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| -rw-r--r-- | ac/n.lyx | 14 | ||||
| -rw-r--r-- | ac/n3.lyx | 1131 |
2 files changed, 1145 insertions, 0 deletions
@@ -210,5 +210,19 @@ filename "n2.lyx" \end_layout +\begin_layout Chapter +Módulos +\end_layout + +\begin_layout Standard +\begin_inset CommandInset include +LatexCommand input +filename "n3.lyx" + +\end_inset + + +\end_layout + \end_body \end_document diff --git a/ac/n3.lyx b/ac/n3.lyx new file mode 100644 index 0000000..6332d29 --- /dev/null +++ b/ac/n3.lyx @@ -0,0 +1,1131 @@ +#LyX 2.3 created this file. For more info see http://www.lyx.org/ +\lyxformat 544 +\begin_document +\begin_header +\save_transient_properties true +\origin unavailable +\textclass book +\begin_preamble +\input{../defs} +\end_preamble +\use_default_options true +\maintain_unincluded_children false +\language spanish +\language_package default +\inputencoding auto +\fontencoding global +\font_roman "default" "default" +\font_sans "default" "default" +\font_typewriter "default" "default" +\font_math "auto" "auto" +\font_default_family default +\use_non_tex_fonts false +\font_sc false +\font_osf false +\font_sf_scale 100 100 +\font_tt_scale 100 100 +\use_microtype false +\use_dash_ligatures true +\graphics default +\default_output_format default +\output_sync 0 +\bibtex_command default +\index_command default +\paperfontsize default +\spacing single +\use_hyperref false +\papersize default +\use_geometry false +\use_package amsmath 1 +\use_package amssymb 1 +\use_package cancel 1 +\use_package esint 1 +\use_package mathdots 1 +\use_package mathtools 1 +\use_package mhchem 1 +\use_package stackrel 1 +\use_package stmaryrd 1 +\use_package undertilde 1 +\cite_engine basic +\cite_engine_type default +\biblio_style plain +\use_bibtopic false +\use_indices false +\paperorientation portrait +\suppress_date false +\justification true +\use_refstyle 1 +\use_minted 0 +\index Index +\shortcut idx +\color #008000 +\end_index +\secnumdepth 3 +\tocdepth 3 +\paragraph_separation indent +\paragraph_indentation default +\is_math_indent 0 +\math_numbering_side default +\quotes_style french +\dynamic_quotes 0 +\papercolumns 1 +\papersides 1 +\paperpagestyle default +\tracking_changes false +\output_changes false +\html_math_output 0 +\html_css_as_file 0 +\html_be_strict false +\end_header + +\begin_body + +\begin_layout Standard +Dado un anillo +\begin_inset Formula $A$ +\end_inset + +, un +\series bold +módulo +\series default + sobre +\begin_inset Formula $A$ +\end_inset + + o +\series bold + +\begin_inset Formula $A$ +\end_inset + +-módulo +\series default + +\begin_inset Formula $_{A}M$ +\end_inset + + es una terna +\begin_inset Formula $(M,+,\cdot)$ +\end_inset + + donde +\begin_inset Formula $(M,+)$ +\end_inset + + es un grupo abeliano y +\begin_inset Formula $\cdot:A\times M\to M$ +\end_inset + + es una operación llamada +\series bold +producto por escalares +\series default + tal que para +\begin_inset Formula $a,b\in A$ +\end_inset + + y +\begin_inset Formula $m,n\in M$ +\end_inset + +: +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $1m=m$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $(ab)m=a(bm)$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $(a+b)m=am+bm$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $a(m+n)=am+an$ +\end_inset + +. +\end_layout + +\begin_layout Standard +Propiedades: +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $0m=0$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $1m=(1+0)m=1m+0m$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Enumerate +\begin_inset Formula $a0=0$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $a0=a(0+0)=a0+a0$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Enumerate +\begin_inset Formula $-(am)=(-a)m=a(-m)$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $am+(-a)m=(a-a)m=0m=0$ +\end_inset + +, +\begin_inset Formula $am+a(-m)=a(m-m)=a0=0$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Standard +Llamamos +\begin_inset Formula $_{A}\text{Mod}$ +\end_inset + + a la clase de los módulos sobre +\begin_inset Formula $A$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Dado un cuerpo +\begin_inset Formula $K$ +\end_inset + +, la clase de espacios vectoriales sobre +\begin_inset Formula $K$ +\end_inset + + es +\begin_inset Formula $_{K}\text{Vect}=_{K}\text{Mod}$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +La clase de grupos abelianos es +\begin_inset Formula $\text{GrAb}=_{\mathbb{Z}}\text{Mod}$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +Un +\begin_inset Formula $\mathbb{Z}$ +\end_inset + +-módulo es un grupo abeliano con un producto por escalares de +\begin_inset Formula $\mathbb{Z}$ +\end_inset + + y este producto debe cumplir +\begin_inset Formula $(a+1)m=am+a$ +\end_inset + + y +\begin_inset Formula $(-a)m=a(-m)$ +\end_inset + +, por lo que se puede definir de una y sólo una forma. +\end_layout + +\end_deeper +\begin_layout Enumerate +Llamamos +\series bold + +\begin_inset Formula $A$ +\end_inset + +-módulo regular +\series default + a +\begin_inset Formula $_{A}A$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Llamamos +\series bold +anulador +\series default + de +\begin_inset Formula $_{A}M$ +\end_inset + + en +\begin_inset Formula $X\subseteq A$ +\end_inset + + a +\begin_inset Formula $\text{ann}_{M}(X)\coloneqq\{m\in M:Xm=0\}\leq_{A}M$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Si +\begin_inset Formula $\{M_{i}\}_{i\in I}$ +\end_inset + + es una familia de +\begin_inset Formula $A$ +\end_inset + +-módulos, +\begin_inset Formula $\prod_{i\in I}M_{i}$ +\end_inset + + es un +\begin_inset Formula $A$ +\end_inset + +-módulo con las operaciones componente a componente, y también lo es la + +\series bold +suma directa +\series default + ( +\series bold +externa +\series default +) +\begin_inset Formula +\[ +\bigoplus_{i\in I}M_{i}\coloneqq\left\{ x\in\prod_{i\in I}M_{i}:\{i\in I:x_{i}\neq0\}\text{ finito}\right\} . +\] + +\end_inset + + +\end_layout + +\begin_layout Enumerate +Dados un conjunto +\begin_inset Formula $I$ +\end_inset + + y un +\begin_inset Formula $A$ +\end_inset + +-módulo +\begin_inset Formula $M$ +\end_inset + +, llamamos +\begin_inset Formula $M^{I}\coloneqq\prod_{i\in I}M$ +\end_inset + + y +\begin_inset Formula $M^{(I)}\coloneqq\bigoplus_{i\in I}M$ +\end_inset + +. + Llamamos +\series bold + +\begin_inset Formula $A$ +\end_inset + +-módulo libre de rango +\begin_inset Formula $n$ +\end_inset + + +\series default + a +\begin_inset Formula $_{A}A^{n}$ +\end_inset + +, que si +\begin_inset Formula $A$ +\end_inset + + es un cuerpo es el espacio vectorial +\begin_inset Formula $A^{n}$ +\end_inset + +. +\end_layout + +\begin_layout Section +Submódulos +\end_layout + +\begin_layout Standard +\begin_inset Formula $N\subseteq_{A}M$ +\end_inset + + es un +\series bold +submódulo +\series default + de +\begin_inset Formula $_{A}M$ +\end_inset + + o un +\series bold + +\begin_inset Formula $A$ +\end_inset + +-submódulo +\series default + de +\begin_inset Formula $M$ +\end_inset + +, +\begin_inset Formula $N\leq_{A}M$ +\end_inset + +, si es un subgrupo de +\begin_inset