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Role of Axions in Structure Formation in the Universe
Başlık:
Role of Axions in Structure Formation in the Universe
Yazar:
Banik, Nilanjan, author.
ISBN:
9780438120280
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (144 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-11(E), Section: B.
Özet:
One of the most profound puzzles of modern day science is to understand the nature of dark matter. Axions that arise as a result of the solution to the CP problem in the theory of strong interactions are one of the leading dark matter candidates. A remarkable property that sets axions apart from other dark matter candidates is that they thermalize via gravitational self-interactions to form a Bose-Einstein Condensate (BEC). Axion BEC behaves differently from other dark matter candidates over time scales longer than their thermalization time.
This dissertation is a compilation of my published works, in which we have explored novel ways axion dark matter can affect structure formation in the Universe. After a brief historical review on dark matter we review in detail the Bose-Einstein condensation of axion dark matter. We show that density perturbations in the early Universe can be given a wavefunction description. We then show that the evolution of axion dark matter can only be described by quantum field theory on time scales longer than their thermalization time. Next, we show that imparting angular momentum to a system of axion BEC gives rise to vortices and these vortices can combine to form bigger vortices. Axion BEC vorticity will give rise to vorticity in baryons due to thermalization. We show that during recombination, the baryon vorticity will seed primordial magnetic fields.
We then present a technique for obtaining the leading behavior of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the local flow of dark matter from the sharpness of the nearby caustic, and a prediction for the dispersions in its velocity components is obtained. Ultralight axionlike particles (ULALPs) have been predicted in many String Theory based extensions of Standard Model and is a popular dark matter candidate. We show that like QCD axions, ULALPs form a BEC. We then derive lower mass bounds on ULALPs based on heating effect of infalling ULALPs on galactic disk stars and the thickness of the nearby caustic ring.
Notlar:
School code: 0070
Tüzel Kişi Ek Girişi:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(696570.1) | 696570-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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