216 lines
7.5 KiB
Python
216 lines
7.5 KiB
Python
class superelliptic_form:
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def __init__(self, C, g):
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F = C.base_ring
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Rxy.<x, y> = PolynomialRing(F, 2)
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Fxy = FractionField(Rxy)
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g = Fxy(reduction_form(C, g))
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self.form = g
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self.curve = C
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def __eq__(self, other):
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if self.reduce().form == other.reduce().form:
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return True
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return False
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def __add__(self, other):
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C = self.curve
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g1 = self.form
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g2 = other.form
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g = reduction(C, g1 + g2)
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return superelliptic_form(C, g)
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def __sub__(self, other):
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C = self.curve
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g1 = self.form
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g2 = other.form
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g = reduction(C, g1 - g2)
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return superelliptic_form(C, g)
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def __neg__(self):
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C = self.curve
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g = self.form
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return superelliptic_form(C, -g)
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def __repr__(self):
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g = self.form
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if len(str(g)) == 1:
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return str(g) + ' dx'
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return '('+str(g) + ') dx'
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def __rmul__(self, constant):
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C = self.curve
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omega = self.form
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return superelliptic_form(C, constant*omega)
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def cartier(self):
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'''Computes Cartier operator on the form. Idea: y^m = f(x) -> y^(p^r - 1) = f(x)^M, where r = ord_p(m),
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M = (p^r - 1)/m. Thus h(x)/y^j dx = h(x) f(x)^(M*j)/y^(p^r * j) dx. Thus C(h(x)/y^j dx) = 1/y^(p^(r-1)*j) C(h(x) f(x)^(M*j) dx).'''
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C = self.curve
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m = C.exponent
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p = C.characteristic
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f = C.polynomial
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F = C.base_ring
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Rx.<x> = PolynomialRing(F)
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Fx = FractionField(Rx)
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FxRy.<y> = PolynomialRing(Fx)
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Fxy = FractionField(FxRy)
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result = 0*C.dx
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mult_order = Integers(m)(p).multiplicative_order()
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M = Integer((p^(mult_order)-1)/m)
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for j in range(0, m):
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fct_j = self.jth_component(j)
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h = Fx(fct_j*f^(M*j))
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h_denom = h.denominator()
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h *= (h_denom)^(p)
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h = Rx(h)
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j1 = (p^(mult_order-1)*j)%m
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B = floor(p^(mult_order-1)*j/m)
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P = polynomial_part(p, h)
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if F.cardinality() != p:
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d = P.degree()
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P = sum(P[i].nth_root(p)*x^i for i in range(0, d+1))
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result += superelliptic_form(C, P/(f^B*y^(j1)*h_denom))
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return result
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def serre_duality_pairing(self, fct, prec=20):
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'''Compute Serre duality pairing of the form with a cohomology class in H1(X, OX) represented by function fct.'''
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result = 0
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C = self.curve
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delta = C.nb_of_pts_at_infty
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for i in range(delta):
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result += (fct*self).expansion_at_infty(place=i, prec=prec)[-1]
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return -result
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def coordinates(self, basis = 0):
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"""Find coordinates of the given holomorphic form self in terms of the basis forms in a list holo."""
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C = self.curve
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if basis == 0:
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basis = C.holomorphic_differentials_basis()
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Fxy, Rxy, x, y = C.fct_field
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# We need to have only polynomials to use monomial_coefficients in linear_representation_polynomials,
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# and sometimes basis elements have denominators. Thus we multiply by them.
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denom = LCM([denominator(omega.form) for omega in basis])
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basis = [denom*omega.form for omega in basis]
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self_with_no_denominator = denom*self.form
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return linear_representation_polynomials(Rxy(self_with_no_denominator), [Rxy(omega) for omega in basis])
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def jth_component(self, j):
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'''If self = sum_j h_j(x)/y^j dx, output is h_j(x).'''
