Some Favourite Mathematical Constants

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Mathematical constant are really exciting and wonderful in the world of numbers. All numbers are not created equal; that certain constants appear at all and then echo throughout mathematics, in seemingly independent ways, is a source of fascination. Just as physical constants provide “boundary conditions” for the physical universe, mathematical constants somehow characterize the structure constants, the Archimedes’ constant pi (pi) was once regarded as the king, and in modern times (after 1980), the Feigenbaum Universal constant delta=4.6692016091029dots is regarded as the ‘Super King’ in this field on the basis of its increasing importance and tremendous uses in mathematical sciences, physics, chemistry, biosciences, economics, engineering etc.

The constants listed below are rather arbitrarily organized by topicwise. The concrete elaboration of how these constants are derived needs a long discussion, and hence detailed discussion is intentionally omitted. Interested readers are requested to contact the author for details of any constant. However, how the Feigenbaum Universal constant can be obtained is very briefly highlighted below with the help of a simple example.

Let f(x)=ax(1-x), where a is a constant. The interval [0,1] is mapped into itself by f for each value of ain [0,4]. This family of functions, parameterized by a, is known as the family of logistic maps. What are the 1-cycles (i.e. fixed points) of f? Solving x=f(x) we obtain

x=0 (which attracts for a<1 and repels for a>1),

and x=frac{a-1}{a} (which attracts for 1<a<3 and repels for a>3).

What are the 2-cycles of f? That is, what are the fixed points of the iterate f^{2} which are not fixed points of f? Solving x=f^{2}(x), xneq f(x), we obtain the 2-cycle.

x=frac{a+1pm (a^{2}-2a-3)^{frac{1}{2}}}{2a} (which attracts for 3<a<1+sqrt{6} and repels for  a>1+sqrt{6}).

For a>1+sqrt{6}=3.4495dots an attracting 4-cycle emerges. We can obtain the 4-cycle by numerically solving x=f^{4}, and xneq f^{2}. It can be shown that 4-cycle attracts for 3.4495….<a<3.5441…., and repels for a>3.5441…..

For a>3.5441…., an attracting 8-cycle emerges. We can obtain the 8-cycle by numerically solving x=f^{8}, and xneq f^{4}. It can be shown that 8-cycle attracts for 3.5441….<a<3.5644…., and repels for a>3.5644…..

For how long does the sequence of period doubling bifurcations continue? It’s interesting that this behavior stops for short of 4. Setting a_{0}=1,a_{1}=3,a_{2}=1+sqrt{6}=3.4495dots , a_{3}=3.5441dots ,a_{4}=3.5644dots , and so forth denote the cascade of bifurcations, it can be proved that

a_{infty}=lim_{infty}a_{n}=3.5699dots <4.0

This point marks the separation between the “periodic regime” and the “chaotic regime” for this family of quadratic functions. The sequence {a_{n}} behaves in a universal manner such that the ratio frac{a_{n}-a_{n-1}}{a_{n+1-a_{n}}} tends to a universal constant delta =4.6692016091029dots .

The elementary particle theorist, Mitchell J. Feigenbaum working in the University of Princeton, U.S.A, has explain in details the creation of this constant in his two marvelous papers.

(i) Quantitative Universality for a class of Nonlinear Transformations, J. of Statistical Physics, 19:1(1978), 25-52.

(ii) The Universal Metric Properties of Nonlinear Transformations, J. of Statistical Physics, 21:6(1979), 669-706.

Favourite Mathematical constants so far we know are listed bellow with their approximate numerical values:


Well-known constants

Numerical Value

1 Zero 0
2 One 1
3 Imaginary unit sqrt{-1}
4 Pythagoras’ constant sqrt{2}
5 Golden mean phi=1.6180339887dots
6 Natural logarithmic base C=2.7182818285….
7 Archimedes’ constant pi=3.14159265358979dots
8 Euler-Mascheroni constant gamma=0.5772156649dots
9 Ape’’ry’s constant zeta(3)=1.202056903dots
10 Catalan’s constant G=0.915965594….
11 Khintchine’s constant K=2.68545200….
12 Feigenbaum constant delta=4.6692016091029dots
13 Madelung’s constant M_{2}=-1.6155426267dots
14 Chaiten’s constant Not available


