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Based on continued fractions with subtractions, we identify the set of real numbers with the set of infinite integer sequences with all terms but the first one greater or equal to two. Each such sequence produces in a canonical way a unique…

Number Theory · Mathematics 2020-10-13 Rinat Kashaev

We present a coherent collection of finite mathematical theorems some of which can only be proved by going well beyond the usual axioms for mathematics. The proofs of these theorems illustrate in clear terms how one uses the well studied…

Logic · Mathematics 2016-09-07 Harvey M. Friedman

The paper considers the problem of finding the largest possible set P(n), a subset of the set N of the natural numbers, with the property that a number is in P(n) if and only if it is a sum of n distinct naturals all in P(n) or none in…

Discrete Mathematics · Computer Science 2008-09-18 Bidu Prakash Das , Soubhik Chakraborty

This report presents an expression for the number of a multiset's sub-multisets of a given cardinality as a function of the multiplicity of its elements. This is also the number of distinct samples of a given size that may be produced by…

Combinatorics · Mathematics 2015-11-20 Sebastiano Ferraris , Alex Mendelson , Gerardo Ballesio , Tom Vercauteren

Metaphysical interpretations of set theory are either inconsistent or incoherent. The uses of sets in mathematics actually involve three distinct kinds of collections (surveyable, definite, and heuristic), which are governed by three…

History and Overview · Mathematics 2009-05-12 Nik Weaver

We define a multiplication on the surreal numbers as higher inductive-inductive types.

Logic · Mathematics 2018-12-04 Jean S. Joseph

We develop new aspects of the the of numerosity theory; more exactly, we emphasize its relation with the ordinal numbers, cardinal numbers, hyperreal numbers and surreal numbers. In particular, we combine the notion of numerosity with the…

Analysis of PDEs · Mathematics 2025-11-05 Vieri Benci

A natural connection between rational functions of several real or complex variables, and subspace collections is explored. A new class of function, superfunctions, are introduced which are the counterpart to functions at the level of…

Algebraic Geometry · Mathematics 2016-02-23 Graeme W. Milton

Let No be Conway's class of surreal numbers. I will make explicit the notion of a function f on No recursively defined over some family of functions. Under some "tameness" and uniformity condition, f must satisfy some interesting…

Logic · Mathematics 2007-05-23 Antongiulio Fornasiero

We present the concept of the \emph{information efficiency of functions} as a technique to understand the interaction between information and computation. Based on these results we identify a new class of objects that we call…

Computational Complexity · Computer Science 2019-04-09 P. W. Adriaans

Let surreal numbers be defined by means of sign sequences. We give a proof that if $S < T$ are sets of surreals, then there is some surreal $w$ such that $S < w < T$. The classical proof is simplified by observing that, for every set $S$ of…

Number Theory · Mathematics 2018-05-22 Paolo Lipparini

This article explores the model-dependent nature of set cardinality, emphasizing that cardinality is not absolute but varies across different axiomatic frameworks. Although Cantor's diagonal argument shows the real numbers are…

Logic · Mathematics 2025-06-10 Slavica Mihaljevic Vlahovic , Branislav Dobrasin Vlahovic

For a given irrational number, we consider the properties of best rational approximations of given parities. There are three different kinds of rational numbers according to the parity of the numerator and denominator, say odd/odd, even/odd…

Number Theory · Mathematics 2024-03-20 Dong Han Kim , Seul Bee Lee , Lingmin Liao

We discuss how to write down three specific natural numbers $A$, $B$, $C$ such that for any real number $r$ you've probably ever thought of, it is consistent with $\mathsf{ZFC}$ set theory that $$\def\Rb{\mathbb{R}}\def\Nb{\mathbb{N}}r =…

Logic · Mathematics 2026-02-03 James E. Hanson , Connor Watson

Let $\mathbf{x}$ be a (non-empty) sequence of positive real numbers. Its achievement set $\mathcal{\mathbf{x}}$ is the set of all the possible sums of the elements of $\mathbf{x}$. The cardinal function of $\mathbf{x}$ is the function…

Classical Analysis and ODEs · Mathematics 2025-08-19 Jacek Marchwicki , Błażej Żmija

Among three natural numbers there is always one which is larger than or equal to the Nim sum of the remaining two numbers. This amazing fact has many applications.

Combinatorics · Mathematics 2015-03-05 Christoph Hering

We present a novel framework for measuring the size of discrete subsets of using surreal-valued numerosity, which strictly satisfies Euclid's principle that "the whole is greater than a part". By mapping numerosities to surreal numbers via…

General Mathematics · Mathematics 2026-04-21 Ilya Shnitman

Conway's real closed field $\mathbf{No}$ of surreal numbers is a sweeping generalization of the real numbers and the ordinals to which a number of elementary functions such as log and exponentiation have been shown to extend. The problems…

Logic · Mathematics 2024-07-08 Ovidiu Costin , Philip Ehrlich

Cantor's famous proof of the non-denumerability of real numbers does apply to any infinite set. The set of exclusively all natural numbers does not exist. This shows that the concept of countability is not well defined. There remains no…

General Mathematics · Mathematics 2009-09-29 W. Mueckenheim

Natural numbers from 0 to 11111 are written in terms of 1 to 9 in two different ways. The first one in increasing order of 1 to 9, and the second one in decreasing order. This is done by using the operations of addition, multiplication,…

History and Overview · Mathematics 2014-01-09 Inder J. Taneja