29,727 research outputs found
The Kagome Antiferromagnet: A Schwinger-Boson Mean-Field Theory Study
The Heisenberg antiferromagnet on the Kagom\'{e} lattice is studied in the
framework of Schwinger-boson mean-field theory. Two solutions with different
symmetries are presented. One solution gives a conventional quantum state with
order for all spin values. Another gives a gapped spin liquid
state for spin and a mixed state with both and
orders for spin . We emphasize that the mixed
state exhibits two sets of peaks in the static spin structure factor. And for
the case of spin , the gap value we obtained is consistent with the
previous numerical calculations by other means. We also discuss the
thermodynamic quantities such as the specific heat and magnetic susceptibility
at low temperatures and show that our result is in a good agreement with the
Mermin-Wagner theorem.Comment: 9 pages, 5 figure
Multiple G-It\^{o} integral in the G-expectation space
In this paper, motivated by mathematic finance we introduce the multiple
G-It\^{o} integral in the G-expectation space, then investigate how to
calculate. We get the the relationship between Hermite polynomials and multiple
G-It\^{o} integrals which is a natural extension of the classical result
obtained by It\^{o} in 1951.Comment: 9 page
Dichotomy in the Dynamical Status of Massive Cores in Orion
To study the evolution of high mass cores, we have searched for evidence of
collapse motions in a large sample of starless cores in the Orion molecular
cloud. We used the Caltech Submillimeter Observatory telescope to obtain
spectra of the optically thin (\H13CO+) and optically thick (\HCO+) high
density tracer molecules in 27 cores with masses 1 \Ms. The red- and
blue-asymmetries seen in the line profiles of the optically thick line with
respect to the optically thin line indicate that 2/3 of these cores are not
static. We detect evidence for infall (inward motions) in 9 cores and outward
motions for 10 cores, suggesting a dichotomy in the kinematic state of the
non-static cores in this sample. Our results provide an important observational
constraint on the fraction of collapsing (inward motions) versus non-collapsing
(re-expanding) cores for comparison with model simulations.Comment: 9 pages, 2 Figures. To appear in ApJ(Letters
- …