The injective spectrum of a noncommutative space

Non-surjective pullbacks of graph C*-algebras from non-injective pushouts of graphs

We find a substantial class of pairs of $*$-homomorphisms between graph C*-algebras of the form $C^*(E)\hookrightarrow C^*(G)\twoheadleftarrow C^*(F)$ whose pullback C*-algebra is an AF graph C*-algebra. Our result can be interpreted as a recipe for determining the quantum space obtained by shrinking a quantum subspace. There is a variety of examples from noncommutative topology, such as quantum complex projective spaces (including the standard Podleś quantum sphere) or quantum teardrops, that instantiate the result. Furthermore, to go beyond AF graph C*-algebras, we consider extensions of gra…

Direction-Dependent CMB Power Spectrum and Statistical Anisotropy from Noncommutative Geometry

Modern cosmology has now emerged as a testing ground for theories beyond the standard model of particle physics. In this paper, we consider quantum fluctuations of the inflaton scalar field on certain noncommutative spacetimes and look for noncommutative corrections in the cosmic microwave background (CMB) radiation. Inhomogeneities in the distribution of large scale structure and anisotropies in the CMB radiation can carry traces of noncommutativity of the early universe. We show that its power spectrum becomes direction-dependent when spacetime is noncommutative. (The effects due to noncommu…

Spectrum of Schroedinger field in a noncommutative magnetic monopole

The energy spectrum of a nonrelativistic particle on a noncommutative sphere in the presence of a magnetic monopole field is calculated. The system is treated in the field theory language, in which the one-particle sector of a charged Schroedinger field coupled to a noncommutative U(1) gauge field is identified. It is shown that the Hamiltonian is essentially the angular momentum squared of the particle, but with a nontrivial scaling factor appearing, in agreement with the first-quantized canonical treatment of the problem. Monopole quantization is recovered and identified as the quantization …

非交换Gelfand对偶：代数情形

Noncommutative Gelfand Duality: the algebraic case

该研究借助导出代数几何技术定义了非交换Gelfand对偶，证明环范畴与预环化位点子范畴反等价，提出的新谱的相对精细化版本在复有限生成交换代数情形与Grothendieck谱一致，为量子时空几何研究奠基。

有限对偶余代数作为极大谱的量子化

The finite dual coalgebra as a quantization of the maximal spectrum

本文将 Heyneman–Sweedler 有限对偶余代数解释为非交换极大谱的量子化，定义完全剩余有限维代数，并刻画中心模有限素仿射代数的 Azumaya 轨迹及单位根量子平面。

Solvmanifolds and noncommutative tori with real multiplication

We prove that the Shimizu L-function of a real quadratic field is obtained from a (Lorentzian) spectral triple on a noncommutative torus with real multiplication, as an adiabatic limit of the Dirac operator on a 3-dimensional solvmanifold. The Dirac operator on this 3-dimensional geometry gives, via the Connes-Landi isospectral deformations, a spectral triple for the noncommutative tori obtained by deforming the fiber tori to noncommutative spaces. The 3-dimensional solvmanifold is the homotopy quotient in the sense of Baum--Connes of the noncommutative space obtained as the crossed product of…