kinko

59
【論 説】 わかった気になる?一般均衡理論 ―ブラウワーの不動点定理の証明付き― 田 中 靖 人 1 はじめに 2 スペルナーの補題(2 次元の場合) 3 スペルナーの補題(一般の場合) 4 ブラウワーの不動点定理 5 交換経済における均衡の存在 6 宇沢の定理 7 企業の生産を含む経済の均衡について 8 付録 1 :コンパクト集合とその性質 9 付録 2 :関数の連続性 10 付録 3 :直積集合における開集合 11 補論 :ユークリッド空間の一般理論 11.1  ユークリッド空間と距離 11.2  距離空間 11.3  位相空間 11.4  閉集合 11.5  ハウスドルフ空間 11.6  ユークリッド空間のコンパクト集合に関する一般的な議論 11.7  点列と収束,関数の最大・最小 11.8  近傍,閉包,内部 11.9  完備距離空間 * 本稿の執筆にあたっては,平成 18 年度私立大学等経常費補助金特別補助高度化推進特別経 費大学院重点特別経費(研究科分),および科学研究費補助金(基盤研究 C(一般),課題番号 16530128)の助成を受けた.厚く感謝する. 243

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    11

    11.1

    11.2

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    11.4

    11.5

    11.6

    11.7

    11.8

    11.9

    18 C16530128

    243

  • 59 3

    1

    3

    X0, X1, , Xn n1(n 1)

    pi( 0), i0, 1, , n p0p1+pn

    ipii0, 1, , n

    0, 1, , n p0, p1, , pn

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    p0 x0p1 x1pn xn 0

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    244

  • 3 X, Y, Z, px , py , pz

    1 px , py , pz 3

    (1, 0, 0), (0, 1, 0), (0, 0, 1)

    2 1

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    (0,1,0)(1,0,0)

    px py

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    245

  • 59 3

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    1 p0, p1, , pn n 1 (1,

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    6

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    K K K

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    246

  • 2

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    12 K 1

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    247

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    248

  • K 12

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    n n

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    n1 (1, 0, 0, , 0), (0, 1, , 0), , (0, 0, , 1)

    n 0 1

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    1 42

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    249

  • 59 3

    2 K v n1 n1

    v v

    3 K v n2

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    K n 0

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    01n1 n1

    1 2

    K n

    0 n1 K n1

    2 0 n1

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    3 n

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    250

  • 0 n n

    n1

    K n1 0 n1

    1 0 n

    n

    0 n1

    n1 K n1 0 n1

    2 0 n

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    1 1 1

    0 n n

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    251

  • 59 3

    0 n

    n

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    1

    1 1

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    1 1

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    2

    2

    2

    2

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    22

    2

    3

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    33

    3

    3

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    0 252

  • 0 n

    1

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    0 x1 y

    2 z 3

    1Brouwer f

    m (x0, x1, , xn)

    xi 0, i0, 1, , n x0 x1 xn 1 (x0, x1, , xn)

    f (x0, x1, , x n) x0x1xn1

    1x0 x0 (x0, x1, , xn) 0

    2x0 x0 x1 x1 (x0, x1, , xn) 1

    3x0 x0x1 x1 x2 x2 (x0, x1, , xn) 2

    4 x i xi i (i0, 1, , n)

    i (i0, 1, , n)

    x i xi x0 x1 xn 1 x0x1 x n 1

    i (i0, 1, , n) x i xi

    1 (1, 0, 0, , 0) (x0, x1, , x n) x0 1

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    253

  • 59 3

    0

    2 (0, 1, 0, , 0) (x0, x1, , x n) x1 1

    x0 x0 x11 (0, 1, 0, , 0)

    1

    3 (0, 0, 1, , 0) (x0, x1, , x n) x2 1

    x0 x0x1 x1 x2 1 (0, 0, 1, , 0)

    2

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    n1 n3 (x0, x1, , 0)

    (x0, x1, , x n) xn 0 xn xn

    n (x0, x1, , 0) 0 n1

    (x0, x1, , 0, xn) n1 (0, x1, x2, , xn)

