Definition 4.2 .

Assume that φ ( x , ξ ) 𝜑 𝑥 𝜉 \varphi(x,\xi) italic_φ ( italic_x , italic_ξ ) is a measurable-convex integrand with each φ ( x , ξ ) [ 0 , + ) 𝜑 𝑥 𝜉 0 \varphi(x,\xi)\in[0,+\infty) italic_φ ( italic_x , italic_ξ ) ∈ [ 0 , + ∞ ) and φ ( x , 0 ) = 0 𝜑 𝑥 0 0 \varphi(x,0)=0 italic_φ ( italic_x , 0 ) = 0 . For each x G 𝑥 𝐺 x\in G italic_x ∈ italic_G , denote the subgradient of φ ( x , ) 𝜑 𝑥 normal-⋅ \varphi(x,\cdot) italic_φ ( italic_x , ⋅ ) by

(26) β ¯ ( x , ) = φ ( x , ) . ¯ 𝛽 𝑥 𝜑 𝑥 \displaystyle\bar{\beta}(x,\cdot)=\partial\varphi(x,\cdot). ¯ start_ARG italic_β end_ARG ( italic_x , ⋅ ) = ∂ italic_φ ( italic_x , ⋅ ) .

Definition 1 .

Let {\cal E} caligraphic_E be the variety of Moufang loops with the following identities:

x 4 = 1 , [ x , y ] 2 = 1 , ( x , y , z ) 2 = 1 , formulae-sequence superscript 𝑥 4 1 formulae-sequence superscript 𝑥 𝑦 2 1 superscript 𝑥 𝑦 𝑧 2 1 \displaystyle x^{4}=1,\,\left[x,y\right]^{2}=1,\,(x,y,z)^{2}=1, italic_x start_POSTSUPERSCRIPT 4 end_POSTSUPERSCRIPT = 1 , [ italic_x , italic_y ] start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT = 1 , ( italic_x , italic_y , italic_z ) start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT = 1 ,
[ x 2 , y ] = 1 , [ [ x , y ] , t ] = 1 , [ ( x , y , z ) , t ] = 1 , formulae-sequence superscript 𝑥 2 𝑦 1 formulae-sequence 𝑥 𝑦 𝑡 1 𝑥 𝑦 𝑧 𝑡 1 \displaystyle\left[x^{2},y\right]=1,\,\left[\left[x,y\right],t\right]=1,\,% \left[(x,y,z),t\right]=1, [ italic_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT , italic_y ] = 1 , [ [ italic_x , italic_y ] , italic_t ] = 1 , [ ( italic_x , italic_y , italic_z ) , italic_t ] = 1 ,
( x 2 , y , z ) = 1 , ( [ x , y ] , z , t ) = 1 , ( ( x , y , z ) , t , s ) = 1 . formulae-sequence superscript 𝑥 2 𝑦 𝑧 1 formulae-sequence 𝑥 𝑦 𝑧 𝑡 1 𝑥 𝑦 𝑧 𝑡 𝑠 1 \displaystyle(x^{2},y,z)=1,\,(\left[x,y\right],z,t)=1,\;\;((x,y,z),t,s)=1. ( italic_x start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT , italic_y , italic_z ) = 1 , ( [ italic_x , italic_y ] , italic_z , italic_t ) = 1 , ( ( italic_x , italic_y , italic_z ) , italic_t , italic_s ) = 1 . (4)

Definition 3.3 .

Let D a := S p { ϕ a V , ϕ a H } assign superscript subscript 𝐷 𝑎 bottom 𝑆 𝑝 superscript italic-ϕ 𝑎 𝑉 superscript italic-ϕ 𝑎 𝐻 D_{a}^{\bot}:=Sp\{\phi^{aV},\phi^{aH}\} italic_D start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ⊥ end_POSTSUPERSCRIPT := italic_S italic_p { italic_ϕ start_POSTSUPERSCRIPT italic_a italic_V end_POSTSUPERSCRIPT , italic_ϕ start_POSTSUPERSCRIPT italic_a italic_H end_POSTSUPERSCRIPT } be an eigenform-distribution of Φ double-struck-Φ \mathbb{\Phi} blackboard_Φ . A 1-form α D a 𝛼 superscript subscript 𝐷 𝑎 bottom \alpha\in D_{a}^{\bot} italic_α ∈ italic_D start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ⊥ end_POSTSUPERSCRIPT is said to be an integrable direction in D a superscript subscript 𝐷 𝑎 bottom D_{a}^{\bot} italic_D start_POSTSUBSCRIPT italic_a end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ⊥ end_POSTSUPERSCRIPT if

d α = κ α , 𝑑 𝛼 𝜅 𝛼 \displaystyle d\alpha=\kappa\wedge\alpha, italic_d italic_α = italic_κ ∧ italic_α , (18)

for some 1-form κ . 𝜅 \kappa. italic_κ .


Definition 1.1 .

We define the algebraic intersection number α β normal-⋅ 𝛼 𝛽 \alpha\cdot\beta\in\mathbb{Z} italic_α ⋅ italic_β ∈ blackboard_Z by

[ δ * β ] = ( α β ) [ u ] , delimited-[] 𝛿 𝛽 𝛼 𝛽 delimited-[] 𝑢 [\delta*\beta]=(\alpha\cdot\beta)[u], [ italic_δ * italic_β ] = ( italic_α ⋅ italic_β ) [ italic_u ] ,

where u 𝑢 u italic_u is an embedded closed loop in S 2 A , superscript 𝑆 2 𝐴 S^{2}\setminus A, italic_S start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ∖ italic_A , positively oriented with respect to x 1 , subscript 𝑥 1 x_{1}, italic_x start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , and hence [ u ] delimited-[] 𝑢 [u] [ italic_u ] is a generator of H 1 ( S 2 A ) subscript 𝐻 1 superscript 𝑆 2 𝐴 H_{1}(S^{2}\setminus A) italic_H start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ( italic_S start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ∖ italic_A ) .


Definition 2.4 .

Let G 𝐺 G italic_G be an abelian group. A map ε : G × G 𝐊 * normal-: 𝜀 normal-→ 𝐺 𝐺 superscript 𝐊 \varepsilon:G\times G\rightarrow{\bf K^{*}} italic_ε : italic_G × italic_G → bold_K start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT is called a skew-symmetric bicharacter on G 𝐺 G italic_G if the following identities hold: for all a , b , c G 𝑎 𝑏 𝑐 𝐺 a,b,c\in G italic_a , italic_b , italic_c ∈ italic_G ,

  1. (i)

    ε ( a , b ) ε ( b , a ) = 1 𝜀 𝑎 𝑏 𝜀 𝑏 𝑎 1 \varepsilon(a,b)\varepsilon(b,a)=1 italic_ε ( italic_a , italic_b ) italic_ε ( italic_b , italic_a ) = 1 ;

  2. (ii)

    ε ( a , b + c ) = ε ( a , b ) ε ( a , c ) 𝜀 𝑎 𝑏 𝑐 𝜀 𝑎 𝑏 𝜀 𝑎 𝑐 \varepsilon(a,b+c)=\varepsilon(a,b)\varepsilon(a,c) italic_ε ( italic_a , italic_b + italic_c ) = italic_ε ( italic_a , italic_b ) italic_ε ( italic_a , italic_c ) ;

  3. (iii)

    ε ( a + b , c ) = ε ( a , c ) ε ( b , c ) 𝜀 𝑎 𝑏 𝑐 𝜀 𝑎 𝑐 𝜀 𝑏 𝑐 \varepsilon(a+b,c)=\varepsilon(a,c)\varepsilon(b,c) italic_ε ( italic_a + italic_b , italic_c ) = italic_ε ( italic_a , italic_c ) italic_ε ( italic_b , italic_c ) .


