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Superheavy sterile neutrinos as dark matter
Abstract
Chung, Kolb, and Riotto have proposed nonthermal mechanisms for the production of superheavy dark matter, consisting of particles with masses which may range up to the GUT scale. Shi and Fuller, on the other hand, have proposed much lighter sterile neutrinos as a dark matter candidate, produced through MSW conversion of active neutrinos. Recently Allen proposed a different nonthermal mechanism for the production of superheavy sterile neutrinos. Such neutrinos are predicted by an SO(10) grand-unified theory, and they lead, through the seesaw mechanism, to masses for ordinary left-handed neutrinos which are consistent with recent atmospheric and solar neutrino observations. The main mechanism discussed here involves the continuous formation of an SO(10) GUT Higgs condensate in the very early universe, with no phase transition. (This behavior near the Big Bang singularity is analogous to the behavior of an ordinary superfluid near a vortex singularity.) Superheavy "right-handed neutrinos'' acquire their mass from a Yukawa coupling to a Higgs field H. During an "inflationary'' period, in which the scale factor R(t) grows exponentially with the proper time t, {H} is very small. During this same period, therefore, the sterile "right-handed'' neutrinos have very small masses, and can be easily produced by quantum fluctuations. At a later stage, however, when the condensate is fully formed, these particles are superheavy, with masses near the GUT scale. They can then play the role of cold dark matter in subsequent structure formation. Since superheavy sterile neutrinos are a novel candidate for dark matter, it is far from obvious that they are consistent with observation and with established theoretical ideas. In this thesis we examine the central issues concerning the viability of such particles as a dark matter candidate. In particular, we consider various production mechanisms (including the one emphasized above), the question of stability over cosmological times, the consistency with various experiments involving neutrino oscillations, and consistency with the general framework of an SO(10) grand unified theory. The principal conclusion of this thesis is that the major component of dark matter in the universe could be the superheavy particles proposed here.
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Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 44-47).
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Citation
Tang, Yongjun (2000). Superheavy sterile neutrinos as dark matter. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2000 -THESIS -T37.
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