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In this paper we develop the definition of a global orthogonal spectrum and its unitary version. It relates $G-$equivariant spectra by equivariant weak equivalence in a coherent way. This category of global spectra has a model structure…

Algebraic Topology · Mathematics 2018-12-04 Zhen Huan

The category of rational G-equivariant cohomology theories for a compact Lie group $G$ is the homotopy category of rational G-spectra and therefore tensor-triangulated. We show that its Balmer spectrum is the set of conjugacy classes of…

Algebraic Topology · Mathematics 2017-06-27 J. P. C. Greenlees

Let $q=|q|e^{i\pi\theta},\,\theta\in(-1,1],$ be a nonzero complex number such that $|q|\neq 1$ and consider the compact quantum group $U_q(2)$. For $\theta\notin\mathbb{Q}\setminus\{0,1\}$, we obtain the $K$-theory of the $C^*$-algebra…

Operator Algebras · Mathematics 2026-01-19 Satyajit Guin , Bipul Saurabh

The spectrum of $L^2$ on a pseudo-unitary group $U(p,q)$ (we assume $p\ge q$ naturally splits into $q+1$ types. We write explicitly orthogonal projectors in $L^2$ to subspaces with uniform spectra (this is an old question formulated by…

Representation Theory · Mathematics 2018-12-14 Yury A. Neretin

In the setting of C*-categories, we provide a definition of "spectrum" of a commutative full C*-category as a one-dimensional unital saturated Fell bundle over a suitable groupoid (equivalence relation) and prove a categorical Gelfand…

Operator Algebras · Mathematics 2011-12-30 Paolo Bertozzini , Roberto Conti , Wicharn Lewkeeratiyutkul

Let $G$ be a finite group. There is a standard theorem on the classification of $G$-equivariant finite dimensional simple commutative, associative, and Lie algebras (i.e., simple algebras of these types in the category of representations of…

Rings and Algebras · Mathematics 2015-12-25 Pavel Etingof

The spaces of higher-order differential operators (in Dimension 1|2), which are modules over the stringy Lie superalgebra K(2), are isomorphic to the corresponding spaces of symbols as orthosymplectic modules in non resonant cases. Such an…

Mathematical Physics · Physics 2011-06-29 Najla Mellouli

A bounded set $\Omega \subset \mathbb{R}^d$ is called a spectral set if the space $L^2(\Omega)$ admits a complete orthogonal system of exponential functions. We prove that a cylindric set $\Omega$ is spectral if and only if its base is a…

Classical Analysis and ODEs · Mathematics 2016-09-26 Rachel Greenfeld , Nir Lev

This paper brings together C*-algebras and algebraic topology in terms of viewing a C*-algebraic invariant in terms of a topological spectrum. E-theory, E(A,B), is a bivariant functor in the sense that is a cohomology functor in the first…

Operator Algebras · Mathematics 2017-08-11 Sarah L. Browne

We show that the category of symmetric spectra can be used as a model for global equivariant homotopy theory of finite groups.

Algebraic Topology · Mathematics 2019-05-29 Markus Hausmann

We show that 2D periodic operators with local and perpendicular defects form an algebra. We provide an algorithm of finding spectrum for such operators. While the continuous spectral components can be computed by simple algebraic operations…

Spectral Theory · Mathematics 2016-06-07 Anton A. Kutsenko

For G a compact Lie group, toral G-spectra are those rational G-spectra whose geometric isotropy consists of subgroups of a maximal torus of G. The homotopy category of rational toral G-spectra is a retract of the category of all rational…

Algebraic Topology · Mathematics 2019-12-25 David Barnes , J. P. C. Greenlees , Magdalena Kedziorek

Categorical spectra are spectrum objects in pointed $(\infty,\infty)$-categories: sequences $(X_n)$ equipped with equivalences $X_n\simeq \Omega X_{n+1}$. This thesis develops foundations for categorical spectra and constructs their tensor…

Algebraic Topology · Mathematics 2026-05-06 Naruki Masuda

In the present paper we continue the project of systematic construction of invariant differential operators on the example of the non-compact algebra $G_{2(2)}$ which is split real form of $G_2$. We give the classification of reducible…

Representation Theory · Mathematics 2019-05-22 V. K. Dobrev

The spectrum of a finite group is the set of its elements orders. Groups are said to be isospectral if their spectra coincide. For every finite simple exceptional group $L=E_7(q)$, we prove that each finite group isospectral to $L$ is…

Group Theory · Mathematics 2021-01-01 Andrey V. Vasil'ev , Alexey M. Staroletov

Symmetry is present in many tasks in computer vision, where the same class of objects can appear transformed, e.g. rotated due to different camera orientations, or scaled due to perspective. The knowledge of such symmetries in data coupled…

Image and Video Processing · Electrical Eng. & Systems 2022-07-25 Mateus Sangalli , Samy Blusseau , Santiago Velasco-Forero , Jesús Angulo

We prove that if G is the circle group or a profinite group, then the all of the homotopical information of the category of rational G-spectra is captured by triangulated structure of the rational G-equivariant stable homotopy category.…

Algebraic Topology · Mathematics 2012-01-27 David Barnes , Constanze Roitzheim

For a point $\mathfrak{p}$ in the spectrum of the cohomology ring of a finite group $G$ over a field $k$, we calculate the spectrum for the subcategory of dualisable objects inside the tensor triangulated category of $\mathfrak{p}$-local…

Representation Theory · Mathematics 2025-05-27 Dave Benson , Srikanth B. Iyengar , Henning Krause , Julia Pevtsova

In this paper we describe the Jordan-Holder series of the standard modules over the rational Cherednik algebras associated with the dihedral group. In particular, we compute the characters of the irreducible representations from the…

Representation Theory · Mathematics 2007-05-23 Tatyana Chmutova

We classify the bireflections (products of 2 involutions) in the commutator subgroup G an orthogonal group O(V) over a finite field GF(q) of characteristic not 2. We show that every element of G is a bireflection if it is reversible…

Group Theory · Mathematics 2024-12-13 Klaus Nielsen