Definition \thedefinition .

Given a real constant k 𝑘 k italic_k , we let 𝘀 k subscript 𝘀 𝑘 \textbf{{s}}_{k} s start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT denote the solution to the ordinary differential equation

{ ϕ ′′ + k ϕ = 0 , ϕ ( 0 ) = 0 , ϕ ( 0 ) = 1 fragments { superscript italic-ϕ ′′ 𝑘 italic-ϕ absent 0 italic-ϕ 0 0 superscript italic-ϕ 0 1 \left\{\begin{aligned} \displaystyle\phi^{\prime\prime}+k\phi&\displaystyle=0,% \\ \displaystyle\phi(0)=0,&\displaystyle\phi^{\prime}(0)=1\end{aligned}\right. { start_ROW start_CELL italic_ϕ start_POSTSUPERSCRIPT ′ ′ end_POSTSUPERSCRIPT + italic_k italic_ϕ end_CELL start_CELL = 0 , end_CELL end_ROW start_ROW start_CELL italic_ϕ ( 0 ) = 0 , end_CELL start_CELL italic_ϕ start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( 0 ) = 1 end_CELL end_ROW (1.1)

Setting 𝗰 k ( t ) = 𝘀 k ( t ) subscript 𝗰 𝑘 𝑡 subscript superscript 𝘀 normal-′ 𝑘 𝑡 \textbf{{c}}_{k}(t)=\textbf{{s}}^{\prime}_{k}(t) c start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( italic_t ) = s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( italic_t ) , we clearly get 𝗰 k ( t ) = - k 𝘀 k ( t ) subscript superscript 𝗰 normal-′ 𝑘 𝑡 𝑘 subscript 𝘀 𝑘 𝑡 \textbf{{c}}^{\prime}_{k}(t)=-k\textbf{{s}}_{k}(t) c start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( italic_t ) = - italic_k s start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( italic_t ) and 𝗰 k subscript 𝗰 𝑘 \textbf{{c}}_{k} c start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT satisfies 𝗰 k ′′ + k 𝗰 k = 0 superscript subscript 𝗰 𝑘 normal-′′ 𝑘 subscript 𝗰 𝑘 0 \textbf{{c}}_{k}^{\prime\prime}+k\textbf{{c}}_{k}=0 c start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT start_POSTSUPERSCRIPT ′ ′ end_POSTSUPERSCRIPT + italic_k c start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT = 0 , with initial condition 𝗰 k ( 0 ) = 1 , 𝗰 k ( 0 ) = 0 formulae-sequence subscript 𝗰 𝑘 0 1 subscript superscript 𝗰 normal-′ 𝑘 0 0 \textbf{{c}}_{k}(0)=1,\textbf{{c}}^{\prime}_{k}(0)=0 c start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( 0 ) = 1 , c start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT start_POSTSUBSCRIPT italic_k end_POSTSUBSCRIPT ( 0 ) = 0 .


Definition 1 (PEL) .

PEL is the class of functions that can be described by

f ( n ) = 2 p ( n ) , fragments f fragments ( n ) superscript 2 𝑝 𝑛 , f(n)={}^{p(n)}2, italic_f ( italic_n ) = start_FLOATSUPERSCRIPT italic_p ( italic_n ) end_FLOATSUPERSCRIPT 2 ,

where p 𝑝 p italic_p can be any polynomial and the left superscript denotes tetration.

The complexity class PEL is the class of languages recognisable by a TM in time f ( n ) 𝑓 𝑛 f(n) italic_f ( italic_n ) , where f ( n ) 𝑓 𝑛 f(n) italic_f ( italic_n ) is in PEL and n 𝑛 n italic_n is the bit-length of the input. Equivalently, PEL is the class of languages recognisable by a TM working on a tape of size f ( n ) 𝑓 𝑛 f(n) italic_f ( italic_n ) , where f ( n ) 𝑓 𝑛 f(n) italic_f ( italic_n ) is in PEL.

PEL can therefore also be described as either PEL-TIME or PEL-SPACE.


Definition 2.3 .

