Quantum phase transitions from topology in momentum space

Many quantum condensed matter systems are strongly correlated and strongly interacting fermionic systems, which cannot be treated perturbatively. However, physics which emerges in the low-energy corner does not depend on the complicated details of the system and is relatively simple. It is determined by the nodes in the fermionic spectrum, which are protected by topology in momentum space (in some cases, in combination with the vacuum symmetry). Close to the nodes the behavior of the system becomes universal; and the universality classes are determined by the toplogical invariants in momentum space. When one changes the parameters of the system, the transitions are expected to occur between the vacua with the same symmetry but which belong to different universality classes. Different types of quantum phase transitions governed by topology in momentum space are discussed in this Chapter. They involve Fermi surfaces, Fermi points, Fermi lines, and also the topological transitions between the fully gapped states. The consideration based on the momentum space topology of the Green's function is general and is applicable to the vacua of relativistic quantum fields. This is illustrated by the possible quantum phase transition governed by topology of nodes in the spectrum of elementary particles of Standard Model.Comment: 45 pages, 17 figures, 83 references, Chapter for the book "Quantum Simulations via Analogues: From Phase Transitions to Black Holes", to appear in Springer lecture notes in physics (LNP

Measurement of Z0 decays to hadrons, and a precise determination of the number of neutrino species

We have made a precise measurement of the cross section for e+e--->Z0-->hadrons with the L3 detector at LEP, covering the range from 88.28 to 95.04 GeV. From a fit to the Z0 mass, total width, and the hadronic cross section to be MZ0=91.160 +/- 0.024 (experiment) +/-0.030(LEP) GeV, [Gamma]Z0=2.539+/-0.054 GeV, and [sigma]h(MZ0)=29.5+/-0.7 nb. We also used the fit to the Z0 peak cross section and the width todetermine [Gamma]invisible=0.548+/-0.029 GeV, which corresponds to 3.29+/-0.17 species of light neutrinos. The possibility of four or more neutrino flavors is thus ruled out at the 4[sigma] confidence level.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28683/3/0000500.pd

A measurement of the Z0 leptonic partial widths and the vector and axial vector coupling constants

We have measured the partial widths of the Z0 into lepton pairs, and the forward-backward charge asymmetry for the process e+e--->[mu]+[mu]- using the L3 detector at LEP. We obtain an average [Gamma]ll of 83.0+/-2.1+/-1.1 MeV.From this result and the asymmetry measurement, we extract the values of the vector and axial vector couplings of the Z0 to leptons: grmv=-0.066-0.027+0.046 and grmA= -0.495-0.007+0.007.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28666/3/0000483.pd

Collaborative design and manufacturing process planning in tooling industry

10.1504/IJCAT.2007.015727International Journal of Computer Applications in Technology303221-234IJCT

Collaborative manufacturing process planning for distributed integration in tooling industry

10.1504/IJMTM.2008.017483International Journal of Manufacturing Technology and Management141-217-3

Clinical analysis of 182 cases with facial nerve injury

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Collaborative process planning and manufacturing in product lifecycle management

10.1016/j.compind.2007.06.012Computers in Industry592-3154-166CINU

Effect of Vacancies on the Nucleation of Cr Precipitates at Grain Boundary in α-Fe

Effect of local vacancies on the nucleation of Cr precipitates at Σ3 ⟨110⟩ {112} grain boundary (GB) in α-Fe has been studied using molecular dynamics with a two-band embedded atomic model potential. Radiation-induced vacancies and Cr atoms were directly introduced into the GB core. The local vacancies affect the accumulation of Cr atoms and the evolution of the GB. It is of interest to find that high vacancy concentrations enhance the long-distance migration of Cr, which is mainly correlated to the vacancy migration mechanism, thus leading to the formation of large vacancy-diluted Cr precipitates near the GB plane. Also, the large vacancy clusters are found to be depleted by Cr atoms during relaxation. The accumulation of vacancies and nucleation of Cr precipitates at the GB lead to significant deformation of the GB structure, resulting in the displacement and broadening of the GB. Without vacancies, the GB tends to climb perpendicular to the GB axis. The current research could help in understanding the nucleation mechanism of Cr precipitates at the GB in α-Fe.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author