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In relativistic physics, Lorentz symmetry or Lorentz invariance, named after the Dutch physicist Hendrik Lorentz, is an equivalence of observation or observational symmetry due to special relativity implying that the laws of physics stay the same for all observers that are moving with respect to one another within an inertial frame. It has also ...
The following notations are used very often in special relativity: Lorentz factor = where = and v is the relative velocity between two inertial frames.. For two frames at rest, γ = 1, and increases with relative velocity between the two inertial frames.
This form is invariant under the Lorentz group, so that for S ∈ SL(2, C) one has , = , This defines a kind of "scalar product" of spinors, and is commonly used to defined a Lorentz-invariant mass term in Lagrangians. There are several notable properties to be called out that are important to physics.
The difference between this and the spacetime interval = in Minkowski space is that = is invariant purely by the principle of relativity whereas = requires both postulates. The "principle of relativity" in spacetime is taken to mean invariance of laws under 4-dimensional transformations.
This can also be expressed in terms of the four-velocity by the equation: [2] [3] = = where: is the charge density measured by an inertial observer O who sees the electric current moving at speed u (the magnitude of the 3-velocity);
From the invariance of the spacetime interval it follows = and this matrix equation contains the general conditions on the Lorentz transformation to ensure invariance of the spacetime interval. Taking the determinant of the equation using the product rule [ nb 4 ] gives immediately [ det ( Λ ) ] 2 = 1 ⇒ det ( Λ ) = ± 1 {\displaystyle \left ...
One of the central features of GR is the idea of invariance of physical laws. This invariance can be described in many ways, for example, in terms of local Lorentz covariance, the general principle of relativity or diffeomorphism covariance. A more explicit description can be given using tensors.
A quantity that is invariant under Lorentz transformations is known as a Lorentz scalar. Writing the Lorentz transformation and its inverse in terms of coordinate differences, where one event has coordinates (x 1, t 1) and (x ′ 1, t ′ 1), another event has coordinates (x 2, t 2) and (x ′ 2, t ′ 2), and the differences are defined as