ήʔϜཧ࿦ /&95
ઓུ‫ྗڠܗ‬ήʔϜ ୈ7ճ
1. ֬ఆత཭൓ઓུΛཧղ
2. ݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུͷؔ܎Λཧղ
ຊಈըͷ໨త
1.֬ఆత཭൓ઓུ
(a)֬ఆత཭൓ઓུͷఆٛ
(b)݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
໨࣍
֬ఆత཭൓ઓུ
ʢ෮शʣ෦෼ήʔϜ
෦෼ήʔϜ

ઓུͷ૊ ͱ
ఏ‫ܞ‬ ʹରͯ͠
 ʹΑͬͯ

 Λ‫ݻ‬ఆͯ͠ಘΒΕΔ෦෼ήʔϜ Λද͢



ͨͩ͠ ͷ৔߹͸‫ݩ‬ͷήʔϜΛද͢ͱ͢Δ



	ྫ
 
 
 

 Λ‫ݻ‬ఆ













x ∈ X S ⊆ N G|xNS
xNS G′ = (S, {Xi}i∈S, {ui}i∈S)
S = N
N = {A, B, C} {a2, b2, c1} ∈ X S = {A, C}
xN{A,C} = xB = b2
AʘB


 




 


AʘB


 




 


$͕
c1
a1
a2 a2
b1 b2 b1 b2
$͕
c2
a1
ʢ෮शʣ݁ୗ଱ੑͷఆٛ
݁ୗ଱ੑͱࣗ‫੍ڧݾ‬త

 Λ೚ҙʹ༩͑ΒΕͨઓུͷ૊ͱ͢Δ

	
֤ ʹ͍ͭͯ ͕෦෼ήʔϜ ʹ͓͍ͯ݁ୗ଱ੑΛ΋ͭͱ͸


 

Ͱ͋Δ͜ͱΛ͍͏



	
ʮ֤ఏ‫ܞ‬ 	ͨͩ͠ 
ʹର͠
 ͕෦෼ήʔϜ ʹ͓͍ͯ݁ୗ଱ੑΛ΋ͭʯ

ɹɹͱ͍͏͜ͱ͕ఆٛ͞Εͨͱ͢Δ͜ͷͱ͖֤ఏ‫ܞ‬ 	ͨͩ͠ 
ʹ͍ͭͯ

	B
 ͕෦෼ήʔϜ ʹ͓͍ͯࣗ‫੍ڧݾ‬తͰ͋Δͱ͸
 ͷ͢΂ͯͷਅ෦෼ू߹ ʹର͠

 ͸ ʹ͓͍ͯ݁ୗ଱ੑΛ΋ͭ͜ͱΛ͍͏

	C
 ͕෦෼ήʔϜ ʹ͓͍ͯ݁ୗ଱ੑͰ͋Δͱ͸
 ͸ ʹ͓͍ͯࣗ‫੍ڧݾ‬తͰ͋ͬͯ

͔͠΋ Λຬͨ͢Α͏ͳ


 ʹ͓͚Δࣗ‫੍ڧݾ‬తͳ ͕ଘࡏ͠ͳ͍͜ͱΛ͍͏
x ∈ X
i ∈ N xi G|xN{i}
∀yi ∈ Xi, ui(x) ≥ ui(yi, xN{i})
S ⊆ N 1 ≤ |S|  m xS G|xNS
S ⊆ N |S| = m
xS G|xNS S T ⊊ S
xT G|xNT
xS G|xNS xS G|xNS
∀i ∈ S, ui(yS, xNS)  ui(x)
G|xNS yS ∈ XS
 ͕݁ୗ଱ੑΛ΋ͭͱ͸
͕ ʹ͓͍ͯ
݁ୗ଱ੑΛ΋ͭ͜ͱΛ͍͏
x ∈ X x G
֬ఆత཭൓ઓུͷఆٛ
֬ఆత཭൓ઓུ

 ΛۭͰͳ͍೚ҙͷఏ‫
ܞ‬ Λ೚ҙʹ༩͑ΒΕͨઓུͷ૊ͱ͢Δ

͜ͷͱ͖
 ͕ʹ͓͍ͯ֬ఆత཭൓ઓུ Λ΋ͭͱ͸


	
 ͕཭൓ઓུ

	
 ͷͲͷਅ෦෼ू߹ ΋ ʹ͓͍ͯ֬ఆత཭൓ઓུΛ΋ͨͳ͍

ͱ͖Λ͍͏

















S ⊆ N x ∈ X
S x yS ∈ XS
yS
S T ⊊ S (yS, xNS)
N
S
T
S
T
yS yT
º
֬ఆత཭൓ઓུͷఆٛ
֬ఆత཭൓ઓུ

