Errata Corrige to Theorems A and B for Dagger Quasi-Stein Spaces
We give a counter-example to Theorem B for dagger quasi-Stein spaces.
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arXiv subjects
Federico Bambozzi
Publications and source records attributed to Federico Bambozzi.
Noncommutative Gelfand Duality: the algebraic case
The goal of this paper is to define a notion of non-commutative Gelfand duality. Using techniques from derived algebraic geometry, we show that the category of rings is anti-equivalent to a subcategory of pre-ringed sites, inspired by Grothendieck's work on commutative rings. Our notion of spectrum, although formally reminiscent of the Grothendieck spectrum, is new. Remarkably, an appropriately refined relative version of our spectrum agrees with the Grothendieck spectrum for finitely generated commutative algebras over the complex numbers, among others. This work aims to represent the starting point for a rigorous study of geometric properties of quantum spacetimes.
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The tempered disk and the tempered cohomology
Let V be a complete discretely valued ring of mixed characteristic, with fraction field K and residue field k. Using the ind-Banach framework for derived analytic geometry, we view generic fibers of V-schemes as derived analytic spaces. This approach yields a refined notion of spectrum, richer than that of classical rigid geometry: for ex- ample we may have open subsets whose structure sheaf contains functions of logarithmic growth. In this setting, the transfer theorem for the log-growth of solutions of p-adic differ- ential equations becomes a natural continuity statement, analogous to the classical transfer theorem for radii of convergence on Berkovich spaces. Motivated by ideas of Scholze, we introduce tempered tubular neighborhoods of smooth k-schemes and define a new tempered de Rham cohomology via the derived de Rham complex of these tubes. Finally, we establish a comparison theorem showing that, for smooth proper k-schemes, tempered de Rham cohomology agrees with crystalline cohomology.
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Derived Analytic Geometry for Z-Valued Functions. Part I -- Topological Properties
We study the Banach algebras ${\rm C}(X, R)$ of continuous functions from a compact Hausdorff topological space $X$ to a Banach ring $R$ whose topology is discrete. We prove that the Berkovich spectrum of ${\rm C}(X, R)$ is homeomorphic to $\zeta(X) \times {\mathcal M}(R)$, where $\zeta(X)$ is the Banaschewski compactification of $X$ and ${\mathcal M}(R)$ is the Berkovich spectrum of $R$. We study how the topology of the spectrum of ${\rm C}(X, R)$ is related to the notion of homotopy Zariski open embedding used in derived geometry. We find that the topology of $\zeta(X)$ can be easily reconstructed from the homotopy Zariski topology associated to ${\rm C}(X, R)$. We also prove some results about the existence of Schauder bases on ${\rm C}(X, R)$ and a generalisation of the Stone--Weierstrass Theorem, under suitable hypotheses on $X$ and $R$.
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Homotopy Epimorphisms and Derived Tate's Acyclicity for Commutative C*-algebras
We study homotopy epimorphisms and covers formulated in terms of derived Tate's acyclicity for commutative C*-algebras and their non-Archimedean counterparts. We prove that a homotopy epimorphism between commutative C*-algebras precisely corresponds to a closed immersion between the compact Hausdorff topological spaces associated to them, and a cover of a commutative C*-algebra precisely corresponds to a topological cover of the compact Hausdorff topological space associated to it by closed immersions admitting a finite subcover. This permits us to prove derived and non-derived descent for Banach modules over commutative C*-algebras.
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On the Sheafyness Property of Spectra of Banach Rings
Let R be a non-Archimedean Banach ring, satisfying some mild technical hypothesis that we will specify later on. We prove that to R one can associate a homotopical Huber spectrum Spa^h(R) via the introduction of the notion of derived rational localizations. The spectrum so obtained is endowed with a derived structural sheaf O_{Spa^h(R)} of simplicial Banach algebras for which the derived Tate-Cech complex is strictly exact. Under some hypothesis we can prove that there is a canonical morphism of sites Spa(R) -> |Spa^h(R)| that is an equivalence in some well-known examples of non-sheafy Banach rings. This permits to use the tools of derived geometry to understand the geometry of Spa(R) also when H^0(O_{Spa(R)}) is not a sheaf.
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On the uniqueness of invariant states
Given an abelian group G endowed with a T-pre-symplectic form, we assign to it a symplectic twisted group *-algebra W_G and then we provide criteria for the uniqueness of states invariant under the ergodic action of the symplectic group of automorphism. As an application, we discuss the notion of natural states in quantum abelian Chern-Simons theory.
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Rigidity for rigid analytic motives
In this paper we prove the Rigidity Theorem for motives of rigid analytic varieties over a non-Archimedean valued field $K$. We prove this theorem both for motives with transfers and without transfers in a relative setting. Applications include the construction of \'etale realization functors, an upgrade of the known comparison between motives with and without transfers and an upgrade of the rigid analytic motivic tilting equivalence, extending them to $\mathrm{Z}[1/p]$-coefficients.