    0 xn1 xn0

    n2 n3

    (x0, x1, , 0, 0) (x0, x1, , xn1, xn)

    xn1 xn0 x n xn x n1 xn1 n

    n1 0 n2 1

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    (x 0m, 0 , x 1

    m, 0 , , x nm, 0), (x 0

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    m 0, 1, , n 1

    m n 0 n

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    1 x0x2x50 025

    254

  • m 1

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    n1 (x0, x1, , xn)

    f i0, 1, , n (x 0m, i, x 1

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    xnm, i) (x 0

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    m, i) (x0, x1, , xn) (x0, x1, , xn)

    (x 0m, 0, x 1

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    m, 0 x 0m, 0 f

    m (x 0m, i, x 1

    m, i, , xnm, i) (x0, x1, , xn)

    (x 0m, i, x 1

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    x0 x0

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    m, 0 x0m, 0

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    x1 x1, , xn xn x0x1xn x0x1xn 1

    (x0, x1, , xn)(x0, x1, , xn) (x0, x1, , xn)

    5

    1

    2n1 X0, X1, , Xn

    (p0, p1, , pn) fi (p0, p1, , pn), i0,

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    2 1

    255

  • 59 3

    p0 f0 p1 f1 pn fn 0

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    (i 0, 1, , n) fi (p0, p1, , pn)0

    (p0, p1, , p

    n )

    (p0, p1, , pn) n1 v(v0, v1, , vn)

    vi pi fifi 0

    vi pifi 0

    (v0, v1, , vn)

    ( 0, 1, , n)

    i (p0, p1, , pn)v0v1vn1

    v1

    i 0i 0, 1, , n

    0 1 n1

    ( 0, 1, , n) fi

    ( 0(p0, p

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    (p0, p1, , p

    n ), , n(p

    0, p

    1, , p

    n ))(p

    0, p

    1, , p

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    0, p

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    i vi pi v

    1 i vi (p0, p

    1, , p

    n )p

    i

    1 1 pi 0 vi (p0,

    p1, , pn )pi fi (p0, p1, , pn )0

    i pi 0 1

    p0 f0p1 f1p

    n fn 0

    1 v0 p0, v1 p

    1, ,vn p

    n fi (p

    0, p

    1, ,

    256

  • pn ) 0

    i fi (p0, p

    1, , p

    n ) 0 p

    0 f0p

    1 f1p

    n fn

    0 p1 fi (p0, p

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    pi 0 fi (p0, p1, , pn )0

    v

    2

    3 X

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    A B B A

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    257

  • 59 3

    B A B A

    AB

    AB A

    1

    p ((px, py)) p

    pp p AA

    A A A

    B

    p p A B

    B p 4

    A p B

    p

    p B 5 A

    A p

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    A B B A p p

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    258

  • A

    A C C p p

    A p

    A

    X Y (x, y) A (xA, yA)B (xB,

    yB) xA xB Y A B xA

    xB B A xA xB Y

    Y

    (1, 1) (1, 0)

    (1, 1) (1, 0)

    (1, 0) (1, 1) X 1

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    (1 x, 2) (1, 2) (1, 1)

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    259

  • 59 3

    3

    (0,1, ,n)

    p (p0, p1, , pn)

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    (p)

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    (2) pi 0 n

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    i0n p i

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    7 p (p0, p1, , p

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    i (p) (p) pi (zi(p

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    pi 0 i (p)(p) pi i (p

    )

    pi 0 i (p) 0

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    7 1

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    260

  • i(p)

    i1

    n

    (p)i0

    n

    pi

    i (p) i1

    n i1n pi 1 (p)1

    i (p) pi

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    pi i 1 n1

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    pi n(p)1i0

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    i(p) (p) 1i0

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    (2) pi 0 n1

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    261

  • 59 3

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  • 59 3

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  • 59 3

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  • 59 3

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    269

  • 59 3

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    270

  • F1, F2, F3,

    Vn X \ Fn Fn Vn X

    V1, V2, V3,

    V1 V2 V1V2 F1 F2

    X \ (F1F2) Vn F1, F2, F3,

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    x1, x2, 1 d (xn1, p)1 xn1 1

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    271

  • 59 3

    9 2

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    f(x)BY( f(x), ) x BX(x, )

    x f(x)V x f 1(V)

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    273

  • 59 3

    x X BY( f(x), )

