diff 763cb89..b34550f equivariant_jiang_su_stability_v2.txt
diff --git a/equivariant_jiang_su_stability_v2.txt b/equivariant_jiang_su_stability_v2.txt
index 30fa771..399adbc 100644
--- a/equivariant_jiang_su_stability_v2.txt
+++ b/equivariant_jiang_su_stability_v2.txt
@@ -9,15 +9,15 @@ $B$, and $Z$ is the Jiang-Su algebra.
The Jiang-Su algebra $Z$ is the unique simple unital inductive limit of
prime dimension-drop intervals with the K-theory of the complex numbers and
a unique tracial state; it is strongly self-absorbing, so
-$Z \cong Z \otimes Z$. The dimension-drop construction and these properties
+$Z \cong Z ⊗ Z$. The dimension-drop construction and these properties
appear in the study of strongly self-absorbing algebras.
./pdf/toms-winter-math0502211-strongly-self-absorbing.pdf
Theorem. Let $A$ be a simple, separable, unital, infinite-dimensional,
-nuclear, stably finite C*-algebra with $A \cong A \otimes Z$. Let $G$ be a
-countable discrete amenable group and $\alpha : G \to \mathrm{Aut}(A)$ an
-action. Put $B = A \otimes Z$ and $\beta_g = \alpha_g \otimes \mathrm{id}_Z$.
+nuclear, stably finite C*-algebra with $A \cong A ⊗ Z$. Let $G$ be a
+countable discrete amenable group and $\alpha : G \to Aut(A)$ an
+action. Put $B = A ⊗ Z$ and $\beta_g = \alpha_g ⊗ id_Z$.
Then there are a unital *-isomorphism $\Phi : A \to B$ and unitaries
$u_g \in B$ for $g \in G$ such that
@@ -28,9 +28,9 @@ for all $g, h \in G$ and $a \in A$.
Stable finiteness means that every isometry in every matrix algebra over
$A$ is a unitary. Amenability enters only through the Folner condition:
for every finite $H \subset G$ and every $\delta > 0$ there is a nonempty
-finite $F \subset G$ with $|hF \,\triangle\, F| < \delta |F|$ for every
+finite $F \subset G$ with $|hF \,△\, F| < \delta |F|$ for every
$h \in H$. The displayed relations say exactly that $\alpha$ and
-$\beta = \alpha \otimes \mathrm{id}_Z$ are cocycle conjugate, with
+$\beta = \alpha ⊗ id_Z$ are cocycle conjugate, with
$\Phi$ intertwining the two actions through the $\beta$-cocycle
$g \mapsto u_g$.
@@ -55,7 +55,7 @@ comparison of positive elements.
Theorem 1.1 (Matui and Sato). Let $A$ be a unital separable simple
infinite-dimensional nuclear C*-algebra with finitely many extremal
-traces. Then the following are equivalent: $A \otimes Z \cong A$; $A$
+traces. Then the following are equivalent: $A ⊗ Z \cong A$; $A$
has strict comparison; every completely positive map from $A$ to $A$
can be excised in small central sequences; has property (SI).
@@ -90,7 +90,7 @@ Corollary 5.12 (Haagerup). Every stably finite unital exact C*-algebra has a tra
Fix a free ultrafilter $\omega$ on the positive integers and form the
uniform tracial ultrapower
-$$ A^\omega = \ell^\infty(\mathbb N, A) / I_\omega, \qquad I_\omega = \{(a_j) : \lim_{j \to \omega} \|a_j\|_{2,u} = 0\}. $$
+$$ A^\omega = \ell^∞(\mathbb N, A) / I_\omega, \qquad I_\omega = \{(a_j) : \lim_{j \to \omega} \|a_j\|_{2,u} = 0\}. $$
The inequalities $\|ab\|_{2,u} \le \|a\| \|b\|_{2,u}$ and
$\|ba\|_{2,u} \le \|a\| \|b\|_{2,u}$ show that $I_\omega$ is a closed
@@ -105,7 +105,7 @@ $\bar\alpha : G \curvearrowright A^\omega$ preserving $A^\omega \cap A'$.
An action $\alpha : G \curvearrowright A$ has equivariant uniform property
Gamma if for every integer $k \ge 2$ there are pairwise orthogonal
-projections $p_1, \ldots, p_k \in (A^\omega \cap A')^{\bar\alpha}$ with
+projections $p_1, ..., p_k \in (A^\omega \cap A')^{\bar\alpha}$ with
$\tau(a p_i) = \tau(a)/k$ for every $a \in A$, every
$\tau \in \mathcal T_\omega(A)$, and every $i$. The construction also
forces $\sum_i p_i = 1$. The absorption criterion to be used states that a
@@ -128,27 +128,27 @@ $$ C_i = C^*(\bar\alpha_g(\iota_i(Z)) : g \in G) $$
commute with $A$ and commute pairwise. Consequently
-$$ C = C^*\Bigl(\bigcup_{i \ge 1} C_i\Bigr) \subseteq A^\omega \cap A' $$
+$$ C = C^*(∪_{i \ge 1} C_i) ⊆ A^\omega \cap A' $$
is a unital separable $\bar\alpha$-invariant subalgebra with
-$\mathcal T(C) \neq \emptyset$. There are moreover self-adjoint elements
-$x_{i,g} \in C_i$ and a constant $M < \infty$ with
+$\mathcal T(C) \neq ∅$. There are moreover self-adjoint elements
+$x_{i,g} \in C_i$ and a constant $M < ∞$ with
$$ \|x_{i,g}\| \le M, \qquad \varphi(x_{i,g}) = 0, \qquad \varphi(x_{i,g}^2) = 1 \quad (\varphi \in \mathcal T(C)), \qquad \bar\alpha_h(x_{i,g}) = x_{i,hg} $$
for all $i \ge 1$ and $g, h \in G$.
Proof. Since $A$ is $Z$-stable, fix an identification
-$A \cong A \otimes \bigotimes_{l \ge 1} Z$ and use its increasing finite
+$A \cong A ⊗ ⊗_{l \ge 1} Z$ and use its increasing finite
tensor stages. First, every norm-separable C*-subalgebra
-$D \subseteq A^\omega$ admits a unital embedding $Z \to A^\omega \cap D'$.
+$D ⊆ A^\omega$ admits a unital embedding $Z \to A^\omega \cap D'$.