Definition 3 .

The (left) groupoid representation of G 𝐺 G italic_G is the representation π 𝜋 \pi italic_π in L 2 ( , ν ) superscript 𝐿 2 𝜈 L^{2}(\mathcal{\mathcal{R}},\nu) italic_L start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ( caligraphic_R , italic_ν ) defined by

( π ( g ) f ) ( ( x , y ) ) = f ( g - 1 x , y ) . 𝜋 𝑔 𝑓 𝑥 𝑦 𝑓 superscript 𝑔 1 𝑥 𝑦 (\pi(g)f)((x,y))=f(g^{-1}x,y). ( italic_π ( italic_g ) italic_f ) ( ( italic_x , italic_y ) ) = italic_f ( italic_g start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT italic_x , italic_y ) .

Definition 3.1.2 .

The Lie algebra 𝔤 𝔯 𝔱 1 𝔤 𝔯 subscript 𝔱 1 \mathfrak{grt}_{1} fraktur_g fraktur_r fraktur_t start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT is spanned by the elements ( 0 , ψ ) 𝔱 𝔡 𝔢 𝔯 2 0 𝜓 𝔱 𝔡 𝔢 subscript 𝔯 2 (0,\psi)\in\mathfrak{tder}_{2} ( 0 , italic_ψ ) ∈ fraktur_t fraktur_d fraktur_e fraktur_r start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , that satisfy the following relations:

ψ ( x , y ) = - ψ ( y , x ) , 𝜓 𝑥 𝑦 𝜓 𝑦 𝑥 \psi(x,y)=-\psi(y,x), italic_ψ ( italic_x , italic_y ) = - italic_ψ ( italic_y , italic_x ) , (3.1)
ψ ( x , y ) + ψ ( y , z ) + ψ ( z , x ) = 0 for x + y + z = 0 , formulae-sequence 𝜓 𝑥 𝑦 𝜓 𝑦 𝑧 𝜓 𝑧 𝑥 0 for 𝑥 𝑦 𝑧 0 \psi(x,y)+\psi(y,z)+\psi(z,x)=0\;\;\;\;{\rm for}\;\;\;\;x+y+z=0, italic_ψ ( italic_x , italic_y ) + italic_ψ ( italic_y , italic_z ) + italic_ψ ( italic_z , italic_x ) = 0 roman_for italic_x + italic_y + italic_z = 0 , (3.2)
ψ ( t 1 , 2 , t 2 , 34 ) + ψ ( t 12 , 3 , t 3 , 4 ) = ψ ( t 2 , 3 , t 3 , 4 ) + ψ ( t 1 , 23 , t 23 , 4 ) + ψ ( t 1 , 2 , t 2 , 3 ) , 𝜓 superscript 𝑡 1 2 superscript 𝑡 2 34 𝜓 superscript 𝑡 12 3 superscript 𝑡 3 4 𝜓 superscript 𝑡 2 3 superscript 𝑡 3 4 𝜓 superscript 𝑡 1 23 superscript 𝑡 23 4 𝜓 superscript 𝑡 1 2 superscript 𝑡 2 3 \psi(t^{1,2},t^{2,34})+\psi(t^{12,3},t^{3,4})=\psi(t^{2,3},t^{3,4})+\psi(t^{1,% 23},t^{23,4})+\psi(t^{1,2},t^{2,3}), italic_ψ ( italic_t start_POSTSUPERSCRIPT 1 , 2 end_POSTSUPERSCRIPT , italic_t start_POSTSUPERSCRIPT 2 , 34 end_POSTSUPERSCRIPT ) + italic_ψ ( italic_t start_POSTSUPERSCRIPT 12 , 3 end_POSTSUPERSCRIPT , italic_t start_POSTSUPERSCRIPT 3 , 4 end_POSTSUPERSCRIPT ) = italic_ψ ( italic_t start_POSTSUPERSCRIPT 2 , 3 end_POSTSUPERSCRIPT , italic_t start_POSTSUPERSCRIPT 3 , 4 end_POSTSUPERSCRIPT ) + italic_ψ ( italic_t start_POSTSUPERSCRIPT 1 , 23 end_POSTSUPERSCRIPT , italic_t start_POSTSUPERSCRIPT 23 , 4 end_POSTSUPERSCRIPT ) + italic_ψ ( italic_t start_POSTSUPERSCRIPT 1 , 2 end_POSTSUPERSCRIPT , italic_t start_POSTSUPERSCRIPT 2 , 3 end_POSTSUPERSCRIPT ) , (3.3)

where the last equation takes values in the Lie algebra 𝔱 𝔱 \mathfrak{t} fraktur_t , and t 1 , 23 = t 1 , 2 + t 1 , 3 superscript 𝑡 1 23 superscript 𝑡 1 2 superscript 𝑡 1 3 t^{1,23}=t^{1,2}+t^{1,3} italic_t start_POSTSUPERSCRIPT 1 , 23 end_POSTSUPERSCRIPT = italic_t start_POSTSUPERSCRIPT 1 , 2 end_POSTSUPERSCRIPT + italic_t start_POSTSUPERSCRIPT 1 , 3 end_POSTSUPERSCRIPT , etc.


Definition 3.6 .

If λ n , k * 𝜆 superscript subscript 𝑛 𝑘 \lambda\in\mathcal{L}_{n,k}^{*} italic_λ ∈ caligraphic_L start_POSTSUBSCRIPT italic_n , italic_k end_POSTSUBSCRIPT start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT , then define the weight of λ 𝜆 \lambda italic_λ by

w ( λ ) = α 𝑛𝑟𝑒𝑐 ( λ ) β 𝑟𝑒𝑐 * ( λ ) r 𝑐𝑖𝑟𝑐 ( λ ) . 𝑤 𝜆 superscript 𝛼 𝑛𝑟𝑒𝑐 𝜆 superscript 𝛽 superscript 𝑟𝑒𝑐 𝜆 superscript 𝑟 𝑐𝑖𝑟𝑐 𝜆 w(\lambda)=\alpha^{\text{nrec}(\lambda)}\beta^{\text{rec}^{*}(\lambda)}r^{% \text{circ}(\lambda)}. italic_w ( italic_λ ) = italic_α start_POSTSUPERSCRIPT nrec ( italic_λ ) end_POSTSUPERSCRIPT italic_β start_POSTSUPERSCRIPT rec start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( italic_λ ) end_POSTSUPERSCRIPT italic_r start_POSTSUPERSCRIPT circ ( italic_λ ) end_POSTSUPERSCRIPT .

