6,063 reputation
11537
bio website tuwien.ac.at/goldstern
location
age
visits member for 2 years, 11 months
seen Apr 12 at 20:10

1d
awarded  Nice Question
Mar
15
comment What are the properties of this linear operator?
Perhaps your question is this: Can the operator, which is a priori only defined on certain even functions, be extended (continuously? uniquely? canonically?) to all (even? analytic?) functions?
Feb
23
revised Formal proof of Con(ZFC) => Con(ZFC + not CH) in ZFC
spelling, syntax
Feb
15
comment Can a Decidable Theory Have Non-recursive Models?
More explicitly: if you only consider formulas not using the equality symbol, this theory has quantifier elimination, in the most obvious and uninteresting way: Removing all quantifiers from any formula leaves you with a logically equivalent formula. If you do allow the equality symbol, and add axioms ensuring that the universe is infinite, then the theory (like the theory of equality, and for the same reason) has full elimination of quantifiers.
Feb
11
comment Can we unify addition and multiplication into one binary operation? To what extent can we find universal binary operations?
As I just discovered, Trevor Evans showed this (at least for countable base sets) in 1989 in his paper "Embedding and representation theorems for clones and varieties", Bull. Austral. Math. Soc. 40. MR1012828 (90k:08004)
Feb
4
awarded  Enlightened
Feb
4
awarded  Nice Answer
Feb
4
comment Consistency Results Separating Three Cardinal Characteristics Simultaneously
Thank you for advertising. Suggestions/corrections/comments are welcome.
Feb
4
revised Consistency Results Separating Three Cardinal Characteristics Simultaneously
unicode hex coding works better for links: %c5%84
Jan
30
comment The theory of two finite linear orders
Thank you! That was really an answer, not a comment.
Jan
29
asked The theory of two finite linear orders
Jan
20
awarded  Good Answer
Jan
16
comment Strong measure zero sets and selection principles
What is the Borel property of strong measure zero? What is the reference that is not in English?
Jan
12
comment Does a nonlinear additive function on R imply a Hamel basis of R?
@AlexanderPruss: You are right, I did not think of the possibility that my f may take infinite values. If I knew that the values of f on R are all finite, I could round them to the next real number without violating additivity. But I don't think this can be achieved with compactness only, and I don't think there is an omitting type theorem for uncountable languages.
Dec
31
comment How can I collapse all cardinals of ground model except one of them?
Do you mean a forcing extension? Class forcing?
Dec
31
comment How can I collapse all cardinals of ground model except one of them?
$\aleph_0$ never collapses.
Dec
29
comment Mathematical research published in the form of poems
Free version: gdz.sub.uni-goettingen.de/dms/load/img/…
Dec
21
revised Equivalence relations on powerset of R^2
link to mse
Dec
1
comment Subsets of Real Numbers (Edited & Revised Version)
I did not understand what St.Georg meant with his definition of $B$, and I do not see which set (or formula?) $B$ this answer refers to. Could you please add your definition of $B$ to your answer?
Nov
25
answered An informal version of the recursion theorem