All Questions

0
votes
0answers
3 views

Complex Kronecker foliation

Let $\theta \in \mathbb{C}$ be a fixed complex number. The submersion $f:\mathbb{C}^{2}\to \mathbb{C}\; \text{with}\; f(x,y)=y-\theta x$ defines a complex foliation on $\mathbb{C}^{2}$. Consider the ...
0
votes
0answers
3 views

Solving limit problems versus the difference quotient

I am working my way through a Calculus 1-level online course, and there is something about limits and the difference quotient that is bothering me. To define the limit used in the difference ...
0
votes
0answers
6 views

Cosets of the fixer of an action of a monoid on a finite set

Let $M$ be a monoid that acts transitively from the right on a finite set $X$. Assume furthermore that the action of $M$ on $X$ induces for every $m \in M$ a bijection on $X \to X, x \mapsto x.m$. Let ...
1
vote
1answer
38 views

Self-similarity for simple algebraic structures

I'm doing this thread because I have some ideas about how to define self-similarity in algebra, but I don't know if this is known at all. Any critics, comments and references are more than welcomed. ...
0
votes
0answers
23 views

Is there some Riemannian manifold's version of Whitney theorem?

Given any Riemannian or Semi-Riemannian manifold $(M,g)$, does there exist a Eucildean space $(E,g^\prime)$ of enough high dimension with metric $g^\prime=diag\{-1,-1,...,+1,+1,...\}$ with any n ...
2
votes
0answers
16 views

An upper bound for a average of a function in $L_{p}([0,1))$

Suppose that $ f $ is $ 1 $-periodic and that $ f \in {L^{p}}([0,1) $, where $ p > 1 $. Let $$ (D_{n})_{n \in \mathbb{N}_{0}} = \left( \left\{ I^{n}_{j},~ 1\leq j \leq 2^{n} \} \right\} \right)_{n ...
1
vote
0answers
10 views

Simultaneous vanishing of convolutions of Mertens function with itself

By a theorem of Landau, we know that all the step functions ($k\geq 1$) $$M_k(x)=\frac{1}{2\pi i}\int^{2+i\infty}_{2-i\infty}\frac{x^sds}{\zeta^k(s)s}=\sum_{n\leq ...
2
votes
0answers
25 views

centeredness in forcing iterations

Suppose $A$ is a complete subalgebra of a complete boolean algebra $B$, and $B$ is $\kappa$-centered. Let $G \subset A$ be a generic ultrafilter. Is $B/G$ $\kappa$-centered in $V[G]$? Naively, we ...
-2
votes
0answers
19 views

Treating The Differential of Independent Variables in Integral [on hold]

I need some comments from real infinitessimal calculus and real analysis point of view like limit-theorems etc. regarding the following Consider that B is constant ($\frac{dB}{dt}=0$) There is a ...
-4
votes
0answers
60 views

How to choose subject of pure math for PhD? [on hold]

I'm seeking about PhD in Maths. I'm really confused about choosing the area of research. I enjoyed studying and teaching Algebra & Topology, But I don't know how to start writing a research on ...
1
vote
0answers
35 views

Decomposition of non-singular matrix [on hold]

Is there any way to show that a non-singular matrix A can be partitioned as follows: \begin{eqnarray*} A&=&\left[ \begin{array}{cc} \underset{\left( k\times k_{1}\right) ...
2
votes
0answers
51 views

Faltings height in short exact sequences

Let $K$ be a number field and $0 \rightarrow A \rightarrow B \rightarrow C \rightarrow 0$ a short exact sequence of abelian varieties over $K$. Let $h(A)$ denote the logarithmic Faltings height ...
-1
votes
0answers
36 views

Example of an operator whose domain is infinite dimensional but range is not closed [on hold]

Give me an example of an operator $T:D->R$, such that $D$ is an infinite dimensional Hilbert space and $R$ is not closed/dense.
1
vote
0answers
21 views

Transversality of stable and unstable manifolds for geodesic flows associated to different metrics on the same manifold

Let $M$ be a closed smooth manifold carrying two negatively curved Riemannian metrics $g$ and $h$. Take a point $p \in M$ and vector $v \in T^{1}M$. Let $\gamma_{v,g}$ and $\gamma_{v,h}$ be the unique ...
3
votes
1answer
119 views

Is a “central” extension of $\mathbb{Z}/m\mathbb{Z}$ by $\mathrm{GL}_n$ necessarily split?

