Search results for "Observable"
showing 10 items of 634 documents
Tuning the Pseudospin Polarization of Graphene by a Pseudomagnetic Field.
2016
One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudo-magnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudo-magnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudo-magnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene's pseudospin due to a strain induced pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic field. We reveal this sublattice symmetry breaking by tunably straining grap…
On the distribution of education and democracy
2006
This paper empirically analyzes the influence of the distribution of education on democracy by controlling for unobservable heterogeneity and by taking into account the persistency of some of the variables. The most novel finding is that increase in the education attained by the majority of the population is what matters for the implementation and sustainability of democracy, rather than the average years of schooling. We show this result is robust to issues pertaining omitted variables, outliers, sample selection, or a narrow definition of the variables used to measure democracy.
Bag Scattering Theory
1986
We reanalyze the procedure used thus far for the study of collision processes in the Chiral Bag Model from the point of view of scattering theory. In the present formalism thein andout states are free waves with no memory of the cavity. This feature gives rise to an observable effect consisting in a peculiar momentum dependence of the scattering amplitudes, which differs from that of previous calculations. The new procedure however does not change the magnitude of the pion-baryon coupling constants.
Polarization of τ in quasielastic (anti)neutrino scattering: The role of spectral functions
2019
We present a study of the $\tau$ polarization in charged-current quasielastic (anti)neutrino-nucleus scattering. The spectral function formalism is used to compute the differential cross section and the polarization components for several kinematical setups, relevant for neutrino-oscillation experiments. The effects of the nuclear corrections in these observables are investigated by comparing the results obtained using two different realistic spectral functions, with those deduced from the relativistic global Fermi gas model, where only statistical correlations are accounted for. We show that the spectral functions, although they play an important role when predicting the differential cross…
The complete experiment for photoproduction of pseudoscalar mesons in a truncated partial wave analysis
2013
The complete experiment problem in the truncated partial wave analysis of pseudoscalar meson photoproduction with suppressed t-channel exchanges is investigated. The focus is set to ambiguities of the group S observables with the unpolarized differential cross section, $\sigma_0$, and the three single-spin observables, $\Sigma$, $T$ and $P$. For this purpose, the approach and formalism already worked out by Omelaenko in 1981 is revisited in this work. A numerical study using multipoles of the PWA solution MAID2007 shows how only one additional double polarization observable can resolve all ambiguities. Therefore, the possibility emerges to perform a complete experiment with only five observ…
Regge phenomenology in π0 and η photoproduction
2017
The $\ensuremath{\gamma}N\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}N$ and $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$-channel exchanges of vector ($\ensuremath{\rho}$ and $\ensuremath{\omega}$) and axial-vector (${b}_{1}$ and ${h}_{1}$) mesons. Moreover, Regge cuts of $\ensuremath{\rho}\mathbb{P},\phantom{\rule{0.28em}{0ex}}\ensuremath{\rho}{f}_{2},\phantom{\rule{0.28em}{0ex}}\ensuremath{\omega}\mathbb{P}$, and $\ensuremath{\omega}{f}_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies fr…
Relativistic Effects and the Role of Heavy Meson Exchange in Deuteron Photodisintegration
1997
Relativistic effects and the role of heavy meson exchange in deuteron photodisintegration are studied systematically for photon energies below the pion production threshold. In a (p/M)-expansion, all leading order relativistic one-body and pi-exchange as well as all static heavy meson exchange currents consistent with the Bonn OBEPQ model are included. In addition, one- and two-body boost effects have been investigated. Sizeable effects from the various two-body contributions beyond pi-exchange have been found in almost every observable considered, i.e., differential cross section and single polarization observables.
Hydraulic kinetics of the graft union in different Olea europaea L. scion/rootstock combinations
2007
The hydraulic resistance of young olive trees grafted on rootstocks with contrasting size-controlling potential was measured 30, 90, 360 and 480 days after grafting. Olive (Olea europaea L.) clones inducing plant vigorous growth (Leccino ‘Minerva’, LM) or dwarfing (Leccino ‘Dwarf’, LD) were studied in different scion/rootstock combinations (LD/LD, LD/LM, LM/LD, LM/LM). Plants growing on LD root systems developed lower leaf surface areas (about 50% less) than plants grafted on LM rootstocks. Graft union represented the largest fraction (up to 85%) of whole-plant hydraulic resistance 30 days after grafting, and still represented an important fraction of it 2 months later (40–55%). Four-hundre…
Explanation of Notation
1991
For the presentation of all 288 polarization observables in the next section we have adopted the following scheme. Each observable is a function of the angle and the photon energy. With respect to the latter we have chosen five energies, namely 4.5 MeV, the maximum of the total cross section, 20 MeV, 60 MeV, 100 MeV, and 140 MeV. For each observable and for each of these energies we have studied the following topics: (i) The influence of meson exchange currents (MEC), isobar configurations (IC) and relativistic corrections (RC). Since the various potential models give qualitatively very similar results, we use in this case the r-space version of the Bonn model (OBEPR). (ii) The contribution…
Inferring rheology and geometry of subsurface structures by adjoint-based inversion of principal stress directions
2020
SUMMARY Imaging subsurface structures, such as salt domes, magma reservoirs or subducting plates, is a major challenge in geophysics. Seismic imaging methods are, so far, the most precise methods to open a window into the Earth. However, the methods may not yield the exact depth or size of the imaged feature and may become distorted by phenomena such as seismic anisotropy, fluid flow, or compositional variations. A useful complementary method is therefore to simulate the mechanical behaviour of rocks on large timescales, and compare model predictions with observations. Recent studies have used the (non-linear) Stokes equations and geometries from seismic studies in combination with an adjoi…