Trending questions
159,041 questions
2
votes
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views
Fundamental domain of an involution on a manifold
What is known about the fundamental domain of an involution on a manifold? Eg., if the involution is free is it true that there exists a fundamental domain which is a smooth manifold with boundary?
- 658
1
vote
0
answers
124
views
Relation of automorphic representation and its constant term
Let $\pi$ be an irreducible non-cuspidal automorphic representation of a classical group $G$ defined over a number field $F$. Let $P$ be a maximal parabolic subgroup of $G$. Let $\pi'$ be the ...
- 1,019
3
votes
0
answers
167
views
Are motives of K3 surfaces of abelian type?
I refer to the article of van Geemen https://arxiv.org/pdf/math/9903146. What van Geemen calls the Kuga-Satake-Hodge conjecture suggests that for a K3 surface $X$ over $\mathbb{C}$, the summand $h^2(X)...
- 658
7
votes
1
answer
310
views
Homotopy between posets
This is entirely a new area for me and I apologise in advance if the questions are silly.
In Quillen's paper "Homotopy properties of the posets of non-trivial $p$-subgroup of a group" (see ...
- 139
1
vote
1
answer
219
views
What is the fastest known algorithm for evaluating a homogeneous binary polynomial?
This question was initially posted on math.stackexchange.com, but there is no appropriate answer, hence I have the right to publish it here again.
Let $f(x,y) = \sum_{i = 0}^d f_i x^i y^{d-i}$ be a ...
- 1,833
5
votes
0
answers
164
views
Does this weak omniscience principle have a name?
In constructive analysis, I'm looking at principles which follow both when there exists at least one discontinuous function from $\mathbb{R}$ to $\mathbb{R}$ (equivalent to WLPO i.e. $x > 0$ or $x \...
- 1,947
11
votes
1
answer
885
views
Which paper is the "Taubes trick" from?
In symplectic geometry, the "Taubes trick" is an argument used to show that a moduli space $\mathcal{M}(J)$, depending on a parameter $J \in \mathcal{J}$, is cut out transversely for generic ...
- 243
0
votes
0
answers
101
views
Generalized Laplacian
I was wondering if any of you had ever encountered operators on
$L^2(\mathbb{R}^2)$ of the form
$$
\nabla \cdot (A(x)\nabla)
$$
where $A(x)$ is some symmetric matrix field (viewed as $L^2(\mathbb{R}^{...
- 21
4
votes
0
answers
291
views
Lower bound on size of the set of sums and differences of non-orthogonal pairs of vectors over finite field
Consider $\mathbb{Z}_m^n$, an $n$-dimensional vector space over $\mathbb{Z}_m$.
For two sets of vectors $P = \left\{ p^i \right\}$ and $Q = \left\{ q^j \right\}$ and a skew-symmetric matrix $S_{ij}=\...
- 91
2
votes
0
answers
165
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Definition for "almost simple" linear algebraic groups
Proposition 2.18 from "Elementary abelian $p$-subgroups of algebraic groups" by R. Griess. used the term "simply connected almost simple linear algebraic group $G$" without ...
- 217
8
votes
1
answer
197
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Weakly compact cardinals in $L$: how long do branches take to appear?
Throughout, we work in $\mathsf{ZFC+V=L+}$ "There is a weakly compact cardinal," $\kappa$ is the first weakly compact cardinal and "tree" means "subtree of $2^{<\kappa}$ of ...
- 20.5k
5
votes
1
answer
203
views
Turing degrees of lim infs of computable functions
The limit lemma gives a natural characterisation of functions $f : \mathbb{N} \to 2$ with Turing degree below $0'$: they are precisely those that can be written as $f(n) = \lim_k f_k(n)$ where $f_k : \...
- 4,378
2
votes
0
answers
110
views
How to apply Pohlig Hellman using a very limited set of auxiliary inputs in that case?
So I was reading about Talotti, Paier, and Miculan - ECC’s Achilles’ Heel: Unveiling Weak Keys in Standardized Curves. The underlying idea is to lift the discrete logarithm problem to $\mathrm{prime}−...
