347 research outputs found
Expansive homeomorphisms of the plane
This article tackles the problem of the classification of expansive
homeomorphisms of the plane. Necessary and sufficient conditions for a
homeomorphism to be conjugate to a linear hyperbolic automorphism will be
presented. The techniques involve topological and metric aspects of the plane.
The use of a Lyapunov metric function which defines the same topology as the
one induced by the usual metric but that, in general, is not equivalent to it
is an example of such techniques. The discovery of a hypothesis about the
behavior of Lyapunov functions at infinity allows us to generalize some results
that are valid in the compact context. Additional local properties allow us to
obtain another classification theorem.Comment: 29 pages, 22 figure
On two-dimensional surface attractors and repellers on 3-manifolds
We show that if is an -diffeomorphism with a surface
two-dimensional attractor or repeller and is a
supporting surface for , then and
there is such that: 1) is a union
of disjoint tame surfaces such that every is
homeomorphic to the 2-torus . 2) the restriction of to
is conjugate to Anosov automorphism of
Search for solar axions in XMASS, a large liquid-xenon detector
XMASS, a low-background, large liquid-xenon detector, was used to search for
solar axions that would be produced by bremsstrahlung and Compton effects in
the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent
limit on the coupling for mass 1keV is
(90% C.L.), which is a factor of two stronger than the existing experimental
limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are
1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced
the most stringent limit, which is better than that previously derived from
astrophysical arguments regarding the Sun to date
Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I
We have searched for exotic neutrino-electron interactions that could be
produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark
photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed
no significant signals in 711 days of data. We obtain an upper limit for
neutrino millicharge of 5.410 at 90\% confidence level
assuming all three species of neutrino have common millicharge. We also set
flavor dependent limits assuming the respective neutrino flavor is the only one
carrying a millicharge, for , for , and for .
These limits are the most stringent yet obtained from direct measurements. We
also obtain an upper limit for the neutrino magnetic moment of
1.810 Bohr magnetons. In addition, we obtain upper limits for
the coupling constant of dark photons in the model of
1.310 if the dark photon mass is 1 MeV,
and 8.810 if it is 10 MeV
Scintillation-only Based Pulse Shape Discrimination for Nuclear and Electron Recoils in Liquid Xenon
In a dedicated test setup at the Kamioka Observatory we studied pulse shape
discrimination (PSD) in liquid xenon (LXe) for dark matter searches. PSD in LXe
was based on the observation that scintillation light from electron events was
emitted over a longer period of time than that of nuclear recoil events, and
our method used a simple ratio of early to total scintillation light emission
in a single scintillation event. Requiring an efficiency of 50% for nuclear
recoil retention we reduced the electron background to 7.7\pm1.1(stat)\pm1.2
0.6(sys)\times10-2 at energies between 4.8 and 7.2 keVee and to
7.7\pm2.8(stat)\pm2.5 2.8(sys)\times10-3 at energies between 9.6 and 12 keVee
for a scintillation light yield of 20.9 p.e./keV. Further study was done by
masking some of that light to reduce this yield to 4.6 p.e./keV, the same
method results in an electron event reduction of 2.4\pm0.2(stat)\pm0.3
0.2(sys)\times10-1 for the lower of the energy regions above. We also observe
that in contrast to nuclear recoils the fluctuations in our early to total
ratio for electron events are larger than expected from statistical
fluctuations.Comment: 25 pages, 15 figure
- …