2,700 research outputs found
CMB statistical anisotropy from noncommutative gravitational waves
Primordial statistical anisotropy is a key indicator to investigate early
Universe models and has been probed by the cosmic microwave background (CMB)
anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated
from anisotropic gravitational waves, parametrised by , where
is the usual scale-invariant power spectrum. Such anisotropic
tensor fluctuations may arise from an inflationary model with noncommutativity
of fields. It is verified that in this model, an isotropic component and a
quadrupole asymmetry with are created and
hence highly red-tilted off-diagonal components arise in the CMB power spectra,
namely in , , and , and in and . We find that B-mode polarisation is more
sensitive to such signals than temperature and E-mode polarisation due to the
smallness of large-scale cosmic variance and we can potentially measure and at 68% CL in a cosmic-variance-limited experiment. Such
a level of signal may be measured in a PRISM like experiment, while the
instrumental noise contaminates it in the experiment. These results
imply that it is impossible to measure the noncommutative parameter if it is
small enough for the perturbative treatment to be valid. Our formalism and
methodology for dealing with the CMB tensor statistical anisotropy are general
and straightforwardly applicable to other early Universe models.Comment: 13 pages, 2 figures, 1 table. Accepted for publication in JCA
Observable non-gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
In any realistic particle physics model of inflation, the inflaton can be
expected to couple to other fields. We consider a model with a dilaton-like
coupling between a U(1) gauge field and a scalar inflaton. We show that this
coupling can result in observable non-gaussianity, even in the conventional
regime where inflation is supported by a single scalar slowly rolling on a
smooth potential: the time dependent inflaton condensate leads to amplification
of the large-scale gauge field fluctuations, which can feed-back into the
scalar/tensor cosmological perturbations. In the squeezed limit, the resulting
bispectrum is close to the local one, but it shows a sizable and characteristic
quadrupolar dependence on the angle between the shorter and the larger modes in
the correlation. Observable non-gaussianity is obtained in a regime where
perturbation theory is under control. If the gauge field is identified with the
electromagnetic field, the model that we study is a realization of the
magnetogenesis idea originally proposed by Ratra, and widely studied. This
identification (which is not necessary for the non-gaussianity production) is
however problematic in light of a strong coupling problem already noted in the
literature.Comment: 28 pages, no figures. Final versio
A Quantum Deformation of the Virasoro Algebra and the Macdonald Symmetric Functions
A quantum deformation of the Virasoro algebra is defined. The Kac
determinants at arbitrary levels are conjectured. We construct a bosonic
realization of the quantum deformed Virasoro algebra. Singular vectors are
expressed by the Macdonald symmetric functions. This is proved by constructing
screening currents acting on the bosonic Fock space.Comment: 15 pages, latex fil
Noncommutative with Quantized Cosmological Constant
We examine a recent deformation of three-dimensional anti-deSitter gravity
based on noncommutative Chern-Simons theory with gauge group . In addition to a noncommutative analogue of 3D gravity, the theory
contains two addition gauge fields which decouple in the commutative limit. It
is well known that the level is quantized in noncommutative Chern-Simons
theory. Here it implies that the cosmological constant goes like minus one over
an integer-squared. We construct the noncommutative vacuum by applying
a Seiberg-Witten map from the commutative case. The procedure is repeated for
the case of a conical space resulting from a massive spinning particle.Comment: 16 p
Statistical Mechanics of Charged Particles in Einstein-Maxwell-Scalar Theory
We consider an -body system of charged particle coupled to gravitational,
electromagnetic, and scalar fields. The metric on moduli space for the system
can be considered if a relation among the charges and mass is satisfied, which
includes the BPS relation for monopoles and the extreme condition for charged
black holes. Using the metric on moduli space in the long distance
approximation, we study the statistical mechanics of the charged particles at
low velocities. The partition function is evaluated as the leading order of the
large expansion, where is the spatial dimension of the system and will
be substituted finally as .Comment: 11 pages, RevTeX3.
Spin Nutation Induced by Atomic Motion in a Magnetic Lattice
An atom moving in a spatially periodic field experiences a temporary periodic
perturbation and undergoes a resonance transition between atomic internal
states when the transition frequency is equal to the atomic velocity divided by
the field period. We demonstrated that spin nutation was induced by this
resonant transition in a polarized rubidium (Rb) atomic beam passing through a
magnetic lattice. The lattice was produced by current flowing through an array
of parallel wires crossing the beam. This array structure, reminiscent of a
multiwire chamber for particle detection, allowed the Rb beam to pass through
the lattice at a variety of incident angles. The dephasing of spin nutation was
reduced by varying the incident angle.Comment: 11 pages, 4 figures, submitted to Phys. Rev.
