Most active questions
785 questions from the last 30 days
3
votes
0
answers
44
views
Is rank of the length spectrum of a closed negatively curved surface/manifold infinite?
Suppose that $(S,\mathfrak{g})$ is a closed negatively curved Riemannian surface (or more generally a manifold). Negative curvature guarantees that the non-trivial conjugacy classes $\text{conj}(\pi_1(...
- 119
0
votes
0
answers
47
views
Fractal dimension using wavelets [closed]
I'm trying to estimate the fractal dimension of a function.
I created the log(energies) Vs log(scales) plot and I'm computing the Fractal Dimension (D) from the slope using the relation
$$
\alpha = -...
1
vote
0
answers
112
views
Zariski Connectedness Theorem: From Analytic & Topological Viewpoint
Let $p:Y \to X$ be a proper, flat (see later why) surjective map between smooth connected complex varieties $Y,X$, esp. $X$ unibranch. Assume that there exist a Zariski open (esp. dense) $U \subset X$ ...
- 6,048
1
vote
0
answers
44
views
Lower bound for restricted sumset in ordered groups
Recently in The restricted sumsets in finite abelian groups it is proved that
Suppose that $k \geq 2$ and $A$ is a non-empty subset of a finite abelian
group $G$ with $|G| > 1$. Then the ...
1
vote
0
answers
100
views
Unitary representations of Fuchsian and Kleinian groups
Let $\Gamma$ be a discrete group that is either Fuchsian ($\Gamma \subseteq \text{PSL}(2,\mathbb R)$) or Kleinian ($\Gamma \subseteq \text{PSL}(2,\mathbb{C})$).
I have a unitary representationL
$$
\...
- 357
3
votes
0
answers
67
views
$(M_1\otimes M_2)\otimes_{A\otimes A} A\cong M_1\otimes_A M_2$ in HA
I apologize for this naive question, I believe it's somewhere in HA but I just can't find it.
For symmetric monoidal category $C$, consider $A\in CAlg(C)$, and $M,N\in Mod_A(C)$, we can formulate the ...
- 618
-3
votes
0
answers
76
views
Exercise generalizing (related to) Hölder's inequality
I came across this exercise and feel absolutely stuck:
Let $p, q, r \in (1, \infty]$ be such that $1/p + 1/q = 1 + 1/r$. Suppose that $F : \mathbb{R}^n \times \mathbb{R}^n \to \mathbb{R}$ satisfies ...
- 1
2
votes
1
answer
42
views
Integral hull of a polyhedron Q is polyhedron
Let $Q \subseteq \mathbb R^n$ be a rational polyhedron and let $Q_I=Convexhull(Q \cap \mathbb Z^n)$. By finite basis theorem, we have $Q=P+C$ for some rational polytope $P$ and finitely generated cone ...
- 31
-2
votes
0
answers
54
views
Density of squared bessel process
I was trying to find a transition density function for a squared Bessel process. In the book "Continuous martingale and Brownian motion" by Revuz and Yor, I find a Corollary on page 441 that ...
- 11
0
votes
0
answers
49
views
The relation between Hodge bundles with metric and polarized variation of Hodge structures
Recently I've been reading Simpson's paper "constructing variations of Hodge structure using Yang-Mills theory and applications to uniformization, 1988, JAMS". On page 898 he mentioned about ...
- 11
2
votes
0
answers
40
views
Lie algebra of Hamiltonian (1,0) vector fields on 4-manifold
I have encountered a certain Lie subalgebra of the Lie algebra of vector fields on a 4-manifold that is also a complex manifold, distinct from the well-known Lie algebra of holomorphic vector fields. ...
- 223
0
votes
0
answers
47
views
Maximize mixing in a 12 person dinner party [closed]
Is this question well posed? If not, can you improve it? If so, what is the solution?
I am holding a dinner party for 12 people. Their names are A, B,...L. The seats are numbered: 1, 2, ... 12. The ...
- 101
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 ...
0
votes
0
answers
32
views
question about some algebraic simplifications performed as we solve differential equations with Laplace transform [migrated]
I am trying to follow this discussion of Laplace transforms on youtube:
https://www.youtube.com/watch?v=ofvkZXgbIxE&t=610s
The relevant portion is 10 minutes in to the video.
