1,199 research outputs found
Electrons and Positrons in Cosmic Rays
This review concentrates on the results obtained, over the last ten years, on
the astrophysics of high-energy cosmic ray electrons and positrons. The
anomalies, observed in the data of recent experiments (possible bump in the
electron spectrum and the PAMELA anomaly in the positron fraction) are
discussed through the systematic use of simple analytical solutions of the
transport equations for cosmic ray electrons. Three main ways of explaining the
origin of the anomalies are considered: the conservative way supposing the
positrons to be pure secondary particles; the nearby sources like pulsars
origin; and the dark matter origin. This review discusses, also, the inability
to select the pulsars model or the dark matter model to explain the electron
anomalies on the basis of the electron spectra with the usual large energy
binning (). It is argued that the signature of nearby pulsars
origin of the anomalies against the dark matter origin could be the fine
structure of the cosmic ray electron spectrum predicted in the Malyshev et al.
paper (2009) and which was observed in the data from the high-resolution ATIC
experiment (2009-2011). To date, the high-resolution ATIC data was the only
experimental result of this type published in the literature. Therefore, they
should be tested by other experiments as soon as possible. Generally, there is,
also, rather controversial situations between the data of the majority of
recent experiments and, consequently, there is a noted urgent need for new
high-precision and high-statistical experiments.Comment: LaTeX2e, 27 pages, 28 figures, invited paper for 23rd European Cosmic
Ray Symposium (2012
Total Quantum Zeno Effect beyond Zeno Time
In this work we show that is possible to obtain Total Quantum Zeno Effect in
an unstable systems for times larger than the correlation time of the bath. The
effect is observed for some particular systems in which one can chose
appropriate observables which frequent measurements freeze the system into the
initial state. For a two level system in a squeezed bath one can show that
there are two bath dependent observables displaying Total Zeno Effect when the
system is initialized in some particular states. We show also that these states
are intelligent states of two conjugate observables associated to the
electromagnetic fluctuations of the bath.Comment: 6 pages, 3 figures, Contributed to Quantum Optics III, Pucon, Chile,
November 200
Superconductivity in model cuprate as an S=1 pseudomagnon condensation
We make use of the S=1 pseudospin formalism to describe the charge degree of
freedom in a model high- cuprate with the on-site Hilbert space reduced to
the three effective valence centers, nominally Cu. Starting
with a parent cuprate as an analogue of the quantum paramagnet ground state and
using the Schwinger boson technique we found the pseudospin spectrum and
conditions for the pseudomagnon condensation with phase transition to a
superconducting state.Comment: Version to be published in JLT
- …