Can ratio of smooth numbers approach 1?











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Can the ratio of $q$-smooth numbers ever approach one? Asked more rigorously, can we ever have
$$1in overline{{a/b; :; a,b ;text{ are } qtext{-smooth}}}=overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}};?$$
If $q=2$, the answer is obviously no because
$$1notin overline{{2^{alpha}; :; alphainmathbb{Z}}}={0}cup {2^{alpha}; :; alphainmathbb{Z}}$$
however beyond this the problem is not easy. The reason I would like to know this is because this would imply that
$$G(q)=inf {a/b; :; a>b,; a,b ; qtext{-smooth}}>1.$$
I suspect that we may be able to say even further that
$$overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}}={0}cup {prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}$$
which would clearly imply the result.










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  • Quite amusingly, this is on the sitewide hot questions list.
    – Matt Samuel
    Nov 3 at 22:40










  • @MattSamuel: Probably because people like to hear "smooth" talk? =P
    – user21820
    Nov 4 at 3:02















up vote
4
down vote

favorite












Can the ratio of $q$-smooth numbers ever approach one? Asked more rigorously, can we ever have
$$1in overline{{a/b; :; a,b ;text{ are } qtext{-smooth}}}=overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}};?$$
If $q=2$, the answer is obviously no because
$$1notin overline{{2^{alpha}; :; alphainmathbb{Z}}}={0}cup {2^{alpha}; :; alphainmathbb{Z}}$$
however beyond this the problem is not easy. The reason I would like to know this is because this would imply that
$$G(q)=inf {a/b; :; a>b,; a,b ; qtext{-smooth}}>1.$$
I suspect that we may be able to say even further that
$$overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}}={0}cup {prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}$$
which would clearly imply the result.










share|cite|improve this question






















  • Quite amusingly, this is on the sitewide hot questions list.
    – Matt Samuel
    Nov 3 at 22:40










  • @MattSamuel: Probably because people like to hear "smooth" talk? =P
    – user21820
    Nov 4 at 3:02













up vote
4
down vote

favorite









up vote
4
down vote

favorite











Can the ratio of $q$-smooth numbers ever approach one? Asked more rigorously, can we ever have
$$1in overline{{a/b; :; a,b ;text{ are } qtext{-smooth}}}=overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}};?$$
If $q=2$, the answer is obviously no because
$$1notin overline{{2^{alpha}; :; alphainmathbb{Z}}}={0}cup {2^{alpha}; :; alphainmathbb{Z}}$$
however beyond this the problem is not easy. The reason I would like to know this is because this would imply that
$$G(q)=inf {a/b; :; a>b,; a,b ; qtext{-smooth}}>1.$$
I suspect that we may be able to say even further that
$$overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}}={0}cup {prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}$$
which would clearly imply the result.










share|cite|improve this question













Can the ratio of $q$-smooth numbers ever approach one? Asked more rigorously, can we ever have
$$1in overline{{a/b; :; a,b ;text{ are } qtext{-smooth}}}=overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}};?$$
If $q=2$, the answer is obviously no because
$$1notin overline{{2^{alpha}; :; alphainmathbb{Z}}}={0}cup {2^{alpha}; :; alphainmathbb{Z}}$$
however beyond this the problem is not easy. The reason I would like to know this is because this would imply that
$$G(q)=inf {a/b; :; a>b,; a,b ; qtext{-smooth}}>1.$$
I suspect that we may be able to say even further that
$$overline{{prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}}={0}cup {prod_{p_ile q}p_i^{alpha_i}; :; (a_1, dots, a_{pi(q)})inmathbb{Z}^{pi(q)}}$$
which would clearly imply the result.







number-theory limits elementary-number-theory






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asked Nov 3 at 21:19









Will Fisher

3,487629




3,487629












  • Quite amusingly, this is on the sitewide hot questions list.
    – Matt Samuel
    Nov 3 at 22:40










  • @MattSamuel: Probably because people like to hear "smooth" talk? =P
    – user21820
    Nov 4 at 3:02


















  • Quite amusingly, this is on the sitewide hot questions list.
    – Matt Samuel
    Nov 3 at 22:40










  • @MattSamuel: Probably because people like to hear "smooth" talk? =P
    – user21820
    Nov 4 at 3:02
















Quite amusingly, this is on the sitewide hot questions list.
– Matt Samuel
Nov 3 at 22:40




Quite amusingly, this is on the sitewide hot questions list.
– Matt Samuel
Nov 3 at 22:40












@MattSamuel: Probably because people like to hear "smooth" talk? =P
– user21820
Nov 4 at 3:02




@MattSamuel: Probably because people like to hear "smooth" talk? =P
– user21820
Nov 4 at 3:02










2 Answers
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Yes, if $qge 3$.



This is because $log_2(3)$ is irrational, so the fractional parts of $log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.






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    Yes. We can just consider fractions of the form $frac {3^a}{2^b}$. The base $2$ log of this is $alog_2(3)-b$. Because $log_2(3)$ is irrational, we can choose $a,b$ to make this difference arbitrarily close to $0$, which means the ratio can be arbitrarily close to $1$.






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      2 Answers
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      2 Answers
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      active

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      up vote
      6
      down vote



      accepted










      Yes, if $qge 3$.



      This is because $log_2(3)$ is irrational, so the fractional parts of $log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.






      share|cite|improve this answer



























        up vote
        6
        down vote



        accepted










        Yes, if $qge 3$.



        This is because $log_2(3)$ is irrational, so the fractional parts of $log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.






        share|cite|improve this answer

























          up vote
          6
          down vote



          accepted







          up vote
          6
          down vote



          accepted






          Yes, if $qge 3$.



          This is because $log_2(3)$ is irrational, so the fractional parts of $log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.






          share|cite|improve this answer














          Yes, if $qge 3$.



          This is because $log_2(3)$ is irrational, so the fractional parts of $log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.







          share|cite|improve this answer














          share|cite|improve this answer



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          edited Nov 3 at 21:44

























          answered Nov 3 at 21:26









          Henning Makholm

          234k16299532




          234k16299532






















              up vote
              6
              down vote













              Yes. We can just consider fractions of the form $frac {3^a}{2^b}$. The base $2$ log of this is $alog_2(3)-b$. Because $log_2(3)$ is irrational, we can choose $a,b$ to make this difference arbitrarily close to $0$, which means the ratio can be arbitrarily close to $1$.






              share|cite|improve this answer

























                up vote
                6
                down vote













                Yes. We can just consider fractions of the form $frac {3^a}{2^b}$. The base $2$ log of this is $alog_2(3)-b$. Because $log_2(3)$ is irrational, we can choose $a,b$ to make this difference arbitrarily close to $0$, which means the ratio can be arbitrarily close to $1$.






                share|cite|improve this answer























                  up vote
                  6
                  down vote










                  up vote
                  6
                  down vote









                  Yes. We can just consider fractions of the form $frac {3^a}{2^b}$. The base $2$ log of this is $alog_2(3)-b$. Because $log_2(3)$ is irrational, we can choose $a,b$ to make this difference arbitrarily close to $0$, which means the ratio can be arbitrarily close to $1$.






                  share|cite|improve this answer












                  Yes. We can just consider fractions of the form $frac {3^a}{2^b}$. The base $2$ log of this is $alog_2(3)-b$. Because $log_2(3)$ is irrational, we can choose $a,b$ to make this difference arbitrarily close to $0$, which means the ratio can be arbitrarily close to $1$.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Nov 3 at 21:27









                  Ross Millikan

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