A surname

(physics) A relativistic paradox concerning the concept of Born rigidity within special relativity, where an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R₀ when stationary. However, the circumference should appear Lorentz-contracted to a smaller value than at rest. This leads to the contradiction that R = R₀ and R < R₀.

(physics) A theorem that relates the time derivative of the expectation values of the position and momentum operators x and p to the expectation value of the force F=-V'(x) on a massive particle moving in a scalar potential V(x).

plural of Ehrenfest equation

Any of a group of equations that describe changes in specific heat capacity and derivatives of specific volume in second-order phase transitions.

plural of Ehrenfest model

(thermodynamics) A model of diffusion used to explain the second law of thermodynamics, considering a number of particles in two containers, which independently change container at a certain rate.