modular group PSL(2,Z)

E169191

The modular group PSL(2,ℤ) is a fundamental discrete group of 2×2 integer matrices modulo sign, acting by fractional linear transformations on the upper half-plane and playing a central role in number theory, geometry, and the theory of modular forms.

All labels observed (5)

Label Occurrences
modular group PSL(2,Z) canonical 4
PSL(2,ℤ) 3
PSL(2,Z) 1

How this entity was disambiguated

Statements (49)

Predicate Object
instanceOf Fuchsian group
arithmetic group
discrete group
matrix group
modular group
actionFormula z ↦ (az + b)/(cz + d) for matrix [[a,b],[c,d]]
actsBy fractional linear transformations
actsOn upper half-plane ℍ
actsProperlyDiscontinuouslyOn upper half-plane ℍ
cofiniteVolumeIn PSL(2,ℝ)
commensurableWith SL(2,ℤ)
containsSubgroup principal congruence subgroup Γ(N)
Γ(2)
Γ₀(N)
Γ₁(N)
definedAs SL(2,ℤ)/{±I}
fundamentalDomain {z ∈ ℍ : |Re(z)| ≤ 1/2, |z| ≥ 1}
generatedBy S
T
generatorAction S:z ↦ -1/z
T:z ↦ z+1
hasAbelianization C₆
hasCenter trivial group
hasCocompactLatticeProperty false
hasCusp
hasElementOfOrder 2
3
hasFiniteAreaQuotient ℍ/PSL(2,ℤ)
hasQuotient PSL(2,ℤ/Nℤ)
hasTorsion true
hasUnderlyingSet 2×2 integer matrices with determinant 1 modulo ±I
hasWordProblem decidable
isCountable true
isFinitelyGenerated true
isFinitelyPresented true
isLatticeIn PSL(2,ℝ)
isNonAbelian true
isomorphicTo free product C₂ * C₃
isQuotientOf SL(2,ℤ)
kernelOfProjectionFrom {±I} in SL(2,ℤ)
presentation ⟨S,T | S² = 1, (ST)³ = 1⟩
quotientIs modular orbifold
rankOverℤ 2 as free product C₂ * C₃
relatedTo Riemann surfaces
Teichmüller theory
automorphic forms
elliptic curves
modular forms

How these facts were elicited

Referenced by (10)

Full triples — surface form annotated when it differs from this entity's canonical label.

Conway’s topograph relatedTo modular group PSL(2,Z)
Farey tessellation isInvariantUnder modular group PSL(2,Z)
Farey tessellation hasSymmetryGroup PSL(2,Z)
linked to: modular group PSL(2,Z)
Fuchsian group isRelatedTo modular group PSL(2,Z)
modular j-invariant invariantUnder modular group
linked to: modular group PSL(2,Z)
T : z ↦ z + 1 belongsToGroup PSL(2,ℤ)
subject linked to: T:z ↦ z+1
linked to: modular group PSL(2,Z)
PSL(2,ℤ/Nℤ) relatedTo modular group PSL(2,ℤ)
linked to: modular group PSL(2,Z)
PSL(2,ℤ/Nℤ) isResiduallyFiniteImageOf PSL(2,ℤ)
linked to: modular group PSL(2,Z)
PSL(2,ℤ/Nℤ) hasNaturalHomomorphismFrom PSL(2,ℤ)
linked to: modular group PSL(2,Z)
Farey sequence relatedTo modular group PSL(2,Z)