# All Questions

**2**

votes

**0**answers

70 views

### Regularity of measures in the theorem of Riesz

There are two concurrent theories of measure/integration on a locally compact topological spaces: either as positive linear forms on the space of continuous functions with compact support, or as Borel ...

**4**

votes

**2**answers

162 views

### Normal Covering of a Finite Group

Suppose $G$ is a finite group and $N_1, N_2, \cdots, N_k$ are proper normal subgroups of $G$. The set $\{ N_1, \cdots, N_k\}$ is called a normal cover for $G$, if $G = \cup_{i=1}^kN_i$. I need to the ...

**1**

vote

**1**answer

49 views

### Expected value of the inverse of a random, truncated Haar matrix

Let $Q$ be a (say 4x4) unitary matrix, distributed according to the Haar distribution. Denote the upper left 2x2 submatrix of $Q$ as $Q_{1:2,1:2}$. I am interested in the following expectation:
$E(I ...

**2**

votes

**0**answers

106 views

### Uniqueness of scalar curvature

I'm reading Gromov's notes
http://www.ihes.fr/~gromov/topics/SpacesandQuestions.pdf
and at page 7 they say that there is a unique second order differential operator $S$ from the space of Riemannian ...

**-1**

votes

**0**answers

17 views

### Probability of rolling the same number n or more times in m rolls of a k-sided dice [migrated]

So the only approach I can find to solve this problem is making computer simulations, anyone can explain a mathematical way to solve it? or recommend a book that can explain this topic.
thanks.

**-1**

votes

**1**answer

40 views

### How to construct a semi-positive definite matrix in this form: (L=D-A')

As known, the graph Laplacian $L = D - A$ is semi-positive definite.
What if there is a matrix $A'$ where
$$ A'_{ij} = \begin{cases} A_{ij}, \quad if A_{ij} >0 \\ -\varepsilon, \quad if A_{ij} = ...

**2**

votes

**2**answers

213 views

### System of boolean equations, Satisfiability

Are there any methods to "solve" large systems of boolean equations?
$$x_{i1}\vee x_{i2}\vee x_{i3} = b_i, \quad\text{for}\quad i=1,\dots,N,$$
where $x_i, b_i \in\{0, 1\}$
For example
$$x_{1}\vee ...

**8**

votes

**1**answer

113 views

### Reconstructing a string from random samples

What is known about the following problem?
Reconstruct a string $\sigma$ of known length $n$ over a known
alphabet $\Sigma$ from a collection of uniformly and independently
chosen $k$-long ...

**0**

votes

**0**answers

36 views

### connected Polish groups

We know that a connected locally compact Hausdorff topological group is a pro-Lie group, by the Gleason-Yamabe theorem. Is there a known characterisation of the connected Polish groups?

**0**

votes

**1**answer

101 views

### Complementation in tensor products

This question, however looks innocent, looks non-trivial to me. Suppose that $X$ and $Y$ are Banach spaces and let $\alpha$ be any reasonable cross-norm on $X\otimes Y$. Reasonable means that ...

**0**

votes

**1**answer

201 views

### Is there a formula that can predict the primes in the sequence of ratios of consecutive superior highly composite numbers? : $2, 3, 2, 5, 2, 3, 7,…$

This is the sequence of prime numbers which are the elementary building blocks for the superior highly composite numbers:
$2, 3, 2, 5, 2, 3, 7, 2, 11, 13, 2, 3, 5, 17, 19, 2, 23, ...$
The $n^{th}$ ...

**1**

vote

**1**answer

115 views

### Divisibility of divisors in some tori and lattices

Let $E$ and $E'$ be two general elliptic curves. We consider the $2$-dimensional torus $A:=\frac{E\times E'}{(u\times u')\left((\mathbb{Z}/2\mathbb{Z})^2\right)}$, where ...

