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48 results for faithful representations

The Burau representation of 3-strand braid group modulo p is determined and shown to be faithful for small p.

problem Determining the faithfulness of the Burau representation of B3B_3 modulo pp.
method Algorithm and proof for faithfulness, solving Salter's question for all p.
result The Burau representation of B3B_3 modulo pp is faithful for p13p \leq 13 and for all pp.

The Burau representation is a natural action of the braid group B_n on the free Z[t,t^{-1}]-module of rank n-1. It is a longstanding open problem to determine for which values of n this representation is faithful. It is known to be faithful for n=3. Moody has shown that it is not faithful for n>8 and Long and Paton imp…

1999-04-20abs ↗pdf ↗

We show the set of faithful representations of a closed orientable hyperbolic surface group is dense in both irreducible components of the PSL(2,K) representation variety, where K is the field of real or complex numbers, answering a question of W. Goldman. We also prove the existence of faithful representations into PU…

2004-11-11abs ↗pdf ↗

The Lawrence representation Ln,mL_{n,m} is a family of homological representation of the braid group BnB_n, which specializes to the reduced Burau and the Lawrence-Krammer representation when mm is 1 and 2. In this article we show that the Lawrence representation is faithful for m2m \geq 2.

2005-09-04abs ↗pdf ↗

The paper explores representations of graph manifolds to Seifert motion groups.

problem Existence of faithful representations of graph manifolds to Seifert motion groups.
method Discussion and proof of non-existence of certain representations.
result Graph manifolds can have virtually no faithful representations to the Seifert motion group.

We prove that a free group F_2 admits a faithful discrete representation into Diff_{+}(I). We also prove that F_2 admits a faithful discrete representation into Homeo_{+}(I). Some properties of these representations have been studied. In the last section we raise several questions.

2010-04-12abs ↗pdf ↗

Based on a normal form for braid group elements suggested by Dehornoy, we prove several representations of braid groups by automorphisms of a free group to be faithful. This includes a simple proof of the standard Artin's representation being faithful.

2002-03-17abs ↗pdf ↗

Link between braid groups and q-deformed rationals solves a classification problem.

problem Classifying faithful complex specializations of the Burau representation of braid group B3.
method Established a link between Burau representation and q-deformed rational numbers.
result Proved faithfulness of Burau representation outside a specific annulus.

In this paper we construct a faithful representation of the mapping class group of the genus two surface into a group of matrices over the complex numbers. Our starting point is the Lawrence-Krammer representation of the braid group B_n, which was shown to be faithful by Bigelow and Krammer. We obtain a faithful repres…

2000-10-31abs ↗pdf ↗

Improved lower bounds for faithful linear representations of mapping class groups.

problem Finding the minimum dimension of faithful linear representations of mapping class groups.
method Using finer study of commutation relations and specific pants decompositions to show representations must kill certain subgroups.
result Established lower bounds of 4g34g - 3 for faithful representations of mapping class groups of genus g7g \ge 7.

Counterexamples show Salter's question on Burau image is negative for n=4.

problem Conditions for a matrix to be in the Burau image of B4B_4.
method Analyzing the central quotient and using counterexamples.
result The central quotient of the Burau image group does not coincide with the central quotient of a specific subgroup of the unitary group for n=4n=4.

The Burau representation of braid group B4 is shown to be faithful almost everywhere.

problem Demonstrate that the Burau representation of braid group B4 is faithful.
method Developed a combinatorial theory to explicitly determine Burau matrices, using Garside normal form and new product decompositions of positive braids. Used cancellation results to show faithfulness almost everywhere.
result The Burau representation of braid group B4 is faithful almost everywhere.

