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% XI-F.tex
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%
% Scope:
% Two gates for the classical cubic Einstein response named in XI-E:
%   F1  admission of C_3 into XI-E's polynomial Hadamard algebra;
%   F2  the gauge-fixing companion of the cubic variation;
%   F3  the plateau sum of the second-order variations;
%   F4  what the sum is not.
%
% Corrections to the production sheet (recorded in the text):
% 1. The admission obstruction is not finite rank. It is a timelike
%    conormal covector at the initial surface, produced by zero
%    Cauchy data for the second metric coefficient together with an
%    unswitched, unramped cubic source. F1 is proved obstructed for
%    the frozen representative; the on-shell class is left open.
% 2. The gauge-fixing companion is the retarded response to 2D^*Ds.
%    It equals K zeta_gf with zeta_gf=-E_0^R Ds, pure gauge with zero
%    data, and pairs to zero on the plateau. It is not -I.
% 3. XI-E's by-hand co-transformation and the covariant part of the
%    cubic response are one mechanism. The sheet's sum
%    delta_split + delta_0 C_3 + delta_gf = 0 + I + 0 counts it twice.
%    The corrected ledger is -I + I + 0 + 0 + 0 = 0.
% 4. The quadratic flow term (1/2)L_xi K xi enters the cubic response
%    through J_3[K xi] = -A((1/2)L_xi K xi); it is not added by hand.
% 5. The second-order parameter selected by gauge fixing is not in
%    g_U; the resulting remainder is a pure switching term, with no
%    ramp contribution, vanishing when J^-(supp f) cap J^+(supp xi)
%    lies in the plateau.
% 6. The identity is stated with the Einstein-shell term
%    P E_0^R L^dens_xi(A gamma) retained and named; it vanishes when
%    A gamma = 0 on U, which includes the witness.
%
% Compile hygiene: no redefinition of predefined macros (XI-B's
% \newcommand{\AA} would not compile); no theorem-header hacks.
%
% No interacting differential, quantum retarded product of the cubic
% source, mixed loop, state, sharp-width limit, or Einstein-jet repair.
%
% No successful compilation, mechanized verification, independent
% referee review, or journal acceptance is asserted.
%=====================================================================

\documentclass[11pt,a4paper]{article}

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\newcommand{\R}{\mathbb R}
\newcommand{\C}{\mathbb C}
\newcommand{\dd}{\,\mathrm d}
\newcommand{\eps}{\varepsilon}
\newcommand{\MT}{M_T}
\newcommand{\MTo}{M_T^\circ}
\newcommand{\sig}{\sigma_\eps}
\newcommand{\PP}{\mathcal P}
\newcommand{\RR}{\mathcal R}
\newcommand{\Lie}{\mathcal L}
\newcommand{\Ldens}{\mathcal L^{\mathrm{dens}}_\xi}
\newcommand{\ga}{\mathfrak g_U}
\newcommand{\Gp}{\mathcal G_U}
\newcommand{\Afree}{\mathscr A_0}
\newcommand{\Ealg}{\mathscr E_H}
\newcommand{\Fpol}{\mathscr F_{\mathrm{mc,pol}}}
\newcommand{\Csol}{\mathscr C_{\mathrm{sol}}}
\newcommand{\ER}{\mathsf E_0^{\mathrm R}}
\newcommand{\EA}{\mathsf E_0^{\mathrm A}}
\newcommand{\ERm}{\mathsf E_m^{\mathrm R}}
\newcommand{\EAm}{\mathsf E_m^{\mathrm A}}
\newcommand{\Ggr}{G_{\mathrm{gr}}^{\mathrm R}}
\newcommand{\Pfree}{P_m}
\newcommand{\sfree}{s_0}
\newcommand{\Xone}{\mathsf X_1}
\newcommand{\Xtwo}{\mathsf X_2}
\newcommand{\Bcal}{\mathcal B}
\newcommand{\Tcal}{\mathcal T}
\newcommand{\Aone}{\mathcal A_1}
\newcommand{\Atwo}{\mathcal A_2}
\newcommand{\Atwothree}{\mathcal A_2^{(3)}}
\newcommand{\Cthree}{\mathcal C_3}
\newcommand{\Hcal}{\mathcal H}
\newcommand{\Jcal}{\mathcal J}
\newcommand{\Vone}{\mathsf V_{1,g}}
\newcommand{\Vtwo}{\mathsf V_{2,g}}
\newcommand{\Dfset}{\mathcal D_f}
\newcommand{\Vp}{\widetilde V_+}
\newcommand{\Vm}{\widetilde V_-}
\newcommand{\sxi}{s_\xi}
\newcommand{\zgf}{\zeta_{\mathrm{gf}}}
\newcommand{\dgf}{\delta_{\mathrm{gf}}}
\newcommand{\pair}[2]{\left\langle #1,#2\right\rangle}
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  \par\medskip\noindent
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    \dimexpr\linewidth-2\fboxsep-2\fboxrule\relax}
  \textbf{#1}\par\smallskip #2
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  \par\medskip
}

\title{\textbf{Landmark XI-F}\\[0.4em]
Admission of the cubic Einstein response,\\
and the plateau sum of the second-order variations}
\author{Ngo Cheung}
\date{}

\usepackage{tikz}
\begin{document}
\maketitle

\begin{abstract}
Landmark XI-E named, and excluded from its release, the classical
cubic Einstein response $u_3=\PP\ER(2\Hcal_2[\gamma])$ and its
scalar-completed insertion $\Cthree=\Aone[u_3;\phi]$. We decide two
gates for that object at fixed regulator width, in the normalization
$\Ggr=-\PP\ER$.

\emph{Admission.} The second metric coefficient carries the frozen
zero Cauchy data on $\Sigma$, and the Einstein--Hilbert density
carries neither the switch $g$ nor the ramp $\sig$. The slab kernel
of $\Cthree$ therefore has the form $\theta(y^0)\beta(y)\,j_3(y;\cdot,\cdot)$:
a sharp onset at the initial surface in a metric slot. For every
frozen switch and every mass we exhibit admissible observation data
for which this kernel has a timelike conormal covector $\pm\dd t$ in
its wavefront set, so it leaves the polynomial microcausal class of
XI-E. The admission map of XI-E does not apply to $\Cthree$. The
failure is not the finite-rank mismatch and not a loop; it is the
sharp-Cauchy singularity of VII-B, now in the gravitational slot,
which the ramp regulates only in the coordinate operator. Whether the
free-shell restriction of $\Cthree$ has some other microcausal
representative is not decided.

\emph{Plateau sum.} From XI-B's gauge fermion, the order-$\kappa$
variation of the de Donder term under the single-field law is
$2D^*Ds$, with divergence $-\Box Ds$; its retarded response through
the frozen inverse is the pure gauge $-2\RR\ER Ds=K\zgf$, with
$\zgf=-\ER Ds$ the de Donder second-order parameter. Hence
$u_3[\gamma+K\xi]-u_3[\gamma]=\sxi+K\zgf[\sxi]+\PP\ER\Ldens(A\gamma)$,
$\sxi=\Lie_\xi\gamma+\tfrac12\Lie_\xi K\xi$: the complete second-order
metric law of X-A, with $\zeta$ selected by gauge fixing. The
cubic-completed second coefficient then shifts, for a free scalar and
$A\gamma=0$ on $U$, by $\Aone[K\zgf;\phi_0]$: a pure switching term
carrying $1-g$ or $\partial g$, with no ramp term, vanishing whenever
$J^-(\supp f)\cap J^+(\supp\xi)$ lies in the plateau. On the XI-E
witness the ledger reads $-I$ (held fixed) $+I$ (covariant cubic)
$+0$ (gauge-fixing response) $+0+0$ (quadratic terms) $=0$. The
production sheet's literal sum $\delta_{\mathrm{split}}+\delta_0\Cthree+\dgf
=0+I+0$ double counts: XI-E's by-hand co-transformation and the
covariant part of the cubic response are one mechanism. The corrected
plateau sum vanishes; $\dgf$ is not $-I$, it is $0$.

Neither result constructs an interacting differential, a quantum
retarded product of the cubic source, a loop value, a sharp limit,
or an Einstein-jet repair.
\end{abstract}

\begin{figure}[ht]
\centering
\begin{tikzpicture}[x=1cm,y=1cm]
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (a) at (0,0) {Frozen cubic representative};
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (b) at (5,0) {Admission gate};
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (c) at (10,0) {A repaired class};
\node[draw,dashed,rounded corners,align=center,text width=9.6cm,font=\small,inner sep=3pt] (s) at (5,-2.35) {Gate 1 is proved obstructed for that representative, not for every later insertion.};
\draw[->] (a) -- (b);
\draw[->] (b) -- (c);
\draw[->] (b) -- (s);
\end{tikzpicture}
\caption{The frozen representative is obstructed. The three boxes name objects this manuscript keeps separate. The dashed box is the stated stop. Not a proof, and not an admission of a quantum coefficient.}
\label{fig:scope-XI-F}
\end{figure}

\begin{figure}[ht]
\centering
\begin{tikzpicture}[x=1cm,y=1cm]
\node[draw,rounded corners,align=center,text width=4.3cm,font=\small,inner sep=3pt] (a) at (0,0) {Frozen cubic representative};
\node[draw,rounded corners,align=center,text width=4.3cm,font=\small,inner sep=3pt] (b) at (6.4,0) {A repaired class};
\node[draw,dashed,rounded corners,align=center,text width=9.6cm,font=\small,inner sep=3pt] (s) at (3.2,-2.35) {Gate 1 is proved obstructed for that representative, not for every later insertion.};
\draw[->] (a) -- (s);
\draw[->] (b) -- (s);
\end{tikzpicture}
\caption{The frozen representative is obstructed. The boxes name objects this manuscript keeps separate. The dashed box is the stated stop. Not a proof, and not an admission of a quantum coefficient.}
\label{fig:split-XI-F}
\end{figure}

\begin{figure}[ht]
\centering
\begin{tikzpicture}[x=1cm,y=1cm]
\node[draw,rounded corners,align=center,text width=7.2cm,font=\small,inner sep=3pt] (a) at (0,0) {Frozen cubic representative};
\node[draw,rounded corners,align=center,text width=7.2cm,font=\small,inner sep=3pt] (b) at (0,-1.7) {Admission gate};
\node[draw,rounded corners,align=center,text width=7.2cm,font=\small,inner sep=3pt] (c) at (0,-3.4) {A repaired class};
\node[draw,dashed,rounded corners,align=center,text width=7.2cm,font=\small,inner sep=3pt] (s) at (0,-5.2) {Gate 1 is proved obstructed for that representative, not for every later insertion.};
\draw[->] (a) -- (b);
\draw[->] (b) -- (c);
\draw[->] (c) -- (s);
\end{tikzpicture}
\caption{Reading downward is not a transfer. The boxes name objects this manuscript keeps separate. The dashed box is the stated stop. Not a proof, and not an admission of a quantum coefficient.}
\label{fig:chain-XI-F}
\end{figure}

