Proof for minimum number of states for a epsilon free NFA is $2^n$












2














I have the following question which I could not proceed:



Let
$$L={w in Sigma^* mid text{all symbols of the alphabet occur even times in } w}.
$$



Prove that any NFA accepting $L$ requires $2^n$ states, where $n$ is the size of the alphabet $Sigma$.



I think I came up with a proof for a DFA using the Myhill-Nerode Theorem but I do not know how to generalize it to NFA's.



Edit:Relevant question is answered in https://stackoverflow.com/questions/9068873/how-do-we-know-that-an-nfa-has-a-minimum-amount-of-states .










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    2














    I have the following question which I could not proceed:



    Let
    $$L={w in Sigma^* mid text{all symbols of the alphabet occur even times in } w}.
    $$



    Prove that any NFA accepting $L$ requires $2^n$ states, where $n$ is the size of the alphabet $Sigma$.



    I think I came up with a proof for a DFA using the Myhill-Nerode Theorem but I do not know how to generalize it to NFA's.



    Edit:Relevant question is answered in https://stackoverflow.com/questions/9068873/how-do-we-know-that-an-nfa-has-a-minimum-amount-of-states .










    share|cite|improve this question



























      2












      2








      2


      0





      I have the following question which I could not proceed:



      Let
      $$L={w in Sigma^* mid text{all symbols of the alphabet occur even times in } w}.
      $$



      Prove that any NFA accepting $L$ requires $2^n$ states, where $n$ is the size of the alphabet $Sigma$.



      I think I came up with a proof for a DFA using the Myhill-Nerode Theorem but I do not know how to generalize it to NFA's.



      Edit:Relevant question is answered in https://stackoverflow.com/questions/9068873/how-do-we-know-that-an-nfa-has-a-minimum-amount-of-states .










      share|cite|improve this question















      I have the following question which I could not proceed:



      Let
      $$L={w in Sigma^* mid text{all symbols of the alphabet occur even times in } w}.
      $$



      Prove that any NFA accepting $L$ requires $2^n$ states, where $n$ is the size of the alphabet $Sigma$.



      I think I came up with a proof for a DFA using the Myhill-Nerode Theorem but I do not know how to generalize it to NFA's.



      Edit:Relevant question is answered in https://stackoverflow.com/questions/9068873/how-do-we-know-that-an-nfa-has-a-minimum-amount-of-states .







      proof-explanation automata






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      edited Nov 29 '18 at 6:20

























      asked Nov 28 '18 at 2:15









      Arda Akdemir

      134




      134






















          1 Answer
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          0














          The answer to the relevant question refers to
          a theorem of [1] that can be used to determine lower bounds on the number of states of a minimal NFA:




          Theorem. Let $L subseteq Sigma^*$ be a regular language and suppose that there exist $n$ pairs of words $P = {(u_i, v_i) mid 1 leqslant i leqslant n }$ such that:





          1. $u_iv_i in L$ for $1 leqslant i leqslant n$


          2. $u_jv_i notin L$ for $1 leqslant i,j leqslant n$ and $i not= j$.


          Then any NFA accepting $L$ has at least $n$ states.




          Suppose that $Sigma = {a_1, dots, a_n}$. For each $i = (i_1, dots, i_n) in {0, 1}^n$, let $u_i = v_i = a_{i_1}^{i_1} a_{i_2}^{i_2} dotsm a_{i_n}^{i_n}$. By construction, $u_i$ and $v_i$ satisfy the conditions (1) and (2). Since $|{0, 1}^n| = 2^n$, any NFA accepting $L$ has at least $2^n$ states.



          [1] I. Glaister and J. Shallit, A lower bound technique for the size of nondeterministic finite automata. Information Processing Letters 59 (2), pp. 75–77, (1996). DOI:10.1016/0020-0190(96)00095-6.






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          • Thank you for the answer!
            – Arda Akdemir
            Nov 29 '18 at 6:20











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          1 Answer
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          active

          oldest

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          active

          oldest

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          active

          oldest

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          0














          The answer to the relevant question refers to
          a theorem of [1] that can be used to determine lower bounds on the number of states of a minimal NFA:




          Theorem. Let $L subseteq Sigma^*$ be a regular language and suppose that there exist $n$ pairs of words $P = {(u_i, v_i) mid 1 leqslant i leqslant n }$ such that:





          1. $u_iv_i in L$ for $1 leqslant i leqslant n$


          2. $u_jv_i notin L$ for $1 leqslant i,j leqslant n$ and $i not= j$.


          Then any NFA accepting $L$ has at least $n$ states.




          Suppose that $Sigma = {a_1, dots, a_n}$. For each $i = (i_1, dots, i_n) in {0, 1}^n$, let $u_i = v_i = a_{i_1}^{i_1} a_{i_2}^{i_2} dotsm a_{i_n}^{i_n}$. By construction, $u_i$ and $v_i$ satisfy the conditions (1) and (2). Since $|{0, 1}^n| = 2^n$, any NFA accepting $L$ has at least $2^n$ states.