Definition .

(Commutative algebra) A commutative algebra 𝒜 𝒜 \mathcal{A} caligraphic_A is a vector space equipped with an additional associative + : 𝒜 × 𝒜 𝒜 fragments : A A A +:\mathcal{A}\times\mathcal{A}\rightarrow\mathcal{A} + : caligraphic_A × caligraphic_A → caligraphic_A and commutative multiplication : 𝒜 × 𝒜 𝒜 fragments : A A A \cdot\,:\mathcal{A}\times\mathcal{A}\rightarrow\mathcal{A} ⋅ : caligraphic_A × caligraphic_A → caligraphic_A such that

x ( y + z ) = x y + x z , λ ( x y ) = ( λ x ) y formulae-sequence 𝑥 𝑦 𝑧 𝑥 𝑦 𝑥 𝑧 𝜆 𝑥 𝑦 𝜆 𝑥 𝑦 x\cdot(y+z)=x\cdot y+x\cdot z,\quad\lambda(x\cdot y)=(\lambda x)\cdot y italic_x ⋅ ( italic_y + italic_z ) = italic_x ⋅ italic_y + italic_x ⋅ italic_z , italic_λ ( italic_x ⋅ italic_y ) = ( italic_λ italic_x ) ⋅ italic_y

holds for all x , 𝑥 x, italic_x , y 𝑦 y italic_y , z 𝒜 𝑧 𝒜 z\in\mathcal{A} italic_z ∈ caligraphic_A and λ 𝜆 \lambda\in\mathbb{R} italic_λ ∈ blackboard_R . An important algebra is the space C ( 𝒳 ) 𝐶 𝒳 C(\mathcal{X}) italic_C ( caligraphic_X ) of all continuous functions f : 𝒳 : 𝑓 𝒳 f:\mathcal{X}\rightarrow\mathbb{R} italic_f : caligraphic_X → blackboard_R on the compact metric space ( 𝒳 , 𝐝 ) 𝒳 𝐝 (\mathcal{X},\mathbf{d}) ( caligraphic_X , bold_d ) endowed with the supremum norm

f := sup x 𝒳 | f ( x ) | . assign subscript norm 𝑓 subscript supremum 𝑥 𝒳 𝑓 𝑥 \|f\|_{\infty}:=\sup_{x\in\mathcal{X}}|f(x)|. ∥ italic_f ∥ start_POSTSUBSCRIPT ∞ end_POSTSUBSCRIPT := roman_sup start_POSTSUBSCRIPT italic_x ∈ caligraphic_X end_POSTSUBSCRIPT | italic_f ( italic_x ) | .

Definition 5

Let 𝒞 𝒫 ~ ( n ) ( Π ~ ) superscript normal-~ 𝒞 𝒫 𝑛 normal-~ normal-Π \tilde{\cal CP}^{(n)}(\tilde{\Pi}) ~ start_ARG caligraphic_C caligraphic_P end_ARG start_POSTSUPERSCRIPT ( italic_n ) end_POSTSUPERSCRIPT ( ~ start_ARG roman_Π end_ARG ) be a set of in-plane Bézier control points of all patches which result from degree elevation of a global regular in-plane parametrisation Π ~ normal-~ normal-Π \tilde{\Pi} ~ start_ARG roman_Π end_ARG up to degree n 𝑛 n italic_n for every patch. Since the Bézier control points of the in-plane parametrisation always coincide along the shared edges, they are unambiguously well defined.

A determining set D is a subset of 𝒞 𝒫 ~ ( n ) superscript normal-~ 𝒞 𝒫 𝑛 \tilde{\cal CP}^{(n)} ~ start_ARG caligraphic_C caligraphic_P end_ARG start_POSTSUPERSCRIPT ( italic_n ) end_POSTSUPERSCRIPT so that :

P D , Z ( P ) = 0 Ψ ¯ 0 ; formulae-sequence for-all 𝑃 𝐷 𝑍 𝑃 0 ¯ Ψ 0 \forall P\in D,\quad Z(P)=0\Rightarrow\bar{\Psi}\ \equiv 0; ∀ italic_P ∈ italic_D , italic_Z ( italic_P ) = 0 ⇒ ¯ start_ARG roman_Ψ end_ARG ≡ 0 ;

A determining set is called minimal determining set (MDS) ~ ( n ) superscript normal-~ 𝑛 \tilde{\cal B}^{(n)} ~ start_ARG caligraphic_B end_ARG start_POSTSUPERSCRIPT ( italic_n ) end_POSTSUPERSCRIPT if there is no determining which size is smaller.


Definition 1 (Screening test) .

Given problem 𝒫 ( λ , Ω , 𝐃 , 𝐲 ) 𝒫 𝜆 Ω 𝐃 𝐲 \mathcal{P}(\lambda,\Omega,\mathbf{D},\boldsymbol{\mathrm{y}}) caligraphic_P ( italic_λ , roman_Ω , bold_D , bold_y ) with solution 𝐱 ~ ~ 𝐱 \tilde{\boldsymbol{\mathrm{x}}} ~ start_ARG bold_x end_ARG , a boolean-valued function T : [ 1 K ] { 0 , 1 } : 𝑇 delimited-[] 1 𝐾 0 1 {T:[1\ldots K]\rightarrow\{0,1\}} italic_T : [ 1 … italic_K ] → { 0 , 1 } is a screening test if and only if:

i [ 1 K ] , T ( i ) = 1 𝐱 ~ ( i ) = 0 . formulae-sequence for-all 𝑖 delimited-[] 1 𝐾 𝑇 𝑖 1 ~ 𝐱 𝑖 0 \displaystyle\forall i\in[1\ldots K],T(i)=1\Rightarrow\mathnormal{\tilde{% \boldsymbol{\mathrm{x}}}}(i)=0. ∀ italic_i ∈ [ 1 … italic_K ] , italic_T ( italic_i ) = 1 ⇒ ~ start_ARG bold_x end_ARG ( italic_i ) = 0 . (2)

Definition 2.1 .

An algebra ( L , [ , ] ) 𝐿 normal-⋅ normal-⋅ (L,[\cdot,\cdot]) ( italic_L , [ ⋅ , ⋅ ] ) over a field F 𝐹 F italic_F is called a Leibniz algebra if it is defined by the identity

[ x , [ y , z ] ] = [ [ x , y ] , z ] - [ [ x , z ] , y ] . 𝑥 𝑦 𝑧 𝑥 𝑦 𝑧 𝑥 𝑧 𝑦 [x,[y,z]]=[[x,y],z]-[[x,z],y]. [ italic_x , [ italic_y , italic_z ] ] = [ [ italic_x , italic_y ] , italic_z ] - [ [ italic_x , italic_z ] , italic_y ] .
Definition 2.5 .

