5,571 research outputs found
Exploring Vacuum Structure around Identity-Based Solutions
We explore the vacuum structure in bosonic open string field theory expanded
around an identity-based solution parameterized by . Analyzing the
expanded theory using level truncation approximation up to level 20, we find
that the theory has the tachyon vacuum solution for . We also find
that, at , there exists an unstable vacuum solution in the expanded
theory and the solution is expected to be the perturbative open string vacuum.
These results reasonably support the expectation that the identity-based
solution is a trivial pure gauge configuration for , but it can be
regarded as the tachyon vacuum solution at .Comment: 12 pages, 5 figures; new numerical data up to level (20,60) included;
Contribution to the proceedings of "Second International Conference on String
Field Theory and Related Aspects" (Steklov Mathematical Institute, Moscow,
Russia, April 12-19, 2009
Using Big Bang Nucleosynthesis to Extend CMB Probes of Neutrino Physics
We present calculations showing that upcoming Cosmic Microwave Background
(CMB) experiments will have the power to improve on current constraints on
neutrino masses and provide new limits on neutrino degeneracy parameters. The
latter could surpass those derived from Big Bang Nucleosynthesis (BBN) and the
observationally-inferred primordial helium abundance. These conclusions derive
from our Monte Carlo Markov Chain (MCMC) simulations which incorporate a full
BBN nuclear reaction network. This provides a self-consistent treatment of the
helium abundance, the baryon number, the three individual neutrino degeneracy
parameters and other cosmological parameters. Our analysis focuses on the
effects of gravitational lensing on CMB constraints on neutrino rest mass and
degeneracy parameter. We find for the PLANCK experiment that total (summed)
neutrino mass eV could be ruled out at or better.
Likewise neutrino degeneracy parameters and could be detected or ruled out at
confidence, or better. For POLARBEAR we find that the corresponding detectable
values are , , and , while for EPIC we obtain ,
, and . Our forcast for
EPIC demonstrates that CMB observations have the potential to set constraints
on neutrino degeneracy parameters which are better than BBN-derived limits and
an order of magnitude better than current WMAP-derived limits.Comment: 27 pages, 11 figures, matches published version in JCA
Analytical Tachyonic Lump Solutions in Open Superstring Field Theory
We construct a classical solution in the GSO(-) sector in the framework of a
Wess-Zumino-Witten-like open superstring field theory on a non-BPS D-brane. We
use an su(2) supercurrent, which is obtained by compactifying a direction to a
circle with the critical radius, in order to get analytical tachyonic lump
solutions to the equation of motion. By investigating the action expanded
around a solution we find that it represents a deformation from a non-BPS
D-brane to a D-brane-anti-D-brane system at the critical value of a parameter
which is contained in classical solutions. Although such a process was
discussed in terms of boundary conformal field theory before, our study is
based on open superstring field theory including interaction terms.Comment: 17 pages, references adde
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Enzymatic one-step ring contraction for quinolone biosynthesis.
The 6,6-quinolone scaffolds on which viridicatin-type fungal alkaloids are built are frequently found in metabolites that display useful biological activities. Here we report in vitro and computational analyses leading to the discovery of a hemocyanin-like protein AsqI from the Aspergillus nidulans aspoquinolone biosynthetic pathway that forms viridicatins via a conversion of the cyclopenin-type 6,7-bicyclic system into the viridicatin-type 6,6-bicyclic core through elimination of carbon dioxide and methylamine through methyl isocyanate
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