Joseph Louis François Bertrand (March 11, 1822 - April 5, 1900, born and died in Paris) was a French mathematician who worked in the fields of number theory, differential geometry, probability theory, and thermodynamics.
Bertrand was a professor at the École Polytechnique and the Collège de France. He was a member of the Paris Academy of Sciences and was its permanent secretary for twenty-six years.
He conjectured, in 1845, that there is at least one prime between n and 2n-2 for every n > 3. Chebyshev proved this conjecture, now called Bertrand's postulate, in 1850.
Bertrand translated into French
Carl Friedrich Gauss's work on the theory of errors and the method of least squares.
In the field of economics he reviewed the work on Oligopoly Theory produced by the French mathematician and economist Augustin Cournot . The model of Bertrand competition argued that Cournot had reached a misleading conclusion; reworking Cournot's duopoly model using prices rather than quantities as the strategic variables thus showing that the equilibrium price was simply the competitive price - a striking conclusion largely ignored until recently.
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