Let $m \ge 1$ be an integer, let $k$ be a field of characteristic $0$, and let $$ 1 \rightarrow \mathrm{GL}_n \rightarrow E \rightarrow \mathbb{Z}/m\mathbb{Z} \rightarrow 1 $$ be an extension of ...
-1
votes
0answers
97 views

Is $\{(\frac{3}{2})^{n}\}_{\mathbb{N}}$ is equidistributed in [0,1] (related open question) [on hold]

Is $\{(\frac{3}{2})^{n}\}_{\mathbb{N}}$ is dense in [0,1] (open question). A more general question is: Is $\{(\frac{3}{2})^{n}\}_{\mathbb{N}}$ is equidistributed in [0,1]?If so, Then density ...
0
votes
0answers
20 views

best MAX-SAT solver for ising spin glass [on hold]

What is the best MAX-SAT solver problems for Ising spin glass? I tried Scip-Max-sat and open-wbo. While open-wbo cannot solve the instance with only 27 variable Scip-max-Sat fail to solve the one with ...
9
votes
0answers
89 views

The real numbers object in Sh(Top)

If $X$ is a sober topological space, the real numbers object in the topos $\mathrm{Sh}(X)$ is the sheaf of continuous real-valued functions on $X$. This is proven very explicitly in Theorem VI.8.2 of ...
4
votes
1answer
84 views

properties of formal delta functions

The formal delta function is $\,\,\displaystyle\delta(x):=\sum_{n\in\mathbb Z}x^n. $ If we agree that expressions $(x+y)^n$ for $n\in\mathbb Z$ are always expanded in non-negative powers of the second ...
2
votes
0answers
42 views

Definition of Givental $J$-function of cotangent bundle of flag variety

I would like to know the definition of Givental $J$-function of cotangent bundle of flag variety. To state my question more precisely, let us briefly recall the definition of the Givental $J$-function ...
0
votes
0answers
14 views

Eigenfunction of ergodic skew product fixed by commutator?

Background: Let $(Y, \mathcal{B},\mu,T)$ be an ergodic probability system and let $G$ be a compact metrizable group with compact subgroup $H$. Given a measurable map $\rho:Y \to G$. We may define the ...
1
vote
0answers
31 views

Mutant pairs distinguished by [2,1]-colored HOMFLY polynomials

Morton and Cromwell showed that the famous mutant pair, Kinoshita-Terasaka and Conway knots, can be distinguished by HOMFLY polynomials colored by [2,1] Young diagram. Are there any other mutant pairs ...
9
votes
1answer
290 views

Parity of the Prime Counting Function

I am interested in the distribution of the parity of $\pi(x)$, the prime counting function, over the natural numbers. Let: $\ \ E_n := \left\{ k \in \left\{1,\dots,n\right\} : \pi(k) \equiv 0 \mod 2 ...
0
votes
0answers
30 views

Stochastic methods for solving very high-dimensional PDE

I am looking for stochastic methods for solving a very high-dimensional PDE (with one time dimension and very large number of spatial dimensions), which would reduce it to a lower-dimensional problem, ...
0
votes
0answers
27 views

bounds on a series with binomial coefficients

I have the following series $\sum\limits_{l=1}^n {n\choose l} \alpha^{\beta^l}$ where $\alpha > 0$and $0 \leq \beta \leq 1$. Can anybody guide me how I can evaluate it or find some tight upper ...
-2
votes
0answers
62 views

What is the joint distribution of sample mean and sample variance of normal distribution? [on hold]

${X_i} \sim N\left( {\mu ,{\sigma ^2}} \right)$, define $\bar X = \frac{1}{{n}}\sum\limits_{i = 1}^n {{X_i}} $, ${S^2} = \frac{1}{{n - 1}}\sum\limits_{n = 1}^n {{{\left( {{X_i} - \bar X} ...
8
votes
1answer
159 views

Special fiber of $X(p)$ in characteritic $p$

Let $p \geq 5$ be a prime. Let $Y(p)$ be the fine moduli space representing elliptic curves + basis of the $p$-torsion over $\mathbb{Q}_p$ and let $Y_1(p)$ be the fine moduli space representing ...
26
votes
0answers
281 views

Determinant of a determinant

Consider an $mn \times mn$ matrix over a commutative ring $A$, divided into $n \times n$ blocks that commute pairwise. One can pretend that each of the $m^2$ blocks is a number and apply the $m ...
2
votes
0answers
48 views

Are there two-sided $\varepsilon$-expanders with independent sets of size $(1-\varepsilon)n$?

Terry Tao's notes on expander graphs has the following exercise: Exercise 13 Let $G$ be a $k$-regular graph on $n$ vertices that is a two-sided $\epsilon$-expander for some $n > k \geq 1$ and ...
3
votes
1answer
109 views

semi-classical Green's function

I am reading Gutzwiller's papers on the relation between Hamiltonian flows and solution to Schrodinger equations. In the two papers, he gave a semi-classical approximation of the Green's function to ...
2
votes
0answers
86 views

Abelian covers of compact Kahler manifolds

Let $X$ be a compact Kahler manifold and $A\subset H_1(X,\mathbb{Z})$ be a subgroup. Corresponding to $A$ there is an abelian covering $X_A \to X$ with $Deck(X_A)=H_1(X,\mathbb{Z})/A$. For example if ...
1
vote
3answers
153 views

Estimating a sum [on hold]

Good morning everyone, I would like to make a question about estimating a sum. Consider the following sum $$S_n:=\sum_{k=0}^{n-1} \frac{k^2}{(n-k)^2 (n+k)^2} $$ It is easy to see that this sum is ...
3
votes
2answers
165 views

What is known about this series?

