Definition 2.1 .

Let G 𝐺 G italic_G be a graph and let Γ S 1 normal-Γ superscript 𝑆 1 \Gamma\subseteq S^{1} roman_Γ ⊆ italic_S start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT be a group. A signature for G 𝐺 G italic_G is a map s : E o r Γ normal-: 𝑠 normal-→ superscript 𝐸 𝑜 𝑟 normal-Γ s:E^{or}\to\Gamma italic_s : italic_E start_POSTSUPERSCRIPT italic_o italic_r end_POSTSUPERSCRIPT → roman_Γ such that

s ( e ¯ ) = s ( e ) - 1 , 𝑠 ¯ 𝑒 𝑠 superscript 𝑒 1 s(\bar{e})=s(e)^{-1}, italic_s ( ¯ start_ARG italic_e end_ARG ) = italic_s ( italic_e ) start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT , (2.1)

where s ( e ) - 1 𝑠 superscript 𝑒 1 s(e)^{-1} italic_s ( italic_e ) start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT is the inverse of s ( e ) 𝑠 𝑒 s(e) italic_s ( italic_e ) in Γ normal-Γ \Gamma roman_Γ . The trivial signature s 1 𝑠 1 s\equiv 1 italic_s ≡ 1 , is denoted by s 1 subscript 𝑠 1 s_{1} italic_s start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT . For an oriented edge e = ( u , v ) E o r 𝑒 𝑢 𝑣 superscript 𝐸 𝑜 𝑟 e=(u,v)\in E^{or} italic_e = ( italic_u , italic_v ) ∈ italic_E start_POSTSUPERSCRIPT italic_o italic_r end_POSTSUPERSCRIPT , we will almost always write s u v := s ( e ) assign subscript 𝑠 𝑢 𝑣 𝑠 𝑒 s_{uv}:=s(e) italic_s start_POSTSUBSCRIPT italic_u italic_v end_POSTSUBSCRIPT := italic_s ( italic_e ) for simplicity.


Definition 2.4 .

A Riemannian manifold ( M , g , Q ) 𝑀 𝑔 𝑄 (M,g,Q) ( italic_M , italic_g , italic_Q ) is called almost Einstein if the metrics g 𝑔 g italic_g and g ~ ~ 𝑔 \tilde{g} ~ start_ARG italic_g end_ARG satisfy

ρ ( x , y ) = α g ( x , y ) + β g ~ ( x , y ) , 𝜌 𝑥 𝑦 𝛼 𝑔 𝑥 𝑦 𝛽 ~ 𝑔 𝑥 𝑦 \rho(x,y)=\alpha g(x,y)+\beta\tilde{g}(x,y), italic_ρ ( italic_x , italic_y ) = italic_α italic_g ( italic_x , italic_y ) + italic_β ~ start_ARG italic_g end_ARG ( italic_x , italic_y ) ,

where α 𝛼 \alpha italic_α and β 𝛽 \beta italic_β are smooth functions on M 𝑀 M italic_M .


Definition 2.16 .

[ S ] Let ( 𝔤 , ) 𝔤 (\mathfrak{g},\cdot) ( fraktur_g , ⋅ ) be a finite dimensional left symmetric algebra. A scalar product k 𝑘 k italic_k on 𝔤 𝔤 \mathfrak{g} fraktur_g is said to be left symmetric if it verifies

k ( x y - y x , z ) = k ( x , y z ) - k ( y , x z ) , x , y , z 𝔤 . formulae-sequence 𝑘 𝑥 𝑦 𝑦 𝑥 𝑧 𝑘 𝑥 𝑦 𝑧 𝑘 𝑦 𝑥 𝑧 𝑥 𝑦 𝑧 𝔤 k(x\cdot y-y\cdot x,z)=k(x,y\cdot z)-k(y,x\cdot z),\qquad x,y,z\in\mathfrak{g}. italic_k ( italic_x ⋅ italic_y - italic_y ⋅ italic_x , italic_z ) = italic_k ( italic_x , italic_y ⋅ italic_z ) - italic_k ( italic_y , italic_x ⋅ italic_z ) , italic_x , italic_y , italic_z ∈ fraktur_g . (4)

Moreover, if 𝔤 𝔤 \mathfrak{g} fraktur_g is a Lie algebra whose Lie bracket is given by the commutator of \cdot the triple ( 𝔤 , , k ) 𝔤 𝑘 (\mathfrak{g},\cdot,k) ( fraktur_g , ⋅ , italic_k ) is called a pseudo-Hessian Lie algebra .


Definition A.22 .

Given the tensor product J = G × H 𝐽 𝐺 𝐻 J=G\times H italic_J = italic_G × italic_H of graphs G 𝐺 G italic_G and H 𝐻 H italic_H , define f : V ( J ) V ( G ) normal-: 𝑓 normal-→ 𝑉 𝐽 𝑉 𝐺 f:V(J)\rightarrow V(G) italic_f : italic_V ( italic_J ) → italic_V ( italic_G ) so that for all ( u , v ) V ( J ) 𝑢 𝑣 𝑉 𝐽 (u,v)\in V(J) ( italic_u , italic_v ) ∈ italic_V ( italic_J ) ,

f ( ( u , v ) ) = u . 𝑓 𝑢 𝑣 𝑢 f((u,v))=u. italic_f ( ( italic_u , italic_v ) ) = italic_u .

Define g : V ( G ) 𝒫 ( V ( J ) ) normal-: 𝑔 normal-→ 𝑉 𝐺 𝒫 𝑉 𝐽 g:V(G)\rightarrow\mathcal{P}(V(J)) italic_g : italic_V ( italic_G ) → caligraphic_P ( italic_V ( italic_J ) ) so that for all u V ( G ) 𝑢 𝑉 𝐺 u\in V(G) italic_u ∈ italic_V ( italic_G ) ,

g ( u ) = f - 1 ( u ) = { ( u , v ) v V ( H ) } . 𝑔 𝑢 superscript 𝑓 1 𝑢 conditional-set 𝑢 𝑣 𝑣 𝑉 𝐻 g(u)=f^{-1}(u)=\{(u,v)\mid v\in V(H)\}. italic_g ( italic_u ) = italic_f start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT ( italic_u ) = { ( italic_u , italic_v ) ∣ italic_v ∈ italic_V ( italic_H ) } .

Definition 4.1 .

[ 19 ] A 3-Lie algebra is a vector space A 𝐴 A italic_A together with a skew-symmetric linear map ( 3 3 3 3 -Lie bracket) [ , , ] : 3 A A fragments fragments [ , , ] : superscript tensor-product 3 A A [\;,\;,\;]:\otimes^{3}A\rightarrow A [ , , ] : ⊗ start_POSTSUPERSCRIPT 3 end_POSTSUPERSCRIPT italic_A → italic_A such that the following Fundamental Identity (FI) holds:

[ [ x , y , z ] , u , v ] = [ [ x , u , v ] , y , z ] + [ [ y , u , v ] , z , x ] + [ [ z , u , v ] , x , y ] , 𝑥 𝑦 𝑧 𝑢 𝑣 𝑥 𝑢 𝑣 𝑦 𝑧 𝑦 𝑢 𝑣 𝑧 𝑥 𝑧 𝑢 𝑣 𝑥 𝑦 [[x,y,z],u,v]=[[x,u,v],y,z]+[[y,u,v],z,x]+[[z,u,v],x,y], [ [ italic_x , italic_y , italic_z ] , italic_u , italic_v ] = [ [ italic_x , italic_u , italic_v ] , italic_y , italic_z ] + [ [ italic_y , italic_u , italic_v ] , italic_z , italic_x ] + [ [ italic_z , italic_u , italic_v ] , italic_x , italic_y ] , (32)

for x , y , z , u , v A 𝑥 𝑦 𝑧 𝑢 𝑣 𝐴 x,y,z,u,v\in A italic_x , italic_y , italic_z , italic_u , italic_v ∈ italic_A .


Definition 4.1 .