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    x BX(x, ) f1(BY ( f(x), ))

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    f 1(G) X f X

    Y G X \ f 1(G) f 1(Y \G) f 1(G)

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    Y \G f 1(Y \G)

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  • 10 3

    9(1)X, Y n m

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    U (v, w) v V, w W VW U

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    x(x1, x2, , xn) v(v1, v2, , vn) y(y1, y2, , ym) w(w1, w2, , wm)

    d(x, v) (x1v1)2+(x2v2)2(xnvn)2

    d(y, w) (y1w1)2+(y2w2)2(ymwm)2

    (x, y)(x1, x2, , xn, y1, y2, , ym), (v, w)(v1, v2, , vn, w1, w2, , wm)d((x, y)(v, w))

    (x1v1)2+(x2v2)2(xnvn)2(y1w1)2+(y2w2)2(ymwm)2

    U (v, w)(8)

    1 2 11

    2222 d(x, v) 1, d(y, w)2

    d((x, y) (v, w)) (x, y) U (7)

    1, 2

    275

  • 59 3

    (x, y) XYd(x, v) 1, d(y, w)2U

    1, 2 d((x, y) (v, w)) d(x, v) 1

    d(y, w)2 (x, y) U (8)

    (2)U XY (1)

    1 0, 2 0

    (x, y) XYd(x, v) 1, d(y, w)2U

    V x Xd(x, v) 1, W y Yd(y, w)2

    V X W Y vV, wW, VW U

    U XY U (v, w) X, Y V,

    W vV, wW VW U (v, w)

    xd(x, v)1V

    yd(y, w)2W

    1 0, 2 0

    (x, y) XYd(x, v) 1, d(y, w)2VW U

    (1) U XY

    11

    11.1

    0 1 1

    1 1

    276

  • 2

    1 2

    2 3

    3

    2

    3

    4 5 , 4

    5 n

    n 1

    2 2 2 x (x1, x2)y (y1, y2)

    2

    xy (x1y1)2+(x2y2)

    2 (xiyi)2

    i1

    2

    23

    2 x(x1, x2, x3)y(y1, y2, y3) 2

    xy (x1y1)2+(x2y2)

    2+(x3y3)2 (xiyi)

    2i1

    3

    2

    n 2 x (x1, x2, , xn) y (y1, y2, , yn)

    xy (xiyi)2

    i1

    n

    n

    (1) x, y n xy 0

    277

  • 59 3

    (2) x, y n xyyx

    (3) x, y, z n xy yz xz

    (4)xy 0 xyx y

    (1), (2), (4) (3) 2

    1 3

    2

    (aibi)2

    i1

    n

    i1

    n

    ai22

    i1

    n

    ai bii1

    n

    bi22

    ai bii1

    n

    ai2

    i1

    n

    bi2

    i1

    n

    (aibi)2

    i1

    n

    i1

    n

    ai22

    i1

    n

    ai bii1

    n

    bi2

    ai22

    i1

    n

    ai2

    i1

    n

    bi2

    i1

    n

    bi2

    i1

    n

    ai2

    i1

    n

    bi2

    i1

    n2

    ai xiyi, bi yizi

    (xizi)2

    i1

    n

    (xiyi)2

    i1

    n

    (yizi)2

    i1

    n

    n 3 x x1, x2, , xn, y y1,

    y2, , yn, z z1, z2, , zn

    xz xy + yz

    4 X V

    V v V x Xxv V

    278

  • 0

    X

    1 (0, 1)

    1

    0 v 0

    212

    10 x xv 2

    1 (0, 1)

    [0, 1]

    1

    0 1

    11.2

    5 X

    x, y

    d(x, y) d

    (X, d)

    (1) x, y X d(x, y) 02

    (2) x, y X d(x, y) d(y, x)

    (3) x, y, z X d(x, z) d(x, y)d(y, z)

    (4) x y d(x, y) 0 2

    2

    279

  • 59 3

    n

    1 x

    1 x 1 x 0

    6(X, d) X x r 0

    BX (x, r) X x r

    BX (x, r) xXd(x , x) r

    x r X

    3

    7(X, d) X V

    V v V BX (v, ), V 0

    4

    10X d x0 X

    r 0 r BX (x0, r) X

    x BX (x0, r) 0 BX (x, ) BX (x0, r)

    r d(x, x0) d(x, x0) rx BX (x0, r)

