Questions tagged [big-picture]
Questions to get the "big picture" about a subject.
181
questions
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52 views
What is the motivation for studying this subgroup of $SL_n(\Bbb R)?$
Consider a diagonal matrix $A$ with entries $e^{s_1},e^{s_2},\cdot\cdot\cdot$ on the diagonal s.t. $\sum_{i \ge1} s_i=0.$ From what I understand this is a subgroup of $SL_n(\Bbb R).$ This is because ...
1
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1answer
37 views
Hyperbolic curve and hyperbola?
Def: A hyperbolic curve is an algebraic curve obtained by removing $r$ points from a smooth,
proper curve of genus $g,$ where $g$ and $r$ are nonnegative integers such that $2g−2+r > 0.$
How ...
4
votes
0answers
125 views
Does anyone know what this diagram could be about?
Does anyone know what this diagram could be about? I found it about a year ago on some blog and I tried to relocate the source of the picture but was unable to.
My best guess is that maybe $R(x)$ and ...
2
votes
1answer
124 views
What is the big picture behind the quotient of a ring by its maximal ideal being a field?
A ring $(X, +, \times, 0, 1)$ is an algebraic structure such that $(X, +, 0)$ is a commutative group, $(X, \times, 1)$ is a monoid, and $\times$ distributes over $+$.
A sub-ring is a subset $Y \...
2
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3answers
49 views
Is a specific choice of ultrafilter necessary in order to get “concrete results” in nonstandard analysis?
Suppose we have sequences of real numbers which are indexed by the natural numbers. We can then define an ultrafilter $\mathcal{U} \subset 2^{\mathbb{N}}$ (where $2^{\mathbb{N}}$ is the powerset of ...
2
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1answer
28 views
On two conceptions of measurability
This is a very broad question about two conceptions of a measurable function. Let $(X, \mathcal X)$ be a measurable space, and let $f$ be a real-valued function of $X$. Throughout the post, I assume ...
2
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1answer
71 views
On the “duality” between formation of quotient structures and formation of substructures as stated in Joy of Cats
In the book Joy of Cats, the authors write (page 118),
One of the nice insights that can be gleaned from category theory is that the formation of quotient structures (such as groups of cosets and ...
2
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2answers
79 views
Intuition behind the definition of initial morphism and embedding as stated in Joy of Cats
In Definition 8.6 of Joy of Cats the authors write (I have changed the wording to avoid explaining the conventions that the authors introduce earlier which would lengthen the post unnecessarily),
...
2
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0answers
58 views
A map (big picture) of the relationship of all areas in mathematics (including probability, stat, and information theory, etc)
Update 10/15:
What I could remember is the picture was under a section named "interesting stuff" (something like this), with a link toward the picture (if I remember it correctly). Also, the professor ...
3
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1answer
72 views
Classification of monoidal closed structures
The motivations for this question are somewhat vague probably. I am trying to have a better understanding of monoidal closed structures. In order to do so I would like to collect unusual examples and ...
1
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1answer
57 views
Alternative Proof to “Prove that it cannot be proven that ”The United States had more fallow acreage than planted acreage"
Given:
A ten year comparison between the United States and the Soviet Union
in terms of crop yields per acre revealed that when only planted
acreage is compared, Soviet yields were equal to 68 ...
1
vote
1answer
58 views
General rule of thumb for tensor products.
When would I want to use a tensor product? For example, say I am trying to derive "something" but, to get to the right derivation, I should use the tensor product.
The question comes from quantum ...
13
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4answers
447 views
What does a topology do, and what makes a particular topology the 'right' one?
From Wikipedia:
The same set can have different topologies. For instance, the real line, the complex plane, and the Cantor set can be thought of as the same set with different topologies.
[Aside: ...
7
votes
0answers
208 views
A definition of differentiable functions for arbitrary topological spaces
Background
It is well-known that there is no notion of derivative for arbitrary topological spaces. However while investigating the notion of derivative as we find in one variable real analysis I ...
2
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1answer
48 views
Looking for intriguing applications of martingales
I've been studying martingales before I start graduate school in statistics, and I'd like to ask, what are the most intriguing or surprising applications of martingales that you've come across, either ...
1
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1answer
105 views
Is there a notion differentiating $\frac1{\mbox{countable }\infty}$ and $\frac1{\mbox{uncountable }\infty}$?
It is accepted belief $\mbox{countable }\infty$ is not $\mbox{uncountable }\infty$. Is there notion differentiating $\frac1{\mbox{countable }\infty}$ and $\frac1{\mbox{uncountable }\infty}$ (latter ...
