31,850 research outputs found
RISK MANAGEMENT FOR LIVESTOCK PRODUCERS: HEDGING AND CONTRACT PRODUCTION
Livestock Production/Industries, Risk and Uncertainty,
Evidence for the Multiverse in the Standard Model and Beyond
In any theory it is unnatural if the observed parameters lie very close to
special values that determine the existence of complex structures necessary for
observers. A naturalness probability, P, is introduced to numerically evaluate
the unnaturalness. If P is small in all known theories, there is an observer
naturalness problem. In addition to the well-known case of the cosmological
constant, we argue that nuclear stability and electroweak symmetry breaking
(EWSB) represent significant observer naturalness problems. The naturalness
probability associated with nuclear stability is conservatively estimated as
P_nuc < 10^{-(3-2)}, and for simple EWSB theories P_EWSB < 10^{-(2-1)}. This
pattern of unnaturalness in three different arenas, cosmology, nuclear physics,
and EWSB, provides evidence for the multiverse. In the nuclear case the problem
is largely solved even with a flat multiverse distribution, and with nontrivial
distributions it is possible to understand both the proximity to neutron
stability and the values of m_e and m_d - m_u in terms of the electromagnetic
contribution to the proton mass. It is reasonable that multiverse distributions
are strong functions of Lagrangian parameters due to their dependence on
various factors. In any EWSB theory, strongly varying distributions typically
lead to a little or large hierarchy, and in certain multiverses the size of the
little hierarchy is enhanced by a loop factor. Since the correct theory of EWSB
is unknown, our estimate for P_EWSB is theoretical. The LHC will determine
P_EWSB more robustly, which may remove or strengthen the observer naturalness
problem of EWSB. For each of the three arenas, the discovery of a natural
theory would eliminate the evidence for the multiverse; but in the absence of
such a theory, the multiverse provides a provisional understanding of the data.Comment: 79 pages, 23 figure
A Program of Photometric Measurements of Solar Irradiance Fluctuations from Ground-based Observations
Photometric observations of the sun have been carried out at the San Fernando Observatory since early 1985. Since 1986, observations have been obtained at two wavelengths in order to separately measure the contributions of sunspots and bright facular to solar irradiance variations. Researchers believe that the contributions of sunspots can be measured to an accuracy of about plus or minus 30 ppm. The effect of faculae is much less certain, with uncertainties in the range of plus or minus 300 ppm. The larger uncertainty for faculae reflects both the greater difficulty in measuring the facular area, due to their lower contrast compared to sunspots, and the greater uncertainty in their contrast variation with viewing angle on the solar disk. Recent results from two separate photometric telescopes will be compared with bolometric observations from the active cavity radiometer irradiance monitor (ACRIM) that was on board the Solar Max satellite
Origin of the fast magnetization tunneling in the single-molecule magnet [Ni(hmp)(tBuEtOH)Cl]4
We present high-frequency angle-dependent EPR data for crystals of
[NixZn1-x(hmp)(t-BuEtOH)Cl]4 (x = 1 and 0.02). The x = 1 complex behaves as a
single-molecule magnet at low temperatures, displaying hysteresis and
exceptionally fast magnetization tunneling. We show that this behavior is
related to a 4th-order transverse crystal-field interaction, which produces a
significant tunnel-splitting (~10 MHz) of the ground state of this S = 4
system. The magnitude of the 4th-order anisotropy, and the dominant axial term
(D), can be related to the single-ion interactions (Di and Ei) at the
individual NiII sites, as determined for the x = 0.02 crystals.Comment: 11 pages including 2 figure
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