    0 xBX (x, )

    d(x , x0) d(x , x)d(x, x0)d(x, x0)r

    xBX(x0, r) BX(x, ) BX(x0, r) BX(x, )

    BX(x0, r) BX(x0, r)

    1

    280

  • [0, 1]

    y f(x), yg(x)(y , x [0, 1]) 2

    d(f, g)

    [0, 1]max f(x)g(x)

    [0, 1] f(x) g(x)

    [0, 1]

    f(x)g(x) f(x) g(x) f(x) g(x)

    d(f, g) 0

    [0, 1] f(x)g(x) d(f, g)0

    f(x) g(x) d(f, g)0 3 y f(x), yg(x), yh(x)

    d(f, h)[0, 1]

    max f(x)h(x) [0, 1]

    max f(x)g(x)g(x) h(x)

    [0, 1]

    max f(x)g(x) [0, 1]

    max g(x)h(x) d(f, g)d(g, h)

    [0, 1]

    11.3

    8 X

    X

    (1) X

    (2)

    (3)

    X X (X,

    ) X

    281

  • 59 3

    11X X

    (1) X

    X X x

    X

    (2) X A U A

    U x U x

    A V BX (x, ) V

    V U BX (x, ) U U

    (3) V1, V2, , Vk X

    V V1V2 Vk x j x Vj

    V1, V2, , Vk j

    BX (x, j) Vj 1, 2, , k 1, 2, , k

    k j 0

    x Vj j

    BX (x, ) BX (x, j) Vj BX (x, ) V V

    (3)

    1n (n1

    , 1n1

    )

    n 1, 2, , n ( n1

    , 1n1

    )

    [0, 1]

    0 282

  • 11.4

    9X X

    F X \ FF X

    X X X

    X X

    1 F[0, 1]

    \ F( , 0)(1, ) ,

    v x

    xv \ F 0

    F

    1 [1, 1]1 1

    (1, 1)1 1 (1, 1]1 1

    X [2, 1] (1, 1]

    1 (3) 1

    [2, 1] [2, 1]

    X

    X

    12

    (1) X

    (2)

    283

  • 59 3

    (3)

    (2)

    (3)

    (2) 1

    n [ n1

    , 1n1

    ] n3, 4, ,

    0 1 n [ n1

    , 1n1

    ]

    n

    (0, 1)

    11.5

    10 X

    x y X x Uy V UVU

    V U V

    13

    XdxyX

    21

    d(x, y) x, y BX (x, ) BX (y, )

    x, y

    BX (x, )BX (y, )

    d(x, z), d(y, z) zX z BX (x, ) BX (y, )

    d(x, y) d(x, z) + d(y, z)

    221

    d(x, y) BX (x, )BX (y, )

    X

    284

  • 11.6

    X A X A V

    VA A A A

    VA

    V

    A A

    2 V1, V2 V1A, V2A V1 A

    V2 A

    2 (V1 A)(V2 A) A V1

    V2 (V1V2)A

    VA V

    A

    A

    2 V1, V2 V1A, V2A (V1A) (V2A)

    A V1 V2 (V1V2)A

    14X X A

    A

    A X A V1V2

    Vr V1,V2, ,Vr

    A B X V VA

    A A V1V2 Vr

    A V1A, V2A, , VrA

    15A X A

    285

  • 59 3

    A X X \ A

    X A

    X \ A X X

    A

    14

    A

    16X K X

    x X \ K x V, KW, VW X

    V, W

    X y K x Vx, y, y Wx, y,

    Vx, y Wx, y Vx, y, Wx, y K

    K Wx, y1 Wx, y2 Wx, yr y1,y2,

    , yrK y K Wx, y K

    K K

    VVx, y1 Vx, y2 Vx, yr, WWx, y1 Wx, y2 Wx, yr

    V, W x V, KW VW Vx, y1

    Vx, y2 Vx, yr Vx, yi(i1, 2, , r) Wx, y1 , Wx, y2, ,

    Wx, yr WWx, y1 Wx, y2 Wx, yr

    17

    K X

    16xX \ KxVx, VxKVx

    X \ K x Vx

    Vx K K Vx

    X \ K X \ K K

    286

  • 11X d X A

    x, y A d(x, y) K K

    A diamA

    diamA A x, y d(x, y)

