# Questions tagged [character-varieties]

moduli of representations (Betti moduli), moduli of Higgs bundles (Dolbeault moduli), moduli of connections (de Rham moduli space), moduli of principal bundles (Čech moduli space), moduli of polygons, moduli of geometric structures, spin networks, skein theory, A-polynomial, higher Teichmüller theory

41
questions

**9**

votes

**2**answers

323 views

### Orbit of an irreducible representation of a surface group under that action of the mapping class group

Let $F$ be a closed oriented surface of negative Euler characteristic. Let $X^i(F)$ be the subset of the $SL_2\mathbb{C}$-character variety of the fundamental group of $F$ corresponding to irreducible ...

**1**

vote

**1**answer

146 views

### Lie bracket on the complex valued functions of the space of representations of a Riemann surface

Let $S$ be a closed surface and $G$ be a reductive Lie group. Goldman (Invariant functions on Lie groups and Hamiltonian flows of surface group representations) proved that, for a fairly general class ...

**9**

votes

**3**answers

600 views

### SL(2, C)-representation of a knot

When studying knot theory I often encounter $SL(2, \mathbb{C})$-representation of knots (of the knot group) or the $SL(2, \mathbb{C})$ character variety of a knot group. But I just don't seem to ...

**10**

votes

**1**answer

326 views

### A question about dimension of SL(2,C) character variety of knot group

It is known that if there isn't a closed essential surface in $S^3 \setminus K$, the dimension of $SL(2,\mathbb C)$ character variety is $1$. (In fact, it holds for a general 3-manifold, not only for ...

**10**

votes

**1**answer

447 views

### Moduli space of flat connections of Lie group over a 2-torus

We know that the moduli space of SU($N$) principal bundle's flat connections over a torus, is equivalent to a complex projective space $\mathbb{P}^{N-1}$
Namely,
$$
M_{\rm flat}=\mathbb{E} / {S}_N = \...

**5**

votes

**1**answer

157 views

### The ¨irreducible¨ representation variety of surface group

Let $S$ be a closed surface of genus larger than 1, $G$ be a compact, simply connected simple Lie group with finite center.
Consider the representation variety $M(S,G)=Rep(\pi_1(S), G)$. Witten´s ...

**3**

votes

**1**answer

123 views

### Kernel of restriction for ring of functions on reductive groups

Let $H \subset G$ be an inclusion of reductive groups over an algebraically closed field $k$ of char $0$. For simplicity, let's assume that $G$ is split and $H$ contains a maximal torus for $G$. Then ...

**2**

votes

**1**answer

162 views

### Metric on moduli space of semistable principal G-bundles on curves

Let $X$ be an irreducible smooth projective curve over $\mathbb{C}$. Let $G$ be a connected reductive linear algebraic group over $\mathbb{C}$. Let ${\rm M}_{G,X}$ be the moduli space of semistable ...

**6**

votes

**1**answer

200 views

### Compactifications of SL(2)-character varieties of surfaces

Thurston compactified the Teichmüller space ${\cal T}(F)$ of a closed, oriented surface $F$ with a piecewise-linear sphere. Furthermore, as far as I understand, its linear pieces have natural ...

**3**

votes

**0**answers

110 views

### Question on Neumann-Zagier Symplectic matrix of an ideal triangulation of one cusped 3-manifold

For a knot complement $M\backslash K$ on a general closed 3-manifold $M$, the gluing equations are given by ($k$ is the number of ideal tetrahedra in an ideal triangulation of $M\backslash K$)
$c_I:=\...

**2**

votes

**0**answers

99 views

### Non Seifert incompressible surfaces detected by ideal points

Given a 3-manifold with toric boundary, the Culler-Shalen theory associates an incompressible surface to any ideal point of its character variety. From the proof of the Neuwirth conjecture, one knows ...

**9**

votes

**1**answer

148 views

### Classification of geometric structures through character varieties

Under what general assumptions $(G,X)$-geometric structures on a manifold $M$ are classified by their holonomies, yielding an injection
$$\Psi: \{(G,X)\text{-structures on M}\} \to H(\pi_1(M),G)/G ?$$ ...

**8**

votes

**2**answers

448 views

### Flat connections on 3-manifold with boundary

Suppose $Y$ is a 3-manifold and the boundary $\Sigma:=\partial Y$ is non-empty. Let $G$ be a Lie group with trivial center. Let $\overline {\mathcal A}_{flat}(\Sigma)$ and $\overline {\mathcal A}_{...

**30**

votes

**4**answers

2k views

### Why do people study representations of 3-manifold groups into $SL(n,\mathbb{C})$?

Varieties of representations and characters of $3$-manifold groups in $SL(2,\mathbb{C})$ have been intensively studied. They have provided tools to identify geometric structures on manifolds, and are ...