\begin{figure}[ht]
\centering
\begin{tikzpicture}[x=1cm,y=1cm]
\node[draw,rounded corners,align=center,text width=4.2cm,font=\small,inner sep=3pt] (a) at (0,0) {Frozen cubic representative};
\node[align=center,font=\small] (m) at (5.2,0) {not the same object};
\node[draw,rounded corners,align=center,text width=4.2cm,font=\small,inner sep=3pt] (b) at (10.4,0) {A repaired class};
\node[draw,dashed,rounded corners,align=center,text width=9.6cm,font=\small,inner sep=3pt] (s) at (5.2,-2.35) {Admission gate. Gate 1 is proved obstructed for that representative, not for every later insertion.};
\draw (a) -- (m);
\draw (m) -- (b);
\draw[->] (m) -- (s);
\end{tikzpicture}
\caption{Frozen cubic representative is not A repaired class. The boxes name objects this manuscript keeps separate. The dashed box is the stated stop. Not a proof, and not an admission of a quantum coefficient.}
\label{fig:pair-XI-F}
\end{figure}

\begin{figure}[ht]
\centering
\begin{tikzpicture}[x=1cm,y=1cm]
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (a) at (0,0) {Named: Frozen cubic representative};
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (b) at (5,0) {Used here: Admission gate};
\node[draw,rounded corners,align=center,text width=3.15cm,font=\small,inner sep=3pt] (c) at (10,0) {Not claimed: A repaired class};
\node[draw,dashed,rounded corners,align=center,text width=9.6cm,font=\small,inner sep=3pt] (s) at (5,-2.5) {Gate 1 is proved obstructed for that representative, not for every later insertion.};
\draw[->] (a) -- (b);
\draw[->] (b) -- (c);
\draw[->] (b) -- (s);
\end{tikzpicture}
\caption{Three statuses stay separate. The boxes name objects this manuscript keeps separate. The dashed box is the stated stop. Not a proof, and not an admission of a quantum coefficient.}
\label{fig:gate-XI-F}
\end{figure}

Figure~\ref{fig:split-XI-F} records one view of the same separation. Figure~\ref{fig:chain-XI-F} records one view of the same separation. Figure~\ref{fig:pair-XI-F} records one view of the same separation. Figure~\ref{fig:gate-XI-F} records one view of the same separation. The drawings add no hypothesis.


Figure~\ref{fig:scope-XI-F} records that separation.
The drawing adds no hypothesis.



\scopebox{Release: two gates, three endings, worst ending governs}{%
\begin{description}[leftmargin=1.2em,itemsep=2pt]
\item[Gate 1 (F1, admission): \textbf{Proved obstructed}.]
The frozen representative of $\Cthree$ has a timelike conormal
covector at $\Sigma$ in a metric slot and is not in $\Fpol$. XI-E's
admission map does not apply. The on-shell class question is open.
\item[Gate 2 (F2--F3, plateau sum): \textbf{Constructed}.]
The de Donder companion is computed from XI-B's fermion with the
coefficient $-1$; the finite transformation of $u_3$ is the X-A
second-order law with $\zeta=\zgf$; the plateau sum is zero when
$A\gamma=0$ on $U$, with the off-plateau remainder a switching term
supported in $(\supp\dd g\cup\supp((1-g)f))\cap J^+(\supp\xi)$.
\end{description}
Overall ending: \textbf{Proved obstructed} (Gate 1). No quantum
version of the plateau sum exists in $\Ealg$, because $\Cthree$ is not
admitted. No $\widehat s_{\mathrm{int}}$, loop, $\eps\to0$ limit, or
repair of $\Jcal_g(\phi_m)$.}

\tableofcontents

%=====================================================================
\section{Scope, the two gates, and the corrections}
\label{sec:scope}
%=====================================================================

XI-E closed three routes and left one object outside all of them:
the cubic Einstein response $u_3$ and its insertion $\Cthree$
\cite{XIE}. XI-E computed the classical variation of $\Cthree$ on a
witness and found a second nonzero number $I$, distinct from the $I$
that its split cancellation had already removed. It did not admit
$\Cthree$ to its Hadamard algebra, and it did not compute the
gauge-fixing companion of the cubic variation. Those are the two gates
here.

\begin{enumerate}[label=\textbf{F\arabic*.}]
\item Admit $\Cthree$ into the polynomial on-shell Hadamard algebra
$\Ealg$ of XI-E, or exhibit a wavefront direction that leaves its
polynomial microcausal class.
\item Compute the order-$\kappa$ variation of the de Donder term under
the single-field transformation law, from XI-B's gauge fermion, and its
retarded response through $\Ggr=-\PP\ER$.
\item Assemble the second-order variations on the XI-E witness and
decide whether their sum vanishes on the plateau, with the off-plateau
support stated.
\item Say what the result is not.
\end{enumerate}

The three endings of the series apply to each gate: \emph{Constructed},
\emph{Proved obstructed}, \emph{Unresolved}. The worst ending governs
the release.

\subsection{Six corrections to the production sheet}

The sheet anticipated an admission proof by composition of retarded
kernels, a gauge-fixing companion equal to $-I$, and a three-term sum
$\delta_{\mathrm{split}}+\delta_0\Cthree+\dgf$. Each of these must be
corrected before the gates can be decided.

\begin{enumerate}
\item The source $J_3=2\Hcal_2[\gamma]$ is local, unswitched and
unramped, and the second coefficient has zero data on $\Sigma$. Its
retarded response is $\ER J_3$ with the zero-data inverse, which
truncates the source at $t=0$. The resulting kernel has a sharp onset
at $\Sigma$ in a metric slot. That onset, not the finite-rank
mismatch, is the obstruction (Section~\ref{sec:F1}).

\item The gauge-fixing companion is the retarded response to the
order-$\kappa$ de Donder variation $2D^*D\sxi$. It equals
$K\zgf[\sxi]$ with $\zgf=-\ER D\sxi$: pure gauge, zero data, supported
in $J^+(\supp\xi)$. Its $\Aone$-pairing on the plateau is zero, not
$-I$ (Section~\ref{sec:F2}).

\item XI-E's cancellation theorem restored $\gamma\mapsto\gamma+\kappa\Lie_\xi\gamma$
by hand in a parametrization with an external second coefficient $k$.
Once $k=u_3[\gamma]$ is generated by the response, the covariant part
of $u_3[\gamma+K\xi]-u_3[\gamma]$ \emph{is} that shift. Adding
$\delta_{\mathrm{split}}=0$, which already contains the by-hand $+I$,
to $\delta_0\Cthree=I$ counts the same term twice
(Section~\ref{sec:F3}).

\item The quadratic flow term $\tfrac12\Lie_\xi K\xi$ of the single-field
law is supplied by the response through the flatness identity
$J_3[K\xi]=-A(\tfrac12\Lie_\xi K\xi)$. It is not added separately.

\item The second-order parameter selected by gauge fixing is not in
$\ga$. Its support is $J^+(\supp\xi)\cap\MT$. The resulting remainder
is a switching term of X-A's and VI's type, with no ramp layer, and it
vanishes under an explicit causal plateau condition.

\item The identity is stated with the Einstein-shell term
$\PP\ER\Ldens(A\gamma)$ retained. On the gauge-fixed free shell
$A\gamma=-2D^*b$; the term vanishes when $D^*b=0$ on $U$, which holds
for the witness and for every linearized Einstein solution. XI-A's
distinction between the gauge-fixed and the Einstein shell is not
erased.
\end{enumerate}

\subsection{Non-imports}

X-E's normalization $\Delta_{\mathrm R}=-4\PP\ER$ with dressing $-2$,
and X-F's three-tree cancellation in that normalization, are not
premises. Their mechanism, that a held-fixed split can be a
truncation, is the same mechanism that appears in
Section~\ref{sec:F3}; no factor, flat-gauge residual, or sum-zero
lemma is copied. VII-C's word, reflected residue, and hypotheses
(E1)--(E4) stay out. The empty fixed-input Einstein jet
$\Jcal_g(\phi_m)=\varnothing$ remains XI-A's result \cite{XIA}.

%=====================================================================
\section{Copied sheet}
\label{sec:sheet}
%=====================================================================

\subsection{Conventions}

\[
 \MT=[0,T]\times\R^3,\qquad \MTo=(0,T)\times\R^3,\qquad \Sigma=\{t=0\},
\]
\[
 \eta=\diag(1,-1,-1,-1),\qquad \Box=\partial_t^2-\Delta,\qquad
 \Pfree=\Box+m^2,\qquad m\geq0.
\]
Indices are moved with $\eta$; parentheses include the factor
$\tfrac12$. Classical fields are smooth on a neighbourhood of the
closed slab; no spatial decay is imposed. The ramp
$\sig(t)=\chi(t/\eps)$, $0<\eps<T$, with the explicit $\chi$ of X-A,
satisfies $\sig=0$ on $\{t\leq0\}$, $\sig=1$ on $\{t\geq\eps\}$,
$\sig>0$ on $\{t>0\}$, and $\chi(1-s)=1-\chi(s)$. The switch
$g\in C_c^\infty(\MTo;[0,1])$ has $P_g=\Int\{g=1\}\neq\varnothing$.
The plateau $U$ is open, relatively compact, with
$\overline U\subset P_g\cap\{\eps<t<T\}$, and $\ga=C_c^\infty(U;TM)$.
The observation test is a real $f\in C_c^\infty(\MTo)$ with
\[
 \Dfset=J^-(\supp f)\cap\MT,
\]
a compact set that is closed under $J^-$ inside $\MT$.

For a symmetric tensor $r$,
\[
 \PP r=r-\tfrac12\eta\tr_\eta r,\qquad
 D^\mu r=\partial_\nu(\PP r)^{\nu\mu},\qquad
 (Kv)_{\mu\nu}=\partial_\mu v_\nu+\partial_\nu v_\mu,\qquad
 \RR=\tfrac12K,
\]
\[
 (D^*v)_{\mu\nu}=-\partial_{(\mu}v_{\nu)}+\tfrac12\eta_{\mu\nu}\partial_\rho v^\rho,
 \qquad
 \PP^2=\id,\qquad \PP D^*=-\RR,\qquad D\RR=\tfrac12\Box,\qquad
 DK\xi=\Box\xi .
\]
With $A=2G_{\mathrm{lin}}$,
\begin{equation}
 A+2D^*D=-\Box\PP,\qquad AK\xi=0,\qquad
 \Ggr=-\PP\ER,\qquad \Ggr D^*=\RR\ER .
 \label{eq:algebra}
\end{equation}
Here $\ER$ is the zero-initial-data inverse of $\Box$ on the slab,
$\EA$ the zero-final-data inverse, and $\ERm,\EAm$ the Klein--Gordon
analogues. For $a\in C_c^\infty(\MTo)$ and $s$ smooth on $\MT$,
$\int a\,\ERm s=\int(\EAm a)\,s$ (X-A, transposition lemma); the proof
only needs $\EAm a$ to vanish near $t=T$, so it applies verbatim to
$a$ smooth on $\MT$ with $\supp a\subset\Dfset$. For $s$ smooth with
zero Cauchy data and $\supp s\subset\{t>0\}$, $\ER\Box s=s$ and
$\ER\partial_\mu s=\partial_\mu\ER s$.

