2,131 research outputs found
Renormalization Group Approach to Cosmological Back Reaction Problems
We investigated the back reaction of cosmological perturbations on the
evolution of the universe using the second order perturbation of the Einstein's
equation. To incorporate the back reaction effect due to the inhomogeneity into
the framework of the cosmological perturbation, we used the renormalization
group method. The second order zero mode solution which appears by the
non-linearities of the Einstein's equation is regarded as a secular term of the
perturbative expansion, we renormalized a constant of integration contained in
the background solution and absorbed the secular term to this constant. For a
dust dominated universe, using the second order gauge invariant quantity, we
derived the renormalization group equation which determines the effective
dynamics of the Friedman-Robertson-Walker universe with the back reaction
effect in a gauge invariant manner. We obtained the solution of the
renormalization group equation and found that perturbations of the scalar mode
and the long wavelength tensor mode works as positive spatial curvature, and
the short wavelength tensor mode as radiation fluid.Comment: 18 pages, revtex, to appear in Phys. Rev.
Infestações parasitárias em surubim híbrido (Pseudoplatystoma reticulatum x P. corruscans ) durante a fase inicial de criação.
Lagrangian description of fluid flow with pressure in relativistic cosmology
The Lagrangian description of fluid flow in relativistic cosmology is
extended to the case of flow accelerated by pressure. In the description, the
entropy and the vorticity are obtained exactly for the barotropic equation of
state. In order to determine the metric, the Einstein equation is solved
perturbatively, when metric fluctuations are small but entropy inhomogeneities
are large. Thus, the present formalism is applicable to the case when the
inhomogeneities are small in the large scale but locally nonlinear.Comment: 11 pages (RevTeX); accepted for publication in Phys. Rev.
Universality of Bias- and Temperature-induced Dephasing in Ballistic Electronic Interferometers
We performed a transport measurement in a ballistic Aharonov-Bohm ring and a
Fabry-Perot type interferometer. In both cases we found that the interference
signal is reversed at a certain bias voltage and that the visibility decays
exponentially as a function of temperature, being in a strong analogy with
recent reports on the electronic Mach-Zehnder interferometers. By analyzing the
data including those in the previous works, the energy scales that characterize
the dephasing are found to be dominantly dependent on the interferometer size,
implying the presence of a universal behavior in ballistic interferometers in
both linear and non-linear transport regimes.Comment: 4 pages, 4 figures, accepted for publication in PRB rapid com
Effects of Metabotropic Glutamate Receptor 3 Genotype on Phonetic Mismatch Negativity
BACKGROUND: The genetic and molecular basis of glutamatergic dysfunction is one key to understand schizophrenia, with the identification of an intermediate phenotype being an essential step. Mismatch negativity (MMN) or its magnetic counterpart, magnetic mismatch field (MMF) is an index of preattentive change detection processes in the auditory cortex and is generated through glutamatergic neurotransmission. We have previously shown that MMN/MMF in response to phoneme change is markedly reduced in schizophrenia. Variations in metabotropic glutamate receptor (GRM3) may be associated with schizophrenia, and has been shown to affect cortical function. Here we investigated the effect of GRM3 genotypes on phonetic MMF in healthy men. METHODS: MMF in response to phoneme change was recorded using magnetoencephalography in 41 right-handed healthy Japanese men. Based on previous genetic association studies in schizophrenia, 4 candidate SNPs (rs6465084, rs2299225, rs1468412, rs274622) were genotyped. RESULTS: GRM3 rs274622 genotype variations significantly predicted MMF strengths (p = 0.009), with C carriers exhibiting significantly larger MMF strengths in both hemispheres compared to the TT subjects. CONCLUSIONS: These results suggest that variations in GRM3 genotype modulate the auditory cortical response to phoneme change in humans. MMN/MMF, particularly those in response to speech sounds, may be a promising and sensitive intermediate phenotype for clarifying glutamatergic dysfunction in schizophrenia
Effect of deconfinement on resonant transport in quantum wires
The effect of deconfinement due to finite band offsets on transport through
quantum wires with two constrictions is investigated. It is shown that the
increase in resonance linewidth becomes increasingly important as the size is
reduced and ultimately places an upper limit on the energy (temperature) scale
for which resonances may be observed.Comment: 6 pages, 6 postscript files with figures; uses REVTe
Parasitologicalassessment and host-parasite relationship in farmed Cachara catfish fingerlings (Pseudoplatystoma reticulatum Eigenmann & Eigenmann 1889), Mato Grosso do Sul, Brazil.
