import json import math from decimal import Decimal, getcontext # Set high precision for exact threshold comparisons at N ~ 10^12 getcontext().prec = 80 def seifert_matrix(p_list): m = len(p_list) V = [[0] * (m - 1) for _ in range(m - 1)] for j in range(m - 1): V[j][j] = (p_list[j] + p_list[j + 1]) // 2 if j + 1 < m - 1: V[j][j + 1] = -(p_list[j + 1] + 1) // 2 if j - 1 >= 0: V[j][j - 1] = -(p_list[j] - 1) // 2 return V def det_int(M): n = len(M) A = [row[:] for row in M] sign = 1 prev = 1 for i in range(n): pivot = i while pivot < n and A[pivot][i] == 0: pivot += 1 if pivot == n: return 0 if pivot != i: A[i], A[pivot] = A[pivot], A[i] sign = -sign for j in range(i + 1, n): for k in range(i + 1, n): A[j][k] = (A[i][i] * A[j][k] - A[j][i] * A[i][k]) // prev A[j][i] = 0 prev = A[i][i] return sign * A[n - 1][n - 1] def signature_3strand_from_trace_det(tr, det): """ For a 2x2 Hermitian matrix with real trace `tr` and real determinant `det`: - If det < 0: one positive, one negative eigenvalue -> signature = 0. - If det > 0: two eigenvalues of the same sign as `tr` -> signature = +2 if tr > 0 else -2. - If det == 0: one zero eigenvalue, one eigenvalue equal to `tr` -> +1 if tr > 0, -1 if tr < 0, 0 if tr == 0. """ if det < 0: return 0 elif det > 0: if tr > 0: return 2 elif tr < 0: return -2 else: return 0 else: if tr > 0: return 1 elif tr < 0: return -1 else: return 0 def solve(): # --------------------------------------------------------- # Key 1: Determinant of K_1 = P(3, -5, -7, 9, -11, 13, -17) # --------------------------------------------------------- p1 = [3, -5, -7, 9, -11, 13, -17] V1 = seifert_matrix(p1) n1 = len(V1) S1 = [[V1[i][j] + V1[j][i] for j in range(n1)] for i in range(n1)] knot_det = abs(det_int(S1)) # --------------------------------------------------------- # General 2x2 Hermitian form H(omega) for 3-strand P(p, q, r): # V = [[(p+q)/2, -(q+1)/2], [-(q-1)/2, (q+r)/2]] # Let x = 1 - cos(theta) = 2 * sin^2(theta/2) in (0, 2] for omega = e^{i theta} != 1. # Notice: # H(omega) = (1 - omega) V + (1 - bar(omega)) V^T # = x (V + V^T) - i sin(theta) (V - V^T) # Since S = V + V^T = [[p+q, -q], [-q, q+r]] and A = V - V^T = [[0, -1], [1, 0]], # we have: # Tr(H(omega)) = x * Tr(S) = x * (p + 2q + r). # det(H(omega)) = x^2 * det(S) - sin^2(theta) * 1 # Since sin^2(theta) = x * (2 - x), # det(H(omega)) = x * (x * det(S) - (2 - x)) = x * ((det(S) + 1) * x - 2). # Since x > 0 for omega != 1: # - sign(Tr(H(omega))) = sign(p + 2q + r) # - sign(det(H(omega))) = sign((D + 1) * x - 2), where D = det(S) = pq + qr + rp. # --------------------------------------------------------- # For K(n) = P(2n+1, -(4n+1), -(6n+3)): # p = 2n+1, q = -4n-1, r = -6n-3 # Tr(S) = p + 2q + r = (2n+1) - 2(4n+1) - (6n+3) = -12n - 4 < 0 for all n >= 1. # D(n) = pq + qr + rp # = (2n+1)(-4n-1) + (-4n-1)(-6n-3) + (-6n-3)(2n+1) # = (2n+1)(-4n - 1 - 6n - 3) + (4n+1)(6n+3) # = (2n+1)(-10n - 4) + (24n^2 + 18n + 3) # = -20n^2 - 18n - 4 + 24n^2 + 18n + 3 = 4n^2 - 1. # Wait: For n >= 1, D(n) = 4n^2 - 1 >= 3 > 0! # Let's check when D(n) can change sign or if we wait: # At omega = -1 (x = 2): (D(n)+1)*2 - 2 = 2*D(n) > 0 for all n >= 1. # At omega = e^{2pi i / 3} (x = 3/2): (D(n)+1)*(3/2) - 2 = (3/2)*4n^2 - 2 = 6n^2 - 2 > 0 for all n >= 1. # That's constant for all n! Let's double check if K(n) has constant signature for Keys 2 and 3: # Yes, for K(n) = P(2n+1, -(4n+1), -(6n+3)), D(n) = 4n^2 - 1 > 0 for all n >= 1. # Let's still compute Keys 2 and 3 directly from the formula. sig_sum_k2 = 0 for n in range(1, 2500 + 1): p = 2 * n + 1 q = -(4 * n + 1) r = -(6 * n + 3) D = p * q + q * r + r * p tr_S = p + 2 * q + r # omega = -1 => x = 2 det_H = 2 * ((D + 1) * 2 - 2) tr_H = 2 * tr_S sig_sum_k2 += signature_3strand_from_trace_det(tr_H, det_H) # Key 3: sum_{n=1}^{5,000,000} sigma_{omega_3}(K(n)) # For omega_3 = e^{2pi i / 3}, x = 1 - cos(2pi/3) = 3/2. # Since D(n) = 4n^2 - 1 >= 3 for all n >= 1, (D(n)+1)*(3/2) - 2 = 6n^2 - 2 > 0, # and tr_S = -12n - 4 < 0, every term has signature -2. N3 = 5000000 tl_1_3 = -2 * N3 # --------------------------------------------------------- # Keys 4 and 5: K_* = P(2000003, -4000005, -6000007) # Let's compute D_* and tr_S_* for K_*: # --------------------------------------------------------- p_star = 2000003 q_star = -4000005 r_star = -6000007 D_star = p_star * q_star + q_star * r_star + r_star * p_star tr_S_star = p_star + 2 * q_star + r_star # Let's check D_star: # p_star = 2*10^6 + 3 # q_star = -4*10^6 - 5 # r_star = -6*10^6 - 7 # D_star = (2e6+3)(-4e6-5) + (-4e6-5)(-6e6-7) + (-6e6-7)(2e6+3) # = 4*10^12 + 12*10^6 + 1 # Since D_star + 1 > 0 and tr_S_star < 0: # For omega = e^{2pi i r / q} (1 <= r < q): # x(r/q) = 1 - cos(2pi r / q) = 2 sin^2(pi r / q). # det(H(omega)) > 0 <=> (D_star + 1) * 2 sin^2(pi r / q) > 2 # <=> sin(pi r / q) > 1 / sqrt(D_star + 1). # Let alpha = (1 / pi) * arcsin(1 / sqrt(D_star + 1)) in (0, 1/2). # Then for 1 <= r < q: # - If r/q in (0, alpha) or r/q in (1 - alpha, 1): det(H) < 0 => signature = 0. # - If r/q == alpha or r/q == 1 - alpha: det(H) == 0 => signature = -1 (cannot happen for rational r/q since D_star + 1 > 2). # - If r/q in (alpha, 1 - alpha): det(H) > 0 and Tr(H) < 0 => signature = -2. # # Therefore, for any modulus q >= 2: # Let K_cut(q) = floor(alpha * q). # For 1 <= r < q: # sigma_{e^{2pi i r / q}}(K_*) = 0 if 1 <= r <= K_cut(q) or q - K_cut(q) <= r <= q - 1, # and -2 if K_cut(q) < r < q - K_cut(q). # # Consequently, the primitive cyclotomic sum is: # S_prim(K_*, q) = -2 * #{ 1 <= r < q : gcd(r, q) = 1 and K_cut(q) < r < q - K_cut(q) } # = -2 * ( phi(q) - 2 * #{ 1 <= r <= K_cut(q) : gcd(r, q) = 1 } ) # (for q > 2; since K_cut(q) < q/2). # Compute alpha to 80 decimal digits using Newton/Taylor series for arcsin: # Since u = 1 / sqrt(D_star + 1) ~ 5 * 10^-7 is very small, # arcsin(u) = u + u^3/6 + 3*u^5/40 + 5*u^7/112 + 35*u^9/1152 + ... D_plus_1 = Decimal(D_star + 1) u = Decimal(1) / D_plus_1.sqrt() u2 = u * u arcsin_u = u * ( Decimal(1) + u2 / Decimal(6) + (Decimal(3) * u2 * u2) / Decimal(40) + (Decimal(5) * (u2**3)) / Decimal(112) + (Decimal(35) * (u2**4)) / Decimal(1152) + (Decimal(63) * (u2**5)) / Decimal(2816) ) pi_dec = Decimal( "3.14159265358979323846264338327950288419716939937510582097494459230781640628620899" ) alpha = arcsin_u / pi_dec # Sieve primes up to 10^6 + 100 for factoring q in [10^12, 10^12 + 2000] Q_start = 10**12 Q_end = 10**12 + 2000 limit = int(math.isqrt(Q_end)) + 10 is_prime = bytearray([1]) * (limit + 1) is_prime[0] = is_prime[1] = 0 for i in range(2, int(math.isqrt(limit)) + 1): if is_prime[i]: is_prime[i * i : limit + 1 : i] = bytearray(len(range(i * i, limit + 1, i))) primes = [i for i, v in enumerate(is_prime) if v] # Segmented factorization for [Q_start, Q_end] span = Q_end - Q_start + 1 rem = [Q_start + i for i in range(span)] prime_factors = [[] for _ in range(span)] for p in primes: start_idx = (-Q_start) % p for idx in range(start_idx, span, p): prime_factors[idx].append(p) while rem[idx] % p == 0: rem[idx] //= p for idx in range(span): if rem[idx] > 1: prime_factors[idx].append(rem[idx]) def s_prim_from_factors(q, p_facs): k_cut = int(alpha * Decimal(q)) # Generate squarefree divisors of q with their Mobius values and compute phi(q) divs = [(1, 1)] phi_q = q for p in p_facs: phi_q = (phi_q // p) * (p - 1) divs += [(d * p, -mu) for d, mu in divs] # Count #{1 <= r <= k_cut : gcd(r, q) == 1} = sum_{d | q} mu(d) * floor(k_cut / d) coprime_le_k = 0 for d, mu in divs: coprime_le_k += mu * (k_cut // d) return -2 * (phi_q - 2 * coprime_le_k) # Key 4: Q = 10^12 + 39 Q4 = 10**12 + 39 s_prim_Q4 = s_prim_from_factors(Q4, prime_factors[Q4 - Q_start]) # Key 5: sum_{q = 10^12}^{10^12 + 2000} S_prim(K_*, q) total_s_prim = 0 for idx in range(span): q = Q_start + idx total_s_prim += s_prim_from_factors(q, prime_factors[idx]) res = { "problem_id": "MATH5", "knot_determinant": knot_det, "knot_signature": sig_sum_k2, "tristram_levine_1_3": tl_1_3, "rasmussen_s_knot": s_prim_Q4, "rasmussen_s_sum": total_s_prim, } print(json.dumps(res)) if __name__ == "__main__": solve()