Vacuum polarization

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In <a href="/facts/Quantum_field_theory/VoewsNJV">quantum field theory</a>, and specifically <a href="/facts/Quantum_electrodynamics/zPteAr6G">quantum electrodynamics</a>, vacuum polarization describes a process in which a background <a href="/facts/Electromagnetic_field/MacraS8y">electromagnetic field</a> produces <a href="/facts/Virtual_particle/CfHFkVL3">virtual</a> <a href="/facts/Electron/L0KBo5cW">electron</a>–<a href="/facts/Positron/HgV4zBzA">positron</a> pairs that change the distribution of charges and currents that generated the original electromagnetic field.  It is also sometimes referred to as the <a href="/facts/Self-energy/qhFMapN6">self-energy</a> of the <a href="/facts/Gauge_boson/TEEpAwxJ">gauge boson</a> (<a href="/facts/Photon/mFNhAEzA">photon</a>). It is analogous to the electric <a href="/facts/Polarization_density/2oQv9EHx">polarization</a> of <a href="/facts/Dielectric/PnVt9P2G">dielectric</a> materials, but in <a href="/facts/Vacuum/BTk3goyV">vacuum</a> without the need of a medium.
</p><p>The effects of vacuum polarization have been routinely observed experimentally since then as very well-understood background effects. Vacuum polarization, referred to below as the one loop contribution, occurs with leptons (electron–positron pairs) or quarks. 
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Vacuum polarization open-in-new

Vacuum polarization