§6 · Agent 6 · E₆/F₄: restriction map · 2026-10-17T02:24:47Z

Theorem 6.6 · \(E_6/F_4\): two points of the shifted torus that are not \(W_X\)-conjugate are \(W(E_6)\)-conjugate, so \(r\) is not onto and (SG) fails under (A1)–(A5)Sakellaridis's standing assumptions for his Theorem 8.0.2 (the pages' Theorem E): (A1) a characteristic-0 field and a split group with simply connected derived group; (A2) an integral model of X with a smooth open Borel orbit and invariant measures; (A3a) rank-one models over O, (A3b) the Cartan decomposition, (A3c) Iwahori orbits (his Axioms 2.2.1, 2.4.1, 2.4.2); (A4) conditions on the spherical roots and colours; (A5) X homogeneous and affine with one open Borel orbit.

proved audit: minor defect ★ key step

Minor defect (second audit). Main claim verified independently, in a Bourbaki R^8 model of E6 with theta=-w_L built from scratch: lambda2* lies in the W-orbit of lambda1* (orbit of size 25920, unique dominant element rho-omega4); both reflection words end at rho-omega4; the explicit w is an element of W(E6) with <lambda1*,mu>=<lambda2*,w mu>, and exactly two elements of W have this property; the W_X-orbits, sigma(y1), and the values of M_(3,0), M_(0,3), M_(1,1) recomputed. Wording defect: the gloss 'the Hecke module H_K phi_0 misses the orbit label 3omega1^vee' conflates the orbit sum M_(3,0) with the image of the orbit indicator (Sakellaridis's P_lambda, not M_lambda), and no argument is given for the stronger reading 1_{O_{3omega1^vee}} not in H_K phi_0. That reading is true under (A)“Under (A)”: assuming all of Sakellaridis's assumptions (A1)–(A5) for X at the given p-adic place, so that his Theorem 8.0.2 applies.: in the proof of Sakellaridis Thm 8.0.2, 1_{x_lambda K} maps to P_lambda whose other weights lie in lambda+T, T the cone of colour valuations; T is sigma-stable, strictly convex and meets the antidominant cone only in 0, so T lies in {a+b>0} union {0}; hence P_(3,0)=c M_(3,0)+c1 M_(1,1)+c0 with c!=0, and l(g)=g(y1)-g(sigma y1) gives l(P_(3,0))=c l(M_(3,0))!=0. No downstream node uses the strong reading as a proof step.

The points \(y_1=(q^{-5},q)\) and \(y_2=(q^{-5},q^4)\) of the dual torus \(A_X^*\) are not related by the little Weyl group \(S_3\), but after the shift by \(q^{\rho_L}\) they become conjugate under \(W(E_6)\), and the orbit sum \(M_{(3,0)}\) takes different values at them. So \(M_{(3,0)}\notin\operatorname{im}r\) and, by Theorem E, spherical generation fails for \(E_6/F_4\) over \(p\)-adic fields under Sakellaridis's hypotheses: the function-level half of the only candidate divergence.

Theorem 6.6.

Let \(X=E_6/F_4\), with \(r\), \(u,v\), \(M_\kappa\), \(m_\mu\) and \(\sigma\) as in Computation 6.4, and let \(y_1,y_2\in A_X^*\) be the positive real points with \((u,v)\)-coordinates $$y_1=(q^{-5},\,q),\qquad y_2=(q^{-5},\,q^{4}).$$ Then:

  1. \(q^{\rho_L}y_1\) and \(q^{\rho_L}y_2\) are \(W\)-conjugate in \(A^*\);
  2. \(y_1\) and \(y_2\) are not \(W_X\)-conjugate;
  3. \(M_{(3,0)}(y_1)\ne M_{(3,0)}(y_2)\).

Hence \(M_{(3,0)}\notin\operatorname{im}r\), \(r\) is not onto, and by Theorem E(2) (SG) fails for \(E_6/F_4\) under (A1)–(A5)Sakellaridis's standing assumptions for his Theorem 8.0.2 (the pages' Theorem E): (A1) a characteristic-0 field and a split group with simply connected derived group; (A2) an integral model of X with a smooth open Borel orbit and invariant measures; (A3a) rank-one models over O, (A3b) the Cartan decomposition, (A3c) Iwahori orbits (his Axioms 2.2.1, 2.4.1, 2.4.2); (A4) conditions on the spherical roots and colours; (A5) X homogeneous and affine with one open Borel orbit., for every \(q\). The conclusion does not depend on the sign of the shift or on left/right conventions (Setup 6.1). More precisely, $$\operatorname{im}r\subseteq\mathcal K:=\{g\in\C[\Lambda_S]^{S_3}:g(y_1)=g(\sigma y_1)\}\subsetneq\C[\Lambda_S]^{S_3},$$ and the missing generator is \(M_{(3,0)}\): the Hecke module \(\cH_K\varphi_0\) misses the orbit label \(3\omega_1^\vee\) (and, symmetrically, \(3\omega_6^\vee\)).

