8,288 research outputs found
Addressing \mu-b_\mu and proton lifetime problems and active neutrino masses in a U(1)^\prime-extended supergravity model
We present a locally supersymmetric extension of the minimal supersymmetric
Standard Model (MSSM) based on the gauge group where, except for the supersymmetry breaking scale
which is fixed to be GeV, we require that all non-Standard-Model
parameters allowed by the {\it local} spacetime and gauge symmetries assume
their natural values. The symmetry, which is spontaneously broken
at the intermediate scale, serves to ({\it i}) explain the weak scale
magnitudes of and terms, ({\it ii}) ensure that dimension-3 and
dimension-4 baryon-number-violating superpotential operators are forbidden,
solving the proton-lifetime problem, ({\it iii}) predict {\it bilinear lepton
number violation} in the superpotential at just the right level to accommodate
the observed mass and mixing pattern of active neutrinos (leading to a novel
connection between the SUSY breaking scale and neutrino masses), while
corresponding trilinear operators are strongly supppressed. The phenomenology
is like that of the MSSM with bilinear R-parity violation, were the would-be
lightest supersymmetric particle decays leptonically with a lifetime of s. Theoretical consistency of our model requires the
existence of multi-TeV, stable, colour-triplet, weak-isosinglet scalars or
fermions, with either conventional or exotic electric charge which should be
readily detectable if they are within the kinematic reach of a hadron collider.
Null results of searches for heavy exotic isotopes implies that the re-heating
temperature of our Universe must have been below their mass scale which, in
turn, suggests that sphalerons play a key role for baryogensis. Finally, the
dark matter cannot be the weakly interacting neutralino.Comment: 33 pages, 2 figures, Discussion on proton decay and radiative
neutrino masses augmented, and references adde
Journal Staff
The aluminum–zinc-vacancy (Al Zn −V Zn ) complex is identified as one of the dominant defects in Al-containing n -type ZnO after electron irradiation at room temperature with energies above 0.8 MeV. The complex is energetically favorable over the isolated V Zn , binding more than 90% of the stable V Zn ’s generated by the irradiation. It acts as a deep acceptor with the (0/− ) energy level located at approximately 1 eV above the valence band. Such a complex is concluded to be a defect of crucial and general importance that limits the n -type doping efficiency by complex formation with donors, thereby literally removing the donors, as well as by charge compensation
Quantum theory of successive projective measurements
We show that a quantum state may be represented as the sum of a joint
probability and a complex quantum modification term. The joint probability and
the modification term can both be observed in successive projective
measurements. The complex modification term is a measure of measurement
disturbance. A selective phase rotation is needed to obtain the imaginary part.
This leads to a complex quasiprobability, the Kirkwood distribution. We show
that the Kirkwood distribution contains full information about the state if the
two observables are maximal and complementary. The Kirkwood distribution gives
a new picture of state reduction. In a nonselective measurement, the
modification term vanishes. A selective measurement leads to a quantum state as
a nonnegative conditional probability. We demonstrate the special significance
of the Schwinger basis.Comment: 6 page
Synchronization and Coarsening (without SOC) in a Forest-Fire Model
We study the long-time dynamics of a forest-fire model with deterministic
tree growth and instantaneous burning of entire forests by stochastic lightning
strikes. Asymptotically the system organizes into a coarsening self-similar
mosaic of synchronized patches within which trees regrow and burn
simultaneously. We show that the average patch length grows linearly with
time as t-->oo. The number density of patches of length L, N(L,t), scales as
^{-2}M(L/), and within a mean-field rate equation description we find
that this scaling function decays as e^{-1/x} for x-->0, and as e^{-x} for
x-->oo. In one dimension, we develop an event-driven cluster algorithm to study
the asymptotic behavior of large systems. Our numerical results are consistent
with mean-field predictions for patch coarsening.Comment: 5 pages, 4 figures, 2-column revtex format. To be submitted to PR
Anisotropic thermal expansion and magnetostriction of YNiBC single crystals
We present results of anisotropic thermal expansion and low temperature
magnetostriction measurements on YNiBC single crystals grown by high
temperature flux and floating zone techniques. Quantum oscillations of
magnetostriction were observed at low temperatures for starting at
fields significantly below (). Large irreversible,
longitudinal magnetostriction was seen in both, in-plane and along the c-axis,
directions of the applied magnetic field in the intermediate superconducting
state. Anisotropic uniaxial pressure dependencies of were evaluated using
results of zero field, thermal expansion measurements
Classification of Possible Finite-Time Singularities by Functional Renormalization
Starting from a representation of the early time evolution of a dynamical
system in terms of the polynomial expression of some observable f (t) as a
function of the time variable in some interval 0 < t < T, we investigate how to
extrapolate/forecast in some optimal stability sense the future evolution of
f(t) for time t>T. Using the functional renormalization of Yukalov and Gluzman,
we offer a general classification of the possible regimes that can be defined
based on the sole knowledge of the coefficients of a second-order polynomial
representation of the dynamics. In particular, we investigate the conditions
for the occurence of finite-time singularities from the structure of the time
series, and quantify the critical time and the functional nature of the
singularity when present. We also describe the regimes when a smooth extremum
replaces the singularity and determine its position and amplitude. This extends
previous works by (1) quantifying the stability of the functional
renormalization method more accurately, (2) introducing new global constraints
in terms of moments and (3) going beyond the ``mean-field'' approximation.Comment: Latex document of 18 pages + 7 ps figure
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