Residual Entropy of the Mott Insulator with No Symmetry Broken

The half-filled ground state of the Hubbard model on the hypercubic lattice in D dimensions is studied by the Kondo-lattice theory, which is none other than the 1/D expansion theory, but within the constrained Hilbert subspace where no symmetry is allowed to be broken. A gap can open in the single-particle excitation spectrum if and only if the residual entropy or entropy at T=+0 K is nonzero. The Mott insulator with no symmetry broken, if it is possible, is characterized by nonzero residual entropy or nonzero entropy at T=+0 K. This conclusion is consistent with Brinkman and Rice's theory and the dynamical mean-field theory. According to the well-known argument based on the Bethe-ansatz solution, on the other hand, the half-filled ground state in one dimension is the Mott insulator although its residual entropy per unit cell is vanishing in the thermodynamic limit. Two possible explanations are given for the contradiction between the present paper and the well-known argument.Comment: 27 page

Effect of Particle-Hole Asymmetry on the Mott-Hubbard Metal-Insulator Transition

The Mott-Hubbard metal-insulator transition is one of the most important problems in correlated electron systems. In the past decade, much progress has been made on examining a particle-hole symmetric form of the transition in the Hubbard model with dynamical mean field theory where it was found that the electronic self energy develops a pole at the transition. We examine the particle-hole asymmetric metal-insulator transition in the Falicov-Kimball model, and find that a number of features change when the noninteracting density of states has a finite bandwidth. Since, generically particle-hole symmetry is broken in real materials, our results have an impact on understanding the metal-insulator transition in real materials.Comment: 5 pages, 3 figure

Measuring compassion in young people

There has been increased scientific interest in compassion in recent years, and compassion is suggested to have many benefits for young people, reflecting the adult literature. However, research highlights issues related to the measurement of compassion in young people. The systematic review aimed to describe and critically appraise the compassion measures used with young people, and their psychometric properties. Three databases were searched (Medline, Psychinfo, Web of Science), and 15 papers were included which outlined the psychometric properties of eight compassion measures used with young people. The measures were critically reviewed and rated for quality, with quality ratings ranging from 2 to 9 out of 14. All measures had clear psychometric weaknesses. The majority of papers assessed self-compassion and no identified papers examined psychometric properties with young people in the UK. Overall, this review suggests that the majority of compassion measures are not suitable for use with young people. Recommendations for future research are discussed

Structural Change and Distribution of Support in Hungarian Agriculture following EU Accession: A Preliminary FADN Analysis

This paper, whilst preliminary and descriptive, highlights some significant changes in the structure of the Hungarian national farm around the time of EU accession, based on an examination of farm-level data. Between 2002 and 2005 gross value of total production changes little, but direct agricultural subsidies nearly double. There is a marked shift in favour of arable farming, which affects both private farms and economic organisations. Arable farms increase their share of total subsidies by 20 percentage points over the three years, at the expense of most animal and mixed farms. Overall, the distribution of subsidies, whilst highly unequal, is slightly less unequal in 2005.Agricultural and Food Policy,

Replications and Extensions in Marketing – Rarely Published But Quite Contrary

Replication is rare in marketing. Of 1,120 papers sampled from three major marketing journals, none were replications. Only 1.8% of the papers were extensions, and they consumed 1.1% of the journal space. On average, these extensions appeared seven years after the original study. The publication rate for such works has been decreasing since the 1970s. Published extensions typically produced results that conflicted with the original studies; of the 20 extensions published, 12 conflicted with the earlier results, and only 3 provided full confirmation. Published replications do not attract as many citations after publication as do the original studies, even when the results fail to support the original studies

Are Null Results Becoming an Endangered Species in Marketing?