A point \(x\in A^*\) with \(x^{\alpha_j^\vee}=q^{n_j}\), \(n_j\in\Z\), is written \(x=q^\lambda\), where \(\lambda\) is the weight with \(\langle\lambda,\alpha_j^\vee\rangle=n_j\); then \(x^\mu=q^{\langle\lambda,\mu\rangle}\), and \(w\cdot q^\lambda=q^{w\lambda}\) for \(w\in W\).

Proof of 1.

  1. Write \((u_i,v_i)\) for the coordinates of \(y_i\). By Computation 6.4, \(x_i:=q^{\rho_L}y_i\) has \(x_i^{\alpha_1^\vee}=q^{-3}u_i\), \(x_i^{\alpha_6^\vee}=q^{-3}v_i\) and \(x_i^{\alpha_j^\vee}=q\) for \(j=2,\dots,5\). So \(x_1^{\alpha_1^\vee}=x_2^{\alpha_1^\vee}=q^{-8}\), \(x_1^{\alpha_6^\vee}=q^{-2}\), \(x_2^{\alpha_6^\vee}=q\), and \(x_i=q^{\lambda_i^*}\) with, in fundamental-weight coordinates,
$$\lambda_1^*=(-8,1,1,1,1,-2)=\rho-9\omega_1-3\omega_6,\qquad\lambda_2^*=(-8,1,1,1,1,1)=\rho-9\omega_1 .$$

It suffices to show that \(\lambda_1^*\) and \(\lambda_2^*\) are \(W\)-conjugate.

  1. A simple reflection \(s_j\) changes fundamental-weight coordinates by \(c\mapsto c-c_j\cdot(\text{row }j\text{ of the Cartan matrix})\). Applying it repeatedly at a negative coordinate, the words (applied from left to right)
$$\lambda_1^*:\ s_1s_3s_4s_2s_5s_4s_3s_1s_6s_5s_4s_2s_3s_1s_4s_3s_5s_6,\qquad\lambda_2^*:\ s_1s_3s_4s_2s_5s_4s_3s_1s_6s_5s_4s_2s_3$$

take both weights to the dominant weight \((1,1,1,0,1,1)=\rho-\omega_4\). Hence \(\lambda_1^*\) and \(\lambda_2^*\) are \(W\)-conjugate.

  1. Norm check: \((\lambda_1^*,\lambda_1^*)-(\lambda_2^*,\lambda_2^*)=-6(\rho,\omega_6)+54(\omega_1,\omega_6)+9(\omega_6,\omega_6)=-48+36+12=0\).
  2. An explicit \(w\in W\) with \(x_1^\mu=x_2^{w\mu}\) for all \(\mu\), found by exhaustive search over the 51840 elements of \(W\), is
$$w(\alpha_1^\vee)=\alpha_1^\vee,\quad w(\alpha_2^\vee)=\alpha_4^\vee,\quad w(\alpha_3^\vee)=-(\alpha_1^\vee+\alpha_2^\vee+\alpha_3^\vee+2\alpha_4^\vee+2\alpha_5^\vee+\alpha_6^\vee),$$ $$w(\alpha_4^\vee)=\alpha_5^\vee,\quad w(\alpha_5^\vee)=\alpha_6^\vee,\quad w(\alpha_6^\vee)=\alpha_1^\vee+\alpha_2^\vee+2\alpha_3^\vee+2\alpha_4^\vee+\alpha_5^\vee .$$
  1. Independently of \(w\): \(m_\mu(x_1)=m_\mu(x_2)\) as exact Laurent polynomials in \(q^{1/2}\) for all 23 dominant \(\mu\) of norm at most 20.