Choose a norm-dense sequence $(d_s)_{s \ge 1}$ in $D$ with bounded
representatives $d_s = [(d_{s,j})_{j \ge 1}]$. For each $j$ choose a finite
tensor stage containing elements within $1/j$ in norm of
-$d_{1,j}, \ldots, d_{j,j}$, and let $\theta_j : Z \to A$ embed into a tensor
+$d_{1,j}, ..., d_{j,j}$, and let $\theta_j : Z \to A$ embed into a tensor
factor strictly after that stage. For $j \ge s$ and $z \in Z$,
-$$ \|[\theta_j(z), d_{s,j}]\| \le \frac{2\|z\|}{j}. $$
+$$ \|[\theta_j(z), d_{s,j}]\| \le (2\|z\|)/(j). $$
The coordinatewise homomorphisms therefore induce a unital *-homomorphism
$z \mapsto [(\theta_j(z))_j]$ into $A^\omega \cap D'$, injective because $Z$
@@ -166,7 +166,7 @@ $$ [\bar\alpha_g(b), d] = \bar\alpha_g([b, \bar\alpha_{g^{-1}}(d)]) = 0, $$
so $C_i$ commutes with $D_{i-1}$. Countability of $G$ keeps each $D_i$
separable, yielding the required algebras and commutation. A limit trace on
$A^\omega$ restricts to a tracial state on $C$, so
-$\mathcal T(C) \neq \emptyset$.
+$\mathcal T(C) \neq ∅$.
The trace $\rho$ of $Z$ is faithful by simplicity. Pick a non-scalar
self-adjoint $c \in Z$; then $\rho((c - \rho(c)1)^2) > 0$, and rescaling
@@ -183,19 +183,19 @@ Lemma. Let $B$ be a unital C*-algebra generated by pairwise commuting
unital C*-subalgebras $B_i$, $i \ge 1$. If $\varphi$ is an extreme point of
$\mathcal T(B)$, then
-$$ \varphi(b_1 \cdots b_s) = \prod_{j=1}^s \varphi(b_j) $$
+$$ \varphi(b_1 ... b_s) = \prod_{j=1}^s \varphi(b_j) $$
-whenever $b_j \in B_{i_j}$ and the indices $i_1, \ldots, i_s$ are distinct.
+whenever $b_j \in B_{i_j}$ and the indices $i_1, ..., i_s$ are distinct.
-Proof. Let $(H_\varphi, \pi, \Omega)$ be the tracial GNS representation and
+Proof. Let $(H_\varphi, \pi, Ω)$ be the tracial GNS representation and
put $\mathcal M = \pi(B)''$ and $\mathcal M_i = \pi(B_i)''$. On the dense
subspace of classes $[a]$, $a \in B$, right multiplication
$R_b[a] = [ab]$ is bounded with norm at most $\|b\|$ by traciality, and it
-commutes with $\pi(B)$ while the vectors $R_b \Omega = [b]$ are dense. If
-$T \in \mathcal M$ has $T \Omega = 0$, then $T R_b \Omega = R_b T \Omega = 0$
-for all $b$, so $T = 0$. Thus $\Omega$ is separating for $\mathcal M$, and
-the normal vector state $\tau(T) = \langle T \Omega, \Omega \rangle$ is
-faithful: for $T \ge 0$, $\tau(T) = 0$ forces $T^{1/2}\Omega = 0$. Its
+commutes with $\pi(B)$ while the vectors $R_b Ω = [b]$ are dense. If
+$T \in \mathcal M$ has $T Ω = 0$, then $T R_b Ω = R_b T Ω = 0$
+for all $b$, so $T = 0$. Thus $Ω$ is separating for $\mathcal M$, and
+the normal vector state $\tau(T) = < T Ω, Ω >$ is
+faithful: for $T \ge 0$, $\tau(T) = 0$ forces $T^{1/2}Ω = 0$. Its
traciality passes from $\pi(B)$ to $\mathcal M$ by separate ultraweak
continuity, so $\mathcal M$ is a finite von Neumann algebra with faithful
normal trace $\tau$.
@@ -203,7 +203,7 @@ normal trace $\tau$.
Extremality forces $\mathcal M$ to be a factor. A nontrivial central
projection $p \in \mathcal M$ would give the convex decomposition
-$$ \varphi(a) = \tau(p) \frac{\tau(p \pi(a))}{\tau(p)} + \tau(1-p) \frac{\tau((1-p)\pi(a))}{\tau(1-p)}, $$
+$$ \varphi(a) = \tau(p) (\tau(p \pi(a)))/(\tau(p)) + \tau(1-p) (\tau((1-p)\pi(a)))/(\tau(1-p)), $$
and the two normalized summands are distinct tracial states on $B$: were the
first equal to $\varphi$, equality of the normal functionals would extend
@@ -211,7 +211,7 @@ from $\pi(B)$ to $\mathcal M$ and evaluation at $p$ would give
$1 = \tau(p)$, contradicting $0 < \tau(p) < 1$.
The algebras $\mathcal M_i$ commute and generate $\mathcal M$, so each
-center satisfies $Z(\mathcal M_i) \subseteq Z(\mathcal M) = \mathbb C 1$,
+center satisfies $Z(\mathcal M_i) ⊆ Z(\mathcal M) = \mathbb C 1$,
and $\tau$ makes every $\mathcal M_i$ a finite factor with a faithful normal
tracial state. Fix $i$ and let $y \ge 0$ lie in the von Neumann algebra
generated by the other $\mathcal M_j$. It commutes with $\mathcal M_i$, and
@@ -232,7 +232,7 @@ successively gives the product formula. This proves the lemma.
For $N \ge 1$ and $g, h \in G$ set
-$$ z_{N,g} = \frac{1}{\sqrt N} \sum_{i=1}^N x_{i,g}, \qquad k_{N;g,h} = \frac{1}{N} \sum_{i=1}^N \frac{x_{i,g} x_{i,h} + x_{i,h} x_{i,g}}{2}. $$
+$$ z_{N,g} = (1)/(\sqrt N) \sum_{i=1}^N x_{i,g}, \qquad k_{N;g,h} = (1)/(N) \sum_{i=1}^N \frac{x_{i,g} x_{i,h} + x_{i,h} x_{i,g}}{2}. $$
The last two subscripts of $k_{N;g,h}$ are covariance indices. These
elements are self-adjoint, $k_{N;g,h} = k_{N;h,g}$, and
@@ -242,28 +242,28 @@ $$ \bar\alpha_l(z_{N,g}) = z_{N,lg}, \qquad \bar\alpha_l(k_{N;g,h}) = k_{N;lg,lh
The joint limit of these variables is Gaussian, and its covariance is the
limit of the empirical covariances.
