Lie algebra decomposition
- Relate the perspective's symmetry with the equations for {$C, T, S$}.
Note that {$\mathbb{H}_{ij}=H^{(0)}\partial_{ij}+H^{(1)}_{ij}$}. I think {$H^{(0)}$} is just a constant, a scalar multiple of the identity. When {$i\neq j$} then we can simply deal with {$H^{(1)}$}. But with the diagonal elements we have to be careful because with regard to them we may have {$H^{(1)T}\neq H^{(1)*}$} when {$H^{(0)}_{jj}=a+bi$} and {$H^{(1)}_{jj}=c-bi$} for they can compensate each other's imaginary diagonal elements.
Note that Stone-Chiu-Roy relate {$J_k$} with the second quantization operators {$\mathcal{T}, \mathcal{C}$}
Hypothesis: Perspective
My hypothesis: A perspective {$J_k$} is an operator which establishes a symmetry of the form {$J_kH^*=HJ_k$}.
- {$\mathbf{U_TH^*U_T^\dagger=H}$} symmetry on {$H^*$} accessible
- {$\mathbf{U_CH^TU_C^\dagger=-H}$} symmetry on {$H^T$} inaccessible
- {$\mathbf{U_SHU_S^{-1}=-H}$} symmetry on {$H$} defined
In Stone-Chiu-Roy we have
- linear {$SH=-HS$}
- antilinear {$TH^*T^{-1}=H$}
- antilinear {$CH^*C^{-1}=-H$}
Thus time reversal establishes a symmetry of the kind we want. And it commutes with the Hamiltonian by considering the newest {$P_{k+1}$} which anticommutes with {$m\in\frak{m}_k$} for {$H=J_1m$}. But the operator may not always exist in the desired space or square as required.
Hypothesis: Shift in perspective
A shift in perspective may be the consequence of the reduction of the space to its subspace. Then operators with off-diagonal blocks may be thrown out. And operators may be expressed in terms of each other, {$J_2J_1=J_3$}, on the smaller subspace but not on the larger one.
Note that in this smaller subspace {$J_2J_1=J_3$} implies {$J_3J_2=J_2J_1J_2=J_1$} and {$J_1J_3=J_3J_2J_3=J_2$}.
Note that {$S=J_2J_3$} anticommutes with {$H_3$} and commutes with {$J_1=i$}. What does this mean for the shift in perspective?
A shift in perspective may perhaps be understood as multiplying by {$J_1=i$}, yielding a dependent perspective, as with {$J_3=J_2J_1$}.
Twofold complex Bott periodicity
Lie algebra decomposition {$\frak{g}_i=\frak{h}_i+\frak{m}_i$} | {$\frak{u}$}{$(M)\oplus\frak{u}$}{$(M)=\frak{u}$}{$(M)+\frak{m}$} | {$\frak{u}$}{$(2M)=\frak{u}$}{$(M)\oplus\frak{u}$}{$(M)+\frak{m}$} |
Operator yielding decomposition | {$iJ_1$} | {$iJ_2$} |
{$2\times 2$} blocks of Lie subalgebra {$\frak{h}_i$} | {$\begin{pmatrix} z & \\ & z \\ \end{pmatrix}$} {$z\in\mathbb{C}$} | {$\begin{pmatrix} ? & ? \\ ? & ? \\ \end{pmatrix}$} |
{$2\times 2$} blocks of subspace {$\frak{m}_i$} | {$\begin{pmatrix} z & \\ & -z \\ \end{pmatrix}$} {$z\in\mathbb{C}$} | {$\begin{pmatrix} ? & ? \\ ? & ? \\ \end{pmatrix}$} |