Farmed fingerlings of South American catfish are frequently exposed to several parasites, but little information is available for implementing health programs for control and prevention of parasitic diseases in the hatcheries. This study evaluated the parasitic fauna of cachara catfish fingerlings (Pseudoplatystoma reticulatum Eingenmann & Eigenmann, 1889) and the hostparasite relationship during the early stages of rearing. A total of 302 cachara fingerlings were used for parasitic diagnosis and histopathological analysis. Ichthyophthirius multifiliis and Trichodina heterodentata were diagnosed as the most prevalent parasites, followed by Cryptobia sp., Henneguya sp., Monogenea and Nematoda. There was a positive correlation between the size of the fish and the mean intensity of parasitism by I. multifiliis. Proliferation of mucus cells, club cells, multifocal area of degeneration, epithelial necrosis on the body surface, skin ulceration, fusion of secondary gill lamellae and inflammatory infiltration were observed in I. multifiliisinfected fish. Ciliated protozoans were the main etiological agents diagnosed, and the cachara (P.
reticulatum) is a new host for T. heterodentata. In addition, ichthyophthiriasis induced severe tissue damage thus making the fingerlings susceptible to opportunistic infections.Los alevines de bagres del Sur de América en cautiverio están frecuentemente expuestos a muchos parásitos, pero poca información es evaluada para implementar programa de salud para control y prevención de enfermedades en criaderos. Este estudio evaluó la fauna de parásitos de alevines de cachara (Pseudoplatystoma reticulatum Eingenmann & Eingenmann, 1889) y la relación huésped-parásito durante las fases iníciales de cultivo. Un total de 302 alevines fueran sometidos a
diagnóstico y análisis histopatológicos. Ichthyophthirius multifiliis y Trichodina heterodentata fueran diagnosticados como los parásitos mas prevalentes, seguidos de Cryptobia sp., Henneguya sp., Monogenea y Nematoda. Ha sido observada una correlación positiva entre la longitud de los peces y la intensidad promedio de I. multifiliis. Proliferación de células de moco, células club, áreas multifocales de degeneración, necrosis epitelial en la superficie del cuerpo, ulceración de piel, fusión de laminillas branquiales secundarias e infiltración inflamatoria fueron observados en peces infectados por I. multifiliis. Los protozoarios ciliados fueran los agentes etiológicos más importantes y el cachara (P. reticulatum) es un nuevo huésped para T. heterodentata. En adición, la ictioftiriasis indujo un daño severo favoreciendo las infecciones oportunistas en los alevines
Phenomenology of Higgs bosons in the Zee-Model
To generate small neutrino masses radiatively, the Zee-model introduces two
Higgs doublets and one weak-singlet charged Higgs boson to its Higgs sector.
From analyzing the renormalization group equations, we determine the
possibile range of the lightest CP-even Higgs boson () mass and the Higgs
boson self-couplings as a function of the cut-off scale beyond which either
some of the coupling constants are strong enough to invalidate the perturbative
analysis or the stability of the electroweak vacuum is no longer guaranteed.
Using the results obtained from the above analysis, we find that the singlet
charged Higgs boson can significantly modify the partial decay width of via radiative corrections, and its collider phenomenology can
also be drastically different from that of the charged Higgs bosons in the
usual two-Higgs-doublet models.Comment: Added a paragraph and a figure in Section V, corrected typos, added
references. (RevTeX, 45 pages, 16 figures included.) To appear in Physical
Review
The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)
This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows
Newtonian Cosmology in Lagrangian Formulation: Foundations and Perturbation Theory
The ``Newtonian'' theory of spatially unbounded, self--gravitating,
pressureless continua in Lagrangian form is reconsidered. Following a review of
the pertinent kinematics, we present alternative formulations of the Lagrangian
evolution equations and establish conditions for the equivalence of the
Lagrangian and Eulerian representations. We then distinguish open models based
on Euclidean space from closed models based (without loss of generality)
on a flat torus \T^3. Using a simple averaging method we show that the
spatially averaged variables of an inhomogeneous toroidal model form a
spatially homogeneous ``background'' model and that the averages of open
models, if they exist at all, in general do not obey the dynamical laws of
homogeneous models. We then specialize to those inhomogeneous toroidal models
whose (unique) backgrounds have a Hubble flow, and derive Lagrangian evolution
equations which govern the (conformally rescaled) displacement of the
inhomogeneous flow with respect to its homogeneous background. Finally, we set
up an iteration scheme and prove that the resulting equations have unique
solutions at any order for given initial data, while for open models there
exist infinitely many different solutions for given data.Comment: submitted to G.R.G., TeX 30 pages; AEI preprint 01
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