11,195 research outputs found
Inflationary NonGaussianity from Thermal Fluctuations
We calculate the contribution of the fluctuations with the thermal origin to
the inflationary nonGaussianity. We find that even a small component of
radiation can lead to a large nonGaussianity. We show that this thermal
nonGaussianity always has positive . We illustrate our result in
the chain inflation model and the very weakly dissipative warm inflation model.
We show that is general in such models. If we allow
modified equation of state, or some decoupling effects, the large thermal
nonGaussianity of order or even can be
produced. We also show that the power spectrum of chain inflation should have a
thermal origin. In the Appendix A, we made a clarification on the different
conventions used in the literature related to the calculation of .Comment: 20 pages, 1 figure. v2, v3: references and acknowledgments update
Non-commutative Geometry Modified Non-Gaussianities of Cosmological Perturbation
We investigate the noncommutative effect on the non-Gaussianities of
primordial cosmological perturbation. In the lowest order of string length and
slow-roll parameter, we find that in the models with small speed of sound the
noncommutative modifications could be observable if assuming a relatively low
string scale. In particular, the dominant modification of non-Gaussianity
estimator f_{NL} could reach O(1) in DBI inflation and K-inflation. The
corrections are sensitive to the speed of sound and the choice of string length
scale. Moreover the shapes of the corrected non-Gaussianities are distinct from
that of ordinary ones.Comment: 26 pages, 3 figures Added references, changed conten
Generalized Space-time Noncommutative Inflation
We study the noncommutative inflation with a time-dependent noncommutativity
between space and time. From the numerical analysis of power law inflation,
there are clues that the CMB spectrum indicates a nonconstant noncommutative
inflation. Then we extend our treatment to the inflation models with more
general noncommutativity and find that the scalar perturbation power spectrum
depends sensitively on the time varying of the spacetime noncommutativity. This
stringy effect may be probed in the future cosmological observations.Comment: 15 pages, 2 figure
Dyson-Schwinger Equations with a Parameterized Metric
We construct and solve the Dyson-Schwinger equation (DSE) of quark propagator
with a parameterized metric, which connects the Euclidean metric with the
Minkowskian one. We show, in some models, the Minkowskian vacuum is different
from the Euclidean vacuum. The usual analytic continuation of Green function
does not make sense in these cases. While with the algorithm we proposed and
the quark-gluon vertex ansatz which preserves the Ward-Takahashi identity, the
vacuum keeps being unchanged in the evolution of the metric. In this case,
analytic continuation becomes meaningful and can be fully carried out.Comment: 10 pages, 7 figures. To appear in Physical Review
Hanle detection for optical clocks
Considering the strong inhomogeneous spatial polarization and intensity
distribution of spontaneous decay fluorescence due to the Hanle effect, we
propose and demonstrate a universe Hanle detection configuration of
electron-shelving method for optical clocks. Experimental results from Ca
atomic beam optical frequency standard with 423 nm electron-shelving method
show that a designed Hanle detection geometry with optimized magnetic field
direction, detection laser beam propagation and polarization direction, and
detector position can improve the fluorescence collection rate by more than one
order of magnitude comparing with that of inefficient geometry. With the fixed
423 nm fluorescence, the improved 657 nm optical frequency standard signal
intensity is presented. And the potential application of the Hanle detection
geometry designed for facilitating the fluorescence collection for optical
lattice clock with a limited solid angle of the fluorescence collection has
been discussed. This Hanle detection configuration is also effective for ion
detection in ion optical clock and quantum information experiments. Besides, a
cylinder fluorescence collection structure is designed to increase the solid
angle of the fluorescence collection in Ca atomic beam optical frequency
standard.Comment: 5 pages, 6 figure
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