Definition 3.3 .

An almost KΓ€hler manifold ( M , Ο‰ , J ) 𝑀 πœ” 𝐽 (M,\omega,J) ( italic_M , italic_Ο‰ , italic_J ) is called Chern-Einstein if its Ricci form ρ 𝜌 \rho italic_ρ satisfies

ρ = Ξ» ⁒ Ο‰ 𝜌 πœ† πœ” \rho=\lambda\omega italic_ρ = italic_Ξ» italic_Ο‰

for some constant Ξ» ∈ ℝ πœ† ℝ \lambda\in\mathbb{R} italic_Ξ» ∈ blackboard_R .


Definition 3.1 .

A commutative semiring (sometimes called a commutative rig β€” commutative ri n g without negative elements) ( R , 0 , 1 , + , β‹… ) 𝑅 0 1 normal-β‹… (R,0,1,+,\cdot) ( italic_R , 0 , 1 , + , β‹… ) consists of a set R 𝑅 R italic_R , two distinguished elements of R 𝑅 R italic_R named 0 0 and 1 1 1 1 , and two binary operations + + + and β‹… normal-β‹… \cdot β‹… , satisfying the following relations for any a , b , c ∈ R π‘Ž 𝑏 𝑐 𝑅 a,b,c\in R italic_a , italic_b , italic_c ∈ italic_R :

0 + a = a a + b = b + a a + ( b + c ) = ( a + b ) + c 1 β‹… a = a a β‹… b = b β‹… a a β‹… ( b β‹… c ) = ( a β‹… b ) β‹… c 0 β‹… a = 0 ( a + b ) β‹… c = ( a β‹… c ) + ( b β‹… c ) 0 π‘Ž π‘Ž π‘Ž 𝑏 𝑏 π‘Ž π‘Ž 𝑏 𝑐 π‘Ž 𝑏 𝑐 missing-subexpression missing-subexpression missing-subexpression β‹… 1 π‘Ž π‘Ž β‹… π‘Ž 𝑏 β‹… 𝑏 π‘Ž β‹… π‘Ž β‹… 𝑏 𝑐 β‹… β‹… π‘Ž 𝑏 𝑐 missing-subexpression missing-subexpression missing-subexpression β‹… 0 π‘Ž 0 β‹… π‘Ž 𝑏 𝑐 β‹… π‘Ž 𝑐 β‹… 𝑏 𝑐 \begin{array}[]{rcl}0+a&=&a\\ a+b&=&b+a\\ a+(b+c)&=&(a+b)+c\\ \\ 1\cdot a&=&a\\ a\cdot b&=&b\cdot a\\ a\cdot(b\cdot c)&=&(a\cdot b)\cdot c\\ \\ 0\cdot a&=&0\\ (a+b)\cdot c&=&(a\cdot c)+(b\cdot c)\end{array} start_ARRAY start_ROW start_CELL 0 + italic_a end_CELL start_CELL = end_CELL start_CELL italic_a end_CELL end_ROW start_ROW start_CELL italic_a + italic_b end_CELL start_CELL = end_CELL start_CELL italic_b + italic_a end_CELL end_ROW start_ROW start_CELL italic_a + ( italic_b + italic_c ) end_CELL start_CELL = end_CELL start_CELL ( italic_a + italic_b ) + italic_c end_CELL end_ROW start_ROW start_CELL end_CELL start_CELL end_CELL start_CELL end_CELL end_ROW start_ROW start_CELL 1 β‹… italic_a end_CELL start_CELL = end_CELL start_CELL italic_a end_CELL end_ROW start_ROW start_CELL italic_a β‹… italic_b end_CELL start_CELL = end_CELL start_CELL italic_b β‹… italic_a end_CELL end_ROW start_ROW start_CELL italic_a β‹… ( italic_b β‹… italic_c ) end_CELL start_CELL = end_CELL start_CELL ( italic_a β‹… italic_b ) β‹… italic_c end_CELL end_ROW start_ROW start_CELL end_CELL start_CELL end_CELL start_CELL end_CELL end_ROW start_ROW start_CELL 0 β‹… italic_a end_CELL start_CELL = end_CELL start_CELL 0 end_CELL end_ROW start_ROW start_CELL ( italic_a + italic_b ) β‹… italic_c end_CELL start_CELL = end_CELL start_CELL ( italic_a β‹… italic_c ) + ( italic_b β‹… italic_c ) end_CELL end_ROW end_ARRAY
Definition 3.4 .

( β™― normal-β™― \sharp β™― ). By recursion on | b | 𝑏 |b| | italic_b | . First define Ο„ 𝜏 \tau italic_Ο„ that maps numeric sizes to their corresponding types. We will revert to using type notation for greater clarity of this definition:

Ο„ ⁒ ( 0 ) = βŠ₯ Ο„ ⁒ ( 1 + n ) = ⊀ ⊎ Ο„ ( n ) 𝜏 0 bottom 𝜏 1 𝑛 fragments top ⊎ Ο„ fragments ( n ) \begin{array}[]{rcl}\tau~{}(0)&=&\bot\\ \tau~{}(1+n)&=&\top\uplus\tau~{}(n)\\ \end{array} start_ARRAY start_ROW start_CELL italic_Ο„ ( 0 ) end_CELL start_CELL = end_CELL start_CELL βŠ₯ end_CELL end_ROW start_ROW start_CELL italic_Ο„ ( 1 + italic_n ) end_CELL start_CELL = end_CELL start_CELL ⊀ ⊎ italic_Ο„ ( italic_n ) end_CELL end_ROW end_ARRAY

so that we can define β™― ⁒ b = Ο„ ⁒ | b | normal-β™― 𝑏 𝜏 𝑏 \sharp\,b=\tau~{}|b| β™― italic_b = italic_Ο„ | italic_b | .


Definition 5

Let 𝔸 𝔸 {\mathbb{A}} blackboard_A be an associative superalgebra. A β„€ 2 subscript β„€ 2 {\mathbb{Z}}_{2} blackboard_Z start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT -graded linear map ⋆ : 𝔸 ⟢ 𝔸 fragments normal-⋆ normal-: A normal-⟢ A \star:{\mathbb{A}}\longrightarrow{\mathbb{A}} ⋆ : blackboard_A ⟢ blackboard_A is called a superinvolution (or β„€ 2 subscript β„€ 2 {\mathbb{Z}}_{2} blackboard_Z start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT -graded involution) if

( a ⁒ b ) ⋆ = ( - 1 ) Ο„ ⁒ ( a ) ⁒ Ο„ ⁒ ( b ) ⁒ b ⋆ ⁒ a ⋆ , ( a ⋆ ) ⋆ = a formulae-sequence superscript π‘Ž 𝑏 ⋆ superscript 1 𝜏 π‘Ž 𝜏 𝑏 superscript 𝑏 ⋆ superscript π‘Ž ⋆ superscript superscript π‘Ž ⋆ ⋆ π‘Ž (ab)^{\star}=(-1)^{\tau(a)\tau(b)}b^{\star}a^{\star},\qquad(a^{\star})^{\star}=a ( italic_a italic_b ) start_POSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT = ( - 1 ) start_POSTSUPERSCRIPT italic_Ο„ ( italic_a ) italic_Ο„ ( italic_b ) end_POSTSUPERSCRIPT italic_b start_POSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT italic_a start_POSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT , ( italic_a start_POSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT ) start_POSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT = italic_a

for any elements a , b ∈ 𝔸 π‘Ž 𝑏 𝔸 a,b\in{\mathbb{A}} italic_a , italic_b ∈ blackboard_A . The pair ( 𝔸 , ⋆ ) 𝔸 normal-⋆ ({\mathbb{A}},\star) ( blackboard_A , ⋆ ) is called a β„€ 2 subscript β„€ 2 {\mathbb{Z}}_{2} blackboard_Z start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT -graded ⋆ normal-⋆ \star ⋆ -algebra.


Definition 5.17 .

An OlΕ‘Γ‘k function is aΒ 6-ary function o π‘œ o italic_o that satisfies

o ⁒ ( x , x , y , y , y , x ) β‰ˆ o ⁒ ( x , y , x , y , x , y ) β‰ˆ o ⁒ ( y , x , x , x , y , y ) . π‘œ π‘₯ π‘₯ 𝑦 𝑦 𝑦 π‘₯ π‘œ π‘₯ 𝑦 π‘₯ 𝑦 π‘₯ 𝑦 π‘œ 𝑦 π‘₯ π‘₯ π‘₯ 𝑦 𝑦 o(x,x,y,y,y,x)\approx o(x,y,x,y,x,y)\approx o(y,x,x,x,y,y). italic_o ( italic_x , italic_x , italic_y , italic_y , italic_y , italic_x ) β‰ˆ italic_o ( italic_x , italic_y , italic_x , italic_y , italic_x , italic_y ) β‰ˆ italic_o ( italic_y , italic_x , italic_x , italic_x , italic_y , italic_y ) .
Definition 5.24 .

A Siggers function is aΒ 6-ary function s 𝑠 s italic_s that satisfies

s ⁒ ( x , y , x , z , y , z ) β‰ˆ s ⁒ ( y , x , z , x , z , y ) . 𝑠 π‘₯ 𝑦 π‘₯ 𝑧 𝑦 𝑧 𝑠 𝑦 π‘₯ 𝑧 π‘₯ 𝑧 𝑦 s(x,y,x,z,y,z)\approx s(y,x,z,x,z,y). italic_s ( italic_x , italic_y , italic_x , italic_z , italic_y , italic_z ) β‰ˆ italic_s ( italic_y , italic_x , italic_z , italic_x , italic_z , italic_y ) .

Definition 2.5 (Choreographic holomorphic sphere) .

A holomorphic sphere u 𝑒 u italic_u in β„‚ ⁒ β„™ k β„‚ superscript β„™ π‘˜ \mathbb{CP}^{k} blackboard_C blackboard_P start_POSTSUPERSCRIPT italic_k end_POSTSUPERSCRIPT is choreographic if

u ∘ Ο„ = Οƒ ∘ u . 𝑒 𝜏 𝜎 𝑒 u\circ\tau=\sigma\circ u. italic_u ∘ italic_Ο„ = italic_Οƒ ∘ italic_u .

Definition 1 .

Let us define

n ⁒ ( p , Ο‰ , Ο‰ β€² ) = m ⁒ ( m ⁒ ( p , Ο‰ ) + 1 , Ο‰ β€² ) . 𝑛 𝑝 πœ” superscript πœ” β€² π‘š π‘š 𝑝 πœ” 1 superscript πœ” β€² n(p,\omega,\omega^{\prime})=m(m(p,\omega)+1,\omega^{\prime}). italic_n ( italic_p , italic_Ο‰ , italic_Ο‰ start_POSTSUPERSCRIPT β€² end_POSTSUPERSCRIPT ) = italic_m ( italic_m ( italic_p , italic_Ο‰ ) + 1 , italic_Ο‰ start_POSTSUPERSCRIPT β€² end_POSTSUPERSCRIPT ) . (24)

Using the definition of m ⁒ ( p ) π‘š 𝑝 m(p) italic_m ( italic_p ) in ( 15 ), n 𝑛 n italic_n is the first geometric scale after m ⁒ ( p ) π‘š 𝑝 m(p) italic_m ( italic_p ) that contains an open circuit.


