1,484 research outputs found
Supersymmetry Breaking and Gravitino Production after Inflation in Modular Invariant Supergravity
By using a string-inspired modular invariant supergravity, which was proved
well to explain WMAP observations appropriately, a mechanism of supersymmetry
breaking (SSB) and Gravitino Production just after the end of inflation are
investigated. Supersymmetry is broken mainly by F-term of the inflaton
superfield and the Goldstino is identified to be inflatino in this model, which
fact is shown numerically. By using the canonically normalized and diagonalized
scalars, the decay rates of these fields are calculated, for both the and
into gravitinos. Non-thermal production of gravitinos is not generated from
the inflaton (dilaton), since the inflaton mass is lighter than gravitino, but
they are produced by the decay of modular field and scalar field .
Because the reheating temperature is about order GeV
and the mass of gravitino is GeV, it is not reproduced
after the reheating of the universe. The gravitinos are produced almost
instantly just after the end of inflation through and , not from
inflaton. Because the decay time appears very rapid, gravitinos disappear
before the BBN stage of the universe. The effects of the lightest
supersymmetric particles (LSP) produced by gravitinos may be important to
investigate more carefully, if the LSP's are the candidate of dark matter.Comment: 11 pages, 1 figure
Dilatonic Inflation, Gravitino and Reheating in Modified Modular invariant Supergravity
A new modified string-inspired modular invariant supergravity model is
proposed and is applied to realize the slow roll inflation in Einstein frame,
so that the model explains WMAP observations very well. Gravitino mass and
their production rate from scalar fields are estimated at certain values of
parameters in the model. Seven cases of parameter choices are discussed here,
among which some examples show the possibility of observation of gauginos by
LHC experiments, which will give some hints of identity of dark matters. The
reheating temperature, which is estimated by the stability condition of
Boltzmann equation by using the decay rates of the dilaton into gauginos,
is lower than the mass of gravitino. Therefore no thermal reproduction of
gravitinos happens. The ratio between the scalar and tensor power spectrum is
predicted to be almost the same for the seven cases under study, and its value
seems in the range possibly observed by the Planck
satellite soon. The plausible supergravity model of inflation, which will be
described here, will open the hope to construct a realistic theory of particles
and cosmology in this framework, including yet undetected objects.Comment: 12 pages, 4 figures, 2 table
Angular Power Spectrum in Modular Invariant Inflation Model
We propose a scalar potential of inflation, motivated by modular invariant
supergravity, and compute the angular power spectra of the adiabatic density
perturbations that result from this model. The potential consists of three
scalar fields, S, Y and T, together with two free parameters. By fitting the
parameters to cosmological data at the fixed point T=1, we find that the
potential behaves like the single-field potential of S, which slowly rolls down
along the minimized trajectory in Y. We further show that the inflation
predictions corresponding to this potential provide a good fit to the recent
three-year WMAP data, e.g. the spectral index n_s = 0.951. The TT and TE
angular power spectra obtained from our model almost completely coincide with
the corresponding results obtained from the \LambdaCDM model. We conclude that
our model is considered to be an adequate theory of inflation that explains the
present data, although the theoretical basis of this model should be further
explicated.Comment: 8 pages, 8 figures and 1 tabl
Geomagnetically Trapped Particles and Soft Errors on IC Observed in a Satellite
開始ページ、終了ページ: 冊子体のページ付
Functional ultrasound reveals effects of MRI acoustic noise on brain function
Loud acoustic noise from the scanner during functional magnetic resonance imaging (fMRI) can affect functional connectivity (FC) observed in the resting state, but the exact effect of the MRI acoustic noise on resting state FC is not well understood. Functional ultrasound (fUS) is a neuroimaging method that visualizes brain activity based on relative cerebral blood volume (rCBV), a similar neurovascular coupling response to that measured by fMRI, but without the audible acoustic noise. In this study, we investigated the effects of different acoustic noise levels (silent, 80 dB, and 110 dB) on FC by measuring resting state fUS (rsfUS) in awake mice in an environment similar to fMRI measurement. Then, we compared the results to those of resting state fMRI (rsfMRI) conducted using an 11.7 Tesla scanner. RsfUS experiments revealed a significant reduction in FC between the retrosplenial dysgranular and auditory cortexes (0.56 ± 0.07 at silence vs 0.05 ± 0.05 at 110 dB, p=.01) and a significant increase in FC anticorrelation between the infralimbic and motor cortexes (−0.21 ± 0.08 at silence vs −0.47 ± 0.04 at 110 dB, p=.017) as acoustic noise increased from silence to 80 dB and 110 dB, with increased consistency of FC patterns between rsfUS and rsfMRI being found with the louder noise conditions. Event-related auditory stimulation experiments using fUS showed strong positive rCBV changes (16.5% ± 2.9% at 110 dB) in the auditory cortex, and negative rCBV changes (−6.7% ± 0.8% at 110 dB) in the motor cortex, both being constituents of the brain network that was altered by the presence of acoustic noise in the resting state experiments. Anticorrelation between constituent brain regions of the default mode network (such as the infralimbic cortex) and those of task-positive sensorimotor networks (such as the motor cortex) is known to be an important feature of brain network antagonism, and has been studied as a biological marker of brain disfunction and disease. This study suggests that attention should be paid to the acoustic noise level when using rsfMRI to evaluate the anticorrelation between the default mode network and task-positive sensorimotor network.journal articl
- …