Two factors of automorphy α 𝛼 \alpha italic_α and β 𝛽 \beta italic_β are called equivalent if there is a holomorphic function h : U ~ * normal-: normal-→ normal-~ 𝑈 superscript h:\widetilde{U}\rightarrow\mathbb{C}^{*} italic_h : ~ start_ARG italic_U end_ARG → blackboard_C start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT satisfying

β ( λ , z ) = h ( z + λ ) α ( λ , z ) h - 1 ( z ) . 𝛽 𝜆 𝑧 𝑧 𝜆 𝛼 𝜆 𝑧 superscript 1 𝑧 \beta(\lambda,z)=h(z+\lambda)\alpha(\lambda,z)h^{-1}(z). italic_β ( italic_λ , italic_z ) = italic_h ( italic_z + italic_λ ) italic_α ( italic_λ , italic_z ) italic_h start_POSTSUPERSCRIPT - 1 end_POSTSUPERSCRIPT ( italic_z ) .

Two summands of automorphy are called equivalent if the induced factors of automorphy are equivalent.


Definition 3.14

A map f : 3 3 normal-: 𝑓 normal-⟶ superscript 3 superscript 3 f:{\mathbb{R}}^{3}\longrightarrow{\mathbb{R}}^{3} italic_f : blackboard_R start_POSTSUPERSCRIPT 3 end_POSTSUPERSCRIPT ⟶ blackboard_R start_POSTSUPERSCRIPT 3 end_POSTSUPERSCRIPT such that

f ( p ) = f ( - p ) 𝑓 𝑝 𝑓 𝑝 f(p)=f(-p) italic_f ( italic_p ) = italic_f ( - italic_p )

is said to have the antipodal property.


Definition 10

A reduction ρ 𝜌 \rho italic_ρ between two chain complexes C = ( C n , d n ) n subscript 𝐶 normal-∗ subscript subscript 𝐶 𝑛 subscript 𝑑 𝑛 𝑛 C_{\ast}=(C_{n},d_{n})_{n\in\mathbb{Z}} italic_C start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT = ( italic_C start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT , italic_d start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT ) start_POSTSUBSCRIPT italic_n ∈ blackboard_Z end_POSTSUBSCRIPT and D = ( D n , d ^ n ) n subscript 𝐷 normal-∗ subscript subscript 𝐷 𝑛 subscript normal-^ 𝑑 𝑛 𝑛 D_{\ast}=(D_{n},\hat{d}_{n})_{n\in\mathbb{Z}} italic_D start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT = ( italic_D start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT , ^ start_ARG italic_d end_ARG start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT ) start_POSTSUBSCRIPT italic_n ∈ blackboard_Z end_POSTSUBSCRIPT , denoted by ρ : C D normal-: 𝜌 subscript 𝐶 normal-∗ subscript 𝐷 normal-∗ \rho:C_{\ast}\mbox{\,$\Rightarrow\hskip-9.0pt\Rightarrow$\,}D_{\ast} italic_ρ : italic_C start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT ⇒ ⇒ italic_D start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT , is a triple ρ = ( f , g , h ) 𝜌 𝑓 𝑔 \rho=(f,g,h) italic_ρ = ( italic_f , italic_g , italic_h ) where f : C D normal-: 𝑓 normal-→ subscript 𝐶 normal-∗ subscript 𝐷 normal-∗ f:C_{\ast}\rightarrow D_{\ast} italic_f : italic_C start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT → italic_D start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT and g : D C normal-: 𝑔 normal-→ subscript 𝐷 normal-∗ subscript 𝐶 normal-∗ g:D_{\ast}\rightarrow C_{\ast} italic_g : italic_D start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT → italic_C start_POSTSUBSCRIPT ∗ end_POSTSUBSCRIPT are chain complex morphisms, h = { h n : C n C n + 1 } n subscript conditional-set subscript 𝑛 normal-→ subscript 𝐶 𝑛 subscript 𝐶 𝑛 1 𝑛 h=\{h_{n}:C_{n}\rightarrow C_{n+1}\}_{n\in\mathbb{Z}} italic_h = { italic_h start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT : italic_C start_POSTSUBSCRIPT italic_n end_POSTSUBSCRIPT → italic_C start_POSTSUBSCRIPT italic_n + 1 end_POSTSUBSCRIPT } start_POSTSUBSCRIPT italic_n ∈ blackboard_Z end_POSTSUBSCRIPT is a family of module morphism, and the following properties are satisfied:

  1. 1)

    f g = i d 𝑓 𝑔 𝑖 𝑑 f\circ g=id italic_f ∘ italic_g = italic_i italic_d ;

  2. 2)

    g f + d h + h d = i d 𝑔 𝑓 𝑑 𝑑 𝑖 𝑑 g\circ f+d\circ h+h\circ d=id italic_g ∘ italic_f + italic_d ∘ italic_h + italic_h ∘ italic_d = italic_i italic_d ;

  3. 3)

    f h = 0 𝑓 0 f\circ h=0 italic_f ∘ italic_h = 0 ; h g = 0 𝑔 0 h\circ g=0 italic_h ∘ italic_g = 0 ; h h = 0 0 h\circ h=0 italic_h ∘ italic_h = 0 .


