Show that $χ_G(i − 1) = 0$












1












$begingroup$


Can you give me a hint for this exercise about Poset (Partially ordered set)?




Let $χ_G(t)$ be the characteristic polynomial of the graphical
arrangement $A_G$. Suppose that $χ_G(i) = 0$, where $i in
> mathbb{N}$
, $i > 1$. Show that $χ_G(i − 1) = 0$




By Enumerative Combinatorics from Stanley, chapter 3.11, I know that
the characteristic polynomial $χ_A(x)$ of the arrangement $A$ is $χ_A(x) = sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$.



And if $V = {v_1, . . . , v_p}$, then define the graphical arrangement $A_G$ to be the arrangement in $R^p$ with hyperplanes $x_i = x_j$, where $v_i$ and $v_j$ are adjacent vertices of $G$. The characteristic polynomial $χ_G(t)$ of the graphical arrangement $A_G$ is also the chromatic polynomial of the graph $G$. The value of $χ_G(t)$ at a positive integer $t$ equals the number of ways to color the vertices of the graph $G$ in $t$ colors so that all neighboring pairs of vertices have different colors.



If we have that $χ_G(i) = 0 Rightarrow χ_A(i)=sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$= 0$



I have to proceeding by backward induction?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
    $endgroup$
    – Shaun
    Nov 26 '18 at 1:25


















1












$begingroup$


Can you give me a hint for this exercise about Poset (Partially ordered set)?




Let $χ_G(t)$ be the characteristic polynomial of the graphical
arrangement $A_G$. Suppose that $χ_G(i) = 0$, where $i in
> mathbb{N}$
, $i > 1$. Show that $χ_G(i − 1) = 0$




By Enumerative Combinatorics from Stanley, chapter 3.11, I know that
the characteristic polynomial $χ_A(x)$ of the arrangement $A$ is $χ_A(x) = sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$.



And if $V = {v_1, . . . , v_p}$, then define the graphical arrangement $A_G$ to be the arrangement in $R^p$ with hyperplanes $x_i = x_j$, where $v_i$ and $v_j$ are adjacent vertices of $G$. The characteristic polynomial $χ_G(t)$ of the graphical arrangement $A_G$ is also the chromatic polynomial of the graph $G$. The value of $χ_G(t)$ at a positive integer $t$ equals the number of ways to color the vertices of the graph $G$ in $t$ colors so that all neighboring pairs of vertices have different colors.



If we have that $χ_G(i) = 0 Rightarrow χ_A(i)=sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$= 0$



I have to proceeding by backward induction?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
    $endgroup$
    – Shaun
    Nov 26 '18 at 1:25
















1












1








1





$begingroup$


Can you give me a hint for this exercise about Poset (Partially ordered set)?




Let $χ_G(t)$ be the characteristic polynomial of the graphical
arrangement $A_G$. Suppose that $χ_G(i) = 0$, where $i in
> mathbb{N}$
, $i > 1$. Show that $χ_G(i − 1) = 0$




By Enumerative Combinatorics from Stanley, chapter 3.11, I know that
the characteristic polynomial $χ_A(x)$ of the arrangement $A$ is $χ_A(x) = sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$.



And if $V = {v_1, . . . , v_p}$, then define the graphical arrangement $A_G$ to be the arrangement in $R^p$ with hyperplanes $x_i = x_j$, where $v_i$ and $v_j$ are adjacent vertices of $G$. The characteristic polynomial $χ_G(t)$ of the graphical arrangement $A_G$ is also the chromatic polynomial of the graph $G$. The value of $χ_G(t)$ at a positive integer $t$ equals the number of ways to color the vertices of the graph $G$ in $t$ colors so that all neighboring pairs of vertices have different colors.



If we have that $χ_G(i) = 0 Rightarrow χ_A(i)=sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$= 0$



I have to proceeding by backward induction?










share|cite|improve this question











$endgroup$




Can you give me a hint for this exercise about Poset (Partially ordered set)?




Let $χ_G(t)$ be the characteristic polynomial of the graphical
arrangement $A_G$. Suppose that $χ_G(i) = 0$, where $i in
> mathbb{N}$
, $i > 1$. Show that $χ_G(i − 1) = 0$




By Enumerative Combinatorics from Stanley, chapter 3.11, I know that
the characteristic polynomial $χ_A(x)$ of the arrangement $A$ is $χ_A(x) = sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$.



And if $V = {v_1, . . . , v_p}$, then define the graphical arrangement $A_G$ to be the arrangement in $R^p$ with hyperplanes $x_i = x_j$, where $v_i$ and $v_j$ are adjacent vertices of $G$. The characteristic polynomial $χ_G(t)$ of the graphical arrangement $A_G$ is also the chromatic polynomial of the graph $G$. The value of $χ_G(t)$ at a positive integer $t$ equals the number of ways to color the vertices of the graph $G$ in $t$ colors so that all neighboring pairs of vertices have different colors.



If we have that $χ_G(i) = 0 Rightarrow χ_A(i)=sum_{t in L(A)} mu(hat0,t)x^{dim(t)}$= 0$



I have to proceeding by backward induction?







order-theory






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 13 at 18:24









greedoid

42.4k1153105




42.4k1153105










asked Nov 26 '18 at 1:14









Vlllbbb1777Vlllbbb1777

113




113












  • $begingroup$
    I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
    $endgroup$
    – Shaun
    Nov 26 '18 at 1:25




















  • $begingroup$
    I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
    $endgroup$
    – Shaun
    Nov 26 '18 at 1:25


















$begingroup$
I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
$endgroup$
– Shaun
Nov 26 '18 at 1:25






$begingroup$
I don't understand why this was downvoted; on the face of it, it looks like a high quality question.
$endgroup$
– Shaun
Nov 26 '18 at 1:25












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