Hamiltonian {$H=im$} | {$\mathbf{H=H^\dagger}$} | {$\begin{pmatrix} & \mathbf{h}_{pq} \\ \mathbf{h}_{pq}^\dagger & \\ \end{pmatrix}$} |
Quantum symmetries | | {$S^2=1$} |
Eightfold real Bott periodicity
{$\frak{o}$}{$(2M)=\frak{u}$}{$(M)+\frak{m}$} | {$\frak{u}$}{$(2M)=\frak{sp}$}{$(M)+\frak{m}$} | {$\frak{sp}$}{$(2M)=\frak{sp}$}{$(M)\oplus\frak{sp}$}{$(M)+\frak{m}$} | {$\frak{sp}$}{$(M)\oplus\frak{sp}$}{$(M)=\frak{sp}$}{$(M)+\frak{m}$} |
{$J_1$} | {$J_2$} | {$J_3$} | {$J_4$} |
{$\begin{pmatrix} a & -b \\ b & a \\ \end{pmatrix}$} {$a+bi\in\mathbb{C}$} | {$\begin{pmatrix} X & Y \\ -\overline{Y} & \overline{X} \\ \end{pmatrix}$} {$X+Yj\in\mathbb{H}$} | {$\begin{pmatrix} q_1 & \\ & q_2 \\ \end{pmatrix}$} {$q_1,q_2\in\mathbb{H}$} | {$\begin{pmatrix} q & \\ & q \\ \end{pmatrix}$} {$q\in\mathbb{H}$} |
{$\begin{pmatrix} a & b \\ b & -a \\ \end{pmatrix}$} {$a,b\in\mathbb{R}$} | {$\begin{pmatrix} X & Y \\ \overline{Y} & -\overline{X} \\ \end{pmatrix}$} {$X,Y\in\mathbb{C}$} | {$\begin{pmatrix} & q_1 \\ q_2 & \\ \end{pmatrix}$} {$q_1,q_2\in\mathbb{H}$} | {$\begin{pmatrix} q & \\ & -q \\ \end{pmatrix}$} {$q\in\mathbb{H}$} |
{$\begin{pmatrix} & \mathbf{h}_{MM} \\ -\mathbf{h}_{MM}^* & \\ \end{pmatrix}$} {$m=\mathbf{h}_{MM}=-\mathbf{h}_{MM}^*$} | {$\begin{pmatrix} \mathbf{h}_{aa} & \mathbf{h}_{ab} \\ -\mathbf{h}_{ab}^* & \mathbf{h}_{aa}^* \end{pmatrix}$} | {$\begin{pmatrix} & \mathbf{h}_{rr} & \mathbf{h}_{rs} \\ & -\mathbf{h}_{rs}^* & \mathbf{h}_{rr}^* \\ \textrm{h.c} & & \\ \end{pmatrix}$} | {$\begin{pmatrix} \mathbf{h}_{aa} & \mathbf{h}_{ab} \\ \mathbf{h}_{ab}^* & -\mathbf{h}_{aa}^* \end{pmatrix}$} |
{$C^2=+1, T^2=-1, S^2=1$} | {$T^2=-1$} | {$T^2=-1,C^2=-1,S^2=1$} | {$C^2=-1$} |
{$\frak{sp}$}{$(M)=\frak{u}$}{$(M)+\frak{m}$} | {$\frak{u}$}{$(M)=\frak{o}$}{$(M)+\frak{m}$} | {$\frak{o}$}{$(2M)=\frak{o}$}{$(M)\oplus\frak{o}$}{$(M)+\frak{m}$} | {$\frak{o}$}{$(M)\oplus\frak{o}$}{$(M)=\frak{o}$}{$(M)+\frak{m}$} |
{$J_5$} | {$J_6$} | {$J_7$} | {$J_8$} |
{$\begin{pmatrix} z & \\ & z \\ \end{pmatrix}$} {$z\in\mathbb{C}\subset\mathbb{H}$} | {$\begin{pmatrix} a & \\ & a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset\mathbb{H}$} | {$\begin{pmatrix} a_1 & \\ & a_2 \\ \end{pmatrix}$} {$a_1,a_2\in \mathbb{R}\subset M_8(\mathbb{R})$} | {$\begin{pmatrix} a & \\ & a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset M_{8}(\mathbb{R})$} |
{$\begin{pmatrix} zj & \\ & zj \\ \end{pmatrix}$} {$z=a+bi\in\mathbb{C}\subset\mathbb{H}$} {$j\in\mathbb{H}$} | {$\begin{pmatrix} bi & \\ & bi \\ \end{pmatrix}$} {$b\in\mathbb{R}\subset\mathbb{H}, i\in\mathbb{H}$} | {$\begin{pmatrix} & a_1 \\ a_2 & \\ \end{pmatrix}$} {$a_1,a_2\in \mathbb{R}\subset M_8(\mathbb{R})$} | {$\begin{pmatrix} a & \\ & -a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset M_{8}(\mathbb{R})$} |
