12,605 research outputs found
Effects of a primordial magnetic field with log-normal distribution on the cosmic microwave background
We study the effect of primordial magnetic fields (PMFs) on the anisotropies
of the cosmic microwave background (CMB). We assume the spectrum of PMFs is
described by log-normal distribution which has a characteristic scale, rather
than power-law spectrum. This scale is expected to reflect the generation
mechanisms and our analysis is complementary to previous studies with power-law
spectrum. We calculate power spectra of energy density and Lorentz force of the
log-normal PMFs, and then calculate CMB temperature and polarization angular
power spectra from scalar, vector, and tensor modes of perturbations generated
from such PMFs. By comparing these spectra with WMAP7, QUaD, CBI, Boomerang,
and ACBAR data sets, we find that the current CMB data set places the strongest
constraint at Mpc with the upper limit
nG.Comment: 14 pages, 6 figure
Constraints on the neutrino mass and the primordial magnetic field from the matter density fluctuation parameter
We have made an analysis of limits on the neutrino mass based upon the
formation of large-scale structure in the presence of a primordial magnetic
field. We find that a new upper bound on the neutrino mass is possible based
upon fits to the cosmic microwave background and matter power spectrum when the
existing independent constraints on the matter density fluctuation parameter
and the primordial magnetic field are taken into account.Comment: 6 pages, 2 figures, final version to appear in Phys. Rev. D, to match
proof
Resonant formation of Lambda(1405) by stopped-K- absorption in deuteron
To solve the current debate on the position of the quasi-bound K^-p state,
namely, "Lambda(1405) or Lambda*(1420)", we propose to measure the T_{21} =
T_{Sigma-pi \leftarrow Kbar-N} Sigma-pi invariant-mass spectrum in stopped-K-
absorption in deuteron, since the spectrum, reflecting the soft and hard
deuteron momentum distribution, is expected to have a narrow quasi-free
component with an upper edge of M = 1430 MeV/c^2, followed by a significant
"high-momentum" tail toward the lower mass region, where a resonant formation
of Lambda(1405) of any mass and width in a wide range is revealed. We introduce
a "deviation" spectrum as defined by DEV = OBS (observed or calculated) / QF
(non-resonant quasi-free), in which the resonant component can be seen as an
isolated peak free from the QF shape.Comment: 7 pages, 6 figure
Constraints on the Primordial Magnetic Field from
A primordial magnetic field (PMF) can affect the evolution of density field
fluctuations in the early universe.In this paper we constrain the PMF amplitude
and power spectral index by comparing calculated
density field fluctuations with observational data, i.e. the number density
fluctuation of galaxies.We show that the observational constraints on
cosmological density fluctuations, as parameterized by , lead to
strong constraints on the amplitude and spectral index of the PMF.Comment: 11 pages, 1 figure, accepted for publication as Phys. Rev.