Definition 1 (Clifford geometric algebra) .

A Clifford geometric algebra 𝒢 p , q subscript 𝒢 𝑝 𝑞 \mathcal{G}_{p,q} caligraphic_G start_POSTSUBSCRIPT italic_p , italic_q end_POSTSUBSCRIPT is defined by the associative geometric product of elements of a quadratic vector space p , q superscript 𝑝 𝑞 \mathbb{R}^{p,q} blackboard_R start_POSTSUPERSCRIPT italic_p , italic_q end_POSTSUPERSCRIPT , their linear combination and closure. 𝒢 p , q subscript 𝒢 𝑝 𝑞 \mathcal{G}_{p,q} caligraphic_G start_POSTSUBSCRIPT italic_p , italic_q end_POSTSUBSCRIPT includes the field of real numbers \mathbb{R} blackboard_R and the vector space p , q superscript 𝑝 𝑞 \mathbb{R}^{p,q} blackboard_R start_POSTSUPERSCRIPT italic_p , italic_q end_POSTSUPERSCRIPT as subspaces. The geometric product of two vectors is defined as

𝐚𝐛 = 𝐚 𝐛 + 𝐚 𝐛 , 𝐚𝐛 𝐚 𝐛 𝐚 𝐛 \mathrm{\mathbf{a}}\mathrm{\mathbf{b}}=\mathrm{\mathbf{a}}\cdot\mathrm{\mathbf% {b}}+\mathrm{\mathbf{a}}\wedge\mathrm{\mathbf{b}}, bold_ab = bold_a ⋅ bold_b + bold_a ∧ bold_b , (1)

where 𝐚 𝐛 normal-⋅ 𝐚 𝐛 \mathrm{\mathbf{a}}\cdot\mathrm{\mathbf{b}} bold_a ⋅ bold_b indicates the standard inner product and the bivector 𝐚 𝐛 𝐚 𝐛 \mathrm{\mathbf{a}}\wedge\mathrm{\mathbf{b}} bold_a ∧ bold_b indicates Grassmann’s antisymmetric outer product. 𝐚 𝐛 𝐚 𝐛 \mathrm{\mathbf{a}}\wedge\mathrm{\mathbf{b}} bold_a ∧ bold_b can be geometrically interpreted as the oriented parallelogram area spanned by the vectors 𝐚 𝐚 \mathrm{\mathbf{a}} bold_a and 𝐛 𝐛 \mathrm{\mathbf{b}} bold_b . Geometric algebras are graded, with grades (subspace dimensions) ranging from zero (scalars) to n = p + q 𝑛 𝑝 𝑞 n=p+q italic_n = italic_p + italic_q (pseudoscalars, n 𝑛 n italic_n -volumes).


Definition 1.21 .

Given 𝐯 𝒰 n 𝐯 superscript 𝒰 𝑛 \mathbf{v}\in{\mathcal{U}}^{n} bold_v ∈ caligraphic_U start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT , 𝒜 ( 𝐯 ) 𝒜 𝐯 \mathcal{A}(\mathbf{v}) caligraphic_A ( bold_v ) is the set of all 𝐮 𝒰 n 𝟎 𝐮 superscript 𝒰 𝑛 0 \mathbf{u}\in{\mathcal{U}}^{n}\setminus\mathbf{0} bold_u ∈ caligraphic_U start_POSTSUPERSCRIPT italic_n end_POSTSUPERSCRIPT ∖ bold_0 s.t.

