All Questions

-6
votes
0answers
80 views

smoothness of free boundary [closed]

For in $\mathbb{R}^n$, there is a an positive obstacle it has the expression $\phi(x) = \chi_{BR(0)} \cdot \max\{0,a(x)\}$, where $a(x)$ is an analytic function or smooth function on the whole of ...
-2
votes
0answers
28 views

Some regularity results of free boundary quesions for a special case [on hold]

In $R^n$, there is an obstacle $\phi \in C_0(R^n)$, and $\phi$ is analytic on its support and has analytic continuation in an open set containing its support. Then I just want to solve the following ...
0
votes
0answers
14 views

Approximate rank of the set formed by all delayed replicas of a bandlimited signals between 0 and T

My question is given a complex-valued signal with a certain delay $s(t-\tau)$ for which we sample $N$ isntants: $$\mathbf{s(\tau)}=\left[s(0-\tau),\ldots,s\left(\frac{N-1}{f_s}-\tau\right)\right]^T$$ ...
4
votes
1answer
174 views

Panning for gold nuggets: a type of isoperimetric problem

Let $C$ be a unit-radius circle in the plane. Suppose you have a total length $L$ of string available, and your task is to connect chords of $C$ using no more than $L$ of string to minimize the ...
3
votes
1answer
108 views

Gaussian Curvature of Exponentiated 2-Planes

Consider a Riemannian manifold $M$ with sectional curvatures $K\ge 0$ and let $\Pi$ be a 2-plane in the tangent space of $M$ at a point $p$. In a small enough neighborhood $U$ of 0 the exponential map ...
3
votes
0answers
152 views

A question on the size of an admissible ordinal

Let $\mathbf{L}_{\varsigma}$ be the level of ordinal $\varsigma$ of Gödel's constructible universe $\mathbf{L}$. Let $\Sigma_{3}$-KP be Kripke-Platek set theory with infinity and ...
-4
votes
0answers
52 views

Partial differential equation [closed]

I have been trying to solve this equation for a while. Is there anyone who can help me to solve this? Any comments appreciated. $$\frac1{r}\frac\partial{\partial r}\left(r \frac{\partial E}{\partial ...
-3
votes
0answers
30 views

Necessary Condition For Ellipticity [closed]

What is the ellipticity condition for a higher order linear differential equations in two complex variables?
1
vote
0answers
91 views

Infinite matrices with a finite number of non-zero values on each row

The little bit of literature on infinite matrices I've been able to find studies a general setting in which the theory is hindered by constantly having to worry about whether or not various infinite ...
9
votes
1answer
303 views
+50

Between compact and locally uniform: What is the name of this convergence?

Let $X$ be a topological space, $(Y,d)$ a metric space, $f\in Y^X$, and $(f_n)$ a sequence in $Y^X$ with the following property: For every $x_0\in X$ and every $\varepsilon>0$, there exist a ...
-6
votes
0answers
64 views

How can I prove that [closed]

Let we have the space C[a,b] ( the space of all functions that are continuous on closed interval [a,b] ) And we have two norms on this space ||X||1=max|x(t)| such that t belongs to [a,b] ...
-3
votes
0answers
92 views

Decidability of a language [closed]

L = {M,w | Turing Machine M on input w revisits the left-most tape cell at least once after initially leaving it }. Is L decidable?
-1
votes
1answer
224 views

Does anyone know of theorems/lemmas that are named after poets/authors/musicians? [closed]

This is a soft question, and if anybody knows of lemmas/theorems, that are used in mathematics, but are named in an unusual way. The lemmas/theorems could be named after poets/philosophers/musicians. ...
8
votes
2answers
255 views

What is the BRST-anti-BRST formalism?

What is the BRST-anti-BRST formalism? Is the Sp(2) doublet the ghost, antighost pair? Introductory accounts of this subject seem to be hard to find. I would appreciate a reference for someone who ...
1
vote
2answers
263 views

How to prove that a kernel is positive definite?

For example, how to prove $\forall(x,y)\in R^N\times R^N,K(x,y) = \displaystyle\frac{1}{1+\frac{||x - y||^2}{{\sigma}^2}}\\$ where $\sigma > 0$ is a parameter, is positive definite? I have tried to ...
-1
votes
0answers
33 views

Does $\sum_{n=1}^{\infty} f(z^n)$ converges locally uniformly on unit disk [migrated]

If $f(z)$ is analytic in the unit disk and $f(0)=0$ , show that $$f(z)+f(z^2)+\cdots f(z^n)\cdots $$ converges locally uniformly to an analytic function in the unit disk. I am thinking to apply ...
-5
votes
1answer
140 views

An axiomatic system with a set of constants that form a complete ordered field [closed]

I am developing a ZFC axiomatic system where together with the empty set, there is a singular (and huge) set of constants that are themselves sets and form a complete ordered field (cof) these ...
1
vote
0answers
25 views