    7K n K

    K n

    17

    K m Bm n

    m Bm xn x m x x

    x

    Bmm n K K

    Bm1 Bm1 Bmk m1, m2, , mk Bm

    M m1, m2, , mk K BM K

    K K

    C L

    C (x1, x2, , xn)nL xj L.j1, 2, , n

    4 [L, L]

    C [L, L] n 5 C

    K C

    15K

    287

  • 59 3

    11.7

    12 X x1, x2, X p

    p U N

    j NN xj U

    p p U

    p

    1

    18 X 1

    (xjj ) 1, 2, 3,

    (xj) (xj) p q 2 X

    p U, q V , UV U, V p, q

    j N1 j N2 xj U, xj V

    N1, N2 xj UVUV

    1

    1 1, 2, 1, 2,

    1, 2, 1 2 1, 2, 3, 4, 5,

    19X F X (xjj ) F (xj

    j ) X p p F

    p F F X \ F

    F X \ F (xjj ) p

    j N xj X \ F N

    xj F p F

    288

  • 20f X 1

    f

    X

    3 f(X) m

    (m, m) m 1

    f(X)

    I1, I2, , IkM (M,

    M) I1, I2, , Ik f(X)(M, M)

    f

    21f X

    xX f(u) f(x) f(v)Xu, v

    minf f(x)xX , Msup f(x)xX minf f(x)xX

    xX m f(x) Msup f(x)xX

    xX M f(x) mM

    f(x)

    X x f(x) xX

    f(x) M xX g(x)Mf(x)1

    g(x)Mf(x)1

    y f(x) zMy1

    M f(x)

    M f(x) M M f(x) M M

    20 f(v)M v

    X x X f(x) m x X

    h(x) f(x)m1

    289

  • 59 3

    m f(x) m f(x) m

    m f(x) m m f(u)m u

    X m M f(u) f(x) f(v)

    11.8

    13X x X N x X

    x U U N U N x

    22X X V V

    X

    V V

    V

    V v Uv, Uv V Uv

    V Uv V v

    v Uv Uv Uv V Uv

    V

    14

    (1) X A A

    XXA

    (2) X A A X

    X A A0

    A

    (1)A A

    (2) F A F F

    290

  • A

    (1) A A0 A

    (2) U A U A0 A0 U

    23X A A x1, x2, x3, X

    p p A

    F A j xj F

    p F 19

    p

    p A

    1 (0, 1)1, 21

    , 31

    , 0

    0 (0, 1) [0, 1]

    11.9

    15X d

    X x1, x2, x3,

    j N, k N j, k d(xj, xk)

    N

    X X

    X

    (0, 1) 21

    , 31

    ,

    n(n1) 1 n

    n1

    n11

  • 59 3

    24X X

    X

    x1, x2, x3, X X p

    xn1, xn2, xn3 p

    x1, x2, x3, 0 m Nn N

    m, n d(xm, xn) 21N2

    1

    p N

    nj N nj d(xnj, p) 21

    n N

    d(xn, p) d(xn, xnj)d(xnj, p)212

    1

    x1, x2, x3, p

    X

    6

    160 X

    X X

    X X Bi (i1, 2, , k)

    X XB1B2 Bk

    X A A(B1 A) (B2 A) (Bk

    A) Bi A A

    25X X

    0 292

  • X

    X 3 X

    X 3

    X m k, n k, mn d(xm, xn)

    k1 x1, x2, , xk1 xm

    BX (xm, ) 23X

    mk BX (xm, ) X

    BX (xm, ) xk m k

    d(xm, xk) k

    x1, x2,

    X X

    26X A A

    diamAdiam

    A diam A diam x, y

    d(x, x), d(y, y) A x, y

    x d(x, x)

