Dynamic system $f(x) = 2x$ mod $1$












4














I am reading the following paper:



ergodic theory of chaos and strange attractors, by J.-P. Eckmann (can be easily downloaded)



My question is from an example on p.620 (bottom left):



Consider a dynamical system $$f(x) = 2x text{mod } 1$$
for $xin [0,1)$.





  1. The paper says this dynamical system is "left-shift with leading digit truncation" in binary notation. What is this?


  2. "Repeated measurements in time will yield eventually all binary digits of the initial point." what does this mean?












share|cite|improve this question





























    4














    I am reading the following paper:



    ergodic theory of chaos and strange attractors, by J.-P. Eckmann (can be easily downloaded)



    My question is from an example on p.620 (bottom left):



    Consider a dynamical system $$f(x) = 2x text{mod } 1$$
    for $xin [0,1)$.





    1. The paper says this dynamical system is "left-shift with leading digit truncation" in binary notation. What is this?


    2. "Repeated measurements in time will yield eventually all binary digits of the initial point." what does this mean?












    share|cite|improve this question



























      4












      4








      4


      1





      I am reading the following paper:



      ergodic theory of chaos and strange attractors, by J.-P. Eckmann (can be easily downloaded)



      My question is from an example on p.620 (bottom left):



      Consider a dynamical system $$f(x) = 2x text{mod } 1$$
      for $xin [0,1)$.





      1. The paper says this dynamical system is "left-shift with leading digit truncation" in binary notation. What is this?


      2. "Repeated measurements in time will yield eventually all binary digits of the initial point." what does this mean?












      share|cite|improve this question















      I am reading the following paper:



      ergodic theory of chaos and strange attractors, by J.-P. Eckmann (can be easily downloaded)



      My question is from an example on p.620 (bottom left):



      Consider a dynamical system $$f(x) = 2x text{mod } 1$$
      for $xin [0,1)$.





      1. The paper says this dynamical system is "left-shift with leading digit truncation" in binary notation. What is this?


      2. "Repeated measurements in time will yield eventually all binary digits of the initial point." what does this mean?









      dynamical-systems binary ergodic-theory chaos-theory






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      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Dec 6 '18 at 22:07









      Adam

      1,1951919




      1,1951919










      asked Nov 23 '18 at 8:31









      sleeve chensleeve chen

      3,06641852




      3,06641852






















          2 Answers
          2






          active

          oldest

          votes


















          6














          I think it means:





          1. The binary representation of the number $fleft(xright)$ is the same as the binary representation of $x$ shifted one place to the left and with the leading digit cut off. For example, in binary notation, we have $frac{3}{4} = 0.11$, and $fleft(frac{3}{4}right) = frac{1}{2} = 0.1$.

          2. Reading the example as in the paper, you didn't mention that "measurement" here really means measurement of whether a number is greater or less than $frac{1}{2}$. By repeatedly applying $fleft(xright)$ and measuring the outcome each time, we can ascertain for each binary digit of $x$ whether it is $0$ or $1$, hence we can determine all binary digits of $x$ in this way.







          share|cite|improve this answer





























            3














            Let $x=0,b_1ldots b_n$, with $b_iin{0,1}$, be the representation of $x$ in base $2$.
            Then $2x=b_1,b_2ldots b_n$ hence $f(x)=0,b_2ldots b_n$, that's $f(x)$ is obtained from $x$ by remove left-handed binary digit as asserted in 1.
            Consequently, the orbit of $x$ is:
            begin{array}
            x & 0,b_1ldots b_n\
            f(x) & 0,b_2ldots b_n\
            f^{circ 2}(x) & 0,b_3ldots b_n\
            end{array}

            Consequently, the first digit of the sequence $x, f(x), f^{circ 2}(x), ldots$ gives the sequence of binary digits of $x$ (statement 2).






            share|cite|improve this answer





















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              2 Answers
              2






              active

              oldest

              votes








              2 Answers
              2






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              6














              I think it means:





              1. The binary representation of the number $fleft(xright)$ is the same as the binary representation of $x$ shifted one place to the left and with the leading digit cut off. For example, in binary notation, we have $frac{3}{4} = 0.11$, and $fleft(frac{3}{4}right) = frac{1}{2} = 0.1$.

              2. Reading the example as in the paper, you didn't mention that "measurement" here really means measurement of whether a number is greater or less than $frac{1}{2}$. By repeatedly applying $fleft(xright)$ and measuring the outcome each time, we can ascertain for each binary digit of $x$ whether it is $0$ or $1$, hence we can determine all binary digits of $x$ in this way.







              share|cite|improve this answer


























                6














                I think it means:





                1. The binary representation of the number $fleft(xright)$ is the same as the binary representation of $x$ shifted one place to the left and with the leading digit cut off. For example, in binary notation, we have $frac{3}{4} = 0.11$, and $fleft(frac{3}{4}right) = frac{1}{2} = 0.1$.

