4,295 research outputs found
Non-linear clustering during the BEC dark matter phase transition
Spherical collapse of the Bose-Einstein Condensate (BEC) dark matter model is
studied in the Thomas Fermi approximation. The evolution of the overdensity of
the collapsed region and its expansion rate are calculated for two scenarios.
We consider the case of a sharp phase transition (which happens when the
critical temperature is reached) from the normal dark matter state to the
condensate one and the case of a smooth first order phase transition where
there is a continuous conversion of "normal" dark matter to the BEC phase. We
present numerical results for the physics of the collapse for a wide range of
the model's space parameter, i.e. the mass of the scalar particle
and the scattering length . We show the dependence of the transition
redshift on and . Since small scales collapse earlier and
eventually before the BEC phase transition the evolution of collapsing halos in
this limit is indeed the same in both the CDM and the BEC models. Differences
are expected to appear only on the largest astrophysical scales. However, we
argue that the BEC model is almost indistinguishable from the usual dark matter
scenario concerning the evolution of nonlinear perturbations above typical
clusters scales, i.e., . This provides an analytical
confirmation for recent results from cosmological numerical simulations [H.-Y.
Schive {\it et al.}, Nature Physics, {\bf10}, 496 (2014)].Comment: 11 pages. Final version to appear in EPJ
Expanding FLew with a Boolean connective
We expand FLew with a unary connective whose algebraic counterpart is the
operation that gives the greatest complemented element below a given argument.
We prove that the expanded logic is conservative and has the Finite Model
Property. We also prove that the corresponding expansion of the class of
residuated lattices is an equational class.Comment: 15 pages, 4 figures in Soft Computing, published online 23 July 201
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On the prevalence of racial discrimination in the United States.
Boutwell, Nedelec, Winegard, Shackelford, Beaver, Vaughn, Barnes, & Wright (2017) published an article in this journal that interprets data from the Add Health dataset as showing that only one-quarter of individuals in the United States experience discrimination. In Study 1, we attempted to replicate Boutwell et al.s findings using a more direct measure of discrimination. Using data from the Pew Research Center, we examined a large sample of American respondents (N = 3,716) and explored the prevalence of discrimination experiences among various racial groups. Our findings stand in contrast to Boutwell et al.s estimates, revealing that between 50% and 75% of Black, Hispanic, and Asian respondents (depending on the group and analytic approach) reported discriminatory treatment. In Study 2, we explored whether question framing affected how participants responded to Boutwells question about experiencing less respect and courtesy. Regardless of question framing, non-White participants reported more experiences than White participants. Further, there was an interaction of participant race and question framing such that when participants were asked about experiences of less respect or courtesy broadly, there were no differences between non-White participants and White participants, but when they were asked about experiences that were specifically race-based, non-White participants reported more experiences than White participants. The current research provides a counterweight to the claim that discrimination is not a prevalent feature of the lives of minority groups and the serious implications this claim poses for research and public policy
Monopole ordered phases in dipolar and nearest-neighbours Ising pyrochlore: from spin ice to the "all-in--all-out" antiferromagnet
We study Ising pyrochlores by means of Monte Carlo simulations. We cover a
set of exchange constants ranging from the frustrated ferromagnetic case
(spin-ice) to the fully-ordered "all-in--all-out" antiferromagnet in the
dipolar model, reinterpreting the results --as in an ionic system-- in terms of
a temperature vs. magnetic charge density phase diagram. In spite of its spin
nature and the presence of both double and single non-conserved magnetic
charges, the dipolar model gives place to a phase diagram which is quite
comparable with those previously obtained for on-lattice systems of electric
charges, and on spin ice models with conserved number of single magnetic
charges. The contrast between these systems, to which we add results from the
nearest-neighbours model, put forward other features of our phase diagram
--notably, a monopole fluid with charge order at high monopole densities that
persists up to arbitrarily high temperatures-- that can only be explained
taking into account construction constraints forced by the underlying spin
degrees of freedom.Comment: 9 pages, 10 figure
Heteroskedasticity, the single crossing property and ordered response models
Heteroskedasticity in ordered response models has not garnered enough attention in the literature. Econometric software packages do not handle this problem satisfactorily either. We provide formulas to calculate heteroskedasticity corrected marginal effects and discrete changes using an approach that deals with single crossing property, a very restrictive assumption of ordered response models.
Food involvement and food purchasing behaviour
This paper investigates the factors affecting product class involvement for food. Factors affecting specific aspects of involvement are also explored. The aim is to determine the factors that affect involvement with food and sketch the profile of consumers more likely to be involved or not involved with food. Building on the literature a conceptual model is developed and empirically tested using survey data collected from supermarkets in Athens. Data were analyzed using probit and ordered probit analysis and marginal effects were calculated which show how much the level of involvement or importance is affected when a variable is changed. Results show that younger consumers, those with higher education and income that engage in nutritional label use behaviour and do not prepare food for their household are more likely to have low involvement with food. Less distinctive characteristics are apparent for the highly involved consumers. Different consumer profiles are also associated with different aspects of food involvement based on importance attached to price, ease of preparation, nutrition, taste, and brand name.product class involvement, food involvement, consumer behaviour, food shopping, attribute importance, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,
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