\begin{lemma}[Inverse of $A$ on compact plateau sources]
\label{lem:GA}
For $s$ smooth, compactly supported in $U$,
\begin{equation}
 \Ggr As=s-2\RR\ER Ds .
 \label{eq:GA}
\end{equation}
\end{lemma}
\begin{proof}
$\Ggr As=(-\PP\ER)(-\Box\PP s)+(-\PP\ER)(-2D^*Ds)
=\PP\PP s+2\PP D^*\ER Ds=s-2\RR\ER Ds$, using \eqref{eq:algebra},
$\ER\Box s=s$, and $\ER D^*=D^*\ER$ on $Ds$, which has zero data.
\end{proof}

\subsection{Coordinate operator, first and second coefficients}

\[
 a_1^{\mu\nu}[r]=\tfrac12\eta^{\mu\nu}\tr_\eta r-r^{\mu\nu},\qquad
 b_1[r]=\tfrac12\tr_\eta r,\qquad
 C^\mu[r]=-\partial_\alpha a_1^{\alpha\mu}[r]=D^\mu r,
\]
\begin{equation}
 \Xone[r]=-\ER\partial_\alpha\bigl(\sig a_1^{\alpha\cdot}[r]\bigr)
 =\ER\bigl(\sig Dr-\sig'a_1^{0\cdot}[r]\bigr).
 \label{eq:X1}
\end{equation}
\[
 \Vone[r]u=\partial_\mu\bigl(ga_1^{\mu\nu}[r]\partial_\nu u\bigr)+gm^2b_1[r]u,
 \qquad
 \Aone[r;\phi]=\int_{\MT}f\bigl(-\ERm\Vone[r]\phi-\Xone[r]\cdot\partial\phi\bigr)\dd^4x .
\]
$\Atwo^{\mathrm{sc}}[H,k;\phi]$ is X-A's complete on-shell second
coefficient, written out in XI-D: with $\rho_1=-\ERm\Vone[H]\phi$,
$\rho_2=\ERm\Vone[H]\ERm\Vone[H]\phi-\ERm\Vtwo[H,k]\phi$,
\[
 \Atwo^{\mathrm{sc}}[H,k;\phi]
 =\int f\Bigl[\rho_2-\Xone[H]\cdot\partial\rho_1
 +(\Xone[H]\cdot\partial\Xone[H]-\Xtwo[H,k])\cdot\partial\phi
 +\tfrac12\Xone^\mu[H]\Xone^\nu[H]\partial_\mu\partial_\nu\phi\Bigr]\dd^4x .
\]
Two copied facts about it:
\begin{align}
 \Atwo^{\mathrm{sc}}[H,k+r;\phi]-\Atwo^{\mathrm{sc}}[H,k;\phi]
 &=\Aone[r;\phi]
 \qquad\text{(XI-D, affine lemma)},
 \label{eq:affine}\\
 \Aone[h';\phi_0]=\Aone[h;\phi_0],\quad
 \Atwo^{\mathrm{sc}}[h',k';\phi_0]&=\Atwo^{\mathrm{sc}}[h,k;\phi_0]
 \qquad\text{(X-A, Theorem (v))},
 \label{eq:XAv}
\end{align}
for every free $\phi_0$, every smooth $(h,k)$, and
\[
 h'=h+K\xi,\qquad
 k'=k+\Lie_\xi h+K\zeta+\tfrac12\Lie_\xi K\xi,\qquad \xi,\zeta\in\ga .
\]
The free input $\phi_0$ is not transformed in \eqref{eq:XAv}; it is
held fixed, exactly as XI-E held the scalar fixed in its cubic
variation.

\subsection{Free multiplet, algebra, and the inherited symbols}

The independent multiplet is $(\gamma,\phi,c,\bar c,b)$ with the free
rule $\sfree\gamma=\RR c$, $\sfree\phi=\sfree c=\sfree b=0$,
$\sfree\bar c=ib$. The gauge fermion of XI-B is
\begin{equation}
 \Psi=-i\int_{\MT}\bar c_\mu\bigl(2D^\mu\gamma-b^\mu\bigr)\dd^4x,
 \qquad
 \sfree\Psi=\int_{\MT}\bigl(2b_\mu D^\mu\gamma-b_\mu b^\mu+i\bar c_\mu\Box c^\mu\bigr)\dd^4x,
 \label{eq:fermion}
\end{equation}
and elimination of $b=D\gamma$ gives $S_{\mathrm{gf}}=\int D_\nu\gamma D^\nu\gamma$
with Euler derivative $E_{\mathrm{gf}}[\gamma]=2D^*D\gamma$
\cite{XIB,XIA}. The free shell $\Csol$ is $-\Box\PP\gamma=0$,
$b=D\gamma$, $\Pfree\phi=0$, $\Box c=\Box\bar c=0$.

XI-E's Route~1 constructed the polynomial on-shell Hadamard algebra
$\Ealg=(\Fpol^{\mathrm{sol}}[[\hbar,\kappa]],\star_H)$ with block data
$H_{\gamma\gamma}=-\PP h_0$, $H_{\gamma b}=D_yH_{\gamma\gamma}$,
$H_{\phi\phi}=-h_m$, $H_{c\bar c}=-ih_0$, graded antisymmetric part
equal to XI-B's causal matrix, and no state selected. Its domain is:

\begin{definition}[XI-E's polynomial microcausal domain, copied]
\label{def:domain}
$\Fpol$ consists of finite graded polynomials
$F(\Phi)=\sum_{n}\pair{u_n}{\Phi^{\otimes n}}$ on ambient
configurations on $M=\R^4$, with compact, graded symmetric
distributional kernels $u_n$ on $M^n$ satisfying
\begin{equation}
 \WF(u_n)\cap\bigl(\Vp^{\,n}\cup\Vm^{\,n}\bigr)=\varnothing,
 \label{eq:mc}
\end{equation}
where $\Vp,\Vm$ are the closed future and past causal covector cones
with zero included, and the total zero covector is never a wavefront
point. Field indices are finite and do not change the criterion.
Admission is kernel inclusion in $\Fpol$ followed by restriction to
$\Csol$:
$Q_H(F)=[F|_{\Csol}]\in\Ealg$. Slab functionals are viewed on $M$
through their slab restriction; for the inherited symbols the ramp is
flat at $t=0$, so no boundary conormal appears.
\end{definition}

The inherited symbols $\Bcal_f=-\int f\Xone[\gamma]\cdot\partial\phi$
and $\Tcal(f,g)[\phi]=\int f(\Xone[r_g[\phi]])\cdot\partial\phi$,
$r_g=-\tfrac12\PP\ER(gT_0[\phi])$, are admitted in $\Ealg$; the
physical one-graviton response of $\Bcal_f$ is $-\Tcal$ at coupling
degree $\kappa^2$ \cite{XIC}. Their admission is not reopened here.

\subsection{The cubic response and the witness}

XI-A's unswitched action $S_{\mathrm{EH}}=-\frac2{\kappa^2}\int\sqrt{-q}R[q]$
with $q=\eta+\kappa\gamma$ gives
$\sqrt{-q}\,G^{\mu\nu}(q)=\kappa\Hcal_1+\kappa^2\Hcal_2+\kappa^3\Hcal_3+O(\kappa^4)$,
$\Hcal_1=G_{\mathrm{lin}}(\gamma)=\tfrac12A\gamma$, with the finite
formulas of XI-A's appendix. The cubic vertex has metric Euler
derivative $J_3[\gamma]=2\Hcal_2[\gamma]$, a quadratic local
differential polynomial. XI-E defined
\begin{equation}
 u_3[\gamma]=-\Ggr J_3[\gamma]=\PP\ER\bigl(2\Hcal_2[\gamma]\bigr),
 \qquad
 \Cthree(f,g)[\gamma,\phi]=\Aone[u_3[\gamma];\phi],
 \label{eq:C3}
\end{equation}
of field degree $(2,1)$, and proved, for $\delta_0\gamma=K\xi$, $\xi\in\ga$,
\begin{equation}
 \delta_0J_3[\gamma]=\Ldens(A\gamma)-A(\Lie_\xi\gamma),
 \qquad
 \delta_0u_3=\Lie_\xi\gamma-2\RR\ER D\Lie_\xi\gamma\quad\text{if }A\gamma=0,
 \label{eq:XIEvar}
\end{equation}
where $(\Ldens v)^{\mu\nu}=\xi^\rho\partial_\rho v^{\mu\nu}-v^{\rho\nu}\partial_\rho\xi^\mu
-v^{\mu\rho}\partial_\rho\xi^\nu+(\partial_\rho\xi^\rho)v^{\mu\nu}$.

The witness (XI-C, XI-D, XI-E): $m=0$,
\begin{equation}
 \gamma=t\eta,\qquad \phi=t^2+\tfrac13|\mathbf x|^2,\qquad
 \xi=a(t)\partial_t,\quad a\geq0,\ a\not\equiv0,\
 \supp a\subset(\eps,T),
 \label{eq:witness}
\end{equation}
in a causal cylinder on which $g=1$, with a compact spatial cutoff on
$\xi$ whose derivatives lie outside the observation dependence region,
the plateau containing $\supp\xi$, and $f\geq0$, $f\not\equiv0$
observed after $\supp a$. Then $\Box\phi=0$, $-\Box\PP\gamma=0$,
$b=D\gamma=(-2,0,0,0)$ is constant, $A\gamma=0$, and
\begin{equation}
 I:=\Aone[\Lie_\xi\gamma;\phi]
 =4\int f(t,\mathbf x)\int_0^t(t-s)a(s)\dd s\dd^4x>0,
 \qquad
 \delta_0\Cthree=I .
 \label{eq:I}
\end{equation}
XI-E also proved the split cancellation
$-\Aone[\Lie_\xi\gamma]+\Aone[\Lie_\xi\gamma]=0$ in the
$(h,\gamma,k)$ parametrization with an external $k$, and recorded
that the two $I$'s are different $I$'s. The two affine numbers,
$S_\eps(t)$ for the bare insertion and $\eps/2$ for the complete word,
are not touched here.

\subsection{Normalization refusal}

The coefficient of $\PP\ER$ is $-1$ throughout. Neither $-2\PP\ER$ nor
$-4\PP\ER$ is used, and no graviton two-point function is selected.

