8,628 research outputs found
Comment on 'Note on the dog-and-rabbit chase problem in introductory kinematics'
We comment on the recent paper by Yuan Qing-Xin and Du Yin-Xiao (Eur. J.
Phys. 29 (2008) N43-N45).Comment: 2 pages, no figure
Origins of the Isospin Violation of Dark Matter Interactions
Light dark matter (DM) with a large DM-nucleon spin-independent cross section
and furthermore proper isospin violation (ISV) may provide
a way to understand the confusing DM direct detection results. Combing with the
stringent astrophysical and collider constraints, we systematically investigate
the origin of ISV first via general operator analyses and further via
specifying three kinds of (single) mediators: A light from chiral
, an approximate spectator Higgs doublet (It can explain the
anomaly simultaneously) and color triplets. In addition, although from an
exotic mixing with generating , we can combine it with
the conventional Higgs to achieve proper ISV. As a concrete example, we propose
the model where the charged light sneutrino is the inelastic
DM, which dominantly annihilates to light dark states such as with sub-GeV
mass. This model can address the recent GoGeNT annual modulation consistent
with other DM direct detection results and free of exclusions.Comment: References added and English greatly improve
Inspection of the detection cross section dependence of the Gallium Anomaly
We discuss in detail the dependence of the Gallium Anomaly on the detection
cross section. We provide updated values of the size of the Gallium Anomaly and
find that its significance is larger than about for all the detection
cross section models. We discuss the dependence of the Gallium Anomaly on the
assumed value of the half life of , which determines the
cross sections of the transitions from the ground state of
to the ground state of . We show that a value of the
half life which is larger than the standard one can reduce
or even solve the Gallium Anomaly. Considering the short-baseline neutrino
oscillation interpretation of the Gallium Anomaly, we show that a value of the
half life which is larger than the standard one can reduce
the tension with the results of other experiments. Since the standard value of
the half life was measured in 1985, we advocate the
importance of new measurements with modern technique and apparatus for a better
assessment of the Gallium Anomaly.Comment: v3: 11 pages, 4 figures, 3 tables, references added, typo correcte
Object Picture of Quasinormal Modes for Stringy Black Holes
We study the quasinormal modes (QNMs) for stringy black holes. By using
numerical calculation, the relations between the QNMs and the parameters of
black holes are minutely shown. For (1+1)-dimensional stringy black hole, the
real part of the quasinormal frequency increases and the imaginary part of the
quasinormal frequency decreases as the mass of the black hole increases.
Furthermore, the dependence of the QNMs on the charge of the black hole and the
flatness parameter is also illustrated. For (1+3)-dimensional stringy black
hole, increasing either the event horizon or the multipole index, the real part
of the quasinormal frequency decreases. The imaginary part of the quasinormal
frequency increases no matter whether the event horizon is increased or the
multipole index is decreased.Comment: 4 pages, 5 figure
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