7,683 research outputs found
Phase diagram and quasiparticle properties of the Hubbard model within cluster two-site DMFT
We present a cluster dynamical mean-field treatment of the Hubbard model on a
square lattice to study the evolution of magnetism and quasiparticle properties
as the electron filling and interaction strength are varied. Our approach for
solving the dynamical mean-field equations is an extension of Potthoff's
"two-site" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent
bath is represented by a highly restricted set of states. As well as the
expected antiferromagnetism close to half filling, we observe distortions of
the Fermi surface. The proximity of a van Hove point and the incipient
antiferromagnetism lead to the evolution from an electron-like Fermi surface
away from the Mott transition, to a hole-like one near half-filling. Our
results also show a gap opening anisotropically around the Fermi surface close
to the Mott transition (reminiscent of the pseudogap phenomenon seen in the
cuprate high-Tc superconductors). This leaves Fermi arcs which are closed into
pockets by lines with very small quasiparticle residue.Comment: 10 pages, 8 figures, latex (revtex4
Small-angle scattering in a marginal Fermi-liquid
We study the magnetotransport properties of a model of small-angle scattering
in a marginal Fermi liquid. Such a model has been proposed by Varma and
Abrahams [Phys. Rev. Lett. 86, 4652 (2001)] to account for the anomalous
temperature dependence of in-plane magnetotransport properties of the high-Tc
cuprates. We study the resistivity, Hall angle and magnetoresistance using both
analytical and numerical techniques. We find that small-angle scattering only
generates a new temperature dependence for the Hall angle near particle-hole
symmetric Fermi surfaces where the conventional Hall term vanishes. The
magnetoresistance always shows Kohler's rule behavior.Comment: 4 pages, 3 figures, Revtex
Rhode Island Election Tickets: A Survey
Rhode Island was the first English colony in America to issue printed election ballots, with the first issued in the mid-1740s. This survey of Rhode Island election tickets, while not exhaustive, is representative of the use of tickets in elections spanning a period of over 150 years and documents state and local politics, political factions and election results from the Ward-Hopkins controversy of the colonial period to political factions during the War of 1812, the Anti-Masonic period of the 1830s, the Law and Order coalition of the 1840s following events of the Dorr Rebellion, the temperance movement of the 1850s, the pro-Union tickets of the Civil War, and Greenback party and Prohibitory factions of the 1870s and 1880s. Statewide elections for general officers, United States congressional representatives, presidential electors, special purpose elections as well as local elections for city, town and district offices are also examined. The scope of this study includes a survey of tickets found in the collections of the University of Rhode Island Library Special Collections, Rhode Island State Archives, Warwick Historical Society as well as private collections of Henry A.L. Brown, Russell DeSimone, and Daniel Schofield.
This document was last revised in 2015. The previous version (2007) can be found below as a supplemental file
Voting and the Spirit of Democracy
This book is published in conjunction with Voting and the Spirit of Democracy, an exhibition held at the University Library, University of Rhode Island 2004
Probing spin-charge separation in a Tomonaga-Luttinger liquid
In a one-dimensional (1D) system of interacting electrons, excitations of
spin and charge travel at different speeds, according to the theory of a
Tomonaga-Luttinger Liquid (TLL) at low energies. However, the clear observation
of this spin-charge separation is an ongoing challenge experimentally. We have
fabricated an electrostatically-gated 1D system in which we observe spin-charge
separation and also the predicted power-law suppression of tunnelling into the
1D system. The spin-charge separation persists even beyond the low-energy
regime where the TLL approximation should hold. TLL effects should therefore
also be important in similar, but shorter, electrostatically gated wires, where
interaction effects are being studied extensively worldwide.Comment: 11 pages, 4 PDF figures, uses scicite.sty, Science.bs
Efficient algorithms for rigid body integration using optimized splitting methods and exact free rotational motion
Hamiltonian splitting methods are an established technique to derive stable
and accurate integration schemes in molecular dynamics, in which additional
accuracy can be gained using force gradients. For rigid bodies, a tradition
exists in the literature to further split up the kinetic part of the
Hamiltonian, which lowers the accuracy. The goal of this note is to comment on
the best combination of optimized splitting and gradient methods that avoids
splitting the kinetic energy. These schemes are generally applicable, but the
optimal scheme depends on the desired level of accuracy. For simulations of
liquid water it is found that the velocity Verlet scheme is only optimal for
crude simulations with accuracies larger than 1.5%, while surprisingly a
modified Verlet scheme (HOA) is optimal up to accuracies of 0.4% and a fourth
order gradient scheme (GIER4) is optimal for even higher accuracies.Comment: 2 pages, 1 figure. Added clarifying comments. Accepted for
publication in the Journal of Chemical Physic
Energetic Instability Unjams Sand and Suspension
Jamming is a phenomenon occurring in systems as diverse as traffic, colloidal
suspensions and granular materials. A theory on the reversible elastic
deformation of jammed states is presented. First, an explicit granular
stress-strain relation is derived that captures many relevant features of sand,
including especially the Coulomb yield surface and a third-order jamming
transition. Then this approach is generalized, and employed to consider jammed
magneto- and electro-rheological fluids, again producing results that compare
well to experiments and simulations.Comment: 9 pages 2 fi
Mutation analysis of HIF prolyl hydroxylases (PHD/EGLN) in individuals with features of phaeochromocytoma and renal cell carcinoma susceptibility
Germline mutations in the von Hippel–Lindau disease (VHL) and succinate dehydrogenase subunit B (SDHB) genes can cause inherited phaeochromocytoma and/or renal cell carcinoma(RCC). Dysregulation of the hypoxia-inducible factor (HIF) transcription factors has been linked to VHL and SDHB-related RCC; both HIF dysregulation and disordered function of a prolyl hydroxylase domain isoform 3 (PHD3/EGLN3)-related pathway of neuronal apoptosis have been linked to the development of phaeochromocytoma. The 2-oxoglutarate-dependent prolyl hydroxylase enzymes PHD1 (EGLN2), PHD2 (EGLN1) and PHD3 (EGLN3) have a key role in regulating the stability of HIF-a subunits (and hence expression of the HIF-a transcription factors). A germline PHD2 mutation has been reported in association with congenital erythrocytosis and recurrent extra-adrenal phaeochromocytoma. We undertook mutation analysis of PHD1, PHD2 and PHD3 in two cohorts of patients with features of inherited phaeochromocytoma (nZ82) and inherited RCC (nZ64) and no evidence of germline mutations in known susceptibility genes. No confirmed pathogenic mutations were detected suggesting that mutations in these genes are not a frequent cause of inherited phaeochromocytoma or RCC
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