%=====================================================================
\section{F1: the cubic kernel at the initial surface}
\label{sec:F1}
%=====================================================================

\subsection{Kernel representation of the first coefficient}

\begin{lemma}[Smooth kernel of $\Aone$]
\label{lem:alpha}
Fix $f$, $g$, and a smooth $\phi$ on the slab. There is a smooth
symmetric contravariant tensor $\alpha=\alpha[f,g,\phi]$ on $\MT$ with
$\supp\alpha\subset\Dfset$ such that
\begin{equation}
 \Aone[r;\phi]=\int_{\MT}\alpha^{\rho\sigma}r_{\rho\sigma}\dd^4x
 \qquad\text{for every smooth }r .
 \label{eq:alpha}
\end{equation}
Explicitly, with $b=\EA(f\dd\phi)$, $b'=\EAm f$, and
$(C^*b)^{\rho\sigma}=-\partial^{(\rho}b^{\sigma)}+\tfrac12\eta^{\rho\sigma}\partial_\mu b^\mu$,
\begin{equation}
 \alpha^{\rho\sigma}
 =-\sig\,(C^*b)^{\rho\sigma}
 +g\Bigl[\tfrac12\eta^{\rho\sigma}\bigl(\partial^\mu b'\partial_\mu\phi-m^2\phi\,b'\bigr)
 -\partial^{(\rho}b'\,\partial^{\sigma)}\phi\Bigr].
 \label{eq:alphaexplicit}
\end{equation}
\end{lemma}

\begin{proof}
The coordinate term $-\int f\Xone[r]\cdot\partial\phi$ is $-\Jc(f\dd\phi)[r]$
in X-A's notation, whose kernel is $\sig C^*(\EA(f\dd\phi))$ by X-A's
kernel lemma; this gives the first term. For the scalar term,
transposition gives $\int f\ERm\Vone[r]\phi=\int b'\Vone[r]\phi$, and
integrating by parts in the divergence (legitimate because $g$ has
compact interior support),
\[
 -\int b'\Vone[r]\phi
 =\int g\,a_1^{\mu\nu}[r]\partial_\mu b'\partial_\nu\phi-\int gm^2b_1[r]\phi\,b' .
\]
Inserting $a_1^{\mu\nu}[r]=\tfrac12\eta^{\mu\nu}\tr r-r^{\mu\nu}$,
$b_1[r]=\tfrac12\tr r$, and symmetrizing gives the second term of
\eqref{eq:alphaexplicit}. Supports: $b,b'$ are supported in $\Dfset$,
and $\Dfset$ is past-closed in $\MT$.
\end{proof}

\begin{proposition}[Representation of $\Cthree$ and the onset at $\Sigma$]
\label{prop:beta}
Let $\beta:=\EA(\PP\alpha)$, a smooth symmetric tensor on $\MT$ with
$\supp\beta\subset\Dfset$. Then
\begin{equation}
 \Cthree(f,g)[\gamma,\phi]=\int_{[0,T]\times\R^3}\beta_{\mu\nu}(y)\,J_3^{\mu\nu}[\gamma](y)\dd^4y .
 \label{eq:C3beta}
\end{equation}
Viewed as a functional of ambient configurations through slab
restriction, the degree-$(2,1)$ kernel $u$ of $\Cthree$ is supported
in $\{y_1=y_2=y\in\Dfset\cap\{y^0\geq0\}\}\times\Dfset$ and has the
form
\begin{equation}
 u(y_1,y_2,x)=\int_{y^0\geq0}\widehat\beta_{\mu\nu}(y,x)\,j_3^{\mu\nu}(y;y_1,y_2)\dd^4y,
 \label{eq:ukernel}
\end{equation}
where $j_3$ is the constant-coefficient bilinear local kernel of
$J_3$ (a finite sum of products of derivatives of
$\delta(y-y_1)$ and $\delta(y-y_2)$) and $\widehat\beta$ is the
$\phi$-slot kernel of $\beta$. The factor $\theta(y^0)$ is forced:
the frozen Cauchy prescription gives the second coefficient zero
data on $\Sigma$, so $\ER$ truncates every source at $t=0$, and the
Einstein--Hilbert density carries no $g$ and no $\sig$ that could
make $J_3[\gamma]$ vanish near $\Sigma$.
\end{proposition}

\begin{proof}
$\Cthree=\int\alpha\cdot u_3=\int\alpha\cdot\PP\ER J_3$. Trace reversal
is self-adjoint under the $\eta$-contraction,
$\pair{\alpha}{\PP r}=\pair{\alpha}{r}-\tfrac12\tr\alpha\tr r=\pair{\PP\alpha}{r}$,
and transposition (applicable because $\supp\PP\alpha\subset\Dfset$
vanishes near $t=T$ and $\ER J_3$ has zero data) gives
\eqref{eq:C3beta}. The $y$-integral runs over the slab only, and
$J_3[\gamma](y)$ depends on the jet of $\gamma$ at $y$; this is
\eqref{eq:ukernel}. Compactness: $y\in\Dfset$, and the $\phi$-slot of
$\alpha$ is supported in $\Dfset$ by Lemma~\ref{lem:alpha}.
\end{proof}

The onset $\theta(y^0)$ is the sharp step $\theta(t)$ that X-A
replaced by $\sig$ in the coordinate operator (X-A, kernel lemma),
and that VII-B found to carry a timelike conormal covector. Here it
reappears in a metric slot, where the ramp does not act. Whether it
is harmless depends on whether the coefficient $\beta$ vanishes on
$\Sigma$. It does not.

\subsection{Two tools}

\begin{lemma}[Smearing]
\label{lem:smear}
Let $u$ be a compactly supported tensor-valued distribution on $M^3$
and $v,\psi$ smooth on $M$. Put $\ell:=\pair{u}{\,\cdot\otimes v\otimes\psi}$,
a compactly supported distribution on $M$. Then
\[
 \WF(\ell)\subset\{(y_1,p):\ \exists\,y_2,y_3:\ (y_1,p;y_2,0;y_3,0)\in\WF(u)\}.
\]
In particular, if $u$ satisfies \eqref{eq:mc} with $n=3$, then
$\WF(\ell)$ contains no nonzero covector in $\Vp\cup\Vm$.
\end{lemma}

\begin{proof}
Smooth multiplication by $v\otimes\psi$ does not enlarge the
wavefront set, and integration over $(y_2,y_3)$ of a compactly
supported distribution is the pushforward estimate of
\cite[Theorem~8.2.12]{Hormander}. If $(y_1,p;y_2,0;y_3,0)\in\WF(u)$
with $0\neq p\in\Vp$, then the triple lies in $\Vp^{\,3}$, contradicting
\eqref{eq:mc}; similarly for $\Vm$.
\end{proof}

\begin{lemma}[Homogeneous reduction of the cubic source]
\label{lem:ADM}
Let $\gamma_{0\mu}=0$ and $\gamma_{ij}=\gamma_{ij}(t)$ on an open set
$W\subset\MT$. Then on $W$,
\begin{equation}
 J_3^{0i}[\gamma]=0,\qquad
 J_3^{00}[\gamma]=q(\dot\gamma,\dot\gamma),\qquad
 q(a,b):=\tfrac14\bigl(\tr a\,\tr b-a_{ij}b_{ij}\bigr),
 \label{eq:J300}
\end{equation}
with spatial traces and contractions taken with $\delta_{ij}$, and
$\Hcal_1^{00}[\gamma]=0$.
\end{lemma}

\begin{proof}
On $W$ the metric is $q=\dd t^2-h_{ij}(t)\dd x^i\dd x^j$ with
$h=\delta-\kappa\gamma(t)$. The nonzero Christoffel symbols of XI-A's
convention are $\Gamma^0_{ij}=\tfrac12\dot h_{ij}$ and
$\Gamma^i_{0j}=K^i{}_j:=\tfrac12h^{ik}\dot h_{kj}$. Direct substitution
into $R_{\mu\nu}=\partial_\rho\Gamma^\rho_{\mu\nu}-\partial_\nu\Gamma^\rho_{\mu\rho}
+\Gamma^\rho_{\rho\lambda}\Gamma^\lambda_{\mu\nu}-\Gamma^\rho_{\nu\lambda}\Gamma^\lambda_{\mu\rho}$
gives $R_{0i}=0$, $R_{00}=-\dot K-K^i{}_jK^j{}_i$ with $K=K^i{}_i$, and
$h^{ij}R_{ij}=\dot K+K^2$, so that
$R=R_{00}-h^{ij}R_{ij}$ and
\[
 G_{00}=R_{00}-\tfrac12R=\tfrac12\bigl(K^2-K^i{}_jK^j{}_i\bigr),\qquad G_{0i}=0 .
\]
Since $q^{00}=1$ and $q^{0i}=0$, $G^{00}=G_{00}$ and $G^{0i}=0$ for every
$\kappa$; hence $J_3^{0i}=0$. Expanding $h^{ik}=\delta^{ik}+O(\kappa)$
and $\dot h=-\kappa\dot\gamma$ gives $K^i{}_j=-\tfrac12\kappa\dot\gamma_{ij}+O(\kappa^2)$,
$K=-\tfrac12\kappa\tr\dot\gamma+O(\kappa^2)$, and
$\sqrt{-q}=1+O(\kappa)$, so
$\sqrt{-q}\,G^{00}=\tfrac18\kappa^2[(\tr\dot\gamma)^2-\dot\gamma_{ij}\dot\gamma_{ij}]+O(\kappa^3)$.
Thus $\Hcal_1^{00}=0$ and $J_3^{00}=2\Hcal_2^{00}=q(\dot\gamma,\dot\gamma)$.
The signature does not affect $G_{\mu\nu}$; the Friedmann check
$G_{00}=3H^2$ for $h=a(t)^2\delta$ confirms the sign.
\end{proof}

\subsection{The obstruction}

\begin{theorem}[The frozen cubic kernel leaves the polynomial microcausal class]
\label{thm:F1}
Fix $m\geq0$, the frozen $g$, and the frozen $\sig$. Let
$t_g:=\min\{t:(t,\mathbf x)\in\supp g\}>0$. Choose $f\in C_c^\infty(\MTo)$,
$f\geq0$, $f\not\equiv0$, with $\supp f\subset(0,t_g)\times\R^3$ and
$\cos(mt)>0$ on $\supp f$. Let $\phi_m$ be XI-A's input,
$\phi_m=\sin(mt)/m$ for $m>0$ and $\phi_m=t$ for $m=0$. Then the
cubic kernel $u$ of $\Cthree(f,g)$ in \eqref{eq:ukernel} satisfies
\[
 \WF(u)\cap\bigl(\Vp^{\,3}\cup\Vm^{\,3}\bigr)\neq\varnothing .
\]
More precisely, with $\ell:=\pair{u}{\,\cdot\otimes v_2\otimes\phi_m}$
for the explicit $v_2$ below, there are points $y$ in an arbitrarily
thin collar around $\Sigma$ with $(y,\pm\dd t)\in\WF(\ell)$.
Consequently the ambient representative of $\Cthree(f,g)$ is not in
$\Fpol$, and XI-E's admission map $Q_H$ does not apply to it.
\end{theorem}

\begin{proof}
\emph{Step 1: the kernel for this $f$.} Since
$\Dfset\subset\{t<t_g\}$ and $\supp g\subset\{t\geq t_g\}$, we have
$\Dfset\cap\supp g=\varnothing$, so the $g$-term of
\eqref{eq:alphaexplicit} vanishes and $\alpha=-\sig C^*b$ with
$b=\EA(f\dd\phi_m)$. Here $\partial_\mu\phi_m=\cos(mt)\,\delta^0_\mu$,
so $b^0=\EA(f\cos(mt))$, $b^i=0$, and
\[
 \alpha^{00}=\tfrac12\sig\partial_tb^0,\qquad
 \alpha^{ij}=\tfrac12\sig\delta^{ij}\partial_tb^0,\qquad
 \alpha^{0i}=-\tfrac12\sig\partial_ib^0 .
\]
Hence $\tr\alpha=-\sig\partial_tb^0$ and
\[
 (\PP\alpha)^{00}=\sig\partial_tb^0,\qquad (\PP\alpha)^{ij}=0,\qquad
 (\PP\alpha)^{0i}=-\tfrac12\sig\partial_ib^0 .
\]
Therefore $\beta=\EA\PP\alpha$ has $\beta^{ij}=0$. Put
\[
 B(s):=\int_{\R^3}\beta^{00}(s,\mathbf x)\dd^3x .
\]
Because $\EA$ acts on sources of compact spatial support per slice
and $\int_{\R^3}\Delta(\cdot)\dd^3x=0$, spatial integration commutes
with $\EA$ and reduces it to its zero-frequency form:
$\int\EA F\dd^3x=\int_s^T(t'-s)\bar F(t')\dd t'$ with $\bar F=\int F\dd^3x$.
Thus
\[
 B(s)=\int_s^T(t'-s)\,\sig(t')\,\partial_t\bar b(t')\dd t',\qquad
 \bar b(t)=\int_t^T(t'-t)\bar F(t')\dd t',\qquad
 \bar F(t)=\int_{\R^3}f(t,\mathbf x)\cos(mt)\dd^3x\geq0 .
\]
Then $\partial_t\bar b(t)=-\int_t^T\bar F\leq0$, strictly negative for
$t<t_-:=\inf\{t:(t,\mathbf x)\in\supp f\}$, while $\sig(t')>0$ for
$t'>0$. Hence
\begin{equation}
 \Lambda_f:=B(0)=\int_0^Tt'\,\sig(t')\,\partial_t\bar b(t')\dd t'<0 .
 \label{eq:Lambda}
\end{equation}