-Proposition. Let $J \subseteq G$ be nonempty and finite, let
-$N_j \to \infty$, and let $\varphi_j$ be extreme points of
+Proposition. Let $J ⊆ G$ be nonempty and finite, let
+$N_j \to ∞$, and let $\varphi_j$ be extreme points of
$\mathcal T(C)$ with $\varphi_j(k_{N_j;g,h}) \to R_{g,h}$ for
$g, h \in J$. Then $R = (R_{g,h})$ is a real positive semidefinite matrix
with diagonal entries one. Choose unit vectors $v_g$ with
-$\langle v_g, v_h \rangle = R_{g,h}$, spanning a finite-dimensional real
+$< v_g, v_h > = R_{g,h}$, spanning a finite-dimensional real
Euclidean space $L$, let $W$ be standard Gaussian in $L$, and put
-$\xi_g = \langle v_g, W \rangle$. Then the pairs
+$\xi_g = < v_g, W >$. Then the pairs
$((z_{N_j,g})_g, (k_{N_j;g,h})_{g,h})$ converge in all ordered joint
moments under $\varphi_j$ to $((\xi_g)_g, (R_{g,h})_{g,h})$. Equivalently,
for every noncommutative *-polynomial $P$ in these self-adjoint variables,
-$$ \varphi_j\bigl(P((z_{N_j,g})_g, (k_{N_j;g,h})_{g,h})\bigr) \longrightarrow \mathbb E\, P((\xi_g)_g, (R_{g,h})_{g,h}). $$
+$$ \varphi_j(P((z_{N_j,g})_g, (k_{N_j;g,h})_{g,h})) → \mathbb E\, P((\xi_g)_g, (R_{g,h})_{g,h}). $$
For every sequence $(N_j, \varphi_j)$ a subsequence satisfies the covariance
convergence.
Proof. For a tracial $\varphi$ and self-adjoint $x, y$ one has
-$\varphi(xy) = \varphi(yx) = \overline{\varphi(xy)}$, so the second moments
+$\varphi(xy) = \varphi(yx) = \varphi(xy)bar$, so the second moments
are real and symmetric. For real scalars $a_g$,
-$$ \sum_{g,h \in J} a_g a_h \varphi_j(k_{N_j;g,h}) = \frac{1}{N_j} \sum_{i=1}^{N_j} \varphi_j\Bigl(\bigl(\sum_{g \in J} a_g x_{i,g}\bigr)^2\Bigr) \ge 0. $$
+$$ \sum_{g,h \in J} a_g a_h \varphi_j(k_{N_j;g,h}) = (1)/(N_j) \sum_{i=1}^{N_j} \varphi_j((\sum_{g \in J} a_g x_{i,g})^2) \ge 0. $$
The diagonal entries are one by the row normalization, and Cauchy-Schwarz
bounds every entry by one in absolute value. The covariance matrices
@@ -275,7 +275,7 @@ Consider a word of length $d \ge 1$ in the fluctuation variables. At one
term of the sequence write $N = N_j$, $\varphi = \varphi_j$. Expanding the
sums gives
-$$ \varphi(z_{N,g_1} \cdots z_{N,g_d}) = N^{-d/2} \sum_{i_1, \ldots, i_d = 1}^N \varphi(x_{i_1,g_1} \cdots x_{i_d,g_d}). $$
+$$ \varphi(z_{N,g_1} ... z_{N,g_d}) = N^{-d/2} \sum_{i_1, ..., i_d = 1}^N \varphi(x_{i_1,g_1} ... x_{i_d,g_d}). $$
Partition the positions by equality of row labels. Distinct rows commute,
so the factors belonging to one row can be grouped while preserving their
@@ -290,21 +290,21 @@ zero, and for $d = 2q$ only pairings into $q$ pairs can survive.
Fix such a pairing with pairs $(a_l, b_l)$, $1 \le l \le q$. Its
contribution is
-$$ N^{-q} \sum_{\substack{1 \le i_1, \ldots, i_q \le N \\ i_1, \ldots, i_q \ \mathrm{distinct}}} \prod_{l=1}^q \varphi(x_{i_l,g_{a_l}} x_{i_l,g_{b_l}}). $$
+$$ N^{-q} \sum_{\substack{1 \le i_1, ..., i_q \le N \\ i_1, ..., i_q \ distinct}} \prod_{l=1}^q \varphi(x_{i_l,g_{a_l}} x_{i_l,g_{b_l}}). $$
Removing the distinctness condition changes this by $O_{d,M}(N^{-1})$: there
are at most $\binom{q}{2} N^{q-1}$ tuples with a collision, and each product
is bounded by $M^{2q}$. The unrestricted sum factors, and traciality
identifies the factors with the empirical covariances:
-$$ \prod_{l=1}^q \Bigl(\frac1N \sum_{i=1}^N \varphi(x_{i,g_{a_l}} x_{i,g_{b_l}})\Bigr) = \prod_{l=1}^q \varphi(k_{N;g_{a_l},g_{b_l}}). $$
+$$ \prod_{l=1}^q (\frac1N \sum_{i=1}^N \varphi(x_{i,g_{a_l}} x_{i,g_{b_l}})) = \prod_{l=1}^q \varphi(k_{N;g_{a_l},g_{b_l}}). $$
The error estimates depend only on $d$ and $M$, so these are uniform in the
moving traces $\varphi_j$. By the covariance convergence the limiting even
moment is the sum over pairings of the corresponding products of entries of
$R$. This is exactly the Gaussian moment: the moment generating function
-$$ \mathbb E \exp\Bigl(\sum_{g \in J} t_g \xi_g\Bigr) = \exp\Bigl(\frac12 \sum_{g,h \in J} t_g t_h R_{g,h}\Bigr) $$
+$$ \mathbb E \exp(\sum_{g \in J} t_g \xi_g) = \exp(\frac12 \sum_{g,h \in J} t_g t_h R_{g,h}) $$
has the same Taylor expansion.
