2 Asymptotic growth
\(f\) is asymptotically bounded above by \(g\) if there exists a \(k {\gt} 0\) such that \(f\) is asymptotically less than \(k*g\).
\(f\) is asymptotically bounded below by \(g\) if there exists \(k {\gt} 0\) such that \(f\) is asymptotically greater than \(k*g\).
\(f\) is asymptotically bounded by \(g\) if \(f\) is asymptotically bounded above and below by \(g\).
\(f\) is asymptotically dominated by \(g\) if for all \(k {\gt} 0\) \(f\) is asymptotically less than \(k*g\).
\(f\) asymptotically dominates \(g\) if for all \(k {\gt} 0\) \((x)\) is asymptotically greater than \(k*g\).
If \(f\) is dominated by \(g\), then it’s also bounded above by \(g\).
The definitions of \(f\) being dominated and bounded above by \(g\) only differ in the quantifier before \(k\) at the very start (universal for the hypothesis, existential for the goal), so it suffices to use any positive value for \(k\). We can use \(1\). The desired result then follows directly.
If \(f\) dominates \(g\), then it’s bounded below by \(g\).
The proof is entirely analogous to the previous proof.
\(f\) is asymptotically bounded above and below by \(g\) if and only if \(f\) is asymptotically bounded by \(g\).
Both directions follow directly from the definition of asymptotic boundedness.
Let \(g\) be asymptotically positive. Then \(f\) is not both asymptotically bounded below by \(g\) and asymptotically dominated by \(g\).
Suppose \(f\) is asymptotically bounded below by \(g\) and also asymptotically dominated by \(g\). We need to find a contradiction to prove the statement.
First, we claim that there exists \(x\_ 0\) such that for all \(x \ge x\_ 0\) we have \(f(x) \ge k \cdot g(x)\) for some \(k {\gt} 0\), \(g(x) \ge 0\) and \(f(x) \le k' \cdot g(x)\) for all \(k' {\gt} 0\). Each of the asymptotic assumption gives one such constant, so taking the maximum of all three gives the needed value.
For the contradiction, consider \(f(x) \le k' \cdot g(x)\) when \(k' = k / 2\). In this case, we have \(f(x) \le (k / 2) \cdot g(x)\), but we also have \(k \cdot g(x) \le f(x)\), leading by transitivity to \(k \cdot g(x) \le (k / 2) \cdot g(x)\), an obvious contradiction to the fact that \((k / 2) \cdot g(x) \le k \cdot g(x)\).
Let \(f\) be asymptotically positive. If \(f\) is asymptotically bounded below by \(g\), then \(f\) is not asymptotically dominated by \(g\).
This is a direct application of Lemma 38.
Let \(f\) be asymptotically positive. If \(f\) is asymptotically bounded below by \(g\), then \(f\) is not asymptotically dominated by \(g\).
This is a direct application of Lemma 38.
Let \(g\) be asymptotically positive. Then it does not hold that both \(f\) is asymptotically bounded above by \(g\) and \(f\) asymptotically dominate \(g\).
The proof is analogous to the proof of Lemma 38. This time, we set \(k' = k + 1\) and thus produce the false inequality \((k + 1) \cdot g(x) \le k \cdot g(x)\).
Let \(f\) be asymptotically positive. If \(f\) is bounded below by \(g\), then \(f\) does not dominate \(g\).
This is a direct application of Lemma 41.
Let \(f\) be asymptotically positive. If \(f\) is asymptotically bounded above by \(g\), then \(f\) does not asymptotically dominate \(g\).
This is a direct application of Lemma 41.
Let \(g\) be asymptotically positive. Then it is not true that both \(f\) is asymptotically dominated by \(g\) and that \(f\) dominates \(g\).
Suppose \(f\) both dominates \(g\) and is dominated by \(g\). Our goal is to find a contradiction. We have by definition the inequalities \(g(x) {\gt} 0\), \(f(x) \ge k\_ 1 \cdot g(x)\) and \(f(x) \le k\_ 2 \cdot g(x)\) for all \(k\_ 1 {\gt} 0\), \(k\_ 2 {\gt} 0\) and for all \(x \ge x\_ 0\) for some \(x\_ 0\). Note that we use the same constant \(x\_ 0\) for all inequalities with no loss of generality. In fact, we shall also use the same \(x\_ 0\) in the asymptotic positivity condition \(g(x) {\gt} 0\).
Fix \(k\_ 1 = 2\) and \(k\_ 2 = 1\) (generally, we only need \(k\_ 1 \ge k\_ 2\)), so we now have \(f(x) \ge 2 \cdot g(x)\) and \(f(x) \le g(x)\). From these inequalities, it immediately follows that \(2 \cdot g(x) \le g(x)\). However, since \(1 \le 2\) and \(g(x) {\gt} 0\), we have \(g(x) {\lt} 2 \cdot g(x)\). We thus have two contradicting inequalities, finishing the proof.