    A x BX (x, ) A

    x

    d(x, y) d(x, x)d(x, y)d(y, y)diam A2

    0 d(x, y) diamA2

    d(x, y) diam A d(x, y)diam A0

    21d(x, y)diam A d(x, y) diam A2

    diam diam A diam A diam diam A diam

    293

  • 59 3

    27

    X X

    X

    X x1, x2, x3, X

    X

    0 X 26 X

    X

    X X

    0

    X

    F1 F2 F3 Fn 2n

    1

    X F1 ,

    F2 , F3,

    X 21 F1 X

    F1 0

    F1

    2214

    1 F2 n

    n xn Fn mn xm, xn

    xm, xn Fn diamFn2n1 d(xm, xn)2n

    1

    x1, x2, x3, X p

    294

  • Fn m n xm Fn n

    pFn

    X

    V pV BX (p, ) X p

    BX (p, )V V

    n 2n1

    p Fn

    diamFn FnBX (p, ) V

    Fn x1, x2, x3,

    X

    8X d 3

    (1)X

    (2)X

    (3)X

    6 242527 (1) (2) (2) (3) (3) (1)

    (1), (2), (3)

    11.10

    28(X, d) d

    X X

    1

    X 1 X

    x x 2x B(x, 2x) 1

    295

  • 59 3

    x x x

    B(x, x) X x B(x, x) X

    X

    B(x1, 1)B(x2, 2) B(xr, r)X, i xii1, 2, , r

    x1, x2, , xr 1, 2, , r

    A X u

    u 1 r i B(xi, i) A

    v

    d(v, xi) d(v, u)d(u, xi)i 2i

    AB(xi, 2i) B(xi, 2i) 1

    A

    X X

    1

    X, Y dX, dY fX Y X

    Y f

    0 0 dX (x, x) X x, x

    dY (f(x), f(x)) x, x

    9X, Y X X

    Y

    dX, dY X, Y fX Y X

    Y yY

    VyxXdY (f(x), y) 21

    f(x) y 21 x y 2

    1

    296

  • Y BY (y, 21) Vyf

    1(BY (y, 21)) BY (y, 2

    1)

    f y Vy X

    xX xVf (x)

    Vy VyyY X

    28 X

    Vy 0 x, x dX (x, x)

    x, xx x 2 dX (x, x)

    xVy xVy y Y

    dY (f(x), y) 21, dY (f(x), y) 2

    1

    dY ( f(x), f(x)) dY(f(x), y)dY(f(x), y)

    fX Y

    11.11

    17 X X f(x) X

    x x idX A

    X A A X

    iA X 1 Y

    X Y

    18XY X

    Y h

    (1) h Y X h1

    (2)h h1

    f(x) x 1

    297

  • 59 3

    Y y Y x

    y Y x 1

    f(x) x 1 X Y 1 1

    h Y

    h f(x) x

    h

    Y 1 x

    X Y X Y

    X Y h h1

    X h X, Y h1

    X h1hidX

    h1 h Y hh1idY

    19xyz

    R

    (1)xRx

    (2)xRy yRx

    (3)xRy yRz xRz

    29

    X X X

    X X f X Y

    f 1 Y X X Y

    Y X

    X Y Y Z fX Y gY

    Z f, g f 1, g1

    298

  • gf (gf)1f1g1

    gf X Z X Z

    2

    2 2

    1t (t1) 2

    t

    r(0)

    ( r)

    r

    r

    31 X Y(1, 1) X

    Y

    f(x)1 xx

    , xX

    X Y f(0)0, x

    f(x) 1, x f(x) 1

    y1 xx

    x x 0 y 0 x1yy

    x 0 y 0

    299

  • 59 3

    x1yy

    x1 y

    y

    f

    f 1(y)1 y y

    f1(0)0, y 1 f1(y) , y 1

    f1(y)

    300

  • The Doshisha University Economic Review Vol.59 No.3

    Abstract

    Yasuhito TANAKA, Introduction to General Equilibrium Theory with a Proof of

    Brouwer's Fixed Point Theorem

    I present an introductory explanation of the proof of the existence of

    general equilibrum mainly in an exchange economy. Present elementary proofs

    of Sperner's lemma and Brouwer's fixed point theorem are also indicated. The

    appendices provide expositions of related mathematical concepts.

    301

    1223456781921031111.111.211.311.411.511.611.711.811.911.1011.11

    Abstract