most recent 30 from http://mathoverflow.net 2013-05-24T04:14:02Z http://mathoverflow.net/feeds/user/19477 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/105026/semirings-with-subtractive-primes Peyman Nasehpour 2012-08-19T07:05:18Z 2012-12-08T16:08:11Z

<p>Let $S$ be a commutative semiring with identity such that each prime ideal of $S$ is subtractive. Does this imply all ideals of $S$ to be subtractive?</p> <p>By a commutative semiring with identity I mean an algebraic structure, consisting of a nonempty set $S$ with two operations of addition and multiplication such that the following conditions are satisfied:</p> <p>$(S,+)$ is a commutative monoid with identity element $0$; $(S,.)$ is a commutative monoid with identity element $1 \not= 0$; Multiplication distributes over addition, i.e. $a(b+c) = ab + ac$ for all $a,b,c \in S$; The element $0$ is the absorbing element of the multiplication, i.e. $s.0=0$ for all $s\in S$.</p> <p>A nonempty subset $I$ of a semiring $S$ is said to be an ideal of $S$, if $a+b \in I$ for all $a,b \in I$ and $sa \in I$ for all $s \in S$ and $a \in I$.</p> <p>A nonempty subset $P$ of a semiring $S$ is said to be a prime ideal of $S$, if $P \not= S$ is an ideal of $S$ such that $ab \in P$ implies either $a\in P$ or $b\in P$ for all $a,b \in S$.</p> <p>An ideal $I$ of a semiring $S$ is said to be subtractive, if $a+b \in I$ and $a \in I$ implies $b \in I$ for all $a,b \in S$.</p>