**6**

votes

**1**answer

127 views

### Lie group actions with only one orbit type, but not defining a principal bundle

Searched-for situation: A compact connected Lie group acts effectively on a closed Riemannian manifold by isometries, such that there is only one orbit type of dimension strictly less than that of the ...

**11**

votes

**1**answer

172 views

### Can infinitely many alternating knots have the same Alexander polynomial?

There exist many constructions of infinite families of knots with the same Alexander polynomial. However, alternating knots seem very special. While there are also many result on restricting the form ...

**0**

votes

**0**answers

42 views

### Independent Quasi Monte Carlo Sequences

I am generating some copulas with MonteCarlo and QuasiMonteCarlo sequences. In particular, I would like to generate a Student's t copula with QMC numbers.
Here is my problem: for Student's t copula I ...

**0**

votes

**0**answers

47 views

### Odd length repetends in recurring decimals [on hold]

For any number n the reciprocal can be expressed as a decimal, which will be composed of a recurring pattern as long as n is co-prime with 2 and 5. In general terms 1/n will produce a recurring ...

**1**

vote

**0**answers

86 views

### Applications of composition operators on Sobolev spaces

I wold like to know some examples where composition operators on Sobolev spaces are useful. I'm in the following situation.
$L^1_p(D)$ - homogeneous Sobolev space, in other words space of locally ...

**8**

votes

**1**answer

294 views

### Is more alternating always better?

While thinking about this interesting question asked by Dylan Thurston, it occured to me that in every case that I know, the closer a knot diagram is to being alternating, the better its properties. ...

**3**

votes

**1**answer

82 views

### Existence of subgraphs when given its degree sequence

For a given simple graph $G$ with $n$ vertices $v_1,v_2,\dots v_n$, the corresponding degree sequence is $d_1,d_2,\cdots,d_n$. My qusetion is:
How to determine whether there exist subgraphs in $G$ ...

**1**

vote

**1**answer

122 views

### About Section 4.2 in 'introduction to the spectral theory of automorphic forms' by Iwaniec

In Section 4.2 in 'introduction to the spectral theory of automorphic forms' by Iwaniec, the author said that the kernel of the invariant integral operator
$$
(Lf)(z)=\int_{\mathbb{H}}k(z,w)f(w)d\mu w
...

**0**

votes

**0**answers

37 views

### are these two groupoids Morita equivalent? [on hold]

We take the action groupoids $\mathbb{T} \rtimes_\alpha \mathbb{Z}_2$ and $\mathbb{T} \rtimes_\beta \mathbb{Z}_2$, where $\alpha(z)=-\bar{z}$ and $\beta(z)=\bar{z}$. Are these Morita equivalent?

**-5**

votes

**0**answers

131 views

### Zariski Problem [on hold]

In char p>3 find a Zariski Surface with geometric genus zero and not rational
another question:create a mathematical theory of Thom catastrophy prediction in particular earthquake prediction

**3**

votes

**1**answer

56 views

### Is the square diagram of index and exponential maps in $K$-theory of $C^*$-algebras anti-commutative?

Assume we have a $3\times 3$ grid with rows and columns being short exact sequences of $C^*$-algebras.
This gives a grid of 6-term exact sequences: 3 "horizontal" sequences and 3 "vertical" ...

**14**

votes

**0**answers

472 views

### Positive binary quadratic form plus univariate monic cubic (giving Hilbert class field)

We have the Lucas numbers, $$ L_1 = 1, \; L_2 = 3, \; L_3 =4, \; L_4 = 7, L_5 = 11, \; L_{n+2} = L_{n+1}+ L_n \; . $$
Question: is it the case that
$$ f(x,y,z) = 4 x^2 + 3 x y + 9 y^2 + z^3 + 3 z ...

**0**

votes

**0**answers

69 views

### endoscopy and simply connectedness

Let $G$ be a connected reductive group with $G_{der}$ simply connected over a local field $F$.
Let $\hat{G}$ be its Langlands dual, $s$ a semisimple element in $\hat{G}$ and $\hat{H}=\hat{G}_{s}$.
...