(Symmetrical solution) The solution z ( t , x ) = ( ρ , u , v ) 𝑧 𝑡 𝑥 𝜌 𝑢 𝑣 z(t,x)=(\rho,u,v) italic_z ( italic_t , italic_x ) = ( italic_ρ , italic_u , italic_v ) to 3NS is x 𝑥 x italic_x -symmetric if there exists a function b ( t ) C 1 ( 0 , + ) 𝑏 𝑡 superscript 𝐶 1 0 b(t)\in C^{1}(0,+\infty) italic_b ( italic_t ) ∈ italic_C start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ( 0 , + ∞ ) such that

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

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 1.11 .

Let 0 < p < 1 0 𝑝 1 0<p<1 0 < italic_p < 1 be rational. A p 𝑝 p italic_p -martingale is a function m : 2 < ω 0 normal-: 𝑚 normal-→ superscript 2 absent 𝜔 superscript absent 0 m:2^{<\omega}\to\mathbb{R}^{\geq 0} italic_m : 2 start_POSTSUPERSCRIPT < italic_ω end_POSTSUPERSCRIPT → blackboard_R start_POSTSUPERSCRIPT ≥ 0 end_POSTSUPERSCRIPT such that

m ( σ ) = ( 1 - p ) m ( σ 0 ) + p m ( σ 1 ) 𝑚 𝜎 1 𝑝 𝑚 𝜎 0 𝑝 𝑚 𝜎 1 m(\sigma)=(1-p)m(\sigma 0)+pm(\sigma 1) italic_m ( italic_σ ) = ( 1 - italic_p ) italic_m ( italic_σ 0 ) + italic_p italic_m ( italic_σ 1 )

for all σ 𝜎 \sigma italic_σ . A p 𝑝 p italic_p -supermartingale is a function s : 2 < ω 0 normal-: 𝑠 normal-→ superscript 2 absent 𝜔 superscript absent 0 s:2^{<\omega}\to\mathbb{R}^{\geq 0} italic_s : 2 start_POSTSUPERSCRIPT < italic_ω end_POSTSUPERSCRIPT → blackboard_R start_POSTSUPERSCRIPT ≥ 0 end_POSTSUPERSCRIPT with

s ( σ ) ( 1 - p ) s ( σ 0 ) + p s ( σ 1 ) 𝑠 𝜎 1 𝑝 𝑠 𝜎 0 𝑝 𝑠 𝜎 1 s(\sigma)\geq(1-p)s(\sigma 0)+ps(\sigma 1) italic_s ( italic_σ ) ≥ ( 1 - italic_p ) italic_s ( italic_σ 0 ) + italic_p italic_s ( italic_σ 1 )

for all σ 𝜎 \sigma italic_σ . A p 𝑝 p italic_p -(super)martingale m 𝑚 m italic_m succeeds on a set X 𝑋 X italic_X if lim sup n m ( X n ) = fragments subscript limit-supremum normal-→ 𝑛 m fragments normal-( X normal-↾ n normal-) \limsup_{n\to\infty}m(X\upharpoonright n)=\infty lim sup start_POSTSUBSCRIPT italic_n → ∞ end_POSTSUBSCRIPT italic_m ( italic_X ↾ italic_n ) = ∞ . A set X 𝑋 X italic_X is p 𝑝 p italic_p -1-Random if no computably enumerable p 𝑝 p italic_p -supermartingale succeeds on it.


Definition 4.3 ( [ Pym17 , Theorem 4.5] ) .

Let X 𝑋 X italic_X be a smooth fourfold, and let Y 𝑌 Y italic_Y be a divisor in X 𝑋 X italic_X . A log symplectic structure σ 𝜎 \sigma italic_σ on ( X , Y ) 𝑋 𝑌 (X,Y) ( italic_X , italic_Y ) is purely elliptic if there are local holomorphic coordinates around each singular point of Y 𝑌 Y italic_Y in which Y 𝑌 Y italic_Y is given by one of the equations in Table 1 and σ 𝜎 \sigma italic_σ is of the form

σ = d log f d w - a x d y d z λ f + b y d x d z λ f - c z d x d y λ f 𝜎 𝑑 𝑓 𝑑 𝑤 𝑎 𝑥 𝑑 𝑦 𝑑 𝑧 𝜆 𝑓 𝑏 𝑦 𝑑 𝑥 𝑑 𝑧 𝜆 𝑓 𝑐 𝑧 𝑑 𝑥 𝑑 𝑦 𝜆 𝑓 \sigma=d\log f\wedge dw-a\dfrac{xdy\wedge dz}{\lambda f}+b\dfrac{ydx\wedge dz}% {\lambda f}-c\dfrac{zdx\wedge dy}{\lambda f} italic_σ = italic_d roman_log italic_f ∧ italic_d italic_w - italic_a divide start_ARG italic_x italic_d italic_y ∧ italic_d italic_z end_ARG start_ARG italic_λ italic_f end_ARG + italic_b divide start_ARG italic_y italic_d italic_x ∧ italic_d italic_z end_ARG start_ARG italic_λ italic_f end_ARG - italic_c divide start_ARG italic_z italic_d italic_x ∧ italic_d italic_y end_ARG start_ARG italic_λ italic_f end_ARG

up to scaling.


Definition 6 (Future (past) distinguishing) .

A spacetime , g a b subscript 𝑔 𝑎 𝑏 \langle\mathcal{M},g_{ab}\rangle ⟨ caligraphic_M , italic_g start_POSTSUBSCRIPT italic_a italic_b end_POSTSUBSCRIPT ⟩ is future distinguishing iff, for all p , q 𝑝 𝑞 p,q\in\mathcal{M} italic_p , italic_q ∈ caligraphic_M ,

I + ( p ) = I + ( q ) p = q superscript 𝐼 𝑝 superscript 𝐼 𝑞 𝑝 𝑞 I^{+}(p)=I^{+}(q)\Rightarrow p=q italic_I start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT ( italic_p ) = italic_I start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT ( italic_q ) ⇒ italic_p = italic_q

(and similarly for past distinguishing ).


Definition 3.2 (Uniqueness in law) .

We endow the space C ( ) 𝐶 C(\mathbb{R}) italic_C ( roman_ℝ ) with the σ 𝜎 \sigma italic_σ -algebra generated by the topology of uniform convergence. Moreover, we equip the space C ( [ 0 , T ] , C ( ) ) 𝐶 0 𝑇 𝐶 C([0,T],C(\mathbb{R})) italic_C ( [ 0 , italic_T ] , italic_C ( roman_ℝ ) ) with the corresponding Borel σ 𝜎 \sigma italic_σ -algebra which we denote ( C ( [ 0 , T ] , C ( ) ) ) 𝐶 0 𝑇 𝐶 \mathcal{B}(C([0,T],C(\mathbb{R}))) caligraphic_B ( italic_C ( [ 0 , italic_T ] , italic_C ( roman_ℝ ) ) ) .
Recall, that if ( u , v ) 𝑢 𝑣 (u,v) ( italic_u , italic_v ) is a solution of the system ( 1.1 ) italic-( 1.1 italic-) \eqref{eq:SteppingStoneWithSeedbank} italic_( italic_) then we have for v 𝑣 v italic_v by Theorem 2.14 that

v ( t , x ) = e - c t v ( 0 , x ) + v ~ ( t , x ) 𝑣 𝑡 𝑥 superscript 𝑒 𝑐 𝑡 𝑣 0 𝑥 ~ 𝑣 𝑡 𝑥 \displaystyle v(t,x)=e^{-ct}v(0,x)+\tilde{v}(t,x) italic_v ( italic_t , italic_x ) = italic_e start_POSTSUPERSCRIPT - italic_c italic_t end_POSTSUPERSCRIPT italic_v ( 0 , italic_x ) + ~ start_ARG italic_v end_ARG ( italic_t , italic_x ) (3.7)

