Though only a few classes of transcendental numbers are known, partly because it can be extremely difficult to show that a given number is transcendental, transcendental numbers are not rare: indeed,almost all real and complex numbers are transcendental, since the algebraic numbers form acountable set, while theset ofreal numbers and the set ofcomplex numbers are bothuncountable sets, and therefore larger than any countable set.
Alltranscendental real numbers (also known asreal transcendental numbers ortranscendental irrational numbers) areirrational numbers, since allrational numbers are algebraic.[3][4][5][6] Theconverse is not true: Not all irrational numbers are transcendental. Hence, the set of real numbers consists of non-overlapping sets of rational,algebraic irrational, and transcendental real numbers.[3] For example, thesquare root of 2 is an irrational number, but it is not a transcendental number as it is aroot of the polynomial equationx2 − 2 = 0. Thegolden ratio (denoted or) is another irrational number that is not transcendental, as it is a root of the polynomial equationx2 −x − 1 = 0.
The name "transcendental" comes from Latin trānscendere'to climb over or beyond, surmount',[7] and was first used for the mathematical concept inLeibniz's 1682 paper in which he proved thatsinx is not analgebraic function ofx.[8]Euler, in the eighteenth century, was probably the first person to define transcendentalnumbers in the modern sense.[9]
Johann Heinrich Lambert conjectured thate andπ were both transcendental numbers in his 1768 paper proving the numberπ isirrational, and proposed a tentative sketch proof thatπ is transcendental.[10]
Joseph Liouville first proved the existence of transcendental numbers in 1844,[11] and in 1851 gave the first decimal examples such as theLiouville constant
in which thenth digit after the decimal point is1 ifn =k! (kfactorial) for somek and0 otherwise.[12] In other words, thenth digit of this number is 1 only ifn is one of1! = 1, 2! = 2, 3! = 6, 4! = 24, etc. Liouville showed that this number belongs to a class of transcendental numbers that can be more closely approximated byrational numbers than can any irrational algebraic number, and this class of numbers is called theLiouville numbers. Liouville showed that all Liouville numbers are transcendental.[13]
The first number to be proven transcendental without having been specifically constructed for the purpose of proving transcendental numbers' existence wase, byCharles Hermite in 1873.
In 1874Georg Cantor proved that the algebraic numbers are countable and the real numbers are uncountable. He also gavea new method for constructing transcendental numbers.[14] Although this was already implied by his proof of the countability of the algebraic numbers, Cantor also published a construction that proves there are as many transcendental numbers as there are real numbers.[a]Cantor's work established the ubiquity of transcendental numbers.
In 1882Ferdinand von Lindemann published the first complete proof thatπ is transcendental. He first proved thatea is transcendental ifa is a non-zero algebraic number. Then, sinceeiπ = −1 is algebraic (seeEuler's identity),iπ must be transcendental. But sincei is algebraic,π must therefore be transcendental. This approach was generalized byKarl Weierstrass to what is now known as theLindemann–Weierstrass theorem. The transcendence ofπ implies that geometric constructions involvingcompass and straightedge only cannot produce certain results, for examplesquaring the circle.
In 1900David Hilbert posed a question about transcendental numbers,Hilbert's seventh problem: Ifa is analgebraic number that is not 0 or 1, andb is an irrational algebraic number, isab necessarily transcendental? The affirmative answer was provided in 1934 by theGelfond–Schneider theorem. This work was extended byAlan Baker in the 1960s in his work on lower bounds for linear forms in any number of logarithms (of algebraic numbers).[16]
A transcendental number is a (possibly complex) number that is not the root of any integer polynomial. Every real transcendental number must also beirrational, since everyrational number is the root of some integer polynomial ofdegree one.[17] The set of transcendental numbers isuncountably infinite. Since the polynomials with rational coefficients arecountable, and since each such polynomial has a finite number ofzeroes, thealgebraic numbers must also be countable. However,Cantor's diagonal argument proves that the real numbers (and therefore also thecomplex numbers) are uncountable. Since the real numbers are the union of algebraic and transcendental numbers, it is impossible for bothsubsets to be countable. This makes the transcendental numbers uncountable.
Norational number is transcendental and all real transcendental numbers are irrational. Theirrational numbers contain all the real transcendental numbers and a subset of the algebraic numbers, including thequadratic irrationals and other forms of algebraic irrationals.
Applying any non-constant single-variablealgebraic function to a transcendental argument yields a transcendental value. For example, from knowing thatπ is transcendental, it can be immediately deduced that numbers such as,,, and are transcendental as well.