- 87
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0
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82
views
How can complex abelian varieties degenerate to tropical abelian varieties
There is a similar interesting question here
which has not been answered. I therefore ask this question in the hope to get an answer. I wonder how a family of complex abelian varieties can exactly ...
- 85
10
votes
1
answer
496
views
Continued fractions of $\sum_{n=0}^k 1/n!$
Quantities $\sum_{n=0}^k 1/n!$ approximate $e$, but not very well by the standards of Diophantine approximation. One gets errors $|e-a/b|$ of roughly $1/(b\ln b)$ where one might hope for $c/b^2$
for ...
- 17.6k
1
vote
1
answer
117
views
Is every connection locally flat for an other connection?
Consider a $C^{\infty}$ connection $d_A = d+A$ on the unit ball $B^n\subset \mathbb{R}^n$. Does there exists another connection $d_{\tilde{A}} = d+\tilde{A}$ such that $d_{\tilde{A}} A = 0$? That is ...
- 363
2
votes
2
answers
335
views
Are there models of ZF in which all uncountable sets are super/hyper/ultra-singular?
This question is a follow up to that posting.
Recall the definition of super/hyper/ultra-singular set given in the linked posting.
Is there a model of $\sf ZF$ in which every uncountable set is super-...
- 11.3k
1
vote
0
answers
49
views
What makes the generalized projection different than metric on a Banach space?
I have came across the notion of generalized projection in Banach spaces, introduced by Ya. Alber and has seen many iterative algorithms being solved by using this projection. It helps in finding the ...
- 85
1
vote
1
answer
151
views
Does this sequence of Blaschke Product have rescaling limit $z-1$?
Background: The conformal conjugacy class of parabolic isometry of upper half plane $\mathbb{H}$ consists of $f(z) = z+1$ and $g(z)=z-1$.
Consider surjective proper holomorphic $F_n: \mathbb{H} \...
7
votes
2
answers
383
views
Connectivity of fibers under fibration replacement
Assume all the spaces mentioned below are simply connected CW complexes. Let $ f: X \to Y $ be a continuous surjctive map between CW complexes, where $ f $ is not necessarily a fibration. Assume that ...
- 1,177
1
vote
0
answers
59
views
Asymptotic behavior of the Hermite functions
I would like to understand the asymptotic behavior of the Hermite function :
$$\psi_k(x) = \frac{1}{\sqrt{2^k k!}}H_k(x) e^{-\frac{x^2}{2}},$$
where $H_k(x)$ is the $k-$th Hermite polynomial. For ...
- 21
2
votes
0
answers
91
views
Conjugacy between piecewise linear circle maps
Let $\mathcal{M}$ the Mandelbrot set,
$\mathcal{M}=\{c \in \mathbb{C}: \{Q_c^n(0) \}_{n \in \mathbb{N}} \text{ is bounded, where } Q_c(z)=z^2+c \}$
And let the hyperbolic or stable component, $H_n=\{ ...
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11
votes
1
answer
500
views
Uncountable families of measurable sets with pairwise positive intersections
Let $(X,\mathcal{B},\mu)$ be an arbitrary finitely additive probability measure space, let $a>0$ and let $(A_i)_{i\in I}$ be an uncountable family of subsets with measure $\geq a$.
Is there an ...
- 10.6k
3
votes
1
answer
220
views
Weak approximation in Krull domains
Suppose $R$ is a Krull domain with the field of fraction $K$. To every prime ideal $P$ of $R$ of height $1$, one can associate a $ \mathbb{Z}$-valued discrete valuation which we denote by $v_P$.
...
- 6,224
7
votes
2
answers
331
views
Does every subset of $\mathbb N$ with full natural density contain arbitrarily long geometric progressions?
We use the standard definition of natural density. We say a subset of $\mathbb N$ has full natural density if it has natural density $1$.
Question: Does every subset of the naturals with full natural ...
- 6,323
30
votes
2
answers
2k
views
Is every connected subgroup of a Euclidean space closed?
The question listed above (in the context of the complex numbers, but it is a reasonable question to ask in any dimension) was asked by a student in my complex analysis class, and I did not have an ...