Constants associate with Number Theory

15 Hardy-Littlewood constant C_{twin}=0.6601618158dots
16 Hadamard-de la Valle’e Poussin constant C_{1}=0.2614972128dots
17 Landau-Ramanujan constant K=0.764223653….
18 Brun’s constant B=1.90211605778….
19 Artin’s constant C_{Artin}=0.3739558136dots
20 Linnik’s constant Not available
21 Hafner-Sarnak-MeCurley constant D_{infty}=0.3532363719dots
22 Gauss-Kuzmin-Wirsing constant lambda=0.3036630029dots
23 Stolarsky-Harborth constant Theta=1.58496dots
24 Porter’s constant C=1.4670780794….
25 Glaisher-Kinkelin constant A=1.28242713….
26 Franse’n-Robinson constant   2.8077702420….
27 Allodi-Grnstead constant   0.809394020534….
28 Niven’s constant constant C=1.705211….
29 Backhouse’s constant   1.456074485826….
30 Mill’s constant C=1.3064….
31 Stieltjes constant gamma_{0}=0.5772156649dots
32 Liouville-Roth constant   0.0110001000….
33 Diophantine approximation constant gamma_{1}=0.4472135955dots
34 Erdos reciprocal sum constant   3.0089
35 Abundant number density constant   0.2441<A<0.2909
36 Self-number density constant lambda=0.252660259dots
37 Cameron’s sum-free set constant 0.21759<c<0.21862
38 Euler totient function asymptotic constant A=1.9435964368….B=-0.0595536246….
39 Nielson-Ramanujan constant Not available
40 Triple-free set constant 0.6135752692….
41 De-Bruijn-Newman constant Not yet available
42 Freiman’s constant Not yet available
43 Cahen’s constant Not yet available


Constants associate with Analytic Inequalities

44 Shapiro’s cycle sum constant 0.4945668….
45 Carlson-Levin constant Gammafrac{1/4}{pi ^{1/4}}
46 Londau-Kolmogorov constant C(3,1)=(frac{243}{8})^{1/3}
47 Hilbert’s constant Not available
48 Copson-de-Bruijn constant C=1.1064957714….
49 Wirtinger-Sobolev isoperimetric constant Not available
50 Whitney-Mikhlin extension constant 2.05003


Constants associate with the Approximation of Functions

51 Wilbraham Gibbs constant G=1.851937052….
52 Lebesgue constant C=0.9894312738….
53 Favard constant Not available
54 Bernstein’s constant beta=0.2801694990dots
55 The “one-ninth” constant   0.1076539192….
56 Laplace limit constant lambda=0.6627434193dots


Constants associate with Enumerating Discrete structures

57 Abelian group enumeration constant A=2.2948566…. , B=1.3297682….
58 R’enyi’s parking constant   0.7475979203….
59 Golomb Dickman constant lambda=0.6243299885dots
60 Lengyel’s constant lambda=1.0986858055dots
61 Otter’s tree enumeration constant beta=0.5349485dots
62 Polya’s random walk constant rho=0.3405373296dots
63 Self-avoiding-walk connective constant 2.6381585….
64 Feller’s coin tossing constant alpha=1.087378025dots ,beta=1.236839845dots
65 Har square entropy constant k=1.503048082….
66 Binary search tree constant Precise numerical value not available
67 Digital search tree constant c=0.3720486812….
68 Quardtree constant C=4.3110704070….
69 Extreme value constant mu_{6}=1.2672063606dots
70 Pattern-free word constant varsigma=1.302dots
71 Takeuchi-Prellberg constant c=2.239433104….
72 Random percolation constant K_{B}=0.0355762113dots
73 Lenz-Ising constant rho=0.218094dots
74 2D Monomer-dimer constant   1.338515152….
75 3D Dimer constant lambda=0.209174dots
76 Lieb’s square ice constant Not yet available


Constants associate with Functional Iteration

77 Gauss’s lemniscate constant 0.83462684167….
78 Grossman’s constant Not available
79 Plouffe’s constant 0.4756260767….
80 Lehmer’s constant 0.5926327182….
81 Iterated exponential constant -0.7666646959….
82 Continued fraction constant 0.76519769…., 0.7098034428….
83 Infinite product constant 2.0742250447….
84 Quadratic recurrence constant C=1.502836801….
85 Conway’s constant lambda=1.303577269dots


Constants associate with Complex Analysis

86 Bloch-Landau constant B=0.4718617….L=0.5432588….
87 Masser-Gramain constant C=0.6462454398….
88 John constant   4.810477….


Constants associate with Geometry

89 Geometric probability constant   4.2472965….
90 Circular coverage constant   0.8269933431….
91 Universal coverage constant Not yet available
92 Hermite’s constant   0.7404804897….
93 Tammes’ constant Not yet available
94 Calabi’s triangle constant 1.5513875245….
95 Graham’s hexagon constant 0.6495190528….
96 Traveling salesman constant 0.521….
97 Moving sofa constant A=0.09442656084….
98 Beam detection constant 5.1415926536….
99 Heilbronn Triangle constant H=0.1924500897….
100 Moser’s worm constant Not yet available
101 Rectilinear crossing constant 0.70449881….
102 Maximum irrodius constant 0.2041241452….
103 Magic geometric constant 0.6675276<m<0.6675284


Almost all the constants seem to be irrationals although rigorous proofs are not available. All the constants have numerous fascinating applications, and thus irrational numbers play very important role in studying modern number theory. Details of some interesting constants and some of their applications will be highlighted in ‘Ganit Bikash’ in near future.


Author Prof. Tarini Kumar Dutta is a Professor in Mathematics Department, Gauhati University.

[This article was first published in Ganit Bikash, Volume 27, June-December, 2000.]


Managing Editor of the English Section, Gonit Sora and Research Fellow, Faculty of Mathematics, University of Vienna.


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