# All Questions

47 views

### calculating the Hilbert polynomial of a scheme given its primary decomposition

Given a scheme $X$ in $\mathbb{P}^n$, let $I_X$ be its, saturated, associated ideal. Suppose that a primary decomposition of this ideal is given by $$I_X =I_1 \cap \ldots \cap I_2$$ I was ...
408 views

### A letter from J. P. Serre

Which is the letter where J. P. Serre present "Analogues Kählériens de certaines conjectures de Weil" to Weil?
595 views

### If there is a dense geodesic, are almost all geodesics equidistributed? Dense?

Let $M$ be a complete finite volume Riemannian manifold and $\gamma : \mathbb{R}^{\geq 0} \to M$ a geodesic. Suppose that $\mathrm{im}(\gamma)$ is dense. Is it equidistributed in the Riemannian ...
264 views

### Time-line until the publicaton of Weil of “Numbers of solutions of equations in finite fields”

In "On the history of the Weil Conjectures" Dieudonné says: "Appropriately enough, the story, as with so many problems in number theory, begins with Gauss...". C. F. Gauss, Disquisitiones ...
118 views

61 views

### Generic path in the space of vector fields on the orientable surface

Who knows, does a theorem of such form exist: Any one-parameter family of vector fields on the orientable surface may be slightly perturbed such that 1) all fields in the family except finite number ...
238 views

### Rational structures on the flag variety over a finite field

Some Notions A variety over a field is defined to be a scheme of finite type over this field. An $\mathbb{F}_q$-rational structure of an $\bar{\mathbb{F}}_q$-variety $V$ is a $\mathbb{F}_q$-variety ...
173 views

### Tools for Removing Radicals from Equations

I am currently doing some investigations on Sylvester's 4 Point Problem Probability of 4 Points being in Convex Configuration and repeatedly face the problem of solving equations between sums of ...
143 views

### Integrals of representations over geodesics

Let $G$ be a compact, connected Lie group and $\rho$ any of its irreducible, unitary representations. If $\gamma:S^1\to G$ is an injective homomorphism (a periodic geodesic passing through the ...
13 views

### Approximation Hardness difference

What is the difference between a $n^{\epsilon}$ and $n^{1-\epsilon}$ bound on hardness of approximation? To be more specific, approximating the chromatic number is both $n^{\epsilon}$ and ...
79 views

### Mumford-Ramanujam examples in characteristic p

For a compact Riemann surface $B$ of genus $\geq 2$, it is a consequence of the Narasimhan-Seshadri theorem that there exist rank-$2$ vector bundles $E \to B$ of degree zero, all of whose symmetric ...
99 views

### Perfectness of the Jacobian of a curve

Let $C$ be a smooth projective curve over a field $K$ of characteristic $0$ (but not necessarily algebraically closed). Let $\mathcal{L}$ be a line bundle on $C$ of degree $0$. Fix an integer ...
68 views