where v ~ ~ 𝑣 \tilde{v} ~ start_ARG italic_v end_ARG is a stochastic process taking values in C ( [ 0 , T ] , C ( ) ) 𝐶 0 𝑇 𝐶 C([0,T],C(\mathbb{R})) italic_C ( [ 0 , italic_T ] , italic_C ( roman_ℝ ) ) and v ( 0 , ) B ( ) 𝑣 0 𝐵 v(0,\cdot)\in B(\mathbb{R}) italic_v ( 0 , ⋅ ) ∈ italic_B ( roman_ℝ ) is deterministic. We thus say that the SPDE ( 1.1 ) exhibits uniqueness in law if for any two weak solutions ( ( u 1 , v 1 ) , W 1 , Ω 1 , ( t 1 ) t 0 , 1 ) subscript 𝑢 1 subscript 𝑣 1 subscript 𝑊 1 subscript Ω 1 subscript subscript superscript 1 𝑡 𝑡 0 subscript 1 ((u_{1},v_{1}),W_{1},\allowdisplaybreaks\Omega_{1},(\mathcal{F}^{1}_{t})_{t% \geq 0},\mathbb{P}_{1}) ( ( italic_u start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , italic_v start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ) , italic_W start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , roman_Ω start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , ( caligraphic_F start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_t end_POSTSUBSCRIPT ) start_POSTSUBSCRIPT italic_t ≥ 0 end_POSTSUBSCRIPT , roman_ℙ start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ) and ( ( u 2 , v 2 ) , W 2 , Ω 2 , ( t 2 ) t 0 , 2 ) subscript 𝑢 2 subscript 𝑣 2 subscript 𝑊 2 subscript Ω 2 subscript subscript superscript 2 𝑡 𝑡 0 subscript 2 ((u_{2},v_{2}),W_{2},\Omega_{2},({\mathcal{F}^{2}_{t}})_{t\geq 0},\mathbb{P}_{% 2}) ( ( italic_u start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , italic_v start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) , italic_W start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , roman_Ω start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , ( caligraphic_F start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_t end_POSTSUBSCRIPT ) start_POSTSUBSCRIPT italic_t ≥ 0 end_POSTSUBSCRIPT , roman_ℙ start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) we have

1 ( ( u 1 , v ~ 1 ) Γ ) = 2 ( ( u 2 , v ~ 2 ) Γ ) fragments subscript 1 fragments ( fragments ( subscript 𝑢 1 , subscript ~ 𝑣 1 ) Γ ) subscript 2 fragments ( fragments ( subscript 𝑢 2 , subscript ~ 𝑣 2 ) Γ ) \displaystyle\mathbb{P}_{1}((u_{1},\tilde{v}_{1})\in\Gamma)=\mathbb{P}_{2}((u_% {2},\tilde{v}_{2})\in\Gamma) roman_ℙ start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ( ( italic_u start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , ~ start_ARG italic_v end_ARG start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ) ∈ roman_Γ ) = roman_ℙ start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ( ( italic_u start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , ~ start_ARG italic_v end_ARG start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) ∈ roman_Γ )

for every Γ ( C ( [ 0 , T ] , C ( ) ) ) ( C ( [ 0 , T ] , C ( ) ) ) Γ tensor-product 𝐶 0 𝑇 𝐶 𝐶 0 𝑇 𝐶 \Gamma\in\mathcal{B}(C([0,T],C(\mathbb{R})))\otimes\mathcal{B}(C([0,T],C(% \mathbb{R}))) roman_Γ ∈ caligraphic_B ( italic_C ( [ 0 , italic_T ] , italic_C ( roman_ℝ ) ) ) ⊗ caligraphic_B ( italic_C ( [ 0 , italic_T ] , italic_C ( roman_ℝ ) ) ) .


Definition 1.1 (Discrete Hessian) .

Let f : 𝕃 : 𝑓 𝕃 f:\mathbb{L}\rightarrow\mathbb{R} italic_f : blackboard_L → blackboard_R be a function defined on 𝕃 𝕃 \mathbb{L} blackboard_L . We define the (discrete) Hessian 2 ( f ) superscript 2 𝑓 \nabla^{2}(f) ∇ start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT ( italic_f ) to be a function from the set E ( 𝕋 n ) 𝐸 subscript 𝕋 𝑛 E(\mathbb{T}_{n}) italic_E ( blackboard_T start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT ) of rhombi of the form { a , b , c , d } 𝑎 𝑏 𝑐 𝑑 \{a,b,c,d\} { italic_a , italic_b , italic_c , italic_d } of side 1 1 1 1 (where the order is anticlockwise, and the angle at a 𝑎 a italic_a is π / 3 𝜋 3 \pi/3 italic_π / 3 ) on the discrete torus to the reals, satisfying

2 f ( { a , b , c , d } ) = - f ( a ) + f ( b ) - f ( c ) + f ( d ) . superscript 2 𝑓 𝑎 𝑏 𝑐 𝑑 𝑓 𝑎 𝑓 𝑏 𝑓 𝑐 𝑓 𝑑 \nabla^{2}f(\{a,b,c,d\})=-f(a)+f(b)-f(c)+f(d). ∇ start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT italic_f ( { italic_a , italic_b , italic_c , italic_d } ) = - italic_f ( italic_a ) + italic_f ( italic_b ) - italic_f ( italic_c ) + italic_f ( italic_d ) .

Definition 2.1 .

Let A 𝐴 A italic_A be a ring and let M 𝑀 M italic_M be an A 𝐴 A italic_A -module. The Nagata idealization A M left-normal-factor-semidirect-product 𝐴 𝑀 A\ltimes M italic_A ⋉ italic_M of M 𝑀 M italic_M is the ring with support A × M 𝐴 𝑀 A\times M italic_A × italic_M and operations defined as follow:

( r , m ) + ( s , n ) = ( r + s , m + n ) , ( r , m ) ( s , n ) = ( r s , s m + r n ) . formulae-sequence 𝑟 𝑚 𝑠 𝑛 𝑟 𝑠 𝑚 𝑛 𝑟 𝑚 𝑠 𝑛 𝑟 𝑠 𝑠 𝑚 𝑟 𝑛 (r,m)+(s,n)=(r+s,m+n),\,(r,m)\cdot(s,n)=(rs,sm+rn). ( italic_r , italic_m ) + ( italic_s , italic_n ) = ( italic_r + italic_s , italic_m + italic_n ) , ( italic_r , italic_m ) ⋅ ( italic_s , italic_n ) = ( italic_r italic_s , italic_s italic_m + italic_r italic_n ) .

Definition 3.3 (Inner Product) .

If a semi-inner product space , normal-⋅ normal-⋅ \langle\cdot,\cdot\rangle ⟨ ⋅ , ⋅ ⟩ satisfies

x , x = 0 x = 0 𝑥 𝑥 0 𝑥 0 \langle x,x\rangle=0\Longrightarrow x=0 ⟨ italic_x , italic_x ⟩ = 0 ⟹ italic_x = 0

then it is called an em inner product.


Definition 5 ( [ 28 ] ) .

Let \mathcal{F} caligraphic_F be a germ of foliation on ( 2 , 0 ) superscript 2 0 ({\mathbb{C}}^{2},0) ( blackboard_C start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT , 0 ) generated by a holomorphic 1 1 1 1 -form ω 𝜔 \omega italic_ω without common factors in its coefficients. Consider an invariant branch Γ normal-Γ \Gamma roman_Γ of \mathcal{F} caligraphic_F given by an irreducible equation f = 0 𝑓 0 f=0 italic_f = 0 . There is an expression

g ω = h d f + f α , 𝑔 𝜔 𝑑 𝑓 𝑓 𝛼 g\omega=hdf+f\alpha, italic_g italic_ω = italic_h italic_d italic_f + italic_f italic_α ,

where α 𝛼 \alpha italic_α is a holomorphic 1 1 1 1 -form and f 𝑓 f italic_f does not divide g 𝑔 g italic_g . The Camacho-Sad index CS 0 ( , Γ ) subscript normal-CS 0 normal-Γ \operatorname{CS}_{0}({\mathcal{F}},\Gamma) roman_CS start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ( caligraphic_F , roman_Γ ) of \mathcal{F} caligraphic_F with respect to Γ normal-Γ \Gamma roman_Γ is defined by

CS 0 ( , Γ ) = - 1 2 π i γ ( f ) α h , subscript CS 0 Γ 1 2 𝜋 𝑖 subscript 𝛾 𝑓 𝛼 \operatorname{CS}_{0}({\mathcal{F}},\Gamma)=\frac{-1}{2\pi i}\int_{\gamma(f)}% \frac{\alpha}{h}, roman_CS start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ( caligraphic_F , roman_Γ ) = divide start_ARG - 1 end_ARG start_ARG 2 italic_π italic_i end_ARG ∫ start_POSTSUBSCRIPT italic_γ ( italic_f ) end_POSTSUBSCRIPT divide start_ARG italic_α end_ARG start_ARG italic_h end_ARG ,

where γ ( f ) 𝛾 𝑓 \gamma(f) italic_γ ( italic_f ) is the homological class of the image of the standard loop z exp ( 2 π i ) maps-to 𝑧 2 𝜋 𝑖 z\mapsto\exp(2\pi i) italic_z ↦ roman_exp ( 2 italic_π italic_i ) under a Puiseux parametrization of Γ normal-Γ \Gamma roman_Γ .


