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Jan
14
revised Von Neumann algebras with uncountable sets of incompatible projections
added 604 characters in body
Jan
13
answered Von Neumann algebras with uncountable sets of incompatible projections
Jan
13
answered To find Wronskian of a ODE
Jan
13
awarded  Yearling
Jan
9
comment Proof that $A^{-1}=adj(A)/|A|$
I don't know the actual history, but things like this are usually a combination of the ideas of several very smart people working first on examples and abstracting from there. I
Jan
9
answered Proof that $A^{-1}=adj(A)/|A|$
Jan
8
comment union of group von neumann
To talk about "closure" you need an environment. Where would the union live? This is key to answer the question.
Jan
8
comment solve $-u''(x)+\int_0^{\pi}u(y)dy=\lambda u(x)$,where $u(0)=u(\pi)=0$
I fail to see why you introduced the initial condition $u'(0)=1$.
Jan
7
comment The series of $\sin A$, when $A$ is a $n \times n$ matrix
The first inequality is not true. It fails for example for $n=1$ and $A=3\pi/2$.
Jan
6
comment If$ p \in B(H)$ is a projection, then $r \in A'$ if and only if the closed vector subspace $p(H)$ of $H$ is invariant for $A$.
I feel you are making it unnecessarily complicated: from $pT^*p=T^*p$ you get $pTp=pT$ directly by taking adjoints. The assertion "W invariant under $T^*$ implies $W^\perp$ invariant under $T$" is basically what needs to be proven.
Jan
5
comment Two Banach spaces, if and only if criterion for range of closed unbounded operator to be closed?
Nice! $\ \ \ \ $
Jan
5
comment Two Banach spaces, if and only if criterion for range of closed unbounded operator to be closed?
Problems I see: 1. The distance to a closed subspace is not always realized; 2. If you have the inequality $\|x_n\|\leq\|y_n\|$ and $\{y_n\} $ is Cauchy, you cannot conclude that $\|x_n\|$ is Cauchy; 3. In your last part, your argument "works" for any closed operator: if $u_n $ is Cauchy in $\|\cdot\|_G $ then from the graph closed you would get your conclusion.
Jan
5
answered Prove: the density operator of a pure state has exactly one non-zero eigenvalue equal to unity
Jan
5
answered nilradical of a finite-dimensional algebra
Jan
2
comment If a set has infinite measure is it NOT lebesgue measurable? If so why?
@CarlMummert: good point!
Jan
2
answered Prove that $\sqrt{2} \notin \mathbb{Q}(\sqrt{3})$.
Dec
31
comment What do instantaneous rates of change really represent?
@Bernard: +1; but to be pedantic, it measures rpm on the other side of the gear box ;)
Dec
31
awarded  Good Answer
Dec
31
answered Applying Neumann series
Dec
30
answered Set of discontinuities of a function that has both limits at each point of $R$