Editorial procedures in the social and biomedical sciences are said to promote studies that falsely reject the null hypothesis. This problem may also exist in major marketing journals. Of 692 papers using statistical significance tests sampled from the Journal of Marketing, Journal of Marketing Research, and Journal of Consumer Research between 1974 and 1989, only 7.8% failed to reject the null hypothesis. The percentage of null results declined by one-half from the 1970s to the 1980s. The JM and the JMR registered marked decreases. The small percentage of insignificant results could not be explained as being due to inadequate statistical power. Various scholars have claimed that editorial policies in the social and medical sciences are biased against studies reporting null results, and thus encourage the proliferation of Type 1 errors (erroneous rejection of the null hypothesis). Greenwald (1975, p. 15) maintains that Type I publication errors are underestimated to the extent that they are: “. . . frightening, even calling into question the scientific basis for much published literature.” Our paper examines the publication frequency of null results in marketing. First, we discuss how editorial policies might foster an atmosphere receptive to Type I error proliferation. Second, we review the evidence on the publication of null results in the social and biomedical sciences. Third, we report on an empirical investigation of the publication frequency of null results in the marketing literature. Fourth, we examine power levels for statistically insignificant findings in marketing to see if they are underpowered and thus less deserving of publication. Finally, we provide suggestions to facilitate the publication of null results

A chemical model for lunar non-mare rocks

Nearly all rocks returned from the moon are readily divided into three broad categories on the basis of their chemical compositions: (1) mare basalts, (2) non-mare rocks of basaltic composition (KREEP, VHA), and (3) anorthositic rocks. Only mare basalts may unambiguously be considered to have original igneous textures and are widely understood to have an igneous origin. Nearly all other lunar rocks have lost their original textures during metamorphic and impact processes. For these rocks one must work primarily with chemical data in order to recognize and define rock groups and their possible modes of origin. Non-mare rocks of basaltic composition have chemical compositions consistent with an origin by partial melting of the lunar interior. The simplest origin for rocks of anorthositic chemical composition is the crystallization and removal of ferromagnesian minerals. It is proposed that the rock groups of anorthositic and non-mare basaltic chemical composition could have been generated from a single series of original, but not necessarily primitive, lunar materials

A chemical model for lunar non-mare rocks

Nearly all rocks returned from the moon are readily divided into three broad categories on the basis of their chemical compositions: (1) mare basalts, (2) non-mare rocks of basaltic composition (KREEP, VHA), and (3) anorthositic rocks. Only mare basalts may unambiguously be considered to have original igneous textures and are widely understood to have an igneous origin. Nearly all other lunar rocks have lost their original textures during metamorphic and impact processes. It is shown that for these rocks one must work primarily with chemical data in order to recognize and define rock groups and their possible modes of origin. Non-mare rocks of basaltic composition have chemical compositions consistent with an origin by partial melting of the lunar interior. The simplest origin for rocks of anorthositic chemical composition is the crystallization and removal of ferromagnesian minerals. It is proposed that the rock groups of anorthositic and non-mare basaltic chemical composition could have been generated from a single series of original but not necessarily primitive lunar materials

Compressibility of the Two-Dimensional infinite-U Hubbard Model

We study the interactions between the coherent quasiparticles and the incoherent Mott-Hubbard excitations and their effects on the low energy properties in the $U=\infty$ Hubbard model. Within the framework of a systematic large-N expansion, these effects first occur in the next to leading order in 1/N. We calculate the scattering phase shift and the free energy, and determine the quasiparticle weight Z, mass renormalization, and the compressibility. It is found that the compressibility is strongly renormalized and diverges at a critical doping $\delta_c=0.07\pm0.01$. We discuss the nature of this zero-temperature phase transition and its connection to phase separation and superconductivity.Comment: 4 pages, 3 eps figures, final version to appear in Phys. Rev. Let

Cold dilute neutron matter on the lattice II: Results in the unitary limit

This is the second of two papers which investigate cold dilute neutron matter on the lattice using pionless effective field theory. In the unitary limit, where the effective range is zero and scattering length is infinite, simple scaling relations relate thermodynamic functions at different temperatures. When the second virial coefficient is properly tuned, we find that the lattice results obey these scaling relations. We compute the energy per particle, pressure, spin susceptibility, dineutron correlation function, and an upper bound for the superfluid critical temperature.Comment: 16 pages, 9 figure