Definition 2.5 .

Let f : G β†’ G β€² normal-: 𝑓 normal-β†’ 𝐺 superscript 𝐺 normal-β€² f:G\rightarrow G^{\prime} italic_f : italic_G β†’ italic_G start_POSTSUPERSCRIPT β€² end_POSTSUPERSCRIPT be an isogeny of p 𝑝 p italic_p -divisible groups over a base scheme S 𝑆 S italic_S . Then the kernel of f 𝑓 f italic_f is a finite group scheme of rank a power of p 𝑝 p italic_p . If the rank is p i superscript 𝑝 𝑖 p^{i} italic_p start_POSTSUPERSCRIPT italic_i end_POSTSUPERSCRIPT for some constant i ∈ β„€ 𝑖 β„€ i\in\mathbb{Z} italic_i ∈ blackboard_Z , then i 𝑖 i italic_i is called the height of the isogeny f, and we write:

ht ⁒ ( f ) = i . ht 𝑓 𝑖 \mathrm{ht}(f)=i. roman_ht ( italic_f ) = italic_i .

Let ρ : G β†’ G β€² normal-: 𝜌 normal-β†’ 𝐺 superscript 𝐺 normal-β€² \rho:G\rightarrow G^{\prime} italic_ρ : italic_G β†’ italic_G start_POSTSUPERSCRIPT β€² end_POSTSUPERSCRIPT be a quasi-isogeny of p 𝑝 p italic_p -divisible groups. Given n ∈ β„€ 𝑛 β„€ n\in\mathbb{Z} italic_n ∈ blackboard_Z such that p n ⁒ ρ : G β†’ G β€² normal-: superscript 𝑝 𝑛 𝜌 normal-β†’ 𝐺 superscript 𝐺 normal-β€² p^{n}\rho:G\rightarrow G^{\prime} italic_p start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT italic_ρ : italic_G β†’ italic_G start_POSTSUPERSCRIPT β€² end_POSTSUPERSCRIPT is an isogeny, we define the height of the quasi-isogeny ρ 𝜌 \rho italic_ρ to be:

ht ⁒ ( ρ ) = ht ⁒ ( p n ⁒ ρ ) - ht ⁒ ( p n ) . ht 𝜌 ht superscript 𝑝 𝑛 𝜌 ht superscript 𝑝 𝑛 \mathrm{ht}(\rho)=\mathrm{ht}(p^{n}\rho)-\mathrm{ht}(p^{n}). roman_ht ( italic_ρ ) = roman_ht ( italic_p start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT italic_ρ ) - roman_ht ( italic_p start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT ) .

Definition 3.1 (Halfspaces) .

A halfspace is a function h : ℝ n β†’ { Β± 1 } : β„Ž β†’ superscript ℝ 𝑛 plus-or-minus 1 h:\mathbb{R}^{n}\to\{\pm 1\} italic_h : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT β†’ { Β± 1 } such that for some unit vector w ∈ ℝ n 𝑀 superscript ℝ 𝑛 w\in\mathbb{R}^{n} italic_w ∈ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT (called the normal vector ) and threshold t ∈ ℝ 𝑑 ℝ t\in\mathbb{R} italic_t ∈ blackboard_R

h ⁒ ( x ) = sign ⁑ ( ⟨ w , x ⟩ - t ) . β„Ž π‘₯ sign 𝑀 π‘₯ 𝑑 h(x)=\operatorname{sign}(\langle w,x\rangle-t)\,. italic_h ( italic_x ) = roman_sign ( ⟨ italic_w , italic_x ⟩ - italic_t ) .
Definition 3.13 (Halfspace Angle) .

For two halfspaces g , h 𝑔 β„Ž g,h italic_g , italic_h with normal (unit) vectors u , v 𝑒 𝑣 u,v italic_u , italic_v respectively, we will write Ξ± ⁒ ( g , h ) 𝛼 𝑔 β„Ž \alpha(g,h) italic_Ξ± ( italic_g , italic_h ) for the angle between u 𝑒 u italic_u and v 𝑣 v italic_v :

Ξ± ⁒ ( g , h ) := cos - 1 ⁑ ( ⟨ u , v ⟩ ) . assign 𝛼 𝑔 β„Ž superscript 1 𝑒 𝑣 \alpha(g,h)\vcentcolon=\cos^{-1}(\langle u,v\rangle)\,. italic_Ξ± ( italic_g , italic_h ) := roman_cos start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT ( ⟨ italic_u , italic_v ⟩ ) .

Definition 6 (Compositional Exponential Family of Distributions) .

The form of compositional probability distribution of exponential family is given by the probability density function

p ⁒ ( 𝒙 , 𝒉 ; 𝜽 ) ⁒ d ⁒ 𝒙 ⁒ d ⁒ 𝒉 = e ( k ⁒ ( 𝒉 , 𝒙 ; 𝜽 ) - ψ ⁒ ( 𝜽 ) ) ⁒ d ⁒ ΞΌ ⁒ ( 𝒙 ) ⁒ d ⁒ Ξ½ ⁒ ( 𝒉 ) , k ⁒ ( 𝒉 , 𝒙 ; 𝜽 ) = ⟨ 𝒇 ⁒ ( 𝜽 ; 𝒉 ) , π’ˆ ⁒ ( 𝒙 ) ⟩ formulae-sequence 𝑝 𝒙 𝒉 𝜽 𝑑 𝒙 𝑑 𝒉 superscript 𝑒 π‘˜ 𝒉 𝒙 𝜽 πœ“ 𝜽 𝑑 πœ‡ 𝒙 𝑑 𝜈 𝒉 π‘˜ 𝒉 𝒙 𝜽 𝒇 𝜽 𝒉 π’ˆ 𝒙 p(\bm{x},\bm{h};\bm{\theta})d\bm{x}d\bm{h}=e^{(k(\bm{h},\bm{x};\bm{\theta})-% \psi(\bm{\theta}))}d\mu(\bm{x})d\nu(\bm{h}),k(\bm{h},\bm{x};\bm{\theta})=% \langle\bm{f}(\bm{\theta};\bm{h}),\bm{g}(\bm{x})\rangle italic_p ( bold_italic_x , bold_italic_h ; bold_italic_ΞΈ ) italic_d bold_italic_x italic_d bold_italic_h = italic_e start_POSTSUPERSCRIPT ( italic_k ( bold_italic_h , bold_italic_x ; bold_italic_ΞΈ ) - italic_ψ ( bold_italic_ΞΈ ) ) end_POSTSUPERSCRIPT italic_d italic_ΞΌ ( bold_italic_x ) italic_d italic_Ξ½ ( bold_italic_h ) , italic_k ( bold_italic_h , bold_italic_x ; bold_italic_ΞΈ ) = ⟨ bold_italic_f ( bold_italic_ΞΈ ; bold_italic_h ) , bold_italic_g ( bold_italic_x ) ⟩

where 𝐱 𝐱 \bm{x} bold_italic_x is realizable values of a multivariate random variable, k π‘˜ k italic_k is a function called compositional kernel that for a given 𝐑 𝐑 \bm{h} bold_italic_h , k π‘˜ k italic_k is the inner product between certain vector function 𝐠 ⁒ ( 𝐱 ) 𝐠 𝐱 \bm{g}(\bm{x}) bold_italic_g ( bold_italic_x ) , called sufficient statistic , (of which the component functions are linearly independent) and certain vector function 𝐟 ⁒ ( 𝛉 ; 𝐑 ) 𝐟 𝛉 𝐑 \bm{f}(\bm{\theta};\bm{h}) bold_italic_f ( bold_italic_ΞΈ ; bold_italic_h ) , called composition function , ψ ⁒ ( 𝛉 ) πœ“ 𝛉 \psi(\bm{\theta}) italic_ψ ( bold_italic_ΞΈ ) is the normalization factor, and ΞΌ , Ξ½ πœ‡ 𝜈 \mu,\nu italic_ΞΌ , italic_Ξ½ ares the laws on r.v. 𝐱 , 𝐑 𝐱 𝐑 \bm{x},\bm{h} bold_italic_x , bold_italic_h , respectively.


Definition 2.3 (Inversion map) .

We define the inversion map i : β„‚ * β†’ β„‚ * normal-: 𝑖 normal-β†’ superscript β„‚ superscript β„‚ i:\mathbb{C}^{*}\to\mathbb{C}^{*} italic_i : blackboard_C start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT β†’ blackboard_C start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT by

i ⁒ ( z ) = 1 / z 𝑖 𝑧 1 𝑧 i(z)=1/z italic_i ( italic_z ) = 1 / italic_z

Definition 3.9.1 .

(Connection list.) For each subprogram p ⁒ ( i ) ⁒ x ⁒ ( i ) ⁒ y ⁒ ( i ) 𝑝 𝑖 π‘₯ 𝑖 𝑦 𝑖 p(i)~{}x(i)~{}y(i) italic_p ( italic_i ) italic_x ( italic_i ) italic_y ( italic_i ) of the derivation program list [ p ⁒ ( i ) ⁒ x ⁒ ( i ) ⁒ y ⁒ ( i ) ] i = 1 n superscript subscript delimited-[] 𝑝 𝑖 π‘₯ 𝑖 𝑦 𝑖 𝑖 1 𝑛 [p(i)~{}x(i)~{}y(i)]_{i=1}^{n} [ italic_p ( italic_i ) italic_x ( italic_i ) italic_y ( italic_i ) ] start_POSTSUBSCRIPT italic_i = 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT that is obtained from an extended program derivation is generated a list that contains the line labels of the premises used to obtain that subprogram. If k ⁒ ( i ) π‘˜ 𝑖 k(i) italic_k ( italic_i ) is the length of the premise program list of the axiom/theorem labeled a ⁒ ( i ) π‘Ž 𝑖 a(i) italic_a ( italic_i ) that is employed to infer the statement p ⁒ ( i ) ⁒ x ⁒ ( i ) ⁒ y ⁒ ( i ) 𝑝 𝑖 π‘₯ 𝑖 𝑦 𝑖 p(i)~{}x(i)~{}y(i) italic_p ( italic_i ) italic_x ( italic_i ) italic_y ( italic_i ) then the associated connection list, c ⁒ l ⁒ ( i ) : π₯𝐬𝐭 ⁒ [ k ⁒ ( i ) ] : 𝑐 𝑙 𝑖 π₯𝐬𝐭 delimited-[] π‘˜ 𝑖 cl(i):\mathbf{lst}[k(i)] italic_c italic_l ( italic_i ) : bold_lst [ italic_k ( italic_i ) ] , is of the form

c ⁒ l ⁒ ( i ) = [ c ⁒ l ⁒ ( i , 1 ) ⁒ … ⁒ c ⁒ l ⁒ ( i , k ⁒ ( i ) ) ] 𝑐 𝑙 𝑖 delimited-[] 𝑐 𝑙 𝑖 1 … 𝑐 𝑙 𝑖 π‘˜ 𝑖 cl(i)=[cl(i,1)~{}\ldots~{}cl(i,k(i))] italic_c italic_l ( italic_i ) = [ italic_c italic_l ( italic_i , 1 ) … italic_c italic_l ( italic_i , italic_k ( italic_i ) ) ]

where 1 ≀ c ⁒ l ⁒ ( i , 1 ) , … , c ⁒ l ⁒ ( i , k ⁒ ( i ) ) ≀ i - 1 formulae-sequence 1 𝑐 𝑙 𝑖 1 … 𝑐 𝑙 𝑖 π‘˜ 𝑖 𝑖 1 1\leq cl(i,1),~{}\ldots~{},cl(i,k(i))\leq i-1 1 ≀ italic_c italic_l ( italic_i , 1 ) , … , italic_c italic_l ( italic_i , italic_k ( italic_i ) ) ≀ italic_i - 1 are the line labels of the subprograms that make up the sublist

