❈♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣s ❛♥❞ ❝♦♥❥✉❣❛t✐♦♥ ♠♦♥♦✐❞s ✇✐t❤ ❝❛♥❝❡❧❧❛t✐♦♥ ▼❛r❣❛r✐❞❛ ❘❛♣♦s♦ ❯♥✐✈❡rs✐t② ♦❢ t❤❡ ❆③♦r❡s ❋❛❝✉❧t② ♦❢ ❙❝✐❡♥❝❡ ❛♥❞ ❚❡❝❤♥♦❧♦❣② ❉❡♣❛rt♠❡♥t ♦❢ ▼❛t❤❡♠❛t✐❝s ❛♥❞ ❙t❛t✐st✐❝s ✭❥♦✐♥t ✇♦r❦ ✇✐t❤ ❆✳ P❛✉❧❛ ●❛rrã♦✱ ◆✳ ▼❛rt✐♥s✲❋❡rr❡✐r❛ ❛♥❞ ▼✳ ❙♦❜r❛❧✮ ❈❚ ✷✵✶✽ ❈❛t❡❣♦r② ❚❤❡♦r② ✷✵✶✽ ❏✉❧② ✵✽✲✶✹✱ P♦♥t❛ ❉❡❧❣❛❞❛✱ ❆③♦r❡s ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✶ ✴ ✷✹
❆ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣ ✐s ❛ s❡♠✐❣r♦✉♣ ❡q✉✐♣♣❡❞ ✇✐t❤ ❛ ✉♥❛r② ♦♣❡r❛t✐♦♥ s❛t✐s❢②✐♥❣ t❤❡ ❢♦❧❧♦✇✐♥❣ ✐❞❡♥t✐t✐❡s✿ ✭✶✮ ✭✷✮ ✭✸✮ ❊①❛♠♣❧❡s ✶ ✳ ❆♥② ❣r♦✉♣ ✇✐t❤ ❆♥② ❝♦♠♠✉t❛t✐✈❡ ♠♦♥♦✐❞ ✇✐t❤ ✳ ✵ ✶ ✇✐t❤ q✉❛t❡r♥✐♦♥ ♣r♦❞✉❝t ❛♥❞ ❝♦♥❥✉❣❛t✐♦♥✳ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✷ ✴ ✷✹
❊①❛♠♣❧❡s ✶ ✳ ❆♥② ❣r♦✉♣ ✇✐t❤ ❆♥② ❝♦♠♠✉t❛t✐✈❡ ♠♦♥♦✐❞ ✇✐t❤ ✳ ✵ ✶ ✇✐t❤ q✉❛t❡r♥✐♦♥ ♣r♦❞✉❝t ❛♥❞ ❝♦♥❥✉❣❛t✐♦♥✳ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❆ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣ ( S , + , ()) ✐s ❛ s❡♠✐❣r♦✉♣ ( S , +) ❡q✉✐♣♣❡❞ ✇✐t❤ ❛ ✉♥❛r② ♦♣❡r❛t✐♦♥ () : S → S s❛t✐s❢②✐♥❣ t❤❡ ❢♦❧❧♦✇✐♥❣ ✐❞❡♥t✐t✐❡s✿ x + x = x + x ✭✶✮ x + y + y = y + y + x ✭✷✮ ( x + y ) = y + x ✭✸✮ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✷ ✴ ✷✹
✵ ✶ ✇✐t❤ q✉❛t❡r♥✐♦♥ ♣r♦❞✉❝t ❛♥❞ ❝♦♥❥✉❣❛t✐♦♥✳ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❆ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣ ( S , + , ()) ✐s ❛ s❡♠✐❣r♦✉♣ ( S , +) ❡q✉✐♣♣❡❞ ✇✐t❤ ❛ ✉♥❛r② ♦♣❡r❛t✐♦♥ () : S → S s❛t✐s❢②✐♥❣ t❤❡ ❢♦❧❧♦✇✐♥❣ ✐❞❡♥t✐t✐❡s✿ x + x = x + x ✭✶✮ x + y + y = y + y + x ✭✷✮ ( x + y ) = y + x ✭✸✮ ❊①❛♠♣❧❡s ❆♥② ❣r♦✉♣ ✇✐t❤ x = x − ✶ ✳ ❆♥② ❝♦♠♠✉t❛t✐✈❡ ♠♦♥♦✐❞ ✇✐t❤ x = e ✳ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✷ ✴ ✷✹
❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❆ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣ ( S , + , ()) ✐s ❛ s❡♠✐❣r♦✉♣ ( S , +) ❡q✉✐♣♣❡❞ ✇✐t❤ ❛ ✉♥❛r② ♦♣❡r❛t✐♦♥ () : S → S s❛t✐s❢②✐♥❣ t❤❡ ❢♦❧❧♦✇✐♥❣ ✐❞❡♥t✐t✐❡s✿ x + x = x + x ✭✶✮ x + y + y = y + y + x ✭✷✮ ( x + y ) = y + x ✭✸✮ ❊①❛♠♣❧❡s ❆♥② ❣r♦✉♣ ✇✐t❤ x = x − ✶ ✳ ❆♥② ❝♦♠♠✉t❛t✐✈❡ ♠♦♥♦✐❞ ✇✐t❤ x = e ✳ S = { q ∈ H | ✵ < � q � < ✶ } ✇✐t❤ q✉❛t❡r♥✐♦♥ ♣r♦❞✉❝t ❛♥❞ ❝♦♥❥✉❣❛t✐♦♥✳ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✷ ✴ ✷✹
❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❆ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣ ( S , + , ()) ✐s ❛ s❡♠✐❣r♦✉♣ ( S , +) ❡q✉✐♣♣❡❞ ✇✐t❤ ❛ ✉♥❛r② ♦♣❡r❛t✐♦♥ () : S → S s❛t✐s❢②✐♥❣ t❤❡ ❢♦❧❧♦✇✐♥❣ ✐❞❡♥t✐t✐❡s✿ x + x = x + x ✭✶✮ x + y + y = y + y + x ✭✷✮ ( x + y ) = y + x ✭✸✮ ❚❤❡ q✉❛s✐✈❛r✐❡t② S ♦❢ ❝♦♥❥✉❣❛t✐♦♥ s❡♠✐❣r♦✉♣s ✇✐t❤ ❝❛♥❝❡❧❧❛t✐♦♥ ✐s ❛ ✇❡❛❦❧② ▼❛❧✬ts❡✈ ❝❛t❡❣♦r②✳ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✸ ✴ ✷✹
❆ ✜♥✐t❡❧② ❝♦♠♣❧❡t❡ ❝❛t❡❣♦r② ✐s ✇❡❛❦❧② ▼❛❧✬ts❡✈ ✐❢ ❢♦r ❛❧❧ ♣✉❧❧❜❛❝❦s ♦❢ s♣❧✐t ❡♣✐♠♦r♣❤✐s♠s ❛❧♦♥❣ s♣❧✐t ❡♣✐♠♦r♣❤✐s♠s ✷ ✷ ✶ ✶ t❤❡ ♣❛✐r ✷ ✱ ✇✐t❤ ✶ ❛♥❞ ✶ ✱ ✐s ❥♦✐♥t❧② ✶ ✶ ✷ ❡♣✐♠♦r♣❤✐❝✳ ❲❡❛❦❧② ▼❛❧✬ts❡✈ ❈❛t❡❣♦r② ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✹ ✴ ✷✹