{$\begin{pmatrix} & \mathbf{h}_{MM} \\ \mathbf{h}_{MM}^* & \\ \end{pmatrix}$} {$\mathbf{h}_{MM}=\mathbf{h}_{MM}^T$} | {$\mathbf{H=H^*}$} | {$\begin{pmatrix} & \mathbf{h}_{pq} \\ \mathbf{h}_{pq}^T & \\ \end{pmatrix}$} {$\mathbf{h}_{pq}=\mathbf{h}_{pq}^*$} | {$\mathbf{H=-H^*=\begin{pmatrix} & -m \\ m & \\ \end{pmatrix}}$} |
{$C^2=-1, T^2=+1, S^2=1$} | {$T^2=+1$} | {$C^2=+1, T^2=+1, S^2=1$} | {$C^2=+1$} |
Analyzing the Hamiltonians
Lie algebra decomposition {$\frak{g}_i=\frak{h}_i+\frak{m}_i$} | {$2\times 2$} blocks of Lie subalgebra {$\frak{h}_i$} | {$2\times 2$} blocks of subspace {$\frak{m}_i$} | Hamiltonian {$H$} | simplified Hamiltonian {$\{\mathbf{Q}(k)\}$} | remarks |
{$\frak{u}$}{$(M)\oplus\frak{u}$}{$(M)=\frak{u}$}{$(M)+\frak{u}$}{$(M)$} | | | | {$G_{m,m+n}(C)$} | |
{$\frak{u}$}{$(2M)=\frak{m}$}{$+\frak{u}$}{$(M)\oplus\frak{u}$}{$(M)$} | | | | {$\begin{pmatrix} \mathbf{0}_n & \mathbf{q} \\ \mathbf{q}^\dagger & \mathbf{0}_m \\ \end{pmatrix}$} {$ \mathbf{q}\in U(m)$} | |
Lie algebra decomposition {$\frak{g}_i=\frak{h}_i+\frak{m}_i$} | {$2\times 2$} blocks of Lie subalgebra {$\frak{h}_i$} | {$2\times 2$} blocks of subspace {$\frak{m}_i$} | Hamiltonian {$H$} | simplified Hamiltonian {$\{\mathbf{Q}(k)\}$} | remarks |
{$\frak{o}$}{$(M)\oplus\frak{o}$}{$(M)=\frak{m}$}{$+\frak{o}$}{$(M)$} | {$\begin{pmatrix} a & \\ & a \\ \end{pmatrix}$} {$a\in\mathbb{R}$} | {$\begin{pmatrix} a & \\ & -a \\ \end{pmatrix}$} {$a\in\mathbb{R}$} | {$\mathbf{H=-H^*=\begin{pmatrix} & -m \\ m & \\ \end{pmatrix}}$} | {$G_{m,2m}(\mathbb{C})$} {$\tau_x\mathbf{Q}(k)^*\tau_x =-\mathbf{Q}(-k)$} | |
{$\frak{o}$}{$(2M)=\frak{m}$}{$+\frak{u}$}{$(M)$} | {$\begin{pmatrix} a & -b \\ b & a \\ \end{pmatrix}$} {$a+bi\in\mathbb{C}$} | {$\begin{pmatrix} a & b \\ b & -a \\ \end{pmatrix}$} {$a,b\in\mathbb{R}$} | {$\begin{pmatrix} & \mathbf{h}_{MM} \\ -\mathbf{h}_{MM}^* & \\ \end{pmatrix}$} {$m=\mathbf{h}_{MM}=-\mathbf{h}_{MM}^*=-\mathbf{h}_{MM}^T$} | {$\begin{pmatrix} \mathbf{0}_n & \mathbf{q} \\ \mathbf{q}^\dagger & \mathbf{0}_m \\ \end{pmatrix}$} {$ \mathbf{q}\in U(2m), \mathbf{q}(k)^T=-\mathbf{q}(-k)$} | {$J_1=S$} {$J_1H_1^*=H_1J_1$} absolute frame |
{$\frak{u}$}{$(2M)=\frak{m}$}{$+\frak{sp}$}{$(M)$} | {$\begin{pmatrix} X & Y \\ -\overline{Y} & \overline{X} \\ \end{pmatrix}$} {$X+Yj\in\mathbb{H}$} | {$\begin{pmatrix} X & Y \\ \overline{Y} & -\overline{X} \\ \end{pmatrix}$} {$X,Y\in\mathbb{C}$} | {$\begin{pmatrix} \mathbf{h}_{aa} & \mathbf{h}_{ab} \\ -\mathbf{h}_{ab}^* & \mathbf{h}_{aa}^* \end{pmatrix}$} | {$G_{2m,2m+2n}(\mathbb{C})$} {$J\mathbf{Q}(k)^*=\mathbf{Q}(-k)J$} | {$J_2=T$} {$J_2H_2^*=H_2J_2$} |
