# All Questions

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### Solutions of an nonlinear evolution problem

We consider the following continuous-time nonlinear evolution problem $$\begin{cases} \dot{y}(t)=Ay(t)+f(y(t),u(t)),\quad t\geq0\\y(0)=f\in\mathcal{X}\end{cases}$$ where ...
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### Set of regular points in an Alexandrov space with curvature bounded from below

Let $X^n$ be an $n$-dimensional Alexandrov space with curvature bounded from below. A point $x\in X$ is called regular if the space of directions $\Sigma_x$ is isometric to the standard sphere ...
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### Two rational and one irrational root of a cubic? [on hold]

Let $p(x)=a_3x^3+a_2x^2+a_1x+a_0$, with $a_i\in\mathbb{Q}$. Is it true that if two of the roots of $p(x)$ are in $\mathbb{Q}$, then the third is as well?
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