- Meeting 01 : Mon, Jul 30, 08:00 am-08:50 am
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Brief introduction to the course and the contents. Administrative Announcements. Grading policies.
Languages vs Algorithmic Problems. Automata theory vs algorithms courses. Historical aspects of the idea of computation. Ruler and Compass problem. Hilbert's problem. Need of understanding computation in very formal terms.
- Meeting 02 : Tue, Jul 31, 12:00 pm-12:50 pm
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Problem of Searching the Treasure on the number line. Algorithms. Drawbacks. Diophantine problem.
Formal model of computation. Post Systems, Mu-calculus, Lambda calculus. Turing machines. Formal Model of Turing machines.
- Meeting 03 : Thu, Aug 02, 11:00 am-11:50 am
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Configurations of TM model. Acceptance of a string by Turing machines. Decidable, semi-decidable and undecidable. Robustness of the Turing machine model. Tape reduction theorem.
- Meeting 04 : Fri, Aug 03, 10:00 am-10:50 am
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Encoding Turing machines as strings. Enumeration of Turing machines. Cantor's diagonalization argument for showing that R is uncountably infinite.
- Meeting 05 : Mon, Aug 06, 08:00 am-08:50 am
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First undecidable task. The proof that "entry filling machines" for the matrix defined, cannot exist. Discussions related to the implications.
- Meeting 06 : Tue, Aug 07, 12:00 pm-12:50 pm
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The halting problem. The membership problem. The undecidability of both languages. Relationship among that two languages. Two ways of observing the relation. Comparing the two methods.
- Meeting 07 : Thu, Aug 09, 11:00 am-11:50 am
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Formally capturing the relation between MP and HP. Definition of many-one reductions. Other natural forms of reductions.
- Meeting 08 : Fri, Aug 10, 10:00 am-10:50 am
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Does knowing the input in advance help? MP-101 problem. Proof that MP-101 is undecidable. MP-101 is equivalent to MP. Transitivity of reductions. Observations about the reduction. Showing that FULL, and EMPTY are undecidable.
- Meeting 09 : Tue, Aug 14, 12:00 pm-12:50 pm
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Other languages like EMPTY and FULL.
INF, REG, CFL, DEC. Undecidability of INF. Reduction from MP to INF. Reduction from MP to NREG. Reduction from MP to REG. Reduction from MP to NCFL. Reduction from MP to NDEC. Observations about the reductions.
- Meeting 10 : Thu, Aug 16, 11:00 am-11:50 am
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Rice-Myhill-Shapiro Theorem - I. Every nontrivial property of semi-decidable languages is undecidable. Example applications.
- Meeting 11 : Fri, Aug 17, 10:00 am-10:50 am
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Importance of the study of the class of semi-decidable languages. Closure properties of D and SD. Characterization of decidable languages and semi-decidable languages. Examples of languages which are not even semi-decidable. Showing that FIN is not even semi-decidable.
- Meeting 12 : Mon, Aug 20, 08:00 am-08:50 am
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Rice-Myhill-Shapiro Theorem - II. Every non-monotone property of semi-decidable languages is outside SD. Proof and Applications.
- Meeting 13 : Tue, Aug 21, 12:00 pm-12:50 pm
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Enumerability and semi-decidability. A characterization.
- Meeting 14 : Thu, Aug 23, 11:00 am-11:50 am
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An application : Godel's Incompleteness Theorem. Set up and the statement of the theorem.
- Meeting 15 : Fri, Aug 24, 10:00 am-10:50 am
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Proof of Godel's incompleteness theorem. Showing the Th(PA) is semi-decidable and T(N) is not even semidecidable. Reducing MP-complement to T(N). Validity of a computation history can be expressed as a FO formula VALCOMP(a) over the natural numbers.
References | : | [K1] Lecture on Proof of completeness theorem.
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- Meeting 16 : Mon, Aug 27, 08:00 am-08:50 am
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Hardness and Completeness in SD. MP is SD-complete. Other SD-complete languages. SD-complete languages are not decidable.
- Meeting 17 : Tue, Aug 28, 12:00 pm-12:50 pm
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Rich world outside SD. The MPXOR language. Oracle Turing machines. The class Sigma-2 and Delta-2. The class Pi-2.
- Meeting 18 : Thu, Aug 30, 11:00 am-11:50 am
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The arithmetic hierarchy. Proof that Delta-2 = Sigma2 intersection Pi-2.
- Meeting 19 : Fri, Aug 31, 10:00 am-10:50 am
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Relatizing the completeness proofs. MP^MP is Sigma-2 complete. The third level of the hierarchy.
- Meeting 20 : Tue, Sep 04, 12:00 pm-12:50 pm
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Quantifier Characterization of Arithmetic Hierarchy. The base case for SD. Applications to place languages in the AH. Placing REG, FIN, etc in AH.
- Meeting 21 : Thu, Sep 06, 11:00 am-11:50 am
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Placing MP^MP in Sigma_2 via the characterizations. Taking clues from the proof to lead to the proof of the characterization itself.
- Meeting 22 : Fri, Sep 07, 10:00 am-10:50 am
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Proof of Quantifier Characterization of Arithmetic Hierarchy.
- Meeting 23 : Mon, Sep 10, 08:00 am-08:50 am
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FIN is Sigma-2 complete. SD-intermediate languages. Proof strategy and discussions.
References | : | [K1] Textbook. Lecture on Arithmetic Hierarchy.
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- Meeting 24 : Tue, Sep 11, 12:00 pm-12:50 pm
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Posts theorem. Simple sets. Arriving at the definition of simple sets from the requirements. From simple sets Construction of simple sets. The algorithm and the proof idea.
References | : | Lecture 37 in [K2]
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- Meeting 25 : Fri, Sep 14, 10:00 am-10:50 am
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Productive sets. Complements of Simple sets cannot be productive.
References | : | Lecture 37 in [K2]
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- Meeting 26 : Mon, Sep 17, 08:00 am-08:50 am
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Complements of SD-complete sets are productive. Relativizing the Post's theorem.
References | : | Lecture 37 in [K2]
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- Meeting 27 : Tue, Sep 18, 12:00 pm-12:50 pm
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Freidburg-Muchnik Theorem. Formulating the proof strategy. Low simple sets.
References | : | Lecture 38 in [K2]
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- Meeting 28 : Thu, Sep 20, 11:00 am-11:50 am
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Construction of the low simple sets. Positive and Negative conditions.
References | : | Lecture 38 in [K2]
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- Meeting 29 : Tue, Sep 25, 12:00 pm-12:50 pm
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Details of Freidburg-Muchnik Theorem. Finite Injury arguments to satisfy the negative conditions.
References | : | Lecture 38 in [K2]
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