𝐮 [ i ] = 0 , if 𝐯 [ i ] = 0 , formulae-sequence 𝐮 delimited-[] 𝑖 0 if 𝐯 delimited-[] 𝑖 0 \displaystyle\mathbf{u}[i]=0,\mbox{ if }\mathbf{v}[i]=0, bold_u [ italic_i ] = 0 , if bold_v [ italic_i ] = 0 ,
𝐮 [ i ] = Δ + , if 𝐯 [ i ] = Δ + , formulae-sequence 𝐮 delimited-[] 𝑖 superscript Δ if 𝐯 delimited-[] 𝑖 superscript Δ \displaystyle\mathbf{u}[i]={\Delta\!}^{\!+},\mbox{ if }\mathbf{v}[i]={\Delta\!% }^{\!+}, bold_u [ italic_i ] = roman_Δ start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT , if bold_v [ italic_i ] = roman_Δ start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT ,
𝐮 [ i ] = Δ + or 𝐮 [ i ] = 0 , if 𝐯 [ i ] = Δ . formulae-sequence 𝐮 delimited-[] 𝑖 superscript Δ or 𝐮 delimited-[] 𝑖 0 if 𝐯 delimited-[] 𝑖 Δ \displaystyle\mathbf{u}[i]={\Delta\!}^{\!+}\mbox{ or }\mathbf{u}[i]=0,\mbox{ % if }\mathbf{v}[i]=\Delta. bold_u [ italic_i ] = roman_Δ start_POSTSUPERSCRIPT + end_POSTSUPERSCRIPT or bold_u [ italic_i ] = 0 , if bold_v [ italic_i ] = roman_Δ .

Definition 6 (Semiring of series)

The set of formal power series with coefficients in a semiring 𝒮 𝒮 \mathcal{S} caligraphic_S endowed with the following sum and Cauchy product:

s s : ( s s ) ( k ) = s ( k ) s ( k ) , : direct-sum 𝑠 superscript 𝑠 direct-sum 𝑠 superscript 𝑠 𝑘 direct-sum 𝑠 𝑘 superscript 𝑠 𝑘 \displaystyle s\oplus s^{\prime}:(s\oplus s^{\prime})(k)=s(k)\oplus s^{\prime}% (k), italic_s ⊕ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT : ( italic_s ⊕ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) ( italic_k ) = italic_s ( italic_k ) ⊕ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_k ) ,
s s : ( s s ) ( k ) = i + j = k s ( i ) s ( j ) , : tensor-product 𝑠 superscript 𝑠 tensor-product 𝑠 superscript 𝑠 𝑘 subscript direct-sum 𝑖 𝑗 𝑘 tensor-product 𝑠 𝑖 superscript 𝑠 𝑗 \displaystyle s\otimes s^{\prime}:(s\otimes s^{\prime})(k)=\bigoplus_{i+j=k}s(% i)\otimes s^{\prime}(j), italic_s ⊗ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT : ( italic_s ⊗ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) ( italic_k ) = ⊕ start_POSTSUBSCRIPT italic_i + italic_j = italic_k end_POSTSUBSCRIPT italic_s ( italic_i ) ⊗ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_j ) ,

is a semiring denoted 𝒮 [ [ z 1 , , z p ] ] 𝒮 delimited-[] subscript 𝑧 1 normal-… subscript 𝑧 𝑝 \mathcal{S}[\![z_{1},...,z_{p}]\!] caligraphic_S [ [ italic_z start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , … , italic_z start_POSTSUBSCRIPT italic_p end_POSTSUBSCRIPT ] ] . If 𝒮 𝒮 \mathcal{S} caligraphic_S is complete, 𝒮 [ [ z 1 , , z p ] ] 𝒮 delimited-[] subscript 𝑧 1 normal-… subscript 𝑧 𝑝 \mathcal{S}[\![z_{1},...,z_{p}]\!] caligraphic_S [ [ italic_z start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT , … , italic_z start_POSTSUBSCRIPT italic_p end_POSTSUBSCRIPT ] ] is complete. A series with a finite support is called a polynomial, and a monomial if there is only one element in the series. The greatest lower bound of series is given by :

s s : ( s s ) ( k ) = s ( k ) s ( k ) . : 𝑠 superscript 𝑠 𝑠 superscript 𝑠 𝑘 𝑠 𝑘 superscript 𝑠 𝑘 s\wedge s^{\prime}:(s\wedge s^{\prime})(k)=s(k)\wedge s^{\prime}(k). italic_s ∧ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT : ( italic_s ∧ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ) ( italic_k ) = italic_s ( italic_k ) ∧ italic_s start_POSTSUPERSCRIPT ′ end_POSTSUPERSCRIPT ( italic_k ) .

Theorem 3.2 .

