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We derive the universal real time $U(1)$ topological gauge field action for mixed quantum states of weakly correlated fermions in all dimensions, and demonstrate its independence of the underlying equilibrium or non-equilibrium nature of…

Statistical Mechanics · Physics 2022-12-28 Ze-Min Huang , Xiao-Qi Sun , Sebastian Diehl

This survey concerns regular graphs that are extremal with respect to the number of independent sets, and more generally, graph homomorphisms. More precisely, in the family of of $d$-regular graphs, which graph $G$ maximizes/minimizes the…

Combinatorics · Mathematics 2017-11-03 Yufei Zhao

Let $A$ be a separable, unital and exact $C^*$-algebra satisfying the universal coefficient theorem. We prove uniqueness theorems up to unitary conjugacy for unital, full and nuclear maps from $A$ into ultraproducts of finite von Neumann…

Operator Algebras · Mathematics 2026-05-15 Shanshan Hua , Stuart White

Given a conditional expectation $P$ from a C*-algebra $B$ onto a C*-subalgebra $A$, we observe that induction of ideals via $P$, together with a map which we call co-induction, forms a Galois connection between the lattices of ideals of $A$…

Operator Algebras · Mathematics 2025-11-04 Kevin Aguyar Brix , Chris Bruce , Kang Li , Eduardo Scarparo

We classify the gauge-invariant ideals in the C*-algebras of infinite directed graphs, and describe the quotients as graph algebras. We then use these results to identify the gauge-invariant primitive ideals in terms of the structural…

Operator Algebras · Mathematics 2007-05-23 Teresa Bates , Jeong Hee Hong , Iain Raeburn , Wojciech Szymanski

We study integrability for coactions of locally compact groups. For abelian groups, this corresponds to integrability of the associated action of the Pontrjagin dual group. The theory of integrable group actions has been previously studied…

Operator Algebras · Mathematics 2009-08-06 Alcides Buss

We consider a twisted action of a discrete group G on a unital C*-algebra A and give conditions ensuring that there is a bijective correspondence between the maximal invariant ideals of A and the maximal ideals in the associated reduced…

Operator Algebras · Mathematics 2023-07-19 Erik Bédos , Roberto Conti

Given a C*-algebra B which is graded over a discrete group G we consider ideals of B which are invariant under the projections onto each of the grading subspaces. If G is exact and the standard conditional expectation of B is faithful we…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel

The main purpose of this paper is to prove the uniqueness of a graph attaining the maximum of the number of independent sets over all $k$-regular graphs on $n$ vertices for $2k|n$.

Combinatorics · Mathematics 2016-03-01 Alexei Dmitriev , Alex Dainiak

We develop the theory of quantum (a.k.a. noncommutative) relations and quantum (a.k.a. noncommutative) graphs in the finite-dimensional covariant setting, where all systems (finite-dimensional $C^*$-algebras) carry an action of a compact…

Operator Algebras · Mathematics 2026-03-19 Dominic Verdon

As a generalization of the Exel-Pardo's notion of self-similar graph, we introduce self-similar group actions on ultragraphs and their $C^*$-algebras. We then approach to the $C^*$-algebras by inverse semigroup and tight groupoid models.

Operator Algebras · Mathematics 2025-05-20 Hossein Larki , Najmeh Rajabzadeh-Hasiri

To every Fell bundle $\mathscr C$ over a locally compact group ${\sf G}$ one associates a Banach $^*$-algebra $L^1({\sf G}\,\vert\,\mathscr C)$. We prove that it is symmetric whenever ${\sf G}$ with the discrete topology is rigidly…

Operator Algebras · Mathematics 2024-04-04 Felipe Flores , Diego Jauré , Marius Mantoiu

We formalize eight different notions of isomorphism among (unital) graph C*-algebras, and initiate the study of which of these notions may be described geometrically as generated by moves. We propose a list of seven types of moves that we…

Operator Algebras · Mathematics 2025-08-22 Søren Eilers , Efren Ruiz

In this work the equivariant signature of a manifold with proper action of a discrete group is defined as an invariant of equivariant bordisms. It is shown that the computation of this signature can be reduced to its computation on fixed…

Algebraic Topology · Mathematics 2011-12-12 A. S. Mishchenko , Quitzeh Morales Meléndez

The unions of directed graphs are the simplest examples of pushouts of directed graphs. The conditions under which they contravariantly induce surjective gauge-equivariant pullbacks of graph C*-algebras have been well studied and vastly…

Rings and Algebras · Mathematics 2025-07-18 Piotr M. Hajac , Mariusz Tobolski

Gauge invariance in discrete dynamical systems and its connection with quantization are considered. For a complete description of gauge symmetries of a system we construct explicitly a class of groups unifying in a natural way the space and…

Mathematical Physics · Physics 2015-05-13 Vladimir V. Kornyak

We introduce a graph theoretic property called Condition (N) for finitely separated graphs and prove that it is equivalent to both nuclearity and exactness of the associated universal tame graph C*-algebra.

Operator Algebras · Mathematics 2017-05-15 Matias Lolk

We discuss a link between graph theory and geometry that arises when considering graph dynamical systems with odd interactions. The equilibrium set in such systems is not a collection of isolated points, but rather a union of manifolds,…

Dynamical Systems · Mathematics 2024-08-28 Davide Sclosa

We consider induced coactions on C*-algebras along a homomorphism of locally compact quantum groups which need not give a closed quantum subgroup. Our approach generalizes the induced coactions constructed by Vaes, and also includes certain…

Operator Algebras · Mathematics 2022-03-02 Kan Kitamura

We characterize covariant positive decomposable maps between unital C*-algebras in terms of a dilation theorem, which generalizes a seminal result by H. Scutaru from Rep. Math. Phys. 16 (1):79-87, 1979. As a case study, we provide a certain…

Operator Algebras · Mathematics 2025-12-08 Krzysztof Szczygielski