A linear transformation d 𝑑 d italic_d of a Leibniz algebra L 𝐿 L italic_L is said to be a derivation if for any x , y L 𝑥 𝑦 𝐿 x,y\in L italic_x , italic_y ∈ italic_L one has

d ( [ x , y ] ) = [ d ( x ) , y ] + [ x , d ( y ) ] . 𝑑 𝑥 𝑦 𝑑 𝑥 𝑦 𝑥 𝑑 𝑦 d([x,y])=[d(x),y]+[x,d(y)]. italic_d ( [ italic_x , italic_y ] ) = [ italic_d ( italic_x ) , italic_y ] + [ italic_x , italic_d ( italic_y ) ] .

Definition 6.1 .

Let s 𝑠 s italic_s be an exponent over the finite field L 𝐿 L italic_L . We say that s 𝑠 s italic_s is a nice exponent over L 𝐿 L italic_L if the number N ( 1 , v ) 𝑁 1 𝑣 N(1,v) italic_N ( 1 , italic_v ) of solutions in L 2 superscript 𝐿 2 L^{2} italic_L start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT of

x + y = 1 , 𝑥 𝑦 1 \displaystyle x+y=1, italic_x + italic_y = 1 ,
x s + y s = v , superscript 𝑥 𝑠 superscript 𝑦 𝑠 𝑣 \displaystyle x^{s}+y^{s}=v, italic_x start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT + italic_y start_POSTSUPERSCRIPT italic_s end_POSTSUPERSCRIPT = italic_v ,

takes at most 3 3 3 3 values as v 𝑣 v italic_v runs through L 𝐿 L italic_L .


Definition 4.1

The solution z ( t , x ) = ( u , v , w ) 𝑧 𝑡 𝑥 𝑢 𝑣 𝑤 z(t,x)=(u,v,w) italic_z ( italic_t , italic_x ) = ( italic_u , italic_v , italic_w ) to system (1.1) is x 𝑥 x italic_x -symmetric if there exists a function b ( t ) 𝒞 1 ( + ) 𝑏 𝑡 superscript 𝒞 1 superscript b(t)\in\mathcal{C}^{1}(\mathbb{R^{+}}) italic_b ( italic_t ) ∈ caligraphic_C start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ( blackboard_R start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT ) such that

z ( t , x ) = z ( t , 2 b ( t ) - x ) , t [ 0 , ) , formulae-sequence 𝑧 𝑡 𝑥 𝑧 𝑡 2 𝑏 𝑡 𝑥 for-all 𝑡 0 z(t,x)=z(t,2b(t)-x),\qquad\forall t\in[0,\infty), italic_z ( italic_t , italic_x ) = italic_z ( italic_t , 2 italic_b ( italic_t ) - italic_x ) , ∀ italic_t ∈ [ 0 , ∞ ) ,

for almost every x 𝑥 x\in\mathbb{R} italic_x ∈ blackboard_R , then the function b ( t ) 𝑏 𝑡 b(t) italic_b ( italic_t ) is called the symmetric axis of z ( t , x ) 𝑧 𝑡 𝑥 z(t,x) italic_z ( italic_t , italic_x ) .


Definition 3.2 .

The dual of a pair of dihedral structures ( δ , δ ) 𝛿 superscript 𝛿 (\delta,\delta^{\prime}) ( italic_δ , italic_δ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) is

( δ , δ ) = ( δ , δ ) . superscript 𝛿 superscript 𝛿 superscript 𝛿 𝛿 (\delta,\delta^{\prime})^{\vee}=(\delta^{\prime},\delta)\ . ( italic_δ , italic_δ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) start_POSTSUPERSCRIPT ∨ end_POSTSUPERSCRIPT = ( italic_δ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT , italic_δ ) .

It is well-defined on configurations, and defines an involution : 𝒞 S 𝒞 S fragments : subscript 𝒞 𝑆 subscript 𝒞 𝑆 \vee:\mathcal{C}_{S}\rightarrow\mathcal{C}_{S} ∨ : caligraphic_C start_POSTSUBSCRIPT italic_S end_POSTSUBSCRIPT → caligraphic_C start_POSTSUBSCRIPT italic_S end_POSTSUBSCRIPT .


Definition 2.26 .

Let m 2 𝑚 2 m\geq 2 italic_m ≥ 2 be an integer and ε > 0 𝜀 0 \varepsilon>0 italic_ε > 0 . We say a germ of continuous map u : 𝒪 ( S , x ) Q normal-: 𝑢 normal-→ 𝒪 𝑆 𝑥 𝑄 u:{\mathcal{O}}(S,x)\rightarrow Q italic_u : caligraphic_O ( italic_S , italic_x ) → italic_Q is of class ( m , ε ) 𝑚 𝜀 (m,\varepsilon) ( italic_m , italic_ε ) at the point x 𝑥 x italic_x if for a smooth chart ϕ : U ( u ( 0 ) ) 2 n normal-: italic-ϕ normal-→ 𝑈 𝑢 0 superscript 2 𝑛 \phi:U(u(0))\rightarrow{\mathbb{R}}^{2n} italic_ϕ : italic_U ( italic_u ( 0 ) ) → blackboard_R start_POSTSUPERSCRIPT 2 italic_n end_POSTSUPERSCRIPT mapping u ( 0 ) 𝑢 0 u(0) italic_u ( 0 ) to 0 0 and holomorphic polar coordinates σ : [ 0 , ) × S 1 S { x } normal-: 𝜎 normal-→ 0 superscript 𝑆 1 𝑆 𝑥 \sigma:[0,\infty)\times S^{1}\rightarrow S\setminus\{x\} italic_σ : [ 0 , ∞ ) × italic_S start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT → italic_S ∖ { italic_x } around x 𝑥 x italic_x , the map

v ( s , t ) = ϕ u σ ( s , t ) , 𝑣 𝑠 𝑡 italic-ϕ 𝑢 𝜎 𝑠 𝑡 v(s,t)=\phi\circ u\circ\sigma(s,t), italic_v ( italic_s , italic_t ) = italic_ϕ ∘ italic_u ∘ italic_σ ( italic_s , italic_t ) ,

defined for s 𝑠 s italic_s large, has partial derivatives up to order m 𝑚 m italic_m , which weighted by e ε s superscript 𝑒 𝜀 𝑠 e^{\varepsilon s} italic_e start_POSTSUPERSCRIPT italic_ε italic_s end_POSTSUPERSCRIPT belong to L 2 ( [ s 0 , ) × S 1 , 2 n ) superscript 𝐿 2 subscript 𝑠 0 superscript 𝑆 1 superscript 2 𝑛 L^{2}([s_{0},\infty)\times S^{1},{\mathbb{R}}^{2n}) italic_L start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ( [ italic_s start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT , ∞ ) × italic_S start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT , blackboard_R start_POSTSUPERSCRIPT 2 italic_n end_POSTSUPERSCRIPT ) if s 0 subscript 𝑠 0 s_{0} italic_s start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT is sufficiently large. We say the germ is of class m 𝑚 m italic_m around a point z S 𝑧 𝑆 z\in S italic_z ∈ italic_S provided u 𝑢 u italic_u is of class H l o c m subscript superscript 𝐻 𝑚 𝑙 𝑜 𝑐 H^{m}_{loc} italic_H start_POSTSUPERSCRIPT italic_m end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_l italic_o italic_c end_POSTSUBSCRIPT near z 𝑧 z italic_z .


