9,788 research outputs found
The Algebra of Strand Splitting. II. A Presentation for the Braid Group on One Strand
Presentations are computed for a braided version BV of Thompson's group V and
for V itself showing that there is an Artin group/Coxeter group relation
between them. The presentation for V is obtained from that for BV by declaring
all that all generators are involutions.Comment: 15 page
The Algebra of Strand Splitting. I. A Braided Version of Thompson's Group V
We construct a braided version of Thompson's group V.Comment: 27 page
MUSE Illuminates Channels for Lyman Continuum Escape in the Halo of SBS 0335-52E
We report on the discovery of ionised gas filaments in the circum-galactic
halo of the extremely metal-poor compact starburst SBS 0335-052E in a 1.5h
integration with the MUSE integral-field spectrograph. We detect these features
in H and [OIII] emission down to surface-brightness levels of erg scmarcsec. The filaments have
projected diameters of 2.1 kpc and extend more than 9 kpc to the north and
north-west from the main stellar body. We also detect extended nebular HeII
4686 emission that brightens towards the north-west at the rim of a
star-burst driven super-shell, suggestive of a locally enhanced UV radiation
field due to shocks. We also present a velocity field of the ionised gas. The
filaments appear to connect seamlessly in velocity space to the kinematical
disturbances caused by the shell. Similar to high- star-forming galaxies,
the ionised gas in this galaxy is dispersion dominated. We argue that the
filaments were created via feedback from the starburst and that these ionised
structures in the halo may act as escape channels for Lyman continuum radiation
in this gas-rich system.Comment: Revised version after peer review. Accepted for publication in A&A
letter
Phase Diagram of One-Dimensional Extended Hubbard Model at Half Filling
We reexamine the ground-state phase diagram of the one-dimensional
half-filled Hubbard model with on-site and nearest-neighbor repulsive
interactions. We calculate second-order corrections to coupling constants in
the g-ology to show that the bond-charge-density-wave (BCDW) phase exists for
weak couplings in between the charge density wave (CDW) and spin density wave
(SDW) phases. We find that the umklapp scattering of parallel-spin electrons
destabilizes the BCDW state and gives rise to a bicritical point where the
CDW-BCDW and SDW-BCDW continuous-transition lines merge into the CDW-SDW
first-order transition line.Comment: 4 pages, 3 figure
Invariant Peano curves of expanding Thurston maps
We consider Thurston maps, i.e., branched covering maps
that are postcritically finite. In addition, we assume that is expanding in
a suitable sense. It is shown that each sufficiently high iterate of
is semi-conjugate to , where is equal to the
degree of . More precisely, for such an we construct a Peano curve
(onto), such that
(for all ).Comment: 63 pages, 12 figure
Mechanism of CDW-SDW Transition in One Dimension
The phase transition between charge- and spin-density-wave (CDW, SDW) phases
is studied in the one-dimensional extended Hubbard model at half-filling. We
discuss whether the transition can be described by the Gaussian and the
spin-gap transitions under charge-spin separation, or by a direct CDW-SDW
transition. We determine these phase boundaries by level crossings of
excitation spectra which are identified according to discrete symmetries of
wave functions. We conclude that the Gaussian and the spin-gap transitions take
place separately from weak- to intermediate-coupling region. This means that
the third phase exists between the CDW and the SDW states. Our results are also
consistent with those of the strong-coupling perturbative expansion and of the
direct evaluation of order parameters.Comment: 5 pages(REVTeX), 5 figures(EPS), 1 table, also available from
http://wwwsoc.nacsis.ac.jp/jps/jpsj/1999/p68a/p68a42/p68a42h/p68a42h.htm
Umklapp scattering of pairs in BCS superconductivity theory
The BCS theory of superconductivity is extended to recognize pairing of
electrons by both normal and umklapp scattering. Application of the variational
approach shows that coexistence of normal and umklapp scattering frustrates
superconductivity.Comment: 9 pages, 5 figures. to be published in Journal of Physics: Condensed
Matte
Techniques for measuring atmospheric aerosols at the High Resolution Fly's Eye experiment
We describe several techniques developed by the High Resolution Fly's Eye
experiment for measuring aerosol vertical optical depth, aerosol horizontal
attenuation length, and aerosol phase function. The techniques are based on
measurements of side-scattered light generated by a steerable ultraviolet laser
and collected by an optical detector designed to measure fluorescence light
from cosmic-ray air showers. We also present a technique to cross-check the
aerosol optical depth measurement using air showers observed in stereo. These
methods can be used by future air fluorescence experiments.Comment: Accepted for publication in Astroparticle Physics Journal 16 pages, 9
figure
Magnetic Fluctuations in a Charge Ordered State of the One-Dimensional Extended Hubbard Model with a Half-Filled Band
Magnetic properties in a charge ordered state are examined for the extended
Hubbard model at half-filling. Magnetic excitations, magnetic susceptibilities
and a nuclear spin relaxation rate are calculated with taking account of
fluctuations around the mean-field solution. The relevance of the present
results to the observation in the 1:1 organic conductors, (TTM-TTP)I, is
discussed.Comment: 4 pages, 3 figures, to be published in J. Phys. Soc. Jpn. Vol.71
(2002) No.
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