hojas jupyter

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Enrique Artal Bartolo 2024-02-14 15:00:57 +01:00
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@ -9,7 +9,7 @@
\usepackage{amsthm}
\usepackage[all]{xy}
\usepackage{mathrsfs}
\usepackage{enumitem}
\usepackage{enumitem}
\usepackage[T1]{fontenc}
\usepackage{color}
\usepackage{stmaryrd}
@ -56,7 +56,7 @@
\renewcommand{\thepropositionx}{\Alph{propositionx}} % "letter-numbered" theorems for Introduction
\theoremstyle{definition}
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}
\newtheorem{question}[theorem]{Question}
\newtheorem{example}[theorem]{Example}
@ -229,7 +229,7 @@
%%%%%%%%%%%%%%%%%%%%%
% Daniel's commands
% Daniel's commands
\newcommand{\Pnr}{\mathcal{P}^n_R}
\newcommand{\Pn}{\mathcal{P}^n_X}
\newcommand{\OXn}{\Omega^{(n)}_{X/\KK}}
@ -304,18 +304,23 @@
\maketitle
We propose the following general method to study germs of multiplicity 3 singular points of hypersurfaces. Firstly, consider an equation of the germ given by a monic polynomial $F = z^3 + a_1z + a_2z + a_3 \in \CC[[{\bf x}]][z]$ of degree 3 with respect to $z$. By means of a Tschirnhaus transformation, reduce $F$ to a monic equation $z^3 + b_2z + b_3$ that does not have terms of degree 2 with respect to $z$. Secondly, consider an embedded resolution $\pi: X \rightarrow \CC^d$ of the reduced divisor given by the product $b_2b_3$ of the coefficients of degree one and zero with respect to $z$. Consider the usual stratification of the pair $(X, (\pi \circ F)^{-1} \{F=0\})$ defined in terms of decomposition $\cup_{j \in J} E_j$ of $(\pi \circ F)^{-1} \{F=0\}$ into irreducible components. Pulling back $F$ under the map $\pi \times id$, we obtain for each stratum $E_I^\circ$ a quasi-trinomial local expression for $F$.
The local quasi-trinomial expression will be non degenerate with respect to its Newton polyhedron unless the monomials $M_1$, $M_2$ and their coefficients $c_1$ and $c_2$ satisfy a precise condition.
We propose the following general method to study germs of multiplicity 3 singular points of hypersurfaces. Firstly, consider an equation of the germ given by a monic polynomial $F = z^3 + a_1z + a_2z + a_3 \in \CC[[{\bf x}]][z]$ of degree 3 with respect to $z$. By means of a Tschirnhaus transformation, reduce $F$ to a monic equation $z^3 + b_2z + b_3$ that does not have terms of degree 2 with respect to $z$. Secondly, consider an embedded resolution $\pi: X \rightarrow \CC^d$ of the reduced divisor given by the product $b_2b_3$ of the coefficients of degree one and zero with respect to $z$. Consider the usual stratification of the pair $(X, (\pi \circ F)^{-1} \{F=0\})$ defined in terms of decomposition $\cup_{j \in J} E_j$ of $(\pi \circ F)^{-1} \{F=0\}$ into irreducible components. Pulling back $F$ under the map $\pi \times id$, we obtain for each stratum $E_I^\circ$ a quasi-trinomial local expression for $F$.
The local quasi-trinomial expression will be non degenerate with respect to its Newton polyhedron unless the monomials $M_1$, $M_2$ and their coefficients $c_1$ and $c_2$ satisfy a precise condition.
\section{The quasi-trimonial case}
In this section we consider the case of
\section{The quasi-trinomial case}
In this section we consider the case of
$$F = z^3 + M_1(c_1+A)z + M_2(c_2 + M_2) \in \CC[[{\bf x}]][z]$$
where $M_1={\bf x}^{m_1}$ and $M_2={\bf x}^{m_2}$ are monomials, $c_1,c_2 \in \CC^\ast$ and $A, B \in ({\bf x})\CC[[{\bf x}]]$
We distinguish the following two cases
\begin{itemize}
\item Assume that the monomials $M_1$ and $M2$ are not related by the divisibility relation, i.e., neither $M_1 \nmid M_2$ nor $M_1 \nmid M_2$.