Definition 3.6 (Offspring distribution) .

Let r 1 𝑟 1 r\geq 1 italic_r ≥ 1 and 𝝃 = ( ξ ( 1 ) , , ξ ( r ) ) 𝝃 superscript 𝜉 1 superscript 𝜉 𝑟 \bm{\xi}=\left(\xi^{\left(1\right)},\ldots,\xi^{\left(r\right)}\right) bold_italic_ξ = ( italic_ξ start_POSTSUPERSCRIPT ( 1 ) end_POSTSUPERSCRIPT , … , italic_ξ start_POSTSUPERSCRIPT ( italic_r ) end_POSTSUPERSCRIPT ) be a family of probabilities on the σ 𝜎 \sigma italic_σ -algebra σ ( W r ) 𝜎 subscript 𝑊 𝑟 \sigma\left(W_{r}\right) italic_σ ( italic_W start_POSTSUBSCRIPT italic_r end_POSTSUBSCRIPT ) . We say that the family of probabilities 𝝁 𝝁 \bm{\mu} bold_italic_μ on the σ 𝜎 \sigma italic_σ -algebra σ ( r ) 𝜎 superscript 𝑟 \sigma\left(\mathbb{N}^{r}\right) italic_σ ( blackboard_N start_POSTSUPERSCRIPT italic_r end_POSTSUPERSCRIPT ) is an offspring distribution, where p is the counter map defined in Definition 3.5 and

𝝁 ( i ) = ξ ( i ) 𝒑 - 1 , i = 1 , , r . formulae-sequence superscript 𝝁 𝑖 superscript 𝜉 𝑖 superscript 𝒑 1 for-all 𝑖 1 𝑟 \bm{\mu}^{\left(i\right)}=\xi^{\left(i\right)}\circ\textbf{{p}}^{-1},\ \ % \forall i=1,\ldots,r. bold_italic_μ start_POSTSUPERSCRIPT ( italic_i ) end_POSTSUPERSCRIPT = italic_ξ start_POSTSUPERSCRIPT ( italic_i ) end_POSTSUPERSCRIPT ∘ p start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT , ∀ italic_i = 1 , … , italic_r .

Definition 4.2 .

Let G 𝐺 G italic_G be a group acting on a space X 𝑋 X italic_X and let f 𝑓 f italic_f be a global function on X 𝑋 X italic_X . We say that f 𝑓 f italic_f is semi-invariant with respect to a character χ 𝜒 \chi italic_χ if, for any g G 𝑔 𝐺 g\in G italic_g ∈ italic_G ,

f ( g x ) = χ ( g ) f ( x ) . 𝑓 𝑔 𝑥 𝜒 𝑔 𝑓 𝑥 f(g\cdot x)=\chi(g)f(x). italic_f ( italic_g ⋅ italic_x ) = italic_χ ( italic_g ) italic_f ( italic_x ) .

Equivalently, this means that f 𝑓 f italic_f is a section of the equivariant line bundle 𝒪 ( χ ) 𝒪 𝜒 \operatorname{\mathcal{O}}(\chi) caligraphic_O ( italic_χ ) on the global quotient stack [ X / G ] delimited-[] 𝑋 𝐺 [X/G] [ italic_X / italic_G ] .


Definition 1.1 .

A 𝐴 A italic_A -number a 𝑎 a italic_a is left divisor of A 𝐴 A italic_A -number b 𝑏 b italic_b , if there exists A 𝐴 A italic_A -number c 𝑐 c italic_c such that

(1.1) a c = b 𝑎 𝑐 𝑏 ac=b italic_a italic_c = italic_b

Definition 1.2 .

A 𝐴 A italic_A -number a 𝑎 a italic_a is right divisor of A 𝐴 A italic_A -number b 𝑏 b italic_b , if there exists A 𝐴 A italic_A -number c 𝑐 c italic_c such that

(1.2) c a = b 𝑐 𝑎 𝑏 ca=b italic_c italic_a = italic_b

Definition 1.3 .

A 𝐴 A italic_A -number a 𝑎 a italic_a is divisor of A 𝐴 A italic_A -number b 𝑏 b italic_b , if there exists A A tensor-product 𝐴 𝐴 A\otimes A italic_A ⊗ italic_A -number c 𝑐 c italic_c such that

c a = b 𝑐 𝑎 𝑏 c\circ a=b italic_c ∘ italic_a = italic_b

A A tensor-product 𝐴 𝐴 A\otimes A italic_A ⊗ italic_A -number c 𝑐 c italic_c is called quotient of A 𝐴 A italic_A -number b 𝑏 b italic_b divided by A 𝐴 A italic_A -number a 𝑎 a italic_a . ∎

Definition 5.1 .

Let division in the D 𝐷 D italic_D -algebra A 𝐴 A italic_A is not always defined. A 𝐴 A italic_A -number a 𝑎 a italic_a divides A 𝐴 A italic_A -number b 𝑏 b italic_b with remainder , if the following equation is true

(5.1) c a + f = b 𝑐 𝑎 𝑓 𝑏 c\circ a+f=b italic_c ∘ italic_a + italic_f = italic_b

A A tensor-product 𝐴 𝐴 A\otimes A italic_A ⊗ italic_A -number c 𝑐 c italic_c is called quotient of A 𝐴 A italic_A -number b 𝑏 b italic_b divided by A 𝐴 A italic_A -number a 𝑎 a italic_a . A 𝐴 A italic_A -number f 𝑓 f italic_f is called remainder of the division of A 𝐴 A italic_A -number b 𝑏 b italic_b by A 𝐴 A italic_A -number a 𝑎 a italic_a .

Definition 5.4 .