{$\frak{sp}$}{$(2M)=\frak{m}$}{$+\frak{sp}$}{$(M)\oplus\frak{sp}$}{$(M)$} | {$\begin{pmatrix} q_1 & \\ & q_2 \\ \end{pmatrix}$} {$q_1,q_2\in\mathbb{H}$} | {$\begin{pmatrix} & q_1 \\ q_2 & \\ \end{pmatrix}$} {$q_1,q_2\in\mathbb{H}$} | {$\begin{pmatrix} & \mathbf{h}_{rr} & \mathbf{h}_{rs} \\ & -\mathbf{h}_{rs}^* & \mathbf{h}_{rr}^* \\ \textrm{h.c} & & \\ \end{pmatrix}$} | {$\begin{pmatrix} \mathbf{0}_n & \mathbf{q} \\ \mathbf{q}^\dagger & \mathbf{0}_m \\ \end{pmatrix}$} {$ \mathbf{q}\in U(2m), J\mathbf{q}(k)^*=\mathbf{q}(-k)J$} | {$J_3=T$} {$J_3H_3^*=H_3J_3$} |
{$\frak{sp}$}{$(M)\oplus\frak{sp}$}{$(M)=\frak{m}$}{$+\frak{sp}$}{$(M)$} | {$\begin{pmatrix} q & \\ & q \\ \end{pmatrix}$} {$q\in\mathbb{H}$} | {$\begin{pmatrix} q & \\ & -q \\ \end{pmatrix}$} {$q\in\mathbb{H}$} | {$\begin{pmatrix} \mathbf{h}_{aa} & \mathbf{h}_{ab} \\ \mathbf{h}_{ab}^* & -\mathbf{h}_{aa}^* \end{pmatrix}$} | {$G_{m,2m}(\mathbb{C})$} {$\tau_y\mathbf{Q}^*(k)\tau_y =-\mathbf{Q}(-k)$} | |
{$\frak{sp}$}{$(M)=\frak{m}$}{$+\frak{u}($}{$M)$} | {$\begin{pmatrix} z & \\ & z \\ \end{pmatrix}$} {$z\in\mathbb{C}\subset\mathbb{H}$} | {$\begin{pmatrix} zj & \\ & zj \\ \end{pmatrix}$} {$z=a+bi\in\mathbb{C}\subset\mathbb{H}$} {$j\in\mathbb{H}$} | {$\begin{pmatrix} & \mathbf{h}_{MM} \\ \mathbf{h}_{MM}^* & \\ \end{pmatrix}$} {$\mathbf{h}_{MM}=\mathbf{h}_{MM}^T$} | {$\begin{pmatrix} \mathbf{0}_n & \mathbf{q} \\ \mathbf{q}^\dagger & \mathbf{0}_m \\ \end{pmatrix}$} {$ \mathbf{q}\in U(m), \mathbf{q}(k)^T=\mathbf{q}(-k)$} | |
{$\frak{u}$}{$(M)=\frak{m}$}{$+\frak{o}$}{$(M)$} | {$\begin{pmatrix} a & \\ & a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset\mathbb{H}$} | {$\begin{pmatrix} bi & \\ & bi \\ \end{pmatrix}$} {$b\in\mathbb{R}\subset\mathbb{H}, i\in\mathbb{H}$} | {$\mathbf{H=H^*}$} | {$G_{m,m+n}(\mathbb{C})$} {$\mathbf{Q}(k)^*=\mathbf{Q}(-k)$} | |
{$\frak{o}$}{$(2M)=\frak{m}$}{$+\frak{o}$}{$(M)\oplus\frak{o}$}{$(M)$} | {$\begin{pmatrix} a_1 & \\ & a_2 \\ \end{pmatrix}$} {$a_1,a_2\in \mathbb{R}\subset M_8(\mathbb{R})$} | {$\begin{pmatrix} & a_1 \\ a_2 & \\ \end{pmatrix}$} {$a_1,a_2\in \mathbb{R}\subset M_8(\mathbb{R})$} | {$\begin{pmatrix} & \mathbf{h}_{pq} \\ \mathbf{h}_{pq}^T & \\ \end{pmatrix}$} {$\mathbf{h}_{pq}=\mathbf{h}_{pq}^*$} | {$\begin{pmatrix} \mathbf{0}_n & \mathbf{q} \\ \mathbf{q}^\dagger & \mathbf{0}_m \\ \end{pmatrix}$} {$ \mathbf{q}\in U(m), \mathbf{q}(k)^*=\mathbf{q}(-k)$} | |
{$\frak{o}$}{$(M)\oplus\frak{o}$}{$(M)=\frak{m}$}{$+\frak{o}$}{$(M)$} | {$\begin{pmatrix} a & \\ & a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset M_{8}(\mathbb{R})$} | {$\begin{pmatrix} a & \\ & -a \\ \end{pmatrix}$} {$a\in\mathbb{R}\subset M_{8}(\mathbb{R})$} | {$\mathbf{H=-H^*}$} | | |