A point particle is an idealized particle heavily used in physics. It's distinguishing features are that it does not have any volume or surface area; it is zero dimensional. A point particle is often a good approximation of real particles and also more extended bodies. In Newtonian gravition as well as General relativity and Electromagnetism, the respective fields produced by spherical objects and point particles of equal charge/mass are equal outside of the spherical object.
Particle physics is the most fundamental area of science in that its goal is to reduce the wonderful diversity and complexity of our universe to a few simple mathematical laws.
On the other hand, there exist other particles which are massless, especially the graviton, photon, and gluons, and this suggested that these string theories be used instead to describe these fundamental particles, including the quarks and gluons from which the hadrons are made.
Although quantization of the particle is straightforward, consistency of the quantization of the string introduces a particularly unusual feature: The dimension of spacetime is determined to be 26 for the simplest string, and 10 or 2 for those with extra degrees of freedom.
In Newtonian gravitation and classical electromagnetism, for example, the respective fields outside of a spherical object are identical to those of a pointparticle of equal charge/mass located at the center of the sphere.
In general relativity a pointparticle with mass only "exists" in the sense of "test particle", inasmuch as its influence on the curvature of spacetime must be ignored.
quantum field theory), "pointparticle" is synonymous with "elementary particle", which is defined as a particle without structure or, equivalently, as a particle lacking component parts.
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