\emph{Step 2: homogeneous configurations and the reduced functional.}
The spatial projection of $\Dfset$ lies in a ball $B_R$. Choose
$\vartheta\in C_c^\infty(\R^3)$ with $\vartheta=1$ on $B_{R+1}$, and
set, for $\lambda\in\R$, $\chi\in C_c^\infty((-\delta,\delta))$ with
$\chi(0)=1$ and $0<\delta<T$,
\[
 v_2(t,\mathbf x)=t\,\vartheta(\mathbf x)\,b_0,\qquad
 v_1^\lambda(t,\mathbf x)=\chi(t)e^{i\lambda t}\vartheta(\mathbf x)\,e,\qquad
 b_0=\diag(1,-1,0),\quad e=\diag(1,0,0),
\]
as purely spatial symmetric tensors ($\gamma_{0\mu}=0$). Complex
values are admissible by linearity. By finite propagation
(X-A, continuity proposition), $\Cthree$ depends on $\gamma$ only
through $\gamma|_{\Dfset}$, and on a neighbourhood of $\Dfset$ the
configuration $\gamma=v_2+\varepsilon v_1^\lambda$ is spatially
homogeneous with $\gamma_{0\mu}=0$. By Lemma~\ref{lem:ADM},
$J_3^{0i}[\gamma]=0$ and $J_3^{00}[\gamma]=q(\dot\gamma,\dot\gamma)$ there,
so \eqref{eq:C3beta} reduces to
\[
 \Cthree[\gamma,\phi_m]=\int_0^TB(s)\,q(\dot\gamma,\dot\gamma)(s)\dd s,
 \qquad
 \dot\gamma=b_0+\varepsilon(\chi e^{i\lambda s})'\,e .
\]
With $q(e,b_0)=\tfrac14(1\cdot0-1)=-\tfrac14$,
\[
 \pair{\ell}{v_1^\lambda}:=\frac{\dd}{\dd\varepsilon}\Big|_{\varepsilon=0}
 \Cthree[v_2+\varepsilon v_1^\lambda,\phi_m]
 =-\tfrac12\int_0^TB(s)\,(\chi e^{i\lambda s})'\dd s
 =\tfrac12B(0)\chi(0)+\tfrac12\int_0^TB'(s)\chi(s)e^{i\lambda s}\dd s ,
\]
using $\chi(T)=0$. By Riemann--Lebesgue the last integral tends to
zero as $|\lambda|\to\infty$, so
\begin{equation}
 \lim_{\lambda\to\pm\infty}\pair{\ell}{v_1^\lambda}=\tfrac12\Lambda_f\neq0 .
 \label{eq:limit}
\end{equation}

\emph{Step 3: the covector.} Since $v_1^\lambda$ has only the
$(1,1)$ component, $\pair{\ell}{v_1^\lambda}=\pair{\ell^{11}}{\chi\vartheta e^{i\lambda y^0}}$,
which is the Fourier transform of the compactly supported
distribution $w:=\chi\vartheta\,\ell^{11}$ at the covector
$-\lambda\,\dd t$. By \eqref{eq:limit} it does not decay along either
ray $\lambda\dd t$, $\lambda\to\pm\infty$. By
\cite[Definition~8.1.2, Proposition~8.1.3]{Hormander}, both $\pm\dd t$
lie in the cone $\Sigma(w)$, which is the projection of $\WF(w)$ to
the covector variable, and $\WF(w)\subset\WF(\ell^{11})$. Hence there
is $y\in\supp(\chi\vartheta)\subset\{|y^0|<\delta\}$ with
$(y,\pm\dd t)\in\WF(\ell^{11})\subset\WF(\ell)$. These covectors are
timelike, hence in $\Vp$ and $\Vm$ respectively. By
Lemma~\ref{lem:smear}, $u$ violates \eqref{eq:mc}. The last
assertion is Definition~\ref{def:domain}.
\end{proof}

\subsection{What is and is not excluded}

\begin{remark}[Not finite rank]
The obstruction is not the finite-rank mismatch XI-C recorded for the
local vertex and the bilinear insertion. Those have smooth-free
diagonal singularities compatible with \eqref{eq:mc}; $\Bcal_f$ and
$\Tcal$ were admitted. The cubic kernel fails \eqref{eq:mc} itself,
through a boundary covector that no diagonal argument sees.
\end{remark}

\begin{remark}[Mechanism and genericity]
Formula \eqref{eq:Lambda} is a particular case of
$\Lambda_f=-\int fY$, where $Y:=\ER\partial_t\bigl[t(\sig-g)\bigr]$
for $m=0$; on $\{t>\eps\}$ outside $\supp g$ one has $\Box Y=1$, so
$Y\not\equiv0$ and nonnegative bumps $f$ with $\Lambda_f\neq0$ exist
above the ramp as well. The special choice $\supp f\subset\{t<t_g\}$
only makes the sign of $\Lambda_f$ manifest for every $m$. The
boundary coefficient $\beta|_\Sigma$ is nonzero whenever
$\Dfset$ meets $\Sigma$ with nonvanishing data; the theorem exhibits
one admissible instance, which suffices to defeat a construction
that admits $\Cthree(f,g)$ for all admissible $f$.
\end{remark}

\begin{remark}[The on-shell class is not decided]
Theorem~\ref{thm:F1} concerns the frozen representative of
$\Cthree$: the slab functional viewed on $M$ by restriction, which is
the representative XI-E's admission uses. On the free shell, a
single-slot boundary trace $\int_\Sigma u\,\gamma(0,\cdot)$ equals a
bulk functional $-\int\gamma\Box v$ with a source flat at $\Sigma$,
hence has a smooth representative. The boundary term carried by $u$
at linear order in $v_1$ is a bilinear form in the Cauchy data of
\emph{both} metric slots, weighted by $\beta|_\Sigma$; whether it has
a representative satisfying \eqref{eq:mc} after both slots are
restricted to free data is not proved here, and we do not claim it.
Admission of some other representative of $[\Cthree|_{\Csol}]$ would
be a separate theorem.
\end{remark}

\begin{remark}[Two repairs that change the model]
Ramping the cubic source, $J_3\mapsto\sig J_3$, would make the kernel
flat at $\Sigma$; moving the metric Cauchy surface off $\Sigma$ would
move the onset. Either alters the frozen prescription of XI-A, in
which the Einstein--Hilbert density is unswitched and the second
coefficient has zero data on $\Sigma$. Neither is done. No cubic
source is contracted against a Hadamard line; that contraction is the
mixed loop and is not this paper.
\end{remark}

Gate 1 ends at \textbf{Proved obstructed}: the cubic kernel leaves
XI-E's interface. The evaluation of $\Cthree$ on smooth
configurations, already in XI-E, is not promoted to a quantum element.

%=====================================================================
\section{F2: the gauge-fixing companion}
\label{sec:F2}
%=====================================================================

\subsection{The de Donder variation from the fermion}

\begin{lemma}[Order-$\kappa$ variation of the de Donder term]
\label{lem:gf}
Let $s$ be a smooth symmetric tensor and shift $\gamma\mapsto\gamma+\kappa s$
with $(b,c,\bar c)$ held fixed. Then
\[
 \sfree\Psi[\gamma+\kappa s]=\sfree\Psi[\gamma]+2\kappa\int_{\MT}b_\mu D^\mu s\dd^4x,
\]
the auxiliary equation becomes $b=D(\gamma+\kappa s)$, and after
elimination
\begin{equation}
 S_{\mathrm{gf}}[\gamma+\kappa s]=S_{\mathrm{gf}}[\gamma]+2\kappa\int D\gamma\cdot Ds+\kappa^2\int Ds\cdot Ds,
 \qquad
 E_{\mathrm{gf}}[\gamma+\kappa s]-E_{\mathrm{gf}}[\gamma]=2\kappa D^*Ds .
 \label{eq:Egfvar}
\end{equation}
The ghost term $i\bar c_\mu\Box c^\mu$ is $\gamma$-independent: it
has no external metric leg at this order. Moreover
\begin{equation}
 \partial_\mu(2D^*Ds)^{\mu\nu}=-\Box D^\nu s .
 \label{eq:divgf}
\end{equation}
\end{lemma}

\begin{proof}
Read off from \eqref{eq:fermion}: only $2b\cdot D\gamma$ depends on
$\gamma$, linearly. Elimination of $b$ and expansion of the square give
\eqref{eq:Egfvar}, with $E_{\mathrm{gf}}=2D^*D\gamma$ as in XI-A.
For \eqref{eq:divgf}, with $v=Ds$,
$\partial_\mu(D^*v)^{\mu\nu}=-\tfrac12\Box v^\nu-\tfrac12\partial^\nu\partial\cdot v+\tfrac12\partial^\nu\partial\cdot v=-\tfrac12\Box v^\nu$.
This is XI-A's separation of the gauge-fixing breaking $-\Box D$ from
the invariant Noether identity, now at order $\kappa$ in $s$.
\end{proof}

Under the single-field law $\gamma'=\gamma+K\xi+\kappa\sxi+O(\kappa^2)$,
$\sxi:=\Lie_\xi\gamma+\tfrac12\Lie_\xi K\xi$ (with $\zeta=0$),
Lemma~\ref{lem:gf} and $DK\xi=\Box\xi$ give
\begin{equation}
 E_{\mathrm{gf}}[\gamma']=E_{\mathrm{gf}}[\gamma]+2D^*\Box\xi+2\kappa D^*D\sxi+O(\kappa^2).
 \label{eq:Egflaw}
\end{equation}
The order-$\kappa^0$ term is XI-A's and XI-B's linear breaking; the
order-$\kappa$ term is the companion the sheet asked for.

