Ordinary or partial differential equations. Delay differential equations, neutral equations, integro-differential equations. Well-posedness, asymptotic behavior, and related questions.

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Dealing with a Matrix ODE in integral form

Supose we have $v'(t) = A(t)v(t)+b(t),$ with $v(0)=0$ where $v(t),b(t) \in \mathbb{R}^n $, $A$ is a $n\times n$ real matrix and $t \in [0,1]$ Now, if A and b are discontinuous but integrable ...
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488 views

duality argument in PDE

Can anyone please explain the term 'duality argument', or the difference between this term and the weak formulation in PDE analysis? Or give some references? Occasionally I see this term appears in ...
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362 views

What is the Schauder estimate on usual Hölder space for parabolic type equations

What is the Schauder estimate on usual Holder space for parabolic type equations ?
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263 views

Rigorous results on the method of multiple scales

The method of multiple scales (Scholarpedia) is a technique used to obtain approximate solutions to differential equations, most commonly when some of the more standard approaches to perturbation ...
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115 views

The existence of the solution of $u_t+u_0u_x+u_{0x}u+u_{xxx}=0,u(x,0)=0$

Prove the existence of the solution of the Cauchy Problem: $$u_t+u_0u_x+u_{0x}u+u_{xxx}=0,u(x,0)=0$$ where$u_0\in C^{\infty}(R).u_0,u_{0x}\to 0,when |x|\to \infty$ AS Robert Bryant's comment,$u=0$ is ...
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99 views

The existence of the solution of the perturbed KdV Equation(semi-group operator)

Consider the perturbed KdV Equation$$u_t-6uu_x+u_{xxx}=\epsilon u,u(x,0)=f(x)$$where $f(x)=v(x,0)$,$v(x,t)$ is a soliton solution.$u$ satisfies the condition$u\to 0 $when $|x|\to\infty$ I want to use ...
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3answers
829 views

book on PDE on manifolds

let $M$ be a Riemannian manifold and $\alpha$ be any some unknown form on $M$. I am interested in solutions or some references of the equation of type $(d + \delta) \alpha = 0$ where $\delta$ is the ...
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171 views

second order operator with real coefficients and not locally solvable

This question is a follow up of the following answer I posted recently: Counterexamples in PDE Is there a second order partial differential operator with real coefficients which are not solvable in ...
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0answers
349 views

Optimal transport warping implementation in Matlab

I am implementing the paper "Optimal Mass Transport for Registration and Warping", my goal being to put it online as I just cannot find any eulerian mass transportation code online and this would be ...
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1answer
164 views

Constructing an example of Hamiltonian flow

I have this Hamiltonian flow generated by $$ h(x, \xi ) = V(x) + \sqrt{\xi ^2 + 1}, \quad x, \xi \in \mathbb{R}^3, $$ so the defining equations are ...
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1answer
264 views

Solution to a second order PDE

Looking for a general solution to the following second-order PDE, where the unknown is a function $f(x_1, x_2)$ of two variables: $ 0=a^2f+a^2x_1{\partial f\over \partial x_1}+b^2x_2{\partial f\over ...
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1answer
144 views

Differential finiteness of power series with hypergeometric coefficients

Let $f$ be a formal (or convergent near the origin, as you wish) power series with variables $x_1$, ... , $x_n$ and complex coefficients. $$ f = \sum_I f_I \mathbf x^I $$ This power series is said to ...
3
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1answer
270 views

Moving under the influence of a vector field

I have a continuously varying vector field $v(p)$ on $\mathbb{R}^2$, and a particle at point $p$ in the plane that can move in a direction $u(p)$ as long as $u(p)$ is turned at most $\pi/2$ left of ...
3
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2answers
261 views

delay differential equation

I'm looking for exact solutions, if such exist, for the following non-linear delay differential equation (DDE): $ y_x(x) = A y(x-1)^a $ where $ 0 < a < 1 $ and $ A > 0 $ are given ...
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1answer
181 views

ODE in symmetric definite positive matrices

It is easy to solve the ODE: $\frac {dx}{dt} = a - b x^2$ with $x(0)=0$, $a>0$, and $b>0$, indeed all one has to do is write $dt = \frac {dx}{a-bx^2} = \frac 1 {2\sqrt a}(\frac {dx}{\sqrt ...
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1answer
92 views

Are the real components of s-roots subharmonic?

