4,245 research outputs found

    One-dimensional classical adjoint SU(2) Coulomb Gas

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    The equation of state of a one-dimensional classical nonrelativistic Coulomb gas of particles in the adjoint representation of SU(2) is given. The problem is solved both with and without sources in the fundamental representation at either end of the system. The gas exhibits confining properties at low densities and temperatures and deconfinement in the limit of high densities and temperatures. However, there is no phase transition to a regime where the string tension vanishes identically; true deconfinement only happens for infinite densities and temperatures. In the low density, low temperature limit, a new type of collective behavior is observed.Comment: 6 pages, 1 postscript figur

    Chemical vapor deposition of high T sub c superconductors

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    The results are reported of an investigation into the synthesis and properties of high temperature superconducting materials. A chemical vapor deposition apparatus was designed and built which is suitable for the preparation of multicomponent metal films This apparatus was used to prepare a series of high T sub c A-15 structure superconducting films in the binary system Nb-Ge. The effect on T sub c of a variety of substrate materials was investigated. An extensive series of ternary alloys were also prepared. Conditions allowing the brittle high T sub c (approximately 18 K) A-15 structure superconductor Nb3A1 to be prepared in a low T sub c but ductile form were found. Some of the ways that the ductile (bcc) form can be cold worked or machined are described. Measurements of rate of transformation of cold worked bcc material to the high T sub c A-15 structure with low temperature annealing are given. Preliminary measurements indicate that this material has attractive high field critical current densities

    Sivers and Boer-Mulders observables from lattice QCD

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    We present a first calculation of transverse momentum dependent nucleon observables in dynamical lattice QCD employing non-local operators with staple-shaped, "process-dependent" Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and in particular to access non-universal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm gear function g_1T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an n_f = 2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.Comment: 25 pages, 13 figures; version accepted by journal. Contains additional section explaining and summarizing the methodolog

    The intrinsic strangeness and charm of the nucleon using improved staggered fermions

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    We calculate the intrinsic strangeness of the nucleon, - , using the MILC library of improved staggered gauge configurations using the Asqtad and HISQ actions. Additionally, we present a preliminary calculation of the intrinsic charm of the nucleon using the HISQ action with dynamical charm. The calculation is done with a method which incorporates features of both commonly-used methods, the direct evaluation of the three-point function and the application of the Feynman- Hellman theorem. We present an improvement on this method that further reduces the statistical error, and check the result from this hybrid method against the other two methods and find that they are consistent. The values for and found here, together with perturbative results for heavy quarks, show that dark matter scattering through Higgs-like exchange receives roughly equal contributions from all heavy quark flavors.Comment: 17 pages, 14 figure

    Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations

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    We report contributions to the nucleon spin and momentum from light quarks calculated using dynamical domain wall fermions with pion masses down to 300 MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams, we observe that spin and orbital angular momenta of both u and d quarks are opposite, almost canceling in the case of the d quark, which agrees with previous calculations using a mixed quark action. We also present the full momentum dependence of n=2 generalized form factors showing little variation with the pion mass.Comment: 7 pages, 5 figures, NT-LBNL-11-020, MIT-CTP-4323. Presented at the 29th International Symposium on Lattice Field Theory (Lattice 2011), Squaw Valley, California, 10-16 Jul 201

    Isolated familial pheochromocytoma as a variant of von Hippel-Lindau disease.

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    Inherited pheochromocytomas are often part of familial syndromes, especially multiple endocrine neoplasia type 2 (MEN 2), retinal cerebellar hemangioblastomatosis [von Hippel-Lindau (vHL) disease] or neurofibromatosis type 1. It is not clear whether isolated familial pheochromocytoma exists as a separate clinical entity. In a family with pheochromocytomas in three generations and with at least seven affected members, we investigated by clinical and genetic analyses the presence or absence of associated conditions. The clinical investigations included ophthalmological and radiological studies for von Hippel-Lindau disease (magnetic resonance imaging of the brain, computed tomography of the abdomen, and direct ophthalmoscopy after mydriasis) and annual calcitonin stimulation tests for C cell disease in five members who agreed to regular follow-up. Besides the pheochromocytomas (so far, these have been multiple in five of seven individuals) no definite second associated condition was found. Genetic analysis did not identify any MEN 2-specific RET protooncogene point mutations (which are present in 97% of MEN 2a families). However, despite the complete absence of other clinical manifestations of the vHL disease (besides pheochromocytomas), a previously undescribed germline missense mutation in the vHL tumor suppressor gene was found (C775G transversion with a predicted substitution of a leucine by a valine at codon 259 in the putative vHL protein). We conclude that in this family the sole occurrence of pheochromocytoma is a variant of vHL disease

    Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass

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    We present lattice QCD calculations of nucleon electromagnetic form factors using pion masses mπm_\pi = 149, 202, and 254 MeV and an action with clover-improved Wilson quarks coupled to smeared gauge fields, as used by the Budapest-Marseille-Wuppertal collaboration. Particular attention is given to removal of the effects of excited state contamination by calculation at three source-sink separations and use of the summation and generalized pencil-of-function methods. The combination of calculation at the nearly physical mass mπm_\pi = 149 MeV in a large spatial volume (mπLsm_\pi L_s = 4.2) and removal of excited state effects yields agreement with experiment for the electric and magnetic form factors GE(Q2)G_E(Q^2) and GM(Q2)G_M(Q^2) up to Q2Q^2 = 0.5 GeV2^2.Comment: v2: published version; 30 pages, 25 figures, 6 table

    Detecting axion dark matter with Rydberg atoms via induced electric dipole transitions

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    Long-standing efforts to detect axions are driven by two compelling prospects, naturally accounting for the absence of charge-conjugation and parity symmetry breaking in quantum chromodynamics, and for the elusive dark matter at ultralight mass scale. Many experiments use advanced cavity resonator setups to probe the magnetic-field-mediated conversion of axions to photons. Here, we show how to search for axion matter without relying on such a cavity setup, which opens a new path for the detection of ultralight axions, where cavity based setups are infeasible. When applied to Rydberg atoms, which feature particularly large transition dipole elements, this effect promises an outstanding sensitivity for detecting ultralight dark matter. Our estimates show that it can provide laboratory constraints in parameter space that so far had only been probed astrophysically, and cover new unprobed regions of parameter space. The Rydberg atomic gases offer a flexible and inexpensive experimental platform that can operate at room temperature. We project the sensitivity by quantizing the axion-modified Maxwell equations to accurately describe atoms and molecules as quantum sensors wherever axion dark matter is present.Comment: 27 pages, including Supplementary Materials. Comments are welcom
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