3,265 research outputs found
An equivalent expression of Z2 Topological Invariant for band insulators using Non-Abelian Berry's connection
We introduce a new expression for the Z2 topological invariant of band
insulators using non- Abelian Berry's connection. Our expression can identify
the topological nature of a general band insulator without any of the gauge
fixing problems that plague the concrete implementation of previous invariants.
The new expression can be derived from the "partner switching" of the Wannier
function center during time reversal pumping and is thus equivalent to the Z2
topological invariant proposed by Kane and Mele.Comment: 14 pages, 8 figure
Tentative evidence of spatially extended GeV emission from SS433/W50
We analyze 10 years of Fermi-LAT data towards the SS433/W50 region. With the
latest source catalog and diffuse background models, the gamma-ray excess from
SS433/W50 is detected with a significance of 6{\sigma} in the photon energy
range of 500 MeV - 10 GeV. Our analysis indicates that an extended flat disk
morphology is preferred over a point-source description, suggesting that the
GeV emission region is much larger than that of the TeV emission detected by
HAWC. The size of the GeV emission is instead consistent with the extent of the
radio nebula W50, a supernova remnant being distorted by the jets, so we
suggest that the GeV emission may originate from this supernova remnant. The
spectral result of the GeV emission is also consistent with an supernova
remnant origin. We also derive the GeV flux upper limits on the TeV emission
region, which put moderate constrains on the leptonic models to explain the
multiwavelength data.Comment: 7 pages, 4 figures, accepted for publication in A&
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