499 research outputs found
Is dark matter a BEC or scalar field?
This is a brief review on the history of the Bose-Einstein condensate (BEC)
or boson star model of galactic dark matter halos, where ultra-light scalar
dark matter particles condense in a single BEC quantum state. The halos can be
described as a self-gravitating, possibly self-interacting, coherent scalar
field.
On a scale larger than galaxies, dark matter behaves like cold dark matter
while below that scale the quantum mechanical nature suppresses the dark matter
structure formation due to the minimum length scale determined by the mass
m\st{>}{\sim}10^{-24} eV and the self-interaction of the particles. This
property could alleviate the cusp problem and missing satellite problems of the
CDM model. Furthermore, this model well reproduces the observed
rotation curves of spiral and dwarf galaxies, which makes the model promising.Comment: published versio
Characteristic Size and Mass of Galaxies in the Bose-Einstein Condensate Dark Matter Model
We study the characteristic length scale of galactic halos in the
Bose-Einstein condensate (or scalar field) dark matter model. Considering the
evolution of the density perturbation we show that the average background
matter density determines the quantum Jeans mass and hence the spatial size of
galaxies at a given epoch. In this model the minimum size of galaxies increases
while the minimum mass of the galaxies decreases as the universe expands. The
observed values of the mass and the size of the dwarf galaxies are successfully
reproduced with the dark matter particle mass . The
minimum size is about and the typical
rotation velocity of the dwarf galaxies is ) c, where is the
Hubble parameter and is the Compton wave length of the particle. We
also suggest that ultra compact dwarf galaxies are the remnants of the dwarf
galaxies formed in the early universe.Comment: Accepted for publication in Physics letters
Brief History of Ultra-light Scalar Dark Matter Models
This is a review on the brief history of the scalar field dark matter model
also known as fuzzy dark matter, BEC dark matter, wave dark matter, or
ultra-light axion.
In this model ultra-light scalar dark matter particles with mass condense in a single Bose-Einstein condensate state and behave
collectively like a classical wave. Galactic dark matter halos can be described
as a self-gravitating coherent scalar field configuration called boson stars.
At the scale larger than galaxies the dark matter acts like cold dark matter,
while below the scale quantum pressure from the uncertainty principle
suppresses the smaller structure formation so that it can resolve the small
scale crisis of the conventional cold dark matter model.Comment: 5 page
Fermion Scattering at a Phase Wave
We study fermion reflection at a phase wave which is formed during a bubble
collision in a first order phase transition. We calculate the reflection and
the transmission coefficients by solving the Dirac equation with the phase wave
background. Using the results we analyze the damping and the velocity of the
wave.Comment: 19 pages. Standard Latex file with 2 tex figure
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