We define canonical remainder b mod a 𝑏 normal-mod 𝑎 {\color[rgb]{.4,0,.9}b\ \mathrm{mod}\ a} italic_b roman_mod italic_a of the division of A 𝐴 A italic_A -number b 𝑏 b italic_b by A 𝐴 A italic_A -number a 𝑎 a italic_a as selected element of the set A { b , a } 𝐴 𝑏 𝑎 A\{b,a\} italic_A { italic_b , italic_a } . The representation

c a + ( b mod a ) = b 𝑐 𝑎 𝑏 mod 𝑎 𝑏 c\circ a+(b\ \mathrm{mod}\ a)=b italic_c ∘ italic_a + ( italic_b roman_mod italic_a ) = italic_b

of division with remainder is called canonical .


Definition 1.1 .

Let k , q , k , q 𝑘 𝑞 superscript 𝑘 superscript 𝑞 k,q,k^{\prime},q^{\prime} italic_k , italic_q , italic_k start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT , italic_q start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT be non-negative integers where q , q 0 𝑞 superscript 𝑞 0 q,q^{\prime}\neq 0 italic_q , italic_q start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ≠ 0 and gcd ( k , q ) = 1 𝑘 𝑞 1 \gcd(k,q)=1 roman_gcd ( italic_k , italic_q ) = 1 . Further, suppose that

k q - k q = 1 . 𝑘 superscript 𝑞 superscript 𝑘 𝑞 1 kq^{\prime}-k^{\prime}q=1. italic_k italic_q start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT - italic_k start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT italic_q = 1 .

If q q 1 𝑞 superscript 𝑞 1 q\geq q^{\prime}\geq 1 italic_q ≥ italic_q start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ≥ 1 , then ( k , q ) superscript 𝑘 superscript 𝑞 (k^{\prime},q^{\prime}) ( italic_k start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT , italic_q start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) is said to be the lower parent of ( k , q ) 𝑘 𝑞 (k,q) ( italic_k , italic_q ) .


Definition 1

The operators ( a , b ) 𝑎 𝑏 (a,b) ( italic_a , italic_b ) are 𝒟 𝒟 {\mathcal{D}} caligraphic_D -pseudo bosonic ( 𝒟 𝒟 {\mathcal{D}} caligraphic_D -pb) if, for all f 𝒟 𝑓 𝒟 f\in{\mathcal{D}} italic_f ∈ caligraphic_D , we have

a b f - b a f = f . 𝑎 𝑏 𝑓 𝑏 𝑎 𝑓 𝑓 a\,b\,f-b\,a\,f=f. italic_a italic_b italic_f - italic_b italic_a italic_f = italic_f . (2.1)

Definition 1.0 .

Let ν 𝜈 \nu italic_ν be a primitive of the volume form Ω Ω \Omega roman_Ω and 𝐟 : \RR ^ n \RR ^ n : 𝐟 maps-to \RR ^ 𝑛 \RR ^ 𝑛 \mathbf{f}:\RR^n\mapsto\RR^n bold_f : ^ italic_n ↦ ^ italic_n an exact volume preserving diffeomorphism such that

𝐟 ^ * ν - ν = d λ , 𝐟 ^ 𝜈 𝜈 𝑑 𝜆 \mathbf{f}^{*}{\nu}-\nu=d\lambda, bold_f ^ * italic_ν - italic_ν = italic_d italic_λ , (2)

for a n - 2 𝑛 2 n-2 italic_n - 2 form λ 𝜆 \lambda italic_λ . The differential form λ 𝜆 \lambda italic_λ is called a generating form with respect to ν 𝜈 \nu italic_ν .

Definition 1.0 .

Let ν , ν ~ 𝜈 ~ 𝜈 \nu,\tilde{\nu} italic_ν , ~ start_ARG italic_ν end_ARG be two primitives of a volume form Ω Ω \Omega roman_Ω , i.e. d ν = d ν ~ = Ω 𝑑 𝜈 𝑑 ~ 𝜈 Ω d\nu=d\tilde{\nu}=\Omega italic_d italic_ν = italic_d ~ start_ARG italic_ν end_ARG = roman_Ω and 𝐟 : \RR ^ n \RR ^ n : 𝐟 maps-to \RR ^ 𝑛 \RR ^ 𝑛 \mathbf{f}:\RR^n\mapsto\RR^n bold_f : ^ italic_n ↦ ^ italic_n an exact volume preserving diffeomorphism such that

𝐟 ^ * ν ~ - ν = d λ , 𝐟 ^ ~ 𝜈 𝜈 𝑑 𝜆 \mathbf{f}^{*}\tilde{\nu}-\nu=d\lambda, bold_f ^ * ~ start_ARG italic_ν end_ARG - italic_ν = italic_d italic_λ , (3)

for a n - 2 𝑛 2 n-2 italic_n - 2 form λ 𝜆 \lambda italic_λ . The n - 2 𝑛 2 n-2 italic_n - 2 differential form λ 𝜆 \lambda italic_λ is called a generating form with respect to ( ν , ν ~ ) 𝜈 normal-~ 𝜈 (\nu,\tilde{\nu}) ( italic_ν , ~ start_ARG italic_ν end_ARG ) .


Definition 1.2 .

Let 𝒴 𝒴 \mathcal{Y} caligraphic_Y be the class of quarter plane walks using steps from the set

{ ( 1 , - 1 ) , ( - 1 , 0 ) , ( 0 , 1 ) } = { , , } . 1 1 1 0 0 1 \{(1,-1),(-1,0),(0,1)\}=\{\searrow,\leftarrow,\uparrow\}. { ( 1 , - 1 ) , ( - 1 , 0 ) , ( 0 , 1 ) } = { ↘ , ← , ↑ } .

Let 𝒮 𝒮 \mathcal{S} caligraphic_S be the class of quarter plane walks using steps from the set

{ ( 1 , 0 ) , ( 1 , - 1 ) , ( 0 , - 1 ) , ( - 1 , 0 ) , ( - 1 , 1 ) , ( 0 , 1 ) } = { , , , , , } . 1 0 1 1 0 1 1 0 1 1 0 1 \{(1,0),(1,-1),(0,-1),(-1,0),(-1,1),(0,1)\}=\{\rightarrow,\searrow,\downarrow,% \leftarrow,\nwarrow,\uparrow\}. { ( 1 , 0 ) , ( 1 , - 1 ) , ( 0 , - 1 ) , ( - 1 , 0 ) , ( - 1 , 1 ) , ( 0 , 1 ) } = { → , ↘ , ↓ , ← , ↖ , ↑ } .

Definition 2.6 .