Definition 2.1 .

Let ( A , ) 𝐴 (A,\cdot) ( italic_A , ⋅ ) be an anti-flexible algebra and V 𝑉 V italic_V be a vector space. Let l , r : A End ( V ) : 𝑙 𝑟 𝐴 End 𝑉 \displaystyle l,r:A\rightarrow{\rm End}(V) italic_l , italic_r : italic_A → roman_End ( italic_V ) be two linear maps. If for any x , y A 𝑥 𝑦 𝐴 x,y\in A italic_x , italic_y ∈ italic_A ,

l ( x y ) - l ( x ) l ( y ) = r ( x ) r ( y ) - r ( y x ) , 𝑙 𝑥 𝑦 𝑙 𝑥 𝑙 𝑦 𝑟 𝑥 𝑟 𝑦 𝑟 𝑦 𝑥 \displaystyle l{(x\cdot y)}-l(x)l(y)=r(x)r(y)-r({y\cdot x}), italic_l ( italic_x ⋅ italic_y ) - italic_l ( italic_x ) italic_l ( italic_y ) = italic_r ( italic_x ) italic_r ( italic_y ) - italic_r ( italic_y ⋅ italic_x ) , (2.1)
l ( x ) r ( y ) - r ( y ) l ( x ) = l ( y ) r ( x ) - r ( x ) l ( y ) , 𝑙 𝑥 𝑟 𝑦 𝑟 𝑦 𝑙 𝑥 𝑙 𝑦 𝑟 𝑥 𝑟 𝑥 𝑙 𝑦 \displaystyle l(x)r(y)-r(y)l(x)=l(y)r(x)-r(x)l(y), italic_l ( italic_x ) italic_r ( italic_y ) - italic_r ( italic_y ) italic_l ( italic_x ) = italic_l ( italic_y ) italic_r ( italic_x ) - italic_r ( italic_x ) italic_l ( italic_y ) , (2.2)

then it is called a bimodule of ( A , ) 𝐴 (A,\cdot) ( italic_A , ⋅ ) , denoted by ( l , r , V ) 𝑙 𝑟 𝑉 \displaystyle(l,r,V) ( italic_l , italic_r , italic_V ) . Two bimodules ( l 1 , r 1 , V 1 ) subscript 𝑙 1 subscript 𝑟 1 subscript 𝑉 1 (l_{1},r_{1},V_{1}) ( italic_l start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , italic_r start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , italic_V start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ) and ( l 2 , r 2 , V 2 ) subscript 𝑙 2 subscript 𝑟 2 subscript 𝑉 2 (l_{2},r_{2},V_{2}) ( italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , italic_r start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT , italic_V start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) of an anti-flexible algebra A 𝐴 A italic_A is called equivalent if there exists a linear isomorphism φ : V 1 V 2 : 𝜑 subscript 𝑉 1 subscript 𝑉 2 \varphi:V_{1}\rightarrow V_{2} italic_φ : italic_V start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT → italic_V start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT satisfying

φ l 1 ( x ) = l 2 ( x ) φ , φ r 1 ( x ) = r 2 ( x ) φ , x A . formulae-sequence 𝜑 subscript 𝑙 1 𝑥 subscript 𝑙 2 𝑥 𝜑 formulae-sequence 𝜑 subscript 𝑟 1 𝑥 subscript 𝑟 2 𝑥 𝜑 for-all 𝑥 𝐴 \varphi l_{1}(x)=l_{2}(x)\varphi,\varphi r_{1}(x)=r_{2}(x)\varphi,\;\;\forall x% \in A. italic_φ italic_l start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ( italic_x ) = italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ( italic_x ) italic_φ , italic_φ italic_r start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ( italic_x ) = italic_r start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ( italic_x ) italic_φ , ∀ italic_x ∈ italic_A . (2.3)

Definition 2.1 .

A derivation on a ring {\mathcal{R}} caligraphic_R is a map δ : normal-: 𝛿 normal-→ \delta:{\mathcal{R}}\rightarrow{\mathcal{R}} italic_δ : caligraphic_R → caligraphic_R satisfying that for all a , b 𝑎 𝑏 a,b\in{\mathcal{R}} italic_a , italic_b ∈ caligraphic_R ,

δ ( a + b ) = δ ( a ) + δ ( b ) , δ ( a b ) = δ ( a ) b + a δ ( b ) . formulae-sequence 𝛿 𝑎 𝑏 𝛿 𝑎 𝛿 𝑏 𝛿 𝑎 𝑏 𝛿 𝑎 𝑏 𝑎 𝛿 𝑏 \delta(a+b)=\delta(a)+\delta(b),\,\,\delta(ab)=\delta(a)b+a\delta(b). italic_δ ( italic_a + italic_b ) = italic_δ ( italic_a ) + italic_δ ( italic_b ) , italic_δ ( italic_a italic_b ) = italic_δ ( italic_a ) italic_b + italic_a italic_δ ( italic_b ) .

A ring (resp. field) equipped with a derivation is called a differential ring (resp. differential field). An ideal I 𝐼 I\subset{\mathcal{R}} italic_I ⊂ caligraphic_R is called a differential ideal if δ ( I ) I 𝛿 𝐼 𝐼 \delta(I)\subset I italic_δ ( italic_I ) ⊂ italic_I .


Definition 3.1 .

𝔰 l 2 𝔰 subscript 𝑙 2 \mathfrak{s}l_{2} fraktur_s italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT (respectively 𝒰 ( 𝔰 l 2 ) 𝒰 𝔰 subscript 𝑙 2 {\cal U}(\mathfrak{s}l_{2}) caligraphic_U ( fraktur_s italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) ) is the Lie algebra (respectively the associative algebra) over {\mathbb{Q}} blackboard_Q generated by { e , f , h } 𝑒 𝑓 \{e,f,h\} { italic_e , italic_f , italic_h } with relations

[ h , e ] = 2 e , [ h , f ] = - 2 f , [ e , f ] = h . formulae-sequence 𝑒 2 𝑒 formulae-sequence 𝑓 2 𝑓 𝑒 𝑓 [h,e]=2e,\,[h,f]=-2f,\,[e,f]=h. [ italic_h , italic_e ] = 2 italic_e , [ italic_h , italic_f ] = - 2 italic_f , [ italic_e , italic_f ] = italic_h .

𝒰 ( 𝔰 l 2 ) subscript 𝒰 𝔰 subscript 𝑙 2 {\cal U}_{{\mathbb{Z}}}(\mathfrak{s}l_{2}) caligraphic_U start_POSTSUBSCRIPT blackboard_Z end_POSTSUBSCRIPT ( fraktur_s italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) is the {\mathbb{Z}} blackboard_Z -subalgebra of 𝒰 ( 𝔰 l 2 ) 𝒰 𝔰 subscript 𝑙 2 {\cal U}(\mathfrak{s}l_{2}) caligraphic_U ( fraktur_s italic_l start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) generated by { e ( k ) , f ( k ) | k } conditional-set superscript 𝑒 𝑘 superscript 𝑓 𝑘 𝑘 \{e^{(k)},f^{(k)}|\;k\in{\mathbb{N}}\} { italic_e start_POSTSUPERSCRIPT ( italic_k ) end_POSTSUPERSCRIPT , italic_f start_POSTSUPERSCRIPT ( italic_k ) end_POSTSUPERSCRIPT | italic_k ∈ blackboard_N } .


Definition 6 .