**-2**

votes

**0**answers

31 views

### How does one define the universal curve over the moduli space of stable curves [migrated]

In relation to the Prym class. How does one define the universal curve $\pi:\bar{\mathcal{C}_g}\longrightarrow\bar{\mathcal{M}_g}$ for genus $g\geq 2$ and their dualizing sheaf $\omega_g$.

**4**

votes

**0**answers

150 views

### Visibility interpretation of Riemann zeta zeros on the critical line?

This is a long shot, but ...
The fraction of $\mathbb{Z}^2$ lattice points
visible from the origin
$1/\zeta(2)=6/\pi^2 \approx 61$%.
The fraction of $\mathbb{Z}^3$ lattice points visible
from the ...

**0**

votes

**1**answer

37 views

### regarding Uniform Algebra on a compact set [on hold]

Suppose $K\subset\mathbb{C}$ is compact and let $R(K)$ be the uniform algebra of rational functions on $K.$ Moreover assume that $R(K)$ contains $\overline{z}.$ How to show that if a rational function ...

**3**

votes

**1**answer

105 views

### What are the applications of Grillakis Shatah and Strauss paper?

I am studying the following paper.
Manoussos Grillakis, Jalal Shatah, and Walter Strauss, Stability theory of solitary waves in the presence of symmetry. I, J. Funct. Anal. 74 (1987), no. 1, 160–197.
...

**4**

votes

**0**answers

87 views

### A forked plane continuum

I came up with this question while trying to solve the following MO one:
Does every connected set that is not a line segment cross some dyadic square?
Suppose $C$ is a plane continuum (i.e. a ...

**1**

vote

**0**answers

90 views

### Skew symmetry for the Hilbert symbol

Let $K$ be a local field containing the group $\mu_n$ of $n$th roots of 1 and the $\theta_K:K^*\to G_K^{ab}$ be the reciprocity map. The we know that the Hilbert symbol $$K^*\times K^*\to \mu_n$$ ...

**0**

votes

**0**answers

32 views

### Symmetrization methods preserving smooth structure of manifolds [on hold]

I was wondering if there are any symmetrization methods that take smooth manifolds to smooth manifolds (or even better one can use the same coordinate charts)?
By symmetrization methods I mean: ...

**-2**

votes

**0**answers

28 views

### Non-deterministic Finite Automata With No Accept State [on hold]

If I have a NFA with no accept states (always returns false) am I able to have zero states or must I include a single one?

**2**

votes

**0**answers

54 views

### Measurability for disintegration of a kernel

Let $(x, A) \mapsto P(x, A)$ be a probability kernel whose "target" (wikipedia terminology) is a product space $Y \times Z$, and say both $Y$ and $Z$ are compact metric spaces. For every $x$ there is ...

**-7**

votes

**0**answers

49 views

### Determine the Limit [on hold]

I have a problem, I just need a answer. Thank you. I don't understate this problem.
http://i.imgur.com/pnG8gIl.png

**1**

vote

**2**answers

152 views

### Two questions related to $TS^{2}$ as a holomorphic manifold

We consider $TS^{2}$ as a 2 dimensional holomorphic manifold and fix an explicit holomorphic structure on $TS^{2}$ as it is indicated in the answer of Mike Usher to the following question. ...

**7**

votes

**0**answers

211 views

### Classifying space of the higher-structure diffeomorphism group

There is a higher extension of the classifying space $B \mathrm{Diff}$ of the diffeomorphism group implicit in the (infinity,n)-category of cobordisms with (X,zeta)-structure ...

**4**

votes

**3**answers

323 views

### Textbook request for class field theory [duplicate]

I am studying class field theory. I need good reference books, notes, or other materials which explain the following topics: ideles and ideals, Haar measure and integration on local fields, Fourier ...

