Search results for "BARD"

Phase diagram of the quarter-filled extended Hubbard model on a two-leg ladder

2000

We investigate the ground-state phase diagram of the quarter-filled Hubbard ladder with nearest-neighbor Coulomb repulsion V using the Density Matrix Renormalization Group technique. The ground-state is homogeneous at small V, a ``checkerboard'' charge--ordered insulator at large V and not too small on-site Coulomb repulsion U, and is phase-separated for moderate or large V and small U. The zero-temperature transition between the homogeneous and the charge-ordered phase is found to be second order. In both the homogeneous and the charge-ordered phases the existence of a spin gap mainly depends on the ratio of interchain to intrachain hopping. In the second part of the paper, we construct an…

Stripe formation in doped Hubbard ladders

2004

We investigate the formation of stripes in $7\chunks \times 6$ Hubbard ladders with $4\chunks$ holes doped away from half filling using the density-matrix renormalization group (DMRG) method. A parallelized code allows us to keep enough density-matrix eigenstates (up to $m=8000$) and to study sufficiently large systems (with up to $7\chunks = 21$ rungs) to extrapolate the stripe amplitude to the limits of vanishing DMRG truncation error and infinitely long ladders. Our work gives strong evidence that stripes exist in the ground state for strong coupling ($U=12t$) but that the structures found in the hole density at weaker coupling ($U=3t$) are an artifact of the DMRG approach.

The composite operator method route to the 2D Hubbard model and the cuprates

2018

In this review paper, we illustrate a possible route to obtain a reliable solution of the 2D Hubbard model and an explanation for some of the unconventional behaviours of underdoped high-$T_\text{c}$ cuprate superconductors within the framework of the composite operator method. The latter is described exhaustively in its fundamental philosophy, various ingredients and robust machinery to clarify the reasons behind its successful applications to many diverse strongly correlated systems, controversial phenomenologies and puzzling materials.

The use of mosses in biomonitoring of selected areas in Poland and Spitsbergen in the years from 1975 to 2014

2015

We have compared historical changes in concentrations of the heavy metals Mn, Ni, Cu, Zn, Cd and Pb accumulated in samples from the Polish woodlands of Beskidy and Karkonosze (S, SE Poland) and the north-east regions of the country, versus the relatively little polluted areas of Spitsbergen of the Svalbard Archipelago. We have combined the results from literature with new results from 2014. The regions of Beskidy and Karkonosze were the most exposed to heavy metals deposition. However, from 1975 to 2014 there was a considerable decrease of concentrations of Cu, Zn, Cd and Pb at all Polish sites, clearly signifying improvement of environmental quality. For example, the average Cd concentrati…

Potere, consenso e dissenso nell’Ystoriola Langobardorum Beneventum degentium di Erchemperto

2021

Diversamente da quella narrata da Paolo Diacono nella «Historia Langobardorum», la storia dei Longobardi di Benevento fra l’VIII e il IX secolo, raccontata da Erchemperto nell’«Ystoriola Langobardorum Beneventum degentium», è una storia nella quale si alternano continuamente il bene e il male, Dio e Satana, il coraggio, la virtù, l’abnegazione da un lato e, dall’altro, la viltà, il tradimento, la perfidia. Personaggi positivi e personaggi negativi – insieme alle vicende delle quali, di volta in volta, essi sono protagonisti – si susseguono nell’«Ystoriola» a ritmo incalzante, e lo storico beneventano, talora in modo palese e scoperto, più spesso in maniera ellittica e sottintesa, manifesta …

PROVA TECNICA E CONTRADDITTORIO NEL PROCESSO PENALE

2023

When science and the criminal process come into contact, cognitive mechanisms are set in motion aimed at reorganizing knowledge belonging to worlds other than the legal one. In this context, the actors of the trial scene are forced to move on a hybrid terrain in which judicial epistemology and scientific epistemology mix. Such a fascinating picture pushes the scholar of the criminal process to seek interpretations suitable for explaining the multiple dilemmas that the phenomenon entails. Starting from a historical-legislative excursus of the expert evidence, the proposed analysis examines the different channels through which expert knowledge enters the process, starting from the investigati…

Mass spectral identification of the blocked N-terminal tryptic peptide of the ATPase inhibitor from beef heart mitochondria

1984

AbstractThe presence of a formyl blocking group at the N-terminus of the ATPase inhibitor has been identified and the partial sequence of the N-terminal peptide has been determined by fast atom bombardment and field desorption coupled to mass spectrometry. Minor discrepancies in amino acid sequence of the inhibitor between the present and published data [(1981) Proc. Natl. Acad. Sci. USA 78, 7403-7407] are reported and its relationships with other inhbitors are briefly discussed.

Las nuevas formas de movilidad de la población, la especificidad de la familia italiana y la explosión del coronavirus en Lombardía

2021

GAUSSIAN EFFECTIVE POTENTIAL AND ANTIFERROMAGNETISM IN THE HUBBARD MODEL

2012

The Gaussian Effective Potential (GEP) is shown to be a useful variational tool for the study of the magnetic properties of strongly correlated electronic systems. The GEP is derived for a single band Hubbard model on a two-dimensional bi-partite square lattice in the strong coupling regime. At half-filling the antiferromagnetic order parameter emerges as the minimum of the effective potential with an accuracy which improves over RPA calculations and is very close to that achieved by Monte Carlo simulations. Extensions to other magnetic systems are discussed.

Light-Induced Renormalization of the Dirac Quasiparticles in the Nodal-Line Semimetal ZrSiSe

2020

In nodal-line semimetals linearly dispersing states form Dirac loops in the reciprocal space, with high degree of electron-hole symmetry and almost-vanishing density of states near the Fermi level. The result is reduced electronic screening and enhanced correlations between Dirac quasiparticles. Here we investigate the electronic structure of ZrSiSe, by combining time- and angle-resolved photoelectron spectroscopy with ab initio density functional theory (DFT) complemented by an extended Hubbard model (DFT +U +V). We show that electronic correlations are reduced on an ultrashort timescale by optical excitation of high-energy electrons-hole pairs, which transiently screen the Coulomb interac…