: ( ) 2008 5 31 1 f(t) t (1) d 2 f(t) + f(t) = 0 dt2 f(t) = sin t f(t) = cos t (1) 1 (2) d dt f(t) + f(t)2 = 0 (1) (2) t (c ) (3) 2 2 u(t, x) c2 u(t, x) = 0 t2 x2 1 (1) (1) 1
t, x (4) 3 u(t, x) + 6u(t, x) u(t, x) + u(t, x) = 0 t x x3 ( u x = u x (4) u t + 6uu x + u xxx = 0 ) ( ): ( ) (2) Riccati ( ) 2008 4 ( ) ( ) 2 (1) : f 1 (t) f 2 (t) f(t) = a 1 f 1 (t) + a 2 f 2 (t) (a 1, a 2 ) f (t) a 1 f 1(t) + a 2 f 2(t) f(t) (1) ( ; ) (1) sin t cos t f(t) = a sin t + b cos t (a, b ) 2 2
( ) 3! 2 2.1 8 9 30 1 1.5 1834 John Scott-Russel ( - ) 4 Union Canal 1995 http://www.ma.hw.ac.uk/solitons/press.html Scott-Russel (solitary wave; wave of translation ) ( ) 1882 Boussinesq ( ) 1895 Korteweg ( ) de Vries ( ) Newton ( ) 17 18 Euler ( ) Lagrange ( ) 19 Boussinesq Korteweg-de Vries Boussinesq Korteweg-de Vries 3 4 http://www.ma.hw.ac.uk/~chris/scott russell.html 3
u(x, t) x ( ) t u(x, t) 1 (3) c f(x) u(x, t) = f(x ct) u(x, t) = f(x + ct) (3) x c Scott-Russel u(x, t) Boussinesq Korteweg-de Vries Korteweg-de Vries ( KdV ) 1 (4) ( x, t u(x, t) ) KdV (k, δ ) (5) u(x, t) = 2k 2 sech 2( k(x ct) + δ ), c = 4k 2 sech x e x 2 sech x = sech x x = 0 1 x ± 0 e x + e x u(x, t) 2k 2 1 x t x ct c = 4k 2 x 5 KdV 4k 2 2k 2 x=ct x 1: KdV KdV Korteweg de Vries 5 Boussinesq Scott-Russel 4
2.2 KdV ( ) KdV ( ) E. Fermi ( ; ) 1 ( ) Fermi Pasta ( ), Ulam ( ) N. Zabusky ( ) M. D. Kruskal ( ) KdV (t = 0 u(x, t)) ( u(x, 0) = sin x) u(x, t) http://www.math.h.kyoto-u.ac.jp/~takasaki/soliton-lab/gallery/solitons/ ( 2, 3, 4 ) Korteweg-de Vries (solitary wave) -on ( electron, photon, proton ) Solitary wave + -on = SOLITON 5
2: KdV ; 3: KdV ; 6 2.3 Boussinesq : u(x, t) (6) 3 4 u tt + u xx + 1 4 u xxxx + 3 2 (uu x) x = 0. KdV : v(x, t) (7) v t + 6v 2 v x + v xxx = 0. KdV (4) KdV 6 solitron 6
KP 7 : u(x, y, t) (8) (u t + 6uu x + u xxx ) x + 3u yy = 0. KdV (4) KdV u(x, t) y (x, y, t) KP KP y 2 KdV Sine-Gordon : ( ) u(x, t) (9) u tt u xx + sin u = 0. sin u m 2 u m Klein-Gordon sine-gordon ( 4) x Sine-Gordon u(x, t) 4: Sine-Gordon 2- : t n ( ) u n (t) (10) u tt = e u n 1 u n e u n u n+1. [To1] 3 2.1 2.2 made in Japan 2.1 ( 4.1 ) ( Novikov ) ( 5.2 ) 7 Kadomtsev ( )-Petviashvili ( ) 7