Under conditions ( 𝒜 1 ) , ( 𝒜 2 ) subscript 𝒜 1 subscript 𝒜 2 ({\cal A}_{1}),({\cal A}_{2}) ( caligraphic_A start_POSTSUBSCRIPT 1 end_POSTSUBSCRIPT ) , ( caligraphic_A start_POSTSUBSCRIPT 2 end_POSTSUBSCRIPT ) , ( 𝒜 4 ) subscript 𝒜 4 ({\cal A}_{4}) ( caligraphic_A start_POSTSUBSCRIPT 4 end_POSTSUBSCRIPT ) and ( 𝒜 7 ) subscript 𝒜 7 ({\cal A}_{7}) ( caligraphic_A start_POSTSUBSCRIPT 7 end_POSTSUBSCRIPT ) there exists a Radon measure ϱ ( X ) italic-ϱ 𝑋 \varrho\in\mathcal{M}(X) italic_ϱ ∈ caligraphic_M ( italic_X ) and a measurable function c : X normal-: 𝑐 normal-→ 𝑋 c:X\to\mathbb{R} italic_c : italic_X → blackboard_R such that

π ( μ , ) = ϱ + c μ . 𝜋 𝜇 italic-ϱ 𝑐 𝜇 \pi(\mu,\,\cdot\,)=\varrho+c\mu. italic_π ( italic_μ , ⋅ ) = italic_ϱ + italic_c italic_μ . (4)

In particular, ϱ = π ( 0 , ) italic-ϱ 𝜋 0 normal-⋅ \varrho=\pi(0,\,\cdot\,) italic_ϱ = italic_π ( 0 , ⋅ ) and c 𝑐 c italic_c is the (signed) density c ( x ) = π ( δ x , { x } ) - ϱ ( { x } ) 𝑐 𝑥 𝜋 subscript 𝛿 𝑥 𝑥 italic-ϱ 𝑥 c(x)=\pi(\delta_{x},\{x\})-\varrho(\{x\}) italic_c ( italic_x ) = italic_π ( italic_δ start_POSTSUBSCRIPT italic_x end_POSTSUBSCRIPT , { italic_x } ) - italic_ϱ ( { italic_x } ) .


Definition 3.1 .

Let 𝔤 𝔤 \mathfrak{g} fraktur_g be a Lie algebra whose centre is 𝔷 𝔷 \mathfrak{z} fraktur_z and let 𝔳 := 𝔷 assign 𝔳 superscript 𝔷 perpendicular-to \mathfrak{v}:=\mathfrak{z}^{\perp} fraktur_v := fraktur_z start_POSTSUPERSCRIPT ⟂ end_POSTSUPERSCRIPT .We say that 𝔤 𝔤 \mathfrak{g} fraktur_g is of Heisenberg-type (or simply H 𝐻 H italic_H -type) if

[ 𝔳 , 𝔳 ] = 𝔷 𝔳 𝔳 𝔷 [\mathfrak{v},\mathfrak{v}]=\mathfrak{z} [ fraktur_v , fraktur_v ] = fraktur_z

and there exists an inner product , normal-⋅ normal-⋅ \langle\cdot,\cdot\rangle ⟨ ⋅ , ⋅ ⟩ on 𝔤 𝔤 \mathfrak{g} fraktur_g with 𝔷 , 𝔳 = 0 𝔷 𝔳 0 \left<\mathfrak{z},\mathfrak{v}\right>=0 ⟨ fraktur_z , fraktur_v ⟩ = 0 such that for any Z 𝔷 𝑍 𝔷 Z\in\mathfrak{z} italic_Z ∈ fraktur_z , the map J Z : 𝔳 𝔳 normal-: subscript 𝐽 𝑍 maps-to 𝔳 𝔳 J_{Z}:\mathfrak{v}\mapsto\mathfrak{v} italic_J start_POSTSUBSCRIPT italic_Z end_POSTSUBSCRIPT : fraktur_v ↦ fraktur_v given by

J Z X , Y = [ X , Y ] , Z , subscript 𝐽 𝑍 𝑋 𝑌 𝑋 𝑌 𝑍 \langle J_{Z}X,Y\rangle=\langle[X,Y],Z\rangle, ⟨ italic_J start_POSTSUBSCRIPT italic_Z end_POSTSUBSCRIPT italic_X , italic_Y ⟩ = ⟨ [ italic_X , italic_Y ] , italic_Z ⟩ ,

for X , Y 𝔳 𝑋 𝑌 𝔳 X,Y\in\mathfrak{v} italic_X , italic_Y ∈ fraktur_v , is an orthogonal map whenever Z , Z = 1 𝑍 𝑍 1 \left<Z,Z\right>=1 ⟨ italic_Z , italic_Z ⟩ = 1 . An H 𝐻 H italic_H -type group is a connected and simply connected Lie group 𝔾 𝔾 \mathbb{G} blackboard_G whose Lie algebra is of H 𝐻 H italic_H -type.