          [1] I. Glaister and J. Shallit, A lower bound technique for the size of nondeterministic finite automata. Information Processing Letters 59 (2), pp. 75–77, (1996). DOI:10.1016/0020-0190(96)00095-6.






          share|cite|improve this answer





















          • Thank you for the answer!
            – Arda Akdemir
            Nov 29 '18 at 6:20
















          0














          The answer to the relevant question refers to
          a theorem of [1] that can be used to determine lower bounds on the number of states of a minimal NFA:




          Theorem. Let $L subseteq Sigma^*$ be a regular language and suppose that there exist $n$ pairs of words $P = {(u_i, v_i) mid 1 leqslant i leqslant n }$ such that:





          1. $u_iv_i in L$ for $1 leqslant i leqslant n$


          2. $u_jv_i notin L$ for $1 leqslant i,j leqslant n$ and $i not= j$.


          Then any NFA accepting $L$ has at least $n$ states.




          Suppose that $Sigma = {a_1, dots, a_n}$. For each $i = (i_1, dots, i_n) in {0, 1}^n$, let $u_i = v_i = a_{i_1}^{i_1} a_{i_2}^{i_2} dotsm a_{i_n}^{i_n}$. By construction, $u_i$ and $v_i$ satisfy the conditions (1) and (2). Since $|{0, 1}^n| = 2^n$, any NFA accepting $L$ has at least $2^n$ states.



          [1] I. Glaister and J. Shallit, A lower bound technique for the size of nondeterministic finite automata. Information Processing Letters 59 (2), pp. 75–77, (1996). DOI:10.1016/0020-0190(96)00095-6.






          share|cite|improve this answer





















          • Thank you for the answer!
            – Arda Akdemir
            Nov 29 '18 at 6:20














          0












          0








          0






          The answer to the relevant question refers to
          a theorem of [1] that can be used to determine lower bounds on the number of states of a minimal NFA:




          Theorem. Let $L subseteq Sigma^*$ be a regular language and suppose that there exist $n$ pairs of words $P = {(u_i, v_i) mid 1 leqslant i leqslant n }$ such that:





          1. $u_iv_i in L$ for $1 leqslant i leqslant n$


          2. $u_jv_i notin L$ for $1 leqslant i,j leqslant n$ and $i not= j$.


          Then any NFA accepting $L$ has at least $n$ states.




          Suppose that $Sigma = {a_1, dots, a_n}$. For each $i = (i_1, dots, i_n) in {0, 1}^n$, let $u_i = v_i = a_{i_1}^{i_1} a_{i_2}^{i_2} dotsm a_{i_n}^{i_n}$. By construction, $u_i$ and $v_i$ satisfy the conditions (1) and (2). Since $|{0, 1}^n| = 2^n$, any NFA accepting $L$ has at least $2^n$ states.



          [1] I. Glaister and J. Shallit, A lower bound technique for the size of nondeterministic finite automata. Information Processing Letters 59 (2), pp. 75–77, (1996). DOI:10.1016/0020-0190(96)00095-6.






          share|cite|improve this answer












          The answer to the relevant question refers to
          a theorem of [1] that can be used to determine lower bounds on the number of states of a minimal NFA:




          Theorem. Let $L subseteq Sigma^*$ be a regular language and suppose that there exist $n$ pairs of words $P = {(u_i, v_i) mid 1 leqslant i leqslant n }$ such that:





          1. $u_iv_i in L$ for $1 leqslant i leqslant n$


          2. $u_jv_i notin L$ for $1 leqslant i,j leqslant n$ and $i not= j$.


          Then any NFA accepting $L$ has at least $n$ states.




          Suppose that $Sigma = {a_1, dots, a_n}$. For each $i = (i_1, dots, i_n) in {0, 1}^n$, let $u_i = v_i = a_{i_1}^{i_1} a_{i_2}^{i_2} dotsm a_{i_n}^{i_n}$. By construction, $u_i$ and $v_i$ satisfy the conditions (1) and (2). Since $|{0, 1}^n| = 2^n$, any NFA accepting $L$ has at least $2^n$ states.



          [1] I. Glaister and J. Shallit, A lower bound technique for the size of nondeterministic finite automata. Information Processing Letters 59 (2), pp. 75–77, (1996). DOI:10.1016/0020-0190(96)00095-6.







          share|cite|improve this answer












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          share|cite|improve this answer










          answered Nov 28 '18 at 17:36









          J.-E. Pin

          18.3k21754




          18.3k21754












          • Thank you for the answer!
            – Arda Akdemir
            Nov 29 '18 at 6:20


















          • Thank you for the answer!
            – Arda Akdemir
            Nov 29 '18 at 6:20
















          Thank you for the answer!
          – Arda Akdemir
          Nov 29 '18 at 6:20




          Thank you for the answer!
          – Arda Akdemir
          Nov 29 '18 at 6:20


















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