Metabolic microenvironmental control by photosynthetic biofilms under changing macroenvironmental temperature and pH conditions
Ex situ microelectrode experiments, using cyanobacterial biofilms from karst water creeks, were conducted under various pH, temperature, and constant-alkalinity conditions to investigate the effects of changing environmental parameters on cyanobacterial photosynthesis-induced calcification. Microenvironmental chemical conditions around calcifying sites were controlled by metabolic activity over a wide range of photosynthesis and respiration rates, with little influence from overlying water conditions. Regardless of overlying water pH levels (from 7.8 to 8.9), pH at the biofilm surface was approximately 9.4 in the light and 7.8 in the dark. The same trend was observed at various temperatures (4°C and 17°C). Biological processes control the calcium carbonate saturation state (Ω) in these and similar systems and are able to maintain Ω at approximately constant levels over relatively wide environmental fluctuations. Temperature did, however, have an effect on calcification rate. Calcium flux in this system is limited by its diffusion coefficient, resulting in a higher calcium flux (calcification and dissolution) at higher temperatures, despite the constant, biologically mediated pH. The ability of biological systems to mitigate the effects of environmental perturbation is an important factor that must be considered when attempting to predict the effects of increased atmospheric partial CO2 pressure on processes such as calcification and in interpreting microfossils in the fossil record
Numerical predictions for equilibrium profile on intertidal flat
Morphology of intertidal flat is dictated by the input of sediments from rivers and the subsequent redistribution by waves, currents, and gravity-driven flows. An analytical models is develop for dynamic equilibrium profile from Falcini et al (2012) and Yamada et al (2004) equations and numerical simulations are used to predict the long-term cross-shore morphology changes on intertidal flat adjacent of river mouth. By using these models, we explore the gravity flows and sea bottom slope in determining the critical conditions for bypass of gravity-driven sediment transport. The field site of this research is located on the center of the eastern coast of Ariake Bay at river mouth of Shirakawa River, Japan. Monthly bed level measurement from February 2001 to January 2013 with the distance between 100 to 1050 m and the interval of 10 m from seawall was analyzed. Oceanographic data such as tide level, significant wave height, wave period, and wind velocity measured at an observation tower of Kumamoto Port. Water debit of Shirakawa River is obtained from Ministry of Land, Infrastructure and Transport of Japan. Based on model predictions, we found that the dynamic equilibrium profile is spatially and temporally consistent with field observations and it predicted to be deeper and boarder associated with sediment
Long-term efficacy and safety of eculizumab in Japanese patients with generalized myasthenia gravis : a subgroup analysis of the REGAIN open-label extension study
The terminal complement inhibitor eculizumab was shown to improve myasthenia gravis-related symptoms in the 26-week, phase 3, randomized, double-blind, placebo-controlled REGAIN study (NCT01997229). In this 52-week sub-analysis of the open-label extension of REGAIN (NCT02301624), eculizumab's efficacy and safety were assessed in 11 Japanese and 88 Caucasian patients with anti-acetylcholine receptor antibody-positive refractory generalized myasthenia gravis. For patients who had received placebo during REGAIN, treatment with open-label eculizumab resulted in generally similar outcomes in the Japanese and Caucasian populations. Rapid improvements were maintained for 52 weeks, assessed by change in score from open-label extension baseline to week 52 (mean [standard error]) using the following scales (in Japanese and Caucasian patients, respectively): Myasthenia Gravis Activities of Daily Living (-2.4 [1.34] and - 3.3 [0.651); Quantitative Myasthenia Gravis (-2.9 [1.98] and - 4.3 [0.79]); Myasthenia Gravis Composite (-4.5 [2.63] and - 4.9 [1.19]); and Myasthenia Gravis Quality of Life 15-item questionnaire (-8.6 [5.68) and - 6.5 [1.93]). Overall, the safety of eculizumab was consistent with its known safety profile. In this interim sub-analysis, the efficacy and safety of eculizumab in Japanese and Caucasian patients were generally similar, and consistent with the overall REGAIN population
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