For any topological groupoid G and any homomorphism from a locally compact Hausdorff topological group K to G, we construct an associated monodromy group. We prove that Morita equivalent topological groupoids have the same monodromy groups. We show how the monodromy groups can be used to test if a Lie groupoid lacks fa…

2017-01-27abs ↗pdf ↗

We consider the linear representations of the mapping class group of an n-punctured 2-sphere constructed by V. F. R. Jones using Iwahori-Hecke algebras of type A. We show that their faithfulness is equivalent to that of certain related Iwahori-Hecke algebra representation of Artin's braid group of n-1 strands. In the c…

2008-03-03abs ↗pdf ↗

The paper identifies a component of representations mapping modular group elements to isometries with unique fixed points.

problem Characterizing representations of the modular group into isometry groups.
method Analyzing the space of discrete faithful representations of the modular group into Isom(X) for X=SL3(R)/SO(3).
result The space of representations has a component homeomorphic to R^2 x [0,∞), parametrized by Pappus representations and containing Anosov representations.

\begin{abstract} The reduced Burau representation is a natural action of the braid group BnB_n on the first homology group H1(D~n;Z)H_1({\tilde{D}}_n;\mathbb{Z}) of a suitable infinite cyclic covering space D~n{\tilde{D}}_n of the nn--punctured disc DnD_n. It is known that the Burau representation is faithful for n3n\le 3 and…

2017-05-07abs ↗pdf ↗

The braid groups B_n can be defined as the mapping class group of the n-punctured disc. The Lawrence-Krammer representation of the braid group B_n is the induced action on a certain twisted second homology of the space of unordered pairs of points in the n-punctured disc. Recently, Daan Krammer showed that this is a fa…

2000-05-04abs ↗pdf ↗

In a previous work [11], the author considered a representation of the braid group ρ: B_n\to GL_m(\Bbb Z[q^{\pm 1},t^{\pm 1}]) (m=n(n-1)/2), and proved it to be faithful for n=4. Bigelow [3] then proved the same representation to be faithful for all n by a beautiful topological argument. The present paper gives a diffe…

2004-05-11abs ↗pdf ↗

In this paper we give a criterion for pairs of isometries of a nonpositively curved metric space to generate a free group. This criterion holds only in singular spaces, for example in Euclidean buildings. The original motivation for our criterion was to prove that the four dimensional Burau representation is faithful. …

2001-01-09abs ↗pdf ↗

In this paper, we introduce a study of prolongations of representations of Lie groups. We obtain a faithful (one-to-one) representation of TG where G is a finite-dimensional Lie group and TG is the tangent bundle of G, by using (not necessarily faithful) representations of G. We show that tangent functions of Lie group…

2013-10-08abs ↗pdf ↗

This study finds a special class of representations that dominate others in a complex hyperbolic group.

problem Domination of surface-group representations in complex hyperbolic groups.
method Analysis of TT-bent representations and their domination by discrete and faithful representations.
result A discrete and faithful representation exists that dominates a given TT-bent representation in the Bergman translation length spectrum.

Ideal attribution mechanisms track model interactions for faithful watermarks.

problem Ensuring models provide transparent and fair attribution decisions.
method Introducing ideal attribution mechanisms and a ledger for tracking model interactions.
result A unified framework for evaluating watermarking schemes, clarifying attainable guarantees.

In this paper we survey some work on representations of BnB_n given by the induced action on a homology module of some space. One of these, called the Lawrence-Krammer representation, recently came to prominence when it was shown to be faithful for all nn. We will outline the methods used, applying them to a closely r…

2003-04-15abs ↗pdf ↗

This paper aims to generalize Artin's ideas to establish an one-to-one correspondence between the orbit braid group Bnorb(C,Zp)B^{orb}_n(\mathbb{C},\mathbb{Z}_p) and a quotient of a group formed by some particular homeomorphisms of a punctured plane. First, we find a faithful representation of $B^{orb}_n(\mathbb{C},\mathbb{Z}_p…

2019-12-11abs ↗pdf ↗

COCA refactors training data to identify and erase unsafe concepts in LLMs.

problem Identifying and erasing unsafe concepts in Large Language Models (LLMs) for safety alignment.
method Concept Concentration (COCA) refactors training data with an explicit reasoning process to identify and erase unsafe concepts.
result COCA significantly reduces both in-distribution and out-of-distribution jailbreak success rates while maintaining strong performance on regular tasks.

Any nontrivial homomorphism from the mapping class group of an orientable surface of genus g3g\geq 3 to $\GL(2g,\C)$ is conjugate to the standard symplectic representation. It is also shown that the mapping class group has no faithful linear representation in dimensions less than or equal to 3g33g-3.

2011-08-16abs ↗pdf ↗