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g = self.form
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C = self.curve
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m = C.exponent
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F = C.base_ring
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Rx.<x> = PolynomialRing(F)
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Fx = FractionField(Rx)
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FxRy.<y> = PolynomialRing(Fx)
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g = reduction(C, y^m*g)
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g = FxRy(g)
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if j == 0:
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return g.monomial_coefficient(y^(0))/C.polynomial
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return g.monomial_coefficient(y^(m-j))
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def is_regular_on_U0(self):
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C = self.curve
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F = C.base_ring
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m = C.exponent
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Rx.<x> = PolynomialRing(F)
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for j in range(0, m):
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if self.jth_component(j) not in Rx:
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return False
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return True
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def is_regular_on_Uinfty(self):
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C = self.curve
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F = C.base_ring
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m = C.exponent
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f = C.polynomial
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r = f.degree()
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delta = GCD(m, r)
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M = m/delta
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R = r/delta
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for j in range(1, m):
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A = self.jth_component(j)
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d = degree_of_rational_fctn(A, F)
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if(-d*M + j*R -(M+1)<0):
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return False
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return True
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def expansion_at_infty(self, place = 0, prec=10):
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g = self.form
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C = self.curve
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g = superelliptic_function(C, g)
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F = C.base_ring
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Rt.<t> = LaurentSeriesRing(F, default_prec=prec)
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g = Rt(g.expansion_at_infty(place = place, prec=prec))
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return g*C.dx_series[place]
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def expansion(self, pt, prec = 50):
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'''Expansion in the completed ring of the point pt. If pt is an integer, it means the corresponding place at infinity.'''
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if pt in ZZ:
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return self.expansion_at_infty(place=pt, prec=prec)
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C = self.curve
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dx_series = C.x.expansion(pt = pt, prec=prec).derivative()
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aux_fct = superelliptic_function(C, self.form)
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return aux_fct.expansion(pt=pt, prec=prec)*dx_series
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def residue(self, place = 0, prec=30):
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return self.expansion_at_infty(place = place, prec=prec)[-1]
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def reduce(self):
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fct = self.form
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C = self.curve
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fct = reduction(C, fct)
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return superelliptic_form(C, fct)
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def reduce2(self):
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fct = self.form
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C = self.curve
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m = C.exponent
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F = C.base_ring
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Rxy.<x, y> = PolynomialRing(F, 2)
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Fxy = FractionField(Rxy)
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fct = reduction(C, Fxy(y^m*fct))
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return superelliptic_form(C, fct/y^m)
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def int(self):
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'''Computes an "integral" of a form dg. Idea: y^m = f(x) -> y^(p^r - 1) = f(x)^M, where r = ord_p(m),
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M = (p^r - 1)/m. Thus h(x)/y^j dx = h(x) f(x)^(M*j)/y^(p^r * j) dx. Thus int(h(x)/y^j dx) = 1/y^(p^(r-1)*j) int(h(x) f(x)^(M*j) dx).'''
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C = self.curve
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m = C.exponent
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p = C.characteristic
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f = C.polynomial
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F = C.base_ring
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Rx.<x> = PolynomialRing(F)
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Fx = FractionField(Rx)
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FxRy.<y> = PolynomialRing(Fx)
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Fxy = FractionField(FxRy)
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result = 0*C.x
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mult_order = Integers(m)(p).multiplicative_order()
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M = Integer((p^(mult_order)-1)/m)
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for j in range(0, m):
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fct_j = self.jth_component(j)
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h = Fx(fct_j*f^(M*j))
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h_denom = h.denominator()
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h *= (h_denom)^(p)
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h = Rx(h)
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j1 = (p^(mult_order)*j)%m
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B = floor(p^(mult_order)*j/m)
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result += superelliptic_function(C, h.integral()/(f^(B)*y^(j1)*h_denom^p))
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return result
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def inv_cartier(omega):
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'''If omega is regular, return form eta such that Cartier(eta) = omega'''
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omega_regular = omega.regular_form()
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C = omega.curve
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p = C.characteristic
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return (omega_regular.dx)^p*C.x^(p-1)*C.dx + (omega_regular.dy)^p*C.y^(p-1)*C.y.diffn()
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def valuation(self, place = 0):
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'''Return valuation at i-th place at infinity.'''
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C = self.curve
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F = C.base_ring
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Rt.<t> = LaurentSeriesRing(F)
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return Rt(self.expansion_at_infty(place = place)).valuation() |