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Encyclopedia Britannica - Main :: DRO-ECG |
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DX1(X1a2As...) _ (a2xa...), while D,(ai)sa3..) =o unless the partition
part
and the operations are evidently commutative. Also DPiDmDPB..(p;1p2ap33...) =1, and the law of operation of the operators D upon a monomial symmetric function
1+D1+2D2 +3D3+... =exppol where exp denotes (by the rule
so that we are only concerned with the successive performance of linear operations. For this purpose write a1 =a,+a1aa,+1+a2aaa}2+.... It has been shown (vide " Memoir on Symmetric Functions of the Roots of Systems of Equations," Phil. Trans. 189o, p. 490) that exp(midi+m2d2+m3d3+...) =exp(M1d1+M2d2+Msda+...), where now the multiplications on the dexter denote successive operations, provided thatexp(M1f;+M22+M3r,3+...) =1+mlt+mzt;2+mat3+...; being an undetermined algebraic quantity. Hence we derive the particular cases expol = exp(di zd2+5(13 ...) ; expadl = exp (dl -22d2+33d2 ...), and we can express D. in terms of d1, d2, d3,..., products denoting successive operations, by the same law which expresses the elementary function
powers
power function s, in terms of the elementary functions al, a2, a3,...Operation of Da upon a Product of Symmetric Functions.Suppose f to be a product of symmetric functions flf2.. f . If in the identity f =f, f2...fm we introduce a new root we change as into a1+/as1, and we obtain(1 +D1+2D2+... +'Da+...)f = (1-}-D1+112D2+.:.+'Da+...)f1 X (1 +D1+2D2+...+'Da+...) f2 X. X (1+11D3+112D2++'Da+)fm, and now expanding and equating coefficients of like powers
D2f =x(D2f1)f2f3...f +(Dlfl) (D1f2)f3... fm, D3f =E(D3f1)f2f3...fm+ (D3f1)(Dlf2)f3...fm+(D3f1)f2fs...fm, the summation in a term
term
Writing these results D1f = D(nf, D2f = D(2)f+Du2)f, D3f = D<3)f+D(21)f+Da3)f, et B.,(ml,muemst, ) 1, z, a, we may write in general De f =ED(plp2p3e.).f, the summation being for every partition (plp2p3...) of s, and D(ptp2p3...)f being =E(Dpl.fl)(Dp2.f2)(DP3f3)f+...fm. Ex. gr. To operate with D2 upon (213)(214)(15), we have D(2)fy' = (13) (Z14) (15) +(213) (14) (15). Dc12).f = (122) (2P) (15) +(213) (213) (14) +(212) (214) (14), and hence D2f = (214) (15) (13) + (213) (15) (14) +(213) (212) (15) + (213)2 (14) +(214) (212) (14). Application.to Symmetric Function Multiplication.An example will explain this. Suppose we wish to find the coefficient of (52413) in the product (213)(214)(15). Write (213) (214) (15) _... +A(524) (13) +... ; D,D2D7(213)(214)(15) =A; every other term disappearing by the fundamental property of D,. Since D,(213)(214)(15) =(13)(14)(14), we have: End of Article: DX1(X1a2As...) If you wish, you can link directly to this article.
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