@@ -317,7 +317,7 @@ The centering is row by row at the current trace, so
$\varphi_j(y_{j,i;g,h}) = 0$ and $\|y_{j,i;g,h}\| \le 2M^2$, and there is
the identity
-$$ k_{N_j;g,h} - \varphi_j(k_{N_j;g,h}) 1 = \frac{1}{N_j} \sum_{i=1}^{N_j} y_{j,i;g,h}. $$
+$$ k_{N_j;g,h} - \varphi_j(k_{N_j;g,h}) 1 = (1)/(N_j) \sum_{i=1}^{N_j} y_{j,i;g,h}. $$
Let $U_j$ be a word having $d$ fluctuation factors and $r \ge 1$ centered
covariance factors of the last form, expanded over rows. Each of its $d + r$
@@ -328,7 +328,7 @@ one row are bounded by the product of the operator norms of the factors.
Finitely many partitions of the $d+r$ positions occur, and with the
normalization $N_j^{-d/2 - r}$ these observations give
-$$ |\varphi_j(U_j)| \le C_{d,r,M} N_j^{\lfloor (d+r)/2 \rfloor - d/2 - r} \le C_{d,r,M} N_j^{-r/2} \longrightarrow 0, $$
+$$ |\varphi_j(U_j)| \le C_{d,r,M} N_j^{\lfloor (d+r)/2 \rfloor - d/2 - r} \le C_{d,r,M} N_j^{-r/2} → 0, $$
with a constant independent of $j$ and $\varphi_j$.
@@ -346,12 +346,12 @@ $x_{i,g}$, $z_{N,g}$, $k_{N;g,h}$ built above. Thus $\mathcal T(C)$ is
nonempty, $\|x_{i,g}\| \le M$, and the joint moment limit applies to any
sequence of extreme traces. Traces of finite-dimensional matrices in this
part are unnormalized, and for a matrix $B$ write
-$\|B\|_{\mathrm{HS}} = (\mathrm{Tr}(B^*B))^{1/2}$ and
-$\|B\|_1 = \mathrm{Tr}|B|$.
+$\|B\|_{HS} = (Tr(B^*B))^{1/2}$ and
+$\|B\|_1 = Tr|B|$.
Proposition. For every finite $H \subset G$, every $\eps > 0$, and every
integer $m \ge 1$ there are $t > 0$ and a self-adjoint $Q \in C$ such that
-$V = \exp(\mathrm{i} t Q)$ satisfies
+$V = \exp(i t Q)$ satisfies
$$ \sup_{\varphi \in \mathcal T(C)} \|\bar\alpha_h(V) - V\|_{2,\varphi} < \eps \quad (h \in H), $$
@@ -360,60 +360,60 @@ $$ \sup_{\varphi \in \mathcal T(C)} |\varphi(V^\ell)| < \eps \quad (1 \le \ell \
Three estimates are needed first.
Lemma. If $S, T$ are positive matrices of the same size, then
-$\|S^{1/2} - T^{1/2}\|_{\mathrm{HS}}^2 \le \|S - T\|_1$.
+$\|S^{1/2} - T^{1/2}\|_{HS}^2 \le \|S - T\|_1$.
Proof. Set $a = S^{1/2}$, $b = T^{1/2}$, $d = a - b$, and
-$u = \mathrm{sign}(d)$ with $\mathrm{sign}(0) = 0$. Since
+$u = sign(d)$ with $sign(0) = 0$. Since
$a^2 - b^2 = ad + db$, cyclicity of the trace gives
-$\mathrm{Tr}(u(a^2 - b^2)) = \mathrm{Tr}(|d|(a + b))$. Diagonalizing $d$
+$Tr(u(a^2 - b^2)) = Tr(|d|(a + b))$. Diagonalizing $d$
gives $a_{jj} + b_{jj} \ge |a_{jj} - b_{jj}| = |d_j|$ by positivity, so
-$$ \mathrm{Tr}(|d|(a+b)) = \sum_j |d_j|(a_{jj}+b_{jj}) \ge \sum_j d_j^2 = \mathrm{Tr}(d^2). $$
+$$ Tr(|d|(a+b)) = \sum_j |d_j|(a_{jj}+b_{jj}) \ge \sum_j d_j^2 = Tr(d^2). $$
The operator $u$ is a contraction, so trace-norm duality gives
-$\mathrm{Tr}(u(a^2 - b^2)) \le \mathrm{Tr}|a^2 - b^2|$. The two
+$Tr(u(a^2 - b^2)) \le Tr|a^2 - b^2|$. The two
inequalities prove the lemma.
Lemma. Let $W$ be a standard Gaussian vector in a finite-dimensional real
Euclidean space and let $B$ be a real symmetric operator there. Put
-$q_B = \langle W, BW \rangle - \mathrm{Tr}(B)$. Then
+$q_B = < W, BW > - Tr(B)$. Then
-$$ \|q_B\|_{L^2} = \sqrt{2} \|B\|_{\mathrm{HS}}, \qquad \bigl|\mathbb E \exp(\mathrm{i} s q_B)\bigr| \le (1 + 4 s^2 \|B\|_{\mathrm{HS}}^2)^{-1/4} $$
+$$ \|q_B\|_{L^2} = √(2) \|B\|_{HS}, \qquad |\mathbb E \exp(i s q_B)| \le (1 + 4 s^2 \|B\|_{HS}^2)^{-1/4} $$
for every real $s$. The law of $q_B$ has an exponential moment and is
determined by its moments.
Proof. Orthogonal diagonalization writes
-$q_B \overset{\mathrm{law}}{=} \sum_j \lambda_j(U_j^2 - 1)$ with independent
+$q_B \overset{law}{=} \sum_j \lambda_j(U_j^2 - 1)$ with independent
standard normals $U_j$. The summands are centered with variances
$2\lambda_j^2$, giving the first formula. The one-dimensional Gaussian
integral gives
-$|\mathbb E \exp(\mathrm{i} s q_B)| = \prod_j (1 + 4 s^2 \lambda_j^2)^{-1/4}$,
+$|\mathbb E \exp(i s q_B)| = \prod_j (1 + 4 s^2 \lambda_j^2)^{-1/4}$,
and $\prod_j (1 + a_j) \ge 1 + \sum_j a_j$ for nonnegative $a_j$ gives the
second formula.
Choose $c > 0$ with $2 c \max_j |\lambda_j| < 1$, any $c$ when $B = 0$.
