6,871 research outputs found
The progenitor of the 'born-again' core V605 Aql and the relation to its younger twin V4334 Sgr
We derived the properties of V605 Aql before the final helium flash pulse by
studying its surrounding PN A58. Photoionizing models of our spectral data
together with a new distance estimate and a closer look at the recombination
timescales lead to a consistent model. Comparing our findings with the only
hydrogen-poor twin, namely Sakurai's Object, we conclude that these born-again
objects have normal PNe core masses. We are able to prove V605 Aql indeed to
be, similar to V4332 Sgr, a very late thermal pulse object and to put
constraints for the evolutionary time scales for the transition back to the
AGB.Comment: LaTeX, 5 pages, 3 figures, Accepted in Astron. & Astrophy
The cancellation of worldsheet anomalies in the D=10 Green--Schwarz heterotic string sigma--model
We determine the two--dimensional Weyl, Lorentz and --anomalies in
the Green--Schwarz heterotic string sigma--model, in an
-Lorentz covariant background gauge, and prove their cancellation.Comment: 12 pages, Plain TeX, no figure
The Three-User Finite-Field Multi-Way Relay Channel with Correlated Sources
This paper studies the three-user finite-field multi-way relay channel, where
the users exchange messages via a relay. The messages are arbitrarily
correlated, and the finite-field channel is linear and is subject to additive
noise of arbitrary distribution. The problem is to determine the minimum
achievable source-channel rate, defined as channel uses per source symbol
needed for reliable communication. We combine Slepian-Wolf source coding and
functional-decode-forward channel coding to obtain the solution for two classes
of source and channel combinations. Furthermore, for correlated sources that
have their common information equal their mutual information, we propose a new
coding scheme to achieve the minimum source-channel rate.Comment: Author's final version (accepted and to appear in IEEE Transactions
on Communications
- …