# All Questions

**0**

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3 views

### Asymptotic decay for the inhomogeneous Schrödinger equation

Let $H$ be an Schrödinger operator $(-\Delta+V(x))$ with a radially symmetric and smooth potential and $H$ is e.s.a. on $C^\infty_0(\mathbb{R}^n)$, furthermore let $\lambda$ be an element of the ...

**0**

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21 views

### Generalization of the alternating sign test for convergence of a series?

I'm struggling with a series of the form $$\sum_n |a_n|\, s_n $$ where
$s_n$ is the sign of a simple function of $n$. The
$|a_n|$ monotonically decrease and are relatively simple functions of ...

**0**

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**0**answers

33 views

### Hilbert triples

I apologize if this is a trivial matter for the analysts out there, but I looked this up in a number of books (e.g., H. Brezis, J. Wloka) and could not find a satisfying discussion, one that would ...

**1**

vote

**0**answers

66 views

### Is there a relationship between the standard conjectures and Langlands program?

I would like to know are there connections between Standard conjectures on algebraic cycles and Langlands program (in the light of Motives, I assume)?
What implications would a development of the ...

**2**

votes

**0**answers

17 views

### A perturbation question for the intersection of C*-subalgebras

This feels like something I may have asked before (in which case, apologies) and it also might be some kind of "standard counterexample in a book on C* algebras".
Let M be a unital C*-algebra and let ...

**-1**

votes

**0**answers

78 views

### Old Math books, will research and sell most [on hold]

I saw an earlier thread on selling old math books. My dad was a professor at Manhattan College for many years, he passed away a couple of years ago and has tons of old math books. I promised him I ...

**2**

votes

**0**answers

24 views

### $L^p$ estimates for Ornstein-Uhlenbeck: what is known beyond hypercontractivity?

Consider an infinite-dimensional Gaussian random vector $X$, and a positive random variable $f(X) \in L^p, p > 1$. Let $f(X) \sim \sum_n f_n(X)$ be its (formal) chaos expansion. Let $(U_\rho, \rho ...

**1**

vote

**1**answer

61 views

### L-function of twist

I'd like to ask the following easy question, since I can't find a reference.
Let $X/\mathbb{Q}$ a smooth projective variety. How does one express the $L$-function of the twist, $L(H^i(X)(r), s)$ in ...

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10 views

### On the local L-parameter of U(3) obtained by the theta lift from U(1)

Let $E/F$ be a quadratic extension of number fields and $v$ a place of $F$.
Let $\sigma$ be a automorphic character of $U(1)(\mathbb{A}_F)$ and $\Theta(\sigma)$ the theta lift of $\sigma$ to ...

**1**

vote

**1**answer

86 views

### Characterization of a subset of $[0,1]$

Let $T\subseteq[0,1]$ be a subset containing $1$. Now we know that $T$ satisfies the following property:
For every $t\in [0,1)$, if there exists a decreasing sequence $\{t_n\}_{n\ge 1}\subset T$ such ...

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26 views

### Holder continuous analytic function

Assume that $0<\alpha<1/2$ and $f$ is analytic in the unit disk $D$ with $|f(z)-f(w)|\le M|z-w|^\alpha$. Can we state that in general $$\int_D |f'(z)|^2 dx dy <\infty?$$

**3**

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**0**answers

62 views

### Ways to show a system of polynomial equations has no solution

I came across the following system of polynomial equations on $X_1,\dots,X_{m-2}$:
$$
\begin{cases}
2X_{2t}+\sum\limits_{t=1}^{2s-1}(-1)^tX_tX_{2s-t}=0,\quad s=1,\dots,\frac{m}{2}-1,\\
...

**-1**

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**0**answers

13 views

### average dirichlet distribution

say that A and B are 2 Dirichlet distributions. Is there a way to know if the average of the values is still a Dirichlet distribution? If not, how to merge 2 Dirichlet "similar" distributions?

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**0**answers

12 views

### One dimensional foliation of surfaces with prescribed graph of foliation

According to the definition of the graph of a foliation by Winkelnkemper we ask the following questions:
Let $G$ be one of the following non hausdorff compact 3 dim manifold
1) $G$ ...

**-3**

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**0**answers

39 views

### How to calculcate frecency? [on hold]

I recently came across the concept of Frecency. I thought it was a typo, but apparently it's a combination of recency and frequency, used in Mozilla's URL bar.
What are possible formulas for ...

**10**

votes

**2**answers

161 views

### Minimal number of generators for $GL(n,\mathbb{Z})$

$\DeclareMathOperator{\gl}{GL}\DeclareMathOperator{\sl}{SL}$From de la Harpe's book "Topics in Geometric Group Theory" I learnt that $\gl(n,\mathbb{Z})$ is generated by the matrices $$s_1 = ...

**1**

vote

**1**answer

64 views

### Solution or Reference Request for a Closed Form of the Sum

I have been working for quite a while on finding a closed formula for the Legendre Symbol. Inspite of my best efforts I can't come anything better with a formula for the symbol ...