The pointwise bound
-$$ \exp\Bigl(c\bigl|\sum_j \lambda_j(U_j^2 - 1)\bigr|\Bigr) \le \exp\Bigl(c\sum_j |\lambda_j|\Bigr) \prod_j \exp(c|\lambda_j| U_j^2) $$
+$$ \exp(c|\sum_j \lambda_j(U_j^2 - 1)|) \le \exp(c\sum_j |\lambda_j|) \prod_j \exp(c|\lambda_j| U_j^2) $$
-and the Gaussian integral show $\mathbb E \exp(c|q_B|) < \infty$. Let $\nu$
+and the Gaussian integral show $\mathbb E \exp(c|q_B|) < ∞$. Let $\nu$
be another probability measure with the same moments. By the nonnegative
-power series for $\cosh$ and monotone convergence,
+power series for $cosh$ and monotone convergence,
-$$ \int_{\mathbb R} \cosh(cx)\, d\nu(x) = \sum_{r=0}^{\infty} \frac{c^{2r}}{(2r)!} \mathbb E(q_B^{2r}) = \mathbb E \cosh(c q_B) < \infty. $$
+$$ \int_{\mathbb R} cosh(cx)\, d\nu(x) = \sum_{r=0}^{∞} \frac{c^{2r}}{(2r)!} \mathbb E(q_B^{2r}) = \mathbb E cosh(c q_B) < ∞. $$
-Since $e^{c|x|} \le 2\cosh(cx)$, the measure $\nu$ has an exponential
+Since $e^{c|x|} \le 2cosh(cx)$, the measure $\nu$ has an exponential
moment. The characteristic functions of $\nu$ and of $q_B$ extend
-analytically to the strip $|\operatorname{Im} z| < c$, their Taylor
+analytically to the strip $|Im z| < c$, their Taylor
coefficients at zero agree, and the identity theorem makes them equal.
Uniqueness of characteristic functions gives $\nu$ equal to the law of
$q_B$. This proves the lemma.
The square-root normalization is exactly what keeps the variance away from
-zero. For a positive real symmetric matrix $P$ with $\mathrm{Tr}(P) = 1$
-the variance formulas give $\mathrm{Var}(q_{P^{1/2}}) = 2$ and
-$\mathrm{Var}(q_P) = 2\mathrm{Tr}(P^2)$. The latter equals $2$ for a
+zero. For a positive real symmetric matrix $P$ with $Tr(P) = 1$
+the variance formulas give $Var(q_{P^{1/2}}) = 2$ and
+$Var(q_P) = 2Tr(P^2)$. The latter equals $2$ for a
rank-one projection but $2/n$ for $P = n^{-1} I_n$, so using $P$ directly
would make the variance vanish as the rank grows. The square root fixes the
variance at $2$, and the perturbation lemma controls its change under
@@ -428,7 +428,7 @@ $f : \mathbb R \to \mathbb C$. No uniform bound on $\|X_j\|$ is needed.
Proof. Let $\mu_j$ be the spectral law of $X_j$ under $\varphi_j$. The
second moments are bounded, so the sequence is tight. Fix $d \ge 0$ and an
-even integer $2r > d$. Moment convergence gives $C_r < \infty$ with
+even integer $2r > d$. Moment convergence gives $C_r < ∞$ with
$\int |x|^{2r} d\mu_j(x) \le C_r$ for all $j$, hence
$$ \int_{|x| > K} |x|^d\, d\mu_j(x) \le C_r K^{d-2r} \qquad (K > 0). $$
@@ -437,7 +437,7 @@ Take any weakly convergent subsequence with limit $\mu$. Lower
semicontinuity gives $\int |x|^{2r} d\mu(x) \le C_r$, so the same tail bound
holds for $\mu$. Multiply $x^d$ by a continuous cutoff equal to one on
$[-K, K]$ and zero outside $[-2K, 2K]$; weak convergence applies to this
-bounded continuous function, and letting $K \to \infty$ with the tail bound
+bounded continuous function, and letting $K \to ∞$ with the tail bound
gives $\int x^d d\mu(x) = \mathbb E(q_B^d)$ for every $d$. The previous
lemma identifies $\mu$ with the law of $q_B$. Tightness then forces the
whole sequence $\mu_j$ to converge weakly to that law, since every
@@ -448,63 +448,63 @@ Proof of the proposition. Step 1, parameters. Fix $H, \eps, m$. Choose
$t > 0$ with $(1 + t^2)^{-1/4} < \eps/4$, then choose $\delta > 0$ and
$0 < \eta < 1/2$ with $t\sqrt2(\sqrt\delta + 2\eta) < \eps/4$. Amenability
gives a nonempty finite $F \subset G$ with
-$|hF \,\triangle\, F| < \delta|F|$ for $h \in H$. Set $n = |F|$ and
-$J = F \cup \bigcup_{h \in H} hF$. Finally choose a real polynomial
+$|hF \,△\, F| < \delta|F|$ for $h \in H$. Set $n = |F|$ and
+$J = F \cup ∪_{h \in H} hF$. Finally choose a real polynomial
-$$ p(s) = \sum_{r=1}^D c_r s^r, \qquad \sup_{0 \le s \le 1} |p(s) - \sqrt{s}| < \eta/\sqrt{n}. $$
+$$ p(s) = \sum_{r=1}^D c_r s^r, \qquad \sup_{0 \le s \le 1} |p(s) - √(s)| < \eta/√(n). $$
-Such a polynomial exists: approximate $\sqrt{s}$ on $[0,1]$ by a real
+Such a polynomial exists: approximate $√(s)$ on $[0,1]$ by a real
polynomial within $\eta/(2\sqrt n)$, then subtract its value at zero.
-Thus $t, \delta, \eta, F, n, J, p$ are fixed before $N \to \infty$ and are
+Thus $t, \delta, \eta, F, n, J, p$ are fixed before $N \to ∞$ and are
not chosen from any trace or limiting covariance.