[ p ⁒ ( c ⁒ l ⁒ ( i , j ) ) ⁒ x ⁒ ( c ⁒ l ⁒ ( i , j ) ) ⁒ y ⁒ ( c ⁒ l ⁒ ( i , j ) ) ] j = 1 k ⁒ ( i ) superscript subscript delimited-[] 𝑝 𝑐 𝑙 𝑖 𝑗 π‘₯ 𝑐 𝑙 𝑖 𝑗 𝑦 𝑐 𝑙 𝑖 𝑗 𝑗 1 π‘˜ 𝑖 ~{}[p(cl(i,j))~{}x(cl(i,j))~{}y(cl(i,j))]_{j=1}^{k(i)} [ italic_p ( italic_c italic_l ( italic_i , italic_j ) ) italic_x ( italic_c italic_l ( italic_i , italic_j ) ) italic_y ( italic_c italic_l ( italic_i , italic_j ) ) ] start_POSTSUBSCRIPT italic_j = 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_k ( italic_i ) end_POSTSUPERSCRIPT

that is program and I/O equivalent to the premise program of the axiom/theorem, labeled a ⁒ ( i ) π‘Ž 𝑖 a(i) italic_a ( italic_i ) . Each derived statement of a proof is accompanied by an axiom label followed by a connection list.

Definition 9.2.1 .

(The g ⁒ e ⁒ n 𝑔 𝑒 𝑛 gen italic_g italic_e italic_n function.) A finite and nonempty set t 𝑑 t italic_t defined by

t = g ⁒ e ⁒ n ⁒ [ a ] 𝑑 𝑔 𝑒 𝑛 delimited-[] π‘Ž t=gen[a] italic_t = italic_g italic_e italic_n [ italic_a ] (9.2.1)

is the set of all irreducible extended programs that have proofs that can be derived from a set, a π‘Ž a italic_a , such that a βŠ‚ u ⁒ s ⁒ e ⁒ t π‘Ž 𝑒 𝑠 𝑒 𝑑 a\subset uset italic_a βŠ‚ italic_u italic_s italic_e italic_t contains no redundant elements with respect to the derivations of elements of t 𝑑 t italic_t , i.e. every element of a π‘Ž a italic_a is involved in the derivation of at least one element of t 𝑑 t italic_t . We say that t 𝑑 t italic_t is a derivable set generated by the set a π‘Ž a italic_a and refer to a π‘Ž a italic_a as a set of generators of t 𝑑 t italic_t .


Definition 2.2 ().

The demographic disparity , or Calders-Verwer gap (Calders and Verwer, 2010 ; Kamishima etΒ al . , 2012 ) , Ξ΄ 𝛿 \delta italic_Ξ΄ , is the difference in mean group outcomes between the advantaged and disadvantaged groups:

(1) Ξ΄ = ΞΌ ⁒ ( a ) - ΞΌ ⁒ ( b ) 𝛿 πœ‡ π‘Ž πœ‡ 𝑏 \delta=\mu(a)-\mu(b) italic_Ξ΄ = italic_ΞΌ ( italic_a ) - italic_ΞΌ ( italic_b )

Definition 2.1 .

Let

c ⁒ ( n , k ) = e Ξ³ ⁒ b ⁒ ( n , k ) 𝑐 𝑛 π‘˜ superscript 𝑒 𝛾 𝑏 𝑛 π‘˜ c(n,k)=e^{\gamma}b(n,k) italic_c ( italic_n , italic_k ) = italic_e start_POSTSUPERSCRIPT italic_Ξ³ end_POSTSUPERSCRIPT italic_b ( italic_n , italic_k )

and

c ⁒ ( n ) = e Ξ³ ⁒ b ⁒ ( n ) . 𝑐 𝑛 superscript 𝑒 𝛾 𝑏 𝑛 c(n)=e^{\gamma}b(n). italic_c ( italic_n ) = italic_e start_POSTSUPERSCRIPT italic_Ξ³ end_POSTSUPERSCRIPT italic_b ( italic_n ) .

Definition 3 ( [ 30 ] ) .

The Cassini curve ( or the Cassini ovals ) is a quartic curve defined as the set of points in the plane such that the product of the distances ( denoted by b 2 superscript 𝑏 2 b^{2} italic_b start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) to two fixed points ( a , 0 ) π‘Ž 0 (a,0) ( italic_a , 0 ) and ( - a , 0 ) π‘Ž 0 (-a,0) ( - italic_a , 0 ) is constant :

[ ( x - a ) 2 + y 2 ] ⁒ [ ( x + a ) 2 + y 2 ] = b 4 . delimited-[] superscript π‘₯ π‘Ž 2 superscript 𝑦 2 delimited-[] superscript π‘₯ π‘Ž 2 superscript 𝑦 2 superscript 𝑏 4 [(x-a)^{2}+y^{2}][(x+a)^{2}+y^{2}]=b^{4}. [ ( italic_x - italic_a ) start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT + italic_y start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ] [ ( italic_x + italic_a ) start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT + italic_y start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ] = italic_b start_POSTSUPERSCRIPT 4 end_POSTSUPERSCRIPT . (9)

Definition 2.1 .

∨ : { 0 , 1 } 2 ⟢ { 0 , 1 } fragments : superscript fragments { 0 , 1 } 2 ⟢ fragments { 0 , 1 } \vee:\{0,1\}^{2}\longrightarrow\{0,1\} ∨ : { 0 , 1 } start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ⟢ { 0 , 1 } with

∨ ( 0 , 0 ) = 0 0 0 0 \vee(0,0)=0 ∨ ( 0 , 0 ) = 0
∨ ( 0 , 1 ) = 1 0 1 1 \vee(0,1)=1 ∨ ( 0 , 1 ) = 1
∨ ( 1 , 0 ) = 1 1 0 1 \vee(1,0)=1 ∨ ( 1 , 0 ) = 1
∨ ( 1 , 1 ) = 1 1 1 1 \vee(1,1)=1 ∨ ( 1 , 1 ) = 1

∧ : { 0 , 1 } 2 ⟢ { 0 , 1 } fragments : superscript fragments { 0 , 1 } 2 ⟢ fragments { 0 , 1 } \wedge:\{0,1\}^{2}\longrightarrow\{0,1\} ∧ : { 0 , 1 } start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ⟢ { 0 , 1 } with

∧ ( 0 , 0 ) = 0 0 0 0 \wedge(0,0)=0 ∧ ( 0 , 0 ) = 0
∧ ( 0 , 1 ) = 0 0 1 0 \wedge(0,1)=0 ∧ ( 0 , 1 ) = 0
∧ ( 1 , 0 ) = 0 1 0 0 \wedge(1,0)=0 ∧ ( 1 , 0 ) = 0
∧ ( 1 , 1 ) = 1 1 1 1 \wedge(1,1)=1 ∧ ( 1 , 1 ) = 1

¬ : { 0 , 1 } ⟢ { 0 , 1 } : ⟢ 0 1 0 1 \neg:\{0,1\}\longrightarrow\{0,1\} ¬ : { 0 , 1 } ⟢ { 0 , 1 } with

¬ ⁑ ( 0 ) = 1 0 1 \neg(0)=1 ¬ ( 0 ) = 1
¬ ⁑ ( 1 ) = 0 1 0 \neg(1)=0 ¬ ( 1 ) = 0

Definition 4.1 .

Let G = βŠ• β„“ = 0 s β„€ m β„“ 𝐺 superscript subscript direct-sum β„“ 0 𝑠 subscript β„€ subscript π‘š β„“ G=\bigoplus_{\ell=0}^{s}\mathbb{Z}_{m_{\ell}} italic_G = βŠ• start_POSTSUBSCRIPT roman_β„“ = 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT blackboard_Z start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT be an arbitrary finite abelian group. The (finite) Weyl-Heisenberg group over βŠ• β„“ = 0 s β„€ m β„“ superscript subscript direct-sum normal-β„“ 0 𝑠 subscript β„€ subscript π‘š normal-β„“ \bigoplus_{\ell=0}^{s}\mathbb{Z}_{m_{\ell}} βŠ• start_POSTSUBSCRIPT roman_β„“ = 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT blackboard_Z start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT is the semidirect product G β‹Š ( G Γ— G ) right-normal-factor-semidirect-product 𝐺 𝐺 𝐺 G\rtimes(G\times G) italic_G β‹Š ( italic_G Γ— italic_G ) equipped with the operation

( Ξ» , k , ΞΊ ) β‹… ( Ξ» ~ , k ~ , ΞΊ ~ ) = ( Ξ» + Ξ» ~ + k ~ ⁒ ΞΊ - k ⁒ ΞΊ ~ , k + k ~ , ΞΊ + ΞΊ ~ ) , β‹… πœ† π‘˜ πœ… ~ πœ† ~ π‘˜ ~ πœ… πœ† ~ πœ† ~ π‘˜ πœ… π‘˜ ~ πœ… π‘˜ ~ π‘˜ πœ… ~ πœ… (\lambda,k,\kappa)\cdot(\tilde{\lambda},\tilde{k},\tilde{\kappa})=(\lambda+% \tilde{\lambda}+\tilde{k}\kappa-k\tilde{\kappa},k+\tilde{k},\kappa+\tilde{% \kappa}), ( italic_Ξ» , italic_k , italic_ΞΊ ) β‹… ( ~ start_ARG italic_Ξ» end_ARG , ~ start_ARG italic_k end_ARG , ~ start_ARG italic_ΞΊ end_ARG ) = ( italic_Ξ» + ~ start_ARG italic_Ξ» end_ARG + ~ start_ARG italic_k end_ARG italic_ΞΊ - italic_k ~ start_ARG italic_ΞΊ end_ARG , italic_k + ~ start_ARG italic_k end_ARG , italic_ΞΊ + ~ start_ARG italic_ΞΊ end_ARG ) ,

where k ⁒ ΞΊ ~ ∈ G π‘˜ ~ πœ… 𝐺 k\tilde{\kappa}\in G italic_k ~ start_ARG italic_ΞΊ end_ARG ∈ italic_G is the sum of the component-wise product of the elements in G 𝐺 G italic_G . Set | m | = ∏ β„“ = 0 s m β„“ π‘š superscript subscript product β„“ 0 𝑠 subscript π‘š β„“ \left|m\right|=\prod_{\ell=0}^{s}m_{\ell} | italic_m | = ∏ start_POSTSUBSCRIPT roman_β„“ = 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT , and for each β„“ ∈ { 0 , … , s } β„“ 0 … 𝑠 \ell\in\{0,\ldots,s\} roman_β„“ ∈ { 0 , … , italic_s } , fix a primitive 2 ⁒ m β„“ 2 subscript π‘š β„“ 2m_{\ell} 2 italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT th root of unity Ο„ m β„“ subscript 𝜏 subscript π‘š β„“ \tau_{m_{\ell}} italic_Ο„ start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT where ΞΆ m β„“ = Ο„ m β„“ 2 subscript 𝜁 subscript π‘š β„“ superscript subscript 𝜏 subscript π‘š β„“ 2 \zeta_{m_{\ell}}=\tau_{m_{\ell}}^{2} italic_ΞΆ start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT = italic_Ο„ start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT is the primitive m β„“ subscript π‘š β„“ m_{\ell} italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT th root of unity used to define the modulation operator M m β„“ subscript 𝑀 subscript π‘š β„“ M_{m_{\ell}} italic_M start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT . A standard unitary representation of the finite Weyl-Heisenberg group is