2
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0answers
65 views
Do we have to redo category theory when learning about enriched categories? [closed]
I'd like to know whether there exists a common language that encompasses both categories and enriched categories, so that results pertaining to either may be proven in a uniform way. I'd prefer it if ...
6
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2answers
398 views
Why is Catalan's constant $G$ important?
I am aware that Catalan's constant appears in the evaluation of many definite integrals, as well as in the evaluation of certain infinite series, and is a special value of a function closely related ...
1
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1answer
90 views
Two questions regarding the convention concerning concrete categories
Definition of Concrete Categories
Let $\mathbf{X}$ be a category. A concrete category over $\mathbf{X}$ is a pair $(\mathbf{A}, U)$, where $\mathbf{A}$ is a category and $U : \mathbf{A} \to \...
2
votes
1answer
86 views
Importance of Axiom of Choice (or its weak form) in Real Analysis
By Wikipedia article on Axiom of dependent choice, it is necessary to have it for development of real analysis. The ${\mathsf {DC}}$ says:
Axiom (${\mathsf{DC}}$). For any nonempty set $X$ and ...
5
votes
1answer
186 views
In algebraic geometry, what kind of theory can only be described by topos but not a site?
A (Grothendieck) topos is defined to be a category equivalent to the category of sheaves on some site. The main difference for a topos and a site is about their morphisms. I noticed that some books ...
14
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5answers
2k views
Intuition Wanted: Why Define Integrals Component-Wise
In our analysis course, we just defined the following:
Let $g := (g_1, \ldots, g_n): [a, b] \to \mathbb{R}^n$, where $g_1, \ldots, g_n: [a,b] \to \mathbb{R}$ are integrable.
Then we call the ...
39
votes
8answers
3k views
Why are algebraic structures preserved under intersection but not union?
In general, the intersection of subgroups/subrings/subfields/sub(vector)spaces will still be subgroups/subrings/subfields/sub(vector)spaces. However, the union will (generally) not be.
Is there a "...
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1answer
108 views
What mathematics cannot be reduced to pigeonhole?
Pigeonhole is a fundamental principle without which state of mathematics will be much different. However what examples of good mathematics has not yet been proved and cannot be proved with pigeonhole ...
4
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4answers
238 views
A graphical representation of Mathematics as a whole?
Does a graphical representation of mathematics, its fields and subfields, exist ?
Meaning, for instance a graph where vertexes are fields of mathematics (e.g convex geometry, Lie algebra, Kahler ...
1
vote
3answers
83 views
What can be learned for number theory from geometrical constructions (and vice versa)?
Even though this question of mine was not so well received at MO I'd like to pick two examples and make a question out of them here.
Consider these two pairs of geometrical constructions which yield ...
3
votes
3answers
107 views
How do we get past how **every** outcome is very unlikely?
Edit: This question is about rejecting the null hypothesis.
Last month my evil twin and I were at a game show.
The rules are as follows: There is a sealed booth with two magic boxes. Box A has a ...
13
votes
1answer
224 views
On the clarification of Manin's remark about Gödel’s incompleteness theorems
In his paper Georg Cantor and his heritage Yuri I. Manin writes (see page 7, 3rd paragraph),
Baffling discoveries such as Gödel’s incompleteness of arithmetics
lose some of their mystery once one ...
2
votes
0answers
95 views
The shape and group structure of an elliptic curve over $\overline{\mathbf{F}_p}$ and intermediary extensions
Let $p$ be prime, let $q$ be a power of $p$ and let $E/\mathbf{F}_q$ be
an elliptic curve defined over the finite field $\mathbf{F}_q$. Let $\overline{\mathbf{F}_q}$ be the algebraic closure of $\...
5
votes
0answers
116 views
Motivation behind Primary Decomposition
I am reading Atiyah's Commutative Algebra chapter on Primary Decomposition. I understand the proofs but I have no intuition as to
How did one come up with definition of a primary ideal $q$ as
$...
3
votes
1answer
77 views
Why care distribution functions more than random variables?
This may be wrong, but I have often heard some saying " we mainly care about CDFs". Similarly, in textbooks, one sees $X \sim N(0,1)$, without any reference to sample space. But why - and how do we ...
5
votes
1answer
191 views
Mandelbrot and Julia fractals for $z_{n+2} = z_{n+1}^2 + z_n^2 + c$
The Mandelbrot and Julia type fractals are very Well known.
But such fractals follow from
$$z_n = f(z_{n-1},c)$$
In other words a recursion that only depends on the previous value and a constant.
(...
1
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0answers
56 views
Does the defintion of chain equivalence have anything to do with liebniz product rule of differentiation?