Proof of 2. In logarithmic coordinates \((\log_qu,\log_qv)\) the generators of \(W_X\) act by \(s_1(\alpha,\beta)=(-\alpha,\alpha+\beta)\) and \(s_6(\alpha,\beta)=(\alpha+\beta,-\beta)\), so $$W_Xy_1=\{(-5,1),(-4,-1),(-1,5),(1,4),(4,-5),(5,-4)\},\qquad W_Xy_2=\{(-5,4),(-4,5),(-1,-4),(1,-5),(4,1),(5,-1)\}.$$ These are disjoint, and since \(q>1\) a positive real point is determined by its logarithms. Moreover \(\sigma(u,v)=(v,u)\), so \(\sigma y_1=(q,q^{-5})\in W_Xy_2\): the gluing identifies \(y_1\) with its \(\sigma\)-image, matching the \(\sigma\)-odd functional of Computation 6.5.

Proof of 3. \(W_X(3,0)=\{(3,0),(-3,3),(0,-3)\}\). Writing \((a,b)=c_1e_1+c_6e_6\) with \(c_1=\tfrac{2a+b}3\) and \(c_6=\tfrac{a+2b}3\), one has \(y^{(a,b)}=u^{c_1}v^{c_6}\), hence $$M_{(3,0)}(y_1)=q^{6}+q^{3}+q^{-9},\qquad M_{(3,0)}(y_2)=q^{9}+q^{-3}+q^{-6},$$ which differ for every \(q>1\) (for \(q=2\): \(72.002\) against \(512.14\)). As a check, \(M_{(0,3)}(y_1)=M_{(3,0)}(y_2)\), while \(M_{(1,1)}\) and \(M_{(2,2)}\) take equal values at \(y_1\) and \(y_2\), as they must.

Conclusion. By 1 and 2 the gluing criterion of Lemma 6.2 applies, and by 3 the separating invariant can be taken to be \(M_{(3,0)}\); so \(M_{(3,0)}\notin\operatorname{im}r\), and by the symmetry \(\sigma\) of Computation 6.4 also \(M_{(0,3)}\notin\operatorname{im}r\). Every \(g\in\operatorname{im}r\) satisfies \(g(y_1)=g(y_2)=g(\sigma y_1)\), the last equality because \(g\) is \(W_X\)-invariant; this is the inclusion \(\operatorname{im}r\subseteq\mathcal K\), which is proper because \(M_{(3,0)}\notin\mathcal K\). Only the \(W\)-conjugacy of the integral weights \(\lambda_1^*,\lambda_2^*\) is used, so the argument holds for every \(q\). In Sakellaridis's language (as in his Example 8.0.1), points of \(\delta(X)^{1/2}A_X^*\) that are not \(W_X\)-conjugate become \(W\)-conjugate; here this happens through the shift \(q^{\rho_L}\), so the glued points move with \(q\), whereas in his example \(\delta(X)\) is trivial.

Verified by computation: e6_words.py, e6_points.py, e6_verify.py.

Builds on

  • Lemma 6.2 · Two criteria for the surjectivity of \(r\): monoid generators suffice, and a glued pair of points forbids it
  • Computation 6.4 · \(E_6/F_4\): root data, the shift \(q^{\rho_L}\), the little Weyl group \(S_3\), and the three generators of the target
  • Computation 6.5 · \(E_6/F_4\): in every computed window the image of \(r\) has codimension one, cut out by a \(\sigma\)-odd functional

Built on by

Original record, as the agent wrote it at 02:24 UTC

E6/F4: two non-W_X-conjugate points of the shifted torus are W-conjugate, so r is not onto

Claim. Let \(y_1,y_2\in A_X^*\) be the positive real points with \((u,v)\)-coordinates $$y_1=(q^{-5},\,q),\qquad y_2=(q^{-5},\,q^{4}).$$ Then (i) \(q^{\rho_L}y_1\) and \(q^{\rho_L}y_2\) are \(W\)-conjugate in \(A^*\); (ii) \(y_1,y_2\) are not \(W_X\)-conjugate; (iii) \(M_{(3,0)}(y_1)\ne M_{(3,0)}(y_2)\). Hence \(M_{(3,0)}\notin\operatorname{im}r\), \(r\) is not onto, and by Theorem E(2) (SG) fails for \(E_6/F_4\) under (A1)–(A5), for every \(q\). The conclusion is independent of the sign of the shift (A6-1) and of left/right conventions.

