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Q&A for professional mathematicians
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Let $A$ be a $C^*$-algebra and $(a_{ij}) \in M_n(A)$ be a positive matrix. Does there exist a constant $C \ge 0$ (not depending on the $a_{ij}$) such that $$\lVert(a_{ij})\rVert \le C \Bigl\lVert\s...
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When does two Brauer group disagree
Usually, we have $Br_{Az}(X)\subseteq Br_{Gr}(X)_{tor}\subseteq Br_{Gr}(X):= H^2(X,\mathbb G_m)$.
It is easy to find counter examples for the second inclusion, but just taking something very singular. The hard part is the first one.
By Shröer, we know that there are several families, like abelian varieties, curves, with $Br_{Az}(X)= Br_{Gr}(X)_{tor}$. By Eddin et al., we know there are counter-examples of nonseparable surfaces. My question is do we know some counter-examples of... -
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Weakening of Idoneal condition
This is about: https://math.stackexchange.com/questions/5108455/what-is-the-largest-integer-d-such-there-is-a-congruence-relation-on-primes-p
The idoneal numbers are discriminants for which every (positive) binary quadratic form squares to the identity in the (form) class group.... -
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Can a compact 7-manifold satisfying the $\chi$-Hodge condition admit a non-trivi...
Dear esteemed colleagues,
Our work on classifying compact, orientable 7-manifolds has led us to a novel class of manifold, which we denote $M_{JL}$ (the June-Lace Manifold). This manifold is theoretically constructed via a specific quantum-derived product of two complex projective... -
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Are the orbits of an action by a simply connected Lie group on an orientable manifold necessarily orientable?
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