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Mirrors > Home > MPE Home > Th. List > Mathboxes > df-no | Structured version Visualization version GIF version |
Description: Define the class of
surreal numbers. The surreal numbers are a proper
class of numbers developed by John H. Conway and introduced by Donald
Knuth in 1975. They form a proper class into which all ordered fields
can be embedded. The approach we take to defining them was first
introduced by Hary Goshnor, and is based on the conception of a
"sign
expansion" of a surreal number. We define the surreals as
ordinal-indexed sequences of 1𝑜 and 2𝑜, analagous to Goshnor's
( − ) and ( + ).
After introducing this definition, we will abstract away from it using axioms that Norman Alling developed in "Foundations of Analysis over Surreal Number Fields." This is done in an effort to be agnostic towards the exact implementation of surreals. (Contributed by Scott Fenton, 9-Jun-2011.) |
Ref | Expression |
---|---|
df-no | ⊢ No = {𝑓 ∣ ∃𝑎 ∈ On 𝑓:𝑎⟶{1𝑜, 2𝑜}} |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | csur 31037 | . 2 class No | |
2 | va | . . . . . 6 setvar 𝑎 | |
3 | 2 | cv 1474 | . . . . 5 class 𝑎 |
4 | c1o 7440 | . . . . . 6 class 1𝑜 | |
5 | c2o 7441 | . . . . . 6 class 2𝑜 | |
6 | 4, 5 | cpr 4127 | . . . . 5 class {1𝑜, 2𝑜} |
7 | vf | . . . . . 6 setvar 𝑓 | |
8 | 7 | cv 1474 | . . . . 5 class 𝑓 |
9 | 3, 6, 8 | wf 5800 | . . . 4 wff 𝑓:𝑎⟶{1𝑜, 2𝑜} |
10 | con0 5640 | . . . 4 class On | |
11 | 9, 2, 10 | wrex 2897 | . . 3 wff ∃𝑎 ∈ On 𝑓:𝑎⟶{1𝑜, 2𝑜} |
12 | 11, 7 | cab 2596 | . 2 class {𝑓 ∣ ∃𝑎 ∈ On 𝑓:𝑎⟶{1𝑜, 2𝑜}} |
13 | 1, 12 | wceq 1475 | 1 wff No = {𝑓 ∣ ∃𝑎 ∈ On 𝑓:𝑎⟶{1𝑜, 2𝑜}} |
Colors of variables: wff setvar class |
This definition is referenced by: elno 31043 sltso 31068 |
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