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This tag is used if a reference is needed in a paper or textbook on a specific result.

5 votes
1 answer
248 views

The square modulus of coordinates of a uniformly chosen point in complex projective space is...

I can't recall where I learned this (beautiful) fact, and I would like a reference (if possible, in a textbook): Let $(z_0:\cdots:z_n) \in \mathbb{P}^n(\mathbb{C})$ be chosen uniformly at random w …
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3 votes
1 answer
259 views

Subgroups of compact Lie groups generated by a subset of nodes of the Dynkin diagram

Where can I find a reference for the following fact, or as close as possible to it? Let $G$ be a semisimple compact real Lie group with rank $r$, let $T$ be a maximal torus in $G$, let $\mathfrak{ …
Gro-Tsen's user avatar
  • 32.4k
10 votes
0 answers
303 views

Compact Lie groups are rational homotopy equivalent to a product of spheres

According to [1] and [2], it is “well-known” that a compact Lie group $G$ has the same rational homology, and according to [2] is even rational homotopy equivalent, to the product $\mathbb{S}^{2m_1+1} …
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  • 32.4k
8 votes
1 answer
630 views

Flag manifolds (=R-spaces): quotients by parabolic subgroups vs. isotropy representation

Real flag manifolds (also known as R-spaces) can be defined in two ways which I believe are equivalent although some fine print may have escaped me: as a quotient of a semisimple real Lie group $G$ …
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  • 32.4k
11 votes
2 answers
707 views

Is there a modern account of Veblen functions of *several* variables?

Veblen $\phi$ functions extend the $\xi \mapsto \phi(\xi) := \omega^\xi$ and the $\xi \mapsto \phi(1,\xi) := \varepsilon_\xi$ functions on the ordinals by repeatedly taking fixed points (I won't repea …
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  • 32.4k
4 votes
2 answers
354 views

The bidualizing monad

Let $\mathbf{C}$ be a closed symmetric monoidal category (I probably need even less than this; the examples I have in mind are simply the category of modules over a commutative ring and the category o …
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  • 32.4k
16 votes
1 answer
476 views

Where can I learn more about the topology on $\mathbb{R}$ induced by the map $\mathbb{R} \to...

Consider the (continuous, injective, abelian group homomorphism) map $\Phi \colon \mathbb{R} \to \prod_{a>0} (\mathbb{R}/a\mathbb{Z})$ (where the target is given the product topology) taking $x\in \ma …
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6 votes
1 answer
475 views

Is the absolute of a compact space the projective limit of the Stone-Čech compactifications ...

Is the following statement true, and if it is, does someone have a reference? Let $X$ be a compact (i.e., compact and Hausdorff) topological space. Then the Gleason space (=Iliadis absolute, =Sto …
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24 votes
3 answers
2k views

Real Lie groups versus real linear algebraic groups: differences in connexity and fundamenta...

There are many introductory texts on real Lie groups, and many on linear algebraic groups in general, but fewer on the specific case of linear algebraic groups over the reals, and even fewer that try …
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2 votes
0 answers
139 views

Getting a copy of Stanley H. Stahl's dissertation on "Classes of primitive recursive ordinal...

Stanley Hershel Stahl did his PhD thesis at the University of Michigan, under the direction of Peter Hinman, and wrote a dissertation in 1974 with title "Classes of Primitive Recursive Ordinal Functio …
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13 votes
0 answers
358 views

What is known about differentiable and analytic structures on the long line (and half-line)?

When reading about this question which recently became active for some reason, I wanted to make a comment, as a warning regarding non-metrizable manifolds, to the effect that the every $C^\infty$ stru …
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15 votes
1 answer
575 views

Topological spaces in which countable intersections of dense open sets have dense interior

In certain topological spaces, known as Baire spaces (e.g., completely metrizable spaces), a countable intersection of dense open sets is dense. Now consider the following strengthening of the Baire p …
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18 votes
1 answer
811 views

Known configurations maximizing the volume of the convex hull of n points on the unit sphere

For $n\geq 4$, let $V_n$ be the maximum volume of the convex hull of $n$ points on the unit sphere (in $\mathbb{R}^3$, although information on higher dimensions is welcome as well). I'm sure the prob …
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  • 32.4k
10 votes
3 answers
574 views

Terminology for a set that does not surject onto $\omega$ (in ZF)

Short question: Is there a standard term for a set $F$ such that there does not exist a surjection $F \twoheadrightarrow \omega$ (in the context of ZF)? More detailed version: Consider the following f …
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  • 32.4k
6 votes
2 answers
2k views

Alternative or reprint of Carter's "Finite Groups of Lie Type: Conjugacy Classes and Complex...

I would like to learn about character theory of finite groups of Lie type and some Deligne-Lusztig theory. The classic textbook on the subject seems to be Roger W. Carter's Finite Groups of Lie Type: …
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