Step 2, uniform Gaussian comparison. Let $R = (R_{g,g'})_{g,g' \in J}$ be
any real positive semidefinite matrix with diagonal one. Choose unit
vectors $v_g$ with Gram matrix $R$ in a finite-dimensional real Euclidean
space $L$, let $W$ be standard Gaussian in $L$, and write
-$\xi_g = \langle v_g, W \rangle$. For $E = F$ or $E = hF$ set
+$\xi_g = < v_g, W >$. For $E = F$ or $E = hF$ set
-$$ P_E = \frac1n \sum_{g \in E} v_g v_g^{\mathsf T}, \qquad B_E = p(P_E), \qquad q_E = \langle W, B_E W \rangle - \mathrm{Tr}(B_E). $$
+$$ P_E = \frac1n \sum_{g \in E} v_g v_g^{\mathsf T}, \qquad B_E = p(P_E), \qquad q_E = < W, B_E W > - Tr(B_E). $$
The operator $P_E$ is positive with trace one and spectrum in $[0,1]$, of
rank at most $n$. Because $p(0) = 0$, the operator $p(P_E) - P_E^{1/2}$
vanishes on the kernel of $P_E$, and the scalar approximation gives
-$$ \|B_E - P_E^{1/2}\|_{\mathrm{HS}}^2 \le \mathrm{rank}(P_E)\, \eta^2/n \le \eta^2, \qquad \|P_E^{1/2}\|_{\mathrm{HS}}^2 = \mathrm{Tr}(P_E) = 1, $$
+$$ \|B_E - P_E^{1/2}\|_{HS}^2 \le rank(P_E)\, \eta^2/n \le \eta^2, \qquad \|P_E^{1/2}\|_{HS}^2 = Tr(P_E) = 1, $$
-hence $1 - \eta \le \|B_E\|_{\mathrm{HS}} \le 1 + \eta$.
+hence $1 - \eta \le \|B_E\|_{HS} \le 1 + \eta$.
The summands indexed by $F \cap hF$ cancel in $P_F - P_{hF}$, and each
remaining $v_g v_g^{\mathsf T}$ has trace norm one, so the square-root
lemma gives
-$$ \|P_F^{1/2} - P_{hF}^{1/2}\|_{\mathrm{HS}}^2 \le \|P_F - P_{hF}\|_1 \le \frac{|F \,\triangle\, hF|}{n} < \delta. $$
+$$ \|P_F^{1/2} - P_{hF}^{1/2}\|_{HS}^2 \le \|P_F - P_{hF}\|_1 \le (|F \,△\, hF|)/(n) < \delta. $$
With the rank control this yields
-$\|B_F - B_{hF}\|_{\mathrm{HS}} \le \sqrt\delta + 2\eta$. Both forms
+$\|B_F - B_{hF}\|_{HS} \le \sqrt\delta + 2\eta$. Both forms
$q_F, q_{hF}$ are evaluated on the same $W$, so their difference is the
centered quadratic of $B_{hF} - B_F$, and the Gaussian quadratic lemma
gives $\|q_{hF} - q_F\|_{L^2} \le \sqrt2(\sqrt\delta + 2\eta)$. Also, by
the nondegeneracy and $\eta < 1/2$, for every integer $\ell \ge 1$,
-$$ \bigl|\mathbb E \exp(\mathrm{i}\ell t q_F)\bigr| \le (1 + 4\ell^2 t^2 \|B_F\|_{\mathrm{HS}}^2)^{-1/4} \le (1 + t^2)^{-1/4}. $$
+$$ |\mathbb E \exp(i\ell t q_F)| \le (1 + 4\ell^2 t^2 \|B_F\|_{HS}^2)^{-1/4} \le (1 + t^2)^{-1/4}. $$
All these bounds hold for every such $R$, singular or not, and no
translation invariance of $R$ has been used.
Step 3, the equivariant polynomial prescription. Direct multiplication of
the rank-one summands gives
-$P_E^r = n^{-r} \sum_{g_1, \ldots, g_r \in E} R_{g_1,g_2} \cdots R_{g_{r-1},g_r} v_{g_1} v_{g_r}^{\mathsf T}$.
+$P_E^r = n^{-r} \sum_{g_1, ..., g_r \in E} R_{g_1,g_2} ... R_{g_{r-1},g_r} v_{g_1} v_{g_r}^{\mathsf T}$.
Taking quadratic forms and traces shows
-$$ q_E = \sum_{r=1}^D \frac{c_r}{n^r} \sum_{g_1, \ldots, g_r \in E} R_{g_1,g_2} \cdots R_{g_{r-1},g_r} (\xi_{g_1} \xi_{g_r} - R_{g_r,g_1}), $$
+$$ q_E = \sum_{r=1}^D (c_r)/(n^r) \sum_{g_1, ..., g_r \in E} R_{g_1,g_2} ... R_{g_{r-1},g_r} (\xi_{g_1} \xi_{g_r} - R_{g_r,g_1}), $$
with the empty product interpreted as $1$ when $r = 1$. Use the same
prescription in $C$:
-$$ \widetilde Q_{N,E} = \sum_{r=1}^D \frac{c_r}{n^r} \sum_{g_1, \ldots, g_r \in E} k_{N;g_1,g_2} \cdots k_{N;g_{r-1},g_r} (z_{N,g_1} z_{N,g_r} - k_{N;g_r,g_1}), $$
+$$ \widetilde Q_{N,E} = \sum_{r=1}^D (c_r)/(n^r) \sum_{g_1, ..., g_r \in E} k_{N;g_1,g_2} ... k_{N;g_{r-1},g_r} (z_{N,g_1} z_{N,g_r} - k_{N;g_r,g_1}), $$
-$$ Q_{N,E} = \tfrac12\bigl(\widetilde Q_{N,E} + \widetilde Q_{N,E}^{\,*}\bigr). $$
+$$ Q_{N,E} = \tfrac12(\widetilde Q_{N,E} + \widetilde Q_{N,E}^{\,*}). $$
Multiplication is in the displayed order. The empirical covariance array
need satisfy no positivity condition, because this is a finite polynomial in
@@ -517,7 +517,7 @@ commutes with $\bar\alpha_h$. Hence
$$ Q_{N,hF} = \bar\alpha_h(Q_{N,F}) \qquad (h \in H,\ N \ge 1). $$
-Step 4, transfer of moments and scalar laws. Take any $N_j \to \infty$ and
+Step 4, transfer of moments and scalar laws. Take any $N_j \to ∞$ and
extreme traces $\varphi_j \in \mathcal T(C)$ with
$\varphi_j(k_{N_j;g,g'}) \to R_{g,g'}$ for $g, g' \in J$. The joint moment
limit gives convergence of every ordered mixed moment of the empirical
@@ -526,9 +526,9 @@ linear combination of these. Since the limiting variables commute and the
closed formula for $q_E$ is real-valued, the $Q_{N_j,E}$ converge jointly
in moments under $\varphi_j$ to the $q_E$. In particular
-$$ \|Q_{N_j,hF} - Q_{N_j,F}\|_{2,\varphi_j} \longrightarrow \|q_{hF} - q_F\|_{L^2}, $$
+$$ \|Q_{N_j,hF} - Q_{N_j,F}\|_{2,\varphi_j} → \|q_{hF} - q_F\|_{L^2}, $$
-$$ \varphi_j(\exp(\mathrm{i} s Q_{N_j,F})) \longrightarrow \mathbb E \exp(\mathrm{i} s q_F) $$
+$$ \varphi_j(\exp(i s Q_{N_j,F})) → \mathbb E \exp(i s q_F) $$
for every real $s$. The passage to scalar spectral laws is needed because
the operator norms of $Q_{N,E}$ may grow with $N$: the estimates
@@ -537,22 +537,22 @@ $\|Q_{N,E}\| \le (N+1) \sum_r |c_r| M^{2r}$. Scalar moment convergence
together with the spectral tail estimate is enough for the exponential
convergence.
