Generic estimates for magnetic fields generated during inflation including Dirac-Born-Infeld theories

We estimate the strength of large-scale magnetic fields produced during inflation in the framework of Dirac-Born-Infeld (DBI) theories. This analysis is sufficiently general in the sense that it covers most of conformal symmetry breaking theories in which the electromagnetic field is coupled to a scalar field. In DBI theories there is an additional factor associated with the speed of sound, which allows a possibility to lead to an extra amplification of the magnetic field in a ultra-relativistic region. We clarify the conditions under which seed magnetic fields to feed the galactic dynamo mechanism at a decoupling epoch as well as present magnetic fields on galactic scales are sufficiently generated to satisfy observational bounds.Comment: 7 pages, no figure, accepted in Phys. Rev.

On relationships among Chern-Simons theory, BF theory and matrix model

Chern-Simons theory on a U(1) bundle over a Riemann surface \Sigma_g of genus g is dimensionally reduced to BF theory with a mass term, which is equivalent to the two-dimensional Yang-Mills on \Sigma_g. We show that the former is inversely obtained from the latter by the extended matrix T-duality developed in hep-th/0703021. For the case of g=0 (i.e. S^2), the U(1) bundle represents the lens space S^3/Z_p. We find that in this case both the Chern-Simons theory and the BF theory with the mass term are realized in a matrix model. We also construct Wilson loops in the matrix model that correspond to those in the Chern-Simons theory on S^3.Comment: 20 pages, references added, typos correcte

Probing the Coupling between Dark Components of the Universe

We place observational constraints on a coupling between dark energy and dark matter by using 71 Type Ia supernovae (SNe Ia) from the first year of the five-year Supernova Legacy Survey (SNLS), the cosmic microwave background (CMB) shift parameter from the three-year Wilkinson Microwave Anisotropy Probe (WMAP), and the baryon acoustic oscillation (BAO) peak found in the Sloan Digital Sky Survey (SDSS). The interactions we study are (i) constant coupling delta and (ii) varying coupling delta(z) that depends on a redshift z, both of which have simple parametrizations of the Hubble parameter to confront with observational data. We find that the combination of the three databases marginalized over a present dark energy density gives stringent constraints on the coupling, -0.08 < delta < 0.03 (95% CL) in the constant coupling model and -0.4 < delta_0 < 0.1 (95% CL) in the varying coupling model, where delta_0 is a present value. The uncoupled LambdaCDM model (w_X = -1 and delta = 0) still remains a good fit to the data, but the negative coupling (delta < 0) with the equation of state of dark energy w_X < -1 is slightly favoured over the LambdaCDM model.Comment: 9 pages, 7 figures, RevTeX, minor corrections, references added, accepted for publication in Phys. Rev.

Realizing Scale-invariant Density Perturbations in Low-energy Effective String Theory

We discuss the realization of inflation and resulting cosmological perturbations in the low-energy effective string theory. In order to obtain nearly scale-invariant spectra of density perturbations and a suppressed tensor-to-scalar ratio, it is generally necessary that the dilaton field $\phi$ is effectively decoupled from gravity together with the existence of a slowly varying dilaton potential. We also study the effect of second-order corrections to the tree-level action which are the sum of a Gauss-Bonnet term coupled to $\phi$ and a kinetic term $(\nabla \phi)^4$. We find that it is possible to realize observationally supported spectra of scalar and tensor perturbations provided that the correction is dominated by the $(\nabla \phi)^4$ term even in the absence of the dilaton potential. When the Gauss-Bonnet term is dominant, tensor perturbations exhibit violent negative instabilities on small-scales about a de Sitter background in spite of the fact that scale-invariant scalar perturbations can be achieved.Comment: 13 pages; v2: minor corrections, refs. added, version to appear in PR

Exiguolide, a new macrolide from the marine sponge Geodia exigua

A new 20-membered macrolide designated exiguolide has been isolated from the marine sponge Geodia exigua, and its structure determined by interpretation of spectroscopic data. Exiguolide specifically inhibited fertilization of sea urchin (Hemicentrotus pulcherrimus) gametes but not embryogenesis of the fertilized egg

Thermoelectric properties of lanthanum sesquisulfide with Ti additive

The electrical resistivity, thermopower, and thermal conductivity have been measured for the lanthanum sesquisulfide (La2S3) of which the crystal phase is controlled by the Ti additive. In all the samples, the thermopower is negative between 300 and 1000 K. The sample with 8 wt % Ti, which consists almost of the cubic γ phase, behaves as a degenerate semiconductor. The thermoelectric figure of merit ZT increases with increasing temperature, reaching a value of 0.21 at 1000 K. In contrast, the sample with 2 wt % Ti consists almost of the tetragonal β phase. The transport mechanism can be well explained by the model of the Anderson localization. The ZT value increases abruptly with increasing temperature. At 1000 K, this ZT value is comparable with that of the sample with 8 wt % Ti

An Efficiency Degradation Model of Power Amplifier and the Impact against Transmission Power Control for Wireless Sensor Networks

Abstract—To extend an available period of wireless sensor networks, transmission power control is regarded as one of the promising schemes. In most of the previous studies on the transmission power control, it is assumed that a transmitter has power consumption of O(dn), where d and n denote a maximum communication distance and a pass loss factor. This assumption would substantially hold under the condition that the transmission efficiency is always constant at any transmission power (efficiency-fixed model). In practice, however, the trans-mission efficiency degrades as the transmission power is reduced. We analytically verify that an actual power amplifier with the efficiency degradation has a power consumption of O(dr), where n/2.8 ≤ r ≤ n/2 (efficiency-degradation model). The efficiency-degradation model gives the negative impact against the transmission power control. Index Terms—Wireless sensor network, transmission power control, transmission efficiency, pass loss factor. I

Two-Dimensional Gauge Theory and Matrix Model

We study a matrix model obtained by dimensionally reducing Chern-Simon theory on S^3. We find that the matrix integration is decomposed into sectors classified by the representation of SU(2). We show that the N-block sectors reproduce SU(N) Yang-Mills theory on S^2 as the matrix size goes to infinity.Comment: 14 pages, a reference added, typos correcte