For each let Ƶm = {0, 1, 2, . . . , m − 1}, and let = (Ƶm, +, ×) be the model whose universe is Ƶm and that has relations corresponding to the + and × relations computed modulo m. Show that for each m, the theory Th is decidable.

Short Answer

Expert verified

Answer:

This statement is decidable is given below.

Step by step solution

01

Turing Machine

A Turing Machine is computational model concept that runs on the unrestricted grammar of Type-zero. It accepts recursive enumerable language. It comprises of an infinite tape length where read and write operation can be perform accordingly.

02

Problem is decidfable.

Mm={0,1,2,...,m-1}form>1is a universe

Mm=(Pm'+,x)model whose universe is pm.

+ and x are relations over modulo m.

We need to show that Thfm is decidable.

We can clear observe that Ƶm is finite as up to m terms.

So we can easily enumerate all possible values into formula and check if the formula is right or not.

  • If it is TRUE, then it belong to Thfm.
  • If it is NOT TRUE, then it belong to Thfm.


Let, Ǝxi such that ϕ=x1,x2,,xi Put Xi=0,1,,m-|


So, if formulaϕ=x1,x2,,xi is true for any value of xi then the original value is true.


Now, a model of theory is considered to be decidable if the formula which is true and also belong to the model.


So, by above recursive strategy, we say is decidable.

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Most popular questions from this chapter

Using the solution you gave to Exercise 1.25, give a formal description of the machines T1 and T2depicted in Exercise 1.24

Question:Consider the algorithm MINIMIZE, which takes a DFA as input and outputs DFA .

MINIMIZE = “On input , where M=(Q,Σ,δ,q0,A) is a DFA:

1.Remove all states of G that are unreachable from the start state.

2. Construct the following undirected graph G whose nodes are the states of .

3. Place an edge in G connecting every accept state with every non accept state. Add additional edges as follows.

4. Repeat until no new edges are added to G :

5. For every pair of distinct states q and r of and every aΣ :

6. Add the edge (q,r) to G if δq,a,δr,a is an edge of G .

7. For each state q,let[q] be the collection of statesq={rQ|noedge joins q and r in G }.

8.Form a new DFA M'=Q',Σ,δ',q'0,A'where

Q'={[q]|qQ}(ifq=r,onlyoneofthemisinQ'),δ'(q,a)=[δq,a]foreveryqQandaΣ,q00=[q0],andA0={[q]|qA}

9. Output ( M')”

a. Show that M and M' are equivalent.

b. Show that M0 is minimal—that is, no DFA with fewer states recognizes the same language. You may use the result of Problem 1.52 without proof.

c. Show that MINIMIZE operates in polynomial time.

Let MODEXP={ha,b,c,pi|a,b,c,andpare positive binary integers such that abcmodp}.

Show that MODEXPP. (Note that the most obvious algorithm doesn’t run in polynomial time. Hint: Try it first where b is a power of 2 .)

Let J={w|eitherw=0xfor some,xATM orw=1yfor some yATM¯}. Show that neither JnorJis Turing-recognizable.

In Corollary 4.18, we showed that the set of all languages is uncountable. Use this result to prove that languages exist that are not recognizable by an oracle Turing machine with an oracle for ATM.

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