**9**

votes

**3**answers

699 views

### Moduli spaces of connections as representation spaces

It is well known that the moduli space of flat connections over a closed manifold $M$ can be identified with the representation space $Hom(\pi_1(M), G) / G$.
Furthermore, Atiyah and Bott (1983) ...

**10**

votes

**7**answers

802 views

### Reference on representations of knot groups

Recently, I was studying knot groups and I wanted to learn some more material about them (e.g. their representations).
"Knots" by Burde and Zieschang discusses some material but it is not entirely ...

**12**

votes

**1**answer

955 views

### Representation varieties of 3-manifold groups in $\mathrm{SL}(n,\mathbb{C})$

I am looking at the variety of representations of the fundamental group of a hyperbolic 3-manifold into $\mathrm{SL}(n,\mathbb{C})$:
$$\mathrm{Hom}(\pi_1(M), \mathrm{SL}(n,{\mathbb C}))$$
It is known ...

**6**

votes

**0**answers

299 views

### Can the analytic arc of an irred. $\mathrm{SL}_2(\mathbb{C})$-character always be lifted to an analytic arc of an irred. representation?

Is there an example of an irreducible and boundary irreducible $3$-manifold $M$ with torus boundary and a non-abelian representation $\rho: \pi_1(M) \to \mathrm{SL}_2(\mathbb{C})$, a non-constant ...

**3**

votes

**1**answer

251 views

### When is an irreducible $\mathrm{SL}_2(\mathbb{C})$ representation of a cusped hyperbolic 3-manifold scheme reduced or smooth?

Let $M$ be an orientable cusped hyperbolic 3-manifold. Let $\rho \in \mathrm{Hom}(\pi_1(M),\mathrm{SL}_2(\mathbb{C}))$ be an irreducible representation.
Is $\rho$ scheme reduced ?
What can ...

**3**

votes

**1**answer

622 views

### Representation variety vs. space of flat connections

The holonomy provides a bijection from
the space of flat $G$-connections (modulo gauge equivalence) on a trivial $G$-bundle over $M$
to
a connected component of the representation variety $Hom(\...

**1**

vote

**1**answer

227 views

### Algebraicness of trace field of finite volume hyperbolic 3-manifold and dimension of $\mathrm{SL}(2,\mathbb{C})$-character variety

Does the following statement:
"Let $G$ be a finitely generated
group and let $X(G)$ be the
$SL(2,\mathbb{C})$-character variety
of $G$. Suppose $X(G)$ contains an
irreducible component $X_0$...

**3**

votes

**1**answer

258 views

### Relation between the Character variety of a knot $K\subset M$ and that of $M$

Suppose there is a knot $K\subset M$, where $M$ is a closed 3-manifold. What's the relation between $\chi(\pi_{1}(M-K))$ and $\chi(\pi_{1}(M))$?
Note: $\chi(G)$ means the $\text{SL}_{2}(C)$-...

**15**

votes

**1**answer

842 views

### Can the SL_2 character variety of a three-manifold be nonreduced?

Let $M^3$ be a three-manifold and consider the representation variety and the character variety of $M$:
$$Y=\operatorname{Hom}(\pi_1(M^3),\operatorname{SL}(2,\mathbb C))$$
$$X=\operatorname{Hom}(\pi_1(...

**12**

votes

**1**answer

1k views

### Rank two vector bundles on a curve of genus two

I recently learned of an interesting result of Narasimhan and Ramanan from 1969, which says that moduli space of rank two vector bundles with trivial determinant on a curve $X$ of genus two is ...

**9**

votes

**1**answer

513 views

### Character varieties of finitely generated groups

Consider the following situation: $\Gamma_0\leq\Gamma$ are both finitely generated groups and $\Gamma_0$ has finite index in $\Gamma$. The restriction gives a well defined map between the character ...

**9**

votes

**1**answer

599 views

### What is (explicitly) known about the SL(n,C) character varieties of 3-manifolds?

The $SL(2,{\bf C})$ character variety of a 3-manifold with 1-cusp $M$ (like a knot complement in the 3-sphere) essentially coincide with the variety defined by the A-polynomial. Those polynomials are ...

**11**

votes

**2**answers

437 views

### Cohomology of $T^n/W$ for compact Lie groups

Let $G$ be a compact, connected and simply connected Lie group.
Let $T\subset G$ be a maximal torus and let $W$ be the corresponding
Weyl group.
Then we have the diagonal action of $W$ on $T^{n}$ ...