I recently came across the following function which intrigues me: \begin{equation} f(\alpha):=\sum_{i=0}^\infty \frac{\alpha^{i(i+1)/2}}{i!}. \end{equation} For $-1\leq \alpha\leq 1$ this function is ...
10
votes
4answers
649 views

Difference between ZFC and ZF+GCH

I hear that the axiom of choice (AC) derives from The generalized continuum hypothesis(GCH). And also hear that both AC and GCH are independent of Zermelo–Fraenkel set theory(ZF). So, I'm just ...
4
votes
0answers
56 views

Outer automorphisms of direct product of residually finite groups

Let $A,B$ be finite generated residually finite groups such that $\mathop{Out}(A)$ and $\mathop{Out}(B)$ are residually finite. Is $\mathop{Out}(A\times B)$ residually finite? If not, what is the ...
-2
votes
0answers
26 views

Probability of having a connected network in a random graph [on hold]

I'm trying to solve this programming problem out of interest in my spare time and want to make sure my maths is correct. "The people of Absurdistan discovered how to build roads only last year. After ...
0
votes
1answer
160 views

Relations between characteristic classes of a group and the Stiefel-Whitney/Pontryagin classes

Let $X$ be a closed manifold and $BG$ be the classifying space of a group $G$ A map from $X$ to $BG$ induce a map from $H^*(BG,Z)$ to $H^*(X,Z)$ by pull back. Let $GH^*(X,Z)$ be the subgroup of ...
2
votes
0answers
107 views

Argument againts the $abcd$ conjecture with extra gcd conditions

Got an argument and numerical support againts the $abcd$ conjecture with extra gcd conditions (observe that this is different from the $abc$ and the $abcd$ conjectures). This thesis p. 20 defines the ...
4
votes
0answers
64 views

Optimal planar net for catching convex shapes

Imagine you want to make a net out of string to filter and catch objects of a certain size, minimizing the length of string employed. (This actually arises in filtering biological impurities from ...
-4
votes
0answers
92 views

I am doing P.H.D. in İstanbul University. My research is about Character Theory of Finite groups [on hold]

How can I define the p(t)-adic valuation and absolute value on F(t)?
-3
votes
0answers
82 views

Algebra Constructions [on hold]

What kind of constructions of associative algebras are normally used in theory and examples besides the following ones: group algebra monoid algebra (such as Solomon-Tits algebra) tensor product ...
1
vote
1answer
49 views

locally topologically finitely generated t.d.l.c. group

I am trying to find an example of the following situation. $G$ is a t.d.l.c. (totally disconnected locally compact) $\sigma$-compact topological group in which every compact open subgroup is ...
-2
votes
0answers
70 views

Category of compact manifold [on hold]

Question 1: What we know about the sub-category $Met$ of $Top$ whose objects are metrizable topological spaces and whose morphisms are the isometries. Question 2: Let $X$ be any compact manifold. We ...
0
votes
0answers
84 views

A curious property of Ramanujan's function $\tau(n)$

As it is well known, Ramanujan's $\tau(n)$ function can be defined through the power series expansion of the modular discriminant: $$\Delta(q)=q\prod\limits_{n=1}^\infty (1-q^n)^{24}=\sum ...
0
votes
1answer
90 views

Sylow-subgroups of the group of units of a finite field [on hold]

Let $K$ be a finite field with $p^n$ elements. Then the group of unit is cyclic of order $p^n-1$. What are the primes which are dividing $p^n-1$? What are the Sylow-subgroups of the group of units of ...
-3
votes
0answers
110 views

Finding closed form of : $\int_0^1 \frac{\log(1+x)}{1+x}\log\left(\log\left(\frac{1}{x}\right)\right) \ dx$

$ \newcommand{\pars}[1]{\left(\, #1 \,\right)} \newcommand{\dd}{{\rm d}}$ Finding closed form of the below: $$\int_0^1 \frac{\log(1+x)}{1+x}\log\left(\log\left(\frac{1}{x}\right)\right) \ dx$$ This ...
6
votes
4answers
261 views

Bound on sum of complex summands involving binomial coefficients

I am trying to find the asymptotic behavior of the sum: $$ \sum^n_{i=0} \begin{pmatrix} 2n \\ i \end{pmatrix} x^i y^{2n-i}$$ as $n\rightarrow\infty$. Here $x$, $y$ are complex numbers and I have ...
3
votes
1answer
121 views

Canonical divisor for conic bundles

Is there a general formula for the canonical divisor $K_X$ of a smooth conic bundle $X$? Motivation: for smooth hypersurfaces of degree $d$ in $\mathbb{P}^n$, $K_X = \mathcal{O}_X(d-n-1)$. But ...
0
votes
0answers
26 views

Variance of sums of correlated variables when sampling without replacement?

Background Let $X_t$ be an alternating renewal process, a stochastic process on the state space {0, 1} where 0 = 'Broken' and 1 = 'Working'. Let $U$ be the cumulative sojourn working during an ...
15
votes
0answers
187 views

Are there periodicity phenomena in manifold topology with odd period?

The study of $n$-manifolds has some well-known periodicities in $n$ with period a power of $2$: $n \bmod 2$ is important. Poincaré duality implies that odd-dimensional compact oriented manifolds ...

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