\begin{proposition}[Non-covariance of the gauge-fixed operator at order $\kappa$]
\label{prop:Etot}
Let $E_{\mathrm{tot}}[\gamma]=A\gamma+E_{\mathrm{gf}}[\gamma]+\kappa J_3[\gamma]=-\Box\PP\gamma+\kappa J_3[\gamma]$
be the gravitational part of the gauge-fixed Euler derivative through
order $\kappa$. For $\xi\in\ga$ and $\gamma'$ as above,
\begin{equation}
 E_{\mathrm{tot}}[\gamma']=E_{\mathrm{tot}}[\gamma]+2D^*\Box\xi
 +\kappa\bigl[\Ldens(A\gamma)+2D^*D\sxi\bigr]+O(\kappa^2).
 \label{eq:Etotlaw}
\end{equation}
\end{proposition}

\begin{proof}
$-\Box\PP(K\xi+\kappa\sxi)=(A+2D^*D)(K\xi+\kappa\sxi)=2D^*\Box\xi+\kappa(A\sxi+2D^*D\sxi)$
by \eqref{eq:algebra}. Next, $J_3$ is quadratic, so
$J_3[\gamma+K\xi]=J_3[\gamma]+\delta_0J_3[\gamma]+J_3[K\xi]$, with
$\delta_0J_3=\Ldens(A\gamma)-A\Lie_\xi\gamma$ by \eqref{eq:XIEvar}.
For $J_3[K\xi]$: the pullback $F_\kappa^*\eta=\eta+\kappa K\xi+\kappa^2(K\zeta+\tfrac12\Lie_\xi K\xi)+O(\kappa^3)$
is flat for every $\kappa$, so $\sqrt{-q}\,G(F_\kappa^*\eta)\equiv0$;
its $\kappa^2$ coefficient is $\Hcal_1[K\zeta+\tfrac12\Lie_\xi K\xi]+\Hcal_2[K\xi]=0$,
and $AK\zeta=0$ gives
\begin{equation}
 J_3[K\xi]=-A\bigl(\tfrac12\Lie_\xi K\xi\bigr).
 \label{eq:flat}
\end{equation}
Hence $\kappa J_3[\gamma']=\kappa J_3[\gamma]+\kappa(\Ldens(A\gamma)-A\sxi)+O(\kappa^2)$,
and the $A\sxi$ terms cancel.
\end{proof}

The invariant part $A\gamma+\kappa J_3$ transforms by the density
pullback; the whole non-covariance at order $\kappa$ sits in
$2D^*D\sxi$. That is the content of ``gauge fixing is not plateau
invariant'' (XI-A) one order up.

\subsection{The companion response}

\begin{definition}[Gauge-fixing response and de Donder parameter]
\label{def:gf}
For $s$ smooth, compactly supported in $U$, set
\begin{equation}
 \dgf[s]:=-\Ggr\bigl(2D^*Ds\bigr),\qquad
 \zgf[s]:=-\ER Ds .
 \label{eq:dgf}
\end{equation}
\end{definition}

\begin{proposition}[Properties of the companion]
\label{prop:gfprops}
\begin{enumerate}[label=\textup{(\alph*)}]
\item $\dgf[s]=-2\RR\ER Ds=K\zgf[s]$: the companion is pure gauge.
\item $\zgf[s]$ has zero Cauchy data and $\supp\zgf[s]\subset J^+(\supp s)\cap\MT\subset\{t>\eps\}$;
it is not in $\ga$.
\item $D\bigl(s+K\zgf[s]\bigr)=0$: $\zgf$ is the second-order parameter
restoring the de Donder divergence of $s$.
\item The divergence of the source is \eqref{eq:divgf}; the response
satisfies $\Box\zgf=-Ds$.
\end{enumerate}
\end{proposition}

\begin{proof}
(a) $-\Ggr(2D^*Ds)=2\PP\ER D^*Ds=2\PP D^*\ER Ds=-2\RR\ER Ds=K(-\ER Ds)$,
using \eqref{eq:algebra} and $\RR=\tfrac12K$. (b) Zero-data retarded
solution of a source supported in $U\subset\{t>\eps\}$; its support is
not compact in $U$. (c) $D(s+K\zgf)=Ds+\Box\zgf=Ds-Ds=0$.
(d) is immediate.
\end{proof}

\subsection{Finite transformation of the cubic response}

\begin{theorem}[The cubic response obeys the complete second-order law]
\label{thm:u3law}
For every smooth $\gamma$ and $\xi\in\ga$,
\begin{equation}
 u_3[\gamma+K\xi]-u_3[\gamma]
 =\sxi+K\zgf[\sxi]+\PP\ER\Ldens(A\gamma),
 \qquad
 \sxi=\Lie_\xi\gamma+\tfrac12\Lie_\xi K\xi .
 \label{eq:u3law}
\end{equation}
If $A\gamma=0$ on $U$, the last term vanishes and
\begin{equation}
 u_3[\gamma+K\xi]=u_3[\gamma]+\Lie_\xi\gamma+K\zgf[\sxi]+\tfrac12\Lie_\xi K\xi,
 \qquad
 D\,u_3[\gamma+K\xi]=D\,u_3[\gamma].
 \label{eq:u3lawvac}
\end{equation}
\end{theorem}

\begin{proof}
By the proof of Proposition~\ref{prop:Etot},
$J_3[\gamma+K\xi]-J_3[\gamma]=\Ldens(A\gamma)-A\sxi$. Apply
$-\Ggr=\PP\ER$ and Lemma~\ref{lem:GA} ($\sxi$ is compactly supported in
$U$): $-\Ggr(-A\sxi)=\sxi-2\RR\ER D\sxi=\sxi+K\zgf[\sxi]$. If $A\gamma=0$
on $U\supset\supp\xi$, then $\Ldens(A\gamma)=0$. The divergence
statement is Proposition~\ref{prop:gfprops}(c).
\end{proof}

Comparing with X-A's law $k'=k+\Lie_\xi h+K\zeta+\tfrac12\Lie_\xi K\xi$
at $(h,k)=(\gamma,u_3[\gamma])$: the response supplies the covariant
term $\Lie_\xi\gamma$, the quadratic flow term through
\eqref{eq:flat}, and a definite second-order parameter
$\zeta=\zgf[\sxi]$. Gauge fixing does not break the second-order law;
it selects $\zeta$. The selected $\zeta$ is not compactly supported in
$U$, which is why a remainder survives in Section~\ref{sec:F3}.

\subsection{The switching formula for a de Donder parameter}

\begin{lemma}[Pure gauge with zero data: coordinate and switching terms]
\label{lem:switch}
Let $\zeta$ be smooth on $\MT$ with zero Cauchy data and
$\supp\zeta\subset\{t\geq\eps\}$, and let $\phi_0$ be free. Then
\begin{align}
 \Xone[K\zeta]&=\zeta,
 \label{eq:preflight}\\
 \Aone[K\zeta;\phi_0]
 &=\int_{\MT}f\,(g-1)\,X_\zeta\phi_0\dd^4x
 -\int_{\MT}f\,\ERm\Bigl([\Pfree,g]X_\zeta\phi_0
 +(\partial_\mu g)\,a_1^{\mu\nu}[K\zeta]\,\partial_\nu\phi_0\Bigr)\dd^4x,
 \label{eq:switch}
\end{align}
where $X_\zeta=\zeta^\mu\partial_\mu$ and $[\Pfree,g]u=(\Box g)u+2(\partial^\mu g)\partial_\mu u$.
Every term carries a factor $g-1$ or $\partial g$ evaluated on
$\supp\zeta\cap\Dfset$. In particular
\begin{equation}
 \Aone[K\zeta;\phi_0]=0\qquad\text{whenever }\Dfset\cap\supp\zeta\subset P_g .
 \label{eq:switchvanish}
\end{equation}
\end{lemma}

\begin{proof}
\eqref{eq:preflight}: $a_1[K\zeta]$ is supported in $\supp\zeta$, where
$\sig=1$ and $\sig'=0$, so $\Box\Xone[K\zeta]=-\partial_\alpha a_1^{\alpha\cdot}[K\zeta]=C[K\zeta]=\Box\zeta$,
and both sides have zero data; this is X-A's preflight argument,
which uses only the support and the data, not compactness.
\eqref{eq:switch}: by X-A's lemma on the pure-gauge variation,
$\Vone[K\zeta]\phi_0=g(D_\zeta\Pfree\phi_0-\Pfree X_\zeta\phi_0)+(\partial g)a_1[K\zeta]\partial\phi_0
=-g\Pfree X_\zeta\phi_0+(\partial g)a_1[K\zeta]\partial\phi_0$. Since
$gX_\zeta\phi_0$ has zero data,
$\ERm(g\Pfree X_\zeta\phi_0)=gX_\zeta\phi_0-\ERm[\Pfree,g]X_\zeta\phi_0$.
Subtract the coordinate term $\int f\zeta\cdot\partial\phi_0$.
The support statement follows by transposing $\ERm$ onto $f$:
$\int f\ERm(\cdot)=\int(\EAm f)(\cdot)$ with $\EAm f$ supported in
$\Dfset$. If $g=1$ on a neighbourhood of $\Dfset\cap\supp\zeta$, then
$\partial g=0$ there as well, and all terms vanish.
\end{proof}

%=====================================================================
\section{F3: the plateau sum}
\label{sec:F3}
%=====================================================================

\subsection{The cubic-completed second coefficient}

\begin{definition}[Cubic-completed coefficient]
\label{def:A23}
For a free $\phi_0$ and a smooth $\gamma$,
\begin{equation}
 \Atwothree[\gamma;\phi_0]
 :=\Atwo^{\mathrm{sc}}\bigl[\gamma,u_3[\gamma];\phi_0\bigr]-\Tcal(f,g)[\phi_0].
 \label{eq:A23}
\end{equation}
\end{definition}

The second metric coefficient of the gauge-fixed equation with the
scalar source is $u_3[\gamma]+r_g[\phi_0]$; by \eqref{eq:affine} the
$r_g$ term contributes $\Aone[r_g[\phi_0];\phi_0]=-\Tcal-\Tcal_{\mathrm{sc}}$,
with $\Tcal_{\mathrm{sc}}:=\int f\ERm\Vone[r_g]\phi_0$ the
scalar-response companion of XI-C's coordinate tree. Both are
independent of $\gamma$ and inert under every operation below; we
follow the sheet and keep only $-\Tcal$. Nothing in this section
changes if $-\Tcal_{\mathrm{sc}}$ is added.