For two predicates p 𝑝 p italic_p and q 𝑞 q italic_q , we say that p 𝑝 p italic_p “if” and only if q 𝑞 q italic_q when both of the following hold:

p q , q μ ( p ) = 1 . formulae-sequence 𝑝 𝑞 𝑞 𝜇 𝑝 1 p\Rightarrow q,\qquad q\Rightarrow\mu(p)=1. italic_p ⇒ italic_q , italic_q ⇒ italic_μ ( italic_p ) = 1 .

Definition 1 (Static stabilizability) .

System ( 1 ) is said to be locally (resp. globally) asymptotically stabilizable by a static state feedback if there exists a locally Lipschitz mapping λ : n 𝒰 normal-: 𝜆 normal-→ superscript 𝑛 𝒰 \lambda:\mathbb{R}^{n}\rightarrow\mathcal{U} italic_λ : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT → caligraphic_U such that

x ˙ = f ( x , λ ( x ) ) ˙ 𝑥 𝑓 𝑥 𝜆 𝑥 \dot{x}=f(x,\lambda(x)) ˙ start_ARG italic_x end_ARG = italic_f ( italic_x , italic_λ ( italic_x ) ) (2)

is locally (resp. globally) asymptotically stable at the origin.

Definition 2 (Dynamic stabilizability) .

System ( 1 ) is said to be locally (resp. globally) asymptotically stabilizable by a dynamic state feedback if there exist f ^ : n × n × 𝒰 n normal-: normal-^ 𝑓 normal-→ superscript 𝑛 superscript 𝑛 𝒰 superscript 𝑛 \hat{f}:\mathbb{R}^{n}\times\mathbb{R}^{n}\times\mathcal{U}\to\mathbb{R}^{n} ^ start_ARG italic_f end_ARG : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × caligraphic_U → blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT such that f ^ ( , , u ) C 1 ( n × n , n ) normal-^ 𝑓 normal-⋅ normal-⋅ 𝑢 superscript 𝐶 1 superscript 𝑛 superscript 𝑛 superscript 𝑛 \hat{f}(\cdot,\cdot,u)\in C^{1}(\mathbb{R}^{n}\times\mathbb{R}^{n},\mathbb{R}^% {n}) ^ start_ARG italic_f end_ARG ( ⋅ , ⋅ , italic_u ) ∈ italic_C start_POSTSUPERSCRIPT 1 end_POSTSUPERSCRIPT ( blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT , blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT ) for all u 𝒰 𝑢 𝒰 u\in\mathcal{U} italic_u ∈ caligraphic_U ,

f ^ ( x , x ^ ) C 0 ( n × n × 𝒰 , n ) ^ 𝑓 𝑥 ^ 𝑥 superscript 𝐶 0 superscript 𝑛 superscript 𝑛 𝒰 superscript 𝑛 \frac{\partial\hat{f}}{\partial(x,\hat{x})}\in C^{0}(\mathbb{R}^{n}\times% \mathbb{R}^{n}\times\mathcal{U},\mathbb{R}^{n}) divide start_ARG ∂ ^ start_ARG italic_f end_ARG end_ARG start_ARG ∂ ( italic_x , ^ start_ARG italic_x end_ARG ) end_ARG ∈ italic_C start_POSTSUPERSCRIPT 0 end_POSTSUPERSCRIPT ( blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × caligraphic_U , blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT )

and f ^ ( x , x ^ , ) normal-^ 𝑓 𝑥 normal-^ 𝑥 normal-⋅ \hat{f}(x,\hat{x},\cdot) ^ start_ARG italic_f end_ARG ( italic_x , ^ start_ARG italic_x end_ARG , ⋅ ) is locally Lipschitz for all ( x , x ^ ) n × n 𝑥 normal-^ 𝑥 superscript 𝑛 superscript 𝑛 (x,\hat{x})\in\mathbb{R}^{n}\times\mathbb{R}^{n} ( italic_x , ^ start_ARG italic_x end_ARG ) ∈ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT × blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT and a locally Lipschitz mapping λ : n 𝒰 normal-: 𝜆 normal-→ superscript 𝑛 𝒰 \lambda:~{}\mathbb{R}^{n}\rightarrow\mathcal{U} italic_λ : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT → caligraphic_U such that

x ˙ = f ( x , λ ( x ^ ) ) , x ^ ˙ = f ^ ( x , x ^ , λ ( x ^ ) ) formulae-sequence ˙ 𝑥 𝑓 𝑥 𝜆 ^ 𝑥 ˙ ^ 𝑥 ^ 𝑓 𝑥 ^ 𝑥 𝜆 ^ 𝑥 \dot{x}=f(x,\lambda(\hat{x})),\quad\dot{\hat{x}}=\hat{f}(x,\hat{x},\lambda(% \hat{x})) ˙ start_ARG italic_x end_ARG = italic_f ( italic_x , italic_λ ( ^ start_ARG italic_x end_ARG ) ) , ˙ start_ARG ^ start_ARG italic_x end_ARG end_ARG = ^ start_ARG italic_f end_ARG ( italic_x , ^ start_ARG italic_x end_ARG , italic_λ ( ^ start_ARG italic_x end_ARG ) ) (3)

is locally (resp. globally) asymptotically stable at the origin.


Definition 5 .

(PDM) Following [ 6 , Definition 4] we refer to ( 36 ) as the Payoff Dynamics Model (PDM), and assume that it recovers the static model p = F ( x ) 𝑝 𝐹 𝑥 p=F(x) italic_p = italic_F ( italic_x ) in steady-state, that is,

f ( q , x ) = 0 h ( q , x ) = F ( x ) . formulae-sequence 𝑓 𝑞 𝑥 0 𝑞 𝑥 𝐹 𝑥 f(q,x)=0\quad\Rightarrow\quad h(q,x)=F(x). italic_f ( italic_q , italic_x ) = 0 ⇒ italic_h ( italic_q , italic_x ) = italic_F ( italic_x ) . (37)

Definition 1 (Memory equivalence) .

Two memories m 𝑚 m italic_m and s 𝑠 s italic_s are equivalent up to level normal-ℓ \ell roman_ℓ , written m s subscript similar-to normal-ℓ 𝑚 𝑠 m\mathrel{\sim_{\ell}}s italic_m start_RELOP ∼ start_POSTSUBSCRIPT roman_ℓ end_POSTSUBSCRIPT end_RELOP italic_s , if 𝖽𝗈𝗆 ( m ) = 𝖽𝗈𝗆 ( s ) 𝖽𝗈𝗆 𝑚 𝖽𝗈𝗆 𝑠 \mathsf{dom}(m)=\mathsf{dom}(s) sansserif_dom ( italic_m ) = sansserif_dom ( italic_s ) and it holds that for all x 𝖽𝗈𝗆 ( m ) 𝑥 𝖽𝗈𝗆 𝑚 x\in\mathsf{dom}(m) italic_x ∈ sansserif_dom ( italic_m ) ,

𝑙𝑒𝑣 ( x ) m ( x ) = s ( x ) square-image-of-or-equals 𝑙𝑒𝑣 𝑥 𝑚 𝑥 𝑠 𝑥 \mathit{lev}(x)\sqsubseteq\ell\implies m(x)=s(x) italic_lev ( italic_x ) ⊑ roman_ℓ ⟹ italic_m ( italic_x ) = italic_s ( italic_x )

Definition 3.3.1 .

