Strong interplay between electron-phonon interaction and disorder in low doped systems

The effects of doping on the spectral properties of low doped systems are investigated by means of Coherent Potential Approximation to describe the distributed disorder induced by the impurities and Phonon-Phonon Non-Crossing Approximation to characterize a wide class of electron-phonon interactions which dominate the low-energy spectral features. When disorder and electron-phonon interaction work on comparable energy scales, a strong interplay between them arises, the effect of disorder can no more be described as a mere broadening of the spectral features and the phonon signatures are still visible despite the presence of strong disorder. As a consequence, the disorder-induced metal-insulator transition, is strongly affected by a weak or moderate electron-phonon coupling which is found to stabilize the insulating phase.Comment: New version with improved bibliography and discussio

Testing a quintessence model with CMBR peaks locations

We show that a model of quintessence with exponential potential, which allows to obtain general exact solutions, can generate location of CMBR peaks which are fully compatible with present observational data

Testing a quintessence model with CMBR peaks location

We show that a model of quintessence with exponential potential, which allows to obtain general exact solutions, can generate locations of CMBR peaks which are fully compatible with present observational dataComment: 7 pages, no figure

Hodge theory and deformations of affine cones of subcanonical projective varieties:

We investigate the relation between the Hodge theory of a smooth subcanonical n-dimensional projective variety X and the deformation theory of the affine cone A_X over X. We start by identifying H^{n−1,1}_prim(X) as a distinguished graded component of the module of first order deformations of A_X, and later on we show how to identify the whole primitive cohomology of X as a distinguished graded component of the Hochschild cohomology module of the punctured affine cone over X. In the particular case of a projective smooth hypersurface X we recover Griffiths' isomorphism between the primitive cohomology of X and certain distinguished graded components of the Milnor algebra of a polynomial defining X. The main result of the article can be effectively exploited to compute Hodge numbers of smooth subcanonical projective varieties. We provide a few example computation, as well a SINGULAR code, for Fano and Calabi-Yau threefolds

Fixed, Tethered or Free: The Role of Space and Place in Online Home-Based Businesses

Online businesses were heralded as being ‘anytime, anyplace, anywhere’ businesses, allowing the entrepreneurs who run them to be free of locational constraints. In contrast, entrepreneurs who operate home-based businesses have made a conscious choice to operate their business from home. This study explores the role of space and place for entrepreneurs who have brought these two types of business together, that is, entrepreneurs who are operating online home-based businesses. Such businesses are important as the have been identified as offering a unique opportunity for experimentation and innovation are hence a source of business diversity. The also offer economic benefits both at the individual micro level and at the macro-economic level. The study, which is exploratory in nature, is undertaken by means of key informant interviews with 42 entrepreneurs who are operating online home based businesses. The study finds that whilst certain factors allow such businesses to be location independent, other factors constrain the location of the businesses, usually to the home. The study findings suggest that there is a more subtle third alternative we term ‘tethered’ businesses, that lies between these two extremes of location dependent or independent, which is more appropriate for many online home-based businesses

Combined quantum state preparation and laser cooling of a continuous beam of cold atoms

We use two-laser optical pumping on a continuous atomic fountain in order to prepare cold cesium atoms in the same quantum ground state. A first laser excites the F=4 ground state to pump the atoms toward F=3 while a second pi-polarized laser excites the F=3 -> F'=3 transition of the D2 line to produce Zeeman pumping toward m=0. To avoid trap states, we implement the first laser in a 2D optical lattice geometry, thereby creating polarization gradients. This configuration has the advantage of simultaneously producing Sisyphus cooling when the optical lattice laser is tuned between the F=4 -> F'=4 and F=4 -> F'=5 transitions of the D2 line, which is important to remove the heat produced by optical pumping. Detuning the frequency of the second pi-polarized laser reveals the action of a new mechanism improving both laser cooling and state preparation efficiency. A physical interpretation of this mechanism is discussed.Comment: Minor changes according to the recommendations of the referee: - Corrected Fig.1. - Split the graph of Fig.6 for clarity. - Added one reference. - Added two remarks in the conclusion. - Results unchange

A unifying framework for kk-statistics, polykays and their multivariate generalizations

Through the classical umbral calculus, we provide a unifying syntax for single and multivariate $k$-statistics, polykays and multivariate polykays. From a combinatorial point of view, we revisit the theory as exposed by Stuart and Ord, taking into account the Doubilet approach to symmetric functions. Moreover, by using exponential polynomials rather than set partitions, we provide a new formula for $k$-statistics that results in a very fast algorithm to generate such estimators.Comment: Published in at http://dx.doi.org/10.3150/07-BEJ6163 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Assessing systemic risk due to fire sales spillover through maximum entropy network reconstruction

Assessing systemic risk in financial markets is of great importance but it often requires data that are unavailable or available at a very low frequency. For this reason, systemic risk assessment with partial information is potentially very useful for regulators and other stakeholders. In this paper we consider systemic risk due to fire sales spillover and portfolio rebalancing by using the risk metrics defined by Greenwood et al. (2015). By using the Maximum Entropy principle we propose a method to assess aggregated and single bank's systemicness and vulnerability and to statistically test for a change in these variables when only the information on the size of each bank and the capitalization of the investment assets are available. We prove the effectiveness of our method on 2001-2013 quarterly data of US banks for which portfolio composition is available.Comment: 36 pages, 6 figures, Accepted on Journal of Economic Dynamics and Contro

Different titanium surfaces modulate the bone phenotype of SaOS-2 osteoblast-like cells.

Commercially pure titanium implants presenting a relatively smooth, machined surface or a roughned endosseous surface show a large percentage of clinical successes. Surface properties of dental implants seem to be important with respect to bone cells response. Implant topography appears to modulate cell growth and differentiation of osteoblasts affecting the bone healing around the titanium implant. The aim of the present study was to examine the effects of three different titanium surfaces on cell morphology, adhesion and bone phenotypic expression of human osteoblast-like cells, SaOS-2. SaOS-2 cells were cultured on commercially pure titanium disks of 1 cm in diameter with three different surface roughness: smooth (S), sandblasted (SB) and titanium plasma sprayed (TPS). Differences in the cell morphology were found on the three surfaces showing an uniform monolayer of shaped cells on the S surfaces, and clusters of multilayered cells with an irregular shape on the rough surfaces. The adhesion of SaOS-2 cells, as measured after 3h of culture, was not affected by surface roughness. ECM components such as collagen I (CoI), fibronectin (FN), vitronectin (VN) and tenascin (TN) were secreted and organized only on SB and TPS surfaces while on S surfaces they remained in the cytoplasm. Osteopontin and BSP-II were largely detected on SB and TPS surfaces, while only minimal production was observed on S surfaces. These data show that titanium surface roughness affects bone differentiation of osteoblast like-cells, SaOS-2, indicating that surface properties may be able to modulate the osteoblast phenotype. These observations also suggest that the bone healing response around dental implants can be affected by surface topography