In this paper, we study two questions related to the problem of testing whether a function is close to a homomorphism. For two finite groups (not necessarily Abelian), an arbitrary map , and a parameter , say that is -close to a homomorphism if there is some homomorphism such that and differ on at most elements of , and say that is -far otherwise. For a given and , a homomorphism tester should ...

For graphs G and H , a homomorphism from G to H is a function φ : V (G) → V (H), which maps vertices adjacent in G to adjacent vertices of H . A homomorphism is locally injective if no two vertices with a common neighbor are mapped to a single vertex in H . Many cases of graph homomorphism and locally injective graph homomorphism are NPcomplete, so there is little hope to design polynomial-time...

Chmieliński has proved in the paper [4] the superstability of the generalized orthogonality equation |〈 f (x), f (y)〉| = |〈x,y〉|. In this paper, we will extend the result of Chmieliński by proving a theorem: Let Dn be a suitable subset of Rn. If a function f : Dn → Rn satisfies the inequality ||〈 f (x), f (y)〉|− |〈x,y〉|| ≤ φ(x,y) for an appropriate control function φ(x,y) and for all x,y ∈ Dn, ...

Let Bn be the Artin braid group on n strings with standard generators σ1, . . . , σn−1 , and let SBn be the singular braid monoid with generators σ ±1 1 , . . . , σ ±1 n−1, τ1, . . . , τn−1 . The desingularization map is the multiplicative homomorphism η : SBn → Z[Bn] defined by η(σ ±1 i ) = σ ±1 i and η(τi) = σi − σ −1 i , for 1 ≤ i ≤ n − 1. The purpose of the present paper is to prove Birman’...

The following note is a supplement to [1]. We will maintain the notation of [1] throughout, and all numbered items to which we refer are from that paper. Theorem 6.11 states that if M is a finitely generated R-module then Th(M,F) is stable. As pointed out in Remark 6.12, the proof Theorem 6.11 yields a stronger conclusion: Th(M,F) is superstable. These notes consist of detailed arguments for th...

Interpersonal Comparisons of Utility: An Algebraic Characterization of Projective Preorders and Some Welfare Consequences It is shown that any completely preordered topological real algebra admits a continuous utility representation which is an algebra-homomorphism (i.e., it is linear and multiplicative). As an application of this result, we provide an algebraic characterization of the projecti...

In this paper we compute the second homology of the discrete jet groups. Let R be the additive group of real numbers and R the multiplicative group of positive reals. The n jet group Jn = {rx+a2x + · · ·+anx | r ∈ R, ai ∈ R} is the group, under composition followed by truncation, of invertible, orientationpreserving real n-jets at 0. Consider the homomorphism D : Jn → R obtained by projecting o...

Let L=K1 U .. , U Kp.r;;;S3 be a tame link of Jl~ 1 components with group G=7r1(S3_L). Also, let H=G/G' be the abelianization of G; H is then the (multiplicative) free abelian group generated by the meridians t1, ••• , tp. of L, and its integral group ring ZH consists of polynomials (with integer coefficients) in t 1 ,. .. , tp.' til, ... , t;l. The homomorphism 6: ZH~Z (which has 6(t;)=1 for e...

Partee (1986) claimed without proof that the function BE is the only homomorphism that makes the Partee triangle commute. This paper shows that this claim is incorrect unless “homomorphism” is understood as “complete homomorphism.” It also shows that BE and A are the inverses of each other on certain natural assumptions.