Rubio_de_francia/seminario.ipynb

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{
"cells": [
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"# Diagramas de Rudolf de curvas planas\n",
"\n",
"<p style=\"text-align:center\">Seminario Rubio de Francia</p>\n",
"\n",
"<p style=\"text-align:center\">Miguel Angel Marco Buzunariz</p>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Geometría algebraica\n",
"\n",
"Considerar un sistema de ecuaciones polinómicas\n",
"\n",
"$$f_1(x_1,\\ldots,x_n)$$\n",
"$$f_2(x_1,\\ldots,x_n)$$\n",
"$$\\vdots$$\n",
"$$f_m(x_1,\\ldots,x_m)$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"El conjunto $V$ de sus soluciones forman una *variedad algebraica*."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Problema general de la geometría algebraica\n",
"\n",
"Estudiar la geometría de $V$ usando la estructura algebraica de las ecuaciones que la definen."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Nos vamos a restringir a los casos más fáciles:"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"- $m=1, n=2$ (curvas planas)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"- $\\mathbb{K}=\\mathbb{C}$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Resultados clásicos conocidos"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"- Si la curva es lisa: teoría de las superficies de Riemann\n",
" - Superficies de género $g=\\frac{d(d-1)}{2}$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Ejemplo \n",
"\n",
"$y^2= x^2-1$\n",
"\n",
"![](hiperbola.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"La proyección sobre el eje $x$ es $2:1$ excepto en $x=\\pm 1$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Ejemplo\n",
"\n",
"![](supriemannelev-0.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Ejemplo\n",
"\n",
"<video data-autoplay src=\"supriemannelev.mp4\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Topología del encaje\n",
"\n",
"$C\\subseteq \\mathbb{C}^2$\n"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Codimensión 2: situación análoga a los nudos"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Uno de los invariantes principales es el grupo fundamental del complementario $\\pi_1(\\mathbb{C}^2\\setminus C)$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"![](monodtrenzas1.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"![](monodtrenzas2.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"![](monodtrenzas3.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas4.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas5.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas6.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas7.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas8.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Lema</b>\n",
" </h3>\n",
" <p>\n",
" Esta construcción determina un morfismo de grupos $\\pi_1(\\mathbb{C}\\setminus \\Delta)\\longrightarrow B_d$.\n",
" </p>\n",
"</div>\n",
"\n"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Definición</b>\n",
" </h3>\n",
" <p>\n",
" Este morfismo recibe el nombre de <i>monodromía de trenzas</i> de la curva.\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Se puede representar como una lista de trenzas correspondientes a una base geométrica de $\\pi_1(\\mathbb{C}\\setminus \\Delta)$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas9.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<video data-autoplay src=\"monodtrenzas10.webm\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Monodromía de trenzas\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Teorema</b> (Zariski-Van Kampen)\n",
" </h3>\n",
" <p>\n",
" El grupo fundamental del complementario $\\pi_1(\\mathbb{C}^2\\setminus C)$ es el cociente del grupo libre $F_d$ por la acción de la monodromía de trenzas.\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Teorema</b>\n",
" </h3>\n",
" <p>\n",
" La monodromía de trenzas determina completamente la topología del par $(\\mathbb{C}^2,C)$.\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Pares de Zariski\n",
"\n",
"La monodromía de trenzas es un objeto algebraico (morfismo de grupos) definido a partir de otro objeto algebraico (ideal en el anillo de polinomios)."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Definición</b>\n",
" </h3>\n",
" <p>\n",
" Dos curvas algebraicas $C_1$ y $C_2$ forman un <i>par de Zariski aritmético</i> si\n",
" <ul>\n",
" <li class=\"fragment\">Los polinomios que las definen $f_1,f_2$ son conjugados de Galois.</li>\n",
" <li class=\"fragment\">Los grupos fundamentales $\\pi_1(\\mathbb{C}^2\\setminus C_1)$ y $\\pi_1(\\mathbb{C}^2\\setminus C_1)$ son no isomorfos.</li>\n",
" </ul>\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Pares de Zariski\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Teorema</b> (ACG_)\n",
" </h3>\n",
" <p>\n",
" Existen pares de Zariski aritméticos\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Esto implica que la monodromía de trenzas (o el grupo fundamental) no se puede calcular de manera puramente algebraica."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Se necesitan cálculos **numéricos**, pero **certificados**."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo de la monodromía de trenzas\n",
"\n",
"Primer paso: elegir los caminos\n",
"\n",
"![](voronoi0.jpg)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo de la monodromía de trenzas\n",
"\n",
"Primer paso: elegir los caminos\n",
"\n",
"![](voronoi1.jpg)\n",
"\n",
"El *Diagrama de Voronoi* nos da segmentos que rodean los puntos del discriminante, acercándose lo menos posible."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo de la trenza sobre un segmento\n",
