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For questions about the surreal numbers, which are a real-closed ordered proper-class-sized field that contains both the real numbers and the ordinal numbers. Thus they contain both infinite numbers (including the ordinals, but also infinite numbers like ω-1 and sqrt(ω)) and infinitesimal numbers (like 1/ω). They can also be identified with a subclass of two-player partisan games.

10 votes
1 answer
681 views

In surreal numbers, what is $\ln \omega$?

Can this number $\ln \omega$ be written in $\{L|R\}$ form? What's its birthday?
Anixx's user avatar
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1 vote
1 answer
122 views

Question on derivation of $\omega$ in surreal numbers

This paper gives a derivation definition on log-atomic surreal numbers: where the logarithm with lower index means iterated logarithm. I think — I may be wrong — that $\omega$ is a log-atomic number …
Anixx's user avatar
  • 10.1k
6 votes
2 answers
964 views

In surreal numbers, what is the successor of all the germs in the Hardy field?

I have my own totally ordered hierarchy of quantities, including infinite ones. Can I embeed them in surreal numbers somehow? For instance, I have the quantity $\omega$, which I identify with the simi …
Anixx's user avatar
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6 votes
1 answer
752 views

Are periodic functions such as sine and cosine defined on surreal numbers?

Surely, one can compose a power series for them, and any partial sum of those series would be defined, But are they defined in the limit? I mean, what is $\cos \omega$, for instance? Does the trigonom …
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0 votes
0 answers
117 views

Can one represent divergent integrals or germs at infinity with surreal numbers?

I have been disliking the theory of surreal numbers for a while, but let's test it. So, we have a set of divergent improper integrals of continuous functions with the following ordering: $\int_0^\inft …
Anixx's user avatar
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8 votes
2 answers
906 views

In surreal numbers, what exactly is $\omega_1$?

This answer refers to $\omega_1$ in context of surreal numbers, and calls it "first uncountable ordinal". But what exactly does it mean? How can it be represented in the $\{L|R\}$ form? How do we know …
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  • 10.1k
-4 votes
0 answers
30 views

In surreal numbers, why log-atomic numbers are not EL-numbers?

In surreal numbers, the log-atomic numbers are those numbers that can be obtained from $\omega$ and its powers via iterated logarithm or exponential function. At the same time, Timothy Chow's EL-numbe …
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-1 votes
1 answer
109 views

In surreal numbers, do the automorphisms allow us to define $\omega_2=\partial(\omega_1)$?

Consider surreal numbers as an H-field with operation of derivation. In such setting for any surreal number $\alpha$ such that $0<\alpha<e^\omega$, $\partial(\alpha)<\alpha$ and for $\alpha>e^\omega$, …
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1 vote
1 answer
197 views

Representing the set of rationals $\mathbb{Q}$ as a germ or surreal number

Let us define natural equivalence between elements of Hardy fields and integrals of Dirac comb-like functions. Let us assume a natural embedding of Hardy field into surreal numbers ($[x]=\omega$). De …
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1 vote
1 answer
249 views

Confusion regarding $\ln \omega$

This answer says that in surreal numbers $\ln \omega=\omega^{1/\omega}$. At the same time, this Wikipedia article says that transseries $\mathbb{T}^{LE}$ are isomorphic to a subfield of $No$ with its …
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0 votes
0 answers
138 views

Is standard, affine infinity of extended reals quite small on the scale of infinities?

Some time ago I had a conversation with a guy who was into surreal numbers and he said that in surreal numbers the affine infinity is quite minor entity compared to the ordinality of natural numbers $ …
Anixx's user avatar
  • 10.1k
-1 votes
1 answer
268 views

Why is it said that all surreal numbers with birthdate $<\omega_1$ are isomorphic to a Hardy...

In this answer I have encountered with the following statement: Assuming CH, every maximal Hardy field is isomorphic to $(\bf{No}(\omega_1), \partial_{\omega_1})$, where $\bf{No}(\omega_1)$ is the s …
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0 votes
0 answers
142 views

Why is the property of linearity against an infinitely-large factor considered essential for...

Why the property $(b)$ in Proposition 14 in this paper on surreal integration is considered essential? The Proposition lists the desired properties of the surreal integration, and among others lists t …
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6 votes
1 answer
488 views

In surreal numbers, what are the main difficulties so far in defining integration?

I know, there were several (including unsuccessful) attempts at defining integration on surreal numbers, so I am asking for a good summary of what have been the main difficulties so far. Particularly, …
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