There is some algebra ...
- 101
0
votes
1
answer
96
views
A question on finite Fourier series
Let $\mathcal F(N)$ denote the space of finite Fourier series up to frequency $N > 0$, i.e. $f\in \mathcal F(N)$ if and only if it can be written as
$$f(x) = \sum_{k=0}^N a_k\cos(kx+\theta_k)$$
for ...
- 71
0
votes
0
answers
85
views
Is there a symbolic computation program that can deal with differential forms, Stokes theorems, the Hodge * operator, etc
I am looking at a messy series of computations of integrals of differential forms on manifolds with boundary, involving repeated application of Stokes' theorem, and also involving the Hodge * operator....
- 1
0
votes
0
answers
67
views
$L_1$ norm of $f\in L^1(\mathbb{R}^n)$ compactly supported and its change of variable
Let $M\in\mathbb{R}^{n\times n}$ be an invertible matrix, denote its induced linear map on $\mathbb{R}^n$ also by $M$, and let $f\in L^1(\mathbb{R}^n)$ be compactly supported.
I am wondering if we can ...
- 91
3
votes
0
answers
36
views
Proving a proposition about the provability logic GL without using its completeness theorem
Let $GL$ be the provability logic containing the axioms $K := \Box (\varphi\to \psi)\to (\Box \varphi\to \Box \psi)$ and $L := \Box(\Box \varphi \to \varphi)\to \Box \varphi$, along with the ...
-3
votes
0
answers
33
views
Bayesian Inference for Parameters Estimation in ARMA Model [closed]
In the usual sense, Maximum Likelihood Estimation is the common method for Parameter estimation in ARMA(p,q) model.
If I am looking to estimate parameters for ARMA(p,q) with Bayesian Inference, how ...
- 1
1
vote
0
answers
36
views
induced module of hyperoctahedral group
Let $H$ be the subgroup of the symmetric group $\mathfrak{S}_n$. Let $W_n$ be the group algebra of the hyperoctahedral group $\mathbb{Z}/2\mathbb{Z} \wr \mathfrak{S}_n$.The induced module $M:=\mathrm{...
- 179
0
votes
0
answers
61
views
Is the new method used by the GIMPS project applicable to non-Mersenne primes?
For years, there was a simple reason why the largest known prime is of the form $2^{p}-1$: We had the Lucas-Lehmer test which was specific to Mersenne numbers, and faster than all other known methods.
...
- 233
0
votes
0
answers
36
views
Contribution of Fisher information near jump points in convolved probability distributions
I am trying to compute the contribution to the Fisher information from jump points $b_i(\theta)$ in the convolved function $f(x; \theta)$ with respect to the parameter $\theta$. I am unsure whether it ...
- 99
1
vote
0
answers
103
views
Prove or disprove that $|(1/\zeta)^{(n)}(x)| \leq \frac{n!}{(x-\frac{1}{2})}$ for all real $x>1$
$|(1/\zeta)^{(n)}(x)| \leq \frac{n!}{(x-\frac{1}{2})}$ for all real $x>1$.
I had this conjecture for a long time. I tried various methods and techniques but they all failed. It might also be wrong ...
- 178
1
vote
0
answers
44
views
Differential system of equations I would like to simplify
I have 2 functions of time $f(t),g(t)$ and a condition for the time-derivative of a third function $h(t)$, say $$\dot{h}(t)=\dot{g}(t)\cos{f(t)},$$ so $h$ is defined provided a value for $h(0)$ (as $h(...
- 11
1
vote
0
answers
58
views
'Invert' perturbed vorticity equation to forced Euler system
Given the vorticity form of the Euler equations in $2D$ with stream function $\psi$
\begin{align}
\omega_t + \nabla^\perp \psi \cdot \nabla\omega &= 0 \\
\Delta \psi = \omega
\end{align}
we know ...
- 255
2
votes
0
answers
35
views
Maximum number of connected components of surfaces in three dimensions, what is known?