"\n",
"Mediante cambio de variable, podemos normalizar a $[0,1]$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"![](trenzasola.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo de la trenza sobre un segmento\n",
"\n",
"Mediante cambio de variable, podemos normalizar a $[0,1]$\n",
"\n",
"![](trenzapoligonal.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo de la trenza sobre un segmento\n",
"\n",
"Mediante cambio de variable, podemos normalizar a $[0,1]$\n",
"\n",
"![](trenzaentorno.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Aritmética intervalar\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Definición</b>\n",
" </h3>\n",
" <p>\n",
" Un <i>intervalo complejo</i> es un conjunto $$[r_0,r_1]+[i_0,i_1]\\cdot i:=\\{a+b\\cdot i \\mid a \\in [r_0,r_1], b\\in [i_0,i_1]\\}\\subseteq \\mathbb{C}$$\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Definición</b>\n",
" </h3>\n",
" <p>\n",
" Dado $Y\\subseteq \\mathbb{C}$, su <i>clausura intervalar</i> $[Y]$ es el menor intervalo que lo contiene.\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Se puede operar con intervalos tomando la clausura intervalar de las operaciones punto a punto."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Los intervalos con estas operaciones **no** forman un anillo (pero para ciertos efectos, se puede operar como si lo fuera)."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Criterio del intervalo de Newton\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Teorema</b>\n",
" </h3>\n",
" <p>\n",
" Sea $Y$ un intervalo complejo, $y0\\in Y$. Sea $f: Y\\longrightarrow \\mathbb{C}$ una función holomorfa, tal que $0\\in [f'(Y)]$. Si\n",
" $$\n",
" N(f,y_0,Y):=y_0-\\frac{f(y_0)}{[f'(Y)]}\\subseteq Y\n",
" $$\n",
" entonces $f$ tiene un único cero en $Y$. Además, este cero está en $N(f,y_0,Y)$.\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Podemos usar este teorema para asegurar que tenemos un entorno alrededor de una raíz aproximada, que contiene a la raíz auténtica, pero sin tocar a las demás raíces."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"Notar que, ya que estamos operando con intervalos, podemos usar intervalos en los propios coeficientes."
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Ejemplo\n",
"\n",
"$$f = [0.9,1.1]\\cdot y^2-1-x$$\n",
"$$y_0=1$$\n",
"$$Y=[0.5,1.5]$$\n",
"$$x_0=0$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"$$N(f,y_0,Y)=1-\\frac{[0.9,1.1]-1}{2\\cdot[0.9,1.1][0.5,1.5]}=$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"$$=1-\\frac{[-0.1,0.1]}{[0.9,3.3]}\\approx [0.888,1.111]$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Ejemplo: extender $x$ a un intervalo\n",
"\n",
"$$f = [0.9,1.1]\\cdot y^2-1-x$$\n",
"$$y_0=1$$\n",
"$$Y=[0.5,1.5]$$\n",
"$$x=[0,0.25]$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"$$N(f,y_0,Y)=1-\\frac{[0.9,1.1]-1-[0,0.25]}{2\\cdot[0.9,1.1][0.5,1.5]}=$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"$$=1-\\frac{[-0.35,0.1]}{[0.9,3.3]}\\approx [0.888,1.13888]$$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos1.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos2.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos3.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos4.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos5.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Cálculo numérico certificado de la trenza\n",
"\n",
"![](cubos6.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## SIROCCO: demostración"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"A.<x,y> = AffineSpace(QQ,2)\n",
"C = A.curve(y^2-x^3-x^2)\n",
"C.plot((x,-3,3),(y,-3,3))"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"show(C.fundamental_group())"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## SIROCCO: demostración"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"C2 = A.curve((x^2+y^2)^2+18*(x^2+y^2) - 27 -8*(x^3-3*x*y^2))\n",
"C2.plot((x,-3,3),(y,-3,3))"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"show(C2.fundamental_group())"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"Volviendo a las superficies de Riemann:\n",
"\n",
"![](diagramarudolfhiperbola2.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"Volviendo a las superficies de Riemann:\n",
"\n",
"![](diagramarudolfhiperbola1.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"<div class=\"thm\">\n",
" <h3>\n",
" <b>Definición</b> \n",
" </h3>\n",
" <p>\n",
" Sea $f\\in\\mathbb{C}[x,y]$, su <i>diagrama de Rudolf</i> es el conjunto\n",
" $$\\{x\\in\\mathbb{C} \\mid \\exists y_0\\neq y_1, Re(y_0)=Re(y_1), f(x,y_0)=f(x,y_1)=0\\}$$\n",
" </p>\n",
"</div>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"- Como conjunto de $\\mathbb{R}^2\\cong \\mathbb{C}$, es un conjunto semialgebraico"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"- En general, son difíciles de calcular"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"Diagrama de Rudolf de $(4z^3+12z+3-w^2)^2-8w-48z+52$"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "fragment"
}
},
"source": [
"<img src=\"diagramarudolforevkov.svg\" style=\"max-height:450px !important; height:450px;\"/>"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"![](laberinto0.png)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"## Diagramas de Rudolf\n",
"\n",
"![](laberinto1.svg)"
]
},
{
"cell_type": "markdown",
"metadata": {
"slideshow": {
"slide_type": "slide"
}
},
"source": [
"# Muchas gracias"
]
}
],
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"language": "sage",
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