Predicting dark matter particle mass, size, and properties from energy cascade and two-thirds law in dark matter flow. (arXiv:2202.07240v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Xu_Z/0/1/0/all/0/1">Zhijie Xu</a>
Dark matter can be characterized by the mass and size of its smallest
constituents, which are challenging to directly probe and detect. After years
of null results in the search for thermal WIMPs, a different prospective might
be required beyond the standard WIMP paradigm. We present a new approach to
estimate the dark matter particle mass, size, density, and many other relevant
properties based on the nature of flow of dark matter. A comparison with
hydrodynamic turbulence is presented to reveal the unique features of
self-gravitating collisionless dark matter flow, i.e. an inverse mass and
energy cascade from small to large scales with a scale-independent rate of
energy cascade $varepsilon_uapprox -4.6times 10^{-7}m^2/s^3$. For the
simplest case with only gravitational interaction involved and in the absence
of viscosity in flow, the energy cascade leads to a two-thirds law for pairwise
velocity that can be extended down to the smallest scale, where quantum effects
become important. Combining the rate of energy cascade $varepsilon_u$, the
Planck constant $hbar$, and the gravitational constant $G$ on the smallest
scale, the mass of dark matter particles is found to be around
$0.9times10^{12}GeV$ with a size around $3times10^{-13}m$. Since the mass
scale $m_X$ is only weakly dependent on $varepsilon_u$ as $m_X propto
(-varepsilon_uhbar^5/G^4)^{1/9}$, the estimation of $m_X$ should be robust
for a wide range of possible values of $varepsilon_u$. If gravity is the only
interaction and dark matter is fully collisionless, mass of around $10^{12}GeV$
is required to produce the given rate of energy cascade $varepsilon_u$. In
other words, if mass has a different value, there must be new interaction
beyond gravity. This work suggests a heavy dark matter scenario produced in the
early universe ($sim 10^{-14}s$). Potential extension to self-interacting dark
matter is also presented.
Dark matter can be characterized by the mass and size of its smallest
constituents, which are challenging to directly probe and detect. After years
of null results in the search for thermal WIMPs, a different prospective might
be required beyond the standard WIMP paradigm. We present a new approach to
estimate the dark matter particle mass, size, density, and many other relevant
properties based on the nature of flow of dark matter. A comparison with
hydrodynamic turbulence is presented to reveal the unique features of
self-gravitating collisionless dark matter flow, i.e. an inverse mass and
energy cascade from small to large scales with a scale-independent rate of
energy cascade $varepsilon_uapprox -4.6times 10^{-7}m^2/s^3$. For the
simplest case with only gravitational interaction involved and in the absence
of viscosity in flow, the energy cascade leads to a two-thirds law for pairwise
velocity that can be extended down to the smallest scale, where quantum effects
become important. Combining the rate of energy cascade $varepsilon_u$, the
Planck constant $hbar$, and the gravitational constant $G$ on the smallest
scale, the mass of dark matter particles is found to be around
$0.9times10^{12}GeV$ with a size around $3times10^{-13}m$. Since the mass
scale $m_X$ is only weakly dependent on $varepsilon_u$ as $m_X propto
(-varepsilon_uhbar^5/G^4)^{1/9}$, the estimation of $m_X$ should be robust
for a wide range of possible values of $varepsilon_u$. If gravity is the only
interaction and dark matter is fully collisionless, mass of around $10^{12}GeV$
is required to produce the given rate of energy cascade $varepsilon_u$. In
other words, if mass has a different value, there must be new interaction
beyond gravity. This work suggests a heavy dark matter scenario produced in the
early universe ($sim 10^{-14}s$). Potential extension to self-interacting dark
matter is also presented.
http://arxiv.org/icons/sfx.gif