Proof of (i). By A6-4, \(x_i:=q^{\rho_L}y_i\) has \(x_i^{\alpha_j^\vee}=q^{\langle\lambda_i^*,\alpha_j^\vee\rangle}\) with integral weights, in fundamental-weight coordinates, $$\lambda_1^*=(-8,1,1,1,1,-2)=\rho-9\omega_1-3\omega_6,\qquad\lambda_2^*=(-8,1,1,1,1,1)=\rho-9\omega_1 .$$ (\(x_1^{\alpha_1^\vee}=q^{-3}q^{-5}=q^{-8}\), \(x_1^{\alpha_6^\vee}=q^{-3}q=q^{-2}\), \(x_2^{\alpha_6^\vee}=q^{-3}q^4=q\), black coordinates \(q\).) It suffices that \(\lambda_1^*,\lambda_2^*\) are \(W\)-conjugate. Applying simple reflections \(s_j(c)=c-c_j\,(\text{row }j\text{ of the Cartan matrix})\) to negative coordinates (e6_words.py): $$\lambda_1^*\xrightarrow{s_1s_3s_4s_2s_5s_4s_3s_1s_6s_5s_4s_2s_3s_1s_4s_3s_5s_6}(1,1,1,0,1,1),\qquad\lambda_2^*\xrightarrow{s_1s_3s_4s_2s_5s_4s_3s_1s_6s_5s_4s_2s_3}(1,1,1,0,1,1)$$ (words applied left to right), the common dominant weight \(\rho-\omega_4\). Norm check: \((\lambda_1^*,\lambda_1^*)-(\lambda_2^*,\lambda_2^*)=-6(\rho,\omega_6)+54(\omega_1,\omega_6)+9(\omega_6,\omega_6)=-48+36+12=0\). An explicit \(w\) with \(x_1^{\mu}=x_2^{w\mu}\) for all \(\mu\): \(w(\alpha_1^\vee)=\alpha_1^\vee\), \(w(\alpha_2^\vee)=\alpha_4^\vee\), \(w(\alpha_3^\vee)=-(\alpha_1^\vee+\alpha_2^\vee+\alpha_3^\vee+2\alpha_4^\vee+2\alpha_5^\vee+\alpha_6^\vee)\), \(w(\alpha_4^\vee)=\alpha_5^\vee\), \(w(\alpha_5^\vee)=\alpha_6^\vee\), \(w(\alpha_6^\vee)=\alpha_1^\vee+\alpha_2^\vee+2\alpha_3^\vee+2\alpha_4^\vee+\alpha_5^\vee\) (found by the exhaustive search of e6_points.py over all 51840 elements of \(W\), verified in e6_verify.py). Independent check: \(m_\mu(x_1)=m_\mu(x_2)\) as exact Laurent polynomials in \(q^{1/2}\) for all 23 dominant \(\mu\) of norm \(\le20\).

Proof of (ii). In \((\log_q u,\log_q v)\): \(W_Xy_1=\{(-5,1),(-4,-1),(-1,5),(1,4),(4,-5),(5,-4)\}\), \(W_Xy_2=\{(-5,4),(-4,5),(-1,-4),(1,-5),(4,1),(5,-1)\}\), disjoint. (Also \(y_2\in W_X\,\sigma(y_1)\), \(\sigma(y_1)=(q,q^{-5})\): the gluing identifies \(y_1\) with its \(\sigma\)-image, matching the \(\sigma\)-odd functional of A6-5.)

Proof of (iii). \(W_X(3,0)=\{(3,0),(-3,3),(0,-3)\}\), and \((a,b)=c_1e_1+c_6e_6\) with \(c_1=\tfrac{2a+b}3\), \(c_6=\tfrac{a+2b}3\), so \(y^{(a,b)}=u^{c_1}v^{c_6}\): $$M_{(3,0)}(y_1)=q^{6}+q^{3}+q^{-9},\qquad M_{(3,0)}(y_2)=q^{9}+q^{-3}+q^{-6},$$ different for \(q>1\) (e.g. \(q=2\): \(72.002\) vs \(512.14\)). Also \(M_{(0,3)}(y_1)=M_{(3,0)}(y_2)\), while \(M_{(1,1)},M_{(2,2)}\) agree at \(y_1,y_2\), as they must.

Consequence. \(\operatorname{im}r\subseteq K:=\{g\in\mathbb C[\Lambda_S]^{S_3}:g(y_1)=g(\sigma y_1)\}\subsetneq\mathbb C[\Lambda_S]^{S_3}\). The missing generator is \(M_{(3,0)}\), i.e. the Hecke module \(\mathcal H_K\varphi_0\) misses the orbit label \(3\omega_1^\vee\) (and, symmetrically, \(3\omega_6^\vee\)); in Sakellaridis's language (as in Example 8.0.1) \(W_X\)-nonconjugate points of \(\delta(X)^{1/2}A_X^*\) are \(W\)-conjugate — here through the shift \(q^{\rho_L}\) (the glued points move with \(q\)), unlike his example where \(\delta(X)\) is trivial.

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