431 research outputs found
The static quark potential from the gauge invariant Abelian decomposition
We investigate the relationship between colour confinement and topological
structures derived from the gauge invariant Abelian (Cho-Duan-Ge)
decomposition. This Abelian decomposition is made imposing an isometry on a
colour field which selects the Abelian direction; the principle novelty of
our study is that we have defined this field in terms of the eigenvectors of
the Wilson Loop. This allows us to establish an equivalence between the path
ordered integral of the non-Abelian gauge fields with an integral over an
Abelian restricted gauge field which is tractable both theoretically and
numerically in lattice QCD. By using Stokes' theorem, we can relate the Wilson
Loop in terms of a surface integral over a restricted field strength, and show
that the restricted field strength may be dominated by topological structures,
which occur when one of the parameters parametrising the colour field winds
itself around a non-analyticity in the colour field. If they exist, these
objects will lead to an area law scaling for the Wilson Loop and provide a
mechanism for quark confinement. We search for these structures in quenched
lattice QCD. We perform the Abelian decomposition, and find that the restricted
field strength is dominated by peaks on the lattice. Wilson Loops containing
these peaks show a stronger area-Law and thus provide the dominant contribution
to the string tension.Comment: 8 pages, 3 figures; v2 some minor changes (including updated
numerical results), accepted for publication in Physics Letter
Electronic Structure of Electron-doped Sm1.86Ce0.14CuO4: Strong `Pseudo-Gap' Effects, Nodeless Gap and Signatures of Short Range Order
Angle resolved photoemission (ARPES) data from the electron doped cuprate
superconductor SmCeCuO shows a much stronger pseudo-gap
or "hot-spot" effect than that observed in other optimally doped -type
cuprates. Importantly, these effects are strong enough to drive the
zone-diagonal states below the chemical potential, implying that d-wave
superconductivity in this compound would be of a novel "nodeless" gap variety.
The gross features of the Fermi surface topology and low energy electronic
structure are found to be well described by reconstruction of bands by a
order. Comparison of the ARPES and optical data from
the sample shows that the pseudo-gap energy observed in optical data is
consistent with the inter-band transition energy of the model, allowing us to
have a unified picture of pseudo-gap effects. However, the high energy
electronic structure is found to be inconsistent with such a scenario. We show
that a number of these model inconsistencies can be resolved by considering a
short range ordering or inhomogeneous state.Comment: 5 pages, 4 figure
Observation of inhibited electron-ion coupling in strongly heated graphite
Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures (Tele≠Tion) allows unsurpassed insight into the dynamic coupling between electrons and ions through time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter
Rapid generation of long synthetic tandem repeats and its application for analysis in human artificial chromosome formation
Human artificial chromosomes (HACs) provide a unique opportunity to study kinetochore formation and to develop a new generation of vectors with potential in gene therapy. An investigation into the structural and the functional relationship in centromeric tandem repeats in HACs requires the ability to manipulate repeat substructure efficiently. We describe here a new method to rapidly amplify human alphoid tandem repeats of a few hundred base pairs into long DNA arrays up to 120 kb. The method includes rolling-circle amplification (RCA) of repeats in vitro and assembly of the RCA products by in vivo recombination in yeast. The synthetic arrays are competent in HAC formation when transformed into human cells. As short multimers can be easily modified before amplification, this new technique can identify repeat monomer regions critical for kinetochore seeding. The method may have more general application in elucidating the role of other tandem repeats in chromosome organization and dynamics
Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
We investigated electronic structure of 5d transition-metal oxide Sr2IrO4
using angle-resolved photoemission, optical conductivity, and x-ray absorption
measurements and first-principles band calculations. The system was found to be
well described by novel effective total angular momentum Jeff states, in which
relativistic spin-orbit (SO) coupling is fully taken into account under a large
crystal field. Despite of delocalized Ir 5d states, the Jeff-states form so
narrow bands that even a small correlation energy leads to the Jeff = 1/2 Mott
ground state with unique electronic and magnetic behaviors, suggesting a new
class of the Jeff quantum spin driven correlated-electron phenomena.Comment: 12 pages, 4 figure
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