Extended supersolid phase of frustrated hard-core bosons on a triangular lattice

We study a model of hard-core bosons with frustrated nearest-neighbor hopping ($t$) and repulsion ($V$) on the triangular lattice. We argue for a supersolid ground state in the large repulsion ($V\gg|t|$) limit where a dimer representation applies, by constructing a unitary mapping to the well understood unfrustrated hopping case. This generalized 'Marshall sign rule' allows us to establish the precise nature of the supersolid order by utilizing a recently proposed dimer variational wavefunction, whose correlations can be efficiently calculated using the Grassman approach. By continuity, a supersolid is predicted over the wide parameter range, $V>-2t>0$. This also establishes a simple phase diagram for the triangular lattice spin 1/2 XXZ antiferromagnet.Comment: 5 pages, 4 figure

Dynamic Structure Function in 3he-4he Mixtures

Relevant features of the dynamic structure function $S(q,\omega)$ in $^3$He-$^4$He mixtures at zero temperature are investigated starting from known properties of the ground state. Sum rules are used to fix rigorous constraints to the different contributions to $S(q,\omega)$, coming from $^3$He and $^4$He elementary excitations, as well as to explore the role of the cross term $S^{(3,4)}(q,\omega)$. Both the low-$q$ (phonon-roton $^4$He excitations and 1p-1h $^3$He excitations) and high-$q$ (deep inelastic scattering) ranges are discussed.Comment: 29 pages, Plain TeX, 11 figures available by request from [email protected]

Some comments on the inverse problem of pure point diffraction

In a recent paper, Lenz and Moody (arXiv:1111.3617) presented a method for constructing families of real solutions to the inverse problem for a given pure point diffraction measure. Applying their technique and discussing some possible extensions, we present, in a non-technical manner, some examples of homometric structures.Comment: 6 pages, contribution to Aperiodic 201

Intentionality versus Constructive Empiricism

By focussing on the intentional character of observation in science, we argue that Constructive Empiricism – B.C. van Fraassen’s much debated and explored view of science – is inconsistent. We then argue there are at least two ways out of our Inconsistency Argument, one of which is more easily to square with Constructive Empiricism than the other

Thermalized Displaced Squeezed Thermal States

In the coordinate representation of thermofield dynamics, we investigate the thermalized displaced squeezed thermal state which involves two temperatures successively. We give the wavefunction and the matrix element of the density operator at any time, and accordingly calculate some quantities related to the position, momentum and particle number operator, special cases of which are consistent with the results in the literature. The two temperatures have diffenent correlations with the squeeze and coherence components. Moreover, different from the properties of the position and momentum, the average value and variance of the particle number operator as well as the second-order correlation function are time-independent.Comment: 7 pages, no figures, Revtex fil

The abundances and distributions of molluscs in the southern Iberian Peninsula: A comparison of marine and terrestrial systems

Molluscs are the second most diverse of all animal phyla, and occur in many habitat types. They are, therefore, a particularly good phylum with which to compare and contrast differences between ecosystems. Mollusc data from a number of sites along the southern coast of the Iberian Peninsula are analysed to study patterns of diversity and distribution using a range of multivariate techniques. Within each site, data are presented from three locations -fully terrestrial, rocky intertidal and soft bottom benthic (10 m and 20 m depths)- all in close proximity. The species are then classified in relation to morphology and size, and analysed at supraspecific levels to elucidate underlying patterns. The observed patterns are briefly discussed, with particular reference to the differential scope and importance of controlling factors in each ecosystem, such as dispersal processes. The results from the systems are compared and discussed in the context of ecological and evolutionary constraints in MolluscaLos moluscos constituyen el segundo filo animal más diverso y se encuentran en muchos tipos de hábitat, por lo que son idóneos para establecer comparaciones entre distintos ecosistemas. Se han analizado los datos de los moluscos obtenidos en una serie de emplazamientos que cubrían el sur de la península Ibérica para determinar, empleando distintas técnicas multivariantes, los patrones de diversidad y distribución de estos organismos. Los datos se tomaron de ejemplares capturados en lugares del medio terrestre próximos a la línea de costa, de la franja intermareal rocosa y de sedimentos de fondos marinos situados a 10 y 20 m de profundidad. Las especies fueron clasificadas atendiendo a la morfología y el tamaño, y se analizaron a nivel supraespecífico para elucidar los patrones generales, que se discuten aquí, brevemente, con especial énfasis en las diferencias según la importancia de los factores que controlan cada ecosistema, como, por ejemplo, los procesos de dispersión. Los resultados de los distintos sistemas se comparan y discuten en el contexto de las tendencias ecológicas y evolutivas de los molusco

Felix Alexandrovich Berezin and his work

This is a survey of Berezin's work focused on three topics: representation theory, general concept of quantization, and supermathematics.Comment: LaTeX, 27 page

A Major Fraction of Fibronectin Present in the Extracellular Matrix of Tissues Is Plasma-derived

The origin of the fibronectin (FN) found in the extracellular matrix of tissues has not been defined experimentally. Previous studies suggest that there is contribution from both local tissue production and transfer from plasma, but the extent of this phenomenon has not been addressed. We have shown before that engineered mice constitutively expressing extra domain A-containing FN (EDA+FN) have a significant decrease of FN levels in plasma and most tissues. We showed that hepatocytes modified to produce EDA+FN have normal extracellular matrix-FN levels but secrete less soluble FN. When we performed a liver-specific EDA-exon deletion in these animals, FN levels were restored both in plasma and tissues. Therefore, an important fraction of tissue FN, approximately an equal amount of that produced by the tissue itself, is actually plasma-derived, suggesting that plasma is an important source of tissue FN. The present results have potential significance for understanding the contributions of plasma FN, and perhaps other plasma proteins, in the modulation of cellular activities and in the formation of the extracellular matrix of tissues

The statistical properties of galaxy morphological types in compact groups of Main galaxies from the SDSS Data Release 4

In order to explore the statistical properties of galaxy morphological types in compact groups (CGs), we construct a random group sample which has the same distributions of redshift and number of member galaxies as those of the CG sample. It turns out that the proportion of early-type galaxies in different redshift bins for the CG sample is statistically higher than that for random group sample, and with growing redshift z this kind of difference becomes more significant. This may be due to the existence of interactions and mergers within a significant fraction of SDSS CGs. We also compare statistical results of CGs with those of more compact groups and pairs, but do not observe as large statistical difference as Hickson (1982)'results.Comment: 12 pages, 9 figure