The motivation to this question can be found in: About equivalent statements of the Birch and Swinnerton-Dyer Conjecture My question is about the last equivalences: $\mathrm{ord}_{s=1} L(E/K,s) = ... 0answers 126 views ### Alternative definition of a category [on hold] It is usual to define a (small) category$C$as consisting, among other things, as: a set of objects$|C|$; and, for each pair of objects$X$and$Y$, a set of morphims$C(X, Y)$. Now, since the ... 0answers 88 views ### book suggestion in fourier analysis and differential topology [on hold] I am at present following Vinberg and Onischik's Lie Groups and Algebraic Groups and I find it a fantastic book with theory developed through a series of problems left to the reader. I would like to ... 0answers 19 views ### Explicit construction of transition semigroup from generator for completely independent spin system (Feller process) As an example of how to obtain the transition semigroup from the probability generator for a Feller process, I am looking at the easiest spin system, namely with all sites independent. Notationwise, I ... 1answer 122 views +50 ### A question on involutions on the Lie algebra of vector fields Edite According to the essential comment of Ian Agol I revise the question as follows For a smooth manifold$M$, is there a non identity involution$\theta$on the lie algebra$\chi^{\infty}(M)$... 0answers 75 views ### Help with extension of f (mentioned below) to f: Zp -> Zp ,continuous function [on hold] This is a (different version to) question from Serre 'A Course in Arithmetic'.Let p be an odd prime number.$\forall n\geq 1$(n positive integer),$f$is defined by: $$f(n)=(-1)^n\prod_{1\le k\le n ... 1answer 166 views ### Constructing a “geometric” model structure on Cat by localizing the “categorical” model structure Let \text{Cat} be the category of (small) categories and functors. There is a "categorical" (also called "canonical" or "folk") model structure on \text{Cat} in which the weak equivalences are the ... 2answers 69 views ### Criterion for deloopable based map Is there a criterion for a based map f:G\to H between deloopable pointed spaces to be deloopable, i.e., that there is a based map g:X\to Y between path-connected pointed spaces such that G\simeq ... 3answers 207 views ### question about the induced homomorphism of etale fundamental groups Background/Setup For any connected scheme S, let \text{FEt}_S denote the category of finite etale S-schemes. Let f : X\rightarrow Y be a morphism of connected schemes, then for any finite ... 2answers 140 views ### Borel Sets in Sacks Generic Extension Let \mathbb{S} denote Sacks forcing. This is forcing with perfect trees or equivalently forcing with uncountable Borel subsets of {}^\omega 2 with the relation \subseteq. Let G \subseteq ... 0answers 91 views ### When is the earliest large prime gap also the latest large prime gap? Suppose one finds the earliest prime gap of at least a certain size g, so that p_{n+1}-p_n=g and n is the smallest index for which the gap is as big as g. Now consider the relative size of ... 2answers 122 views ### Expectation of a generalization of Dirichlet distribution For the standard Dirichlet, the expectation of X_i is \alpha_i/\alpha_0, where \alpha_0 = \sum_i \alpha_i [http://en.wikipedia.org/wiki/Dirichlet_distribution]. I am considering the following ... 2answers 154 views ### elementwise functions of positive definite matrix The fact that the Schur (that is, element wise) product of two positive definite (symmetric) matrices is positive definite immediately implies (using the convexity of the positive semi definite cone) ... 0answers 24 views ### Expressing the superposition of two cubic bezier splines as a cubic bezier spline? [on hold] To be clear, I'm not a mathematician, but a programmer. I'm trying to find an algorithm, and I'll try to be clear about the problem and its constraints. Please let me know if I need to provide more ... 1answer 85 views ### Symmetric invariants of a Schur Module Let V\cong\mathbb C^n be a complex vector space of dimension n. Let \lambda\in\mathbb Z^r be a generalized integer partition \lambda_1\ge\cdots\ge\lambda_r with r\le n. Denote by \mathbb ... 