-Step 5, uniformity over all traces. Set $V_N = \exp(\mathrm{i} t Q_{N,F})$.
+Step 5, uniformity over all traces. Set $V_N = \exp(i t Q_{N,F})$.
For self-adjoint $X, Y$ in a unital C*-algebra and a tracial $\varphi$,
differentiation gives
-$$ \frac{d}{ds}\bigl(e^{\mathrm{i}(1-s)tX} e^{\mathrm{i}stY}\bigr) = e^{\mathrm{i}(1-s)tX}\, \mathrm{i}t(Y - X)\, e^{\mathrm{i}stY}, $$
+$$ (d)/(ds)(e^{i(1-s)tX} e^{istY}) = e^{i(1-s)tX}\, it(Y - X)\, e^{istY}, $$
and the tracial 2-seminorm is unchanged by left and right unitary
multiplication, so integration and the triangle inequality give the
-tracial Duhamel bound $\|e^{\mathrm{i}tX} - e^{\mathrm{i}tY}\|_{2,\varphi} \le t\|X - Y\|_{2,\varphi}$.
+tracial Duhamel bound $\|e^{itX} - e^{itY}\|_{2,\varphi} \le t\|X - Y\|_{2,\varphi}$.
Together with exact equivariance, the norm limit, and the Gaussian
translation bound, every sequence of traces and indices with convergent
covariance satisfies
-$$ \limsup_{j \to \infty} \|\bar\alpha_h(V_{N_j}) - V_{N_j}\|_{2,\varphi_j} \le t\sqrt2(\sqrt\delta + 2\eta) < \eps/4, $$
+$$ limsup_{j \to ∞} \|\bar\alpha_h(V_{N_j}) - V_{N_j}\|_{2,\varphi_j} \le t\sqrt2(\sqrt\delta + 2\eta) < \eps/4, $$
-$$ \lim_{j \to \infty} |\varphi_j(V_{N_j}^\ell)| = \bigl|\mathbb E \exp(\mathrm{i}\ell t q_F)\bigr| \le (1 + t^2)^{-1/4} < \eps/4 $$
+$$ \lim_{j \to ∞} |\varphi_j(V_{N_j}^\ell)| = |\mathbb E \exp(i\ell t q_F)| \le (1 + t^2)^{-1/4} < \eps/4 $$
for $h \in H$ and $1 \le \ell \le m$, by the choices of the parameters.
@@ -560,7 +560,7 @@ Consequently, for all sufficiently large $N$, every extreme trace
$\varphi \in \mathcal T(C)$ satisfies
$\|\bar\alpha_h(V_N) - V_N\|_{2,\varphi} < \eps/2$ and
$|\varphi(V_N^\ell)| < \eps/2$ for $h \in H$ and $1 \le \ell \le m$. Were
-this false, some $N_j \to \infty$ and extreme traces $\varphi_j$ would fail
+this false, some $N_j \to ∞$ and extreme traces $\varphi_j$ would fail
one of these finitely many tests at tolerance $\eps/2$. The covariance
matrices $(\varphi_j(k_{N_j;g,g'}))_{g,g' \in J}$ lie in the compact set of
real positive semidefinite matrices with diagonal one, so a subsequence has
@@ -614,7 +614,7 @@ $ac = a^{1/2} c a^{1/2}$ when $c \ge 0$, using that $a$ commutes with $C$,
and traciality from $\tau(acd) = \tau(dac) = \tau(adc)$. Its norm is
$\tau(a)$. When $\tau(a) > 0$ its normalization is an element of
$\mathcal T(C)$, and when $\tau(a) = 0$ it vanishes, so the uniform
-approximately invariant unitary $V = \exp(\mathrm{i} t Q)$ from the
+approximately invariant unitary $V = \exp(i t Q)$ from the
preceding proposition gives
$$ |\tau(a V^\ell)| < \eps\, \tau(a) \le \eps \qquad (0 \le a \le 1,\ \tau \in \mathcal T_\omega(A),\ 1 \le \ell \le m,\ \tau(a) > 0), $$
@@ -632,7 +632,7 @@ continuous $f$, where $\mathbb T = \{z \in \mathbb C : |z| = 1\}$ and $\mu$
is normalized Haar measure.
Proof. Choose increasing finite sets $H_m \subset G$ with union $G$ and a
-sequence $a_1, a_2, \ldots$ dense in the positive unit ball of $A$ with
+sequence $a_1, a_2, ...$ dense in the positive unit ball of $A$ with
$a_1 = 1$. Apply the uniform-unitary proposition with
$(H, \eps, m) = (H_m, 1/m, m)$, and call the resulting exponential unitary
$V^{(m)} \in C$. It has a representative $(v^{(m)}_j)_j$ of unitaries in
@@ -660,21 +660,21 @@ and fixed by $\bar\alpha$. The last display, first for every $a_r$, then by
norm density for positive contractions, then by linearity for $a \in A$,
gives $\tau(a w^\ell) = 0$ for every $a \in A$, $\tau \in \mathcal T_\omega(A)$,
and $\ell \ge 1$. The same holds for negative powers because
-$\tau(a w^{-\ell}) = \overline{\tau(a^* w^\ell)}$, and the zeroth power has
+$\tau(a w^{-\ell}) = \tau(a^* w^\ell)bar$, and the zeroth power has
trace $\tau(a)$. Hence the identity holds for trigonometric polynomials,
and uniform approximation on $\mathbb T$ together with
-$|\tau(a f(w))| \le \|a\| \|f\|_\infty$ proves it for every continuous $f$.
