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I'm a graduate student at UC Berkeley, studying mathematical logic. I'm especially interested in reverse mathematics and abstract model theory.
13h

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Polinominal equations
Explain why it is a good idea to do your own homework. Use reasoning to expand your explanation to find the general benefits of doing your own homework. 
Jan 27 
awarded  Notable Question 
Jan 27 
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A Classification problem in measure theory
What is the motivation for this problem? Also, what sort of thing would count as a classification? 
Jan 25 
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calculating E(Xt^2,Xth^2) with Xt normal(0,sigma^2)
Please do not ask homework questions here. 
Jan 25 
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Are hyperreal numbers isomorphic to formal power series?
Again, "$No$" is from the surreals, not the hyperreals. 
Jan 24 
revised 
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Jan 24 
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Are hyperreal numbers isomorphic to formal power series?
Anixx, based on your most recent comment I think you might be confusing the hyperreals with the surreals, which are two very different things. In particular, there's no "special" element of 'the' hyperreals which we deem "$\omega$." 
Jan 24 
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paradox about the Axiom of Choice?
Google is your friend: google.com/… 
Jan 23 
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Book on Convergence Concepts in Probability without Measure Theory
Also, entirely separately  and I should have mentioned this in my first comment  measure theory is incredibly cool. See it now so you can see more later! 
Jan 23 
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nonstandard models and mathematical theorems
Sneaky! I like it. 
Jan 23 
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Book on Convergence Concepts in Probability without Measure Theory
Personally, I feel there's few things as useful as learning some measure theory as early as possible, especially if you're seriously interested in probability; but that's just my opinion. 
Jan 23 
answered  On whether a formula of KP is $\Pi_3$ 
Jan 22 
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Matching power series to infinity
I was thinking in a slightly different direction: off the top of my head, I think we have a reasonable ring of power series for any index set $I$ which is the underlying set of a monoid $(I, *)$ such that for each $x$ in $I$, there are only finitely many pairs $y_1, y_2$ with $y_1*y_2=x$. But maybe there's another obstacle? 
Jan 22 
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Matching power series to infinity
Actually, note that this establishes an equivalence: the statement "if every coefficient of the powerseries is a multiple of $c$, then the series is a multiple of $c$" is equivalent (over ZF) to the axiom of countable choice. And, if we generalize the class of formal power series to index sets other than $\omega$ in the natural way, we get equivalences with other forms of choice, too. 
Jan 22 
answered  Matching power series to infinity 
Jan 21 
revised 
Decidability of diophantine equation in a theory
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Jan 21 
revised 
Decidability of diophantine equation in a theory
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Jan 21 
revised 
Decidability of diophantine equation in a theory
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Jan 21 
answered  Decidability of diophantine equation in a theory 
Jan 21 
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Total formulae in a theory equivalent to $\Delta_0$ formulae in the theory?
(Also, in this context, it's good to give the provability predicate "$Bew$" a subscript, i.e., $Bew_{PA}(x)$ instead of $Bew(x)$.) 