I want a bear as a pet

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Hello I want a bear as a pet and welcome to Wikipedia! We appreciate encyclopedic contributions, but some of your contributions do not conform to our policies. For more information on this, see Wikipedia's policies on vandalism and limits on acceptable additions. If you'd like to experiment with the wiki's syntax, please do so in the sandbox rather than in articles.

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September 2017

Please refrain from making unconstructive edits to Wikipedia, as you did at Chaos theory. Your edits appear to constitute vandalism and have been reverted. If you would like to experiment, please use the sandbox. Repeated vandalism can result in the loss of editing privileges. Thank you. Dr. K. 00:46, 11 September 2017 (UTC)

October 2017

Please stop changing the signs of rotation matrix. They were correct before you changed them. There is extensive discussion on the talk page. please read it and understand the difference between rotation of a vector and rotation of axes. Thank you. Dbfirs 20:06, 28 October 2017 (UTC)

Wrong correction on Special unitary group (May 2)

On April 27, you removed the minus sign in u₂ = -i σ₂, but I am almost certain that you should not remove it. Look at the definitions of u₂ and σ₂ (on the Pauli matrices page).

To answer your question, the page Special unitary group is consistent with the page Pauli matrices. Here is the explanation :

${\begin{aligned}u_{2}={\begin{pmatrix}0&-1\\1&0\end{pmatrix}}={\begin{pmatrix}0&(-i)\cdot (-i)\\(-i)\cdot i&0\end{pmatrix}}=-i{\begin{pmatrix}0&-i\\i&0\end{pmatrix}}=-i\sigma _{1}\,.\end{aligned}}$

Because $(-i)\cdot (-i)=(-1)\cdot (-1)\cdot i^{2}=(-1)\cdot (-1)\cdot (-1)=-1$ and $(-i)\cdot i=(-1)\cdot i^{2}=(-1)\cdot (-1)=1$. — Preceding unsigned comment added by Math-Phys-648 (talk • contribs) 02:20, 3 May 2018 (UTC)