For ten points, identify this adjective, applied to a ubiquitous theorem that in its simplest form states that the average kinetic energy of a system is equal to minus one-half of the average potential energy of a system.
In statistical mechanics, coefficients described by this adjective are related to graph theory through the use of Mayer cluster integrals, and an ongoing debate exists as to whether the stress described by this adjective on the atomic level is equivalent to the Cauchy stress of macroscopic objects.  The Onnes equation is another name for the equation of state  or "expansion" described by this adjective, which can be used to find the Boyle temperature of a gas. The most well-known statement described by this adjective has been used to derive the Chandrasekhar limit for White Dwarfs. For ten points, identify this adjective, applied to a ubiquitous theorem that in its simplest form states that the average kinetic energy of a system is equal to minus one-half of the average potential energy of a system.
In statistical mechanics, coefficients described by this adjective are related to graph theory through the use of Mayer cluster integrals, and an ongoing debate exists as to whether the stress described by this adjective on the atomic level is equivalent to the Cauchy stress of macroscopic objects.  
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