 ΛۭͰͳ͍೚ҙͷఏ‫
ܞ‬ Λ೚ҙʹ༩͑ΒΕͨઓུͷ૊ͱ͢Δ

͜ͷͱ͖
 ͕ʹ͓͍ͯ֬ఆత཭൓ઓུ Λ΋ͭͱ͸


	
 ͕཭൓ઓུ

	
 ͷͲͷਅ෦෼ू߹ ΋ ʹ͓͍ͯ֬ఆత཭൓ઓུΛ΋ͨͳ͍

ͱ͖Λ͍͏



 ͷͱ͖͜ͷਅ෦෼ू߹͸ۭू߹Ͱ͋Γɺ֬ఆత཭൓ઓུΛ΋ͨͳ͍

Ώ͑ʹʹ͓͚Δ཭൓ઓུ Λ΋ͭͱ͢Ε͹֬ఆతͰ͋Δ



 ͷͱ͖͜ͷਅ෦෼ू߹͸ 
 Ͱ͋Δ

Ώ͑ʹʹ͓͚Δ཭൓ઓུ Λ΋ͪ
 ΍ ͕֬ఆత཭൓ઓུΛ΋ͨͳ͍ͷͰ͋Ε͹
֬ఆతͰ͋Δ

 ͸͜ͷΑ͏ʹ࠶‫ؼ‬తʹܾ·Δ

S ⊆ N x ∈ X
S x yS ∈ XS
yS
S T ⊊ S (yS, xNS)
S = {i}
x y{i}
S = {i, j} {i} {j}
x y{i,j} {i} {j}
|S|  1
ਓͰͷ཭൓ઓུ͸֬ఆత཭൓ઓུ
 Ͱఆٛ͞Ε͍ͯΔ
S = {i}
݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུΛ΋ͨͳ͍‫
ߧۉ‬
ઓུͷ૊ ͕༩͑ΒΕ͍ͯΔ͜ͷͱ͖೚ҙͷ ʹ͍ͭͯ
 ͕෦෼ήʔϜ ʹ͓͍ͯ

݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


 ʹ͓͍ͯͰ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ



ͱ͘ʹ
͕ ʹ͓͍ͯ݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


Ͱ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ















x ∈ X S ⊆ N xS ∈ XS G|xNS
T ⊆ S
G|xNS x
x G T ⊆ N
x
݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུΛ΋ͨͳ͍‫
ߧۉ‬
ઓུͷ૊ ͕༩͑ΒΕ͍ͯΔ͜ͷͱ͖೚ҙͷ ʹ͍ͭͯ
 ͕෦෼ήʔϜ ʹ͓͍ͯ

݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕
 ʹ͓͍ͯͰ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

ͱ͘ʹ
͕ ʹ͓͍ͯ݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


Ͱ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

݁ୗ଱ੑφογϡ‫ߧۉ‬ ʹ͍ͭͯߟ͑Δ

෦෼ఏ‫ܞ‬ ʹ͍ͭͯߟ͑Δ

 ʹ͍ͭͯ཭൓ઓུΛ΋ͨͳ͍͔Β
֬ఆత཭൓ઓུΛ΋ͨͳ͍

  ΋֬ఆత཭൓ઓུΛ΋ͨͳ͍













x ∈ X S ⊆ N xS ∈ XS G|xNS
T ⊆ S G|xNS x
x G T ⊆ N
x
x = (a2, b2, c1)
{A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}
{A}
{B}{C}
AʘB


 




 


AʘB


 




 


$͕
c1
a1
a2 a2
b1 b2 b1 b2
a1
$͕
c2
݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུΛ΋ͨͳ͍‫
ߧۉ‬
ઓུͷ૊ ͕༩͑ΒΕ͍ͯΔ͜ͷͱ͖೚ҙͷ ʹ͍ͭͯ
 ͕෦෼ήʔϜ ʹ͓͍ͯ

݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕
 ʹ͓͍ͯͰ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

ͱ͘ʹ
͕ ʹ͓͍ͯ݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


Ͱ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

݁ୗ଱ੑφογϡ‫ߧۉ‬ ʹ͍ͭͯߟ͑Δ

 ʹ͍ͭͯ཭൓ઓུΛ΋ͨͳ͍͔Β
֬ఆత཭൓ઓུΛ΋ͨͳ͍

  ΋֬ఆత཭൓ઓུΛ΋ͨͳ͍

 ʹ͍ͭͯ཭൓ઓུΛ΋ͨͳ͍͔Β
֬ఆత཭൓ઓུΛ΋ͨͳ͍













x ∈ X S ⊆ N xS ∈ XS G|xNS
T ⊆ S G|xNS x
x G T ⊆ N
x
x = (a2, b2, c1)
{A, B}
{A, C}{B, C}
{A, B, C}
AʘB


