# Is there provably a largest cardinal consistent with ZF?

The existence of such large cardinals is not provable in ZFC (but for all we know, it might be that ZFC proves the non- existence of some of them!).

Contents

## What is a large cardinal number?

In the mathematical field of set theory, a large cardinal property is a certain kind of property of transfinite cardinal numbers. Cardinals with such properties are, as the name suggests, generally very “large” (for example, bigger than the least α such that α=ωα).

## Is ZFC complete?

A theory is complete iff: Every sentence that has no proof-of-its-negation can be proved. First-order logic is complete in the first sense. ZFC is (assuming it is consistent) incomplete in the second sense — that is, there are sentences that ZFC neither proves nor disproves.

## Are ZFC axioms consistent?

Consistency proofs for ZFC are essentially proofs by reflection, meaning that we note, in some way or another, that since the axioms of ZFC are true, they are consistent.

## Why are large cardinals important?

Here is one of the main results about the usefulness of large cardinals: They provide us with a clear “complete” first order theory of the reals. What I mean is this: Without the assumption of large cardinals, there are many first order statements about the reals whose truth value can be changed by forcing.

## Are there biggest cardinals?

(And anyway, there is no largest large cardinal axiom because there is no maximal consistent recursive extension of ZFC.)

## What is the biggest inaccessible cardinal?

There is no largest cardinal, this is just Cantor. As to the large cardinal axioms, that’s a whole other matter. The “0 = 1” axiom is sort of a joke (though it’s not wrong). The large cardinal axioms are stronger and stronger in consistency strength meaning they prove more and more.

## Is ZF consistent?

NO; if ZF is consistent, it has a model but this model is not a set whose existence the theory ZF can prove to exist. To prove the consistency of ZF we need a “stronger” meta-theory.

## Is it possible to prove ZFC consistent?

Since ZFC satisfies the conditions of Gödel’s second theorem, the consistency of ZFC is unprovable in ZFC (provided that ZFC is, in fact, consistent). Hence no statement allowing such a proof can be proved in ZFC.

## What are the axioms of ZF in set theory?

Axioms of ZF

This axiom asserts that when sets \(x\) and \(y\) have the same members, they are the same set. Since it is provable from this axiom and the previous axiom that there is a unique such set, we may introduce the notation ‘\(\varnothing\)’ to denote it.

## Is Aleph Null an inaccessible cardinal?

If the generalized continuum hypothesis holds, then a cardinal is strongly inaccessible if and only if it is weakly inaccessible. (aleph-null) is a regular strong limit cardinal.

## What is a male cardinal called?

Northern Cardinals or “Redbirds”

The bright plumage of the male is responsible for the northern cardinal’s nickname: the redbird. Besides the bright red plumage, males have a black mask on their faces. Females lack the mask, and their brown or greenish-brown plumage is less distinctive.

## What are cardinal numbers?

In informal use, a cardinal number is what is normally referred to as a counting number, provided that 0 is included: 0, 1, 2, …. They may be identified with the natural numbers beginning with 0. The counting numbers are exactly what can be defined formally as the finite cardinal numbers.

## How many cardinal numbers are there?

Since 0 means nothing; it is not a cardinal number. We can write cardinal numbers in numerals as 1, 2, 3, 4, and so on as well as in words like one, two, three, four, and so on. The chart shows the cardinal numbers in figures as well in words.

## What is the lowest cardinal number?

one

The lowest cardinal number is one. This is the smallest whole amount of anything you can have. There is an infinite number of cardinals, but zero isn’t one of them.

## How do you find a cardinal number?

So to find the cardinal number of set a we simply count how many elements are in there. So since this contains the letters a B C.

## How do you find the cardinal number of a large set?

Number or cardinality of the set we use the symbol n with the parentheses. Around the name of the set like n of a to represent the cardinal number of the set.

## Is 11 a cardinal number?

The cardinal numbers are the numbers that are used for counting something. These are also said to be cardinals. The cardinal numbers are the counting numbers that start from 1 and goes on sequentially and are not fractions. The examples of cardinal numbers are: 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,….

## What does Aleph Null mean?

Definition of aleph-null

: the number of elements in the set of all integers which is the smallest transfinite cardinal number.

## Is Omega bigger than Aleph Null?

ω+1 isn’t bigger than ω, it just comes after ω. But aleph-null isn’t the end. Why? Well, because it can be shown that there are infinities bigger than aleph-null that literally contain more things.

## Is there an aleph 2?

Regardless of the status of the continuum hypothesis, aleph 1 is the cardinality of the set of countable ordinals. Then aleph 2 would be the cardinality of the set of at most aleph 1-sized ordinals, and so on.

## Is Rayo’s number the biggest number?

Definition. The definition of Rayo’s number is a variation on the definition: The smallest number bigger than any finite number named by an expression in the language of first-order set theory with a googol symbols or less.

## Is anything bigger than Rayos number?

Note that, in this new theory, Rayo’s number can now be described very briefly, in terms of this new constant! So H(1, 10100) will be much larger than Rayo’s number.

## What is bigger than a Googolplexianth?

Graham’s number is bigger than the googolplex. It’s so big, the Universe does not contain enough stuff on which to write its digits: it’s literally too big to write. But this number is finite, it’s also an whole number, and despite it being so mind-bogglingly huge we know it is divisible by 3 and ends in a 7.