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For questions about mathematical problems arising from quantum mechanics, a branch of physics describing the behaviour of nature at very small scales, at the level of atoms and subatomic particles.
3
votes
Accepted
Interpretation of a parameter in forming a pseudodifferential operator
Let me answer to your second query and make $h=1$. You have
$$
Op_1(a(x) \xi)= a(x) D_x,\quad \text{with $D_x=-i\partial_x$},
$$
$$
Op_0(a(x) \xi)= D_x a(x),
$$
$$
Op_{1/2}(a(x) \xi)= \frac 12D_x a(x) …
7
votes
Accepted
Is there an equivalent of Heisenberg's uncertainty principle in the decision sciences ?
Let me answer in terms of operator theory. The uncertainty principle can be interpreted as some particular inequality (as you say) such as
$$
\frac{\hbar}{2}\Vert{u}\Vert^2\le \Vert{D_xu}\Vert\Vert{xu …
1
vote
Observable nearly commuting with a "complete" set of commuting observables
Well, you have
$$
[\frac{1}{idx},x]=1/i
$$
although $\frac{1}{idx}$ is far from the Identity.
2
votes
Accepted
Massive dirac operator symmetric spectrum
With $z=x+iy$, we use the Fourier transformation in $(x,y)$ to see that $H$ is unitarily equivalent to
$$
\frac12\begin{pmatrix}2m&\xi-i\eta\\
\xi+i\eta&-2m\end{pmatrix},
\text{whose eigenvalues are } …
8
votes
1
answer
455
views
On commutator of bounded operators
Let $\mathbb H$ be a Hilbert space and let $\mathcal B(\mathbb H)$ be the bounded operators on
$\mathbb H$. Let $J,K\in \mathcal B(\mathbb H)$ such that
$
J=J^*, K=-K^*.
$
Then the commutator $[J,K]$ …
1
vote
Accepted
Witten index non-trivial in the context of Quantum Mechanics?
Consider the most classical example, $D=\frac{d}{dx}-x$, which is the creation operator. Note that $D$ is injective since, with $L^2$ norms and dot-products and say $u$ in the Schwartz class,
$$
\Vert …
0
votes
Is there a 'certainty' principle?
With $D_x=\frac{d}{i dx}$, the Heisenberg uncertainty principle in its most classical form can be deduced from the equality
$$
2\Re \langle \hbar D_x u, ix u \rangle_{L^2(\mathbb R)}= \langle \bigl[\h …
4
votes
When is this operator positive semi-definite?
Too long for an additional comment. I guess that you can keep the assumption $\hat P, \hat Q$ Hermitian and require
$$
[\hat P, \hat Q]=1/(2πi),
$$
as it is the case with the prototypical example
$
\h …