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The convection–diffusion equation describes the flow of heat, particles, or other physical quantities in situations where there is both diffusion and convection or advection. For information about the equation, its derivation, and its conceptual importance and consequences, see the main article convection–diffusion equation. This article ...
These can be used to find a general solution of the heat equation over certain domains (see, for instance, ). In one variable, the Green's function is a solution of the initial value problem (by Duhamel's principle, equivalent to the definition of Green's function as one with a delta function as solution to the first equation)
The term Friedmann equation sometimes is used only for the first equation. [3] In these equations, R(t) is the cosmological scale factor, is the Newtonian constant of gravitation, Λ is the cosmological constant with dimension length −2, ρ is the energy density and p is the isotropic pressure.
Water density calculator Archived July 13, 2011, at the Wayback Machine Water density for a given salinity and temperature. Liquid density calculator Select a liquid from the list and calculate density as a function of temperature. Gas density calculator Calculate density of a gas for as a function of temperature and pressure.
In quantum mechanics, a density matrix (or density operator) is a matrix that describes an ensemble [1] of physical systems as quantum states (even if the ensemble contains only one system). It allows for the calculation of the probabilities of the outcomes of any measurements performed upon the systems of the ensemble using the Born rule .
The table below essentially simplifies the ideal gas equation for a particular process, making the equation easier to solve using numerical methods. A thermodynamic process is defined as a system that moves from state 1 to state 2, where the state number is denoted by a subscript.
In other words, the solution of equation 2, u(x), can be determined by the integration given in equation 3. Although f ( x ) is known, this integration cannot be performed unless G is also known. The problem now lies in finding the Green's function G that satisfies equation 1 .
Siméon Denis Poisson. Poisson's equation is an elliptic partial differential equation of broad utility in theoretical physics.For example, the solution to Poisson's equation is the potential field caused by a given electric charge or mass density distribution; with the potential field known, one can then calculate the corresponding electrostatic or gravitational (force) field.