( Ξ» , k , ΞΊ ) ↦ ( ∏ β„“ = 0 s ( - Ο„ m β„“ ) Ξ» β„“ ) ⁒ D m ( k , ΞΊ ) = ( ∏ β„“ = 0 s ( - Ο„ m β„“ ) Ξ» β„“ - k ⁒ ΞΊ ) ⁒ M m ( ΞΊ ) ⁒ T m ( k ) ∈ U ⁒ ( | m | ) , maps-to πœ† π‘˜ πœ… superscript subscript product β„“ 0 𝑠 superscript subscript 𝜏 subscript π‘š β„“ subscript πœ† β„“ superscript subscript 𝐷 π‘š π‘˜ πœ… superscript subscript product β„“ 0 𝑠 superscript subscript 𝜏 subscript π‘š β„“ subscript πœ† β„“ π‘˜ πœ… superscript subscript 𝑀 π‘š πœ… superscript subscript 𝑇 π‘š π‘˜ π‘ˆ π‘š (\lambda,k,\kappa)\mapsto\left(\prod_{\ell=0}^{s}(-\tau_{m_{\ell}})^{\lambda_{% \ell}}\right)D_{m}^{(k,\kappa)}=\left(\prod_{\ell=0}^{s}(-\tau_{m_{\ell}})^{% \lambda_{\ell}-k\kappa}\right)M_{m}^{(\kappa)}T_{m}^{(k)}\in U(\left|m\right|)\,, ( italic_Ξ» , italic_k , italic_ΞΊ ) ↦ ( ∏ start_POSTSUBSCRIPT roman_β„“ = 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT ( - italic_Ο„ start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT ) start_POSTSUPERSCRIPT italic_Ξ» start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUPERSCRIPT ) italic_D start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_k , italic_ΞΊ ) end_POSTSUPERSCRIPT = ( ∏ start_POSTSUBSCRIPT roman_β„“ = 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT ( - italic_Ο„ start_POSTSUBSCRIPT italic_m start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT end_POSTSUBSCRIPT ) start_POSTSUPERSCRIPT italic_Ξ» start_POSTSUBSCRIPT roman_β„“ end_POSTSUBSCRIPT - italic_k italic_ΞΊ end_POSTSUPERSCRIPT ) italic_M start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_ΞΊ ) end_POSTSUPERSCRIPT italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_k ) end_POSTSUPERSCRIPT ∈ italic_U ( | italic_m | ) ,

where U ⁒ ( | m | ) π‘ˆ π‘š U(\left|m\right|) italic_U ( | italic_m | ) is the set of all | m | Γ— | m | π‘š π‘š \left|m\right|\times\left|m\right| | italic_m | Γ— | italic_m | unitaries.

We define Οƒ : G Γ— G β†’ U ⁒ ( | m | ) : 𝜎 β†’ 𝐺 𝐺 π‘ˆ π‘š \sigma:G\times G\rightarrow U(\left|m\right|) italic_Οƒ : italic_G Γ— italic_G β†’ italic_U ( | italic_m | ) by Οƒ ⁒ ( k , ΞΊ ) = M m ( ΞΊ ) ⁒ T m ( k ) 𝜎 π‘˜ πœ… superscript subscript 𝑀 π‘š πœ… subscript superscript 𝑇 π‘˜ π‘š \sigma(k,\kappa)=M_{m}^{(\kappa)}T^{(k)}_{m} italic_Οƒ ( italic_k , italic_ΞΊ ) = italic_M start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_ΞΊ ) end_POSTSUPERSCRIPT italic_T start_POSTSUPERSCRIPT ( italic_k ) end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT . If | m | π‘š \left|m\right| | italic_m | is odd, we further define the mapping Ο€ : G Γ— G β†’ U ⁒ ( | m | ⁒ ( | m | - 1 ) / 2 ) : πœ‹ β†’ 𝐺 𝐺 π‘ˆ π‘š π‘š 1 2 \pi:G\times G\rightarrow U(\left|m\right|(\left|m\right|-1)/2) italic_Ο€ : italic_G Γ— italic_G β†’ italic_U ( | italic_m | ( | italic_m | - 1 ) / 2 ) as

Ο€ ⁒ ( k , ΞΊ ) = I ( | m | - 1 ) / 2 βŠ— ( M m ( ΞΊ ) ⁒ T m ( k ) ) . πœ‹ π‘˜ πœ… tensor-product subscript 𝐼 π‘š 1 2 superscript subscript 𝑀 π‘š πœ… subscript superscript 𝑇 π‘˜ π‘š \pi(k,\kappa)=I_{(\left|m\right|-1)/2}\otimes\left(M_{m}^{(\kappa)}T^{(k)}_{m}% \right). italic_Ο€ ( italic_k , italic_ΞΊ ) = italic_I start_POSTSUBSCRIPT ( | italic_m | - 1 ) / 2 end_POSTSUBSCRIPT βŠ— ( italic_M start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_ΞΊ ) end_POSTSUPERSCRIPT italic_T start_POSTSUPERSCRIPT ( italic_k ) end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT ) .

Definition 2.1 (Admissible trajectory-control pairs and costs) .

For every z ∈ I ⁒ R n βˆ– 𝐂 𝑧 normal-I superscript normal-R 𝑛 𝐂 z\in{{{\rm I\mskip-3.5mu R}}}^{n}\setminus\mathbf{C} italic_z ∈ roman_I roman_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT βˆ– bold_C , we will say that ( x , u ) π‘₯ 𝑒 (x,u) ( italic_x , italic_u ) is an admissible trajectory-control pair from z 𝑧 z italic_z for the control system

(8) x Λ™ = f ⁒ ( x , u ) , x ⁒ ( 0 ) = z formulae-sequence Λ™ π‘₯ 𝑓 π‘₯ 𝑒 π‘₯ 0 𝑧 \dot{x}=f(x,u),\quad x(0)=z Λ™ start_ARG italic_x end_ARG = italic_f ( italic_x , italic_u ) , italic_x ( 0 ) = italic_z

if there exists T x ≀ + ∞ subscript 𝑇 π‘₯ T_{x}\leq+\infty italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT ≀ + ∞ such that u ∈ L l ⁒ o ⁒ c ∞ ⁒ ( [ 0 , T x ) , U ) 𝑒 subscript superscript 𝐿 𝑙 π‘œ 𝑐 0 subscript 𝑇 π‘₯ π‘ˆ u\in L^{\infty}_{loc}([0,T_{x}),U) italic_u ∈ italic_L start_POSTSUPERSCRIPT ∞ end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_l italic_o italic_c end_POSTSUBSCRIPT ( [ 0 , italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT ) , italic_U ) and x π‘₯ x italic_x is a CarathΓ©odory solution of ( 8 ) in [ 0 , T x ) 0 subscript 𝑇 π‘₯ [0,T_{x}) [ 0 , italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT ) corresponding to u 𝑒 u italic_u , verifying

x ⁒ ( [ 0 , T x ) ) βŠ‚ I ⁒ R n \ 𝐂 , and, if T x < + ∞ , lim t β†’ T x - ⁑ 𝐝 ⁒ ( x ⁒ ( t ) ) = 0 formulae-sequence π‘₯ 0 subscript 𝑇 π‘₯ \ I superscript R 𝑛 𝐂 and, if T x < + ∞ , subscript β†’ 𝑑 subscript superscript 𝑇 π‘₯ 𝐝 π‘₯ 𝑑 0 x([0,T_{x}))\subset{{{\rm I\mskip-3.5mu R}}}^{n}\backslash\mathbf{C},\ \ % \displaystyle\text{and, if $T_{x}<+\infty$,}\ \ \lim_{t\to T^{-}_{x}}{\bf d}(x% (t))=0 italic_x ( [ 0 , italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT ) ) βŠ‚ roman_I roman_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT \ bold_C , and, if italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT < + ∞ , roman_lim start_POSTSUBSCRIPT italic_t β†’ italic_T start_POSTSUPERSCRIPT - end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT end_POSTSUBSCRIPT bold_d ( italic_x ( italic_t ) ) = 0

(notice that such a solution might be not unique). We shall use π’œ f ⁒ ( z ) subscript π’œ 𝑓 𝑧 {\mathcal{A}}_{f}({z}) caligraphic_A start_POSTSUBSCRIPT italic_f end_POSTSUBSCRIPT ( italic_z ) to denote the family of admissible trajectory-control pairs ( x , u ) π‘₯ 𝑒 (x,u) ( italic_x , italic_u ) from z 𝑧 z italic_z for the control system ( 8 ) . Moreover, we will call cost associated to ( x , u ) ∈ π’œ f ⁒ ( z ) π‘₯ 𝑒 subscript π’œ 𝑓 𝑧 (x,u)\in{\mathcal{A}}_{f}({z}) ( italic_x , italic_u ) ∈ caligraphic_A start_POSTSUBSCRIPT italic_f end_POSTSUBSCRIPT ( italic_z ) the function

x 0 ⁒ ( t ) := ∫ 0 t l ⁒ ( x ⁒ ( Ο„ ) , u ⁒ ( Ο„ ) ) ⁒ 𝑑 Ο„ βˆ€ t ∈ [ 0 , T x ) . formulae-sequence assign superscript π‘₯ 0 𝑑 superscript subscript 0 𝑑 𝑙 π‘₯ 𝜏 𝑒 𝜏 differential-d 𝜏 for-all 𝑑 0 subscript 𝑇 π‘₯ x^{0}(t):=\int_{0}^{t}l(x(\tau),u(\tau))\,d\tau\ \ \forall t\in[0,T_{x}). italic_x start_POSTSUPERSCRIPT 0 end_POSTSUPERSCRIPT ( italic_t ) := ∫ start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_t end_POSTSUPERSCRIPT italic_l ( italic_x ( italic_Ο„ ) , italic_u ( italic_Ο„ ) ) italic_d italic_Ο„ βˆ€ italic_t ∈ [ 0 , italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT ) .

