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  2. Hilbert's seventeenth problem - Wikipedia

    en.wikipedia.org/wiki/Hilbert's_seventeenth_problem

    An n-variable instance of 3-SAT can be realized as a positivity problem on a polynomial with n variables and d=4. This proves that positivity testing is NP-Hard . More precisely, assuming the exponential time hypothesis to be true, v ( n , d ) = 2 Ω ( n ) {\displaystyle v(n,d)=2^{\Omega (n)}} .

  3. Hilbert's problems - Wikipedia

    en.wikipedia.org/wiki/Hilbert's_problems

    Problems 1, 2, 5, 6, [a] 9, 11, 12, 15, and 22 have solutions that have partial acceptance, but there exists some controversy as to whether they resolve the problems. That leaves 8 (the Riemann hypothesis), 13 and 16 [b] unresolved. Problems 4 and 23 are considered as too vague to ever be described as solved; the withdrawn 24 would also be in ...

  4. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    The standard Collatz function is given by P = 2, a 0 = ⁠ 1 / 2 ⁠, b 0 = 0, a 1 = 3, b 1 = 1. Conway proved that the problem Given g and n, does the sequence of iterates g k (n) reach 1? is undecidable, by representing the halting problem in this way. Closer to the Collatz problem is the following universally quantified problem:

  5. Newcomb's paradox - Wikipedia

    en.wikipedia.org/wiki/Newcomb's_paradox

    Another related problem is the meta-Newcomb problem. [20] The setup of this problem is similar to the original Newcomb problem. However, the twist here is that the predictor may elect to decide whether to fill box B after the player has made a choice, and the player does not know whether box B has already been filled.

  6. Three-body problem - Wikipedia

    en.wikipedia.org/wiki/Three-body_problem

    The three-body problem is a special case of the n-body problem, which describes how n objects move under one of the physical forces, such as gravity. These problems have a global analytical solution in the form of a convergent power series, as was proven by Karl F. Sundman for n = 3 and by Qiudong Wang for n > 3 (see n-body problem for details

  7. Boolean satisfiability problem - Wikipedia

    en.wikipedia.org/wiki/Boolean_satisfiability_problem

    A variant of the 3-satisfiability problem is the one-in-three 3-SAT (also known variously as 1-in-3-SAT and exactly-1 3-SAT). Given a conjunctive normal form with three literals per clause, the problem is to determine whether there exists a truth assignment to the variables so that each clause has exactly one TRUE literal (and thus exactly two ...

  8. Four fours - Wikipedia

    en.wikipedia.org/wiki/Four_fours

    For example, when d=4, the hash table for two occurrences of d would contain the key-value pair 8 and 4+4, and the one for three occurrences, the key-value pair 2 and (4+4)/4 (strings shown in bold). The task is then reduced to recursively computing these hash tables for increasing n , starting from n=1 and continuing up to e.g. n=4.

  9. Circle packing in a circle - Wikipedia

    en.wikipedia.org/wiki/Circle_packing_in_a_circle

    Of these, solutions for n = 2, 3, 4, 7, 19, and 37 achieve a packing density greater than any smaller number > 1. (Higher density records all have rattles.) [ 10 ] See also