27,118 research outputs found
Low-energy neutrino physics and neutrino mass
Among the principal concerns in neutrino physics today are the questions of whether neutrinos are massive and, if so, whether the neutrinos emitted in a weak decay are pure or mixed quantum states. The concept of mixed neutrinos has been with us for more than 20 years, having first been introduced by Maki et al (1) and by Pontecorvo (2) following demonstration in 1962 that more than one type (flavor) of neutrino existed. After having been dormant for some time, the interest in these issues was reborn in recent years with the advent of grand unified theories, which predict nonvanishing neutrino mass and which can accommodate eutrino mixing, in a natural way. Controversial experiments also refueled the excitment (and consternation) of researchers in this endeavor
Structural Quantification of Entanglement
We introduce an approach which allows a detailed structural and quantitative
analysis of multipartite entanglement. The sets of states with different
structures are convex and nested. Hence, they can be distinguished from each
other using appropriate measurable witnesses. We derive equations for the
construction of optimal witnesses and discuss general properties arising from
our approach. As an example, we formulate witnesses for a 4-cluster state and
perform a full quantitative analysis of the entanglement structure in the
presence of noise and losses. The strength of the method in multimode
continuous variable systems is also demonstrated by considering a dephased
GHZ-type state.Comment: 12 pages, 1 table and 3 figure
High electrical resistivity carbon/graphite fibers
Carbon/graphite fibers were chemically oxidized in the liquid phase to fibers of graphite oxide. Resistivity increases as high as 10,000 times were obtained, the oxidized fiber decomposed on exposure to atmosphere. A factor of 1,000 remained as a stable increment. The largest change observed was 1,000,000 times. Best results were obtained on the most highly graphitized fibers. Electrochemical oxidation yielded a lower increase--about 10 times, but provided a controllable method of synthesis and insight to the mechanism of reaction. Tensile tests indicated that the strength of the fiber on oxidation was decreased by no more than 25 percent
Uncertainty in the 0νββ decay nuclear matrix elements
The nuclear matrix elements M0nu of the neutrinoless double-beta decay (0nubetabeta) are evaluated for 76Ge,100Mo,130Te, and 136Xe within the renormalized quasiparticle random phase approximation (RQRPA) and the simple QRPA. Three sets of single particle level schemes are used, ranging in size from 9 to 23 orbits. When the strength of the particle-particle interaction is adjusted so that the 2nubetabeta decay rate is correctly reproduced, the resulting M0nu values become essentially independent of the size of the basis, and of the form of different realistic nucleon-nucleon potentials. Thus, one of the main reasons for variability of the calculated M0nu within these methods is eliminated
Electromagnetic field quantization in a linear polarizable and magnetizable medium
By modeling a linear polarizable and magnetizable medium (magneto-dielectric)
with two quantum fields, namely E and M, electromagnetic field is quantized in
such a medium consistently and systematically. A Hamiltonian is proposed from
which, using the Heisenberg equations, Maxwell and constitutive equations of
the medium are obtained. For a homogeneous medium, the equation of motion of
the quantum vector potential, , is derived and solved analytically.
Two coupling functions which describe the electromagnetic properties of the
medium are introduced. Four examples are considered showing the features and
the applicability of the model to both absorptive and nonabsorptive
magneto-dielectrics.Comment: 23 pages, Accepted for publication in Phy.Rev
Reactor antineutrino spectra and their application to antineutrino-induced reactions. II
The antineutrino and electron spectra associated with various nuclear fuels are calculated. While there are substantial differences between the spectra of different uranium and plutonium isotopes, the dependence on the energy and flux of the fission-inducing neutrons is very weak. The resulting spectra can be used for the calculation of the antineutrino and electron spectra of an arbitrary nuclear reactor at various stages of its refueling cycle. The sources of uncertainties in the spectrum are identified and analyzed in detail. The exposure time dependence of the spectrum is also discussed. The averaged cross sections of the inverse neutron β decay, weak charged and neutral-current-induced deuteron disintegration, and the antineutrino-electron scattering are then evaluated using the resulting ν̅_e spectra.
[RADIOACTIVITY, FISSION 235U, 238U, (^239)Pu, (^240)Pu, (^241)Pu, antineutrino and electron spectra calculated. σ for ν̅ induced reactions analyzed.
Influence of the Ground-State Topology on the Domain-Wall Energy in the Edwards-Anderson +/- J Spin Glass Model
We study the phase stability of the Edwards-Anderson spin-glass model by
analyzing the domain-wall energy. For the bimodal distribution of bonds, a
topological analysis of the ground state allows us to separate the system into
two regions: the backbone and its environment. We find that the distributions
of domain-wall energies are very different in these two regions for the three
dimensional (3D) case. Although the backbone turns out to have a very high
phase stability, the combined effect of these excitations and correlations
produces the low global stability displayed by the system as a whole. On the
other hand, in two dimensions (2D) we find that the surface of the excitations
avoids the backbone. Our results confirm that a narrow connection exists
between the phase stability of the system and the internal structure of the
ground-state. In addition, for both 3D and 2D we are able to obtain the fractal
dimension of the domain wall by direct means.Comment: 4 pages, 3 figures. Accepted for publication in Rapid Communications
of Phys. Rev.
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