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An almost commutative algebra, or a $\rho$-commutative algebra, is an algebra which is graded by an abelian group and whose commutativity is controlled by a function called a commutation factor. The same way as a formulation of a…

Algebraic Topology · Mathematics 2022-06-14 Shuichi Harako

For Connes' spectral triples, the group of automorphisms lifted to the Hilbert space is defined and used to fluctuate the metric. A few commutative examples are presented including Chamseddine and Connes' spectral unification of gravity and…

High Energy Physics - Theory · Physics 2007-05-23 Thomas Schucker

We explicitly construct Fredholm modules and spectral triples representing any element of $K$-homology groups of Hensel-Steinitz algebras.

Operator Algebras · Mathematics 2025-10-09 Shelley Hebert , Slawomir Klimek , Matt McBride

For an almost contact metric manifold $N$, we find conditions for which either the total space of an $S^1$-bundle over $N$ or the Riemannian cone over $N$ admits a strong K\"ahler with torsion (SKT) structure. In this way we construct new…

Differential Geometry · Mathematics 2010-11-19 Marisa Fernandez , Anna Fino , Luis Ugarte , Raquel Villacampa

The notion of a spectral geometry on a compact metric space X is introduced. This notion serves as a discrete approximation of X motivated by the notion of a spectral triple from non-commutative geometry. A set of axioms charaterising…

Operator Algebras · Mathematics 2017-11-01 Sergei Buyalo

We construct commutative algebra spectra that represent the operator $K$-theory of $C^*$-algebras, which are algebras over the commutative ring spectra that represent topological $K$-theory. The spectral multiplicative structure introduces…

Operator Algebras · Mathematics 2022-03-08 R. Vasconcellos , L. C. P. A. M. Müssnich , N. J. B. Aza

We study two ways of summing an infinite family of noncommutative spectral triples. First, we propose a definition of the integration of spectral triples and give an example using algebras of Toeplitz operators acting on weighted Bergman…

Mathematical Physics · Physics 2016-11-18 Kevin Falk

We introduce the class of almost symmetric submanifolds of Euclidean space, a close relative of symmetric submanifolds and (contact) sub-Riemannian symmetric spaces. More specifically, we prove that every full irreducible almost symmetric…

Differential Geometry · Mathematics 2025-12-18 Claudio Gorodski , Carlos Olmos

A notion of fundamental group of spectral triples has been introduced. The notion uses a noncommutative analogue of unramified coverings. It was shown that in commutative case this fundamental group is a profinite completion of fundamental…

K-Theory and Homology · Mathematics 2007-05-23 Petr R. Ivankov , Nickolay P. Ivankov

A regular spectral triple is proposed for a two-dimensional $\kappa$-deformation. It is based on the naturally associated affine group $G$, a smooth subalgebra of $C^*(G)$, and an operator $\caD$ defined by two derivations on this…

Mathematical Physics · Physics 2012-08-07 B. Iochum , T. Masson , A. Sitarz

We show that the K-theory spectra of many assemblers, such as the assembler of polytopes in euclidean, hyperbolic or spherical geometry, as well as the assembler of definable sets, are equivalent to the K-theory spectrum of a squares…

K-Theory and Homology · Mathematics 2025-12-02 Josefien Kuijper

We introduce the notion of a polygonic spectrum which is designed to axiomatize the structure on topological Hochschild homology $\mathrm{THH}(R,M)$ of an $\mathbb{E}_1$-ring $R$ with coefficients in an $R$-bimodule $M$. For every polygonic…

Algebraic Topology · Mathematics 2023-02-16 Achim Krause , Jonas McCandless , Thomas Nikolaus

On a 4-dimensional compact symplectic manifold, we consider a smooth family of compatible almost-complex structures such that at time zero the induced metric is Hermite-Einstein almost-K\"ahler metric with zero or negative Hermitian scalar…

Differential Geometry · Mathematics 2013-10-01 Mehdi Lejmi

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

We extend the notion of an almost flat bundle over a closed Riemannian manifold to bundles over simplicial complexes, and prove that up to a constant factor, this notion is invariant under pullback via maps which induce isomorphisms on…

Geometric Topology · Mathematics 2018-03-15 Benedikt Hunger

We extend the notion of a spectral triple to that of a higher-order relative spectral triple, which accommodates several types of hypoelliptic differential operators on manifolds with boundary. The bounded transform of a higher-order…

K-Theory and Homology · Mathematics 2024-06-05 Magnus Fries

We study $\mathcal D$-homothetic deformations of almost $\alpha$-Kenmotsu structures. We characterize almost contact metric manifolds which are $CR$-integrable almost $\alpha$-Kenmotsu manifolds, through the existence of a canonical linear…

Differential Geometry · Mathematics 2010-06-25 Giulia Dileo

We complete and precise the results of [B.13] and we prove a strong version of the semi-proper direct image theorem with values in the space C f n (M) of finite type closed n--cycles in a complex space M. We describe the strongly…

Complex Variables · Mathematics 2015-04-08 Daniel Barlet

For a closed smooth manifold $M$ admitting a symplectic structure, we define a smooth topological invariant $Z(M)$ using almost-K\"ahler metrics, i.e. Riemannian metrics compatible with symplectic structures. We also introduce $Z(M,…

Differential Geometry · Mathematics 2014-09-19 Jongsu Kim , Chanyoung Sung

Lie groups considered as three-dimensional almost paracontact almost paracomplex Riemannian manifolds are investigated. In each basic class of the classification used for the manifolds under consideration, a correspondence is established…

Differential Geometry · Mathematics 2021-06-22 Mancho Manev , Veselina Tavkova