Let ( A , α ) 𝐴 𝛼 (A,\alpha) ( italic_A , italic_α ) and ( B , β ) 𝐵 𝛽 (B,\beta) ( italic_B , italic_β ) be two monoidal Hom-algebras. A left ( A , α ) 𝐴 𝛼 (A,\alpha) ( italic_A , italic_α ) , right ( B , β ) 𝐵 𝛽 (B,\beta) ( italic_B , italic_β ) Hom-bimodule consists of an object ( M , μ ) ~ ( k ) 𝑀 𝜇 ~ subscript 𝑘 (M,\mu)\in\widetilde{\mathcal{H}}(\mathcal{M}_{k}) ( italic_M , italic_μ ) ∈ ~ start_ARG caligraphic_H end_ARG ( caligraphic_M start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ) together with a left ( A , α ) 𝐴 𝛼 (A,\alpha) ( italic_A , italic_α ) -Hom-action ϕ : A M M : italic-ϕ tensor-product 𝐴 𝑀 𝑀 \phi:A\otimes M\to M italic_ϕ : italic_A ⊗ italic_M → italic_M , ϕ ( a m ) = a m italic-ϕ tensor-product 𝑎 𝑚 𝑎 𝑚 \phi(a\otimes m)=am italic_ϕ ( italic_a ⊗ italic_m ) = italic_a italic_m and a right ( B , β ) 𝐵 𝛽 (B,\beta) ( italic_B , italic_β ) -Hom-action φ : M B M : 𝜑 tensor-product 𝑀 𝐵 𝑀 \varphi:M\otimes B\to M italic_φ : italic_M ⊗ italic_B → italic_M , φ ( m b ) = m b 𝜑 tensor-product 𝑚 𝑏 𝑚 𝑏 \varphi(m\otimes b)=mb italic_φ ( italic_m ⊗ italic_b ) = italic_m italic_b fulfilling the compatibility condition, for all a A 𝑎 𝐴 a\in A italic_a ∈ italic_A , b B 𝑏 𝐵 b\in B italic_b ∈ italic_B and m M 𝑚 𝑀 m\in M italic_m ∈ italic_M ,

(2.15) ( a m ) β ( b ) = α ( a ) ( m b ) . 𝑎 𝑚 𝛽 𝑏 𝛼 𝑎 𝑚 𝑏 (am)\beta(b)=\alpha(a)(mb). ( italic_a italic_m ) italic_β ( italic_b ) = italic_α ( italic_a ) ( italic_m italic_b ) .

We call a left ( A , α ) 𝐴 𝛼 (A,\alpha) ( italic_A , italic_α ) , right ( B , β ) 𝐵 𝛽 (B,\beta) ( italic_B , italic_β ) Hom-bimodule a [ ( A , α ) , ( B , β ) ] 𝐴 𝛼 𝐵 𝛽 [(A,\alpha),(B,\beta)] [ ( italic_A , italic_α ) , ( italic_B , italic_β ) ] -Hom-bimodule. Let ( M , μ ) 𝑀 𝜇 (M,\mu) ( italic_M , italic_μ ) and ( N , ν ) 𝑁 𝜈 (N,\nu) ( italic_N , italic_ν ) be two [ ( A , α ) , ( B , β ) ] 𝐴 𝛼 𝐵 𝛽 [(A,\alpha),(B,\beta)] [ ( italic_A , italic_α ) , ( italic_B , italic_β ) ] -Hom-bimodules. A morphism f : M N : 𝑓 𝑀 𝑁 f:M\to N italic_f : italic_M → italic_N is called a morphism of [ ( A , α ) , ( B , β ) ] 𝐴 𝛼 𝐵 𝛽 [(A,\alpha),(B,\beta)] [ ( italic_A , italic_α ) , ( italic_B , italic_β ) ] -Hom-bimodules if it is both left ( A , α ) 𝐴 𝛼 (A,\alpha) ( italic_A , italic_α ) -linear and right ( B , β ) 𝐵 𝛽 (B,\beta) ( italic_B , italic_β ) -linear, and satisfies the following property

(2.16) ( a f ( m ) ) β ( b ) = α ( a ) ( f ( m ) b ) , 𝑎 𝑓 𝑚 𝛽 𝑏 𝛼 𝑎 𝑓 𝑚 𝑏 (af(m))\beta(b)=\alpha(a)(f(m)b), ( italic_a italic_f ( italic_m ) ) italic_β ( italic_b ) = italic_α ( italic_a ) ( italic_f ( italic_m ) italic_b ) ,

for all a A 𝑎 𝐴 a\in A italic_a ∈ italic_A , b B 𝑏 𝐵 b\in B italic_b ∈ italic_B and m M 𝑚 𝑀 m\in M italic_m ∈ italic_M .


Definition 1 (Rotations, Reflections and Translations) .

A matrix of the form

( a - b b a ) , a 2 + b 2 = 1 𝑎 𝑏 𝑏 𝑎 superscript 𝑎 2 superscript 𝑏 2 1 \left(\begin{array}[]{cc}a&-b\\ b&a\end{array}\right),\ a^{2}+b^{2}=1 ( start_ARRAY start_ROW start_CELL italic_a end_CELL start_CELL - italic_b end_CELL end_ROW start_ROW start_CELL italic_b end_CELL start_CELL italic_a end_CELL end_ROW end_ARRAY ) , italic_a start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT + italic_b start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT = 1

is called a rotation matrix, and a matrix of the form

( a b b - a ) , a 2 + b 2 = 1 𝑎 𝑏 𝑏 𝑎 superscript 𝑎 2 superscript 𝑏 2 1 \left(\begin{array}[]{cc}a&b\\ b&-a\end{array}\right),\ a^{2}+b^{2}=1 ( start_ARRAY start_ROW start_CELL italic_a end_CELL start_CELL italic_b end_CELL end_ROW start_ROW start_CELL italic_b end_CELL start_CELL - italic_a end_CELL end_ROW end_ARRAY ) , italic_a start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT + italic_b start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT = 1

is called a reflection matrix. If 𝐮 𝔽 q 2 𝐮 superscript subscript 𝔽 𝑞 2 \textbf{{u}}\in\mathbb{F}_{q}^{2} u ∈ blackboard_F start_POSTSUBSCRIPT italic_q end_POSTSUBSCRIPT start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT and R 𝑅 R italic_R is a rotation matrix, then a rotation about u by R 𝑅 R italic_R is an affine map of the form

( 𝒗 ) = R ( 𝒗 - 𝒖 ) + 𝒖 . 𝒗 𝑅 𝒗 𝒖 𝒖 {\mathcal{R}}(\textbf{{v}})=R(\textbf{{v}}-\textbf{{u}})+\textbf{{u}}. caligraphic_R ( v ) = italic_R ( v - u ) + u .

If 𝐮 𝔽 q 2 𝐮 superscript subscript 𝔽 𝑞 2 \textbf{{u}}\in\mathbb{F}_{q}^{2} u ∈ blackboard_F start_POSTSUBSCRIPT italic_q end_POSTSUBSCRIPT start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT and S 𝑆 S italic_S is a reflection matrix, then a reflection about u by S 𝑆 S italic_S is an affine map of the form

𝒮 ( 𝒗 ) = S ( 𝒗 - 𝒖 ) + 𝒖 . 𝒮 𝒗 𝑆 𝒗 𝒖 𝒖 {\mathcal{S}}(\textbf{{v}})=S(\textbf{{v}}-\textbf{{u}})+\textbf{{u}}. caligraphic_S ( v ) = italic_S ( v - u ) + u .

