Symbols:Q

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The Set of Rational Numbers

$\Q$

The set of rational numbers.


The $\LaTeX$ code for \(\Q\) is \Q  or \mathbb Q or \Bbb Q.


The Set of Non-Zero Rational Numbers

$\Q_{\ne 0}$

The set of non-zero rational numbers:

$\Q_{\ne 0} = \Q \setminus \left\{{0}\right\}$


The $\LaTeX$ code for \(\Q_{\ne 0}\) is \Q_{\ne 0}  or \mathbb Q_{\ne 0} or \Bbb Q_{\ne 0}.


Deprecated

$\Q^*$

The set of non-zero rational numbers:

$\Q^* = \Q \setminus \left\{{0}\right\}$


The $\LaTeX$ code for \(\Q^*\) is \Q^*  or \mathbb Q^* or \Bbb Q^*.


The Set of Non-Negative Rational Numbers

$\Q_{\ge 0}$

The set of non-negative rational numbers:

$\Q_{\ge 0} = \left\{{x \in \Q: x \ge 0}\right\}$


The $\LaTeX$ code for \(\Q_{\ge 0}\) is \Q_{\ge 0}  or \mathbb Q_{\ge 0} or \Bbb Q_{\ge 0}.


Deprecated

$\Q_+$

The set of non-negative rational numbers:

$\Q_+ = \left\{{x \in \Q: x \ge 0}\right\}$


The $\LaTeX$ code for \(\Q_+\) is \Q_+  or \mathbb Q_+ or \Bbb Q_+.


The Set of Strictly Positive Rational Numbers

$\Q_{> 0}$

The set of strictly positive rational numbers:

$\Q_{> 0} = \left\{{x \in \Q: x > 0}\right\}$


The $\LaTeX$ code for \(\Q_{> 0}\) is \Q_{> 0}  or \mathbb Q_{> 0} or \Bbb Q_{> 0}.


Deprecated

$\Q_+^*$

The set of strictly positive rational numbers:

$\Q_+^* = \left\{{x \in \Q: x > 0}\right\}$


The $\LaTeX$ code for \(\Q_+^*\) is \Q_+^*  or \mathbb Q_+^*} or \Bbb Q_+^*.


Probability

$q$

Used in conjunction with the general probability $p$:

$q = 1 - p$

As such, $q$ is a real number such that:

$0 \le q \le 1$

and

$p + q = 1$


The $\LaTeX$ code for \(q\) is q .


Quotient Mapping

$q_\mathcal R$

The quotient mapping induced by $\mathcal R$:

$q_\mathcal R: S \to S / \mathcal R: q_\mathcal R \left({s}\right) = \left[\!\left[{s}\right]\!\right]_\mathcal R$

where:

$\mathcal R \subseteq S \times S$ be an equivalence relation on a set $S$
$\left[\!\left[{s}\right]\!\right]_\mathcal R$ is the $\mathcal R$-equivalence class of $s$
$S / \mathcal R$ is the quotient set of $S$ determined by $\mathcal R$.


Also known as:

the canonical surjection from $S$ to $S / \mathcal R$
the canonical map or canonical projection from $S$ onto $S / \mathcal R$
the natural mapping from $S$ to $S / \mathcal R$
the natural surjection from $S$ to $S / \mathcal R$
the classifying map or classifying mapping (as it classifies the elements of $S$ into those various equivalence classes)
the projection from $S$ to $S / \mathcal R$


The $\LaTeX$ code for \(q_\mathcal R: S \to S / \mathcal R\) is q_\mathcal R: S \to S / \mathcal R .