**0**

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**0**answers

15 views

### How to distribute groups over activities in rounds [on hold]

This problem started with my sister asking me how she can distribute 12 groups over 6 activities in 6 rounds. She wants to organize a camp for for year students. There are 6 acitvities and in every ...

**4**

votes

**1**answer

40 views

### Separability of the C*-algebra in the definition of K-homology

There are (at least) two approaches to K-homoology: one is via the so called dual algebra which is due to Paschke. The second is via the Fredholm modules and is due to Kasparov. In Nigel Higson's book ...

**4**

votes

**1**answer

56 views

### Comodule analogue for statement that a faithful representation of an affine group scheme generates all

If $V$ is a faithful finite dimensional representation of an affine group scheme $G$ over a field $k$, then every finite dimensional representation of $G$ is isomorphic to a subquotient of $\otimes^n ...

**7**

votes

**1**answer

78 views

### Fast computation of a Groebner basis - What is Possible

I need to compute a Groebner basis of 18 polynomials in 19 variables the terms of which have degree at most 3. My aim is to exploit a symmetry in a PDE problem and I am not an expert in algebra or ...

**-1**

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**0**answers

22 views

### graphical estimate of convergence rates [looking for textbook reference] [on hold]

I asked this question already in mathematics, but got no sufficient answer.
I am writing a paper for engineers. There, under other things, I compare convergence rates
of sequences $x_n \to x^*$, ...

**1**

vote

**0**answers

35 views

### Lower central series in a free pro-p group

Let $F$ be a nonabelian finitely generated free pro-$p$ group, $H \leq_c F$ of infinite index. Denote by $\{F_n\}_{n \in \mathbb{N}}$ the lower central series of $F$, and set $r_n = [F : F_nH]$.
Is ...

**2**

votes

**1**answer

51 views

### Intersection of closed geodesics in hyperbolic surface

This question may be easy but I could not come up with a proof.
Let $F$ be a hyperbolic surface of finite type (with finitely many boundary and finitely many puncture). Let $\gamma$ be a closed ...

**2**

votes

**1**answer

104 views

### Are the Szpiro ratios of 37b1 over certain number fields {33,39,42,48,51,66}?

Related to this question.
Szpiro's conjecture over number fields states that the Szpiro ratio is:
$$ \sigma_{E/K}=\frac{\log{|N_{K/Q}\Delta_{E/K}|}}{\log{|N_{K/Q} f_{E/K}}|}$$
Given $ \varepsilon ...

**0**

votes

**1**answer

32 views

### edge transitivity and edge deletion

Let G be a graph which has the following properties:
1) For every $e_1,e_2 \notin E(G)$, $G \cup e_1 \cong G \cup e_2$
2) For every $e_1,e_2 \in E(G)$, $G\setminus e_1 \cong G\setminus e_2$
i.e. ...

**0**

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**0**answers

48 views

### Maximal subgroups of indefinite special orthogonal group SO(p,q)

Can someone answer the following question:
Is there any classification of maximal proper Zariski-closed real subgroups of $SO(p,q)$ which are not parabolic, and satisfy the following conditions:
...

**5**

votes

**1**answer

118 views

### Square filling self avoiding walk [on hold]

I want to create an algorithm that fills a square grid with a random Hamiltonian path starting at a particular point. See this example.
One approach is to try a free direction as a next step, and ...

**1**

vote

**0**answers

129 views

### Learning roadmap in Algebra [on hold]

I am a senior undergraduate student in mathematics, I have a sound knowledge in the following areas:
a) Commutative Algebra
b) Field Theory and Galois Theory
c) Homological Algebra
My question is ...

**1**

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**0**answers

44 views

### Expanding graphs from iterated zig-zag product

Let $\Gamma \, zz\, G$ denote the zig-zag product of graphs $\Gamma$ and $G$.
Reingold, Vadhan, and Wigderson proved that the second largest eigenvalue of the normalized adjacency matrix of the ...

**-4**

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**0**answers

98 views

### How can I prove: If A is a subset of C and B is a subset of D, then the union of A and B is a subset of the union of C and D? [on hold]

How could I write a proof for the above statement, considering I'm studyng the first Enginnering math's course? (in other words, my math level is pretty basic)
Thanks in advance

**5**

votes

**0**answers

79 views

### How many simultaneous polynomial equations of degree 2 can software solve today?

Consider the following problem:
Input: $n$ polynomial equations of degree $2$ in approximately $n$ variables.
Each equation contains about $\sqrt{n}$ monomials.
We would like to find one ...

**0**

votes

**1**answer

89 views

### Convergence of complex series that are not absolutely convergent?

Does anyone know of a convergence test for a complex series of the form
$$\sum_n a_n \cdot \exp(i \cdot b_n)$$
?
The particular series I need to understand has a_n going to zero as n goes ...

