Download Designing fair curves and surfaces: shape quality in by Nickolas S. Sapidis PDF

By Nickolas S. Sapidis

This state of the art learn of the options used for designing curves and surfaces for computer-aided layout functions specializes in the primary that reasonable shapes are constantly freed from unessential beneficial properties and are uncomplicated in layout. The authors outline equity mathematically, show how newly constructed curve and floor schemes warrantly equity, and help the person in choosing and elimination form aberrations in a floor version with out destroying the vital form features of the version. Aesthetic elements of geometric modeling are of important significance in business layout and modeling, fairly within the car and aerospace industries. Any engineer operating in computer-aided layout, computer-aided production, or computer-aided engineering probably want to upload this quantity to his or her library. Researchers who've a familiarity with simple ideas in computer-aided photograph layout and a few wisdom of differential geometry will locate this publication a precious reference.

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Extra resources for Designing fair curves and surfaces: shape quality in geometric modeling and computer-aided design

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P → P¯ : E(Qp ) → E(F We shall define a filtration E(Qp ) ⊃ E 0 (Qp ) ⊃ E 1 (Qp ) ⊃ · · · ⊃ E n (Qp ) ⊃ · · · and identify the quotients. First, define E 0 (Qp ) = {P | P¯ is nonsingular}. It is a subgroup because, as we observed on p26, a line through two nonsingular points on a cubic (or tangent to a nonsingular point), will meet the cubic again at a nonsingular point. Write E¯ ns for E¯ \ {any singular point}. The reduction map P → P¯ : E 0 (Qp ) → E¯ ns (Fp ) is a homomorphism, and we define E 1 (Qp ) be its kernel.

For any elliptic curve E over an algebraically closed field k of characteristic zero, E(k)n is a free Z/nZ-module of rank 2. Proof. There will exist an algebraically closed subfield k0 of finite transcendance degree over Q such that E arises from a curve E0 over k0 . Now k0 can be embedded into C, and so we can apply the next lemma (twice). 19. Let E be an elliptic curve over an algebraically closed field k, and let Ω be an algebraically closed field containing k. Then the map E(k) → E(Ω) induces an isomorphism on the torsion subgroups.

3 27 3 27 a = 2cd + ELLIPTIC CURVES 37 ´ron Models 9. Ne Consider an elliptic curve over Qp E : Y 2 Z = X 3 + aXZ 2 + bZ 3 , a, b ∈ Qp , ∆ = 4a3 + 27b2 = 0. After making a change of variables X → X/c2 , Y → Y /c3 , Z → Z, we can suppose that a, b ∈ Zp and ordp (∆) is minimal. We can think of E as defining a curve over Zp , which will be the best “model” of E over Zp among plane projective curves when p = 2, 3. However, when p = 2 or 3 we may be able to get a better model of E over Zp by allowing a more complicated equation.

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