Let \(g\) be asymptotically positive. If \(f\) is asymptotically dominated by \(g\), then \(f\) does not asymptotically dominate \(g\).
This is a direct application of Lemma 44.
Let \(g\) be asymptotically positive. If \(f\) asymptotically dominates \(g\), then \(f\) is not asymptotically dominated by \(g\).
This is a direct application of Lemma 44.
2.1 Reflexivity
\(f\) is asymptotically bounded by itself.
Proving asymptotic boundedness is equivalent to proving boundedness above and below. Both can be proved the same way - we choose \(1_K\) for \(K\) and \(1_R\) for \(N\), then the required asymptotic growth properties follow from definitions of identity elements for \(K\) and \(R\).
\(f\) is asymptotically bounded above by itself.
This follows directly from 47.
\(f\) is asymptotically bounded below by itself.
This follows directly from 47.
2.2 Transitivity
If \(f\) is asymptotically bounded above by \(g\) and \(g\) is asymptotically bounded above by \(h\), then \(f\) is asymptotically bounded above by \(h\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f(x) \le k\_ 1 \cdot g(x)\) and \(g(x) \le k\_ 2 \cdot h(x)\) for sufficiently large \(x\). By multiplicativity and transitivity, we have \(f(x) \le k\_ 1 \cdot k\_ 2 \cdot h(x)\).
If \(f\) is asymptotically bounded below by \(g\) and \(g\) is asymptotically bounded below by \(h\), then \(f\) is asymptotically bounded below by \(h\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f(x) \ge k\_ 1 \cdot g(x)\) and \(g(x) \ge k\_ 2 \cdot h(x)\) for sufficiently large \(x\). By multiplicativity and transitivity, we have \(f(x) \ge k\_ 1 \cdot k\_ 2 \cdot h(x)\).
If \(f\) is asymptotically bounded by \(g\) and \(g\) is asymptotically bounded by \(h\), then \(f\) is asymptotically bounded by \(h\).
If \(f\) is asymptotically dominated by \(g\) and \(g\) is asymptotically dominated by \(h\), then \(f\) is asymptotically dominated by \(h\).
Let \(k {\gt} 0\). Then by first assumption, we have \(f(x) \le k \cdot g(x)\) for large \(x\). By the second assumption, we have \(g(x) \le h(x)\) for large \(x\). By multiplicativity and transitivity, we get \(f(x) \le k \cdot h(x)\).
If \(f\) asymptotically dominates \(g\) and \(g\) asymptotically dominates \(h\), then \(f\) asymptotically dominates \(h\).
Let \(k {\gt} 0\). Then by first assumption, we have \(f(x) \ge k \cdot g(x)\) for large \(x\). By the second assumption, we have \(g(x) \ge h(x)\) for large \(x\). By multiplicativity and transitivity, we get \(f(x) \ge k \cdot h(x)\).
2.3 Scalar multiplicativity
Let \(c {\gt} 0\). If \(f\) is bounded above by \(g\), then \(c \cdot f\) is also bounded above by \(g\).
Let \(k\) be the constant such that \(f\) is asymptotically less than \(k \cdot g\). By positive scalar multiplicativity of asymptotic inequality, \(c \cdot f\) is asymptotically less than \(c \cdot k \cdot g\). Since \(c \cdot k {\gt} 0\), this implies that \(c \cdot f\) is bounded above by \(g\).
Let \(c {\gt} 0\). If \(f\) is bounded below by \(g\), then \(c \cdot f\) is also bounded below by \(g\).
Let \(k\) be the constant such that \(f\) is asymptotically greater than \(k \cdot g\). By positive scalar multiplicativity of asymptotic inequality, \(c \cdot f\) is asymptotically greater than \(c \cdot k \cdot g\). Since \(c \cdot k {\gt} 0\), this implies that \(c \cdot f\) is bounded below by \(g\).
Let \(c {\gt} 0\). If \(f\) is bounded by \(g\), then \(c \cdot f\) is also bounded by \(g\).
Let \(c {\lt} 0\). If \(f\) is bounded above by \(g\), then \(c \cdot f\) is bounded above by \(-g\).
Let \(k\) be the constant such that \(f\) is asymptotically less than \(k \cdot g\). By positive scalar multiplicativity of asymptotic inequality, \(-c \cdot f\) is asymptotically less than \(-c \cdot k \cdot g\). Since \(-c \cdot k {\gt} 0\), this implies that \(c \cdot f\) is bounded above by \(-g\).
Let \(c {\lt} 0\). If \(f\) is bounded below by \(g\), then \(c \cdot f\) is bounded below by \(-g\).
Let \(k\) be the constant such that \(f\) is asymptotically greater than \(k \cdot g\). By positive scalar multiplicativity of asymptotic inequality, \(-c \cdot f\) is asymptotically greater than \(-c \cdot k \cdot g\). Since \(-c \cdot k {\gt} 0\), this implies that \(c \cdot f\) is bounded below by \(-g\).