\item Assume that the monomials $M_1$ and $M_2$ are not related by the divisibility relation, i.e., neither $M_1 \nmid M_2$ nor $M_1 \nmid M_2$.
In this case, the Newton polyhedra of $F$ contains a unique two dimensional compact face determined by the monomials $z^3$, $M_1z$ and $M_2$. Moreover, $F$ is non degenerate with respect to its Newton polyhedra.
\
@ -333,6 +338,20 @@ In this case, the Newton polyhedra of $F$ contains a unique two dimensional comp
\filldraw[black] (2,-1) circle (2pt) node[anchor=south west]{$m_1$};
\fill [yellow] (11,0,4)--(11,0,0)--(13,0,0)--(13,0,4)--(11,0,4);
\fill [yellow] (11,0,4)--(11,0,7)--(6,0,7)--(6,0,4)--(11,0,4);
\draw[gray, thick] (6,0,0) -- (6,0,7);
\draw[gray, thick] (6,0,0) -- (6,4,0);
\draw[gray, thick] (6,0,0) -- (13,0,0);
@ -380,7 +399,7 @@ In this case, the Newton polyhedra of $F$ contains a unique two dimensional comp
\item Assume that the monomials $M_1$ and $M_2$ are related by the divisibility relation, i.e., either $M_1 | M_2$ or $M_1 | M_2$. In this case the Newton polyhedron of $F$ is a polygonal path. We distinguish the following cases.
\item Assume that the monomials $M_1$ and $M_2$ are related by the divisibility relation, i.e., either $M_1 | M_2$ or $M_1 | M_2$. In this case the Newton polyhedron of $F$ is a polygonal path. We distinguish the following cases.
\
@ -430,6 +449,10 @@ In this case, the Newton polyhedra of $F$ contains a unique two dimensional comp
\fill [yellow] (28/3,0,4)--(28/3,0,8/3)--(11,0,8/3)--(11,0,0)--(6,0,0)--(6,0,4)--(28/3,0,4);
\draw[gray, thick] (6,0,0) -- (6,0,7);
\draw[gray, thick] (6,0,0) -- (6,4,0);
\draw[gray, thick] (6,0,0) -- (13,0,0);
@ -496,6 +519,7 @@ In this case, the Newton polyhedra of $F$ contains a unique two dimensional comp
\begin{tikzpicture}
\fill [yellow] (28/3,0,4)--(28/3,0,8/3)--(11,0,8/3)--(11,0,0)--(6,0,0)--(6,0,4)--(28/3,0,4);
@ -549,7 +573,7 @@ In this case, the Newton polyhedra of $F$ contains a unique two dimensional comp
\item If $M_1^3 = M_2^2$, the point corresponding to the monomial $M_1z$ lies in the unique dimensional compact face of the Newton polyhedron of $F$. The face equation is equal to
\item If $M_1^3 = M_2^2$, the point corresponding to the monomial $M_1z$ lies in the unique dimensional compact face of the Newton polyhedron of $F$. The face equation is equal to
$$z^3 + c_1z + c_2.$$
Therefore, $F$ is non degenerate with respect to its Newton polyhedron if and only if $3c_1 \ne 2c_2$.
@ -558,6 +582,8 @@ Therefore, $F$ is non degenerate with respect to its Newton polyhedron if and on
\fill [yellow] (28/3,0,4)--(28/3,0,8/3)--(11,0,8/3)--(11,0,0)--(6,0,0)--(6,0,4)--(28/3,0,4);
\draw[gray, thick] (6,0,0) -- (6,0,7);
@ -579,7 +605,9 @@ Therefore, $F$ is non degenerate with respect to its Newton polyhedron if and on
\draw[gray, thick] (6,3,0) -- (13,3,0);
\draw[gray, dashed] (6,1,3) -- (6,0,8/3);
\draw[gray, dashed] (6,1,8/3) -- (6,0,8/3);
\draw[gray, dashed] (28/3,0,0) -- (28/3,0,8/3);
\draw[gray, dashed] (6,1,8/3) -- (6,1,0);
\draw[gray, dashed] (28/3,1,0) -- (28/3,0,0);
@ -615,8 +643,8 @@ Therefore, $F$ is non degenerate with respect to its Newton polyhedron if and on
\end{itemize}
@ -625,4 +653,4 @@ Therefore, $F$ is non degenerate with respect to its Newton polyhedron if and on
\end{document}
\end{document}

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