If T x < + ∞ subscript 𝑇 π‘₯ T_{x}<+\infty italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT < + ∞ , we extend continuously ( x 0 , x ) superscript π‘₯ 0 π‘₯ (x^{0},x) ( italic_x start_POSTSUPERSCRIPT 0 end_POSTSUPERSCRIPT , italic_x ) to [ 0 , + ∞ ) 0 [0,+\infty) [ 0 , + ∞ ) , by setting

( x 0 , x ) ⁒ ( t ) = lim t β†’ T x - ⁑ ( x 0 , x ) ⁒ ( t ) βˆ€ t β‰₯ T x . formulae-sequence superscript π‘₯ 0 π‘₯ 𝑑 subscript β†’ 𝑑 superscript subscript 𝑇 π‘₯ superscript π‘₯ 0 π‘₯ 𝑑 for-all 𝑑 subscript 𝑇 π‘₯ (x^{0},x)(t)=\lim_{t\to T_{x}^{-}}(x^{0},x)(t)\qquad\forall t\geq T_{x}. ( italic_x start_POSTSUPERSCRIPT 0 end_POSTSUPERSCRIPT , italic_x ) ( italic_t ) = roman_lim start_POSTSUBSCRIPT italic_t β†’ italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT start_POSTSUPERSCRIPT - end_POSTSUPERSCRIPT end_POSTSUBSCRIPT ( italic_x start_POSTSUPERSCRIPT 0 end_POSTSUPERSCRIPT , italic_x ) ( italic_t ) βˆ€ italic_t β‰₯ italic_T start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT .

From now on, we will always consider admissible trajectories and associated costs defined on [ 0 , + ∞ ) 0 [0,+\infty) [ 0 , + ∞ ) .

Definition 3.1 ( W π‘Š W italic_W -Feedback) .

Let W π‘Š W italic_W be a p 0 subscript 𝑝 0 {p_{0}} italic_p start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT -MRF with p 0 β‰₯ 0 subscript 𝑝 0 0 {p_{0}}\geq 0 italic_p start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT β‰₯ 0 for ( f , l , 𝐂 ) 𝑓 𝑙 𝐂 (f,l,{\bf C}) ( italic_f , italic_l , bold_C ) and fix a selection p ⁒ ( x ) ∈ D * ⁒ W ⁒ ( x ) 𝑝 π‘₯ superscript 𝐷 π‘Š π‘₯ p(x)\in D^{*}W(x) italic_p ( italic_x ) ∈ italic_D start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT italic_W ( italic_x ) for any x ∈ I ⁒ R n βˆ– 𝐂 π‘₯ normal-I superscript normal-R 𝑛 𝐂 x\in{{{\rm I\mskip-3.5mu R}}}^{n}\setminus{\bf C} italic_x ∈ roman_I roman_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT βˆ– bold_C . Let N 𝑁 N italic_N be the same as in Proposition 3.1 . We call W π‘Š W italic_W -feedback for the control system

(21) x Λ™ = f ⁒ ( x , u ) Λ™ π‘₯ 𝑓 π‘₯ 𝑒 \dot{x}=f(x,u) Λ™ start_ARG italic_x end_ARG = italic_f ( italic_x , italic_u )

a map

K : x ↦ K ( x ) ∈ U ∩ B ( 0 , N ( W ( x ) ) fragments K : x maps-to K fragments ( x ) U B fragments ( 0 , N fragments ( W fragments ( x ) ) K:x\mapsto K(x)\in U\cap B(0,N(W(x)) italic_K : italic_x ↦ italic_K ( italic_x ) ∈ italic_U ∩ italic_B ( 0 , italic_N ( italic_W ( italic_x ) )

verifying

(22) ⟨ p ⁒ ( x ) , f ⁒ ( x , K ⁒ ( x ) ) ⟩ + p 0 ⁒ l ⁒ ( x , K ⁒ ( x ) ) < - Ξ³ ⁒ ( W ⁒ ( x ) ) 𝑝 π‘₯ 𝑓 π‘₯ 𝐾 π‘₯ subscript 𝑝 0 𝑙 π‘₯ 𝐾 π‘₯ 𝛾 π‘Š π‘₯ \langle p(x),f(x,K(x))\rangle+{p_{0}}\,l(x,K(x))<-\gamma(W(x)) ⟨ italic_p ( italic_x ) , italic_f ( italic_x , italic_K ( italic_x ) ) ⟩ + italic_p start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT italic_l ( italic_x , italic_K ( italic_x ) ) < - italic_Ξ³ ( italic_W ( italic_x ) )

for every x ∈ I ⁒ R n βˆ– 𝐂 π‘₯ normal-I superscript normal-R 𝑛 𝐂 x\in{{{\rm I\mskip-3.5mu R}}}^{n}\setminus{\bf C} italic_x ∈ roman_I roman_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT βˆ– bold_C .


Definition 2.1.1

A vector space β„° β„° \mathcal{E} caligraphic_E over β„‚ β„‚ \mathbb{C} blackboard_C is called an algebra if β„° β„° \mathcal{E} caligraphic_E is endowed with a multiplication map

ΞΌ : β„° Γ— β„° ⟼ β„° : πœ‡ ⟼ β„° β„° β„° \mu:\mathcal{E}\times\mathcal{E}\longmapsto\mathcal{E} italic_ΞΌ : caligraphic_E Γ— caligraphic_E ⟼ caligraphic_E

such that ΞΌ πœ‡ \mu italic_ΞΌ is bilinear and associative. The multiplication between 2 elements x , y ∈ β„° π‘₯ 𝑦 β„° x,y\in\mathcal{E} italic_x , italic_y ∈ caligraphic_E is usually denoted by x . y formulae-sequence π‘₯ 𝑦 x.y italic_x . italic_y , i.e. ΞΌ ⁒ ( x , y ) = x . y formulae-sequence πœ‡ π‘₯ 𝑦 π‘₯ 𝑦 \mu(x,y)=x.y italic_ΞΌ ( italic_x , italic_y ) = italic_x . italic_y . Thus for all x , y , z ∈ β„° π‘₯ 𝑦 𝑧 β„° x,y,z\in\mathcal{E} italic_x , italic_y , italic_z ∈ caligraphic_E and Ξ» ∈ β„‚ πœ† β„‚ \lambda\in\mathbb{C} italic_Ξ» ∈ blackboard_C , the conditions of an algebra are given as follows:

  1. 1.

    x . ( Ξ» ⁒ y + z ) = Ξ» ⁒ x ⁒ y + x ⁒ z formulae-sequence π‘₯ πœ† 𝑦 𝑧 πœ† π‘₯ 𝑦 π‘₯ 𝑧 x.(\lambda y+z)=\lambda xy+xz italic_x . ( italic_Ξ» italic_y + italic_z ) = italic_Ξ» italic_x italic_y + italic_x italic_z and

  2. 2.

    ( x . y ) . z = x . z + y . z fragments fragments ( x . y ) . z x . z y . z (x.y).z=x.z+y.z ( italic_x . italic_y ) . italic_z = italic_x . italic_z + italic_y . italic_z .

Definition 2.1.2

Suppose there is an element e ∈ π’œ 𝑒 π’œ e\in\mathcal{A} italic_e ∈ caligraphic_A satisfying

e . x = x . e = x formulae-sequence 𝑒 π‘₯ π‘₯ 𝑒 π‘₯ e.x=x.e=x italic_e . italic_x = italic_x . italic_e = italic_x

for all x ∈ π’œ π‘₯ π’œ x\in\mathcal{A} italic_x ∈ caligraphic_A . Then π’œ π’œ \mathcal{A} caligraphic_A is called a unital algebra and the element e 𝑒 e italic_e is called identity element or unit.

It is direct from the definition of the neutral element that in case of existence, the neutral element is unique. It should be mentioned that not every algebra is a unital algebra. Indeed, the space of all real valued functions defined on ℝ ℝ \mathbb{R} blackboard_R , whose limit at infinity is 0, is an algebra under the point wise multiplication without a unit.


Definition 2 .

Weak full extraction holds if, given v : T β†’ 𝐑 : 𝑣 β†’ 𝑇 𝐑 v:T\to{\bf R} italic_v : italic_T β†’ bold_R , there exists a menu of contracts { c ⁒ ( t ) ∈ 𝐑 S : t ∈ T } conditional-set 𝑐 𝑑 superscript 𝐑 𝑆 𝑑 𝑇 \{c(t)\in{\bf R}^{S}:t\in T\} { italic_c ( italic_t ) ∈ bold_R start_POSTSUPERSCRIPT italic_S end_POSTSUPERSCRIPT : italic_t ∈ italic_T } such that for each t ∈ T 𝑑 𝑇 t\in T italic_t ∈ italic_T ,

v ⁒ ( t ) - Ο€ ⁒ ( t ) β‹… c ⁒ ( t ) = 0 𝑣 𝑑 β‹… πœ‹ 𝑑 𝑐 𝑑 0 v(t)-\pi(t)\cdot c(t)=0 italic_v ( italic_t ) - italic_Ο€ ( italic_t ) β‹… italic_c ( italic_t ) = 0

and

v ⁒ ( t ) - Ο€ ⁒ ( t ) β‹… c ⁒ ( s ) ≀ 0 βˆ€ s β‰  t formulae-sequence 𝑣 𝑑 β‹… πœ‹ 𝑑 𝑐 𝑠 0 for-all 𝑠 𝑑 v(t)-\pi(t)\cdot c(s)\leq 0\ \ \forall s\not=t italic_v ( italic_t ) - italic_Ο€ ( italic_t ) β‹… italic_c ( italic_s ) ≀ 0 βˆ€ italic_s β‰  italic_t

for some Ο€ ⁒ ( t ) ∈ Ξ  ⁒ ( t ) πœ‹ 𝑑 Ξ  𝑑 \pi(t)\in\Pi(t) italic_Ο€ ( italic_t ) ∈ roman_Ξ  ( italic_t ) .


Definition 13 .