Part of Hilbert's 16th problem is:
It seems to me that a thorough investigation of the relative positions of the upper bound for separate branches is of great interest, and similarly the ...
- 21
1
vote
0
answers
29
views
Factoring semiprimes via sum of two squares? [migrated]
The following thoughts came into my head after watching Grant Sanderson's JBPM award lecture here, in which he discusses the fact that we can quickly factor 3599 by noticing it can be written as (60-1)...
- 61
1
vote
0
answers
32
views
Balanced cocircuit cover
Are there studies on matroids which can be covered by $r$ cocircuits ($r$ is the rank of the matroid), so each element is covered by a small number of times?
For example, it is known graphic matroids ...
- 613
-1
votes
0
answers
46
views
Tightest decreasing majorant
I had asked this question here but received no answer.
Let $O$ be an operator that maps sequences to sequences such that the elements of the sequence $O(a)$ are given by
$$\bigl(O(a)\bigr)_n ~{}={}~ \...
- 349
-3
votes
0
answers
28
views
Convergence of measures in the Lévy–Prokhorov metric and weak convergence of measures [closed]
How to prove that over R the convergence of measures in the Levi-Prokhorov metric is equivalent to the weak convergence of measures
- 1
0
votes
0
answers
42
views
Markov chain on the real line: Numerical methods for evaluating the stationary distribution
Consider a Markov chain on the real line with transition probabilities
$$
p(x_0,x)=\mathbf 1_{\{x\geq x_0+\alpha\,\cup\,x\leq x_0-\beta\}}\phi(x)+\delta(x-x_0)\left(\Phi(x_0+\alpha)-\Phi(x_0-\beta)\...
3
votes
0
answers
31
views
Disjoint touching bodies of constant width
Let $F$ and $F_1,\ldots,F_n$ be bodies of constant width 1 in $\mathbb{R}^d$ such that $F_1,\ldots,F_n$ are pairwise disjoint and all intersect non-trivially (i.e. in at least one point) with $F$. ...
- 199
0
votes
0
answers
91
views
How to show a point is a weak* -weak continuous for the identity map on $X_1^*$ or on $X_1^{**}$?
I am trying to understand the Remark 3.2 mentioned in the paper titled as "On Weak*
-Extreme Points in Banach Spaces" written by S. Dutta and T. S. S. R. K. Rao (http://library.isical.ac.in:...
- 113
0
votes
0
answers
89
views
Extend algebraic morphism to a compactification with normal crossing boundary
Suppose $X$ and $Y$ are smooth algebraic variety over a char $0$ field $k$, and $f:X\to Y$ a morphism. I want to ask whether there exists compactifications $\bar X$ and $\bar Y$ such that $\bar X\...
- 785
-2
votes
0
answers
34
views
Convergence of $ \vec{x_{n+1}} = A^{-1} f(\vec{x_{n}},\vec{y_{n}}), \:\:\: \vec{y_{n+1}} = A^{-1} g(\vec{x_{n}},\vec{y_{n}}) $ [closed]
I have two systems
$$ A \vec{x} = f(\vec{x}, \vec{y}), \:\:\: A \vec{y} = g(\vec{x}, \vec{y}) $$
Both have the same constant, square, invertible matrix $A$. I implemented an iterative algorithm with ...
- 97
0
votes
0
answers
37
views
Maximise norm over the boundary of a convex set
Let $K\subset \mathbb R^2$ be compact, convex and connected. What is the know numerical scheme to find the extremal points of $K$?
Denote by $\partial K$ the collection of all extremal points of $K$. ...
- 1,399
1
vote
0
answers
50
views
Insights on non-commutative operator families on rational functions satisfying the braid relation
I am studying the article "Symmetrization operators in polynomial rings" by A. Lascoux and M.-P. Schützenberger (MSN). Specifically, I am trying to prove the following claim involving ...
- 141
1
vote
1
answer
27
views
Surjective hash functions $h:\{0,1\}^* \to \{0,1\}^{2n}$ with avalanche effect
Motivation. In computer science, hash functions are maps that convert binary strings of arbitrary length to a fixed-length binary string. In symbols, we have a map $h:\{0,1\}^* \to \{0,1\}^n$ for some ...
