3,366 research outputs found
Expanding Universe and Dynamical Compactification Using Yang-Mills Instantons
We consider an eight-dimensional Einstein-Yang-Mills theory to explore
whether Yang-Mills instantons formed in extra dimensions can induce the
dynamical instability of our four-dimensional spacetime. We show that the
Yang-Mills instantons in extra dimensions can trigger the expansion of our
universe in four-dimensional spacetime as well as the dynamical
compactification of extra dimensions. We also discuss a possibility to realize
a reheating mechanism via the quantum back-reaction from the contracting tiny
internal space with a smeared instanton.Comment: v3; 26 pages, 6 figures, version to be published in JHE
Magnetic moments of the pentaquarks
We present in this talk a recent analysis for the magnetic moments of the
baryon antidecuplet within the framework of the chiral quark-soliton model with
linear corrections considered. We take into account the mixing of higher
representations to the collective magnetic moment operator, which comes from
the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by
experimental data for the magnetic moments of the baryon octet as well as by
the masses of the octet, decuplet and of . The magnetic moment of
is rather sensitive to the pion-nucleon sigma term and ranges from
to as the sigma term is varied from
to 75 MeV, respectively. On top of them, we obtained that
the strange magnetic moment of the nucleon has the value of n.m. within this scheme and turns out to be almost independent of the
sigma term.Comment: 7 pages, 1 figure, A talk given at International Workshop on
PENTAQUARK04, SPring-8, Hyogo, Japan, 20-23 Jul 200
Strong decays of exotic and non-exotic heavy baryons in the chiral quark-soliton model
In the large limit both heavy and light baryons are described by the
universal mean field, which allows us to relate the properties of heavy baryons
to light ones. With the only input from the decays of light octet baryons (due
to the universality of the chiral mean field), excellent description of strong
decays of both charm and bottom sextets is obtained. The parameter-free
prediction for the widths of exotic anti-decapentaplet
() baryons is also made. The exotic heavy baryons
should be anomalously narrow despite of large phase space available. In
particular, the widths of and , interpreted as
members of -plet, are very small: 0.48~MeV and
1.12~MeV respectivly. This result is in very good agreement with the
measurements of the LHCb Collaboration and provides natural and parameter free
explanation of the LHCb observation that and
have anomalously small widths among five recently observed states.Comment: 13 pages, 3 figures. Discussion on large Nc limit of the decay
couplings added. Acknowledgment added. Version to appear in Physics. Rev.
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