An arrangement of tuples ( w 1 ( 1 ) , … , w q - 1 ( 1 ) ) , … , ( w 1 ( q ) , … , w q - 1 ( q ) ) subscript superscript 𝑀 1 1 … superscript subscript 𝑀 π‘ž 1 1 … superscript subscript 𝑀 1 π‘ž … superscript subscript 𝑀 π‘ž 1 π‘ž (w^{(1)}_{1},\ldots,w_{q-1}^{(1)}),\ldots,(w_{1}^{(q)},\ldots,w_{q-1}^{(q)}) ( italic_w start_POSTSUPERSCRIPT ( 1 ) end_POSTSUPERSCRIPT start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , … , italic_w start_POSTSUBSCRIPT italic_q - 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( 1 ) end_POSTSUPERSCRIPT ) , … , ( italic_w start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_q ) end_POSTSUPERSCRIPT , … , italic_w start_POSTSUBSCRIPT italic_q - 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_q ) end_POSTSUPERSCRIPT ) (understood, depending on the context, as element of β„€ q ⁒ ( q - 1 ) superscript β„€ π‘ž π‘ž 1 \mathbb{Z}^{q(q-1)} blackboard_Z start_POSTSUPERSCRIPT italic_q ( italic_q - 1 ) end_POSTSUPERSCRIPT or β„€ N q ⁒ ( q - 1 ) superscript subscript β„€ 𝑁 π‘ž π‘ž 1 \mathbb{Z}_{N}^{q(q-1)} blackboard_Z start_POSTSUBSCRIPT italic_N end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_q ( italic_q - 1 ) end_POSTSUPERSCRIPT ) is feasible if

βˆ€ j = 3 , … , q : : for-all 𝑗 3 … π‘ž absent \displaystyle\forall j=3,\ldots,q: βˆ€ italic_j = 3 , … , italic_q :
⁒ w 1 ( j ) = βˆ‘ a = 1 q - 1 w a ( j - 2 ) - βˆ‘ a = 2 q - 1 w a ( j - 1 ) superscript subscript 𝑀 1 𝑗 superscript subscript π‘Ž 1 π‘ž 1 superscript subscript 𝑀 π‘Ž 𝑗 2 superscript subscript π‘Ž 2 π‘ž 1 superscript subscript 𝑀 π‘Ž 𝑗 1 \displaystyle\qquad w_{1}^{(j)}=\sum_{a=1}^{q-1}w_{a}^{(j-2)}-\sum_{a=2}^{q-1}% w_{a}^{(j-1)} italic_w start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j ) end_POSTSUPERSCRIPT = βˆ‘ start_POSTSUBSCRIPT italic_a = 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_q - 1 end_POSTSUPERSCRIPT italic_w start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j - 2 ) end_POSTSUPERSCRIPT - βˆ‘ start_POSTSUBSCRIPT italic_a = 2 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_q - 1 end_POSTSUPERSCRIPT italic_w start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j - 1 ) end_POSTSUPERSCRIPT (7)
⁒ βˆ€ a = 2 , … , q - 1 : w a ( j ) = - w a - 1 ( j - 2 ) + w a - 1 ( j - 1 ) + w a ( j - 1 ) : for-all π‘Ž 2 … π‘ž 1 superscript subscript 𝑀 π‘Ž 𝑗 superscript subscript 𝑀 π‘Ž 1 𝑗 2 superscript subscript 𝑀 π‘Ž 1 𝑗 1 superscript subscript 𝑀 π‘Ž 𝑗 1 \displaystyle\qquad\forall a=2,\ldots,q-1:w_{a}^{(j)}=-w_{a-1}^{(j-2)}+w_{a-1}% ^{(j-1)}+w_{a}^{(j-1)} βˆ€ italic_a = 2 , … , italic_q - 1 : italic_w start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j ) end_POSTSUPERSCRIPT = - italic_w start_POSTSUBSCRIPT italic_a - 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j - 2 ) end_POSTSUPERSCRIPT + italic_w start_POSTSUBSCRIPT italic_a - 1 end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j - 1 ) end_POSTSUPERSCRIPT + italic_w start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ( italic_j - 1 ) end_POSTSUPERSCRIPT (8)

For q β‰₯ 3 π‘ž 3 q\geq 3 italic_q β‰₯ 3 and N β‰₯ 1 𝑁 1 N\geq 1 italic_N β‰₯ 1 we let β„° := β„° ⁒ ( q , N ) βŠ† β„€ N q ⁒ ( q - 1 ) assign β„° β„° π‘ž 𝑁 superscript subscript β„€ 𝑁 π‘ž π‘ž 1 \mathcal{E}:=\mathcal{E}(q,N)\subseteq\mathbb{Z}_{N}^{q(q-1)} caligraphic_E := caligraphic_E ( italic_q , italic_N ) βŠ† blackboard_Z start_POSTSUBSCRIPT italic_N end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_q ( italic_q - 1 ) end_POSTSUPERSCRIPT to be the set of all feasible arrangements of tuples.


Definition 4.6 .

Let A 𝐴 A italic_A be a Lie algebroid over the presymplectic manifold ( M , Ο‰ ) 𝑀 πœ” (M,\omega) ( italic_M , italic_Ο‰ ) . A D 𝐷 D italic_D -momentum section ΞΌ ∈ Ξ“ ⁒ ( M , A * ) πœ‡ normal-Ξ“ 𝑀 superscript 𝐴 \mu\in\Gamma(M,A^{*}) italic_ΞΌ ∈ roman_Ξ“ ( italic_M , italic_A start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ) is called bracket-compatible if

(15) ( 𝐝 ⁒ ΞΌ ) ⁒ ( a , b ) = - Ο‰ ⁒ ( ρ ⁒ a , ρ ⁒ b ) 𝐝 πœ‡ π‘Ž 𝑏 πœ” 𝜌 π‘Ž 𝜌 𝑏 (\mathbf{d}\mu)(a,b)=-\omega(\rho a,\rho b) ( bold_d italic_ΞΌ ) ( italic_a , italic_b ) = - italic_Ο‰ ( italic_ρ italic_a , italic_ρ italic_b )

for all a , b ∈ Ξ“ ⁒ ( M , A ) π‘Ž 𝑏 normal-Ξ“ 𝑀 𝐴 a,b\in\Gamma(M,A) italic_a , italic_b ∈ roman_Ξ“ ( italic_M , italic_A ) .


Definition 1 .

Perruquetti etΒ al. ( 2008 ) Let f : ℝ n β†’ ℝ n normal-: 𝑓 normal-β†’ superscript ℝ 𝑛 superscript ℝ 𝑛 f:\mathbb{R}^{n}\rightarrow\mathbb{R}^{n} italic_f : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT β†’ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT be a piecewise continuous function with f ⁒ ( 0 ) = 0 𝑓 0 0 f(0)=0 italic_f ( 0 ) = 0 , ψ ⁒ ( t , x 0 ) πœ“ 𝑑 subscript π‘₯ 0 \psi(t,x_{0}) italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) is said to be a right-maximally defined solution of

x Λ™ = - f ⁒ ( x ) Λ™ π‘₯ 𝑓 π‘₯ \dot{x}=-f(x) Λ™ start_ARG italic_x end_ARG = - italic_f ( italic_x ) (1)

if ψ ⁒ ( t , x 0 ) πœ“ 𝑑 subscript π‘₯ 0 \psi(t,x_{0}) italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) is such that

d ⁒ ψ ⁒ ( t , x 0 ) d ⁒ t = - f ⁒ ( ψ ⁒ ( t , x 0 ) ) , ψ ⁒ ( 0 , x 0 ) = x 0 , βˆ€ t ∈ [ t 0 , T m ⁒ ( x 0 ) ) , βˆ€ x 0 ∈ π’Ÿ βˆ– { 0 } formulae-sequence 𝑑 πœ“ 𝑑 subscript π‘₯ 0 𝑑 𝑑 𝑓 πœ“ 𝑑 subscript π‘₯ 0 formulae-sequence πœ“ 0 subscript π‘₯ 0 subscript π‘₯ 0 formulae-sequence for-all 𝑑 subscript 𝑑 0 subscript 𝑇 π‘š subscript π‘₯ 0 for-all subscript π‘₯ 0 π’Ÿ 0 \frac{{d\psi(t,x_{0})}}{{d}t}=-f(\psi(t,x_{0})),~{}~{}\psi(0,x_{0})=x_{0},\ \ % \ \ \forall t\in[t_{0},T_{m}(x_{0})),\forall x_{0}\in{\cal D}\setminus\{0\} divide start_ARG italic_d italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) end_ARG start_ARG italic_d italic_t end_ARG = - italic_f ( italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) ) , italic_ψ ( 0 , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) = italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , βˆ€ italic_t ∈ [ italic_t start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) ) , βˆ€ italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ∈ caligraphic_D βˆ– { 0 }

where T m ⁒ ( x 0 ) ∈ ( 0 , ∞ ) subscript 𝑇 π‘š subscript π‘₯ 0 0 T_{m}(x_{0})\in(0,\infty) italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) ∈ ( 0 , ∞ ) is the maximal possible real number with the above property, or plus infinity. Moreover,Β ( 1 ) is said to have a unique solution in forward time if for any x 0 ∈ ℝ n subscript π‘₯ 0 superscript ℝ 𝑛 x_{0}\in\mathbb{R}^{n} italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ∈ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT and two right-maximally defined solutions ofΒ ( 1 ), ψ ⁒ ( t , x 0 ) πœ“ 𝑑 subscript π‘₯ 0 \psi(t,x_{0}) italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) and Ο• ⁒ ( t , x 0 ) italic-Ο• 𝑑 subscript π‘₯ 0 \phi(t,x_{0}) italic_Ο• ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) defined on [ t 0 , T m ψ ] subscript 𝑑 0 superscript subscript 𝑇 π‘š πœ“ [t_{0},T_{m}^{\psi}] [ italic_t start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_ψ end_POSTSUPERSCRIPT ] and [ t 0 , T m ψ ] subscript 𝑑 0 superscript subscript 𝑇 π‘š πœ“ [t_{0},T_{m}^{\psi}] [ italic_t start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_ψ end_POSTSUPERSCRIPT ] , respectively, there exists t 0 < T m ⁒ ( x 0 ) < min ⁑ ( T m ψ ⁒ ( x 0 ) , T m Ο• ⁒ ( x 0 ) ) subscript 𝑑 0 subscript 𝑇 π‘š subscript π‘₯ 0 superscript subscript 𝑇 π‘š πœ“ subscript π‘₯ 0 superscript subscript 𝑇 π‘š italic-Ο• subscript π‘₯ 0 t_{0}<T_{m}(x_{0})<\min(T_{m}^{\psi}(x_{0}),T_{m}^{\phi}(x_{0})) italic_t start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT < italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) < roman_min ( italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_ψ end_POSTSUPERSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) , italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT start_POSTSUPERSCRIPT italic_Ο• end_POSTSUPERSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) ) such that ψ ⁒ ( t , x 0 ) = Ο• ⁒ ( t , x 0 ) πœ“ 𝑑 subscript π‘₯ 0 italic-Ο• 𝑑 subscript π‘₯ 0 \psi(t,x_{0})=\phi(t,x_{0}) italic_ψ ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) = italic_Ο• ( italic_t , italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) for all t ∈ [ t 0 , T m ⁒ ( x 0 ) ) 𝑑 subscript 𝑑 0 subscript 𝑇 π‘š subscript π‘₯ 0 t\in[t_{0},T_{m}(x_{0})) italic_t ∈ [ italic_t start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , italic_T start_POSTSUBSCRIPT italic_m end_POSTSUBSCRIPT ( italic_x start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ) ) .


Definition 2.3 .

Let A 𝐴 A italic_A be a finite set equipped with a sign function; that is, a function sgn : A β†’ { Β± 1 } : sgn β†’ 𝐴 plus-or-minus 1 \mathrm{sgn}\colon A\rightarrow\{\pm 1\} roman_sgn : italic_A β†’ { Β± 1 } . A sign-reversing involution ΞΉ : A β†’ A : πœ„ β†’ 𝐴 𝐴 \iota\colon A\rightarrow A italic_ΞΉ : italic_A β†’ italic_A is an involution such that for every a ∈ A π‘Ž 𝐴 a\in A italic_a ∈ italic_A

sgn ⁒ ( ΞΉ ⁒ ( a ) ) = - sgn ⁒ ( a ) . sgn πœ„ π‘Ž sgn π‘Ž \mathrm{sgn}(\iota(a))=-\mathrm{sgn}(a). roman_sgn ( italic_ΞΉ ( italic_a ) ) = - roman_sgn ( italic_a ) .