The category Rep ( H t , k ( ν ) ) Rep subscript 𝐻 𝑡 𝑘 𝜈 \textrm{Rep}(H_{t,k}(\nu)) Rep ( italic_H start_POSTSUBSCRIPT italic_t , italic_k end_POSTSUBSCRIPT ( italic_ν ) ) is defined as follows. The objects are given by triples ( M , x , y ) 𝑀 𝑥 𝑦 (M,x,y) ( italic_M , italic_x , italic_y ) , where M 𝑀 M italic_M is an ind-object of Rep ( S ν ) Rep subscript 𝑆 𝜈 \textrm{Rep}(S_{\nu}) Rep ( italic_S start_POSTSUBSCRIPT italic_ν end_POSTSUBSCRIPT ) , x 𝑥 x italic_x is a map x : 𝔥 * M M : 𝑥 tensor-product superscript 𝔥 𝑀 𝑀 x:\mathfrak{h}^{*}\otimes M\to M italic_x : fraktur_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ italic_M → italic_M and y 𝑦 y italic_y a map y : 𝔥 M M : 𝑦 tensor-product 𝔥 𝑀 𝑀 y:\mathfrak{h}\otimes M\to M italic_y : fraktur_h ⊗ italic_M → italic_M , both of which are morphisms in IND ( Rep ( S ν ) ) IND Rep subscript 𝑆 𝜈 \textrm{IND}(\textrm{Rep}(S_{\nu})) IND ( Rep ( italic_S start_POSTSUBSCRIPT italic_ν end_POSTSUBSCRIPT ) ) . They also satisfy the following conditions:

x ( 1 x ) - x ( 1 x ) ( σ 1 ) = 0 , 𝑥 tensor-product 1 𝑥 𝑥 tensor-product 1 𝑥 tensor-product 𝜎 1 0 x\circ(1\otimes x)-x\circ(1\otimes x)\circ(\sigma\otimes 1)=0, italic_x ∘ ( 1 ⊗ italic_x ) - italic_x ∘ ( 1 ⊗ italic_x ) ∘ ( italic_σ ⊗ 1 ) = 0 ,

as a map from 𝔥 * 𝔥 * M tensor-product superscript 𝔥 superscript 𝔥 𝑀 \mathfrak{h}^{*}\otimes\mathfrak{h}^{*}\otimes M fraktur_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ fraktur_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ italic_M to M 𝑀 M italic_M ;

y ( 1 y ) - y ( 1 y ) ( σ 1 ) = 0 , 𝑦 tensor-product 1 𝑦 𝑦 tensor-product 1 𝑦 tensor-product 𝜎 1 0 y\circ(1\otimes y)-y\circ(1\otimes y)\circ(\sigma\otimes 1)=0, italic_y ∘ ( 1 ⊗ italic_y ) - italic_y ∘ ( 1 ⊗ italic_y ) ∘ ( italic_σ ⊗ 1 ) = 0 ,

as a map from 𝔥 𝔥 M tensor-product 𝔥 𝔥 𝑀 \mathfrak{h}\otimes\mathfrak{h}\otimes M fraktur_h ⊗ fraktur_h ⊗ italic_M to M 𝑀 M italic_M ;

y ( 1 x ) - x ( 1 y ) ( σ 1 ) = t ev 𝔥 1 - k ( ev 𝔥 1 ) ( Ω 3 - Ω 1 , 3 ) , 𝑦 tensor-product 1 𝑥 𝑥 tensor-product 1 𝑦 tensor-product 𝜎 1 tensor-product 𝑡 subscript ev 𝔥 1 𝑘 tensor-product subscript ev 𝔥 1 superscript Ω 3 superscript Ω 1 3 y\circ(1\otimes x)-x\circ(1\otimes y)\circ(\sigma\otimes 1)=t\cdot{\rm ev}_{% \mathfrak{h}}\otimes 1-k\cdot({\rm ev}_{\mathfrak{h}}\otimes 1)\circ(\Omega^{3% }-\Omega^{1,3}), italic_y ∘ ( 1 ⊗ italic_x ) - italic_x ∘ ( 1 ⊗ italic_y ) ∘ ( italic_σ ⊗ 1 ) = italic_t ⋅ roman_ev start_POSTSUBSCRIPT fraktur_h end_POSTSUBSCRIPT ⊗ 1 - italic_k ⋅ ( roman_ev start_POSTSUBSCRIPT fraktur_h end_POSTSUBSCRIPT ⊗ 1 ) ∘ ( roman_Ω start_POSTSUPERSCRIPT 3 end_POSTSUPERSCRIPT - roman_Ω start_POSTSUPERSCRIPT 1 , 3 end_POSTSUPERSCRIPT ) ,

as a map from 𝔥 𝔥 * M tensor-product 𝔥 superscript 𝔥 𝑀 \mathfrak{h}\otimes\mathfrak{h}^{*}\otimes M fraktur_h ⊗ fraktur_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ italic_M to M 𝑀 M italic_M , where Ω Ω \Omega roman_Ω is a central element from Definition 3.2.7 , and indices indicate the spaces on which Ω Ω \Omega roman_Ω acts in the tensor product 𝔥 𝔥 * M tensor-product 𝔥 superscript 𝔥 𝑀 \mathfrak{h}\otimes\mathfrak{h}^{*}\otimes M fraktur_h ⊗ fraktur_h start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ⊗ italic_M .

The morphisms of Rep ( H t , k ( ν ) ) Rep subscript 𝐻 𝑡 𝑘 𝜈 \textrm{Rep}(H_{t,k}(\nu)) Rep ( italic_H start_POSTSUBSCRIPT italic_t , italic_k end_POSTSUBSCRIPT ( italic_ν ) ) are the morphisms of IND ( Rep ( S ν ) ) IND Rep subscript 𝑆 𝜈 \textrm{IND}(\textrm{Rep}(S_{\nu})) IND ( Rep ( italic_S start_POSTSUBSCRIPT italic_ν end_POSTSUBSCRIPT ) ) which commute with the action-maps x 𝑥 x italic_x and y 𝑦 y italic_y .

Also by Rep ext ( H t , k ( ν ) ) superscript Rep ext subscript 𝐻 𝑡 𝑘 𝜈 \textrm{Rep}^{\rm ext}(H_{t,k}(\nu)) Rep start_POSTSUPERSCRIPT roman_ext end_POSTSUPERSCRIPT ( italic_H start_POSTSUBSCRIPT italic_t , italic_k end_POSTSUBSCRIPT ( italic_ν ) ) denote the similar category constructed over Rep ext ( S ν ) superscript Rep ext subscript 𝑆 𝜈 \textrm{Rep}^{\rm ext}(S_{\nu}) Rep start_POSTSUPERSCRIPT roman_ext end_POSTSUPERSCRIPT ( italic_S start_POSTSUBSCRIPT italic_ν end_POSTSUBSCRIPT ) .


Definition

[ 8 ] Let μ 𝜇 \mu\in\mathcal{M} italic_μ ∈ caligraphic_M . A continuous function f : X : 𝑓 𝑋 f:\mathbb{R}\longrightarrow X italic_f : blackboard_R ⟶ italic_X is said to be μ 𝜇 \mu italic_μ -pseudo almost automorphic if f 𝑓 f italic_f is written in the form:

f = g + φ , 𝑓 𝑔 𝜑 f=g+\varphi, italic_f = italic_g + italic_φ ,

where g A A ( , X ) 𝑔 𝐴 𝐴 𝑋 g\in AA(\mathbb{R},X) italic_g ∈ italic_A italic_A ( blackboard_R , italic_X ) and φ ( , X , μ ) . 𝜑 𝑋 𝜇 \varphi\in\mathcal{E}(\mathbb{R},X,\mu). italic_φ ∈ caligraphic_E ( blackboard_R , italic_X , italic_μ ) .
The space of all such functions is denoted by P A A ( , X , μ ) . 𝑃 𝐴 𝐴 𝑋 𝜇 PAA(\mathbb{R},X,\mu). italic_P italic_A italic_A ( blackboard_R , italic_X , italic_μ ) . {}_{\blacksquare} start_FLOATSUBSCRIPT ■ end_FLOATSUBSCRIPT