Breaking down the co power of a topological space

Consider a compact, Hausdorff topological space which is homeomorphic to its own co-power over an index set $I$, so $X \cong \prod_{i \in I } X$. Is there necessarily another topological space, which ...
2
votes
1answer
203 views

Extensions in parabolic Hölder spaces

Let $\alpha\in ]0,1[,k\in\mathbb{N}.$Let $\Omega$ be a open and bounded subset or $\mathbb{R}^n$ of class $C^{k+\alpha}$. As one could find in G.M. Troianello "Elliptic Differential Equations and ...
0
votes
1answer
171 views

The number of solutions of a Diophantine equation [on hold]

Is $\lim_{n \rightarrow \infty} |\{(x,y) \in \mathbb{Q}(\zeta_n)^2 : y^3 = x^3 + x + 1\}| < \infty ?$ where $\zeta_n$ is a primitive $n$-th root of unity. That is, I am asking whether the number ...
7
votes
2answers
219 views

Peano arithmetic vs. fast-growing hierarchy with pathological fundamental sequences

Fundamental sequence for a countable limit ordinal $\alpha$ is an increasing sequence $\{\alpha[i]\}$ of ordinals of length $\omega$ such that $\lim_{i\rightarrow\omega}\alpha[i]=\alpha$. There are ...
6
votes
0answers
133 views

Does every commutative $*$-algebra of operators on a prehilbert space have a character?

My question can be equivalently stated as follows: Let $A$ be a complex commutative algebra with involution, and assume there exists a non-zero homomorphism $\pi:A\to L(V)$ to the algebra of ...
5
votes
0answers
152 views

Gompf's invariant of $2$-plane fields

I am interested in low dimensional contact topology. These days I read "Handlebody construction of Stein surfaces" written by R. E. Gompf, and study an invariant $\theta (\xi)$. This invariant is ...
8
votes
2answers
355 views

Infected square

I saw the following problem in Mathematical Puzzles from Peter Winkler (very good book, by the way): imagine you infect k cases of a chessboard nxn and the infection spreads to a case if it has at ...
3
votes
1answer
117 views

Immersed versus embedded surfaces representing a same homology class

I am working on the Gromov norm of submanifolds in the total space E of surface bundles over surfaces. So I am interested in knowing the minimal genus of a surface representing a given homology class ...
2
votes
0answers
154 views

Diophantine equations over cyclotomic fields

Let $\mathbb{Q}^{\text{ab}}$ be the compositum of all finite abelian extensions of $\mathbb{Q}$. Explicitly, $\mathbb{Q}^{\text{ab}}$ is the field obtained from $\mathbb{Q}$ by adjoining all roots of ...
0
votes
0answers
42 views

Hyperquotient singularities and Newton polyhedra

Following the same notation as M. Reid "Young person's guide to Canonical Singularities": Suppose that $Y\subseteq \mathbb{A}^{n+1}_\mathbb{C}$ is a smooth affine hypersurface defined by ...
-1
votes
0answers
49 views

Probability: short circuiting amongst recycled batteries [closed]

I am a student at University of Illinois with some batteries to recycle. The student union collects batteries, but requires the terminals to be taped. I think this makes a lot of sense for 9 volt ...
11
votes
2answers
643 views

from a circle to higher spheres

Question: Is there a group $G$ and a CW-complex $X$ such that 1) $X$ is homotopy equivalent to the circle $S^{1}$. 2) $G$ acts on $X$ 3) the space of fixed points $X^{G}$ is weakly equivalent to ...
-3
votes
3answers
257 views

Determinant of matrix from set {-1, 1}

Let $A \in \mathbb{R}^{11 \times 11}$ and it's elements are form set $\{ -1,1 \}$. $\mathbb{P}(-1) = \mathbb{P}(1) = 0.5$. What is a probability to get such a matrix, that $\det A > 4000$? I have ...
3
votes
0answers
42 views

Topological pressure for subshifts on a countable alphabet

Apologies for asking two similar questions within a week of each other, I had hoped that asking a finite alphabet version of this question would lead to enlightenment but unfortunately it didn't. ...
-1
votes
2answers
107 views

Converting p-adic to decimal [closed]

Is it possible to convert irrational p-adic numbers to a standard number? Rationals and negative rationals are relatively straightforward, but is there a way to know that for instance $\ldots ...
10
votes
2answers
424 views

On a proposition in Hartshorne's paper “Ample vector bundles on curves”

In Prop. 4.1, p. 87 of the article "Ample vector bundles on curves" (Nagoya Math. J. 43 [1971], 73--89), R. Hartshorne states the following: Let $A$ be an abelian variety [over an alg. closed field ...
-7
votes
0answers
91 views

off-topic government question [closed]

We are estimating the spares requirement for a radar power supply. The power supply was designed with a mean (μ) life of 6500 hours. The standard deviation (σ) determined from testing is 750 hours. ...
10
votes
0answers
111 views

Polytopes with few vertices and few facets

I recently realized that, for fixed $\alpha$ and $\beta$, the number of (combinatorial types of) $d$-polytopes with $\leq d+1+\alpha$ vertices and $\leq d+1+\beta$ facets is bounded by a constant that ...
4
votes
1answer
232 views

When is a `1-form' with continuous coefficients exact?