- 48.9k
0
votes
0
answers
67
views
Copy and repeat or copy and sum integer coefficients
Let
$$
\ell(n) = \left\lfloor\log_2 n\right\rfloor.
$$
Let $T(n,k)$ be an integer coefficients with row length $f(n)$ (number of zeros in the binary expansion of $n$ plus $2$ for $n>0$ with $f(0)=1$...
- 4,938
3
votes
0
answers
28
views
Given a metric space $X$, is there a natural way to view the quasi-isometry group $QI(X)$ as a topological group?
Given a metric space $(X,d)$, we define $QI(X)$ as the set of quasi-isometries $f : X \to X$, modulo the equivalence relation
$$
f \sim g \ \ \ \ \text{ if and only if } \ \ \ \sup_{x \in X} \ d(f(x)...
- 639
-2
votes
0
answers
82
views
Every well-ordered set is isomorphic to an unique ordinal? [closed]
Every well-ordered set $W$ is isomorphic to a unique ordinal
Proof: We start with some well-ordered set $W$. We attempt to construct a bijective map from $W$. Let us consider this class
$$\{(x, \...
- 1
2
votes
0
answers
49
views
Are maps between cohomology of homogeneous vector bundles morphisms of representations?
Let $X = G/P$ a rational homogeneous variety, e.g. a grassmannian. Consider a short exact sequence $$ 0 \longrightarrow E_1 \longrightarrow E_2 \longrightarrow E_3 \longrightarrow 0$$
where $E_i$ are ...
- 41
0
votes
0
answers
38
views
Bounding the error of a truncated moment problem
Let $\{x_{i}\}_{i=1}^{\infty}$ be a non-increasing sequence of non-negative real numbers, and let $\{y_{j}\}_{j=1}^{B}$ be a non-increasing sequence of non-negative real numbers, where $B$ is a finite ...
- 433
1
vote
0
answers
58
views
Tiling with one of each 3D shape
Encouraged by the positive solutions to my question,
Tiling with one of each shape,
I'd like to pose the $\mathbb{R}^3$ equivalent:
Q. Is there a tiling of $\mathbb{R}^3$ by (bounded) polyhedra, one ...
- 151k
1
vote
0
answers
38
views
Metric entropy of an ellipsoid
Let $B^d_2$ denote the unit ball of $\ell_2^d$ and let $T$ be an invertible linear map.
Consider the function
$$
H(T) := \log M(TB_2^d, B_2^d),
$$
which is the packing entropy for $TB_2^d$ by $B_2^d$....
- 380
1
vote
0
answers
33
views
Martingale decomposition in Aldous' famous 1997 paper
I was reading Aldous' famous 1997 paper (Aldous, David. "Brownian excursions, critical random graphs and the multiplicative coalescent." The Annals of Probability (1997): 812-854.)
In his ...
- 111
3
votes
0
answers
28
views
Avoiding class/unit group computation when computing $p$-Selmer groups
Let $K$ be a number field, $S$ be a finite set of places of $K$, and $K(S,p)$ be the $p$-Selmer group of the $S$-integers of $K$, that is the set of nonzero elements of $K$ modulo $p$-th powers whose ...
0
votes
0
answers
53
views
Special determinant formula
Consider two column vectors $\textbf{a}$ and $\textbf{b}$ of length $k$ and $m$ respectively, $km$ variables denoted $y_{i,j}$ (i=1 to k, j=1 to m), and a quadratic form $\textbf{y}^{T}\mathbb{M}\...
- 419
1
vote
0
answers
39
views
Reference request - Fourier multiplier of vector valued function
I would like to understand the concept of multiplier for vector valued functions and find appropriate references for the multiplier theorems out there.
For instance say that we would like to express $\...
- 111
0
votes
0
answers
30
views
Question on the closed proper convex functions
I'm confused with the definition of the closed proper convex functions when reading the paper
https://people.orie.cornell.edu/aslewis/publications/00-dykstras.pdf
It appears that, when a function $f$ ...
- 1,399