3.1 Lax 1 Riccati (2) (11) f(t) = g (t) g(t) f(t) = d log g(t) f(t) g(t) g(t) = dt e R f(t) dt Riccati (2) (12) d 2 dt 2 g(t) = 0 g(t) = a 1 t + a 0 (a 0, a 1 ) Riccati (13) f(t) = a 1 a 1 t + a 0 KdV u xxx u xx Burgers u w x /w w KdV 1967 Miura ( ; ) w x /w w xx /w u = w xx /w w v = iw x /w (i = 1), (14) w xx + uw = 0, iw x + vw = 0 v v KdV (7) Gardener ( ), Greene ( ), Kruskal, Miura (GGKM ) w(x, t; λ) : (15) 2 x 2 w(x, t; λ) + u(x, t)w(x, t; λ) = λ2 w(x, t; λ) λ x t (15) ( ) Schrödinger ( ) ( t ; t ) u(x) w(x; λ) ( ) u(x) ( ) w(x; λ) ( u(x) w(x; λ) ) (16) x w(x; λ) = 1 a(λ) e iλx, x + w(x; λ) = e iλx + r(λ)e iλx 8
(a(λ), r(λ) λ ) e iλx e iλx λ w(x; λ) λ u(x) 1/ a(λ) r(λ) ( 5) 1/a(λ) r(λ) 8 u(x) e -i x e -i x u(x) e i x x 5: u(x) u(x) u(x) ( λ ) u(x) u(x)? Gelfand-Levitan(-Marchenko) ( ) u(x)! (M. Kac ( ) ) Schrödinger (15) KdV GGKM KdV u(x, t) Schrödinger (15) λ t ( ) t 1/a(λ) t r(λ, t) t r(λ, t) = r(λ, 0)e 8iλ3 t u(x, t) t = 0 u(x, 0) t 8 a(λ) λ c j, η j (j = 1,..., n; n u(x) ) r(λ) {r(λ), η 1,..., η n, c 1,..., c n } 9
u(x, t) u(x, 0) u(x, t) KdV! KdV (17) u(x, 0) a(λ), r(λ, 0) u(x, t) GLM a(λ), r(λ, t) = r(λ, 0)e 8iλ3 t r(λ, t) = 0 ( ) P. D. Lax ( ; 2007 ) λ Schrödinger (15) w(x, t; λ) L = 2 +u(x, t) x2 w λ ( ) x(t) w v(t) = y(t) ( ) a(t) b(t) L P (t) = v(t) c(t) d(t) P (t) P (t) λ t : (18) P (t)v(t) = λv(t) ( ) P (t) P (0) U(t) (19) P (t) = U(t)P (0)U(t) 1 P (t) U(t) U(t) A(t) ( ) d d (20) U(t) = A(t)U(t), A(t) = dt dt U(t) U(t) 1, (19) (21) d dt du(t) P (t) = P (0)U(t) 1 + U(t)P (0) d( U(t) 1) dt dt = du(t) U(t) 1 U(t)P (0)U(t) 1 + U(t)P (0) dt = A(t)P (t) P (t)a(t) ( U(t) ) 1 du(t) U(t) 1 dt 10
[A(t), P (t)] P (t) (22) d P (t) = [A(t), P (t)] dt L = 2 + u(x, t) ( x u(x, t) KdV L (23) t L = [A, L], A = 4 3 + 6u + 3u x, ) (L A 3 f(x) ) KdV (23) Lax L Lax (L, A) Lax (Lax pair) KdV KdV [TD] 3.2 KdV Sine-Gordon (RCA ) ([ ] ) (5) KdV Miura (14) KdV KdV f(x) : ( ) f f (f ) 2 f = = d2 log f. f 2 f dx2 f(x) = cosh x f (x) = sinh x, f (x) = cosh x 9 (5) (24) u(x, t) = 2 d2 dx 2 log cosh( k(x ct) + δ ) 2 ( 3 ) (1968 ; [To1] ) n ( n ) KdV Sine-Gordon ([ ] ): KdV f(x, t) (25) D x (D t + D 3 x)f f = 0 9 cosh x = ex + e x, sinh x = ex e x : 2 2 11
f(x, t) (26) u(x, t) = 2 2 log f(x, t) x2 u(x, t) KdV D : (27) D m x D n t f(x, t) g(x, t) := m x n t f(x + x, t + t )g(x x, t t ) x =t =0. x fg = f g + fg D x f g = f g fg, 2 xfg = f g + 2f g + fg D 2 xf g = f g 2f g + fg f (25) KdV v = x (log f) 1 f 2 D x(d t + D 3 x)f f = 2(v t + 6v 2 x + v xxx ) 0 0. x u = 2v x KdV KdV Sine-Gordon ( ) n (28) f(x, t) = 1 + εf (1) (x, t) + ε 2 f (2) (x, t) + u(x, t) 2 1 (28) f (1) 1 f (2) ( 3 ) f 4.1 ( ) (26) f ( ) [Hi] 12
