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# 22 Comments

 Aug15 comment Is this expression for the Riemann Tensor correct? The c's and the p's are smooth functions on the manifold Aug14 comment What does this notation means in noncommutative case But in the page en.wikipedia.org/wiki/Covariant_derivative#Formal_definition they use the notation $V f$ also to indicate the directional derivative of a function along $V$. Then it is misleading to choose one or the other alternative above. How should I interprete? Feb2 comment Find all the functions which satisfy a given functional equation @DejanGovc I was editing while I received your post. Please check it again Feb2 comment Find all the functions which satisfy a given functional equation @Alex did you assume $f(0)=0$ in your solution? Because then I'm pretty sure that $f(0)=-1$ is also possible. My apologies since I inverted $x,y$ in the first term of the equation. Please check the edited version. Still my apologies. BTW in this case setting $x=y=0$ gives $f(f(0))=f(0)^2+f(f(0))+f(0)$ from which $f(0)\in \{-1,0\}$. Nov5 comment Ordering of two weak star limits lol you are right... Oct29 comment At most three different eigenvalues @GerryMyerson I'm following the language introduced in the Birkhoff Rota Ordinary differential equation book and you can define the operator $L[u]=u'+q(x)u$ so for $\lambda$ to be an eigenvalue it means that $L[u]=\lambda u$ has a non trivial solution $u$. Oct29 comment At most three different eigenvalues @JuliánAguirre it is $u'$, it is a first order DE Oct29 comment airy equation vanish infinitely many times nice. Didn't know about this one. Can we solve the exercise without using that theorem? Sep5 comment Weak closedness implies closed and convex how do you prove that, with your choice of $A$, $S_p(A)$ is weakly closed in $L^p(I,\mathbb R^n)$? Aug29 comment convergence in $L^r(I)$ $\|f_n\|_p$ is bounded Aug24 comment necessary conditions to be relatively compact what if $F_\varepsilon\cap A$ is empty? Aug22 comment differential system on the torus So i presume you would like to conclude that $\tilde u$ and $\tilde v$ are identically zero, being harmonic and with $0$ integral. Am I right? but unfortunately i cannot conclude by myself. Can you help me? Aug21 comment Estimate on the interval of definition as parameter varies I'm afraid your calculations are not correct.. Aug4 comment Prove that the solution tends to $0$ as $t$ goes to infinity Excellent.. thank you did.. Aug4 comment Prove that the solution tends to $0$ as $t$ goes to infinity I don't get your point about symmetry.. can you please provide more details? Aug4 comment Prove that the solution tends to $0$ as $t$ goes to infinity I don't know.. form your proof $<0$ seems to suffice indeed.. i copied the text as i found it.. Aug4 comment Prove that the solution tends to $0$ as $t$ goes to infinity Where did you used that the matrix is simmetric? Was it just a redundant information? Jul21 comment Prove that this function is measurable Can you please provide more details in the first point of your argument? Still I cannot follow you completely even though you are convincing me you are right... Moreover, I can't see what is $j$ in the formula.. Of course later i will accept your answer.. Thank you Davide Jun11 comment $A$ has measure $0$ you mean... $\sin(n_kx)\to\pm\frac{1}{\sqrt2}$? Jun11 comment $A$ has measure $0$ but what if, for example, $n_k=4k+1$ and $x=\frac\pi2$? In this case the limit exists and it is constantly $1$ so I cannot claim that if the limit exists then it is $0$. I don't get your point sorry...