A translation by u is an affine map of the form

𝒯 ( 𝒗 ) = 𝒗 + 𝒖 . 𝒯 𝒗 𝒗 𝒖 {\mathcal{T}}(\textbf{{v}})=\textbf{{v}}+\textbf{{u}}. caligraphic_T ( v ) = v + u .

Definition 2.2 .

Let 𝔤 𝔤 {\mathfrak{g}} fraktur_g be a Lie bialgebra. A left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -crossed module ( V , , α ) 𝑉 𝛼 (V,{\triangleright},\alpha) ( italic_V , ▷ , italic_α ) is a left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -module ( V , ) 𝑉 (V,{\triangleright}) ( italic_V , ▷ ) that admits a left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -coaction α : V 𝔤 V : 𝛼 𝑉 tensor-product 𝔤 𝑉 \alpha:V\to{\mathfrak{g}}\otimes V italic_α : italic_V → fraktur_g ⊗ italic_V such that

α ( x v ) = ( [ x , ] id + id x ) α ( v ) + δ ( x ) v fragments α fragments ( x v ) fragments ( fragments [ x , ] tensor-product id id tensor-product x ) α fragments ( v ) δ fragments ( x ) v \alpha(x{\triangleright}v)=([x,\ ]\otimes{\rm id}+{\rm id}\otimes x{% \triangleright})\alpha(v)+\delta(x){\triangleright}v italic_α ( italic_x ▷ italic_v ) = ( [ italic_x , ] ⊗ roman_id + roman_id ⊗ italic_x ▷ ) italic_α ( italic_v ) + italic_δ ( italic_x ) ▷ italic_v

for any x 𝔤 , v V . formulae-sequence 𝑥 𝔤 𝑣 𝑉 x\in{\mathfrak{g}},v\in V. italic_x ∈ fraktur_g , italic_v ∈ italic_V .

In the case of 𝔤 𝔤 {\mathfrak{g}} fraktur_g is finite-dimensional, the notion of a left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -crossed module is equivalent to a left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -module ( V , ) 𝑉 (V,{\triangleright}) ( italic_V , ▷ ) that admits a left 𝔤 * o p superscript 𝔤 absent 𝑜 𝑝 {\mathfrak{g}}^{*op} fraktur_g start_POSTSUPERSCRIPT * italic_o italic_p end_POSTSUPERSCRIPT -action superscript {\triangleright}^{\prime} ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT satisfying

(2.4) ϕ ( 1 ) v ϕ , ( 2 ) x + x ( 1 ) v ϕ , x ( 2 ) = x ( ϕ v ) - ϕ ( x v ) fragments ϕ subscript superscript 1 v fragments ϕ subscript , 2 x x subscript 1 v fragments ϕ , x subscript 2 x fragments ( ϕ superscript v ) ϕ superscript fragments ( x v ) \phi{}_{(1)}{\triangleright}^{\prime}v{\langle}\phi{}_{(2)},x{\rangle}+x{}_{(1% )}{\triangleright}v{\langle}\phi,x{}_{(2)}{\rangle}=x{\triangleright}(\phi{% \triangleright}^{\prime}v)-\phi{\triangleright}^{\prime}(x{\triangleright}v) italic_ϕ start_FLOATSUBSCRIPT ( 1 ) end_FLOATSUBSCRIPT ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT italic_v ⟨ italic_ϕ start_FLOATSUBSCRIPT ( 2 ) end_FLOATSUBSCRIPT , italic_x ⟩ + italic_x start_FLOATSUBSCRIPT ( 1 ) end_FLOATSUBSCRIPT ▷ italic_v ⟨ italic_ϕ , italic_x start_FLOATSUBSCRIPT ( 2 ) end_FLOATSUBSCRIPT ⟩ = italic_x ▷ ( italic_ϕ ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT italic_v ) - italic_ϕ ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_x ▷ italic_v )

for any x 𝔤 , ϕ 𝔤 * formulae-sequence 𝑥 𝔤 italic-ϕ superscript 𝔤 x\in{\mathfrak{g}},\,\phi\in{\mathfrak{g}}^{*} italic_x ∈ fraktur_g , italic_ϕ ∈ fraktur_g start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT and v V , 𝑣 𝑉 v\in V, italic_v ∈ italic_V , where the left 𝔤 * o p superscript 𝔤 absent 𝑜 𝑝 {\mathfrak{g}}^{*op} fraktur_g start_POSTSUPERSCRIPT * italic_o italic_p end_POSTSUPERSCRIPT -action superscript {\triangleright}^{\prime} ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT corresponds to the left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -coaction α 𝛼 \alpha italic_α above via ϕ v = ϕ , v ( 1 ) v ( 2 ) fragments ϕ superscript v fragments ϕ , v superscript 1 v 2 \phi{\triangleright}^{\prime}v={\langle}\phi,v{}^{(1)}{\rangle}v{}^{(2)} italic_ϕ ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT italic_v = ⟨ italic_ϕ , italic_v start_FLOATSUPERSCRIPT ( 1 ) end_FLOATSUPERSCRIPT ⟩ italic_v start_FLOATSUPERSCRIPT ( 2 ) end_FLOATSUPERSCRIPT with α ( v ) = v ( 1 ) v . ( 2 ) fragments α fragments ( v ) v superscript tensor-product 1 v superscript . 2 \alpha(v)=v{}^{(1)}\otimes v{}^{(2)}. italic_α ( italic_v ) = italic_v start_FLOATSUPERSCRIPT ( 1 ) end_FLOATSUPERSCRIPT ⊗ italic_v start_FLOATSUPERSCRIPT ( 2 ) end_FLOATSUPERSCRIPT .

We call a left 𝔤 𝔤 {\mathfrak{g}} fraktur_g -module V 𝑉 V italic_V with linear map : 𝔤 * V V fragments superscript : superscript 𝔤 tensor-product V V {\triangleright}^{\prime}:{\mathfrak{g}}^{*}\otimes V\to V ▷ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT : fraktur_g start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ italic_V → italic_V (not necessarily an action) such that ( 2.4 ) a left almost 𝔤 𝔤 {\mathfrak{g}} fraktur_g -crossed module .


Definition 1.3 .

We say that a connected Lie group M 𝑀 M italic_M is unimodular if

𝑡𝑟𝑎𝑐𝑒 ( 𝑎𝑑 ( m ) ) = 0 , m 𝔪 , formulae-sequence 𝑡𝑟𝑎𝑐𝑒 𝑎𝑑 𝑚 0 for-all 𝑚 𝔪 \text{trace}\left(\text{ad}(m)\right)=0,\;\forall m\in\mathfrak{m}, trace ( ad ( italic_m ) ) = 0 , ∀ italic_m ∈ fraktur_m ,

where 𝔪 𝔪 \mathfrak{m} fraktur_m denotes the Lie Algebra of M 𝑀 M italic_M .