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

7 votes

How to triangulate a math reference?

MathOverflow itself serves as an excellent reference tool for this sort of triangulation. When a future researcher googles the topic of lextensive categories with strongly orthogonal orbits (perhaps w …
Tom LaGatta's user avatar
  • 8,532
0 votes

infinite dimensional polyhedra

For a very good reference see Eckland and Turnbull, Infinite-Dimensional Optimization and Convexity.
Tom LaGatta's user avatar
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0 votes
1 answer
232 views

Kernel elements for the Grothendieck group map of a commutative monoid

This is just a nomenclature question. Let $T$ be a commutative monoid, and let $T^*$ be its Grothendieck group. That is, $T^* \cong T \times T \ / \sim$, where $(s,s') \sim (t, t')$ if $s+t'+e = s'+t+ …
Tom LaGatta's user avatar
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4 votes
Accepted

Notion of smoothness for set-valued functions

My idea is that if we want to compare $f(p)$ and $f(q)$ for nearby points $p$ and $q$, then we need to be able to put $f(p)$ and $f(q)$ into the same space. To do this, I'm going to assume that $M$ i …
Tom LaGatta's user avatar
  • 8,532
0 votes
3 answers
499 views

The symmetry group of $\mathbb Z^d$

Let $d \ge 1$, and consider the integer lattice $\mathbb Z^d$. This is a homogeneous space, in the manner of the Erlangan Programm. I would like to write $\mathbb Z^d = G / H$, where $G$ is the symm …
Tom LaGatta's user avatar
  • 8,532
3 votes
1 answer
152 views

Defining a family of rotations with certain properties

Let $d \ge 2$, and consider the sphere $S^{d-1}$ embedded in $\mathbb R^d$. Does there exist a family of rotations $\{\mathcal O_v\}_{v \in S^{d-1}}$ which satisfies: $\mathcal O_v e_1 = v$, and $\ …
Tom LaGatta's user avatar
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4 votes
3 answers
3k views

Examples of Banach spaces and their duals

There are many representation theorems which state that the dual space of a Banach space $X$ has a particularly concrete form. For example, if $X = C([0,1],\mathbb R)$ is the space of real-valued con …
Tom LaGatta's user avatar
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6 votes
1 answer
448 views

The typical size of a random element in a Banach space

Let $X$ be a separable Banach space, and let $\mathbb P$ be a Radon probability measure on $X$ with zero mean and covariance operator $K : X^* \to X$. Let $x$ be an $X$-valued random variable with di …
Tom LaGatta's user avatar
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4 votes
1 answer
310 views

Spectral Properties of $A(I-A)^{-1}$

I am working with a class of matrices $A$ which are non-negative-definite, not symmetric, and have maximum eigenvalue less than 1. I am interested in the spectral properties of the matrix $H = A(I - …
Tom LaGatta's user avatar
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2 votes
1 answer
885 views

Riesz representation theorem for vector-valued fields

Let $Q$ be a locally compact Hausdorff space, and let $V$ be a topological vector space. Consider the space $X = C_0(Q, V)$ of $V$-valued fields which vanish at infinity. Let $X^*$ denote the dual spa …
Tom LaGatta's user avatar
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13 votes
2 answers
1k views

Applications of non-separable Hilbert spaces

In applications, Hilbert spaces of interest are often assumed to be separable. In addition to being extremely convenient mathematically, this assumption can often be justified on computational or phys …
3 votes
1 answer
2k views

A formula for the Jacobian of a flow

Let $U : \mathbb R^d \to \mathbb R^d$ be a smooth vector field, and let $F_t : \mathbb R \times \mathbb R^d \to \mathbb R^d$ be the corresponding smooth flow, defined by the differential equation $$\t …
Tom LaGatta's user avatar
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3 votes
3 answers
2k views

How do we use an Ehresmann connection to define a semispray?

Let $M$ be a differentiable manifold, let $TM$ be its tangent bundle, and consider $TTM$, the double tangent bundle. Let $V \subseteq TTM$ denote the vertical subbundle, which is determined in a cano …
Tom LaGatta's user avatar
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12 votes
2 answers
3k views

Does there exist an event independent of a given sigma-algebra?

The following question came up in a discussion with my advisor: Let $(\Omega, \mathcal F, \mathbb P)$ be a non-trivial probability space, and suppose that $\mathcal G$ is a proper sub-$\sigma$-alg …
Tom LaGatta's user avatar
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29 votes
Accepted

Mathematical Advice for Interested Highschool Students

This is an answer to your question, What general resources exist for students in highschool who are very interested in Mathematics? A patient teacher is the best resource for an interested high …

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