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  2. Borde–Guth–Vilenkin theorem - Wikipedia

    en.wikipedia.org/wiki/Borde–Guth–Vilenkin...

    Furthermore, there are examples of infinite cyclic models solving the problem of unbounded entropy growth which are geodesically complete. [14] In both of these studies, the authors argue that the previous investigations often did not use mathematically precise formulations of the BGV theorem and thus reached incomplete conclusions.

  3. Isotopes of antimony - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_antimony

    All other isotopes have half-lives less than 4 days, most less than an hour. There are also many isomers , the longest-lived of which is 120m1 Sb with half-life 5.76 days. Except for beryllium , antimony is the lightest element observed to have isotopes capable of alpha decay ; 104 Sb is seen to undergo this mode of decay.

  4. Plateau's problem - Wikipedia

    en.wikipedia.org/wiki/Plateau's_problem

    In mathematics, Plateau's problem is to show the existence of a minimal surface with a given boundary, a problem raised by Joseph-Louis Lagrange in 1760. However, it is named after Joseph Plateau who experimented with soap films. The problem is considered part of the calculus of variations.

  5. Antimony tetroxide - Wikipedia

    en.wikipedia.org/wiki/Antimony_tetroxide

    The material forms when Sb 2 O 3 is heated in air: [5] Sb 2 O 3 + 0.5 O 2 → Sb 2 O 4 ΔH = −187 kJ/mol. At 800 °C, antimony(V) oxide loses oxygen to give the same material: Sb 2 O 5 → Sb 2 O 4 + 0.5 O 2 ΔH = −64 kJ/mol. The material is mixed valence, containing both Sb(V) and Sb(III) centers.

  6. List of unsolved problems in mathematics - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, model theory, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations.

  7. Boundary value problem - Wikipedia

    en.wikipedia.org/wiki/Boundary_value_problem

    Boundary value problems are similar to initial value problems.A boundary value problem has conditions specified at the extremes ("boundaries") of the independent variable in the equation whereas an initial value problem has all of the conditions specified at the same value of the independent variable (and that value is at the lower boundary of the domain, thus the term "initial" value).

  8. Calculus of variations - Wikipedia

    en.wikipedia.org/wiki/Calculus_of_Variations

    The calculus of variations may be said to begin with Newton's minimal resistance problem in 1687, followed by the brachistochrone curve problem raised by Johann Bernoulli (1696). [2] It immediately occupied the attention of Jacob Bernoulli and the Marquis de l'Hôpital , but Leonhard Euler first elaborated the subject, beginning in 1733.

  9. Short integer solution problem - Wikipedia

    en.wikipedia.org/wiki/Short_integer_solution_problem

    The Short Integer Solution (SIS) problem is an average case problem that is used in lattice-based cryptography constructions. Lattice-based cryptography began in 1996 from a seminal work by Ajtai [ 1 ] who presented a family of one-way functions based on the SIS problem.