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Invariant states on noncommutative tori
For any number $h$ such that $\hbar:=h/2\pi$ is irrational and any skew-symmetric, non-degenerate bilinear form $\sigma:\mathbb{Z}^{2g}\times \mathbb{Z}^{2g} \to \mathbb{Z}$, let be $\mathcal{A}^h_{g,\sigma}$ be the twisted group $*$-algebra $\mathbb{C}[\mathbb{Z}^{2g}]$ and consider the ergodic group of $*$-automorphisms of $\mathcal{A}^h_{g,\sigma}$ induced by the action of the symplectic group Sp$(\mathbb{Z}^{2g},\sigma)$. We show that the only Sp$(\mathbb{Z}^{2g},\sigma)$-invariant state on $\mathcal{A}^h_{g,\sigma}$ is the trace state $\tau$.
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Analytic geometry over F_1 and the Fargues-Fontaine curve
This paper develops a theory of analytic geometry over the field with one element. The approach used is the analytic counter-part of the Toen-Vaquie theory of schemes over F_1, i.e. the base category relative to which we work out our theory is the category of sets endowed with norms (or families of norms). Base change functors to analytic spaces over Banach rings are studied and the basic spaces of analytic geometry (like polydisks) are recovered as a base change of analytic spaces over F_1. We end by discussing some applications of our theory to the theory of the Fargues-Fontaine curve and to the ring Witt vectors.
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On a generalization of affinoid varieties
In this thesis we develop the foundations for a theory of analytic geometry over a valued field, uniformly encompassing the case when the base field is equipped with a non-archimedean valuation and the case when it has an archimedean one. Our building blocks are dagger affinoid algebras, i.e. algebras of germs of analytic functions, equipped with their canonical bornology. We obtain results akin to the ones of affinoid algebras and affinoid spaces theory in our context. In particular, we give a generalization of the celebrated Gerritzen-Grauert theorem. Finally, we construct the category of dagger analytic spaces and compare its objects with classical objects from Berkovich geometry, dagger spaces of Grosse-Klonne and complex analytic spaces.
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Theorems A and B for dagger quasi-Stein spaces
In this article we use the homological methods of the theory of quasi-abelian categories and some results from functional analysis to prove Theorems A and B for (a broad sub-class of) dagger quasi-Stein spaces. In particular we show how to deduce these theorems from the vanishing, under certain hypothesis, of the higher derived functors of the projective limit functor. Our strategy of the proof generalizes and puts in a more formal framework the Kiehl's proof for rigid quasi-Stein spaces.
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Stein Domains in Banach Algebraic Geometry
In this article we give a homological characterization of the topology of Stein spaces over any valued base field. In particular, when working over the field of complex numbers, we obtain a characterization of the usual Euclidean (transcendental) topology of complex analytic spaces. For non-Archimedean base fields the topology we characterize coincides with the topology of the Berkovich analytic space associated to a non-Archimedean Stein algebra. Because the characterization we used is borrowed from a definition in derived geometry, this work should be read as a contribution towards the foundations of derived analytic geometry.
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Closed graph theorems for bornological spaces
The aim of this paper is that of discussing Closed Graph Theorems for bornological vector spaces in a way which is accessible to non-experts. We will see how to easily adapt classical arguments of functional analysis over $\mathbb{R}$ and $\mathbb{C}$ to deduce Closed Graph Theorems for bornological vector spaces over any complete, non-trivially valued field, hence encompassing the non-Archimedean case too. We will end this survey by discussing some applications. In particular, we will prove de Wilde's Theorem for non-Archimedean locally convex spaces and then deduce some results about the automatic boundedness of algebra morphisms for a class of bornological algebras of interest in analytic geometry, both Archimedean (complex analytic geometry) and non-Archimedean.
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Dagger Geometry As Banach Algebraic Geometry
In this article, we apply the approach of relative algebraic geometry towards analytic geometry to the category of bornological and Ind-Banach spaces (non-Archimedean or not). We are able to recast the theory of Grosse-Kl\"onne dagger affinoid domains with their weak G-topology in this new language. We prove an abstract recognition principle for the generators of their standard topology (the morphisms appearing in the covers). We end with a sketch of an emerging theory of dagger affinoid spaces over the integers, or any Banach ring, where we can see the Archimedean and non-Archimedean worlds coming together.
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On a Family of Circulant Matrices for Quasi-Cyclic Low-Density Generator Matrix Codes
We present a new class of sparse and easily invertible circulant matrices that can have a sparse inverse though not being permutation matrices. Their study is useful in the design of quasi-cyclic low-density generator matrix codes, that are able to join the inner structure of quasi-cyclic codes with sparse generator matrices, so limiting the number of elementary operations needed for encoding. Circulant matrices of the proposed class permit to hit both targets without resorting to identity or permutation matrices that may penalize the code minimum distance and often cause significant error floors.
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