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Results for believe in "V=L"
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110 votes
10 answers
15k views

Analogues of P vs. NP in the history of mathematics

The question is this: When, in the history of mathematics, have problems "like P vs. NP" arisen and then been solved? In those cases, what were the resolutions? … Until Cohen, there were many proven statements about transfinite sets, and then a whole class of other statements---V=L, GCH, CH, AC, Zorn's Lemma, well-orderability... …
23 votes
3 answers
3k views

Why believe in the existence of large cardinals rather than just their consistency?

What reasons are there to believe in their truth, rather than merely in their consistency, or at most their truth in some transitive model? … One might be $V = L$, or even the axiom of restriction, but most set theorists dismiss them, as they rule out large large cardinals and inaccessible cardinals, respectively, and instead seek core models …
23 votes
Accepted

Why believe in the existence of large cardinals rather than just their consistency?

Without that existence, we wouldn't have any reason to believe in even the much weaker consistency assertions. … According to Steel, the large cardinal set-theorist can still consider the nature of V=L set theory, without the stronger large cardinals, simply by relativizing set theory to L. …
Joel David Hamkins's user avatar
28 votes
0 answers
2k views

How did Gauss find the units of the cubic field $\mathbb Q[n^{1/3}]$?

=v, t''= \frac{t'v'}{l'}, t''' = \frac{t''v''}{l''}, etc.$$ He also uses the notation $Div$, which I believe is an abbreviation for "Divisor", since the arithmetical procedure he describes involves the … Secondly, the power of $z$ written there is actually 4; I believe this is just a typo of Gauss. Thirdly, this cubic form has $v=|2^{\frac{1}{3}}|$, and I believe $\epsilon$ is a third root of unity. …
27 votes
Accepted

On statements independent of ZFC + V=L

retains its large cardinal property in L, so we get consistency with V=L. … These are all independent of ZFC+V=L, since they are independent of ZFC, and their truth is the same in V as in L. …
Lucenaposition's user avatar
13 votes
0 answers
1k views

Is there any correspondence between Gödel and Kreisel that supports Kreisel's observation th...

National Acad., 1938, he remarks that V=L added as a new axiom seems to give a natural completion of the axioms of set theory, in so far as it determines the vague notion of an arbitrary infinite set in … So Davis (and apparently also Kreisel) believed that Gödel accepted V=L in 1938 as a new axiom. …
2 votes
0 answers
131 views

Generic behavior of the degree of a projective variety

Now, consider the incidence correspondence $X = \lbrace (v,L) \in V \times \mathrm{Gr}(k+1,n+1) \mid v \in L \rbrace \subset V \times \mathrm{Gr}(k+1,n+1)$. This is a projective variety. … \cap L) = 0$ for all $L \in U$. …
20 votes
Accepted

Are some interesting mathematical statements minimal?

Since it is a model of $\text{ZFC}+V=L$, one gets on board all of the consequences of that theory in the minimal model. … But there are many further properties true in the minimal model, when it exists, that are not provable from $\text{ZFC}+V=L$. …
Joel David Hamkins's user avatar
14 votes

Why is inner model theory evidence for consistency of large cardinals?

I believe it is essentially this perspective that is expressed by the quotations you have made in the original question. … For example, if ZFC is consistent, then we know that it is consistent that ZFC + V=L + ¬Con(ZFC), with the point being that in any world fulfilling this theory, we would have the full fine-structural account …
Joel David Hamkins's user avatar
12 votes
1 answer
512 views

Why do we need the comparison lemma?

way of building up the model $L[A]$), which have to have well-founded ultrapowers (in which case they are called mice), and one needs a comparison lemma for establishing which mice are initial segments … I read some of Steel’s “The Comparison Lemma” in my quest for an answer, and it mentioned that for $L$ the mice are just well-founded structures satisfying a fragment of $\mathrm{ZFC}$ and $V = L$, which …
1 vote

Standard models of N and R: An Alice/Bob approach

I don't believe "ultimate L" will ever gain popular traction, for reasons that should be apparent. … I think the question of whether $V$ equals $L$ is far more important to settle. My opinion about $V=L$ is in the minority, but it has had some important supporters. …
Jesse Elliott's user avatar
4 votes

Standard models of N and R: An Alice/Bob approach

There cannot be a "true" $V$. There cannot even be a completed collection of all ordinals. … This rules out wanting $V=L$ as an axiom, as that limits the types of collections available. …
Pace Nielsen's user avatar
  • 18.7k
0 votes

What can one say about the Dirichlet problem for Schrödinger equation with negative potential?

I will assume $V \in L^\infty(\Omega)$ is smooth, $V>0$ and $g \in C^1(\partial \Omega)$. … {L^\infty}}{\lambda_1(\Omega)} \int_\Omega |\nabla u|^2 + 2\|V\|_{L^\infty} \int_\Omega w^2 \,, $$ hence $$ J(u) \ge \left(1-\frac{2\|V\|_{L^\infty}}{\lambda_1(\Omega)} \right) \int_\Omega |\nabla u|^2 …
Michele Caselli's user avatar
27 votes
Accepted

Are there any good nonconstructive "existential metatheorems"?

In particular, to prove that a particular $\Sigma^1_2$ statement is true in ZFC, it suffices to prove it under the assumption also that V=L, where one also has all kinds of additional structure available … To prove that there is a proof, is a proof, so I believe ultimately there will be no way to avoid the quibbling over whether it is easy or hard to translate the high-level proof into a low level proof, …
C7X's user avatar
  • 2,031
1 vote
1 answer
360 views

How are Koepke's ordinal computability and E-recursion related?

It is interesting to note that Sacks' proof of Theorem 3.1 from his paper gives an indication of what must happen if $V\neq L$ (most set theorists do not believe that $V$=$L$ is an 'acceptable' axiom): … Suppose $\forall x(x\in L\leftrightarrow\{e\}(x)\downarrow)$ and $V\neq L$. Then for some $b\notin L$, $\{e\}(b)\uparrow$. …

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