The basic K nuclear cluster K- pp and its enhanced formation in the p + p -> K+ + X reaction
We have studied the structure of K- pp nuclear cluster comprehensively by
solving this three-body system exactly in a variational method starting from
the Ansatz that the Lambda(1405) resonance (Lambda*) is a K-p bound state. We
have found that our original prediction for the presence of K-pp as a compact
bound system with M = 2322 GeV/c), leads to
unusually large self-trapping of Lambda* by the participating proton, since the
Lambda*-p system exists as a compact doorway state propagating to K- pp
(R{Lambda*-p} ~ 1.67 fm).Comment: 18 pages, 14 figures. Phys, Rev. C, in pres
Constraints on the Evolution of the Primordial Magnetic Field from the Small-Scale Cosmic Microwave Background Angular Anisotropy
Recent observations of the cosmic microwave background (CMB) have extended
the measured power spectrum to higher multipoles 1000, and there
appears to be possible evidence for excess power on small angular scales. The
primordial magnetic field (PMF) can strongly affect the CMB power spectrum and
the formation of large scale structure. In this paper, we calculate the CMB
temperature anisotropies generated by including a power-law magnetic field at
the photon last-scattering surface (PLSS). We then deduce an upper limit on the
PMF based on our theoretical analysis of the power excess on small angular
scales. We have taken into account several important effects such as the
modified matter sound speed in the presence of a magnetic field. An upper limit
to the field strength of 4.7 nG at the present scale of 1
Mpc is deduced. This is obtained by comparing the calculated theoretical result
including the Sunyaev-Zeldovich (SZ) effect with recent observed data on the
small-scale CMB anisotropies from the
(WMAP), the Cosmic Background Imager (CBI), and the Arcminute Cosmology
Bolometer Array Receiver (ACBAR). We discuss several possible mechanisms for
the generation and evolution of the PMF.Comment: 27 pages, 4 figures, accepted to ApJ April 10, 200
Energy dependence of -"" effective potential derived from coupled-channel Green's function
We investigate the energy dependence of a single-channel effective potential
between the and the ""-core nucleus, which can be obtained as an
-"" equivalent local potential from a coupled-channel model for
- systems. It turns out that the imaginary part of
the resultant potential near the decay threshold can well
approximate the phase space suppression factor of
decay modes. The effects on the pole position of the state in
the channel are also discussed.Comment: 4 pages, 2 figures, Proceedings of the International Conference on
Exotic Atoms and Related Topics (EXA2011), September 5-9, 2011, Wien,
Austria, to appear in Hyperfine Interaction
Palatable Meal Anticipation in Mice
The ability to sense time and anticipate events is a critical skill in nature. Most efforts to understand the neural and molecular mechanisms of anticipatory behavior in rodents rely on daily restricted food access, which induces a robust increase of locomotor activity in anticipation of daily meal time. Interestingly, rats also show increased activity in anticipation of a daily palatable meal even when they have an ample food supply, suggesting a role for brain reward systems in anticipatory behavior, and providing an alternate model by which to study the neurobiology of anticipation in species, such as mice, that are less well adapted to "stuff and starve" feeding schedules. To extend this model to mice, and exploit molecular genetic resources available for that species, we tested the ability of wild-type mice to anticipate a daily palatable meal. We observed that mice with free access to regular chow and limited access to highly palatable snacks of chocolate or “Fruit Crunchies” avidly consumed the snack but did not show anticipatory locomotor activity as measured by running wheels or video-based behavioral analysis. However, male mice receiving a snack of high fat chow did show increased food bin entry prior to access time and a modest increase in activity in the two hours preceding the scheduled meal. Interestingly, female mice did not show anticipation of a daily high fat meal but did show increased activity at scheduled mealtime when that meal was withdrawn. These results indicate that anticipation of a scheduled food reward in mice is behavior, diet, and gender specific
The Reionization History and Early Metal Enrichment inferred from the Gamma-Ray Burst Rate
Based on the gamma-ray burst (GRB) event rate at redshifts of , which is assessed by the spectral peak energy-to-luminosity relation
recently found by Yonetoku et al., we observationally derive the star formation
rate (SFR) for Pop III stars in a high redshift universe. As a result, we find
that Pop III stars could form continuously at . Using the
derived Pop III SFR, we attempt to estimate the ultraviolet (UV) photon
emission rate at in which redshift range no observational
information has been hitherto obtained on ionizing radiation intensity. We find
that the UV emissivity at can make a noticeable contribution
to the early reionization. The maximal emissivity is higher than the level
required to keep ionizing the intergalactic matter at .
However, if the escape fraction of ionizing photons from Pop III objects is
smaller than 10%, then the IGM can be neutralized at some redshift, which may
lead to the double reionization. As for the enrichment, the ejection of all
metals synthesized in Pop III objects is marginally consistent with the IGM
metallicity, although the confinement of metals in Pop III objects can reduce
the enrichment significantly.Comment: 12 pages, 2 figures, ApJL accepte
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