However, analgebraic function of several variables may yield an algebraic number when applied to transcendental numbers if these numbers are notalgebraically independent. For example,π and(1 −π) are both transcendental, butπ + (1 −π) = 1 is not. It is unknown whethere +π, for example, is transcendental, though at least one ofe +π andeπ must be transcendental. More generally, for any two transcendental numbersa andb, at least one ofa +b andab must be transcendental. To see this, consider the polynomial(x −a)(x −b) =x2 − (a +b)x +a b . If (a +b) anda b were both algebraic, then this would be a polynomial with algebraic coefficients. Because algebraic numbers form analgebraically closed field, this would imply that the roots of the polynomial,a andb, must be algebraic. But this is a contradiction, and thus it must be the case that at least one of the coefficients is transcendental.
AllLiouville numbers are transcendental, but not vice versa. Any Liouville number must have unbounded partial quotients in itssimple continued fraction expansion. Using acounting argument one can show that there exist transcendental numbers which have bounded partial quotients and hence are not Liouville numbers.
Using the explicit continued fraction expansion ofe, one can show thate is not a Liouville number (although the partial quotients in its continued fraction expansion are unbounded).Kurt Mahler showed in 1953 thatπ is also not a Liouville number. It is conjectured that all infinite continued fractions with bounded terms, that have a "simple" structure, and that are not eventually periodic are transcendental[18] (in other words, algebraic irrational roots of at least third degree polynomials do not have apparent pattern in their continued fraction expansions, since eventually periodic continued fractions correspond to quadratic irrationals, seeHermite's problem).
TheDottie numberd (thefixed point of the cosine function) – the unique real solution to the equation, wherex is in radians (by the Lindemann–Weierstrass theorem).[21]
ifa is algebraic and nonzero, for any branch of theLambert W function (by the Lindemann–Weierstrass theorem), in particular theomega constantΩ.
if botha and the orderr are algebraic such that, for any branch of the generalized Lambert W function.[22]
, thesquare super-root of any natural number is either an integer or transcendental (by the Gelfond–Schneider theorem).
Values of thegamma function of rational numbers that are of the form or.[23]
Algebraic combinations ofπ and or ofπ and such as thelemniscate constant (following from their respective algebraic independences).[19]
The values ofBeta function if and are non-integer rational numbers.[24]
TheBessel function of the first kind, its first derivative, and the quotient are transcendental whenν is rational andx is algebraic and nonzero,[25] and all nonzero roots of and are transcendental whenν is rational.[26]
Numbers which have yet to be proven to be either transcendental or algebraic:
Most nontrivial combinations of two or more transcendental numbers are themselves not known to be transcendental or even irrational:eπ,e +π,ππ,ee,πe,π√2,eπ2. It has been shown that bothe +π andπ/e do not satisfy anypolynomial equation of degree≤ 8 and integer coefficients of average size 109.[48][49] At least one of the numbersee andee2 is transcendental.[50] Since the field of algebraic numbers is algebraically closed ande andπ are roots of the polynomialx2 - (e +π)x +eπ, at least one of the numberseπ ande +π is transcendental.Schanuel's conjecture would imply that all of the above numbers are transcendental andalgebraically independent.[51]
The values of theRiemann zeta functionζ(n) at odd positive integers; in particularApéry's constantζ(3), which is known to be irrational. For the other numbersζ(5),ζ(7),ζ(9), ... even this is not known.
Values of theGamma FunctionΓ(1/n) for positive integers and are not known to be irrational, let alone transcendental.[56][57] For at least one the numbersΓ(1/n) andΓ(2/n) is transcendental.[24]
Any number given by some kind oflimit that is not obviously algebraic.[57]
Assume, for purpose offinding a contradiction, thate is algebraic. Then there exists a finite set of integer coefficientsc0,c1, ...,cn satisfying the equation:It is difficult to make use of the integer status of these coefficients when multiplied by a power of the irrationale, but we can absorb those powers into an integral which “mostly” will assume integer values. For a positive integerk, define the polynomialand multiply both sides of the above equation byto arrive at the equation:
By splitting respective domains of integration, this equation can be written in the formwhereHereP will turn out to be an integer, but more importantly it grows quickly withk.
This would allow us to compute exactly, because any term of can be rewritten asthrough achange of variables. HenceThat latter sum is a polynomial in with integer coefficients, i.e., it is a linear combination of powers with integer coefficients. Hence the number is a linear combination (with those same integer coefficients) of factorials; in particular is an integer.
Smaller factorials divide larger factorials, so the smallest occurring in that linear combination will also divide the whole of. We get that from the lowest power term appearing with a nonzero coefficient in, but this smallest exponent is also themultiplicity of as a root of this polynomial. is chosen to have multiplicity of the root and multiplicity of the roots for, so that smallest exponent is for and for with. Therefore divides.
