Engineering topics
Greensite, Jeff
Publications and source records attributed to Greensite, Jeff.
Quantum excitations of static charges in the Ginzburg-Landau model of superconductivity
We point out that in superconductors there may exist localized quantum excitations of the electric and condensate fields surrounding a static charge, which cannot be interpreted as simply the ground state of the screened charge plus some number of massive photons. This is illustrated via a lattice Monte Carlo calculation of the energy spectrum of a pair of separated static charges in an effective Ginzburg-Landau model of superconductivity.
Multiplicity, localization, and domains in the Hartree–Fock ground state of the two-dimensional Hubbard model
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Excitations of static isolated fermions in the Higgs phase of gauge Higgs theory
A spectrum of localized excitations of isolated static fermions has been discovered in several different gauge Higgs theories. In lattice numerical simulations, we show that the charged elementary particles can have the spectrum of excitations in the Higgs phase of SU(3) gauge Higgs theory, q=2 Abelian Higgs theory, Landau-Ginzburg theory, and in chiral U(1) gauge Higgs theory. Possibly these excited states of the isolated fermions can be observed in ARPES studies of conventional superconductors. Also, we consider that similar kinds of excitations could exist in other gauge Higgs theories, such as the electroweak sector of the Standard Model.
Nature of symmetry breaking in the superconducting ground state
The order parameters which are believed to detect U(1) gauge symmetry breaking in a superconductor are both nonlocal and gauge dependent. For that reason, they are further ambiguous as a guide to phase structure. We point out that a global subgroup of the local U(1) gauge symmetry may be regarded, in analogy to non-Abelian theories, as a “custodial” symmetry affecting the matter field alone, and construct, along the lines of our previous work, a gauge-invariant criterion for breaking symmetries of this kind. It is shown that spontaneous breaking of custodial symmetry is a necessary condition for the existence of spontaneous symmetry breaking of a global subgroup of the (Abelian or non-Abelian) gauge group in any given gauge, and a sufficient condition for the existence of spontaneous breaking of a global subgroup of the gauge group in some gauge. As an illustration, we compute numerically, in a lattice version of the Ginzburg-Landau model, the phase boundaries of the theory and the order parameters associated with various symmetries in each phase.
Cuprates and center vortices: A QCD confinement mechanism in a high-T c context
It is determined that the center vortex confinement mechanism, familiar in hadronic physics, may have some relevance to high-T c phenomena. We focus specifically on the transition from the superconducting phase to the pseudogap phase. There is evidence of a vortex liquid in the latter phase, in which the pairing responsible for superconductivity still exists, but superconductivity itself does not. An analogy, drawn from particle physics, may be the Higgs to confinement phase transition in an SU(N) gauge theory, where the confined phase is a vortex liquid, and the Higgs phase is a phase of a broken global Z N symmetry. We illustrate this idea with numerical simulations of a spatially asymmetric U(1) gauge-Higgs model, with lattice artifact monopoles suppressed. We further show the existence of a Higgs (superconductor) to confinement (vortex liquid) phase, explicitly identifying vortices in lattice configurations generated in the confined phase, and showing that they produce an area-law falloff in planar Wilson loops, which may be measurable experimentally. The superconducting phase is a phase of broken global Z 2 symmetry.
Screening without screening: Baryon energy at high baryon density
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Unphysical properties of the static quark-antiquark four-point correlator in Landau gauge
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What symmetry is actually broken in the Higgs phase of a gauge-Higgs theory?
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Finite-density transition line for QCD with 695 MeV dynamical fermions
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Confinement criterion for gauge theories with matter fields
A generalization of the Wilson loop area-law criterion, which is applicable to gauge theories with matter in the fundamental representation of the gauge group, is proposed. This new criterion, like the area law, is stronger than the statement that asymptotic particle states are massive color singlets, which holds even for theories described by the Brout-Englert-Higgs mechanism.
Coulomb flux tube on the lattice
In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious reason that this sum should fall off exponentially with distance from the sources. We show here, however, from numerical simulations in pure SU(2) lattice gauge theory, that the color Coulomb electric field does in fact fall off exponentially with transverse distance away from a line joining static quark-antiquark sources, indicating the existence of a color Coulomb flux tube, and the absence of long-range Coulomb dipole fields.
Relative weights approach to SU(3) gauge theories with dynamical fermions at finite density
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Non-Perturbative Aspects of Thermal QCD
This report summarizes research in theoretical high energy physics carried out under grant support by Mithat Unsal, Jeff Greensite and Maarten Golterman, together with a list of publications generated under this grant.