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seen Oct 10 at 15:17

Jul
17
comment Inequality: $2\sqrt{xz}+2\sqrt{yz}+2\sqrt{xy}\geq 3x+3y+3z-3$
thanks! I followed through your instructive steps and it worked perfectly.
Jun
28
comment If $4k^3+6k^2+3k+l+1$ and $4l^3+6l^2+3l+k+1$ are powers of two, how to conclude $k=1, l=2$
Thanks for the help! I think $S$ should be $S=2(x+y+1)(2(x^2-xy+y^2)+x+y+1)$ (with minus sign)
Jun
23
comment When is $(a^2+b)(b^2+a)$ a power of $2$?
I thought of this question myself, just experimenting :)
Jun
23
comment When is $(a^2+b)(b^2+a)$ a power of $2$?
that was fast. thanks!
Jan
25
comment Maximum number of different diagonals obtained by column permutations
Thanks Zackkenyon, my question is the latter: "What is the maximum number of diagonals among all such matrices?"
May
2
comment (Logic) Formally writing a rational number in logic
thanks, I think the key idea "multiplying by a suitable integer, a common denominator of the coefficients of P ." is really useful. This way one can avoid rationals altogether.
May
2
comment Definable with parameters (Example)
Sorry for the confusion! What I meant is that is there any set that is definable with parameters but not definable without parameters?
Apr
28
comment (Logic) Formally writing a rational number in logic
Thanks, this is an awesomely clear answer.
Apr
25
comment How to show that the property of being algebraically closed is reflected by elementary extensions?
Thanks! I wonder if is it true that any elementary extention of a non-algebraically closed field is also not algebraically closed?
Apr
25
comment How to show that the property of being algebraically closed is reflected by elementary extensions?
Thanks! Assume that the structure $(F,0,1,+,\cdot)$ is a countable elementary submodel of the complex field $(\mathbb{C},0,1,+,\cdot)$.
Apr
25
comment Logic automorphism question about $(\mathbb{R},0,1,+,\cdot,<)$.
Is the harder question related to proving Aut($\mathbb{R}/\mathbb{Q}$)=1?
Apr
24
comment How to show that a theory T union a sentence $\varphi$ is consistent.
oh yes, I missed out several information about $T$, pls see edit. Thanks!
Apr
24
comment How to show that a theory T union a sentence $\varphi$ is consistent.
$T$ is assumed to be consistent (as stated in question), if that helps?
Apr
24
comment How to show that a theory T union a sentence $\varphi$ is consistent.
what is reductio?
Apr
22
comment Logic question regarding a countable elementary submodel of the complex field.
just a "subquestion", what is the difference between elementary submodel, elementary substructure, and the elementary extension you just mentioned? sorry, really confused.
Apr
22
comment Logic question linking $\omega$-categoricalness to completeness
Do you mean $\omega$-categorical?
Mar
25
comment Quantum Groups: prove $U_1'\cong U[K]/(K^2-1)$ and $U\cong U_1'/(K-1)$
thanks for the help! (I have awarded the +500 bounty to this solution.)
Mar
21
comment Prove well-definedness of comultiplication and counit of $GL_q(2)$ and $SL_q(2)$.
just a further question, how does showing the above computations show that $\Delta$ and $\epsilon$ are well-defined?
Feb
27
comment Different definition of antipode for $SL_q(2)$?
Thanks. In Kassel, it is written that the comultiplication $\Delta$ of $M_q(2)$ equip $SL_q(2)$ with Hopf algebra structures. And the comultiplications seem to be the same, $\Delta (a)=a\otimes a+b\otimes c$, etc. I am really puzzled.
Jan
19
comment Basis of $SL_q(2)$
@JulianKuelshammer thanks a lot. may i ask how is the topological group (denoted as $F_h(SL_2(\mathbb{C}))$ different from $SL_q(2)$?