Plane Partition

DOWNLOAD Mathematica Notebook

A plane partition is a two-dimensional array of integers n_(i,j) that are nonincreasing both from left to right and top to bottom and that add up to a given number n. In other words,

 n_(i,j)>=n_(i,j+1)
(1)
 n_(i,j)>=n_(i+1,j)
(2)

and

 n=sum_(i,j)n_(i,j).
(3)

Implicit in this definition is the requirement that the array be flush on top and to the left and contain no holes.

PlanePartition
 5 4 2 1 1; 3 2   ; 2 2
(4)

For example, one plane partition of 22 is illustrated above.

The generating function for the number PL(n) of planar partitions of n is

 sum_(n=0)^inftyPL(n)x^n=1/(product_(k=1)^(infty)(1-x^k)^k)=1+x+3x^2+6x^3+13x^4+24x^5+...
(5)

(OEIS A000219, MacMahon 1912b, Speciner 1972, Bender and Knuth 1972, Bressoud and Propp 1999).

Writing a(n)=PL(n), a recurrence equation for a(n) is given by

 a(n)=1/nsum_(k=1)^na(n-k)sigma_2(k),
(6)

where sigma_k(n) is a divisor function. It also has generating function

 G(x)=exp[sum_(n=1)^inftysigma_2(n)(x^n)/n].
(7)

MacMahon (1960) also showed that the number PL(a,b,c) of plane partitions whose Young tableaux fit inside an a×b rectangle and whose integers do not exceed c (in other words, with all n_(i,j)<=c) is given by

 PL(a,b,c)=product_(i=1)^aproduct_(j=1)^bproduct_(k=1)^c(i+j+k-1)/(i+j+k-2)
(8)

(Bressoud and Propp 1999, Fulmek and Krattenthaler 2000). Expanding out the products gives

PL(a,b,c)=product_(i=1)^(a)(Gamma(i)Gamma(b+c+i))/(Gamma(b+i)Gamma(c+i))
(9)
=(G(a+1)G(b+1)G(c+1)G(a+b+c+1))/(G(a+b+1)G(a+c+1)G(b+c+1)),
(10)

where G(n) is the Barnes G-function. Taking n=a=b=c gives

PL(n,n,n)=product_(i=1)^(n)(Gamma(i)Gamma(i+2n))/([Gamma(i+n)]^2)
(11)
=([G(n+1)]^3G(3n+1))/([G(2n+1)]^3),
(12)

the first few terms of which are 2, 20, 980, 232848, 267227532, 1478619421136, ... (OEIS A008793). Amazingly, PL(a,b,c) also gives the number of hexagon tilings by rhombi for a hexagon of side lengths a, b, c, a, b, c (David and Tomei 1989, Fulmek and Krattenthaler 2000).

The concept of planar partitions can also be generalized to cubic partitions.

Wolfram Web Resources

Mathematica »

The #1 tool for creating Demonstrations and anything technical.

Wolfram|Alpha »

Explore anything with the first computational knowledge engine.

Wolfram Demonstrations Project »

Explore thousands of free applications across science, mathematics, engineering, technology, business, art, finance, social sciences, and more.

Computerbasedmath.org »

Join the initiative for modernizing math education.

Online Integral Calculator »

Solve integrals with Wolfram|Alpha.

Step-by-step Solutions »

Walk through homework problems step-by-step from beginning to end. Hints help you try the next step on your own.

Wolfram Problem Generator »

Unlimited random practice problems and answers with built-in Step-by-step solutions. Practice online or make a printable study sheet.

Wolfram Education Portal »

Collection of teaching and learning tools built by Wolfram education experts: dynamic textbook, lesson plans, widgets, interactive Demonstrations, and more.

Wolfram Language »

Knowledge-based programming for everyone.