� � � � � � ❲❡❛❦❧② ▼❛❧✬ts❡✈ ❈❛t❡❣♦r② ❆ ✜♥✐t❡❧② ❝♦♠♣❧❡t❡ ❝❛t❡❣♦r② ✐s ✇❡❛❦❧② ▼❛❧✬ts❡✈ ✐❢ ❢♦r ❛❧❧ ♣✉❧❧❜❛❝❦s ♦❢ s♣❧✐t ❡♣✐♠♦r♣❤✐s♠s ❛❧♦♥❣ s♣❧✐t ❡♣✐♠♦r♣❤✐s♠s e ✷ A × B C � C π ✷ g π ✶ e ✶ s r A � B f t❤❡ ♣❛✐r ( e ✶ , e ✷ ) ✱ ✇✐t❤ e ✶ = < ✶ A , sf > ❛♥❞ e ✷ = < rg , ✶ C > ✱ ✐s ❥♦✐♥t❧② ❡♣✐♠♦r♣❤✐❝✳ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✹ ✴ ✷✹
■♥ ✇❡ ❤❛✈❡ ❲❡❛❦❧② ▼❛❧✬ts❡✈ ❈❛t❡❣♦r② ❊①❛♠♣❧❡s ♦❢ ✇❡❛❦❧② ▼❛❧✬ts❡✈ ❝❛t❡❣♦r✐❡s ❛r❡ ✲ ❉▲❛t✱ ♣r♦♣❡rt② ❝❤❛r❛❝t❡r✐③✐♥❣ ✐t ❛♠♦♥❣st t❤❡ ✈❛r✐❡t✐❡s ♦❢ ❧❛tt✐❝❡s ✲ q✉❛s✐✈❛r✐❡t✐❡s ♦❢ ❛❧❣❡❜r❛s ✇✐t❤ ❛ t❡r♥❛r② ♦♣❡r❛t✐♦♥ p ( x , y , z ) s❛t✐s❢②✐♥❣ p ( x , y , y ) = p ( x ′ , y , y ) ⇒ x = x ′ ✳ p ( x , y , y ) = p ( y , y , x ) ❛♥❞ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✺ ✴ ✷✹
❲❡❛❦❧② ▼❛❧✬ts❡✈ ❈❛t❡❣♦r② ❊①❛♠♣❧❡s ♦❢ ✇❡❛❦❧② ▼❛❧✬ts❡✈ ❝❛t❡❣♦r✐❡s ❛r❡ ✲ ❉▲❛t✱ ♣r♦♣❡rt② ❝❤❛r❛❝t❡r✐③✐♥❣ ✐t ❛♠♦♥❣st t❤❡ ✈❛r✐❡t✐❡s ♦❢ ❧❛tt✐❝❡s ✲ q✉❛s✐✈❛r✐❡t✐❡s ♦❢ ❛❧❣❡❜r❛s ✇✐t❤ ❛ t❡r♥❛r② ♦♣❡r❛t✐♦♥ p ( x , y , z ) s❛t✐s❢②✐♥❣ p ( x , y , y ) = p ( x ′ , y , y ) ⇒ x = x ′ ✳ p ( x , y , y ) = p ( y , y , x ) ❛♥❞ ■♥ S ✇❡ ❤❛✈❡ p ( x , y , z ) = x + y + z ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✺ ✴ ✷✹
� � � � � � � � � � � � � � � � � ❆❞♠✐ss✐❜✐❧✐t② ❞✐❛❣r❛♠s ❆♥ ❛❞♠✐ss✐❜✐❧✐t② ❞✐❛❣r❛♠ ❣✐✈❡s r✐s❡ t♦ C g f γ π ✷ s A B C r s e ✷ g ✭✶✮ � D A × B C B β β α γ e ✶ f D r π ✶ α A fr = ✶ B = gs ✱ α r = β = γ s ❚❤❡ tr✐♣❧❡ ( α, β, γ ) ✐s ❛❞♠✐ss✐❜❧❡ ✇✐t❤ r❡s♣❡❝t t♦ ( f , r , g , s ) ✐❢ t❤❡r❡ ❡①✐sts ❛ ✉♥✐q✉❡ ♠♦r♣❤✐s♠ ϕ : A × B C → D s✉❝❤ t❤❛t ϕ e ✶ = α ❛♥❞ ϕ e ✷ = γ ✳ ❚❤❡♥ ✇❡ s❛② t❤❛t t❤❡ ❞✐❛❣r❛♠ ( ✶ ) ✐s ❛❞♠✐ss✐❜❧❡✳ ▼✳❘❛♣♦s♦ ✭❋❈❚✲❯❆❝✮ ❈♦♥❥✉❣❛t✐♦♥ ❙❡♠✐❣r♦✉♣s ❏✉❧② ✵✽✲✶✹✱ ✷✵✶✽ ✻ ✴ ✷✹
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