Definition

[ 4 ] Let μ 𝜇 \mu\in\mathcal{M} italic_μ ∈ caligraphic_M and f : × X Y : 𝑓 𝑋 𝑌 f:\mathbb{R}\times X\longrightarrow Y italic_f : blackboard_R × italic_X ⟶ italic_Y be such that f ( , x ) B S p ( , Y ) 𝑓 𝑥 𝐵 superscript 𝑆 𝑝 𝑌 f(\cdot,x)\in BS^{p}(\mathbb{R},Y) italic_f ( ⋅ , italic_x ) ∈ italic_B italic_S start_POSTSUPERSCRIPT italic_p end_POSTSUPERSCRIPT ( blackboard_R , italic_Y ) for each x X 𝑥 𝑋 x\in X italic_x ∈ italic_X . The function f 𝑓 f italic_f is μ 𝜇 \mu italic_μ - S p superscript 𝑆 𝑝 S^{p} italic_S start_POSTSUPERSCRIPT italic_p end_POSTSUPERSCRIPT -almost automorphic if f 𝑓 f italic_f is written as:

f = g + φ , 𝑓 𝑔 𝜑 f=g+\varphi, italic_f = italic_g + italic_φ ,

where g A A S p U ( × X , Y ) 𝑔 𝐴 𝐴 superscript 𝑆 𝑝 𝑈 𝑋 𝑌 g\in AAS^{p}U(\mathbb{R}\times X,Y) italic_g ∈ italic_A italic_A italic_S start_POSTSUPERSCRIPT italic_p end_POSTSUPERSCRIPT italic_U ( blackboard_R × italic_X , italic_Y ) , and φ p U ( × X , Y , μ ) . 𝜑 superscript 𝑝 𝑈 𝑋 𝑌 𝜇 \varphi\in\mathcal{E}^{p}U(\mathbb{R}\times X,Y,\mu). italic_φ ∈ caligraphic_E start_POSTSUPERSCRIPT italic_p end_POSTSUPERSCRIPT italic_U ( blackboard_R × italic_X , italic_Y , italic_μ ) .
The space of all such functions is denoted P A A S p U ( , X , μ ) . 𝑃 𝐴 𝐴 superscript 𝑆 𝑝 𝑈 𝑋 𝜇 PAAS^{p}U(\mathbb{R},X,\mu). italic_P italic_A italic_A italic_S start_POSTSUPERSCRIPT italic_p end_POSTSUPERSCRIPT italic_U ( blackboard_R , italic_X , italic_μ ) . {}_{\blacksquare} start_FLOATSUBSCRIPT ■ end_FLOATSUBSCRIPT


Definition 5.2 ( [ Ete18 , §5] ) .

A j 𝑗 j italic_j -derivation on the field of complex numbers is a derivation δ : : 𝛿 \delta:\operatorname{\mathbb{C}}\operatorname{\rightarrow}\operatorname{% \mathbb{C}} italic_δ : blackboard_C → blackboard_C such that for any z 𝑧 z\in\operatorname{\mathbb{H}} italic_z ∈ blackboard_H we have

δ j ( z ) = j ( z ) δ ( z ) , δ j ( z ) = j ′′ ( z ) δ ( z ) , δ j ′′ ( z ) = j ′′′ ( z ) δ ( z ) . formulae-sequence 𝛿 𝑗 𝑧 superscript 𝑗 𝑧 𝛿 𝑧 formulae-sequence 𝛿 superscript 𝑗 𝑧 superscript 𝑗 ′′ 𝑧 𝛿 𝑧 𝛿 superscript 𝑗 ′′ 𝑧 superscript 𝑗 ′′′ 𝑧 𝛿 𝑧 \delta j(z)=j^{\prime}(z)\delta(z),~{}\delta j^{\prime}(z)=j^{\prime\prime}(z)% \delta(z),~{}\delta j^{\prime\prime}(z)=j^{\prime\prime\prime}(z)\delta(z). italic_δ italic_j ( italic_z ) = italic_j start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_z ) italic_δ ( italic_z ) , italic_δ italic_j start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_z ) = italic_j start_POSTSUPERSCRIPT ′ ′ end_POSTSUPERSCRIPT ( italic_z ) italic_δ ( italic_z ) , italic_δ italic_j start_POSTSUPERSCRIPT ′ ′ end_POSTSUPERSCRIPT ( italic_z ) = italic_j start_POSTSUPERSCRIPT ′ ′ ′ end_POSTSUPERSCRIPT ( italic_z ) italic_δ ( italic_z ) .

The space of j 𝑗 j italic_j -derivations is denoted by j Der ( ) 𝑗 Der j\rm{Der}(\operatorname{\mathbb{C}}) italic_j roman_Der ( blackboard_C ) .


Definition 4.4 .

Let χ 𝜒 \chi italic_χ be a Dirichlet character mod q 𝑞 q italic_q . An arithmetical function f 𝑓 f italic_f is said to be separable with respect to χ 𝜒 \chi italic_χ if

f ( n a ) = f ( n ) χ ( a ) 𝑓 𝑛 𝑎 𝑓 𝑛 𝜒 𝑎 f(na)=f(n)\chi(a) italic_f ( italic_n italic_a ) = italic_f ( italic_n ) italic_χ ( italic_a )

for any positive integers n , a 𝑛 𝑎 n,a italic_n , italic_a with gcd ( a , q ) = 1 𝑎 𝑞 1 \gcd(a,q)=1 roman_gcd ( italic_a , italic_q ) = 1 .


Definition 3.2 .

( 𝒩 ( n , ω , ε ) 𝒩 𝑛 𝜔 𝜀 \mathcal{N}(n,\omega,\varepsilon) caligraphic_N ( italic_n , italic_ω , italic_ε ) -NS sets) Let ω > 0 𝜔 0 \omega>0 italic_ω > 0 and 0 ε < 1 0 𝜀 1 0\leq\varepsilon<1 0 ≤ italic_ε < 1 . An open set Ω 0 n subscript normal-Ω 0 superscript 𝑛 \Omega_{0}\subset\mathbb{R}^{n} roman_Ω start_POSTSUBSCRIPT 0 end_POSTSUBSCRIPT ⊂ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT is said 𝒩 ( n , ω , ε ) 𝒩 𝑛 𝜔 𝜀 \mathcal{N}(n,\omega,\varepsilon) caligraphic_N ( italic_n , italic_ω , italic_ε ) -NS set if there exists a function v 𝒩 ( n , ε ) 𝑣 𝒩 𝑛 𝜀 v\in\mathcal{N}(n,\varepsilon) italic_v ∈ caligraphic_N ( italic_n , italic_ε ) such that, up to a translation, its boundary can be represented in polar coordinates as

r ( ξ ) = ρ ( 1 + v ( ξ ) ) [ 0 , + ] 𝑟 𝜉 𝜌 1 𝑣 𝜉 0 r(\xi)=\rho(1+v(\xi))\in[0,+\infty] italic_r ( italic_ξ ) = italic_ρ ( 1 + italic_v ( italic_ξ ) ) ∈ [ 0 , + ∞ ] (3.1)

where ξ 𝕊 n - 1 𝜉 superscript 𝕊 𝑛 1 \xi\in\mathbb{S}^{n-1} italic_ξ ∈ blackboard_S start_POSTSUPERSCRIPT italic_n - 1 end_POSTSUPERSCRIPT and ρ = ( ω / ω n ) 1 n 𝜌 superscript 𝜔 subscript 𝜔 𝑛 1 𝑛 \rho=(\omega/\omega_{n})^{\frac{1}{n}} italic_ρ = ( italic_ω / italic_ω start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT ) start_POSTSUPERSCRIPT divide start_ARG 1 end_ARG start_ARG italic_n end_ARG end_POSTSUPERSCRIPT is the radius of the ball having the same measure of Ω normal-Ω \Omega roman_Ω .


Definition 4.1 ().

Let 𝒙 n 𝒙 superscript 𝑛 {\bm{x}}\in\mathbb{R}^{n} bold_italic_x ∈ blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT be a real-valued vector and π S n 𝜋 subscript 𝑆 𝑛 \pi\in S_{n} italic_π ∈ italic_S start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT be a permutation of n 𝑛 n italic_n elements. A function f : n n : 𝑓 superscript 𝑛 superscript 𝑛 f:\mathbb{R}^{n}\rightarrow\mathbb{R}^{n} italic_f : blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT → blackboard_R start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT is called permutation-equivariant iff

f ( π ( 𝒙 ) ) = π ( f ( 𝒙 ) ) . 𝑓 𝜋 𝒙 𝜋 𝑓 𝒙 f(\pi({\bm{x}}))=\pi(f({\bm{x}})). italic_f ( italic_π ( bold_italic_x ) ) = italic_π ( italic_f ( bold_italic_x ) ) .

That is, a function is permutation-equivariant if it commutes with any permutation of the input elements.

It is a trivial observation that the self-attention operation is permutation-equivariant.


Definition 2.11 .