 




 


AʘB


 




 


$͕
c1
a1
a2 a2
b1 b2 b1 b2
a1
$͕
c2
݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུΛ΋ͨͳ͍‫
ߧۉ‬
ઓུͷ૊ ͕༩͑ΒΕ͍ͯΔ͜ͷͱ͖೚ҙͷ ʹ͍ͭͯ
 ͕෦෼ήʔϜ ʹ͓͍ͯ

݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕
 ʹ͓͍ͯͰ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

ͱ͘ʹ
͕ ʹ͓͍ͯ݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


Ͱ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

݁ୗ଱ੑφογϡ‫Ͱߧۉ‬͸ͳ͍ ʹ͍ͭͯߟ͑Δ

෦෼ఏ‫ܞ‬ ʹ͍ͭͯߟ͑Δ

 ʹ͍ͭͯ཭൓ઓུΛ΋ͨͳ͍͔Β
֬ఆత཭൓ઓུΛ΋ͨͳ͍

  ΋֬ఆత཭൓ઓུΛ΋ͨͳ͍













x ∈ X S ⊆ N xS ∈ XS G|xNS
T ⊆ S G|xNS x
x G T ⊆ N
x
x = (a1, b1, c1)
{A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}
{A}
{B}{C}
AʘB


 




 


AʘB


 




 


$͕
c1
a1
a2 a2
b1 b2 b1 b2
a1
$͕
c2
݁ୗ଱ੑφογϡ‫ͱߧۉ‬ͷؔ܎
݁ୗ଱ੑφογϡ‫֬ͱߧۉ‬ఆత཭൓ઓུΛ΋ͨͳ͍‫
ߧۉ‬
ઓུͷ૊ ͕༩͑ΒΕ͍ͯΔ͜ͷͱ͖೚ҙͷ ʹ͍ͭͯ
 ͕෦෼ήʔϜ ʹ͓͍ͯ

݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕
 ʹ͓͍ͯͰ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

ͱ͘ʹ
͕ ʹ͓͍ͯ݁ୗ଱ੑφογϡ‫͋Ͱߧۉ‬Δͱ͸
೚ҙͷ෦෼ఏ‫ܞ‬ ͕


Ͱ֬ఆత཭൓ઓུΛ΋ͨͳ͍͜ͱͰ͋Δ

݁ୗ଱ੑφογϡ‫Ͱߧۉ‬͸ͳ͍ ʹ͍ͭͯߟ͑Δ

 ʹ͍ͭͯ཭൓ઓུ Λ΋ͭ͞Βʹ ʹର͠

 
 ͱ΋ʹ཭൓ઓུΛ΋ͨͳ͍
ͭ·Γ֬ఆత཭൓ઓུΛ΋ͨͳ͍

Ώ͑ʹ཭൓ઓུ ͸֬ఆతͰ͋Δ













x ∈ X S ⊆ N xS ∈ XS G|xNS
T ⊆ S G|xNS x
x G T ⊆ N
x
x = (a1, b1, c1)
{A, B} y{A,B} = (a2, b2) x′ = (a2, b2, c1)
{A} {B}
y{A,B} = (a2, b2)
AʘB


 




 


AʘB


 




 


$͕
c1
a1
a2 a2
b1 b2 b1 b2
a1
$͕
c2
֬ఆత཭൓ઓུ

 ΛۭͰͳ͍೚ҙͷఏ‫
ܞ‬ Λ೚ҙʹ༩͑ΒΕͨઓུͷ૊ͱ͢Δ

͜ͷͱ͖
 ͕ʹ͓͍ͯ֬ఆత཭൓ઓུ Λ΋ͭͱ͸


	
 ͕཭൓ઓུ

	
 ͷͲͷਅ෦෼ू߹ ΋ ʹ͓͍ͯ֬ఆత཭൓ઓུΛ΋ͨͳ͍

ͱ͖Λ͍͏
S ⊆ N x ∈ X
S x yS ∈ XS
yS
S T ⊊ S (yS, xNS)
y{A,B} = (a2, b2)
º
º
ࢀߟจ‫ݙ‬ɿ‫ྗڠ‬ήʔϜཧ࿦

தࢁɾધ໦ɾ෢౻ɹႻ૲ॻ๪
See you next timeʂ
ήʔϜཧ࿦ /95

࣍ճɿ֬ఆత཭൓ઓུͱ݁ୗ଱ੑφογϡ‫ߧۉ‬ͷؔ܎ূ໌

ゲーム理論NEXT 戦略形協力ゲーム第7回 -確定的離反戦略-