{"kind":"theorem_check","report":{"conclusion":{"first_index":0,"interlacing":"weak","interlacing_from":1,"root_region":{"upper":{"closed":true,"value":"-1"}},"simple_roots":false,"statement":"every P_n, n >= 0, is nonzero and real-rooted with every root in (-inf, -1] (so its coefficients have one sign); for n >= 1, P_(n-1) interlaces P_n (weakly, in the sense of Liu and Wang), and deg P_n - deg P_(n-1) is 0 or 1 for n >= 2"},"hypotheses":[{"evidence":"degrees 0 and 0; real-rooted and P_0 << P_1 checked exactly","name":"seed_rows","statement":"P_0 and P_1 are nonzero and real-rooted, of degrees e and e or e + 1, and P_0 << P_1 (weak interlacing)","status":{"kind":"verified"}},{"evidence":"l_n = (0) l_(n-1) + ([x^1] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 0 (then deg P_n - deg P_(n-1) = 1): positive seeds and nonnegative step coefficients: s_n >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of s_n at n = 2 + u have one sign); t_n >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of t_n at n = 2 + u have one sign); s_n + t_n > 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of s_n + t_n at n = 2 + u have one sign)","name":"degree_law_from_step_0","statement":"deg P_n - deg P_(n-1) is 0 or 1 and P_n, P_(n-2) have positive leading coefficients (after the sign normalization) for every n >= 2: degree steps (deg P_(n-1) - deg P_(n-2) -> deg P_n - deg P_(n-1)) 0 -> 1, 1 -> 0; l_n = (0) l_(n-1) + ([x^1] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 0 (then deg P_n - deg P_(n-1) = 1)","status":{"kind":"verified"}},{"evidence":"l_n = ([x^0] A_n) l_(n-1) + ([x^1] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 1 (then deg P_n - deg P_(n-1) = 0): positive seeds and nonnegative step coefficients: s_n >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of s_n at n = 2 + u have one sign); t_n >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of t_n at n = 2 + u have one sign); s_n + t_n > 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of s_n + t_n at n = 2 + u have one sign)","name":"degree_law_from_step_1","statement":"deg P_n - deg P_(n-1) is 0 or 1 and P_n, P_(n-2) have positive leading coefficients (after the sign normalization) for every n >= 2: degree steps (deg P_(n-1) - deg P_(n-2) -> deg P_n - deg P_(n-1)) 0 -> 1, 1 -> 0; l_n = ([x^0] A_n) l_(n-1) + ([x^1] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 1 (then deg P_n - deg P_(n-1) = 0)","status":{"kind":"verified"}},{"evidence":"[t^1] B_n(-1 - t) <= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of [t^1] B_n(-1 - t) at n = 2 + u have one sign)","name":"lag_coefficient_nonpositive","statement":"B_n(x) <= 0 for every x in (-inf, -1] and every n >= 2","status":{"kind":"verified"}},{"evidence":"[t^0] A_n(-1 + t) >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of [t^0] A_n(-1 + t) at n = 2 + u have one sign); A_n(0) > 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of A_n(0) at n = 2 + u have one sign); [t^1] B_n(-1 + t) >= 0 for every integer n in [2, +inf) (exact; Taylor shift: the coefficients of [t^1] B_n(-1 + t) at n = 2 + u have one sign)","name":"window_upper_end","statement":"A_n(x) > 0 and B_n(x) >= 0 for every x > -1 and every n >= 2 (no row gets a root > -1)","status":{"kind":"verified"}},{"evidence":"checked exactly","name":"seed_roots_in_window","statement":"P_0 and P_1 have every root in (-inf, -1]","status":{"kind":"verified"}}],"lean_declarations":["RealRooted.MaWang.strictInterl_of_interlaces_evalCoeff_nonpos"],"lean_replay":"not_attempted","normal_form":"P_n = A_n(x) P_(n-1) + B_n(x) P_(n-2) for n >= 2, with A_n(x) = (1), B_n(x) = (1) + (1) x","recurrence":{"first_index":0,"initial_polynomials":[["1"],["2"]],"recurrence":{"terms":[{"coeff":{"coeffs":[["1"]]},"deriv_order":0,"offset":1,"sign":"none"},{"coeff":{"coeffs":[["1","1"]]},"deriv_order":0,"offset":2,"sign":"none"}]},"schema":"polytool.recurrence.v1"},"reference":"L. L. Liu and Y. Wang, Adv. Appl. Math. 38 (2007) 542-560, Theorem 2.1 and Corollary 2.4 (A unified approach to polynomial sequences with only real zeros; the lag row as the interlacer, b_n = 0), weak interlacing of consecutive rows, with nonnegativity of the coefficients replaced, where a root region is certified, by an exact root-location induction","schema":"polytool.recurrence-real-rootedness-theorem.v1","status":"proved","theorem":"liu_wang_three_term"}}