4?? 1981 KP Grassmann 4.1 1970 Ising Lax (23) (t ) ( ): ( ) τ ([ ] ) ((25) D x, D t 4 ) ([ ] ) 10 ( ):? (1980 ) 420! ([ ] ) 10 n ; n = 3 3 = 2 + 1 = 1 + 1 + 1 3, n = 4 4 = 3 + 1 = 2 + 2 = 2 + 1 + 1 = 1 + 1 + 1 + 1 5. 13
( ) KdV Lax (23) Lax L 2 + u(x, t) (29) L = + u 2 1 + u 3 2 + = u n 1 n, (u 0 = 1, u 1 = 0) 1!?? n=0 Lax (23) KdV ( (22) ) n ( ) Lax [A, L] = AL LA ( )( f(x) m g(x) n) = m(m 1) (m r + 1) f(x)g (r) (x) m+n r r! r 0 m, n ( ) P = a n (x) n n P +, P (30) P + = n 0 a n (x) n, P = n<0 a n (x) n. 1970 Gelfand ( ), Dikii ( ), Manin ( ) Wilson ( ), Adler ( ) (29) Lax t 1, t 2,..., t n,... ( t ) u i x t u i (x, t) Lax (31) L t n = [B n, L], (n = 1, 2,... ). 14
B n L n B n = (L n ) + KP hierarchy, KP B n (32) B m t n B n t m + [B m, B n ] = 0, (m, n = 1, 2,... ) m = 2, n = 3 KP (8) (u 2 = u, t 1 = x, t 2 = y, t 3 = t, t n ; (8) ) KP Lax L (29) L 2 = 2 + 2u 2 + ( ) 0 KP u = 2u 2 KdV (t 1 = x, t 3 = t, t n ) KdV hierarchy, KdV ( 2 + u L ) L 2 L 3 Boussinesq KP Schrödinger (15) (33) (34) Lw(x, t; λ) = λw(x, t; λ), w(x, t; λ) = B n w(x, t; λ). t n (34) (33) L n (n = 1, 2,... ) w(x, t; λ) (35) w(x, t; λ) = (1 + w 1 (x, t)λ 1 + w 2 (x, t)λ 2 + )e xλ+ξ(t,λ), ξ(t, λ) = t n λ n, n e xλ+ξ(t,λ) = λ n e xλ+ξ(t,λ) (n 0 n ) (36) w(x, t; λ) = (1 + w 1 (x, t) 1 + w 2 (x, t) 2 + )e xλ+ξ(t,λ) n w(x, t; λ) Schrödinger (16) (35) 11 w(x, t; λ) τ(t) = τ(t 1, t 2,... ) ( ) τ t 1 + x λ 1, t 2 λ 2, t 2 3 λ 3,... 3 (37) w(x, t; λ) = e xλ+ξ(t,λ), τ(t 1 + x, t 2, t 3,... ) 11 (16) ±iλ (35) λ n=1 15
τ τ(t) f τ τ Schur ( ) Plücker ( ) KP Grassmann ( ) Grassmann ( ) Plücker Π ( 6) v = a 1 a 2 a 3 w = b 1 b 2 b 3 ( ) a 2 b 2 (38) αx + βy + γz = 0, α : β : γ = a 3 b 3 : a 1 b 1 : a 1 b 1 a 3 b 3 a 2 b 2 ( ) z v y w x 6: = GM(3; 2) (38) α : β : γ GM(3; 2) = {[α : β : γ] (α, β, γ) (0, 0, 0)} (α, β, γ 0 (38) ) 16
( (x, y, z, w) ) v = a 1 a 2 a 3 w = b 1 b 2 b 3 a 4 b 4 (39) 23 x 13 y + 12 z = 0, 24 x 14 y + 12 w = 0, 34 x 14 z + 13 w = 0, 34 y 24 z + 23 w = 0 12 ij a i b i (40) ij = = a ib j a j b i a j b j 12 : 13 : 14 : 23 : 24 : 34 GM(4; 2) GM(4; 2)? = {[ 12 : 13 : 14 : 23 : 24 : 34 ] ( 12,..., 34 ) (0, 0, 0, 0, 0, 0)} (39) (x, y, z, w) v, w (40) (41) 12 34 13 24 + 14 23 = 0, ( [Ha2] 12.4 ) ij ( 0 ) (39) { } ( 12,..., 34 ) (0,..., 0), (42) GM(4; 2) = [ 12 : : 34 ] 12 34 13 24 + 14 23 = 0 N m Grassmann GM(N; m) ( m ) (38) (39) N C m (N m ) Plücker Plücker (41) Plücker ( N, m ) GM( ; 2 ) Grassmann 13 Grassmann Grassmann Plücker 12 v, w 13 (..., x 2, x 1, x 0, x 1, x 2,... ) x 0 = x 1 = x 2 = = 0 17
