25,681 research outputs found
Observe matter falling into a black hole
It has been well known that in the point of view of a distant observer, all
in-falling matter to a black hole (BH) will be eventually stalled and "frozen"
just outside the event horizon of the BH, although an in-falling observer will
see the matter falling straight through the event horizon. Thus in this "frozen
star" scenario, as distant observers, we could never observe matter falling
into a BH, neither could we see any "real" BH other than primordial ones, since
all other BHs are believed to be formed by matter falling towards singularity.
Here we first obtain the exact solution for a pressureless mass shell around a
pre-existing BH. The metrics inside and interior to the shell are all different
from the Schwarzschild metric of the enclosed mass. The metric interior to the
shell can be transformed to the Schwarzschild metric for a slower clock which
is dependent of the location and mass of the shell. Another result is that
there does not exist a singularity nor event horizon in the shell. Therefore
the "frozen star" scenario is incorrect. We also show that for all practical
astrophysical settings the in-falling time recorded by an external observer is
sufficiently short that future astrophysical instruments may be able to follow
the whole process of matter falling into BHs. The distant observer could not
distinguish between a "real" BH and a "frozen star", until two such objects
merge together. It has been proposed that electromagnetic waves will be
produced when two "frozen stars" merge together, but not true when two "real"
bare BHs merge together. However gravitational waves will be produced in both
cases. Thus our solution is testable by future high sensitivity astronomical
observations.Comment: 7 pages, 2 figures. Proceeding of the conference "Astrophysics of
Compact Objects", 1-7 July, Huangshan, China. Abridged abstrac
Phenomenological discriminations of the Yukawa interactions in two-Higgs doublet models with symmetry
There are four types of two-Higgs doublet models under a discrete
symmetry imposed to avoid tree-level flavour-changing neutral current, i.e.
type-I, type-II, type-X and type-Y models. We investigate the possibility to
discriminate the four models in the light of the flavour physics data,
including mixing, , and
decays, the recent LHC Higgs data, the direct search
for charged Higgs at LEP, and the constraints from perturbative unitarity and
vacuum stability. After deriving the combined constraints on the Yukawa
interaction parameters, we have shown that the correlation between the mass
eigenstate rate asymmetry of and the
ratio could be sensitive probe to discriminate the four models with
future precise measurements of the observables in the
decay at LHCb.Comment: 29 pages, 4 tables, 11 figures. v3: minor corrections included,
matches published version in EPJ
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