**0**

votes

**0**answers

83 views

### Thin profinite groups - nonabelian analogues of p-adic integers

Let $p$ be a prime number, $S = C_p$ a cyclic group of order $p$, $G = \mathbb{Z}_p$ the profinite additive group of $p$-adic integers. It is well known that all the closed nontrivial subgroups of $G$ ...

**0**

votes

**0**answers

97 views

### Trivial representation in tensor square [migrated]

Taken from another question in this website. I am not sure why the following statement is true.
Suppose $G$ is a group and $V$ an irreducible representation of $G$. One has that ...

**0**

votes

**0**answers

44 views

### Is any integral log structure be a colimit of a direct system of fine log structures?

Consider log structure on a (Noetherian) scheme with \'etale topology in the sense of Fontaine-Illusie. I.e. a log structure on a scheme $X$ is an etale sheaf $M$ with a morphism of monoid ...

**4**

votes

**0**answers

163 views

### Navigation in a graph

The problem
Let $G=(V,E)$ be a graph. $k = O\left(\log(|V|)\right)$ distinct vertices are picked randomly from $V$. We call the set of chosen $k$ vertices $T$.
Assumptions about the graph: You may ...

**6**

votes

**1**answer

241 views

### Does there exist harmonic function with that property?

Can one construct a harmonic function $f$ defined in the unit disk with the condition $f(0)≥1$ such that area of $\{z∈D:f(z)>0\}$ is small enough, i. e. for every $\epsilon>0$ does there exist ...

**2**

votes

**0**answers

24 views

### Conditions for convergence of Euler's method

It is know that a sufficient and necessary condition for
$$\dot y(t) = f(y(t), t), \quad t > 0, \quad y(0) = y_0$$
assumes a unique solution of $f$ is Lipschitz in $y$ and continuous in $t$. ...

**4**

votes

**2**answers

158 views

### Do singular values dominate eigenvalues?

Suppose $A$ is an $n \times n$ complex matrix with singular values $s_1 \ge s_2 \ge \cdots \ge s_n$ and eigenvalues $(\lambda_i)_{i=1}^{n}$ arranged so that $|\lambda_1| \ge |\lambda_2| \ge \cdots ...

**1**

vote

**2**answers

149 views

### Graphs of tensoring modules

Let $A$ be a ring, and $L,M,N$ an $A^\mathrm{op} \otimes A$-modules.
$L \otimes_A M$ is then an $A \otimes A^\mathrm{op}$ module so we can tensor it again with $N$ to get an abelian group $(L ...

**1**

vote

**0**answers

170 views

### Kummer Coverings

Let $L_1$, $\cdots$, $L_k$ be homogenous linear forms in three variables $z_0$, $z_1$, $z_2$ defining $k$ lines in $\mathbb{P}_{2}$. Consider the abelian extension $K
((L_2/L_1)^{1/n}, \cdots, ...

**5**

votes

**3**answers

157 views

### Clustering of periodic points for a polynomial iteration of $\mathbb{C}$

Let $f : \mathbb{C} \to \mathbb{C}$ be a polynomial map of degree $q > 1$. Consider $E_n \subset \mathbb{C}$ the set of periodic points with period (dividing) $n$; generally, $|E_n| = q^n$. Since ...

**4**

votes

**0**answers

82 views

### Pseudodifferential operators on compact manifolds with boundary

I have heard that the square root of the Dirichlet (or the Neumann) Laplacian is not a pseudodifferential operator on compact manifolds with boundary. The context in which this was said was that ...

**0**

votes

**0**answers

144 views

### A question about Assaf Naor's review in Bourbaki about the Batson-Spielman-Srivastava result

I am referring to this article - http://www.cims.nyu.edu/~naor/homepage%20files/Exp.1033.pdf
If I understand right, the author states that his equations (8) and (9) are equivalent to the equations ...