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  2. Optimal control - Wikipedia

    en.wikipedia.org/wiki/Optimal_control

    A particular form of the LQ problem that arises in many control system problems is that of the linear quadratic regulator (LQR) where all of the matrices (i.e., , , , and ) are constant, the initial time is arbitrarily set to zero, and the terminal time is taken in the limit (this last assumption is what is known as infinite horizon). The LQR ...

  3. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    A black hole event horizon is teleological in nature, meaning that it is determined by future causes. [14] [15] [16] More precisely, one would need to know the entire history of the universe and all the way into the infinite future to determine the presence of an event horizon, which is not possible for quasilocal observers (not even in principle).

  4. Absolute horizon - Wikipedia

    en.wikipedia.org/wiki/Absolute_horizon

    In general relativity, an absolute horizon is a boundary in spacetime, defined with respect to the external universe, inside which events cannot affect an external observer. Light emitted inside the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again by the observer.

  5. Three-body problem - Wikipedia

    en.wikipedia.org/wiki/Three-body_problem

    While a system of 3 bodies interacting gravitationally is chaotic, a system of 3 bodies interacting elastically is not. [clarification needed] There is no general closed-form solution to the three-body problem. [1] In other words, it does not have a general solution that can be expressed in terms of a finite number of standard mathematical ...

  6. Algebraic Riccati equation - Wikipedia

    en.wikipedia.org/wiki/Algebraic_Riccati_equation

    which is known as the discrete-time dynamic Riccati equation of this problem. The steady-state characterization of P, relevant for the infinite-horizon problem in which T goes to infinity, can be found by iterating the dynamic equation repeatedly until it converges; then P is characterized by removing the time subscripts from the dynamic equation.

  7. Kruskal–Szekeres coordinates - Wikipedia

    en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates

    The black hole event horizon bordering exterior region I would coincide with a Schwarzschild t-coordinate of + while the white hole event horizon bordering this region would coincide with a Schwarzschild t-coordinate of , reflecting the fact that in Schwarzschild coordinates an infalling particle takes an infinite coordinate time to reach the ...

  8. Bekenstein bound - Wikipedia

    en.wikipedia.org/wiki/Bekenstein_bound

    According to the Bekenstein bound, the entropy of a black hole is proportional to the number of Planck areas that it would take to cover the black hole's event horizon.. In physics, the Bekenstein bound (named after Jacob Bekenstein) is an upper limit on the thermodynamic entropy S, or Shannon entropy H, that can be contained within a given finite region of space which has a finite amount of ...

  9. Millennium Prize Problems - Wikipedia

    en.wikipedia.org/wiki/Millennium_Prize_Problems

    The conjecture is that there is a simple way to tell whether such equations have a finite or infinite number of rational solutions. More specifically, the Millennium Prize version of the conjecture is that, if the elliptic curve E has rank r , then the L -function L ( E , s ) associated with it vanishes to order r at s = 1 .