\begin{theorem}[Variation of the cubic-completed coefficient]
\label{thm:F3}
For every smooth $\gamma$, every free $\phi_0$, and every $\xi\in\ga$,
\begin{align}
 \Aone[\gamma+K\xi;\phi_0]-\Aone[\gamma;\phi_0]&=0,
 \label{eq:F3first}\\
 \Atwothree[\gamma+K\xi;\phi_0]-\Atwothree[\gamma;\phi_0]
 &=\Aone\bigl[K\zgf[\sxi];\phi_0\bigr]
 +\Aone\bigl[\PP\ER\Ldens(A\gamma);\phi_0\bigr].
 \label{eq:F3}
\end{align}
\end{theorem}

\begin{proof}
\eqref{eq:F3first} is \eqref{eq:XAv} at first order. For
\eqref{eq:F3}, $\Tcal$ cancels, and we split the difference in two
steps. First, with $\gamma+K\xi$ fixed in the first slot,
\eqref{eq:affine} and Theorem~\ref{thm:u3law} give
\[
 \Atwo^{\mathrm{sc}}[\gamma+K\xi,u_3[\gamma+K\xi]]-\Atwo^{\mathrm{sc}}[\gamma+K\xi,u_3[\gamma]]
 =\Aone[\sxi]+\Aone[K\zgf[\sxi]]+\Aone[\PP\ER\Ldens(A\gamma)].
\]
Second, apply \eqref{eq:XAv} with $(h,k)=(\gamma,u_3[\gamma])$,
$F$ the flow of $\kappa\xi$ ($\zeta=0$), for which
$k'=u_3[\gamma]+\sxi$:
$\Atwo^{\mathrm{sc}}[\gamma+K\xi,u_3[\gamma]+\sxi]=\Atwo^{\mathrm{sc}}[\gamma,u_3[\gamma]]$.
By \eqref{eq:affine},
\[
 \Atwo^{\mathrm{sc}}[\gamma+K\xi,u_3[\gamma]]-\Atwo^{\mathrm{sc}}[\gamma,u_3[\gamma]]
 =-\Aone[\sxi].
\]
Adding the two steps gives \eqref{eq:F3}. ($u_3[\gamma]$ is smooth on
the closed slab and extends smoothly across its boundary; X-A's
identities use only values on $\MT$.)
\end{proof}

\begin{corollary}[Plateau sum]
\label{cor:plateau}
If $A\gamma=0$ on $U$, then
\begin{equation}
 \Atwothree[\gamma+K\xi;\phi_0]-\Atwothree[\gamma;\phi_0]
 =\Aone\bigl[K\zgf[\sxi];\phi_0\bigr],
 \label{eq:plateausum}
\end{equation}
a pure switching term of the form \eqref{eq:switch}, and
\begin{equation}
 \Atwothree[\gamma+K\xi;\phi_0]=\Atwothree[\gamma;\phi_0]
 \qquad\text{whenever}\qquad
 \Dfset\cap J^+(\supp\xi)\subset P_g .
 \label{eq:plateauzero}
\end{equation}
\end{corollary}

\begin{proof}
Theorem~\ref{thm:F3}, Proposition~\ref{prop:gfprops}(b), and
Lemma~\ref{lem:switch}: $\supp\zgf[\sxi]\subset J^+(\supp\xi)\cap\MT\subset\{t\geq\eps\}$,
with zero data.
\end{proof}

\subsection{The ledger on the witness}

Take \eqref{eq:witness}. Then $A\gamma=0$ everywhere, so
Corollary~\ref{cor:plateau} applies, and $g=1$ on the whole observation
dependence cylinder, so $\Dfset\cap J^+(\supp\xi)\subset P_g$ and the
sum is zero. The sheet asks that the contributions be printed before
they are added. In the cylinder, with $r=\Lie_\xi\gamma$,
$s_2=\tfrac12\Lie_\xi K\xi$, and $p:=aa''+2a'^2$,
\[
 r_{00}=a+2ta',\quad r_{ij}=-a\delta_{ij},\qquad
 (s_2)_{00}=p,\quad (s_2)_{0i}=(s_2)_{ij}=0,
\]
\[
 D^0r=ta'',\qquad D^0s_2=\tfrac12p',\qquad D^ir=D^is_2=0 .
\]

\paragraph{L1, held-fixed cross term, linear in $\xi$.}
XI-E recomputed $\Xone^0[r]=ta-2\int_0^ta$, $\Vone[r]\phi=-4ta'-2t^2a''$,
$-\ER\Vone[r]\phi=2t^2a-4\int_0^tsa$, whence the density
$4\int_0^t(t-s)a(s)\dd s$ and
\[
 \text{L1}=-\Aone[r;\phi]=-I .
\]

\paragraph{L2, held-fixed cross term, quadratic in $\xi$.}
$a_1^{00}[s_2]=-\tfrac12p$, $a_1^{ij}[s_2]=-\tfrac12p\delta^{ij}$,
$\Xone^0[s_2]=\ER(\tfrac12p')=\tfrac12P(t)$ with $P(t)=\int_0^tp$,
$\Vone[s_2]\phi=\partial_0(-pt)+a_1^{ij}\partial_i\partial_j\phi=-2p-tp'$, and
$-\ER\Vone[s_2]\phi=\int_0^t(t-s)(2p+sp')\dd s=tP(t)$. The density is
$tP-\tfrac12P\cdot2t=0$:
\[
 \text{L2}=-\Aone[s_2;\phi]=0 .
\]

\paragraph{L3, covariant part of the cubic response, linear.}
\[
 \text{L3}=+\Aone[\Lie_\xi\gamma;\phi]=+I .
\]

\paragraph{L4, covariant part of the cubic response, quadratic.}
\[
 \text{L4}=+\Aone[\tfrac12\Lie_\xi K\xi;\phi]=0 .
\]

\paragraph{L5, gauge-fixing response.}
$\zgf[\sxi]=z(t)\partial_t$ with $z=-\ER(ta''+\tfrac12p')=-(ta-2\int_0^ta+\tfrac12P)$,
$z(0)=z'(0)=0$. For any such $\zeta=z\partial_t$ in the $g=1$ cylinder,
$(K\zeta)_{00}=2z'$, $a_1^{00}[K\zeta]=-z'$, $a_1^{ij}[K\zeta]=-z'\delta^{ij}$,
$\Vone[K\zeta]\phi=-4z'-2tz''$, $-\ER\Vone[K\zeta]\phi=2tz$,
$\Xone[K\zeta]=\zeta$, and the density is $2tz-z\,\partial_0\phi=2tz-2tz=0$.
This is Lemma~\ref{lem:switch} verified by hand:
\[
 \text{L5}=\Aone[K\zgf[\sxi];\phi]=0 .
\]
(For $t$ beyond $\supp a$, $z$ is the constant
$2\int a-\tfrac12\int a'^2$: the de Donder parameter ends as a rigid
time translation. This is a remark, not an input.)

\paragraph{L6, Einstein-shell term.}
\[
 \text{L6}=\Aone[\PP\ER\Ldens(A\gamma);\phi]=0\qquad(A\gamma=0).
\]

\paragraph{L7, tree.}
$\Tcal$ has no metric argument: $\text{L7}=0$.

\begin{equation}
 \boxed{\;
 \text{L1}+\text{L2}+\text{L3}+\text{L4}+\text{L5}+\text{L6}+\text{L7}
 =-I+0+I+0+0+0+0=0 .\;}
 \label{eq:ledger}
\end{equation}
This is Corollary~\ref{cor:plateau} evaluated, and the positive
witness pairing \eqref{eq:I} verifies the sign: the held-fixed
$-I$ is removed by the covariant part of the response generated by
the cubic vertex, not by the gauge-fixing response, which pairs to
zero.

\subsection{The sheet's three symbols, and the double count}

The production sheet asked for $\delta_{\mathrm{split}}+\delta_0\Cthree+\dgf$,
with XI-E's values. In the ledger above these are:
\begin{align*}
 \delta_{\mathrm{split}}&=\text{L1}+\text{L2}+(\text{by-hand }+I)=-I+0+I=0
 &&\text{(XI-E, cancellation theorem)},\\
 \delta_0\Cthree&=\text{L3}+\text{L5}\big|_{\text{linear}}=I+0=I
 &&\text{(XI-E, cubic variation)},\\
 \dgf&=\text{L5}=0
 &&\text{(Proposition~\ref{prop:gfprops}, this paper)}.
\end{align*}
Their literal sum is $0+I+0=I$. That number is not an obstruction.
The ``by-hand $+I$'' inside $\delta_{\mathrm{split}}$ is the shift
$\gamma\mapsto\gamma+\kappa\Lie_\xi\gamma$ restored by XI-E in a
parametrization with an external second coefficient $k$ and an
independent field $\gamma$; L3 is the shift $\Lie_\xi\gamma$ generated
by the cubic response once $k=u_3[\gamma]$. They are one term in two
notations. XI-E's theorem is correct in its own parametrization, and
XI-E's $\delta_0\Cthree=I$ is correct; what is incorrect is the
sheet's instruction to add them. Removing the duplicate gives
\eqref{eq:ledger}. Nothing is dropped: $\Cthree$ is retained, and so
is its $I$. The sheet's expectation $\dgf=-I$ is replaced by the
computed value $\dgf=0$.

\subsection{The Einstein-shell term, named}

On the gauge-fixed free shell $-\Box\PP\gamma=0$ one has
$A\gamma=-2D^*D\gamma=-2D^*b$, which vanishes exactly when
$D^*b=0$; constant $b$ (the witness) and $b=0$ (the de Donder
Einstein shell) are examples, and every linearized Einstein solution
in any gauge satisfies $A\gamma=0$. For gauge-fixed-shell
configurations with $D^*b\neq0$ on $U$, Theorem~\ref{thm:F3} retains
the term $\Aone[\PP\ER\Ldens(-2D^*b);\phi_0]$. It is an explicit
classical functional; its value on the plateau is not computed here
and is not asserted to vanish. This is XI-A's distinction between the
gauge-fixed wave equation and the Einstein equation, met again at
second order: the cubic source transforms as a density only modulo
$A\gamma$.

%=====================================================================
\section{Support of the remainder}
\label{sec:support}
%=====================================================================

\begin{proposition}[Support of the plateau remainder]
\label{prop:support}
Let $A\gamma=0$ on $U$ and $\xi\in\ga$. The remainder
$R_\xi:=\Aone[K\zgf[\sxi];\phi_0]$ in \eqref{eq:plateausum} is given by
\eqref{eq:switch} with $\zeta=\zgf[\sxi]$. As a functional of $\zeta$
its kernel is supported in
\begin{equation}
 \bigl(\supp\dd g\ \cup\ \supp((1-g)f)\bigr)\ \cap\ J^+(\supp\xi)\ \cap\ \Dfset .
 \label{eq:remsupport}
\end{equation}
There is no ramp term: $\zgf[\sxi]$ vanishes on $\{t\leq\eps\}$ and
$\Xone[K\zgf]=\zgf$ exactly. With the observation-plateau hypothesis
$\supp f\subset P_g$ the second set is empty and the kernel is
supported in $\supp\dd g\cap J^+(\supp\xi)\cap\Dfset$. Without it,
$\supp((1-g)f)$ remains, as in XI-E's Route~2.
\end{proposition}

\begin{proof}
Lemma~\ref{lem:switch} and Proposition~\ref{prop:gfprops}(b). The
first term of \eqref{eq:switch} is supported in $\supp f\cap\{g\neq1\}\cap\supp\zeta$;
the second, after transposition onto $\EAm f$, in
$\supp\partial g\cap\supp\zeta\cap\Dfset$.
\end{proof}

Compare XI-E's support formula for arbitrary compact ghosts, which
had the additional layer $\{0\leq t\leq\eps\}$: an unrestricted ghost
can enter the ramp, while the de Donder parameter selected by the
cubic response cannot, because it is retarded from $U$. The
remainder is a genuine switching defect: for an observation whose
dependence region meets $\supp\dd g$ inside $J^+(\supp\xi)$, the
second-order parameter forced by gauge fixing reaches the switching
region, where the switched scalar action is not covariant. It is
zero on the witness and under \eqref{eq:plateauzero}.

