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In meteorology, [2] helicity corresponds to the transfer of vorticity from the environment to an air parcel in convective motion. Here the definition of helicity is simplified to only use the horizontal component of wind and vorticity, and to only integrate in the vertical direction, replacing the volume integral with a one-dimensional definite integral or line integral:
The helicity of a particle is positive (" right-handed") if the direction of its spin is the same as the direction of its motion and negative ("left-handed") if opposite. Helicity is conserved. [1] That is, the helicity commutes with the Hamiltonian, and thus, in the absence of external forces, is time-invariant. It is also rotationally ...
Magnetic helicity is a gauge-dependent quantity, because can be redefined by adding a gradient to it (gauge choosing).However, for perfectly conducting boundaries or periodic systems without a net magnetic flux, the magnetic helicity contained in the whole domain is gauge invariant, [15] that is, independent of the gauge choice.
A correct description of such an object requires the application of Newton's second law to the entire, constant-mass system consisting of both the object and its ejected mass. [7] Mass flow rate can be used to calculate the energy flow rate of a fluid: [8] ˙ = ˙, where is the unit mass energy of a system.
Originally, the coupling constant related the force acting between two static bodies to the "charges" of the bodies (i.e. the electric charge for electrostatic and the mass for Newtonian gravity) divided by the distance squared, , between the bodies; thus: in = / for Newtonian gravity and in = / for electrostatic.
At equilibrium, the rate of net energy production in the system must equal the rate of energy loss due to frictional dissipation at the surface, i.e. W i n = W o u t {\displaystyle W_{in}=W_{out}} The rate of energy loss per unit surface area from surface friction, W o u t {\displaystyle W_{out}} , is given by
Helicity may refer to: Helicity (fluid mechanics) , the extent to which corkscrew-like motion occurs Helicity (particle physics) , the projection of the spin onto the direction of momentum
The two-component helicity eigenstates satisfy ^ (^) = (^) where are the Pauli matrices, ^ is the direction of the fermion momentum, = depending on whether spin is pointing in the same direction as ^ or opposite.