Formula $M$ +\end_inset + + cerrado para el producto por escalares, si y sólo si +\begin_inset Formula $0\in N$ +\end_inset + + y +\begin_inset Formula $N$ +\end_inset + + es cerrado para +\series bold +combinaciones +\begin_inset Formula $A$ +\end_inset + +-lineales +\series default +, en cuyo caso +\begin_inset Formula $N$ +\end_inset + + es un módulo. +\end_layout + +\begin_layout Itemize +\begin_inset Argument item:1 +status open + +\begin_layout Plain Layout +\begin_inset Formula $\implies]$ +\end_inset + + +\end_layout + +\end_inset + + +\begin_inset Formula $N\neq\emptyset$ +\end_inset + + y, para +\begin_inset Formula $n\in N$ +\end_inset + +, +\begin_inset Formula $1n=(1+0)n=1n+0n\implies0n=0\in N$ +\end_inset + +, y es claro que es cerrado para combinaciones +\begin_inset Formula $A$ +\end_inset + +-lineales. +\end_layout + +\begin_layout Itemize +\begin_inset Argument item:1 +status open + +\begin_layout Plain Layout +\begin_inset Formula $\impliedby]$ +\end_inset + + +\end_layout + +\end_inset + +Claramente es cerrado para la suma y el producto, y también para el opuesto + porque si +\begin_inset Formula $n\in N$ +\end_inset + + entonces +\begin_inset Formula $-n=(-1)n\in N$ +\end_inset + +, ya que +\begin_inset Formula $n+(-1)n=(1-1)n=0n=0$ +\end_inset + +. +\end_layout + +\begin_layout Standard +Llamamos +\begin_inset Formula ${\cal L}(_{A}M)$ +\end_inset + + al conjunto de +\begin_inset Formula $A$ +\end_inset + +-submódulos de +\begin_inset Formula $M$ +\end_inset + + ordenado por inclusión, que es un retículo en la que el ínfimo es la intersecci +ón y el supremo es la suma. +\begin_inset Note Note +status open + +\begin_layout Plain Layout +TODO definida más adelante. + Añadir demostración. +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Standard +Ejemplos: +\end_layout + +\begin_layout Enumerate +Dado un cuerpo +\begin_inset Formula $K$ +\end_inset + +, un +\begin_inset Formula $K$ +\end_inset + +-submódulo es un subespacio vectorial. +\end_layout + +\begin_layout Enumerate +Un +\begin_inset Formula $\mathbb{Z}$ +\end_inset + +-submódulo es un subgrupo abeliano. +\end_layout + +\begin_layout Enumerate +Todo módulo +\begin_inset Formula $_{A}M$ +\end_inset + + tiene al menos los submódulos 0 y +\begin_inset Formula $_{A}M$ +\end_inset + +, y puede no haber más. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $_{\mathbb{Z}}\mathbb{Z}_{2}$ +\end_inset + + no tiene más. +\end_layout + +\end_deeper +\begin_layout Enumerate +Los submódulos del módulo regular son los ideales, +\begin_inset Formula ${\cal L}(_{A}A)={\cal L}(A)$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Si +\begin_inset Formula $A$ +\end_inset + + es subanillo de +\begin_inset Formula $B$ +\end_inset + +, +\begin_inset Formula $B$ +\end_inset + + es un +\begin_inset Formula $A$ +\end_inset + +-módulo tomando como producto por escalares el producto en +\begin_inset Formula $B$ +\end_inset + +. + En general +\begin_inset Formula ${\cal L}(_{A}B)\neq{\cal L}(_{B}B)$ +\end_inset + +. + Por ejemplo, +\begin_inset Formula $\mathbb{Q}$ +\end_inset + + solo tiene dos +\begin_inset Formula $\mathbb{Q}$ +\end_inset + +-submódulos (sus ideales) pero tiene muchos +\begin_inset Formula $\mathbb{Z}$ +\end_inset + +-submódulos (sus subgrupos), y dados un anillo +\begin_inset Formula $A$ +\end_inset + + y +\begin_inset Formula $n\in\mathbb{N}$ +\end_inset + +, +\begin_inset Formula $\{f\in A[X]:\text{gr}f\leq n\}$ +\end_inset + + es un submódulo de +\begin_inset Formula $_{A}A[X]$ +\end_inset + + pero no de +\begin_inset Formula $_{A[X]}A[X]$ +\end_inset + +. + +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $\text{ann}_{M}(X)\leq_{A}M$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $\bigoplus_{i\in I}M_{i}\leq_{A}\prod_{i\in I}M_{i}$ +\end_inset + +. +\end_layout + +\begin_layout Standard +Si +\begin_inset Formula $N\leq_{A}M$ +\end_inset + +, +\begin_inset Formula $M/N\coloneqq\{\overline{m}\coloneqq m+N\}_{m\in M}$ +\end_inset + + es un +\begin_inset Formula $A$ +\end_inset + +-módulo con la suma y el producto heredados, el +\series bold +módulo cociente +\series default + de +\begin_inset Formula $M$ +\end_inset + + por +\begin_inset Formula $N$ +\end_inset + +. + +\series bold +Demostración: +\series default + Para +\begin_inset Formula $m,m',n,n'\in M$ +\end_inset + + y +\begin_inset Formula $a\in A$ +\end_inset + + con +\begin_inset Formula $m-m',n-n'\in N$ +\end_inset + +, +\begin_inset Formula $\overline{m}+\overline{n}=\overline{m+n}=\overline{m+n+(m'-m+n'-n)}=\overline{m'+n'}=\overline{m'}+\overline{n'}$ +\end_inset + + y +\begin_inset Formula $a\overline{m}=\overline{am}=\overline{am+a(m'-m)}=\overline{am'}=a\overline{m'}$ +\end_inset + +, por lo que las operaciones están bien definidas, y es fácil ver que se + cumplen los axiomas de +\begin_inset Formula $A$ +\end_inset + +-módulo. +\end_layout + +\begin_layout Enumerate +Dado un cuerpo +\begin_inset Formula $K$ +\end_inset + +, el módulo cociente de +\begin_inset Formula $_{K}V$ +\end_inset + + por +\begin_inset Formula $U\leq_{K}V$ +\end_inset + + es el espacio vectorial cociente. +\end_layout + +\begin_layout Enumerate +El módulo cociente de +\begin_inset Formula $_{\mathbb{Z}}G$ +\end_inset + + por +\begin_inset Formula $H\leq_{\mathbb{Z}}G$ +\end_inset + + es el grupo cociente. +\end_layout + +\begin_layout Section +Homomorfismos +\end_layout + +\begin_layout Standard +Un +\series bold +homomorfismo de +\begin_inset Formula $A$ +\end_inset + +-módulos +\series default +, +\series bold + +\begin_inset Formula $A$ +\end_inset + +-homomorfismo +\series default + o +\series bold +aplicación +\begin_inset Formula $A$ +\end_inset + +-lineal +\series default + entre +\begin_inset Formula $_{A}M$ +\end_inset + + y +\begin_inset Formula $_{A}N$ +\end_inset + + es un homomorfismo de grupos abelianos +\begin_inset Formula $f:M\to N$ +\end_inset + + que conserva el producto por escalares, y llamamos +\begin_inset Formula $\text{Hom}_{A}(M,N)$ +\end_inset + + al conjunto de los +\begin_inset Formula $A$ +\end_inset + +-homomorfismos de +\begin_inset Formula $M$ +\end_inset + + a +\begin_inset Formula $N$ +\end_inset + +, que es un grupo abeliano con la suma. + El +\series bold +núcleo +\series default + de un +\begin_inset Formula $A$ +\end_inset + +-homomorfismo +\begin_inset Formula $f$ +\end_inset + + es +\begin_inset Formula $\ker f\coloneqq f^{-1}(0)$ +\end_inset + +. + Propiedades: +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $f$ +\end_inset + + es inyectivo si y sólo si +\begin_inset Formula $\ker f=0$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Enumerate +\begin_inset Argument item:1 +status open + +\begin_layout Plain Layout +\begin_inset Formula $\implies]$ +\end_inset + + +\end_layout + +\end_inset + + +\begin_inset Formula $f(x)=0=f(0)\implies x=0$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +\begin_inset Argument item:1 +status open + +\begin_layout Plain Layout +\begin_inset Formula $\impliedby]$ +\end_inset + + +\end_layout + +\end_inset + + +\begin_inset Formula $f(a)=f(b)\implies f(a-b)=0\implies a-b=0$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Enumerate +Si +\begin_inset Formula $M'\leq_{A}M$ +\end_inset + +, +\begin_inset Formula $f(M')\leq_{A}N$ +\end_inset + +, y en particular +\begin_inset Formula $f(M)\leq_{A}N$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $f(M')$ +\end_inset + + contiene al +\begin_inset Formula $0=f(0)$ +\end_inset + + y sus combinaciones +\begin_inset Formula $A$ +\end_inset + +-lineales son la imagen de combinaciones +\begin_inset Formula $A$ +\end_inset + +-lineales en +\begin_inset Formula $M'$ +\end_inset + +, que están en +\begin_inset Formula $M'$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Enumerate +Si +\begin_inset Formula $N'\leq_{A}N$ +\end_inset + +, +\begin_inset Formula $f^{-1}(N')\leq_{A}M$ +\end_inset + +. +\end_layout + +\begin_deeper +\begin_layout Standard +\begin_inset Formula $f^{-1}(N')$ +\end_inset + + contiene al +\begin_inset Formula $0=f^{-1}(N')$ +\end_inset + +, y si +\begin_inset Formula $a_{1},\dots,a_{k}\in A$ +\end_inset + + y +\begin_inset Formula $m_{1},\dots,m_{k}\in f^{-1}(N')$ +\end_inset + +, +\begin_inset Formula $f(a_{1}m_{1}+\dots+a_{k}m_{k})=a_{1}f(m_{1})+\dots+a_{k}f(m_{k})\in N'$ +\end_inset + +. +\end_layout + +\end_deeper +\begin_layout Enumerate +La composición de +\begin_inset Formula $A$ +\end_inset + +-homomorfismos es un +\begin_inset Formula $A$ +\end_inset + +-homomorfismos. +\end_layout + +\begin_layout Standard +Un homomorfismo es un +\series bold +monomorfismo +\series default + si es inyectivo, un +\series bold +epimorfismo +\series default + si es suprayectivo y un +\series bold +isomorfismo +\series default + si es biyectivo. + Las proyecciones canónicas +\begin_inset Formula $M\to M/N$ +\end_inset + + son epimorfismos. + Los inversos de isomorfismos son isomorfismos, y se dice que los módulos + involucrados son +\series bold +isomorfos +\series default +. + En efecto, si +\begin_inset Formula $f:M\to N$ +\end_inset + + es un +\begin_inset Formula $A$ +\end_inset + +-isomorfismo, +\begin_inset Formula $a\in A$ +\end_inset + + y +\begin_inset Formula $n,n'\in N$ +\end_inset + + con imágenes por +\begin_inset Formula $f^{-1}$ +\end_inset + + +\begin_inset Formula $m,m'\in M$ +\end_inset + +, +\begin_inset Formula $f(m+m')=f(m)+f(m')=n+n'$ +\end_inset + + y por tanto +\begin_inset Formula $f^{-1}(n+n')=m+m'=f^{-1}(n)+f^{-1}(n')$ +\end_inset + + y +\begin_inset Formula $f(am)=af(m)=an$ +\end_inset + + y por tanto +\begin_inset Formula $f^{-1}(an)=am=af^{-1}(n)$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +En un cuerpo +\begin_inset Formula $K$ +\end_inset + +, un +\begin_inset Formula $K$ +\end_inset + +-homomorfismo es una aplicación lineal. +\end_layout + +\begin_layout Enumerate +Un +\begin_inset Formula $\mathbb{Z}$ +\end_inset + +-homomorfismo es un homomorfismo de grupos. +\end_layout + +\begin_layout Enumerate +\begin_inset Formula $\text{Hom}_{\mathbb{Z}}(\mathbb{Z}_{2},\mathbb{Z}_{3})=0$ +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset Note Note +status open + +\begin_layout Plain Layout +TODO 4.1.8 +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Section +Restricción de escalares +\end_layout + +\begin_layout Standard +Dado un homomorfismo de anillos +\begin_inset Formula $f:A\to B$ +\end_inset + +, cada +\begin_inset Formula $B$ +\end_inset + +-módulo es un +\begin_inset Formula $A$ +\end_inset + +-módulo por +\series bold +restricción de escalares +\series default +, +\begin_inset Note Note +status open + +\begin_layout Plain Layout +TODO +\end_layout + +\end_inset + + +\end_layout + +\end_body +\end_document |
