Urca process


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Urca process

[′ər·kə ‚prä‚ses]
(astrophysics)
A series of nuclear reactions, chiefly among the iron group of elements, that are postulated as a cause of stellar collapse, due to the energy lost to neutrinos that are rapidly formed in the reactions.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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For example, the neutrino emissivity from modified quark URCA process is given as [36]
Haensel, "Direct URCA process in neutron stars," Physical Review Letters, vol.
This leads to marginally faster cooling of the neutron star due to neutrino emission URCA processes and the quark-neutrino scattering reaction.
The superfluidity of nucleons in NSs strongly suppresses most mechanisms of neutrino emission operating in the nonsuperfluid nucleon matter (the bremsstrahlung at nucleon collisions, modified Urca processes, etc.
In Figure 3, the PBF neutrino emissivity, as given in (54), is shown together with the emissivities of modified Urca processes and bremsstrahlung multiplied by the corresponding suppression factors resulting from superfluidity, as obtained in [49].
The minimal cooling paradigm assumes that the direct Urca processes and any exotic fast reactions are not operative in the NC core.
The following is the analogue of the simple URCA processes:
These reactions constitute simple URCA processes, in which there is a net loss of a [v.sub.l][[bar.v].sub.l] pair at nonzero temperatures.
The UHE neutrinos with energies up to hundreds ZeV are produced in superdense protomatter medium via simple (quark and pionic reactions) or modified URCA processes, even after the neutrino trapping.