Let $\Omega$ be a convex, bounded open subset of $\mathbb{R}^d$, and let $C^1(\bar \Omega)$ be usual space of continuous functions on $\bar \Omega$ which are $C^1$ in $\Omega$ and whose partials in ...
0
votes
0answers
26 views

How to find out if a given sequence of orthogonal polynomials belongs to the Askey scheme?

I am studying some classes of orthogonal polynomials and want to find out which of them belong to the Askey scheme. To give a simple example consider the polynomials $${p_n}(x,r) = \sum\limits_{k = ...
1
vote
0answers
65 views

About the reduceness of the commuting scheme associated with a symmetric pair

my question is the following one: Let $G$ be a connected reductive algebraic group over the field of complex numbers, and let $V$ be a linear representation of $G$ obtained as the isotropy ...
0
votes
1answer
144 views

Orthogonal projection

Let $G$ be an operator with compact resolvent on a Hilbert space $H$ such that $\ker G \neq \{0\}$. Further let $P$ be the orthogonal projection onto $\ker G$, and let $G_{0} := G+P$. My question is: ...
1
vote
1answer
26 views

Condition Number and CFL Condition in Finite difference Methods

when applying a Finite Difference scheme for an IVP, two factors come to mind when considering stability: One factor would be the condition number of the approximation operator. The other factor ...
4
votes
2answers
270 views

What is the best reference for Spectral theory?

I'm studying Bernard Aupetit: A Primer on Spectral Theory but the textbook we are using is a little bit heavy going for me. Is there a best book to learn about these things? Thank you.
1
vote
0answers
52 views

Does this condition imply a polynomial is a product of linear factors

Let $\Lambda$ be a lattice (i.e. $\Lambda \simeq \mathbb{Z}^n$) with a positive subcone $\Lambda^+$. Let $H: \Lambda^+ \rightarrow \mathbb{C}$ be a function such that $\forall\mu \in \Lambda^+$, ...
3
votes
0answers
73 views

Oscillatory integral moments of $L(\frac{1}{2} + it, f \times f)$

Understanding moments and subconvexity bounds for $L$-functions is a big topic with a lot of activity. I'm currently looking at a related problem, bounding $$ \int_0^T L\left(\tfrac{1}{2} + it, f ...
1
vote
0answers
55 views

Lower periodic subsets of groups and semigroups

Suppose that $A$ and $B$ are subsets of a group or semigroup. We call $A$ left upper [resp. lower] $B$-periodic if $BA\subseteq A$ [resp. $A\subseteq BA$]. If $A$ is both left upper and lower ...
-3
votes
0answers
57 views

Game theory question Folk Theorem [closed]

I wonder what is the strategy is here.. I have calculated the potential result start from p1 choose C and p2 choose D at first time, and then they both confess. However someone points this is not the ...
-3
votes
0answers
56 views

Verification of Gauss Bonnet Theorem on Beltrami pseudosphere and bent sphere patches [closed]

Given that boundary geodesic curvature k_g and Gauss curvature K are constant, patch area = A and perimeter length = p. $ K\, A + k_g\, p = 2 \pi $ For a flat circle patch $ k_g= 1/R, $ $ ...
2
votes
1answer
127 views

Graph automorphism that swaps two pairs of nodes

Suppose we have two automorphisms on a graph $G$ such that each one swaps a separate pairs of vertices. Is it possible to construct (or prove the existence of) a third automorphism that swaps both ...
9
votes
1answer
195 views

Subquotients in the Verma filtration on Verma modules

Let $\lambda$ be a dominant integral weight of $\mathfrak g$, a finite-dimensional reductive Lie algebra over $\mathbb C$. Let $M(w\cdot \lambda)$ denote the Verma module with high weight $w\cdot ...
2
votes
1answer
68 views

Standard names and methods for this type of fitting minimization

In material science research, we have come across the following type of problem. Given a m by n matrix A, a m vector b, and error tolerance $\varepsilon$, we want to do this minimization $$\eqalign{ ...
2
votes
1answer
306 views

Hopf-algebras in associative ring spectra

I'm interested in a definition of cocommutative Hopf-algebra objects in the $\infty$-category of associative (read: $A_\infty$) ring spectra. One thought I had was to think of cocommutative ...

15 30 50 per page