The local Gan–Gross–Prasad conjecture for general spin groups: a Lean blueprint

9 Further statements not yet used by the main theorem

These statements are formalized but not (yet) on the path of the main theorem: the analytic estimates of Thesis Ch. 8 and 10 (the convergence of \(J\) is stated separately above), the Levi decomposition and transport of \(m_{\mathrm{geom}}\) (Thesis §7.2, §9.3), and checks of the normalization of \(\hat j\) on \(\mathfrak {sl}_2\).

9.1 Estimates

Thesis Ch. 8, §10.1.

Proposition 188 Good minimal parabolic subgroups

(Thesis Prop. 8.1.1(i), existence.) There are full isotropic flags of \(W\) and \(V\) whose stabilizer \(\bar P\) satisfies \(H\cap \bar U_{\min }=\{ 1\} \), with \(H(F)\bar P(F)\) open in \(G(F)\) and of Haar-null complement.

Proof ▶

Not yet formalized (adapted from [ 5 ] Prop. 6.4.1). “Good” is replaced by its two consequences used in the estimates.

Lemma 189 Thesis Lemma 8.2.1(i)

For \(r=0\) there is \(\epsilon {\gt}0\) with \(\int _{H_0(F)/A_{G,H}(F)}\Xi ^{G_0}(h_0)e^{\epsilon \sigma (h_0)}\, dh_0{\lt}\infty \). This differs from Thesis Lemma 8.2.1(i), which integrates over \(H_0(F)/A_{H_0}(F)\).

Proof ▶

Not yet formalized (adapted from [ 5 ] Lemma 6.5.1(i)).

Lemma 190 Thesis Lemma 8.2.1(ii)

There is \(d{\gt}0\) with \(\int _{H(F)/A_{G,H}(F)}\Xi ^G(h)\sigma (h)^{-d}\, dh{\lt}\infty \).

Proof ▶

Not yet formalized (adapted from [ 5 ] Lemma 6.5.1(ii)).

Lemma 191 Thesis Lemma 8.2.1(iii)

For every \(\delta {\gt}0\) there is \(\epsilon {\gt}0\) with \(\int _{H(F)/A_{G,H}(F)}\Xi ^G(h)e^{\epsilon \sigma (h)}(1+|\lambda (h)|)^{-\delta }\, dh{\lt}\infty \).

Proof ▶

Not yet formalized (adapted from [ 5 ] Lemma 6.5.1(iii)).

There are \(d{\gt}0\) and a continuous seminorm \(\nu \) on \(\mathcal C(A_G(F)\backslash G(F),\chi ^{-1})\) with \(|K(f,x)|\le \nu (f)\, \Xi ^{H\backslash G}(x)^2\sigma _{H\backslash G}(x)^{d}\).

Proof ▶

Not yet formalized (adapted from [ 5 ] Thm. 8.1.1(i)).

9.2 Levi subgroups

Proposition 193 The Levi decomposition

For a GGP datum \(\tilde d\) realizing the Levi pair \((\tilde W,\tilde V)\) of a pair of isotropic flags, there is a surjective homomorphism with central kernel from the Levi quotient \(P/U\) onto \(\prod \mathrm{GL}(Z'_{i,W})\times \prod \mathrm{GL}(Z'_{j,V})\times \tilde G(F)\) (Thesis §5.1.2, (9.3.1)–(9.3.3)).

Proof ▶

Not yet formalized: it needs the Clifford-algebra description of the Levi subgroup.

Lemma 194 Transport of \(m_{\mathrm{geom}}\)

For an isomorphism of GGP triples \(e:G\to G'\) and a quasi-character \(\theta '\) of \(G'(F)\), \(m_{\mathrm{geom}}(\theta '\circ e)=m_{\mathrm{geom}}(\theta ')\) (Thesis §7.2, Prop. 12.1.1).

Proof ▶

Not yet formalized: needs the transport of \(\mathcal O_x\) and \(\hat j\).

9.3 Normalization checks on \(\mathfrak {sl}_2\)

Sanity checks of the definition of \(\hat j\) for \(\mathrm{GL}_2(F)\) acting on \(\mathfrak {sl}_2(F)\) with the trace form.

Lemma 195 The regular orbit measure exists

The \(\mathrm{GL}_2(F)\)-invariant measure on the regular nilpotent orbit, normalized by the self-dual measure on \(\mathfrak g/\mathfrak g_E\) ( [ 5 ] §1.6, Thesis §2.4), exists.

Proof ▶

Not yet formalized: needs the \(p\)-adic inverse function theorem and invariant measures on homogeneous spaces.

Lemma 196 \(\hat j(\mathcal O_{\mathrm{reg}},\cdot )\) on the split torus

For \(X=x\, \mathrm{diag}(1,-1)\), \(x\neq 0\): \(\hat j(\mathcal O_{\mathrm{reg}},X)=2/|2x|\).

Proof ▶

Not yet formalized (hand computation, every residue characteristic).

Lemma 197 \(\hat j(\mathcal O_{\mathrm{reg}},\cdot )\) on elliptic tori

For \(\varepsilon \) a nonsquare and \(x\neq 0\), \(\hat j(\mathcal O_{\mathrm{reg}},x\begin{pmatrix} 0 & 1 \\ \varepsilon & 0 \end{pmatrix})=0\).

Proof ▶

Not yet formalized: \(\mu _{\mathcal O_{\mathrm{reg}}}\) is induced from the Borel, so its Fourier transform is induced from the split torus.

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