DeRhamComputation/as_covers/holomorphic_combinations.sage

def holomorphic_combinations(S):
    """Given a list S of pairs (form, corresponding Laurent series at some pt), find their combinations holomorphic at that pt."""
    C_AS = S[0][0].curve
    p = C_AS.characteristic
    F = C_AS.base_ring
    prec = C_AS.prec
    Rt.<t> = LaurentSeriesRing(F, default_prec=prec)
    RtQ = FractionField(Rt)
    minimal_valuation = min([g[1].valuation() for g in S])
    if minimal_valuation >= 0:
        return [s[0] for s in S]
    list_of_lists = [] #to będzie lista złożona z list współczynników część nieholomorficznych rozwinięcia form z S
    for eta, eta_exp in S:
        a = -minimal_valuation + eta_exp.valuation()
        list_coeffs = a*[0] + eta_exp.list() + (-minimal_valuation)*[0]
        list_coeffs = list_coeffs[:-minimal_valuation]
        list_of_lists += [list_coeffs]
    M = matrix(F, list_of_lists)
    V = M.kernel() #chcemy wyzerować części nieholomorficzne, biorąc kombinacje form z S


    # Sprawdzamy, jakim formom odpowiadają elementy V.
    forms = []
    for vec in V.basis():
        forma_holo = 0*S[0][0]
        forma_holo_power_series = Rt(0)
        for vec_wspolrzedna, elt_S in zip(vec, S):
            eta = elt_S[0]
            #eta_exp = elt_S[1]
            forma_holo += vec_wspolrzedna*eta
            #forma_holo_power_series += vec_wspolrzedna*eta_exp
        forms += [forma_holo]
    return forms

def holomorphic_combinations_mixed(S):
    """Given a list S of pairs (form, corresponding Laurent series at some pt), find their combinations holomorphic at that pt."""
    C_AS = S[0][0].curve
    p = C_AS.characteristic
    F = C_AS.base_ring
    prec = C_AS.prec
    Rt.<t> = LaurentSeriesRing(F, default_prec=prec)
    RtQ = FractionField(Rt)
    minimal_valuation = min([g[1].valuation() for g in S])
    print(minimal_valuation)
    if minimal_valuation >= 0:
        return [s[0] for s in S]
    list_of_lists = [] #to będzie lista złożona z list współczynników część nieholomorficznych rozwinięcia form z S
    for eta, eta_exp in S:
        a = -minimal_valuation + eta_exp.valuation()
        list_coeffs = a*[0] + eta_exp.list() + (-minimal_valuation)*[0]
        list_coeffs = list_coeffs[:-minimal_valuation]
        list_of_lists += [list_coeffs]
    M = matrix(F, list_of_lists)
    V = M.kernel() #chcemy wyzerować części nieholomorficzne, biorąc kombinacje form z S


    # Sprawdzamy, jakim formom odpowiadają elementy V.
    forms = []
    for vec in V.basis():
        forma_holo = 0*S[0][0]
        forma_holo_power_series = Rt(0)
        res1 = 0*C_AS.dx
        res2 = 0*C_AS.x
        res = 0*C_AS.dx
        for vec_wspolrzedna, elt_S in zip(vec, S):
            eta = elt_S[0]
            if isinstance(eta, as_form):
                res += vec_wspolrzedna*eta
                res1 += vec_wspolrzedna*eta
            if isinstance(eta, as_function):
                res += vec_wspolrzedna*eta.diffn()
                res2 += vec_wspolrzedna*eta
            #eta_exp = elt_S[1]
            #forma_holo_power_series += vec_wspolrzedna*eta_exp
        forms += [(res1, res2)]
    return forms

def holomorphic_combinations_fcts(S, pole_order):
    '''given a set S of (form, corresponding Laurent series at some pt), find their combinations holomorphic at that pt'''
    C_AS = S[0][0].curve
    p = C_AS.characteristic
    F = C_AS.base_ring
    prec = C_AS.prec
    Rt.<t> = LaurentSeriesRing(F, default_prec=prec)
    RtQ = FractionField(Rt)
    minimal_valuation = min([Rt(g[1]).valuation() for g in S])
    if minimal_valuation >= -pole_order:
        return [s[0] for s in S]
    list_of_lists = [] #to będzie lista złożona z list współczynników część nieholomorficznych rozwinięcia form z S
    for eta, eta_exp in S:
            a = -minimal_valuation + Rt(eta_exp).valuation()
            if eta_exp !=0:
                list_coeffs = a*[0] + Rt(eta_exp).list() + (-minimal_valuation)*[0]
                list_coeffs = list_coeffs[:-minimal_valuation - pole_order]
            else:
                list_coeffs = (-minimal_valuation - pole_order)*[0]
            list_of_lists += [list_coeffs]
    M = matrix(F, list_of_lists)
    V = M.kernel() #chcemy wyzerować części nieholomorficzne, biorąc kombinacje form z S


    # Sprawdzamy, jakim formom odpowiadają elementy V.
    forms = []
    for vec in V.basis():
        forma_holo = 0*C_AS.x
        forma_holo_power_series = Rt(0)
        for vec_wspolrzedna, elt_S in zip(vec, S):
            eta = elt_S[0]
            #eta_exp = elt_S[1]
            forma_holo += vec_wspolrzedna*eta
            #forma_holo_power_series += vec_wspolrzedna*eta_exp
        forms += [forma_holo]
    return forms

def holomorphic_combinations_forms(S, pole_order):
    '''given a set S of (form, corresponding Laurent series at some pt), find their combinations holomorphic at that pt'''
    C_AS = S[0][0].curve
    p = C_AS.characteristic
    F = C_AS.base_ring
    prec = C_AS.prec
    Rt.<t> = LaurentSeriesRing(F, default_prec=prec)
    RtQ = FractionField(Rt)
    minimal_valuation = min([Rt(g[1]).valuation() for g in S])
    if minimal_valuation >= -pole_order:
        return [s[0] for s in S]
    list_of_lists = [] #to będzie lista złożona z list współczynników część nieholomorficznych rozwinięcia form z S
    for eta, eta_exp in S:
        a = -minimal_valuation + Rt(eta_exp).valuation()
        list_coeffs = a*[0] + Rt(eta_exp).list() + (-minimal_valuation)*[0]
        list_coeffs = list_coeffs[:-minimal_valuation - pole_order]
        list_of_lists += [list_coeffs]
    M = matrix(F, list_of_lists)
    V = M.kernel() #chcemy wyzerować części nieholomorficzne, biorąc kombinacje form z S


    # Sprawdzamy, jakim formom odpowiadają elementy V.
    forms = []
    for vec in V.basis():
        forma_holo = 0*C_AS.dx
        forma_holo_power_series = Rt(0)
        for vec_wspolrzedna, elt_S in zip(vec, S):
            eta = elt_S[0]
            #eta_exp = elt_S[1]
            forma_holo += vec_wspolrzedna*eta
            #forma_holo_power_series += vec_wspolrzedna*eta_exp
        forms += [forma_holo]
    return forms

#print only forms that are log at the branch pts, but not holomorphic