- 114k
0
votes
0
answers
82
views
Solution modulo $9$ of certain linear equation implies triviality modulo $3$
Question: Let $k \geq 2$ and $r \geq 4$ be two natural numbers. We are given eight integers $\nu_{ij} \geq 0$ for every $1 \leq i \leq k$ and $1 \leq j \leq r$ such that the following two conditions ...
- 119
2
votes
1
answer
215
views
How can one test whether a given analytic curve in the plane is algebraic or not?
Suppose $\Gamma$ is an analytic Jordan curve in the complex plane $\mathbb{C}$. What are ways to test whether $\Gamma$ is (contained in) an algebraic curve, i.e., whether there exists a real ...
- 2,154
1
vote
0
answers
38
views
Is there an equivalent to the logistic map for a nonlinear path through some of the other nodules of the Mandelbrot set?
The logistic map can be related to the real axis of the Mandelbrot set, looking at the different cycle lengths as you pass through all the various nodules along the real axis. But there are other ...
11
votes
3
answers
672
views
Merging single-sorted and multi-sorted theories
The general theory of single-sorted (say, algebraic) theories is very similar to the general theory of multi-sorted (algebraic) theories. Each variable gets a sort, but apart from that nothing really ...
- 63.1k
3
votes
0
answers
144
views
An optimisation problem
Let $E\subset \mathbb R^2$ be compact, convex and connected. For $p_1,\ldots, p_n>0$ with
$$\sum_{i=1}^n p_i=1,$$
and a probability measure $\nu$ supported on $E$ of density $f$, we consider
$$\...
- 1,399
0
votes
0
answers
38
views
A general rule for approximating the perimeter of a set with finite perimeter in terms of the volume
I want to know if it is possible to have a general rule for approximating the perimeter of a set $E\subset \mathbb{R}^n$ with finite perimeter in terms of the volume (Lebesgue measure) of a sequence ...
- 747
4
votes
1
answer
140
views
Integrate unit normal vector over unit sphere intersected with a simplicial cone
Let $S^{d-1}$ be the unit sphere in $\mathbb R^d$. Consider a ($d$-dimensional) simplicial cone $C$ in $\mathbb R^d$ whose extremal rays are spanned by some unit vectors $\mathbf{u}_1,\ldots,\mathbf{u}...
- 135
9
votes
1
answer
425
views
Delta-generated spaces vs CW complexes
$\newcommand\Top{\mathrm{Top}}\newcommand\CW{\mathrm{CW}}\newcommand\Deltagenerated{\text{$\Delta$-generated}}\newcommand\Spaces{\mathrm{Spaces}}\newcommand\DeltaSpaces{\text{$\Delta$-Spaces}}$I am ...
- 719
1
vote
4
answers
799
views
Examples of long running and consecutively numbered international meetings [closed]
I just saw a poster at the next office's door announcing the
95th Annual Meeting of the International Association of Applied Mathematics and Mechanics.
Here is another example of a meeting I will ...
6
votes
2
answers
774
views
Finiteness of an integral
In a paper I am reading, the following seems to be claimed:
Let $f:[0,\infty)\to [2,\infty)$ be a continuous, monotonically increasing function with $\lim_{x\to\infty}f(x)=\infty$ and let $\alpha>3/...
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4
votes
1
answer
145
views
Stably embedded clone
Let $M$ be a first-order structure, considered as an element of the ambient set-theoretic universe $V$.
Clearly, for any $L_{\infty,\infty}$-formula $\varphi(\bar x)$ (with $\bar x$ finite, say) in ...
- 1,338
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votes
0
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159
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If $\omega_1$ is not inaccessible in $L$, how hard can it be to find a non-measurable $\Sigma^1_3$ set of reals?
In his wonderfully titled paper Can you take Solovay's inaccessible away? Shelah showed that if every $\mathbf{\Sigma}^1_3$ set of reals is Lebesgue measurable, then $\omega_1$ is an inaccessible ...
