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We study $\epsilon$-representations of discrete groups by unitary operators on a Hilbert space. We define the notion of Ulam stability of a group which loosely means that finite-dimensional $\epsilon$-represendations are uniformly close to…

Functional Analysis · Mathematics 2010-10-05 Marc Burger , Narutaka Ozawa , Andreas Thom

In our earlier work, we constructed a specific non-compact quantum group whose quantum group structures have been constructed on a certain twisted group C*-algebra. In a sense, it may be considered as a ``quantum Heisenberg group…

Operator Algebras · Mathematics 2009-09-25 Byung-Jay Kahng

In this paper, we introduce and study the class of {\it enriched strictly pseudocontractive mappings} in Hilbert spaces and extend the corresponding convergence theorem (Theorem 12) in [Browder, F. E., Petryshyn, W. V., {\it Construction of…

Functional Analysis · Mathematics 2019-09-10 Vasile Berinde

Motivated by the relation between Schur algebra and the group algebra of a symmetric group, along with other similar examples in algebraic Lie theory, Min Fang and Steffen Koenig addressed some behaviour of the endomorphism algebra of a…

Representation Theory · Mathematics 2021-01-01 Takuma Aihara , Aaron Chan , Takahiro Honma

Let H(X) be the generalized Heisenberg group induced by a normed space X. We prove that X is a relatively minimal subgroup of H(X). We show that the group $G:=H(L_4[0,1])$ is reflexively representable but weakly continuous unitary…

Functional Analysis · Mathematics 2007-05-23 Michael Megrelishvili

A physically more adequate definition of a quaternionic holomorphic (H-holomorphic) function of one quaternionic variable compared to known ones and a quaternionic generalization of Cauchy-Riemann's equations are presented. At that a class…

Complex Variables · Mathematics 2024-02-14 Michael Parfenov

Let $G$ and $T$ be topological groups, $\alpha : T \to \Aut(G)$ a homomorphism defining a continuous action of $T$ on $G$ and $G^\sharp := G \rtimes_\alpha T$ the corresponding semidirect product group. In this paper we address several…

Representation Theory · Mathematics 2012-08-14 Karl-Hermann Neeb

For an arbitrary unimodular Lie group $G$, we construct strongly continuous unitary representations in the Bergman space of a naturally constructed strongly pseudoconvex neighborhood of $G$ in the complexification of its underlying…

Representation Theory · Mathematics 2010-09-14 Giuseppe Della Sala , Joe J. Perez

We describe a special class of representations of an inverse semigroup S on Hilbert's space which we term "tight". These representations are supported on a subset of the spectrum of the idempotent semilattice of S, called the "tight…

Operator Algebras · Mathematics 2008-06-25 Ruy Exel

Given a positive integer $n$ and a partition $(n_1,\ldots,n_r)$ of $n$, one can consider the associated $n$-dimensional multiprojective space $\mathbb{P}^{n_1}\times \cdots \times \mathbb{P}^{n_r}$. These multiprojective spaces are…

Algebraic Geometry · Mathematics 2025-07-15 Arijit Mukherjee

It is shown that the quaternionic Hilbert space formulation of quantum mechanics allows a quantization, based on a generalized system of imprimitivity, that leads to a description of the motion of a quantum particle in the field of a…

Quantum Physics · Physics 2022-04-05 G. G. Emch , A Jadczyk

By following the ideas underpinning the well-established ``homogeneous model'' of an $n$-dimensional Euclidean space, we investigate whether the motion group or the weak motion group of an $n$-dimensional affine metric space on a vector…

Metric Geometry · Mathematics 2023-12-08 Hans Havlicek

This is the first of a sequence of papers devoted to studying the link between the complexity of the Word Problem for a finitely generated recursively presented group $G$ and the isoperimetric functions of the finitely presented groups in…

Group Theory · Mathematics 2025-09-23 Francis Wagner

This work provides a quaternioinc reprsentation for real symplectic matrices in dimension four, analogous to the pair of unit quaternions representation for special orthogonal matrices. In the process of finding formulae for this…

Mathematical Physics · Physics 2008-01-30 Yassmin Ansari , Viswanath Ramakrishna

Each vector space that is endowed with a quadratic form determines its Clifford algebra. This algebra, in turn, contains a distinguished group, known as the Lipschitz group. We show that only a quotient of this group remains meaningful in…

Metric Geometry · Mathematics 2024-02-02 Hans Havlicek

The notion of a \emph{$G$-completely reducible} subgroup is important in the study of algebraic groups and their subgroup structure. It generalizes the usual idea of complete reducibility from representation theory: a subgroup $H$ of a…

Group Theory · Mathematics 2022-07-26 Benjamin Martin

We study equivariant projective compactifications of reductive groups obtained by closing the image of a group in the space of operators of a projective representation. We describe the structure and the mutual position of their orbits under…

Algebraic Geometry · Mathematics 2015-06-26 Dmitri A. Timashev

For weighted group convoltion measure algebra we construct a representation on reflexsive space.

Functional Analysis · Mathematics 2016-02-19 Bahram Khodsiani , Ali Rejali

We review the general properties of target spaces of hypermultiplets, which are quaternionic-like manifolds, and discuss the relations between these manifolds and their symmetry generators. We explicitly construct a one-to-one map between…

High Energy Physics - Theory · Physics 2009-11-10 Eric Bergshoeff , Sorin Cucu , Tim de Wit , Jos Gheerardyn , Stefan Vandoren , Antoine Van Proeyen

We consider the projective linear group $\mathrm{PSL}(3,\mathbb{H})$. We have investigated the reversibility problem in this group and use the reversibility to offer an algebraic characterization of the dynamical types of…

Group Theory · Mathematics 2023-07-20 Sandipan Dutta , Krishnendu Gongopadhyay , Tejbir Lohan