►where and the square roots are real and positive when the lattice is rectangular; otherwise they are determined by continuity from the rectangular case.
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►The lattice invariants are defined by
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►The lattice roots satisfy the cubic equation
…and are denoted by .
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►Let , or equivalently be nonzero, or be distinct.
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►Conversely, , , and the set are determined uniquely by the lattice
independently of the choice of generators.
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►(23.10.8) continues to hold when , , are permuted cyclically.
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►Also, when is replaced by the lattice invariants and are divided by and , respectively.
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and are meromorphic functions with poles at the lattice points.
is even and is odd.
…The function is entire and odd, with simple zeros at the lattice points.
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►The Weierstrass function plays a similar role for cubic potentials in canonical form .
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►Airault et al. (1977) applies the function to an integrable classical many-body problem, and relates the solutions to nonlinear partial differential equations.
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►where are the corresponding Cartesian coordinates and , , are constants.
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►Line graphs of the Weierstrass functions , , and , illustrating the lemniscatic and equianharmonic cases.
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►►►Figure 23.4.7:
with , for , = 0.
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Magnify
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►Surfaces for the Weierstrass functions , , and .
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►Figure 23.4.8:
with , for , , .
(The scaling makes the lattice appear to be square.)
Magnify3DHelp
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►2 in Abramowitz and Stegun (1964) gives values of , , and to 7 or 8D in the rectangular and rhombic cases, normalized so that and (rectangular case), or and (rhombic case), for = 1.
…05, and in the case of the user may deduce values for complex by application of the addition theorem (23.10.1).
►Abramowitz and Stegun (1964) also includes other tables to assist the computation of the Weierstrass functions, for example, the generators as functions of the lattice invariants and .
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