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sav08:notes_on_congruences [2009/05/06 10:04]
vkuncak
sav08:notes_on_congruences [2009/05/06 11:56]
vkuncak
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 We assume no relation symbols other than congruence itself. ​ (We represent a predicate $p(x_1,​\ldots,​x_n)$ as $f_p(x_1,​\ldots,​x_n)=true$.) We assume no relation symbols other than congruence itself. ​ (We represent a predicate $p(x_1,​\ldots,​x_n)$ as $f_p(x_1,​\ldots,​x_n)=true$.)
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 ===== Intersection of Congruences ===== ===== Intersection of Congruences =====
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 \[\begin{array}{rcl} \[\begin{array}{rcl}
  ​\bigwedge_{i=0}^n (x_i,y_1) \in \bigcap S & \rightarrow & \bigwedge_{i=0}^n (x_i,y_1) \in r_1,r_2 \\  ​\bigwedge_{i=0}^n (x_i,y_1) \in \bigcap S & \rightarrow & \bigwedge_{i=0}^n (x_i,y_1) \in r_1,r_2 \\
- ​r_1,​r_2 ~~ \text{congruence relations} & \rightarrow & f(x_1,​\ldots,​ x_n) f(y_1,​\ldots,​ y_n) \in r_1,r_2 \\+ ​r_1,​r_2 ~~ \text{congruence relations} & \rightarrow & (f(x_1,​\ldots,​ x_n)f(y_1,​\ldots,​ y_n)) \in r_1,r_2 \\
  & \rightarrow & f(x_1,​\ldots,​ x_n) = f(y_1,​\ldots,​ y_n) \in \bigcap S  & \rightarrow & f(x_1,​\ldots,​ x_n) = f(y_1,​\ldots,​ y_n) \in \bigcap S
 \end{array} \] \end{array} \]