Suppose $f(z)$ is an analytic function on a domain $D$ which maps negative axis to negative axis. For $s>1$ consider the function $$u(z)=\Re \sqrt[s]{f(z)}$$ with the branch cut along the negative ...
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73 views

Semi implicit DAE integration using an implicit Runge Kutta scheme

I'm looking for some references regarding integration of DAEs in the form $M(t) \frac{dy}{dt} + G(y(t),t) + f(t) = 0, \quad y \in R^n, M(t) \in R^{nxn}$ using a high order implicit Runge Kutta ...
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174 views

Optimal Sobolev Inequality

Recall the Optimal Sobolev Inequality: Let $(M^n,g)$ be a smooth, compact Riemannian $n (\geq 3)$ manifold with $\hbox{inj}_g\geq i_0, |Ric(g)|\leq \Lambda g$. Let ...
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158 views

A priori estimate for Yamabe solution

We know Schoen's compactness on Yamabe problem: Let $(M^n,g)$ be a smooth compact Riemannian manifold of dimension $3\leq n\leq 24$ without boundary. Denote $\Phi$ to be the full set of arbitrary ...
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1answer
170 views

A priori estimate of elliptic complex

On a compact Riemannian maniflod $(M,g)$, for an elliptic complex $\mathcal{C}_0\overset{L_1}{\longrightarrow}\mathcal{C}_1\overset{L_2}{\longrightarrow}\mathcal{C}_2$ where $L_1$ and $L_2$ are ...
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1answer
177 views

topological equivalence of ODEs

Let $n$ be a non-negative integer. $\;\;$ Let $\: f : \mathbb{R}^n \to \mathbb{R}^n \:$ and $\: g : \mathbb{R}^n \to \mathbb{R}^n \:$ be Lipschitz. Define the relation $\stackrel{f}{\sim}$ on ...
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2answers
490 views

The spectrum of Schrodinger Equation [closed]

Consider the Schrodinger Equation$$\psi_{xx}-(u-\lambda)\psi=0$$ with the condition 1.when $x\to|\infty|,u\to0,u_x\to0$ 2.$\psi|_{x\to \infty}=0$ How to prove that spectrums are real? ...
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1answer
295 views

Lie algebra “generated” by matrix-valued curve?

Let $A(t)$ be a $n\times n$-matrix-valued continuous (plus possibly other niceness conditions; see below) curve, with the matrix entries being complex in general. If I am not mistaken, $A(t)$ ...
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1answer
136 views

dilation operator green function

how can i solve $ -ixDG(x,s)-iG(x,s)/2= \delta ( \frac{x}{s}-1) $ i do not know , since it is a first odrder differntial operator, the formal solution i've found would be $ G(x,s)= \sum_{n} ...
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525 views

Conservative differential equations “in the wild”

Dear MO world, I'm teaching an undergraduate course on "fun with chaos". As part of a test (on bifurcations in differential equations), I asked students to sketch phase portraits for a family of (2d) ...
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1answer
440 views

first-order linear differential equation with boundary conditions

let be the differential equation $ -ixDf(x)-if(x)/2= E_{n}f(x) $ with the boundary conditions $ f(x)=f(p^{k}x) $ for 'p' prime and $k=...,-2,-1,0,1,2,...$ is this possible to solve this eigenvalue ...
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3answers
298 views

Criteria for Involutive Subbundles

Preliminaries: Let $M$ be a smooth manifold with tangent bundle $TM$. A vector subbundle $VM$ of $TM$ is called involutive if the section space $\Gamma(VM)$ of $VM$ is closed under the Lie bracket ...
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1answer
307 views

Bedford-Taylor theory

The Dirichlet problem for the Complex Monge-Ampere equation on a bounded pseudoconvex domain in $\mathbb{C}^n$ was studied in Bedford-Taylor's seminal paper wherein they defined $(dd^{c} u)^n$ for ...
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1answer
354 views

How to deduce the existence of stationary points from fixed points of evolution maps?

This is probably a very elementary question. Nevertheless I decided to post it on MO. Consider a smooth manifold $M$ and a smooth complete vector field $v:M\rightarrow TM$. Consider an autonomous ...
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149 views

On explicit eigenfunctions

Given an algebraic surface $S$ defined by an algebraic equation such as $x^{4}+2y^{4}+3z^{4}=1$, how would one find the third smallest eigenvalue $\mu_{3}$ for the differential equation $\Delta ...
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3answers
865 views

The multiplicity of the max eigenvalue in matrix multiplication

Suppose that eigenvalues of two real square matrix $A$ and $B$ are $1 = \lambda^A_1 > \lambda^A_2 \geq \ldots \geq \lambda^A_n > 0 $ and $1 = \lambda^B_1 > \lambda^B_2 \geq \ldots \geq ...
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1answer
353 views

laplace equation on manifolds with boundary

in aubin's book on page 104 theorem 4.7 there is the theorem: Let $(M,g)$ be a compact $C^{\infty}$ Riemannian manifold. There exists a weak solution $\varphi \in H_{1}$ of $\Delta \varphi = f $ if ...
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368 views

Do these kernel functions satisfy the semi-group property?