To establish the last claim in the lemma, that is nonzero, it is sufficient to prove that does not divide. To that end, let be anyprime larger than and. We know from the above that divides each of for, so in particular all of thoseare divisible by. It comes down to the first term. We have (seefalling and rising factorials)and those higher degree terms all give rise to factorials or larger. HenceThat right hand side is a product of nonzero integer factors less than the prime, therefore that product is not divisible by, and the same holds for; in particular cannot be zero.
Choosing a value ofk that satisfies both lemmas leads to a non-zero integer added to a vanishingly small quantity being equal to zero: an impossibility. It follows that the original assumption, thate can satisfy a polynomial equation with integer coefficients, is also impossible; that is,e is transcendental.
A similar strategy, different fromLindemann's original approach, can be used to show that thenumberπ is transcendental. Besides thegamma-function and some estimates as in the proof fore, facts aboutsymmetric polynomials play a vital role in the proof.
For detailed information concerning the proofs of the transcendence ofπ ande, see the references and external links.
^Cantor's construction builds aone-to-one correspondence between the set of transcendental numbers and the set of real numbers. In this article, Cantor only applies his construction to the set of irrational numbers.[15]
^Weisstein, Eric W."Dottie Number".Wolfram MathWorld. Wolfram Research, Inc. Retrieved23 July 2016.
^Mező, István; Baricz, Árpád (June 22, 2015). "On the generalization of the Lambert W function".arXiv:1408.3999 [math.CA].
^Chudnovsky, G. (1984).Contributions to the theory of transcendental numbers. Mathematical surveys and monographs (in English and Russian). Providence, R.I: American Mathematical Society.ISBN978-0-8218-1500-7.
^Murty, M. Ram (2013), "The Fibonacci zeta function", in Prasad, D.; Rajan, C. S.; Sankaranarayanan, A.; Sengupta, J. (eds.),Automorphic representations andL-functions, Tata Institute of Fundamental Research Studies in Mathematics, vol. 22, Tata Institute of Fundamental Research, pp. 409–425,ISBN978-93-80250-49-6,MR3156859
^Yoshinaga, Masahiko (2008-05-03). "Periods and elementary real numbers".arXiv:0805.0349 [math.AG].
^Weisstein, Eric W."Rabbit Constant".mathworld.wolfram.com. Retrieved2023-08-09.
^Allouche, Jean-Paul; Cosnard, Michel (2000), "The Komornik–Loreti constant is transcendental",American Mathematical Monthly,107 (5):448–449,doi:10.2307/2695302,JSTOR2695302,MR1763399
Burger, Edward B.; Tubbs, Robert (2004).Making transcendence transparent. An intuitive approach to classical transcendental number theory.Springer.ISBN978-0-387-21444-3.Zbl1092.11031.
Calude, Cristian S. (2002).Information and Randomness: An algorithmic perspective. Texts in Theoretical Computer Science (2nd rev. and ext. ed.).Springer.ISBN978-3-540-43466-5.Zbl1055.68058.
Lambert, J.H. (1768). "Mémoire sur quelques propriétés remarquables des quantités transcendantes, circulaires et logarithmiques".Mémoires de l'Académie Royale des Sciences de Berlin:265–322.
Pytheas Fogg, N. (2002).Berthé, V.; Ferenczi, Sébastien; Mauduit, Christian; Siegel, A. (eds.).Substitutions in dynamics, arithmetics and combinatorics. Lecture Notes in Mathematics. Vol. 1794.Springer.ISBN978-3-540-44141-0.Zbl1014.11015.
Shallit, J. (15–26 July 1996). "Number theory and formal languages". InHejhal, D.A.; Friedman, Joel;Gutzwiller, M.C.;Odlyzko, A.M. (eds.).Emerging Applications of Number Theory. IMA Summer Program. The IMA Volumes in Mathematics and its Applications. Vol. 109. Minneapolis, MN:Springer (published 1999). pp. 547–570.ISBN978-0-387-98824-5.
Fritsch, R. (29 March 1988).Transzendenz vone im Leistungskurs? [Transcendence ofe in advanced courses?](PDF). Rahmen der 79. Hauptversammlung des Deutschen Vereins zur Förderung des mathematischen und naturwissenschaftlichen Unterrichts [79th Annual, General Meeting of the German Association for the Promotion of Mathematics and Science Education].Der mathematische und naturwissenschaftliche Unterricht (in German). Vol. 42. Kiel, DE (published 1989). pp. 75–80 (presentation), 375–376 (responses). Archived fromthe original(PDF) on 2011-07-16 – viaUniversity of Munich (mathematik.uni-muenchen.de ). — Proof thate is transcendental, in German.