1,345 research outputs found
The Puzzling Frequencies of CEMP and NEMP Stars
We present the results of binary population simulations of carbon- and
nitrogen-enhanced metal-poor (CEMP and NEMP) stars. We show that the observed
paucity of very nitrogen-rich stars puts strong constraints on possible
modifications of the initial mass function at low metallicity.Comment: 3 pages, contribution to "The Origin of the Elements Heavier than
Iron" in honor of the 70th birthday of Roberto Gallino, Torino, Italy,
September 200
A Novel Protocol-Authentication Algorithm Ruling Out a Man-in-the-Middle Attack in Quantum Cryptography
In this work we review the security vulnerability of Quantum Cryptography
with respect to "man-in-the-middle attacks" and the standard authentication
methods applied to counteract these attacks. We further propose a modified
authentication algorithm which features higher efficiency with respect to
consumption of mutual secret bits.Comment: 4 pages, submitted to the International Journal of Quantum
Information, Proceedings of the meeting "Foundations of Quantum Information",
Camerino, April 200
Practical Quantum Key Distribution with Polarization-Entangled Photons
We present an entangled-state quantum cryptography system that operated for
the first time in a real world application scenario. The full key generation
protocol was performed in real time between two distributed embedded hardware
devices, which were connected by 1.45 km of optical fiber, installed for this
experiment in the Vienna sewage system. The generated quantum key was
immediately handed over and used by a secure communication application.Comment: 5 pages, 3 figure
Aperiodic quantum oscillations of particle-hole asymmetric Dirac cones
We report experimental measurements and theoretical analysis of Shubnikov-de
Haas (SdH) oscillations in a Dirac cone system: the a-(BEDT-TTF)2I3 organic
metal under hydrostatic pressure. The measured SdH oscillations reveal
anomalies at high magnetic fields B where the 1/B oscillations periodicity is
lost above 7 T. We interpret these unusual results within a theoretical model
that takes into account intrinsic distortions of the a-(BEDT-TTF)2I3 Dirac
cones such as a parabolic particle-hole asymmetric correction. Others possible
causes, such as a cone tilting or a Zeeman effect, are carefully ruled out. The
observations are consistent among a-(BEDT-TTF)2I3 samples with different Fermi
levels
Development of Large Volume Neutron Detector
開始ページ、終了ページ: 冊子体のページ付
Decoherence, fluctuations and Wigner function in neutron optics
We analyze the coherence properties of neutron wave packets, after they have
interacted with a phase shifter undergoing different kinds of statistical
fluctuations. We give a quantitative (and operational) definition of
decoherence and compare it to the standard deviation of the distribution of the
phase shifts. We find that in some cases the neutron ensemble is more coherent,
even though it has interacted with a wider (i.e. more disordered) distribution
of shifts. This feature is independent of the particular definition of
decoherence: this is shown by proposing and discussing an alternative
definition, based on the Wigner function, that displays a similar behavior. We
briefly discuss the notion of entropy of the shifts and find that, in general,
it does not correspond to that of decoherence of the neutron.Comment: 18 pages, 7 figure
Evolution of Low-Mass Population III Stars
We present the evolutionary models of metal-free stars in the mass range from
0.8 to 1.2 Msun with up-to-date input physics. The evolution is followed to the
onset of hydrogen mixing into a convection, driven by the helium flash at red
giant or asymptotic giant branch phase.
The models of mass M >= 0.9 Msun undergo the central hydrogen flash,
triggered by the carbon production due to the 3-alpha reactions.
We find that the border of the off-center and central ignition of helium core
flash falls between 1.1 and 1.2 Msun; the models of mass M <= 1.1 Msun
experience the hydrogen mixing at the tip of red giant branch while the models
of M = 1.2 Msun during the helium shell flashes on the asymptotic giant branch.
The equation of state for the Coulomb liquid region, where electron
conduction and radiation compete, is shown to be important since it affects the
thermal state in the helium core and influences the red giant branch evolution.
It is also found that the non-resonant term of 3-alpha reactios plays an
important role, although it has negligible effect in the evolution of stars of
younger populations.
We compare our models with the computations by several other sets of authors,
to confirm the good agreement except for one study which finds the helium
ignition much closer to the center with consequences important for subsequent
evolution.Comment: 23 pages, 6 figures, 2 tables, accepted for Ap
Recommended from our members
Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016.
[This corrects the article DOI: 10.1186/s13054-016-1208-6.]
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