Dear Friends, Define the kernel functions for $a\ge 1$, $$ G_a(t,x) := \frac{C_a t}{t^{1+1/a}+|x|^{1+a}}, \qquad \forall t>0,\: x\in R\;, $$ where the constant $C_a$ is some normalization ...
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1answer
381 views

Continuous variation from solution of easy problem to solution of hard problem

I asked this question a week ago over on math.stackexchange and got no reply, so I am asking here with slightly different wording. I am trying to prove that there exists a solution to a problem. I ...
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321 views

Inverse Problem for jet equations

The following is a well known fact and due to the functorial properties of the jet functor: Suppose you have two smooth manifolds $M$ and $N$ and maps $f:M \rightarrow N$ as well as $g: M \rightarrow ...
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132 views

monge ampere equation along totally real submanifolds

hi, are there some references when solving the complex monge ampere equation along totally real submanifolds of some compact (with boundary or without) complex manifold. i know that there are a lot ...
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1answer
703 views

Solution of Heat equation with Neumann BC in an arbitrary domain

Consider the heat equation $u_t=\Delta u$ with Neumann boundary condition and initial condition $u(x,0)=u^0(x)$ in a bounded domain $\Omega$ with smooth boundary. Is this true: Any solution ...
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1answer
157 views

differential structures on unit-root Frobenius modules.

Let $\mathcal{E}$ be the ring of series $f(T)=\sum_{n \in \mathbb{Z}} a_nT^n, \; a_n \in \mathbb{Q}_p$ such that the $\{a_n\}$ are bounded and $a_{-n}\rightarrow 0$ as $n \rightarrow +\infty$. This is ...
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2answers
395 views

calabi conjecture on compact manifolds

hi, is the calabi conjencture formulated for compact manifolds with boundary ? or only for those without boundary ? excuse me if the question is too trivial but in my literature it isn't mentioned ...
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154 views

Inertia/Gravity in Distance Geometry

The Cayley-Menger Determinant, D(N), slickly calculates the N-dimensional simplex volume of any N+1 points. One constraint in our 3D world is that D(4)=0. Give each point a mass (Mi) and dynamic ...
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166 views

Is this Stefan-type problem an open problem?

I am looking for a weak-formulation that would give me an existence and uniqueness of a solution of a Stefan-type problem. It is basically a 2-phase Stefan problem in 2D except that the free-boundary ...
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244 views

$\partial \bar{\partial}$ on a complex manifold

hallo, i have the following question: let $M$ be a complex $n-$dimensional manifold and $R \subset M$ be a totally real, compact, $n-$dimensional (real) manifold. let $\alpha$ be a smooth nonnegative ...
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1answer
517 views

A polynomial recurrence involving partial derivatives

Define recursively polynomials $f_n(a,b)$ by $$ f_0(a,b)=1,\ \ f_n(0,b)=0\ \mathrm{for}\ n>0 $$ $$ \frac{\partial}{\partial a}f_n(a,b) = f_{n-1}(b-a,1-a). $$ For instance, $$ ...
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1answer
305 views

Reparametrizing characteristic curves for PDE's

I'm looking for solutions for a PDE that looks like this $$ \nabla u(\vec x) \cdot f(\vec x) = k. $$ For some clarification, $u$ is a log-probability. And this arises from a Fokker-Plank-like ...
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1answer
286 views

Differences between the Poisson's and elliptic Monge-Ampere equations?

I am working with a numerical application where some known techniques solve $\Delta u=\rho$ for $\rho(x,y)\geq0$ defined on a planar rectangle (given as the density of a large pointset). Since the ...
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3answers
493 views

question about the recursion equation: $x_{n+1}x_{n−1}=x_n^2(1−4x_n)$

Hi all, I am trying to slove the recursion equation: $x_{n+1}x_{n−1}=x_n^2(1−4x_n)$ in the form of $x_n=x_n(x_1,x_2)$ or $x_n=x_n(c_1,c_2)$, and finally get the limit of the ratio: ...
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1answer
225 views

Nonlinear PDE ${u_{tt}}^2u_{ttxx} = 1$

I have been trying to solve this equation during fortnight $$ {u_{tt}}^2u_{ttxx} = 1. $$ But I still here. The only thing is change of variables $u_{tt}(t,x) = y(t,x) $ and solved the ODE $y'' = ...
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2answers
1k views

Looking for the solution of first order non-linear differential equation ($y ′+y^{2}=f(x)$) without knowing a particular solution.

I have been working on Riccati Equation. I have tried many different methods to find a closed form for the solution of first order non-linear differential equation ($y'+y^{2}=f(x)$) without knowing a ...
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0answers
232 views

PDE on the line

In my work I faced a system of PDE of the form \begin{align} \varphi^\prime_v(t,v)|_{v=X_t} = \sigma(t,X_t),\newline \varphi^\prime_t(t,v)|_{v=X_t} = b(t,X_t), \end{align} where ...
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218 views

Periodic orbits of Hamiltonian systems

Consider a second order Hamiltonian system of the type $$ \ddot{x}+V'(x)=0, \quad x \in \mathbb{R}^N. $$ Under very `natural assumptions' it is possible to prove the existence of a non constant ...