309 research outputs found
Invariance of generalized wordlength patterns
The generalized wordlength pattern (GWLP) introduced by Xu and Wu (2001) for
an arbitrary fractional factorial design allows one to extend the use of the
minimum aberration criterion to such designs. Ai and Zhang (2004) defined the
-characteristics of a design and showed that they uniquely determine the
design. While both the GWLP and the -characteristics require indexing the
levels of each factor by a cyclic group, we see that the definitions carry over
with appropriate changes if instead one uses an arbitrary abelian group. This
means that the original definitions rest on an arbitrary choice of group
structure. We show that the GWLP of a design is independent of this choice, but
that the -characteristics are not. We briefly discuss some implications of
these results.Comment: To appear in: Journal of Statistical Planning and Inferenc
Generalized wordlength patterns and strength
Xu and Wu (2001) defined the \emph{generalized wordlength pattern} of an arbitrary fractional factorial design (or orthogonal array) on
factors. They gave a coding-theoretic proof of the property that the design
has strength if and only if . The quantities are
defined in terms of characters of cyclic groups, and so one might seek a direct
character-theoretic proof of this result. We give such a proof, in which the
specific group structure (such as cyclicity) plays essentially no role.
Nonabelian groups can be used if the counting function of the design satisfies
one assumption, as illustrated by a couple of examples
On the pion electroproduction amplitude
We analyze amplitudes for the pion electroproduction on proton derived from
Lagrangians based on the local chiral SU(2) x SU(2) symmetries. We show that
such amplitudes do contain information on the nucleon axial form factor F_A in
both soft and hard pion regimes. This result invalidates recent Haberzettl's
claim that the pion electroproduction at threshold cannot be used to extract
any information regarding F_A.Comment: 14 pages, 6 figures, revised version, accepted for publication in
Phys. Rev.
Polarized photons in radiative muon capture
We discuss the measurement of polarized photons arising from radiative muon
capture. The spectrum of left circularly polarized photons or equivalently the
circular polarization of the photons emitted in radiative muon capture on
hydrogen is quite sensitive to the strength of the induced pseudoscalar
coupling constant . A measurement of either of these quantities, although
very difficult, might be sufficient to resolve the present puzzle resulting
from the disagreement between the theoretical prediction for and the
results of a recent experiment. This sensitivity results from the absence of
left-handed radiation from the muon line and from the fact that the leading
parts of the radiation from the hadronic lines, as determined from the chiral
power counting rules of heavy-baryon chiral perturbation theory, all contain
pion poles.Comment: 10 pages, 6 figure
Observation of double radiative capture on pionic hydrogen
We report the first observation of double radiative capture on pionic
hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC
spectrometer, and detected --ray coincidences following stops
in liquid hydrogen. We found the branching ratio for double radiative capture
to be . The measured
branching ratio and angle-energy distributions support the theoretical
prediction of a dominant contribution from the
annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let
Capture rate and neutron helicity asymmetry for ordinary muon capture on hydrogen
Applying heavy-baryon chiral perturbation theory to ordinary muon capture
(OMC) on a proton, we calculate the capture rate and neutron helicity asymmetry
up to next-to-next-to-leading order. For the singlet hyperfine state, we obtain
the capture rate Gamma_0 = 695 sec^{-1} while, for the triplet hyperfine state,
we obtain the capture rate Gamma_1 = 11.9 sec^{-1} and the neutron asymmetry
alpha_1 = 0.93. If the existing formalism is used to relate these atomic
capture rates to Gamma_{liq}, the OMC rate in liquid hydrogen, then Gamma_{liq}
corresponding to our improved values of Gamma_0 and Gamma_1 is found to be
significantly larger than the experimental value, primarily due to the updated
larger value of g_A. We argue that this apparent difficulity may be correlated
to the specious anomaly recently reported for mu^- + p to n + nu_mu + gamma,
and we suggest a possibility to remove these two "problems" simply and
simultaneously by reexamining the molecular physics input that underlies the
conventional analysis of Gamma_{liq}.Comment: 14 pages, 1 figur
Social Movements and the Globalisation of Environmental Governance
Summary Environmental governance has become globalised as part of a wider agenda of global governance building within key institutions such as the World Trade Organisation (WTO). The perceived need for global solutions to global environmental problems and calls for sustainable development have put environmental issues onto the agenda of the institutions of global governance, which, some argue, are becoming democratised through consultation with global civil society. This sphere of global civil society, however, is not unproblematic, hosting a diversity of actors such as social movements, business and industry who are clearly not on an equal footing. This article focuses on social movements attempts to influence the international trade agenda, but also takes a look at radical grassroots resistance movements that do not fit easily within this sphere. Their calls for structural transformation of the WTO highlight the lack of democracy and accountability within the WTO that will not be remedied merely through consultation with global civil society
Muon capture by a proton in heavy baryon chiral perturbation theory
The matrix element for muon capture by a proton is calculated to O(p^3)
within heavy baryon chiral perturbation theory using the new O(p^3) Lagrangian
of Ecker and Mojzis. External nucleon fields are renormalized using the
appropriate definition of the wave function renormalization factor Z_N. Our
expression for Z_N differs somewhat from that found in existing literature, but
is the one which is consistent with the Lagrangian we use and the one which
ensures, within our approach, the nonrenormalization of the vector coupling as
required by the conserved vector current. Expressions for the standard muon
capture form factors are derived and compared to experimental data and we
determine three of the coefficients of the Ecker - Mojzis Lagrangian, namely,
b_7, b_{19}, and b_{23}.Comment: 14 pages, LaTeX, using revte
- …