Let \(c {\lt} 0\). If \(f\) is bounded by \(g\), then \(c \cdot f\) is bounded by \(-g\).
2.4 Additivity
Let \(f\_ 1\) and \(f\_ 2\) be bounded above by \(g\). Then \(f\_ 1 + f\_ 2\) is also bounded above by \(g\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f\_ 1\) is asymptotically less than \(k\_ 1 \cdot g\) and \(f\_ 2\) is asymptotically less than \(k\_ 2 \cdot g\). By additivity of asymptotic inequality, \(f\_ 1 + f\_ 2\) is asymptotically less than \((k\_ 1 * k\_ 2) \cdot g\). It directly follows that \(f\_ 1 + f\_ 2\) is asymptotically bounded above by \(g\).
Let \(f\_ 1\) and \(f\_ 2\) be bounded below by \(g\). Then \(f\_ 1 + f\_ 2\) is also bounded below by \(g\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f\_ 1\) is asymptotically greater than \(k\_ 1 \cdot g\) and \(f\_ 2\) is asymptotically greater than \(k\_ 2 \cdot g\). By additivity of asymptotic inequality, \(f\_ 1 + f\_ 2\) is asymptotically greater than \((k\_ 1 * k\_ 2) \cdot g\). It directly follows that \(f\_ 1 + f\_ 2\) is asymptotically bounded below by \(g\).
Let \(f\_ 1\) and \(f\_ 2\) be bounded by \(g\). Then \(f\_ 1 + f\_ 2\) is also bounded by \(g\).
Let \(f\_ 1\) be bounded below by \(g\) and let \(f\_ 2\) be asymptotically positive. Then \(f\_ 1 + f\_ 2\) is bounded below by \(g\).
This property immediately follows from Lemma 22.
Let \(f\_ 1\) be bounded above by \(g\) and let \(f\_ 2\) be asymptotically negative. Then \(f\_ 1 + f\_ 2\) is bounded above by \(g\).
This property immediately follows from Lemma 23.
Let \(f\_ 1\) be bounded by \(g\). Let also \(f\_ 2\) be asymptotically positive and bounded above by \(g\). Then \(f\_ 1 + f\_ 2\) is bounded by \(g\).
Let \(f\_ 1\) be bounded by \(g\). Let also \(f\_ 2\) be asymptotically negative and bounded below by \(g\). Then \(f\_ 1 + f\_ 2\) is bounded by \(g\).
Let \(f\_ 1\) be bounded by \(g\). Let also \(f\_ 2\) be asymptotically positive and let \(f\_ 2\) be dominated by \(g\). Then \(f\_ 1 + f\_ 2\) is bounded by \(g\).
Let \(f\_ 1\) be bounded by \(g\). Let also \(f\_ 2\) be asymptotically negative and let \(f\_ 2\) dominate \(g\). Then \(f\_ 1 + f\_ 2\) is bounded by \(g\).
2.5 Multiplicativity
Let \(f\_ 1\) and \(f\_ 2\) be asymptotically nonnegative functions such that \(f\_ 1\) is asymptotically bounded above by \(g\_ 1\) and \(f\_ 2\) is asymptotically bounded above by \(g\_ 2\). Then \(f\_ 1 * f\_ 2\) is asymptotically bounded above by \(g\_ 1 * g\_ 2\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f\_ 1\) is asymptotically less than \(g\_ 1\) and \(f\_ 2\) is asymptotically less than \(g\_ 2\). By multiplicativity of asymptotic inequality, \(f\_ 1 * f\_ 2\) is asymptotically less than \(k\_ 1 \cdot g\_ 1 * k\_ 2 \cdot g\_ 2\), which is equivalent to asymptotic above boundedness of \(f\_ 1 * f\_ 2\) by \(g\_ 1 * g\_ 2\).
Let \(f\_ 1\) and \(f\_ 2\) be asymptotically nonpositive functions such that \(f\_ 1\) is asymptotically bounded below by \(g\_ 1\) and \(f\_ 2\) is asymptotically bounded below by \(g\_ 2\). Then \(f\_ 1 * f\_ 2\) is asymptotically bounded below by \(g\_ 1 * g\_ 2\).
Let \(k\_ 1\) and \(k\_ 2\) be the constants such that \(f\_ 1\) is asymptotically greaterthan \(g\_ 1\) and \(f\_ 2\) is asymptotically greater than \(g\_ 2\). By multiplicativity of asymptotic inequality, \(f\_ 1 * f\_ 2\) is asymptotically less than \(k\_ 1 \cdot g\_ 1 * k\_ 2 \cdot g\_ 2\), which is equivalent to asymptotic below boundedness of \(f\_ 1 * f\_ 2\) by \(g\_ 1 * g\_ 2\).