Ziqian Xie
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 Apr17 suggested rejected edit on Derive an exact formula (solve the recurrence definition) for the following recursive sequence: Apr16 comment Inverse laplace transform of $1/(s^2 +1)^{1/2}$ I don't think there is an analytical solution, the inverse laplace transform of this is the bessel function of the first kind. Apr16 comment Question about parallel displacement on a surface Sorry, but I think you misunderstood, I am asking whether the calculation in my question (which is quoted from a problem in the book I mentioned) is right or not, and presumably it is not right because the author explicitly said ‘what's wrong with the following argument’. Apr16 reviewed Reviewed Error bound for Composite Simpson's Rule for $f\notin C^4$ Apr16 comment Question about parallel displacement on a surface Now I understand it is $v$ dependent, but is the above calculation quoted from the book right? The problem asks to find the fault of the calculation. Apr16 comment Which of the following is true for $\int_{1}^{0} x\ln x\, \text dx$? @robjohn yep, I forgot the $\frac{1}{4}$ factor. Apr15 awarded Custodian Apr15 reviewed No Action Needed Setting two equations equal to each other Apr14 comment Question about parallel displacement on a surface @user86418 It should be equal to $\iint K\,ds$, where $K$ is the gaussian curvature. Apr14 comment Which of the following is true for $\int_{1}^{0} x\ln x\, \text dx$? After change of variable, it is $\int_0^{-\infty}xe^x\,dx$. Apr14 asked Question about parallel displacement on a surface Apr12 comment Are there simple examples of Riemannian manifolds with zero curvature and nonzero torsion "A visual introduction to Riemannian curvatures and some discrete generalizations" -Saw it on the comment of your other answer, thx! Apr12 comment Are there simple examples of Riemannian manifolds with zero curvature and nonzero torsion Great answer and illustration! May I ask where do these figures come from? I have seen some of these pictures in Nakahara's Geometry, Topology and Physics, what about the others? I would like to read the book contains the torsion figures. Apr11 comment RC-Circuit for a LIF-Neuron Google 'first order linear differential equations'. Apr11 comment RC-Circuit for a LIF-Neuron The solution is for constant current input $I_0$. Apr10 accepted A question about the index of vector field Apr8 answered A question about the index of vector field Apr7 comment A question about the index of vector field @RyanBudney I think I know how to do it now, since $\mathbf{v}$ can be extended to a nonvanishing vector field on $U$, $\mathbf{v}$ on $M$ can be shrunk continuously into small sphere around any point in $U$, where vector field $\mathbf{v}$ behaves like a constant vector field and has index 0, so the original vector field on $M$ should have index 0. Is this correct? Is this homology? Apr7 comment A question about the index of vector field @RyanBudney exactly. Apr7 comment A question about the index of vector field @RyanBudney Should I say the Brouwer degree of $\mathbf{v}$? It is the degree of map that maps $M$ onto a sphere of the same dimension defined by $\mathbf{v}$.