                2. Reading the example as in the paper, you didn't mention that "measurement" here really means measurement of whether a number is greater or less than $frac{1}{2}$. By repeatedly applying $fleft(xright)$ and measuring the outcome each time, we can ascertain for each binary digit of $x$ whether it is $0$ or $1$, hence we can determine all binary digits of $x$ in this way.







                share|cite|improve this answer
























                  6












                  6








                  6






                  I think it means:





                  1. The binary representation of the number $fleft(xright)$ is the same as the binary representation of $x$ shifted one place to the left and with the leading digit cut off. For example, in binary notation, we have $frac{3}{4} = 0.11$, and $fleft(frac{3}{4}right) = frac{1}{2} = 0.1$.

                  2. Reading the example as in the paper, you didn't mention that "measurement" here really means measurement of whether a number is greater or less than $frac{1}{2}$. By repeatedly applying $fleft(xright)$ and measuring the outcome each time, we can ascertain for each binary digit of $x$ whether it is $0$ or $1$, hence we can determine all binary digits of $x$ in this way.







                  share|cite|improve this answer












                  I think it means:





                  1. The binary representation of the number $fleft(xright)$ is the same as the binary representation of $x$ shifted one place to the left and with the leading digit cut off. For example, in binary notation, we have $frac{3}{4} = 0.11$, and $fleft(frac{3}{4}right) = frac{1}{2} = 0.1$.

                  2. Reading the example as in the paper, you didn't mention that "measurement" here really means measurement of whether a number is greater or less than $frac{1}{2}$. By repeatedly applying $fleft(xright)$ and measuring the outcome each time, we can ascertain for each binary digit of $x$ whether it is $0$ or $1$, hence we can determine all binary digits of $x$ in this way.








                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Nov 23 '18 at 9:06









                  Sam StreeterSam Streeter

                  1,485417




                  1,485417























                      3














                      Let $x=0,b_1ldots b_n$, with $b_iin{0,1}$, be the representation of $x$ in base $2$.
                      Then $2x=b_1,b_2ldots b_n$ hence $f(x)=0,b_2ldots b_n$, that's $f(x)$ is obtained from $x$ by remove left-handed binary digit as asserted in 1.
                      Consequently, the orbit of $x$ is:
                      begin{array}
                      x & 0,b_1ldots b_n\
                      f(x) & 0,b_2ldots b_n\
                      f^{circ 2}(x) & 0,b_3ldots b_n\
                      end{array}

                      Consequently, the first digit of the sequence $x, f(x), f^{circ 2}(x), ldots$ gives the sequence of binary digits of $x$ (statement 2).






                      share|cite|improve this answer


























                        3














                        Let $x=0,b_1ldots b_n$, with $b_iin{0,1}$, be the representation of $x$ in base $2$.
                        Then $2x=b_1,b_2ldots b_n$ hence $f(x)=0,b_2ldots b_n$, that's $f(x)$ is obtained from $x$ by remove left-handed binary digit as asserted in 1.
                        Consequently, the orbit of $x$ is:
                        begin{array}
                        x & 0,b_1ldots b_n\
                        f(x) & 0,b_2ldots b_n\
                        f^{circ 2}(x) & 0,b_3ldots b_n\
                        end{array}

                        Consequently, the first digit of the sequence $x, f(x), f^{circ 2}(x), ldots$ gives the sequence of binary digits of $x$ (statement 2).






                        share|cite|improve this answer
























                          3












                          3








                          3






                          Let $x=0,b_1ldots b_n$, with $b_iin{0,1}$, be the representation of $x$ in base $2$.
                          Then $2x=b_1,b_2ldots b_n$ hence $f(x)=0,b_2ldots b_n$, that's $f(x)$ is obtained from $x$ by remove left-handed binary digit as asserted in 1.
                          Consequently, the orbit of $x$ is:
                          begin{array}
                          x & 0,b_1ldots b_n\
                          f(x) & 0,b_2ldots b_n\
                          f^{circ 2}(x) & 0,b_3ldots b_n\
                          end{array}

                          Consequently, the first digit of the sequence $x, f(x), f^{circ 2}(x), ldots$ gives the sequence of binary digits of $x$ (statement 2).






                          share|cite|improve this answer












                          Let $x=0,b_1ldots b_n$, with $b_iin{0,1}$, be the representation of $x$ in base $2$.
                          Then $2x=b_1,b_2ldots b_n$ hence $f(x)=0,b_2ldots b_n$, that's $f(x)$ is obtained from $x$ by remove left-handed binary digit as asserted in 1.
                          Consequently, the orbit of $x$ is:
                          begin{array}
                          x & 0,b_1ldots b_n\
                          f(x) & 0,b_2ldots b_n\
                          f^{circ 2}(x) & 0,b_3ldots b_n\
                          end{array}

                          Consequently, the first digit of the sequence $x, f(x), f^{circ 2}(x), ldots$ gives the sequence of binary digits of $x$ (statement 2).







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Nov 23 '18 at 9:06









                          Fabio LucchiniFabio Lucchini

                          7,81311426




                          7,81311426






























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