**1**

vote

**1**answer

77 views

### Expression and growth bound for $r_{p^m,k}(n)$

Let's define , $$R_{p^m,k}(n)=\#\{(a_1,\dots,a_k)\in\mathbb{Z}^k:\sum_{i=1}^ka_i^2\le n \ \text{and} \ p^m|\sum_{i=1}^ka_i^2\}$$
what will be growth bound of $R_{p^m,k}(n)$? This can be thought as a ...

**4**

votes

**1**answer

96 views

### Inequality due to Siegel (assumptions) and upper bounds on number field discriminants

In Siegel's 1969 paper, Abschätzung von Einheiten, on page 73, he states the inequality
$$\log\sqrt d\le n-1+{n\over 2}\log\pi+r_2\log 2\qquad (*)$$
and compares with the bound due to Minkowski that
...

**0**

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39 views

### Bounding the absolute value of a polynomial involving a Diophantine equation

Let $\mathbf{z}\in\mathbb{C}^n$ with entries $z_1,z_2,\ldots,z_n$. I would like to bound the following quantity
\begin{equation*}
...

**-7**

votes

**0**answers

87 views

### Proof that $\sqrt2$ is irrational [on hold]

Question: Using fundamental theorem of integers and the fact that every natural number that is not prime, prove that $\sqrt{2}$ is irrational unless $n=m^2$ for some $m\in\mathbb N$.
Here is how I ...

**0**

votes

**1**answer

87 views

### Number of solutions in a sum of squares Diophantine equation

Let $n$ be an integer. I'm interested in upper bounding the number of integer solutions of
\begin{equation*}
x_1^2+x_2^2+\ldots+x_p^2=y_1^2+y_2^2+\ldots+y_p^2,
\end{equation*}
where for all ...

**0**

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**0**answers

39 views

### u-Invariants of p-adic function fields

In his Paper "Fields of u-invariant 9" Oleg Izhboldin points out that for a algebraic closed, finitely generated field $k$ we have $u(k)= 2^{cd(k)}$. In particular we have
...

**-2**

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**0**answers

37 views

### Studying Signal Processing [on hold]

I'd Like to ask two questions :
What is the difference between studying Signal processing (both Deterministic and statistical) in Department of Electrical Engineering versus Department of Mathematics ...

**-1**

votes

**0**answers

61 views

### Proof that at least one of the nontrivial zeta zeroes has an irrational height (assuming RH) [on hold]

This seems quite simple so its likely someone has done this before (a few Google searches returned empty and I would be really grateful for a relevant link), but in case it's new, I wanted to check if ...

**1**

vote

**1**answer

98 views

### Strong divisibility of Lucas sequences

Let $a$ and $b$ be relatively prime integers and let $u_n$ be their associate Lucas sequence, i.e., the second order linear recurrence sequence satisfying $u_0 = 0$, $u_1 = 1$ and $u_{n+2} = au_{n+1} ...

**1**

vote

**2**answers

80 views

### The set of matrices with same spectral radius

I am working on an optimization problem over the set of positive matrices (that is, matrices where all entries are positive numbers) that have the same spectral radius. My main problem is how to ...

**5**

votes

**1**answer

54 views

### Trees with a maximal convex hull: are the only optimal solutions Steiner trees?

For given $n\geqslant 3$, I'm looking for a connected set composed of $n$ equal segments in the plane such that the convex hull of it has maximal area $A(n)$. To simplify notation, we'll take ...

**0**

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**0**answers

50 views

### Bounding Random Quadratic Gauss sums

I'm interested in seeing whether the following is true. Assume $u$ is uniform on $[0,1]$ and $|\epsilon_k|=1$ for all $k=1,2,\ldots,n$. We have
\begin{align*}
...

**0**

votes

**0**answers

23 views

### Period doubling bifurcations [on hold]

In the bifurcation diagram, is it true that if the function $f_r(x)$ at $x^*$ (where $x^*$ is a fixed point where a bifurcation occurs) can be locally written as a smooth function then ...

**0**

votes

**0**answers

38 views

### Linear extensions and directed, rooted spanning trees

Let $P$ be a poset with a unique bottom element $\perp$ and view its Hasse diagram $H$ as an oriented graph. Can the principle of exclusion-inclusion
be used to calculate the number of linear ...

**3**

votes

**0**answers

82 views

### Singularities in mixed characteristic

Let $R$ be a regular local ring in mixed characteristic. Moreover, I assume that $R$ is the local ring of a point on a smooth $\mathbb Z_p$-scheme and that $R/pR$ is regular. ($\mathbb Z_p$ is the ...

**2**

votes

**1**answer

49 views

### Endomorphism Ring of Simple Abelian Varieties

I know that if $A$ is a simple abelian variety over a number field $k$ with all endomorphisms defined over $K$ then $\mbox{End}(A_K)\otimes \mathbb{Q}$ is a division algebra with a positive ...

**5**

votes

**0**answers

35 views

### Testing membership in a cluster algebra

Say I have a cluster algebra with principal coefficients and initial cluster $x_1,\ldots,x_n$. I don't want to invert the coefficient variables $y_1,\ldots,y_n$. The Laurent Phenomenon says that ...