15,852 research outputs found
Hidden assumptions in the derivation of the Theorem of Bell
John Bell's inequalities have already been considered by Boole in 1862. Boole
established a one-to-one correspondence between experimental outcomes and
mathematical abstractions of his probability theory. His abstractions are
two-valued functions that permit the logical operations AND, OR and NOT and are
the elements of an algebra. Violation of the inequalities indicated to Boole an
inconsistency of definition of the abstractions and/or the necessity to revise
the algebra. It is demonstrated in this paper, that a violation of Bell's
inequality by Einstein-Podolsky-Rosen type of experiments can be explained by
Boole's ideas. Violations of Bell's inequality also call for a revision of the
mathematical abstractions and corresponding algebra. It will be shown that this
particular view of Bell's inequalities points toward an incompleteness of
quantum mechanics, rather than to any superluminal propagation or influences at
a distance
KAT-7 Science Verification: Using HI Observations of NGC 3109 to Understand its Kinematics and Mass Distribution
HI observations of the Magellanic-type spiral NGC 3109, obtained with the
seven dish Karoo Array Telescope (KAT-7), are used to analyze its mass
distribution. Our results are compared to what is obtained using VLA data.
KAT-7 is the precursor of the SKA pathfinder MeerKAT, which is under
construction. The short baselines and low system temperature of the telescope
make it sensitive to large scale low surface brightness emission. The new
observations with KAT-7 allow the measurement of the rotation curve of NGC 3109
out to 32', doubling the angular extent of existing measurements. A total HI
mass of 4.6 x 10^8 Msol is derived, 40% more than what was detected by the VLA
observations.
The observationally motivated pseudo-isothermal dark matter (DM) halo model
can reproduce very well the observed rotation curve but the cosmologically
motivated NFW DM model gives a much poorer fit to the data. While having a more
accurate gas distribution has reduced the discrepancy between the observed RC
and the MOdified Newtonian Dynamics (MOND) models, this is done at the expense
of having to use unrealistic mass-to-light ratios for the stellar disk and/or
very large values for the MOND universal constant a0. Different distances or HI
contents cannot reconcile MOND with the observed kinematics, in view of the
small errors on those two quantities. As for many slowly rotating gas-rich
galaxies studied recently, the present result for NGC 3109 continues to pose a
serious challenge to the MOND theory.Comment: 25 pages, 20 figures, accepted for publication in Astronomical
Journa
Preventing sexual violence in New Mexico: what our communities have to say.
Presented at: 2015 Annual Conference of the New Mexico Public Health Association; March 31-April 1, 2015; Albuquerque, NM.https://digitalrepository.unm.edu/prc-posters-presentations/1036/thumbnail.jp
Modelling the role of consideration of alternatives in mode choice: An application on the Rome-Milan corridor
In this paper, we investigate the role consideration of the alternatives plays in mode choice models. On the Rome-Milan corridor, in Italy, where seven alternative modes of transport are available, we administered a stated choice (SC) experiment. Responses to supplementary questions on consideration of the different modes of transport and the presence of thresholds for the travel time attribute indicate travellers are less likely to consider the slower modes. Two model specifications, in which consideration for the slower alternatives is measured using both sets of supplementary questions, are proposed and contrasted against a model which assumes all alternatives are considered. Our results suggests that some of the unobserved preference heterogeneity could potentially be due to consideration effects. Accounting for consideration of alternatives also has direct impacts on choice probabilities, parameter estimates and willingness-to-pay measures
Testing the stability of utility parameters in repeated best, repeated best-worst and one-off best-worst studies
Stated choice (SC) surveys are a key tool for studying travel behaviour and are used to inform policy decisions in many countries. Recently, the best-worst (BW) variant of SC has rapidly increased in popularity in fields as diverse as transport, marketing and health research. A key argument for its implementation has been that it is perceived to be easier for respondents to identify the best and the worst alternative in a choice set compared to identifying the second- or even third best. For elicitation formats asking respondents to consecutively identify the first, second and third best (etc.) alternative, labelled here as repeated best stages, it is well known that utility and scale parameters are generally not stable across the stages. Joint analysis of the responses to each stage may increase the efficiency of the utility and willingness-to-pay parameters (i.e. smaller standard errors), but incorrect inferences may be made if these parameters are not stable across the stages. This paper tests the stability of utility parameters for the repeated BW and one-off BW format. Using data from three different studies, we show that, regardless of the dataset and elicitation format used, the obtained utility parameters and willingness to pay estimates are not stable across stages. The results thereby question the use of BW data in applied work aimed at forecasting and understanding first (best) choices. Our findings thereby contradict recent discussions about potentially beneficial framing effects in BW surveys. The unique presence of corresponding data from a repeated best and repeated BW exercise in one survey highlights the observed rank-orders are highly consistent across the two elicitation formats and that any differences in marginal willingness to pay estimates can be attributed to the imposed econometric model rather than to differences in the behaviour of respondents
A Solvable Model for Many Quark Systems in QCD Hamiltonians
Motivated by a canonical, QCD Hamiltonian we propose an effective Hamiltonian
to represent an arbitrary number of quarks in hadronic bags. The structure of
the effective Hamiltonian is discussed and the BCS-type solutions that may
represent constituent quarks are presented. The single particle orbitals are
chosen as 3-dimensional harmonic oscillators and we discuss a class of exact
solutions that can be obtained when a subset of single-particle basis states is
restricted to include a certain number of orbital excitations. The general
problem, which includes all possible orbital states, can also be solved by
combining analytical and numerical methods.Comment: 24 pages, 2 figures, research articl
Decision uncertainty in multi-attribute stated preference studies
Econometric modelling of decision uncertainty has received extensive attention in the contingent valuation literature, but these methods are not directly transferable to the realm of multi-attribute stated preference studies. In this paper, an integrated choice and latent variable model tracing the impact of decision uncertainty on the valuation of flood risks reductions in the Netherlands is developed. The proposed model structure is not subject to the potential endogeneity bias and measurement error issues associated with most applied methods. The driving factors of decision uncertainty are identified through stated choices and a set of self-reported decision uncertainty follow-up questions. The model simultaneously accounts for the impact of decision uncertainty on individual choices and welfare estimates. In the presented case study, uncertain respondents are found to make more random choices and select the opt out option more often. Willingness-to-pay for flood risk reductions increases after accounting for these behavioural responses to decision uncertainty
Spectral Properties of Magnetic Excitations in Cuprate Two-Leg Ladder Systems
This article summarizes and extends the recent developments in the
microscopic modeling of the magnetic excitations in cuprate two-leg ladder
systems. The microscopic Hamiltonian comprises dominant Heisenberg exchange
terms plus an additional four-spin interaction which is about five times
smaller. We give an overview over the relevant energies like the one-triplon
dispersion, the energies of two-triplon bound states and the positions of
multi-triplon continua and over relevant spectral properties like spectral
weights and spectral densities in the parameter regime appropriate for cuprate
systems. It is concluded that an almost complete understanding of the magnetic
excitations in undoped cuprate ladders has been obtained as measured by
inelastic neutron scattering, inelastic light (Raman) scattering and infrared
absorption.Comment: 26 pages, 10 figures, review for Mod. Phys. Lett.
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