+$|\tau(a f(w))| \le \|a\| \|f\|_∞$ proves it for every continuous $f$.
Proposition. The action $\alpha$ has equivariant uniform property Gamma,
and its projections can be chosen to sum to $1$.
Proof. Fix $k \ge 2$ and let $w = [(w_j)]$ be the unitary just constructed,
represented by unitaries $w_j \in A$. Partition $\mathbb T$ into $k$
-half-open arcs $I_1, \ldots, I_k$ of Haar measure $1/k$ and write
+half-open arcs $I_1, ..., I_k$ of Haar measure $1/k$ and write
$\chi_i = 1_{I_i}$. Choose continuous functions
$f_i^{(r)} : \mathbb T \to [0,1]$ with
-$$ e_r := \max_{1 \le i \le k} \|f_i^{(r)} - \chi_i\|_{L^2(\mu)} \longrightarrow 0, $$
+$$ e_r := \max_{1 \le i \le k} \|f_i^{(r)} - \chi_i\|_{L^2(\mu)} → 0, $$
for instance by replacing each indicator near its two endpoints by linear
ramps whose total lengths tend to zero. Fix $r$ and write $f_i = f_i^{(r)}$,
@@ -682,7 +682,7 @@ $e = e_r$. Pointwise bounds and the triangle inequality give
$$ \|f_i^2 - f_i\|_{L^2(\mu)} \le e, \qquad \|f_i f_j\|_{L^2(\mu)} \le 2e \ \ (i \ne j), $$
-$$ \Bigl\|\sum_i f_i - 1\Bigr\|_{L^2(\mu)} \le k e, \qquad \Bigl|\int_{\mathbb T} f_i\, d\mu - \frac1k\Bigr| \le e. $$
+$$ \Bigl\|\sum_i f_i - 1\Bigr\|_{L^2(\mu)} \le k e, \qquad |\int_{\mathbb T} f_i\, d\mu - \frac1k| \le e. $$
The first uses $|f_i^2 - f_i| \le |f_i - \chi_i|$ almost everywhere; the
second expands
@@ -698,10 +698,10 @@ moduli of the functions above, gives the corresponding 2-norm bounds for
the $y_i^{(r)}$ uniformly over $\tau \in \mathcal T_\omega(A)$, and for
every positive contraction $a \in A$ it also gives
-$$ \Bigl|\tau(a y_i^{(r)}) - \frac{\tau(a)}{k}\Bigr| = \tau(a) \Bigl|\int_{\mathbb T} f_i^{(r)}\, d\mu - \frac1k\Bigr| \le e_r. $$
+$$ |\tau(a y_i^{(r)}) - (\tau(a))/(k)| = \tau(a) |\int_{\mathbb T} f_i^{(r)}\, d\mu - \frac1k| \le e_r. $$
Represent $y_i^{(r)}$ by $f_i^{(r)}(w_j)$, and use $H_r$ and
-$a_1, \ldots, a_r$ from the preceding proof. For fixed $r$ the
+$a_1, ..., a_r$ from the preceding proof. For fixed $r$ the
coordinate-selection lemma gives a coordinate $j(r) \ge r$ such that the
positive contractions $y_{i,r} = f_i^{(r)}(w_{j(r)})$ satisfy, for all
indicated indices,
@@ -712,7 +712,7 @@ $$ \Bigl\|\sum_i y_{i,r} - 1\Bigr\|_{2,u} < k e_r + 1/r, $$
$$ \|[y_{i,r}, a_s]\|_{2,u} < 1/r \quad (s \le r), \qquad \|\alpha_h(y_{i,r}) - y_{i,r}\|_{2,u} < 1/r \quad (h \in H_r), $$
-$$ \sup_{\sigma \in \mathcal T(A)} \Bigl|\sigma(a_s y_{i,r}) - \frac{\sigma(a_s)}{k}\Bigr| < e_r + 1/r \quad (s \le r). $$
+$$ \sup_{\sigma \in \mathcal T(A)} |\sigma(a_s y_{i,r}) - (\sigma(a_s))/(k)| < e_r + 1/r \quad (s \le r). $$
This is a coordinate choice made after $f_i^{(r)}$ is fixed, so it needs no
uniform continuity modulus, as $r$ varies, for these increasingly sharp arc
@@ -735,19 +735,19 @@ a tracial state, and faithfulness of every trace follow from nuclearity,
stable finiteness, simplicity, and the quasitrace theorem. The last
proposition supplies equivariant uniform property Gamma, so all hypotheses
of the absorption criterion hold and $\alpha$ and
-$\beta = \alpha \otimes \mathrm{id}_Z$ are cocycle conjugate. The exact
+$\beta = \alpha ⊗ id_Z$ are cocycle conjugate. The exact
orientation of the equations is fixed as follows.
An isomorphism $\Phi : A \to B$ is automatically unital, being surjective
between unital algebras. Put $\gamma_g = \Phi \alpha_g \Phi^{-1}$. If
cocycle conjugacy is supplied in the form
-$\gamma_g = \mathrm{Ad}(u_g) \beta_g$ for a $\beta$-cocycle $u$, then the
+$\gamma_g = Ad(u_g) \beta_g$ for a $\beta$-cocycle $u$, then the
two displayed equations of the theorem follow directly. In the reverse
-orientation, suppose $\beta_g = \mathrm{Ad}(v_g) \gamma_g$ with
+orientation, suppose $\beta_g = Ad(v_g) \gamma_g$ with
$v_{gh} = v_g \gamma_g(v_h)$. The unitaries lie in $B$, whose multiplier
algebra is $B$ itself. Set $u_g = v_g^*$. Then
-$$ u_g \beta_g(u_h) = v_g^* v_g \gamma_g(v_h^*) v_g^* = \gamma_g(v_h^*) v_g^* = v_{gh}^* = u_{gh}, \qquad \mathrm{Ad}(u_g) \beta_g = \gamma_g. $$
+$$ u_g \beta_g(u_h) = v_g^* v_g \gamma_g(v_h^*) v_g^* = \gamma_g(v_h^*) v_g^* = v_{gh}^* = u_{gh}, \qquad Ad(u_g) \beta_g = \gamma_g. $$
Either orientation therefore gives the required $\beta$-cocycle, and the
identity relation $u_e = u_e^2$ together with unitarity forces $u_e = 1$.