8,059 research outputs found
Statistical and dynamical decoupling of the IGM from Dark Matter
The mean mass densities of cosmic dark matter is larger than that of baryonic
matter by a factor of about 5 in the CDM universe. Therefore, the
gravity on large scales should be dominant by the distribution of dark matter
in the universe. However, a series of observations incontrovertibly show that
the velocity and density fields of baryonic matter are decoupling from
underlying dark matter field. This paper shows our attemps to unveil the
physics behind this puzzle. In linear approximation, the dynamics of the baryon
fluid is completely governed by the gravity of the dark matter. Consequently,
the mass density field of baryon matter will be
proportional to that of dark matter , even though
they are different from each other initially. In weak and moderate nonlinear
regime, the dynamics of the baryon fluid can be sketched by Burgers equation. A
basic feature of the Burgers dynamics is to yield shocks. When the Reynolds
number is large, the Burgers fluid will be in the state of Burgers turbulence,
which consists of shocks and complex structures. On the other hand, the
collisionless dark matter may not show such shock, but a multivalued velocity
field. Therefore, the weak and moderate nonlinear evolution leads to the
IGM-dark matter deviation. Yet, the velocity field of Burgers fluid is still
irrotational, as gravity is curl-free. In fully nonlinear regime, the vorticity
of velocity field developed, and the cosmic baryonic fluid will no longer be
potential, as the dynamics of vorticity is independent of gravity and can be
self maintained by the nonlinearity of hydrodynamics. In this case, the cosmic
baryon fluid is in the state of fully developed turbulence, which is
statistically and dynamically decoupling from dark matter. This scenario
provides a mechanism of cohenent explanation of observations.Comment: 21 page
Indirect unitarity violation entangled with matter effects in reactor antineutrino oscillations
If finite but tiny masses of the three active neutrinos are generated via the
canonical seesaw mechanism with three heavy sterile neutrinos, the 3\times 3
Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix V will not be exactly
unitary. This kind of indirect unitarity violation can be probed in a precision
reactor antineutrino oscillation experiment, but it may be entangled with
terrestrial matter effects as both of them are very small. We calculate the
probability of \overline{\nu}_e \to \overline{\nu}_e oscillations in a good
analytical approximation, and find that, besides the zero-distance effect, the
effect of unitarity violation is always smaller than matter effects, and their
entanglement does not appear until the next-to-leading-order oscillating terms
are taken into account. Given a 20-kiloton JUNO-like liquid scintillator
detector, we reaffirm that terrestrial matter effects should not be neglected
but indirect unitarity violation makes no difference, and demonstrate that the
experimental sensitivities to the neutrino mass ordering and a precision
measurement of \theta_{12} and \Delta_{21} \equiv m^2_2 - m^2_1 are robust.Comment: 21 pages, 6 figures, version to be published in PLB, more discussions
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Coupled-channel analysis of the possible , and molecular states
We perform a coupled-channel study of the possible deuteron-like molecules
with two heavy flavor quarks, including the systems of with
double charm, with double bottom and
with both charm and bottom, within the
one-boson-exchange model. In our study, we take into account the S-D mixing
which plays an important role in the formation of the loosely bound deuteron,
and particularly, the coupled-channel effect in the flavor space. According to
our calculation, the states and
with double charm, the states
,
and
with double bottom, and
the states and
with both charm and bottom are good
molecule candidates. However, the existence of the states
with double charm and
with both charm and bottom is ruled out.Comment: 1 figure added, published in Physical Review
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