(ξ λ ) λ: GM(4, 2) (42) Plücker ij (i, j) = (1, 2),..., (3, 4) (43) (ξ λ ) λ: = (ξ φ, ξ 1, ξ 2, ξ }{{ 1,1, ξ } 3, ξ 2,1, ξ 1,1,1, }{{} 2 3... ) ( φ 0 ) λ Schur t = (t 1, t 2, t 3,... ) s λ (t) ( [MJD] 9.3 ) Schur s φ (t) = 1, s 1 (t) = t 1, s 2 (t) = t2 1 2 + t 2, s 1,1 (t) = t2 1 2 t 2, s 3 (t) = t3 1 6 + t 1t 2 + t 3, s 2,1 (t) = t3 1 3 t 3, s 1,1,1 (t) = t3 1 6 t 1t 2 + t 3. λ n s λ (t) n t n n t = (t 1, t 2, t 3,... ) ( ) s λ (t) ( ) KP τ τ(t) Schur (44) τ(t) = λ: ξ λ s λ (t) (ξ λ ) λ: Plücker Grassmann (ξ λ ) λ Grassmann Plücker (44) KP τ KP Grassmann Schur ξ λ τ(t) Plücker τ(t) ( )! 1 Grassmann [SN] [SU] 18
4.2 Grassmann Grassmann KP hierarchy Grassmann KP Grassmann Grassmann GM(N; m) GM(N; m) N m GM(3; 2) 6 3 3 a 11 a 12 a 13 x a 11 x + a 12 y + a 13 z a 21 a 22 a 23 y = a 21 x + a 22 y + a 23 z a 31 a 32 a 33 z a 31 x + a 32 y + a 33 z ( ) GM(3; 2) (= ) GM(3; 2) 3 3 (GL(3) GL 3 ) GM(3; 2) GL(3) ( = ) Grassmann GM(N; m) N N GL(N) Grassmann GL( ) ( ) Lie ( ) ( Lie ) Lie Lie 1960 Lie ( ) ( KP ) GL( ) ( ) Grassmann KP KP GL( ) 14 n n + 1 τ(t) = 1 τ (= 0 ) 14 19
( ) Ising ( ) τ Lie Noether ( ) KP ( ) Liouville ( )-Arnold ( ) KP ( 1970 [W] ) [MJD] 5 1981 ( ) ( ) 5.1 [ ] 1970 ( Schrödinger ) 1980 [Ha1] ( ) 1970 20
([Sh]) 2000 5.2 KP ( ) GL( ) ( Lie ) 1980 Novikov : 3 ( ) KP (8) τ KP τ KP : U(1) KP τ Witten : KP ( KdV ) τ (45) Z N (t) = X: N e β tr (t 1 X+t 2 X 2 +t 3 X 3 + ) dx (46) Z N (Λ) = e tr (X 3 +ΛX) dx, X: N Λ : dx X N ( ) X N τ ( (46) t n = 1 n tr Λn KP ) (46) ( ) KdV τ Witten ( ) 1998 M. Kontsevich ( ) 21
5.3? = 1. 2. 7! 7: 1990 KdV 15 16 ( ; ) 15 V. Drinfeld 1985 16 22
( ) : http://www.rkmath.rikkyo.ac.jp/~kakei/books.html [To2], [To3] ( ) 2 3 [SN], [MJD], [Ta] [SU] [U] [ ],,, :, 13, 14, (1999);,, (2007). [ ], (1985). [ ] [Ha1] :,, 4, (,, ) 19-56, (1982). : 17, 51, 806-809 (1996). [Ha2] :, (2004). [Hi] :, (1992). [MJD],, :, [ 4] (1993); ( ) (2007). [Sh] [SN] [SU] :, 1983 8,., :, 18 (1984).,, 5, (1989). [Ta] :, (2001) [TD], : KdV, 16 (1979) 17 http://wwwsoc.nii.ac.jp/jps/jps/butsuri/50th/noframe/50(3)/50th-p806.html 23
[To1] : 18 51, 185 188, (1996) [To2] : 30, 30 3, (1999). [To3] : ( ), (2000). [U] :, 4 (1993). [W] :, 14 (1992) 18 http://wwwsoc.nii.ac.jp/jps/jps/butsuri/50th/noframe/50(3)/50th-p185.html 24