3answers 274 views ### How to find an integer set, s.t. the sums of at most 3 elements are all distinct? How to find a set A \subset \mathbb{N} such that any sum of at most three Elements a_i \in A is different if at least one element in the sum is different. Example with |A|=3: Out of the set A ... 0answers 65 views ### why is this result about Gaussian analytic functions equivalent to the Crofton formula I am reading Zeros of Gaussian Analytic Functions by Mikhail Sodin and he gives an much-too-easy proof of density of zeros of a Gaussian Analytic function. Definition A Gaussian analytic function ... 1answer 163 views ### Inverse of a Borel surjection Let X and Y be standard Borel spaces, and let f:X\to Y be a surjective Borel map. Does there exist a Borel inverse of f, that is a Borel map g:Y\to X such that f\circ g = \mathrm{id}_Y. ... 0answers 37 views ### On C_0(\Omega)-module maps from L_\infty(\Omega,\mu) to L_q(\Omega,\nu) Let \Omega be a locally compact space, and \mu,\nu\in C_0(\Omega)^*. By H_{p,q}^{B} (resp. H_{p,q}^{C}) we denote the Banach space of continuous B(\Omega)-module (resp. C_0(\Omega)-module) ... 0answers 9 views ### How to estimate the covariance matrix if the unnormalized pdf is known but integral is intractable? [migrated] Assume a d-dimensional random vector x, whose unnormalized pdf is known as the product of N multivariate t-distribution:$$Pr(x)\propto\prod_{i=1}^nt_{\nu_i,\mu_i,\Sigma_i}(x)$$Is there any ... 1answer 363 views ### Is there a mistake in Vapnik's “Basic Lemma”? I have a concern about the "Basic Lemma" which Valdimir Vapnik states and proves in his 1998 book Statistical Learning Theory (ch. 14.3, pp. 574–76): It seems like a certain coefficient should have ... 1answer 272 views ### Why are Witten-Reshetikhin-Turaev invariants expected to be integral? A Witten-Reshetikhin-Turaev (WRT) Invariant \tau_{M,L}^G(\xi)\in\mathbb{C} is an invariant of closed oriented 3-manifold M containing a framed link L, where G is a simple Lie group, and \xi ... 0answers 190 views ### Associated prime ideals and local cohomology [on hold] Let M be an R-module such that \operatorname{Ass}(M/N) is a finite set for any submodule N of M. Show that 1. \operatorname{Ass}(M/r M)=\operatorname{Ass}(M/r^n M) for each natural n; 2. ... 1answer 94 views ### Vertex transitive and edge transitive and line graph How can we find the proof of the following statement: An undirected graph is edge transitive if and only if its line graph is vertex transitive. 0answers 65 views ### my question is about matrix [on hold] let A be an n*n matrix with real entries which of the following is correct? 1.if A^2=0, then A is diagonalisable over complex numbers. 2.if A^2=I, then A is diagonalisable over real numbers 3.if ... 0answers 90 views ### Calogero-Moser eigenfunction The folllowing function J(t_1,t_2,t_3,m,h)=[(1-e^{t_1-t_2})(1-e^{t_2-t_3})(1-e^{t_1-t_3})]^{-m/h} ... 1answer 219 views ### Generating finite groups Let G be a finite group possessing a generating set of order n \in \mathbb{N}. Let H \leq G and x_1, \dots, x_n \in G for which \langle H, x_1, \dots, x_n \rangle = G. Must there be h_1, ... 0answers 134 views ### Open problems in Federer's Geometric Measure Theory I wanted to know if the problems mentionned in this book are solved. More specifically, at some places, the author says that he doesn't know the answer, for example :"I do not know whether this ... 0answers 56 views ### How f is approximated, in the L^{p}- norm, by a function f+h whose Fourier transform is constant in some nbhd of the point? Fact.Suppose f\in L^{1}(\mathbb R), x_{0}\in \mathbb R, and \epsilon >0. Then there exists h\in L^{1}(\mathbb R) with \|h\|_{L^{1}}< \epsilon, such that$$\hat{h}(x)= ... 1answer 309 views ### Is the Manickam-Miklós-Singhi Conjecture solved? This arXiv paper is claimed to contain a proof for the MMS conjecture. But it seems that this manuscript is not yet peer reviewed by other mathematicians. I personally tried to follow the paper, but ... 0answers 46 views ### Differential equations [closed] For k > 0,x = x(t),y = y(t) Solve this system: \begin{array}{l} x\frac{{{d^2}x}}{{d{t^2}}} = k\frac{{dy}}{{dt}}\\ x\frac{{{d^2}y}}{{d{t^2}}} = - k\frac{{dx}}{{dt}} \end{array} 0answers 170 views ### p-adic etale cohomology Let$X$be a smooth projective scheme over$\mathbb{Z}_p$, with special fiber$X_s$over$\mathbb{F}_p$, generic fiber$X_{\eta}$over$\mathbb{Q}_p$, and geometric generic fiber$\bar{X_{\eta}}\$ over ...

15 30 50 per page