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  2. Penrose diagram - Wikipedia

    en.wikipedia.org/wiki/Penrose_diagram

    Penrose diagram of an infinite Minkowski universe, horizontal axis u, vertical axis v. In theoretical physics, a Penrose diagram (named after mathematical physicist Roger Penrose) is a two-dimensional diagram capturing the causal relations between different points in spacetime through a conformal treatment of infinity.

  3. 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 ...

  4. Tipler cylinder - Wikipedia

    en.wikipedia.org/wiki/Tipler_cylinder

    Tipler's original solution involved a cylinder of infinite length, which is easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, [6] he did not prove this. But Hawking comments: "it can't be done with positive energy density everywhere!

  5. Exact solutions in general relativity - Wikipedia

    en.wikipedia.org/wiki/Exact_solutions_in_general...

    These tensor fields should obey any relevant physical laws (for example, any electromagnetic field must satisfy Maxwell's equations).Following a standard recipe which is widely used in mathematical physics, these tensor fields should also give rise to specific contributions to the stress–energy tensor. [1]

  6. 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 ...

  7. 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 ...

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  9. Penrose–Hawking singularity theorems - Wikipedia

    en.wikipedia.org/wiki/Penrose–Hawking...

    A key tool used in the formulation and proof of the singularity theorems is the Raychaudhuri equation, which describes the divergence of a congruence (family) of geodesics. The divergence of a congruence is defined as the derivative of the log of the determinant of the congruence volume. The Raychaudhuri equation is