Definition 1

Let a triangle have angles ( Ξ± , Ξ² , Ξ³ ) 𝛼 𝛽 𝛾 (\alpha,\beta,\gamma) ( italic_Ξ± , italic_Ξ² , italic_Ξ³ ) . We define

s = 2 ⁒ sin ⁑ ( Ξ± / 2 ) . 𝑠 2 𝛼 2 s=2\sin(\alpha/2). italic_s = 2 roman_sin ( italic_Ξ± / 2 ) .

Definition 3.2 .

Let 𝒳 = 𝒴 = { 0 , 1 } ≀ d m 𝒳 𝒴 subscript superscript 0 1 π‘š absent 𝑑 \mathcal{X}=\mathcal{Y}=\{0,1\}^{m}_{\leq d} caligraphic_X = caligraphic_Y = { 0 , 1 } start_POSTSUPERSCRIPT italic_m end_POSTSUPERSCRIPT start_POSTSUBSCRIPT ≀ italic_d end_POSTSUBSCRIPT and

f ⁒ ( x , y ) = { 1 if ⟨ x , y ⟩ = 0 0 otherwise . 𝑓 π‘₯ 𝑦 cases 1 if ⟨ x , y ⟩ = 0 0 otherwise f(x,y)=\begin{cases}1&\text{if $\langle x,y\rangle=0$}\\ 0&\text{otherwise}\end{cases}. italic_f ( italic_x , italic_y ) = { start_ROW start_CELL 1 end_CELL start_CELL if ⟨ italic_x , italic_y ⟩ = 0 end_CELL end_ROW start_ROW start_CELL 0 end_CELL start_CELL otherwise end_CELL end_ROW .

Definition 1

A High General Granular Operator Space ( GFSG ) π•Š π•Š \mathbb{S} blackboard_S shall be a structure of the form π•Š = ⟨ π•Š Β― , 𝒒 , l , u , 𝐏 , ≀ , ∨ , ∧ , βŠ₯ , ⊀ ⟩ π•Š Β― π•Š 𝒒 𝑙 𝑒 𝐏 bottom top \mathbb{S}\,=\,\left\langle\underline{\mathbb{S}},\mathcal{G},l,u,\mathbf{P},% \leq,\vee,\wedge,\bot,\top\right\rangle blackboard_S = ⟨ Β― start_ARG blackboard_S end_ARG , caligraphic_G , italic_l , italic_u , bold_P , ≀ , ∨ , ∧ , βŠ₯ , ⊀ ⟩ with π•Š Β― Β― π•Š \underline{\mathbb{S}} Β― start_ARG blackboard_S end_ARG being a set, 𝒒 𝒒 \mathcal{G} caligraphic_G an admissible granulation (defined below) for π•Š π•Š \mathbb{S} blackboard_S and l , u 𝑙 𝑒 l,u italic_l , italic_u being operators : π•Š Β― ⟼ π•Š Β― : absent ⟼ Β― π•Š Β― π•Š :\underline{\mathbb{S}}\longmapsto\underline{\mathbb{S}} : Β― start_ARG blackboard_S end_ARG ⟼ Β― start_ARG blackboard_S end_ARG satisfying the following ( π•Š Β― Β― π•Š \underline{\mathbb{S}} Β― start_ARG blackboard_S end_ARG is replaced with π•Š π•Š \mathbb{S} blackboard_S if clear from the context. ∨ \vee ∨ and ∧ \wedge ∧ are idempotent partial operations.):

( βˆ€ a , b ) ⁒ a ∨ b = w b ∨ a ; ( βˆ€ a , b ) ⁒ a ∧ b = w b ∧ a formulae-sequence superscript 𝑀 for-all π‘Ž 𝑏 π‘Ž 𝑏 𝑏 π‘Ž superscript 𝑀 for-all π‘Ž 𝑏 π‘Ž 𝑏 𝑏 π‘Ž \displaystyle(\forall a,b)a\vee b\stackrel{{\scriptstyle w}}{{=}}b\vee a\;;\;(% \forall a,b)a\wedge b\stackrel{{\scriptstyle w}}{{=}}b\wedge a ( βˆ€ italic_a , italic_b ) italic_a ∨ italic_b start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP italic_b ∨ italic_a ; ( βˆ€ italic_a , italic_b ) italic_a ∧ italic_b start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP italic_b ∧ italic_a
( βˆ€ a , b ) ⁒ ( a ∨ b ) ∧ a = w a ; ( βˆ€ a , b ) ⁒ ( a ∧ b ) ∨ a = w a formulae-sequence superscript 𝑀 for-all π‘Ž 𝑏 π‘Ž 𝑏 π‘Ž π‘Ž superscript 𝑀 for-all π‘Ž 𝑏 π‘Ž 𝑏 π‘Ž π‘Ž \displaystyle(\forall a,b)(a\vee b)\wedge a\stackrel{{\scriptstyle w}}{{=}}a\;% ;\;(\forall a,b)(a\wedge b)\vee a\stackrel{{\scriptstyle w}}{{=}}a ( βˆ€ italic_a , italic_b ) ( italic_a ∨ italic_b ) ∧ italic_a start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP italic_a ; ( βˆ€ italic_a , italic_b ) ( italic_a ∧ italic_b ) ∨ italic_a start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP italic_a
( βˆ€ a , b , c ) ⁒ ( a ∧ b ) ∨ c = w ( a ∨ c ) ∧ ( a ∨ c ) superscript 𝑀 for-all π‘Ž 𝑏 𝑐 π‘Ž 𝑏 𝑐 π‘Ž 𝑐 π‘Ž 𝑐 \displaystyle(\forall a,b,c)(a\wedge b)\vee c\stackrel{{\scriptstyle w}}{{=}}(% a\vee c)\wedge(a\vee c) ( βˆ€ italic_a , italic_b , italic_c ) ( italic_a ∧ italic_b ) ∨ italic_c start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP ( italic_a ∨ italic_c ) ∧ ( italic_a ∨ italic_c )
( βˆ€ a , b , c ) ⁒ ( a ∨ b ) ∧ c = w ( a ∧ c ) ∨ ( a ∧ c ) superscript 𝑀 for-all π‘Ž 𝑏 𝑐 π‘Ž 𝑏 𝑐 π‘Ž 𝑐 π‘Ž 𝑐 \displaystyle(\forall a,b,c)(a\vee b)\wedge c\stackrel{{\scriptstyle w}}{{=}}(% a\wedge c)\vee(a\wedge c) ( βˆ€ italic_a , italic_b , italic_c ) ( italic_a ∨ italic_b ) ∧ italic_c start_RELOP SUPERSCRIPTOP start_ARG = end_ARG start_ARG italic_w end_ARG end_RELOP ( italic_a ∧ italic_c ) ∨ ( italic_a ∧ italic_c )
( βˆ€ a , b ) ( a ≀ b ↔ a ∨ b = b & a ∧ b = a ) fragments fragments ( for-all a , b ) fragments ( a b ↔ a b b a b a ) \displaystyle(\forall a,b)(a\leq b\leftrightarrow a\vee b=b\,\&a\wedge b=a) ( βˆ€ italic_a , italic_b ) ( italic_a ≀ italic_b ↔ italic_a ∨ italic_b = italic_b & italic_a ∧ italic_b = italic_a )
( βˆ€ a ∈ π•Š ) 𝐏 a l a & a l ⁒ l = a l & 𝐏 a u a u ⁒ u fragments fragments ( for-all a S ) P superscript π‘Ž 𝑙 a superscript π‘Ž 𝑙 𝑙 superscript π‘Ž 𝑙 P superscript π‘Ž 𝑒 superscript π‘Ž 𝑒 𝑒 \displaystyle(\forall a\in\mathbb{S})\,\mathbf{P}a^{l}a\,\&\,a^{ll}\,=\,a^{l}% \,\&\,\mathbf{P}a^{u}a^{uu} ( βˆ€ italic_a ∈ blackboard_S ) bold_P italic_a start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT italic_a & italic_a start_POSTSUPERSCRIPT italic_l italic_l end_POSTSUPERSCRIPT = italic_a start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT & bold_P italic_a start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT italic_a start_POSTSUPERSCRIPT italic_u italic_u end_POSTSUPERSCRIPT
( βˆ€ a , b ∈ π•Š ) ( 𝐏 a b ⟢ 𝐏 a l b l & 𝐏 a u b u ) fragments fragments ( for-all a , b S ) fragments ( P a b ⟢ P superscript π‘Ž 𝑙 superscript 𝑏 𝑙 P superscript π‘Ž 𝑒 superscript 𝑏 𝑒 ) \displaystyle(\forall a,b\in\mathbb{S})(\mathbf{P}ab\longrightarrow\mathbf{P}a% ^{l}b^{l}\,\&\,\mathbf{P}a^{u}b^{u}) ( βˆ€ italic_a , italic_b ∈ blackboard_S ) ( bold_P italic_a italic_b ⟢ bold_P italic_a start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT italic_b start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT & bold_P italic_a start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT italic_b start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT )
βŠ₯ l = βŠ₯ & βŠ₯ u = βŠ₯ & 𝐏 ⊀ l ⊀ & 𝐏 ⊀ u ⊀ fragments superscript bottom 𝑙 bottom superscript bottom 𝑒 bottom P superscript top 𝑙 top P superscript top 𝑒 top \displaystyle\bot^{l}\,=\,\bot\,\&\,\bot^{u}\,=\,\bot\,\&\,\mathbf{P}\top^{l}% \top\,\&\,\mathbf{P}\top^{u}\top βŠ₯ start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT = βŠ₯ & βŠ₯ start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT = βŠ₯ & bold_P ⊀ start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT ⊀ & bold_P ⊀ start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT ⊀
( βˆ€ a ∈ π•Š ) 𝐏 βŠ₯ a & 𝐏 a ⊀ fragments fragments ( for-all a S ) P bottom a P a top \displaystyle(\forall a\in\mathbb{S})\,\mathbf{P}\bot a\,\&\,\mathbf{P}a\top ( βˆ€ italic_a ∈ blackboard_S ) bold_P βŠ₯ italic_a & bold_P italic_a ⊀

Let β„™ β„™ \mathbb{P} blackboard_P stand for proper parthood, defined via β„™ ⁒ a ⁒ b β„™ π‘Ž 𝑏 \mathbb{P}ab blackboard_P italic_a italic_b if and only if 𝐏 ⁒ a ⁒ b & Β¬ ⁒ 𝐏 ⁒ b ⁒ a 𝐏 π‘Ž 𝑏 𝐏 𝑏 π‘Ž \mathbf{P}ab\,\&\,\neg\mathbf{P}ba bold_P italic_a italic_b & Β¬ bold_P italic_b italic_a ) and let t 𝑑 t italic_t be a term operation formed from the weak lattice operations. A granulation is said to be admissible if the following three conditions hold:

( βˆ€ x βˆƒ x 1 , … x r ∈ 𝒒 ) t ( x 1 , x 2 , … x r ) = x l fragments fragments ( for-all x subscript π‘₯ 1 , … subscript π‘₯ π‘Ÿ G ) t fragments ( subscript π‘₯ 1 , subscript π‘₯ 2 , … subscript π‘₯ π‘Ÿ ) superscript π‘₯ 𝑙 \displaystyle(\forall x\exists x_{1},\ldots x_{r}\in\mathcal{G})\,t(x_{1},\,x_% {2},\ldots\,x_{r})=x^{l} ( βˆ€ italic_x βˆƒ italic_x start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , … italic_x start_POSTSUBSCRIPT italic_r end_POSTSUBSCRIPT ∈ caligraphic_G ) italic_t ( italic_x start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , italic_x start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , … italic_x start_POSTSUBSCRIPT italic_r end_POSTSUBSCRIPT ) = italic_x start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT
and ( βˆ€ x ) ( βˆƒ x 1 , … x r ∈ 𝒒 ) t ( x 1 , x 2 , … x r ) = x u , fragments and fragments ( for-all x ) fragments ( subscript π‘₯ 1 , … subscript π‘₯ π‘Ÿ G ) t fragments ( subscript π‘₯ 1 , subscript π‘₯ 2 , … subscript π‘₯ π‘Ÿ ) superscript π‘₯ 𝑒 , \displaystyle\mathrm{and}\>(\forall x)\,(\exists x_{1},\,\ldots\,x_{r}\in% \mathcal{G})\,t(x_{1},\,x_{2},\ldots\,x_{r})=x^{u}, roman_and ( βˆ€ italic_x ) ( βˆƒ italic_x start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , … italic_x start_POSTSUBSCRIPT italic_r end_POSTSUBSCRIPT ∈ caligraphic_G ) italic_t ( italic_x start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , italic_x start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , … italic_x start_POSTSUBSCRIPT italic_r end_POSTSUBSCRIPT ) = italic_x start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT , (Weak RA, WRA)
( βˆ€ y ∈ 𝒒 ) ( βˆ€ x ∈ β„˜ ( S Β― ) ) ( 𝐏 y x ⟢ 𝐏 y x l ) , fragments fragments ( for-all y G ) fragments ( for-all x β„˜ fragments ( Β― 𝑆 ) ) fragments ( P y x ⟢ P y superscript π‘₯ 𝑙 ) , \displaystyle{(\forall y\in\mathcal{G})(\forall{x\in\wp(\underline{S})})\,(% \mathbf{P}yx\,\longrightarrow\,\mathbf{P}yx^{l}),} ( βˆ€ italic_y ∈ caligraphic_G ) ( βˆ€ italic_x ∈ β„˜ ( Β― start_ARG italic_S end_ARG ) ) ( bold_P italic_y italic_x ⟢ bold_P italic_y italic_x start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT ) , (Lower Stability, LS)
( βˆ€ x , y ∈ 𝒒 ) ( βˆƒ z ∈ β„˜ ( S Β― ) ) β„™ x z , & β„™ y z & z l = z u = z , fragments fragments ( for-all x , y G ) fragments ( z β„˜ fragments ( Β― 𝑆 ) ) P x z , P y z superscript 𝑧 𝑙 superscript 𝑧 𝑒 z , \displaystyle{(\forall x,\,y\in\mathcal{G})(\exists z\in\wp(\underline{S}))\,% \mathbb{P}xz,\,\&\,\mathbb{P}yz\,\&\,z^{l}\,=\,z^{u}\,=\,z,} ( βˆ€ italic_x , italic_y ∈ caligraphic_G ) ( βˆƒ italic_z ∈ β„˜ ( Β― start_ARG italic_S end_ARG ) ) blackboard_P italic_x italic_z , & blackboard_P italic_y italic_z & italic_z start_POSTSUPERSCRIPT italic_l end_POSTSUPERSCRIPT = italic_z start_POSTSUPERSCRIPT italic_u end_POSTSUPERSCRIPT = italic_z , (Full Underlap, FU)

Definition 2.1 (Cayley-Dickson construction [ 6 ] , [ 1 ] ) .

Consider the vector space of the direct sum of two copies of an algebra with conjugation: π’œ 2 = π’œ βŠ• π’œ superscript π’œ 2 direct-sum π’œ π’œ \mathcal{A}^{2}=\mathcal{A}\oplus\mathcal{A} caligraphic_A start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT = caligraphic_A βŠ• caligraphic_A . A multiplication on π’œ 2 superscript π’œ 2 \mathcal{A}^{2} caligraphic_A start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT is defined as

( a , b ) ⁒ ( u , v ) = ( a ⁒ u - v Β― ⁒ b , b ⁒ u Β― + v ⁒ a ) . π‘Ž 𝑏 𝑒 𝑣 π‘Ž 𝑒 Β― 𝑣 𝑏 𝑏 Β― 𝑒 𝑣 π‘Ž (a,b)(u,v)=(au-\bar{v}b,b\bar{u}+va). ( italic_a , italic_b ) ( italic_u , italic_v ) = ( italic_a italic_u - Β― start_ARG italic_v end_ARG italic_b , italic_b Β― start_ARG italic_u end_ARG + italic_v italic_a ) .

It is easy to check, that relative to this multiplication the vector space π’œ 2 superscript π’œ 2 \mathcal{A}^{2} caligraphic_A start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT is an algebra of dimension 2 β‹… dim ⁒ ( π’œ ) β‹… 2 dim π’œ 2\cdot\mathrm{dim}(\mathcal{A}) 2 β‹… roman_dim ( caligraphic_A ) . This is called the doubling of the algebra π’œ π’œ \mathcal{A} caligraphic_A .


Definition 2.1 .

[ 6 ] Let A 𝐴 A italic_A be an associative algebra. A bilinear map Ξ΄ : A Γ— A β†’ A normal-: 𝛿 normal-β†’ 𝐴 𝐴 𝐴 \delta:A\times A\rightarrow A italic_Ξ΄ : italic_A Γ— italic_A β†’ italic_A is called a biderivation if for all x , y , z ∈ A π‘₯ 𝑦 𝑧 𝐴 x,y,z\in A italic_x , italic_y , italic_z ∈ italic_A ,

  1. (i)

    Ξ΄ ⁒ ( x ⁒ y , z ) = Ξ΄ ⁒ ( x , z ) ⁒ y + x ⁒ Ξ΄ ⁒ ( y , z ) 𝛿 π‘₯ 𝑦 𝑧 𝛿 π‘₯ 𝑧 𝑦 π‘₯ 𝛿 𝑦 𝑧 \delta(xy,z)=\delta(x,z)y+x\delta(y,z) italic_Ξ΄ ( italic_x italic_y , italic_z ) = italic_Ξ΄ ( italic_x , italic_z ) italic_y + italic_x italic_Ξ΄ ( italic_y , italic_z ) ,

  2. (ii)

    Ξ΄ ⁒ ( x , y ⁒ z ) = Ξ΄ ⁒ ( x , y ) ⁒ z + y ⁒ Ξ΄ ⁒ ( x , z ) 𝛿 π‘₯ 𝑦 𝑧 𝛿 π‘₯ 𝑦 𝑧 𝑦 𝛿 π‘₯ 𝑧 \delta(x,yz)=\delta(x,y)z+y\delta(x,z) italic_Ξ΄ ( italic_x , italic_y italic_z ) = italic_Ξ΄ ( italic_x , italic_y ) italic_z + italic_y italic_Ξ΄ ( italic_x , italic_z ) .


Definition 2 (Latent Discrimination) .

Classifier h β„Ž h italic_h exhibits no latent discrimination if for every pair ( 𝐱 1 , 𝐱 2 ) ∈ 𝒳 2 superscript 𝐱 1 superscript 𝐱 2 superscript 𝒳 2 (\mathbf{x}^{1},\mathbf{x}^{2})\in\mathcal{X}^{2} ( bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT , bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) ∈ caligraphic_X start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT such that 𝐱 0 1 = 𝐱 0 2 subscript superscript 𝐱 1 0 subscript superscript 𝐱 2 0 \mathbf{x}^{1}_{0}=\mathbf{x}^{2}_{0} bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT = bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT (i.e., pairs with similar sensitive features) we have : normal-: : :

h * ⁒ ( 𝐱 1 ) = h * ⁒ ( 𝐱 2 ) superscript β„Ž superscript 𝐱 1 superscript β„Ž superscript 𝐱 2 \displaystyle h^{*}(\mathbf{x}^{1})=h^{*}(\mathbf{x}^{2}) italic_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ) = italic_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) β‡’ h ⁒ ( 𝐱 1 ) = h ⁒ ( 𝐱 2 ) , a ⁒ n ⁒ d formulae-sequence β‡’ absent β„Ž superscript 𝐱 1 β„Ž superscript 𝐱 2 π‘Ž 𝑛 𝑑 \displaystyle\Rightarrow h(\mathbf{x}^{1})=h(\mathbf{x}^{2}),\ and β‡’ italic_h ( bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ) = italic_h ( bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) , italic_a italic_n italic_d (1)
h * ⁒ ( 𝐱 1 ) > h * ⁒ ( 𝐱 2 ) superscript β„Ž superscript 𝐱 1 superscript β„Ž superscript 𝐱 2 \displaystyle h^{*}(\mathbf{x}^{1})>h^{*}(\mathbf{x}^{2}) italic_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ) > italic_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) β‡’ h ⁒ ( 𝐱 1 ) β‰₯ h ⁒ ( 𝐱 2 ) . β‡’ absent β„Ž superscript 𝐱 1 β„Ž superscript 𝐱 2 \displaystyle\Rightarrow h(\mathbf{x}^{1})\geq h(\mathbf{x}^{2}). β‡’ italic_h ( bold_x start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ) β‰₯ italic_h ( bold_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ) . (2)

Definition 1 .

A Hilbert algebra is an algebra H = ( H , β†’ , 1 ) 𝐻 𝐻 β†’ 1 H=(H,\rightarrow,1) italic_H = ( italic_H , β†’ , 1 ) of type ( 2 , 0 ) 2 0 (2,0) ( 2 , 0 ) which satisfies the following conditions for every a , b , c ∈ H π‘Ž 𝑏 𝑐 𝐻 a,b,c\in H italic_a , italic_b , italic_c ∈ italic_H :

  1. 1)

    a β†’ ( b β†’ a ) = 1 fragments a β†’ fragments ( b β†’ a ) 1 a\rightarrow(b\rightarrow a)=1 italic_a β†’ ( italic_b β†’ italic_a ) = 1 ,

  2. 2)

    ( a β†’ ( b β†’ c ) ) β†’ ( ( a β†’ b ) β†’ ( a β†’ c ) ) = 1 fragments fragments ( a β†’ fragments ( b β†’ c ) ) β†’ fragments ( fragments ( a β†’ b ) β†’ fragments ( a β†’ c ) ) 1 (a\rightarrow(b\rightarrow c))\rightarrow((a\rightarrow b)\rightarrow(a% \rightarrow c))=1 ( italic_a β†’ ( italic_b β†’ italic_c ) ) β†’ ( ( italic_a β†’ italic_b ) β†’ ( italic_a β†’ italic_c ) ) = 1 ,

  3. 3)

    if a β†’ b = b β†’ a = 1 β†’ π‘Ž 𝑏 𝑏 β†’ π‘Ž 1 a\rightarrow b=b\rightarrow a=1 italic_a β†’ italic_b = italic_b β†’ italic_a = 1 then a = b π‘Ž 𝑏 a=b italic_a = italic_b .