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DefinitionLet C be a clone on A. A pair (a,b) ∈ A2 is an edge if for:• E = SgC(a,b), and• θ a congruence on E,
there is• semilattice type: f ∈ C so that f on {a/θ,b/θ} is max on {0, 1};• majority type: m ∈ C so that m on {a/θ,b/θ} is maj on {0, 1};• abelian type: C on E/θ is an abelian clone.
An edge (a,b) is minimal if [...] (a,a′), (b,b′) ∈ θ implies E = SgC(a′,b′).
A graph of an algebra is connected.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;
2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;
3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};
4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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FactLet C be a MTC and (a,b) an edge:
1. if the type is semilattice or majority then E = a/θ ∪ b/θ;2. if the edge is minimal, then the type is unique;3. if the type is semilattice and the edge is minimal then E = {a,b};4. . . .
Set B is stable if, for every edge (a,b), a/θ ∩ B 6= ∅ implies b/θ ∩ B 6= ∅.
TheoremIn an MTC a subset is 2-absorbing if and only if it is stable.
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Random properties of MTCs
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FactLet C be a MTC on A.• C is generated by a cyclic operation of prime arity > |A|.• C is generated by a Siggers operation: s(a, r, e,a) = s(r,a, r, e).• C is generated by a ternary operation (any operation witnessing all
the edges generates C).
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Open problems
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?
• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:
• Can we derive the more advanced properties of Bulatov and Zhuk?How about commutator theory?
• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?
• Can we characterize 3-absorption using edges?• . . .
Some more general questions:
• Can we derive the more advanced properties of Bulatov and Zhuk?How about commutator theory?
• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?
• . . .
Some more general questions:
• Can we derive the more advanced properties of Bulatov and Zhuk?How about commutator theory?
• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:
• Can we derive the more advanced properties of Bulatov and Zhuk?How about commutator theory?
• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:• Can we derive the more advanced properties of Bulatov and Zhuk?
How about commutator theory?
• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:• Can we derive the more advanced properties of Bulatov and Zhuk?
How about commutator theory?• How about TCT in MTCs?
• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:• Can we derive the more advanced properties of Bulatov and Zhuk?
How about commutator theory?• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?
• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Some (embarrassing) open questions:• Does every {a,b} form an edge of an MTC?• Can we characterize stability under special types of edges?• Can we characterize 3-absorption using edges?• . . .
Some more general questions:• Can we derive the more advanced properties of Bulatov and Zhuk?
How about commutator theory?• How about TCT in MTCs?• Can a structural characterization of MTCs be proposed?• and extended to Taylor clones, or general algebras?
Minimal (clones with a Taylor operation) | M. KozikPage 19
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Under the hood
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Some proofs are nice, for example:Relations are:• all subdirect,
• proper if “not full”,• redundant if “some binary projection is a graph of a bijection”,• strongly functional if “every permutation is a graph of a 2-function”.
TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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Some proofs are nice, for example:Relations are:• all subdirect,• proper if “not full”,
• redundant if “some binary projection is a graph of a bijection”,• strongly functional if “every permutation is a graph of a 2-function”.
TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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Some proofs are nice, for example:Relations are:• all subdirect,• proper if “not full”,• redundant if “some binary projection is a graph of a bijection”,
• strongly functional if “every permutation is a graph of a 2-function”.TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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Some proofs are nice, for example:Relations are:• all subdirect,• proper if “not full”,• redundant if “some binary projection is a graph of a bijection”,• strongly functional if “every permutation is a graph of a 2-function”.
TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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Some proofs are nice, for example:Relations are:• all subdirect,• proper if “not full”,• redundant if “some binary projection is a graph of a bijection”,• strongly functional if “every permutation is a graph of a 2-function”.
TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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Some proofs are nice, for example:Relations are:• all subdirect,• proper if “not full”,• redundant if “some binary projection is a graph of a bijection”,• strongly functional if “every permutation is a graph of a 2-function”.
TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
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TheoremLet R be an irredundant proper relation• R pp-defines binary irredundant and proper, or• there exist ternary strongly functional R1, . . . ,Rn such that the set{R1, . . . ,Rm} is inter-pp-definable with R.
implies (with some e�ort)
Theorem (Zhuk)Let C be a Taylor clone, then
1. C has a 2-absorbing subuniverse, or2. C has a 3-absorbing subuniverse, or3. C/α is abelian for some congruence α, or4. C/α is polynomially complete for some congruence α.
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Some content is fragile, for example:A clone on {0, 1, 2} is generated by m(a,b, c) =
=
{0 if{a,b, c} = {0, 1, 2}maj(a,b, c) otherwise;
• m is cyclic;• three majority edges;• Clo(m) is an MTC;
=
{0 if{a,b, c} ⊇ {1, 2}maj(a,b, c) otherwise;
• m is cyclic;• clone is simple;• at least two majority edges;• Clo(m) is not an MTC.
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Some content is fragile, for example:A clone on {0, 1, 2} is generated by m(a,b, c) =
=
{0 if{a,b, c} = {0, 1, 2}maj(a,b, c) otherwise;
• m is cyclic;• three majority edges;• Clo(m) is an MTC;
=
{0 if{a,b, c} ⊇ {1, 2}maj(a,b, c) otherwise;
• m is cyclic;• clone is simple;• at least two majority edges;• Clo(m) is not an MTC.
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