I have this vague/ big picture question which might be too vague to answer (I don't mind it being deleted in this case). Do chain equivalences have anything to do with Leibniz product rule of ...
2
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1answer
182 views
The context & motivation for the Tits alternative in combinatorial group theory
The Details:
Definition 1: A class $\mathcal{G}$ of groups satisfies the Tits alternative if for any $G$ in $\mathcal{G}$ either $G$ has a free, non-abelian subgroup or $G$ has a solvable subgroup ...
1
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1answer
111 views
There is a natrual connection on the tangent bundle?
I come up with a (maybe stupid) question: let $M$ be a smooth manifold, then the exterior differential $d$ is a natural connection on $\Omega^k(M)$, hence by dualizing we get a natural connection on $...
0
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1answer
63 views
On multiplicative and additive properties of cyclotomic polynomials
Is there explicit relation between $\Phi_{a+b}(x)$, $\Phi_{ab}(x)$, $\Phi_{a}(x)$ and $\Phi_{b}(x)$ at general coprime or non-coprime $a,b\in\Bbb Z$?
If $a,b$ are distinct primes then we have $x^{ab}-...
3
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0answers
113 views
What makes a math problem important?
Given that pure mathematics is, by definition, not concerned with applications, how does one decide that one problem is more valuable than another? Is it just a matter of certain topics becoming ...
0
votes
0answers
47 views
Analogies and differences between polynomial evaluation and modulo operations
Given a polynomial $f(x)\in\Bbb Z[x]$, prime $p$ and integer $a$ are there analogies and differences between evaluating $f(x)$ at $x=a$ and computing $a\bmod p$? Both look like some kind of function ...
0
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0answers
34 views
Formulas without efficient algorithms?
Suppose the fastest known method to multiply two decimal numbers is an exponential time algorithm. Would it still be beneficial to mathematics having formulas like the following for positive integers?
...
1
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0answers
78 views
Why, intuitively, are propositional resolution proofs so long?
I'm trying to gain an intuitive understanding of why propositional resolution proofs tend to be so long.
As every essential prime implicant can be produced via resolution, intuitively I would have ...
12
votes
1answer
427 views
Mathematical disciplines with high thresholds
Are there mathematical disciplines that are extremely inaccessible, with very high thresholds even for those who have the necessary prerequisites?
Number theory and graph theory, for example, are ...
3
votes
2answers
323 views
Books on the philosophy of geometry
I am looking for recent books ( say published after 2000) on the philosophy of geometry, most books on the philosophy of mathematics seem to ignore or bypass geometry at all or am I just looking with ...
12
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2answers
217 views
$\pi$ when not in base 10
Very novice amateur mathematician here. My daughter (8 yo) is a math junkie and is trying to wrap her head around irrational numbers. We were talking about $\pi$, and I rambled on about how folks have ...
4
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3answers
910 views
Why introduce the $p$-adic numbers?
My current intuition about the p-adic numbers comes from the following three facts:
You can describe $Gal(\overline{\mathbb{Q}}/\mathbb{Q})$ with the $Gal(\overline{\mathbb{Q}}_p/\mathbb{Q}_p)$ ...
4
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0answers
127 views
Mathematics Textbooks that exemplify “Understanding” Mathematics.
I hope this question isn't considered too strange.
Gowers argues in "The Two Cultures of Mathematics" That mathematicians can be broadly categorized as those interested in understanding mathematics ...
5
votes
1answer
141 views
Fields with an overlap between logic and algebra?
I was curious if there is any field of study that uses both logic and algebra. To clarify, logic and analysis overlap in areas like descriptive set theory, and there are a lot of logic ideas in areas ...
5
votes
1answer
131 views
Structure preserving maps, and their use for understanding math.
A warning, I've labeled this a soft question, because I'm not quite sure I know what I'm asking.
In general, the study of some mathematical structure X (a function, a shape, whatever) becomes more ...
6
votes
1answer
1k views
Gaining a Deep Understanding of Theorems
As one might infer from my user name, I am currently pursuing an autodidactic path in pure mathematics while awaiting the real math classes next year at university. I recently bought Dummit and Foote'...
1
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0answers
50 views
A simple clarification on joint probability inequality.
Suppose we have $N$ balls and we have an experiment that is set up in the following way.
Your goal is to pick a particular ball that is fixed. At each trial you pick $N^{1-c_1}$ balls and replace. We ...
5
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1answer
550 views
Why are all metrics are essentially equivalent on compact spaces?
In his book Poincaré's Legacies, Terence Tao writes on p. 215:
Since all metrics are essentially equivalent on compact spaces, we
see that <...>
What exactly does he mean by that? Could ...