- 13.1k
1
vote
1
answer
242
views
The equation $ax^2 +by^2 =1 \mod P$ in cyclotomic field
Let $L$ be a cyclotomic field, and $P$ a prime ideal of $\mathcal{O}_L$.
is there any symbol for the equation $ax^2 + by^2 =1 \mod P$ and if so, is it computable in polynomial time?
if $a$ is ...
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6
votes
1
answer
293
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Prime number theorem via large sieve type sums
We know that the prime number theorem is equivalent to the statement
$$
M(x)=\sum_{n\le x}\mu(n)=o(x).
$$
By using Ramanujan sums, we can write $M(x)$ as
$$
M(x)=\sum_{q\le x}\sum_{\substack{0\lt a\le ...
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71
votes
8
answers
12k
views
Possible new series for $\pi$
In a recent (unfortunately over-hyped) preprint by Saha and Sinha, Field theory expansions of string theory amplitudes (arXiv:2401.05733), they present the following series for $\pi$:
$$\pi = 4 + \...
- 82.7k
1
vote
1
answer
230
views
Conjectured error term when counting square-free integers
It is well know that the density of positive square-free integers up to $x$ is asymptotically $x/\zeta(2)$. The error term
$$ E(x)=\sum_{1\leq n \leq x } \mu(n)^2 -\frac{x}{\zeta(2)}
$$ can easily ...
- 3,062
2
votes
1
answer
162
views
Are Cohen Generics Minimal Covers?
Are Cohen generics (in $2^\omega$) minimal covers?
I'm ultimately interested in this question for some more effective notion of forcing but I realized I wasn't sure how to show this even assuming full ...
- 3,029
2
votes
2
answers
383
views
Definition of Multivariable Antiderivatives
In the 1-dimensional case antiderivatives $F(x)$ of a function $f(x)$ have the following properties:
$F(x)=\int\limits_0^xf(t)dt$
$\frac{d}{dx}F(x)=f(x)$
$\int\limits_a^bf(t)dt = F(b)-F(a)$
Of ...
- 13.2k
1
vote
1
answer
214
views
Derived completeness of the inverse perfection
Fix a prime number $p$, and let $R$ be a ring of positive characteristic $p$. Consider the inverse perfection of $R$, which is defined as the inverse limit
$$
R^\flat = \varprojlim(\cdots \xrightarrow{...
- 125
3
votes
1
answer
136
views
For $\mathbb R^n \times Q \cong \mathbb R^m \times Q $ must $n = m$? ($Q$ is the Hilbert cube)
There are several theorems describing the topology on hyperspaces of convex subsets of $\mathbb R^n$ under the Hausdorff metric. For example Antonyan and Jonard-Pérez prove the space of compact convex ...
- 1,955
5
votes
1
answer
298
views
Partition induced by a cover
Let $X$ be a set and let $(Y_i)_{i \in I}$ be a family of (not necessarily pairwise disjoint) subsets covering $X$,
$$ X = \bigcup_{i\in I} Y_i.$$
For any subset $J \subseteq I$, we then define
$$ Y_J ...
- 9,853
5
votes
1
answer
423
views
What is the relationship between non-existence of those kinds of singular sets and AC?
Let's say a set $A$ is super-singular, if and only if, there exists a set $x$ such that $|A|=|\bigcup x|$ and $| A| > |x|$, and for each $y \in x$ we have: $ |y| \not > |x|$ .
A set $A$ is ...
- 11.3k
2
votes
2
answers
132
views
Invertibility of one matrix constructed by order n subgroup of symmetric group
Let $S_n$ be the symmetric group on $n$ elements $\{ 1,2,\dotsc,n \}$ and $G$ be a subgroup of $S_n$ of order $n$. Denote the elements in $G$ by $\{ \sigma_1,\dotsc,\sigma_n \}$. Let the matrix $A=(\...
- 21
1
vote
0
answers
112
views
References on the partial trace
For the Hilbert space $H^N:=L((\mathbb R^{3})^N,\mathbb C)$, consider the projection operator $D: H^N\to H^N$ as follows :
$$D(\Phi):=\left(\int_{(\mathbb R^{3})^N}\overline{\Psi(x_1,\ldots, x_N)}\Phi(...
- 1,399