%=====================================================================
\section{F4: what the sum is not}
\label{sec:F4}
%=====================================================================

\begin{itemize}
\item Equation \eqref{eq:plateauzero} is a classical coefficient
identity on off-shell plateau parameters $\xi\in\ga$, for a free
scalar held fixed. It is not nilpotence of an interacting
differential, not a quantum master equation, and not a quantum Ward
identity. No $\widehat s_{\mathrm{int}}$, antibracket, or antifield
term is constructed; XI-B's antifields remain slots.
\item The co-transformation $\Lie_\xi\gamma$, now generated by the
response rather than inserted by hand, is still not free: on the
witness its spatial wave operator contains $-a''\delta_{ij}$. It is
not an automorphism of $\Afree$, and the ghost rule
$\sfree\gamma=\tfrac12Kc$ is not that shift.
\item Because $\Cthree$ is not admitted (Theorem~\ref{thm:F1}), there
is no element of $\Ealg$ whose symbol is $\Atwothree$, and no quantum
version of \eqref{eq:ledger} exists in the frozen algebra. The ledger
is classical.
\item The two affine numbers are untouched: the bare insertion still
fails by $S_\eps(t)$, the complete coordinate word still leaves
$\eps/2$. Neither enters the cubic ledger; neither is erased by it.
\item No mixed loop is evaluated; no state is selected; no
$\eps\to0$ limit is taken; $\Jcal_g(\phi_m)=\varnothing$ stands.
\end{itemize}

%=====================================================================
\section{Decision, exclusions, and handoff}
\label{sec:decision}
%=====================================================================

\begin{center}
\small
\begin{tabularx}{\linewidth}{@{}p{.10\linewidth}p{.27\linewidth}X@{}}
\toprule
Gate & Ending & Exact scope\\
\midrule
F1 &
\textbf{Proved obstructed} &
The frozen representative of $\Cthree(f,g)$ has
$\pm\dd t\in\WF$ at $\Sigma$ in a metric slot
(Theorem~\ref{thm:F1}); it leaves $\Fpol$, and XI-E's
admission map does not apply. Mechanism: zero Cauchy data for
the second coefficient together with an unswitched, unramped cubic
source. Not finite rank; not a loop. The on-shell class is open.\\[0.4em]
F2 &
\textbf{Constructed} &
De Donder variation $2D^*D\sxi$ from XI-B's fermion, divergence
$-\Box D\sxi$, response $K\zgf[\sxi]$, $\zgf=-\ER D\sxi$, coefficient
$-1$ (Lemma~\ref{lem:gf}, Proposition~\ref{prop:gfprops}). Ghost
term has no metric leg at this order.\\[0.4em]
F3 &
\textbf{Constructed} &
$u_3$ obeys the X-A second-order law with $\zeta=\zgf$
(Theorem~\ref{thm:u3law}); the cubic-completed coefficient shifts by
$\Aone[K\zgf]$ plus the named Einstein-shell term
(Theorem~\ref{thm:F3}); zero when $A\gamma=0$ on $U$ and
$\Dfset\cap J^+(\supp\xi)\subset P_g$; ledger $-I+0+I+0+0+0+0=0$ on
the witness; remainder supported in \eqref{eq:remsupport}, no ramp
term.\\[0.4em]
F4 &
Recorded &
Not a Ward identity; not an automorphism; no quantum version in
$\Ealg$; affine numbers untouched.\\
\bottomrule
\end{tabularx}
\end{center}

\begin{center}
\small
\begin{tabularx}{\linewidth}{@{}p{.08\linewidth}X X X@{}}
\toprule
Gate & Constructed only if & Obstructed if & Result\\
\midrule
F1 & $\Cthree\in\Ealg$ with the XI-E embedding &
kernel leaves the copied wavefront class &
\textbf{Obstructed}: timelike conormal at $\Sigma$\\
F2 & de Donder variation computed in the coefficient $-1$ &
--- & \textbf{Constructed}\\
F3 & plateau sum proved, support stated &
interior pairing nonzero on the witness &
\textbf{Constructed}: sum $=0$; the sheet's $I$ was a double count\\
\bottomrule
\end{tabularx}
\end{center}

The worst ending among the two gates governs: \textbf{Proved
obstructed}, at the admission gate. The plateau sum is constructed as
a classical identity and could not be quantized in $\Ealg$ even if
its sum were nonzero.

\subsection*{Exclusions that persist}

\begin{itemize}
\item No state, Hadamard selection beyond XI-E's product data, or
expectation value.
\item No mixed-loop value; the cubic source is not contracted against
a Hadamard line.
\item No interacting differential, antibracket, or master identity.
\item No sharp-width limit; no identification with VII-B's or IX-A's
sharp insertions, although the covector found in Theorem~\ref{thm:F1}
is the same timelike conormal type.
\item No repair of $\Jcal_g(\phi_m)=\varnothing$; no switching of the
Einstein--Hilbert density; no ramp on the cubic source.
\item X-E's and X-F's normalizations and identities are not premises.
\end{itemize}

\subsection*{What a successor receives}

\begin{enumerate}
\item The kernel representation \eqref{eq:C3beta}--\eqref{eq:ukernel}
and the obstruction Theorem~\ref{thm:F1}, with the open on-shell
question stated.
\item The de Donder companion $K\zgf$ and the finite transformation
law \eqref{eq:u3law}, including the Einstein-shell term.
\item The variation identity \eqref{eq:F3}, the plateau corollary,
the ledger \eqref{eq:ledger}, and the support formula
\eqref{eq:remsupport}.
\item The correction that XI-E's by-hand co-transformation and the
covariant part of the cubic response are one mechanism.
\item Two named routes that would change the model: a ramped cubic
source, or metric data off $\Sigma$. Neither is taken here.
\end{enumerate}

\subsection*{Conclusion}

\[
 \boxed{
 \begin{gathered}
 \Cthree\notin\Fpol:\ \text{the frozen cubic kernel carries }\pm\dd t\text{ at }\Sigma;\\[2pt]
 u_3[\gamma+K\xi]-u_3[\gamma]=\Lie_\xi\gamma+\tfrac12\Lie_\xi K\xi+K\zgf+\PP\ER\Ldens(A\gamma),
 \quad \zgf=-\ER D\sxi;\\[2pt]
 \Atwothree[\gamma+K\xi]-\Atwothree[\gamma]=\Aone[K\zgf;\phi_0]\ \ (A\gamma=0\text{ on }U),
 \quad -I+I+0=0\text{ on the witness.}
 \end{gathered}}
\]
A reader can now see that $\Cthree$ is not an element of the frozen
algebra, and that the second $I$ of the cubic variation is cancelled
by the held-fixed term it was always paired with, while the
gauge-fixed companion contributes zero. A zero sum does not construct
the interacting class XI-E withheld.

%=====================================================================
\section*{Declarations}
\addcontentsline{toc}{section}{Declarations}

\paragraph{Proof scope.}
The kernel representation, the wavefront witness, the fermion
computation, the finite transformation law, the variation identity,
the ledger, and the support statement are proved on smooth
configurations in the displayed conventions. The on-shell
representative question for $\Cthree$ is stated as open.

\paragraph{Dependencies.}
X-A supplies the Cauchy facts, kernel lemma, preflight argument, and
Theorem~(v). XI-A supplies the signed action and the gauge-fixed
versus Einstein distinction. XI-B supplies the fermion, normalization,
and free shell. XI-C and XI-D supply the tree sign and the affine
lemma. XI-E supplies the algebra, its domain, the cubic variation,
and the witness. Hörmander supplies the wavefront tools.

\paragraph{Corrections.}
The admission mechanism, the value of the gauge-fixing companion, the
double count in the three-term sum, the origin of the quadratic flow
term, the non-plateau support of the de Donder parameter, and the
retained Einstein-shell term are corrected relative to the production
sheet.

\paragraph{Verification.}
No successful \texttt{pdflatex} execution, proof-assistant check,
executed symbolic computation, independent referee review, or journal
acceptance is asserted. All nonzero and zero witnesses are analytic.

%=====================================================================
\begin{thebibliography}{9}
\addcontentsline{toc}{section}{References}

\bibitem{XA}
N.~Cheung,
\emph{Landmark X-A: Classical covariance of one fixed-regulator
switched relational scalar through order $\kappa^2$}.
Supplied manuscript \texttt{X-A.tex}.
Used for the Cauchy lemma, transposition, kernel lemma, preflight
argument, pure-gauge variation lemma, and Theorem~(v).

\bibitem{XIA}
N.~Cheung,
\emph{Landmark XI-A: A switched Einstein--scalar action for the
ramp relational scalar}.
Supplied manuscript \texttt{XI-A.tex}.
Used for the signed action, $E_{\mathrm{gf}}=2D^*D\gamma$, the
breaking $-\Box D$, and the empty fixed-input jet.

\bibitem{XIB}
N.~Cheung,
\emph{Landmark XI-B: The free de Donder multiplet for the ramp
Einstein--scalar sheet}.
Supplied manuscript \texttt{XI-B.tex}.
Used for the gauge fermion, the normalization $-\PP\ER$, and the
free shell.

\bibitem{XIC}
N.~Cheung,
\emph{Landmark XI-C: One fixed-regulator graviton tree for the ramp
relational scalar}.
Supplied manuscript \texttt{XI-C.tex}.
Used for the tree sign $-\Tcal$ and the held-fixed defect.

\bibitem{XID}
N.~Cheung,
\emph{Landmark XI-D: Admission of the fixed-width graviton tree and
one ghost-number-zero identity}.
Supplied manuscript \texttt{XI-D.tex}.
Used for the written-out second coefficient and the affine lemma.

\bibitem{XIE}
N.~Cheung,
\emph{Landmark XI-E: On-shell admission of the fixed-width tree,
a localized first-order identity, and the held-fixed defect}.
Supplied manuscript \texttt{XI-E.tex}.
Used for the Hadamard algebra and its domain, the cubic response,
its variation, the split cancellation, and the witness.

\bibitem{Hormander}
L.~H\"ormander,
\emph{The Analysis of Linear Partial Differential Operators I},
Grundlehren der mathematischen Wissenschaften 256, second edition,
Springer, 1990.
Used for Definition~8.1.2, Proposition~8.1.3, and
Theorem~8.2.12.

\bibitem{BGP}
C.~B\"ar, N.~Ginoux, and F.~Pf\"affle,
\emph{Wave Equations on Lorentzian Manifolds and Quantization},
ESI Lectures in Mathematics and Physics, European Mathematical
Society, 2007. arXiv:0806.1036.
Used for smooth Cauchy theory and finite propagation.

\end{thebibliography}

\end{document}