Energy of the zero point – Wikipedia

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L’ zero -point energy is the lowest possible energy that a quantum physical system may have; This corresponds to his energy when he is in his fundamental state, that is to say when any other form of energy has been removed [ first ] , [ 2 ] .

All quantum mechanical systems undergo fluctuations even when they are in their fundamental state (with which an energy of the zero point is associated), a consequence of their wave nature. The principle of uncertainty implies that each physical system has a zero point for its energy, greater than the minimum of its classic potential well. At macroscopic scales, this energy is negligible because fluctuations are canceled over large volumes. This energy, however, has microscopic physical effects such as the Casimir effect, the spontaneous emission of photons by atoms, the creation of pairs of particles/antiparticles, or a minimum agitation of the molecules.

This implies in particular that the temperature of absolute zero cannot be reached microscopically, because of the minimum agitation of the matter or the existence of zero point energy.
This leads to movement even at absolute zero. For example, liquid helium does not freeze under atmospheric pressure, whatever the temperature, because of its zero -point energy.

The concept of energy of the zero point was developed by Max Planck in Germany in 1911 as a correction term added to the equation of its original quantum theory dating from 1900. The term zero -point energy is a translation of the German word “nulpunksenergie”.

The energy of the vacuum is the particular case where the “physical system” is emptiness.

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A classic system can be motionless at its minimum energy in classic potential. A quantum system in this same potential is described by a wave function, which is relocated and remains in a state of quantum fluctuation, according to the principle of Heisenberg, with a kinetic energy which believes as the reverse of the dimension of location quantum describing this movement. In the fundamental state this location energy is called zero point energy, which is associated with a zero quantum point movement.

For example, a quantum harmonic oscillator has a fundamental fundamental state of energy half of its classic frequency multiplied by the Planck constant.

ϵ = hν2{Displaystyle Epsilon = {Frac {hnu} {2}}}}

This property is found in acoustic waves which are quantum in atomic displacements and called phonons with a collective point movement of atoms which is observed on each atom by X -ray and radiocristallography in the form of an imprecision of position.

When the atoms are very light and in a low interatomic potential as for heliums 3 and 4, the zero point energy is sufficient to give an amplitude of zero point movement so large compared to the interatomic distances that helium cannot More solidify and remains liquid with zero pressure.

A characteristic of this zero point agitation, very different from a classic disorderly thermal agitation, is that it is described by a coherent collective quantum wave function, with perpetual movements without any dissipation, without viscosity or resistance. Taking into account the statistics of helium 3 or 4 atoms, this liquid in its zero quantum movement becomes superfluous, flowing without dissipation [ 3 ] , with perpetual quantum flows without any dissipation [ 4 ] , because they are in their fundamental quantum collective state of zero point movement. This movement is observed in the macroscopic state as a superfluid or a superconductor [ 5 ] .

All quantum fields, such as the electromagnetic field with its quantum photons, in the void, also have a zero point movement whose variations are observed, as revealed in the experience of the Casimir effect, in the form of a force between two plates or materials.

  1. ↑ Calphysics Institute : Zero point energy and zero point field .
  2. ↑ ‘ Void energy » , on media4.obbspm.fr (archived) (consulted the ) .
  3. ↑ (in) V. F. Vinen, ‘ THE PHYSICS OF SUPERFLUID HELIUM» .
  4. ↑ (in) John Emsley, Nature’s building blocks : an A-Z guide to the elements , Oxford New York, Oxford University Press, , 538 p. (ISBN  978-0-19-850341-5 , OCLC  46984609, read online ) , p. 175–179 .
  5. ↑ Institute of CNRS physics, ‘ Supervisactivity zero resistance and superfluous » .

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