Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with trace
Search options answers only
not deleted
user 342609
Use this tag when having questions concerning expressions with the trace of a matrix/operator.
7
votes
Unitary equivalence between Hermitian operators
The time evolution of the position operator of a free particle in quantum mechanics (Hamiltonian $H=P^2/2m$) is a nice counterexample:
$ e^{iHt/\hbar} X e^{-iHt/\hbar} = X + P t/m$,
with $A=X$ (positi …
- 7,298
0
votes
How to prove $\mathrm{Tr}[(\partial_\mu U)U^\dagger]=0$?
Even in the absence of an additional relation, a term of the form ${\rm Tr} (\partial_\mu A \,\, \partial^\mu B)$ in the Lagrangian would be (physically) equivalent to $- {\rm Tr} [ (\partial_\mu \ …
- 7,298
2
votes
Accepted
What is the physically significance of having trace less than 1 in squared mixed state densi...
The trace of $\rho^2$ is thus given by ${\rm Tr} \rho^2 =\sum_n p_n^2 \le 1$, where the equality sign holds if and only if $p_m=1$ for some index $m$ and $p_n=0$ for $n\ne m$. …
- 7,298
3
votes
Can the Dirac trace of two gamma matrices always be made positive?
Quite generally, you have ${\rm Tr}(-A B)=-{\rm Tr}(A B)=-{\rm Tr}(BA)$ for arbitrary square matrices $A$, $B$.
- 7,298