**15**

votes

**0**answers

1k views

### Representations of quantum groups at roots of unity

I'm interested in the semisimplified category of representations of a quantum group at a root of unity. I've heard that simple objects in this category correspond to certain "integral" conjugacy ...

**13**

votes

**0**answers

555 views

### Generalization of Witten's computation of the volume of moduli space

Let $\Sigma$ be a Riemann surface, and let $X:=\operatorname{Hom}(\pi_1(\Sigma),\operatorname{SU}(2))/\operatorname{SU}(2)$ be the $\operatorname{SU}(2)$ character variety of $\pi_1(\Sigma)$.
There ...

**7**

votes

**2**answers

622 views

### Deriving the Hilbert spaces for Chern-Simons TQFTs with complex gauge group

One method for finding the Hilbert spaces corresponding to surfaces in Chern-Simons TQFT is by geometrically quantizing the phase space, which is just the character variety of the surface. I know that ...

**2**

votes

**1**answer

368 views

### Which bundles does the character variety parameterize?

For any Riemann surface with punctures $C$, and Lie group $G$, the character variety is the space of maps $\mathrm{Hom}(\pi_1(C), G)$.
I know that if $G= S_n$ (not a lie group), then $\mathrm{Hom}(\...

**3**

votes

**0**answers

200 views

### Is tensor product flat with respect to the Hitchin connection?

Let $M$ be a compact symplectic manifold equipped with a line bundle $\mathcal L$ with curvature $\omega$. Denote by $H^0(M,\mathcal L)$ the space of smooth global sections of $\mathcal L$ (this ...

**4**

votes

**1**answer

573 views

### How does one relate the monodromy of the KZ equations with the WRT representation of the braid group?

The KZ equations on the configuration space of $n$ distinct points in $\mathbb C$ give rise to a representation of $B_n$ on $V^{\otimes n}$, where $V$ is any given representation of $SL(2)$ (we'll ...

**4**

votes

**0**answers

321 views

### Do real polarization and Kahler polarization of character varieties of closed surfaces give equivalent representations of the Mapping Class Group?

This is a question about the Witten--Reshetikhin--Turaev representations of the mapping class group of a closed surface $\Sigma_g$. For simplicity, we'll stick to the case $G=SU(2)$.
These ...

**3**

votes

**1**answer

566 views

### How to interpret sections over the $\mathrm{SU}(2)$ character variety as sections over the $\mathrm{SL}(2,\mathbb{C})$ character variety?

The motivation for this question comes from the Volume Conjecture of Kashaev-Murakami-Murakami. The Jones family of invariants of knots and $3$-manifolds can all be defined using $\mathrm{SU}(2)$ and ...

**7**

votes

**2**answers

574 views

### What is the state in the WRT TQFT associated to a handlebody?

Let $Y^3$ be a handlebody with boundary $\Sigma$. By definition, there is some associated vector $v_{WRT}(Y^3)\in Z(\Sigma)$, the (finite dimensional) Hilbert space associated to $\Sigma$ by the ...

**14**

votes

**1**answer

821 views

### Is there an algebraic description of Yang-Mills measure?

Consider $X=\operatorname{Hom}(\pi,\mathrm{SL}(2,\mathbb C))/\! \!/\mathrm{SL}(2,\mathbb C)$ and $Y=\operatorname{Hom}(\pi,\mathrm{SU}(2))/\mathrm{SU}(2)$, where $\pi$ is a surface group. Note that ...

**11**

votes

**1**answer

1k views

### How nice are representation varieties of Fuchsian groups?

Background
Let $S_{g,n}$ be an oriented surface of genus $g$, with $n$ punctures. We explicitly prohibit the non-hyperbolic cases:
$g=0$, $n=0,1,2$.
$g=1$, $n=0$.
Let $\Gamma$ be the fundamental ...

**14**

votes

**1**answer

925 views

### Moduli space of semistable bundles

It is well-known that the space of $S$-equivalence classes of rank 2 semistable holomorphic vector bundles with trivial determinant on a genus 2 Riemann surface $M$ is $CP^3$ (more concretely $PH^0(...

**10**

votes

**3**answers

2k views

### Zariski tangent spaces to representation varieties

In Bill Goldman's paper "The Symplectic Nature of the Fundamental Groups of Surfaces" (Advances, 54, 200-225, '84) it is stated that the "Zariski tangent space" to a representation space Hom$(\pi, G)/...

**3**

votes

**2**answers

521 views

### SU(2) representations of alternating knot groups

Suppose that $K$ is an $\textit{alternating}$ knot in $S^3$, and let $R_0$ be the space of homomorphisms from $\pi_1(S^3 - K)\to SU(2)$ which send meridians to trace free matrices. Denote the subset ...