Let N 𝑁 N italic_N and H 𝐻 H italic_H be inverse semigroups and let α : H × N N : 𝛼 𝐻 𝑁 𝑁 \alpha\colon H\times N\to N italic_α : italic_H × italic_N → italic_N be a function which we write as α ( h , n ) = h n 𝛼 𝑛 𝑛 \alpha(h,n)=h\cdot n italic_α ( italic_h , italic_n ) = italic_h ⋅ italic_n . Then α 𝛼 \alpha italic_α is an action of inverse semigroups if the following conditions are satisfied for all h , h H superscript 𝐻 h,h^{\prime}\in H italic_h , italic_h start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ∈ italic_H and n , n N 𝑛 superscript 𝑛 𝑁 n,n^{\prime}\in N italic_n , italic_n start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ∈ italic_N .

  1. (1)

    h ( n n ) = ( h n ) ( h n ) 𝑛 superscript 𝑛 𝑛 superscript 𝑛 h\cdot(nn^{\prime})=(h\cdot n)(h\cdot n^{\prime}) italic_h ⋅ ( italic_n italic_n start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) = ( italic_h ⋅ italic_n ) ( italic_h ⋅ italic_n start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) ,

  2. (2)

    h h n = h ( h n ) superscript 𝑛 superscript 𝑛 hh^{\prime}\cdot n=h\cdot(h^{\prime}\cdot n) italic_h italic_h start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ⋅ italic_n = italic_h ⋅ ( italic_h start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ⋅ italic_n ) .

Definition 3.1 .

Let N 𝑁 N italic_N and H 𝐻 H italic_H be inverse monoids and let α : H × N N : 𝛼 𝐻 𝑁 𝑁 \alpha\colon H\times N\to N italic_α : italic_H × italic_N → italic_N be a function with application written α ( h , n ) = h n 𝛼 𝑛 𝑛 \alpha(h,n)=h\cdot n italic_α ( italic_h , italic_n ) = italic_h ⋅ italic_n . Then α 𝛼 \alpha italic_α is an action of inverse monoids if it is an action of inverse semigroups and satisifies that for all n N 𝑛 𝑁 n\in N italic_n ∈ italic_N

1 n = n . 1 𝑛 𝑛 1\cdot n=n. 1 ⋅ italic_n = italic_n .

Definition 2.1 .

[ 27 ] A Hom-Lie algebra ( L , α ) 𝐿 𝛼 (L,\alpha) ( italic_L , italic_α ) is an 𝔽 𝔽 {\mathbb{F}} blackboard_F -vector space L 𝐿 L italic_L endowed with a bilinear map [ - , - ] : L × L L : 𝐿 𝐿 𝐿 [-,-]:L\times L\rightarrow L [ - , - ] : italic_L × italic_L → italic_L and a linear homomorphism α : L L : 𝛼 𝐿 𝐿 \alpha:L\rightarrow L italic_α : italic_L → italic_L satisfying that for any x , y , z L 𝑥 𝑦 𝑧 𝐿 x,y,z\in L italic_x , italic_y , italic_z ∈ italic_L ,

[ x , y ] = - [ y , x ] , (skew-symmetry) 𝑥 𝑦 𝑦 𝑥 (skew-symmetry) \displaystyle[x,y]=-[y,x],~{}~{}\text{(skew-symmetry)} [ italic_x , italic_y ] = - [ italic_y , italic_x ] , (skew-symmetry)
] + [ α ( y ) , [ z , x ] ] + [ α ( z ) , [ x , y ] ] = 0 . (Hom-Jacobi identity) fragments ] [ α fragments ( y ) , fragments [ z , x ] ] [ α fragments ( z ) , fragments [ x , y ] ] 0 . (Hom-Jacobi identity) \displaystyle]+[\alpha(y),[z,x]]+[\alpha(z),[x,y]]=0.~{}~{}\text{(Hom-Jacobi % identity)} ] + [ italic_α ( italic_y ) , [ italic_z , italic_x ] ] + [ italic_α ( italic_z ) , [ italic_x , italic_y ] ] = 0 . (Hom-Jacobi identity)

In particular, a Hom-Lie algebra ( L , α ) 𝐿 𝛼 (L,\alpha) ( italic_L , italic_α ) is called multiplicative , if α 𝛼 \alpha italic_α is an algebra homomorphism, i.e., α ( [ x , y ] ) = [ α ( x ) , α ( y ) ] 𝛼 𝑥 𝑦 𝛼 𝑥 𝛼 𝑦 \alpha([x,y])=[\alpha(x),\alpha(y)] italic_α ( [ italic_x , italic_y ] ) = [ italic_α ( italic_x ) , italic_α ( italic_y ) ] , for all x , y L 𝑥 𝑦 𝐿 x,y\in L italic_x , italic_y ∈ italic_L .

Definition 2.2 .

[ 27 , 34 ] For a Hom-Lie algebra ( L , α ) 𝐿 𝛼 (L,\alpha) ( italic_L , italic_α ) , a triple ( V , ρ , β ) 𝑉 𝜌 𝛽 (V,\rho,\beta) ( italic_V , italic_ρ , italic_β ) consisting of a vector space V 𝑉 V italic_V , a linear map ρ : L End ( V ) : 𝜌 𝐿 End 𝑉 \rho:L\rightarrow{\rm End}(V) italic_ρ : italic_L → roman_End ( italic_V ) and β End ( V ) 𝛽 End 𝑉 \beta\in{\rm End}(V) italic_β ∈ roman_End ( italic_V ) is said to be a representation of ( L , α ) 𝐿 𝛼 (L,\alpha) ( italic_L , italic_α ) or an ( L , α ) 𝐿 𝛼 (L,\alpha) ( italic_L , italic_α ) - module , if for all x , y L 𝑥 𝑦 𝐿 x,y\in L italic_x , italic_y ∈ italic_L , the following equalities are satisfied

(2.1) β ρ ( x ) = ρ ( α ( x ) ) β , 𝛽 𝜌 𝑥 𝜌 𝛼 𝑥 𝛽 \displaystyle\beta\circ\rho(x)=\rho(\alpha(x))\circ\beta, italic_β ∘ italic_ρ ( italic_x ) = italic_ρ ( italic_α ( italic_x ) ) ∘ italic_β ,
(2.2) ρ ( [ x , y ] ) β = ρ ( α ( x ) ) ρ ( y ) - ρ ( α ( y ) ) ρ ( x ) . 𝜌 𝑥 𝑦 𝛽 𝜌 𝛼 𝑥 𝜌 𝑦 𝜌 𝛼 𝑦 𝜌 𝑥 \displaystyle\rho([x,y])\circ\beta=\rho(\alpha(x))\circ\rho(y)-\rho(\alpha(y))% \circ\rho(x). italic_ρ ( [ italic_x , italic_y ] ) ∘ italic_β = italic_ρ ( italic_α ( italic_x ) ) ∘ italic_ρ ( italic_y ) - italic_ρ ( italic_α ( italic_y ) ) ∘ italic_ρ ( italic_x ) .

For brevity of notation, we usually put x v = ρ ( x ) ( v ) , x L , v V formulae-sequence 𝑥 𝑣 𝜌 𝑥 𝑣 formulae-sequence for-all 𝑥 𝐿 𝑣 𝑉 xv=\rho(x)(v),~{}\forall~{}x\in L,v\in V italic_x italic_v = italic_ρ ( italic_x ) ( italic_v ) , ∀ italic_x ∈ italic_L , italic_v ∈ italic_V , just like the case in Lie algebras. A subspace W 𝑊 W italic_W of V 𝑉 V italic_V is called a submodule of ( V , ρ , β ) 𝑉 𝜌 𝛽 (V,\rho,\beta) ( italic_V , italic_ρ , italic_β ) if W 𝑊 W italic_W is both β 𝛽 \beta italic_β -invariant and L 𝐿 L italic_L -invariant, i.e., β ( W ) W 𝛽 𝑊 𝑊 \beta(W)\subset W italic_β ( italic_W ) ⊂ italic_W and x W W , x L formulae-sequence 𝑥 𝑊 𝑊 for-all 𝑥 𝐿 xW\subset W,~{}\forall~{}x\in L italic_x italic_W ⊂ italic_W , ∀ italic_x ∈ italic_L .