Electrical conductivity and thermal behavior of solid electrolytes based on alkali carbonates and sulfates

Both thermal stability and electrical conductivity of alkali ion conducting Na2CO3 and Na2SO4, were improved by adding alkaline earth carbonates and sulfates, respectively, as well as insulating materials like ¿-Al2O3. The admixing of divalent compounds causes two effects. First a more or less extended solution can exist depending on the radius of the alkaline earth ion and is accompanied by an increase in electrical conductivity. Secondly, a phase mixture with an excess of dopant was observed that shows an enhancement in conductivity and mechanical stability. This phenomenon known as composite effect was observed in the following systems: Na2CO3-BaCO3, Na2CO3-SrCO3, Na2SO4-BaSO4, Na2SO4-¿-Al2O3

Scenario of inflationary cosmology from the phenomenological Λ\Lambda models

Choosing the three phenomenological models of the dynamical cosmological term $\Lambda$, viz., $\Lambda \sim (\dot a/a)^2$, $\Lambda \sim {\ddot a/a}$ and $\Lambda \sim \rho$ where $a$ is the cosmic scale factor, it has been shown by the method of numerical analysis that the three models are equivalent for the flat Universe $k=0$. The evolution plots for dynamical cosmological term $\Lambda$ vs. time $t$ and also the cosmic scale factor $a$ vs. $t$ are drawn here for $k=0, +1$. A qualitative analysis has been made from the plots which supports the idea of inflation and hence expanding Universe.Comment: 12 latex pages with 12 figures; Replaced with the revised version; Accepeted for `J. Non-lin. Frac. Phen. Sci. Engg.

The Coulomb law in the pure gauge U(1) theory on a lattice

We study the heavy charge potential in the Coulomb phase of pure gauge compact U(1) theory on the lattice. We calculate the static potential $V_W(T,{\vec R})$ from Wilson loops on a $16^3 \times 32$ lattice and compare with the predictions of lattice perturbation theory. We investigate finite size effects and, in particular, the importance of non-Coulomb contributions to the potential. We also comment on the existence of a maximal coupling in the Coulomb phase of pure gauge U(1) theory.Comment: 14 pages. LaTeX file and 3 postscript figure

Non-Gaussian errors of baryonic acoustic oscillations

We revisit the uncertainty in baryon acoustic oscillation (BAO) forecasts and data analyses. In particular, we study how much the uncertainties on both the measured mean dilation scale and the associated error bar are affected by the non-Gaussianity of the non-linear density field. We examine two possible impacts of non-Gaussian analysis: (1) we derive the distance estimators from Gaussian theory, but use 1000 N-Body simulations to measure the actual errors, and compare this to the Gaussian prediction, and (2) we compute new optimal estimators, which requires the inverse of the non-Gaussian covariance matrix of the matter power spectrum. Obtaining an accurate and precise inversion is challenging, and we opted for a noise reduction technique applied on the covariance matrices. By measuring the bootstrap error on the inverted matrix, this work quantifies for the first time the significance of the non-Gaussian error corrections on the BAO dilation scale. We find that the variance (error squared) on distance measurements can deviate by up to 12% between both estimators, an effect that requires a large number of simulations to be resolved. We next apply a reconstruction algorithm to recover some of the BAO signal that had been smeared by non-linear evolution, and we rerun the analysis. We find that after reconstruction, the rms error on the distance measurement improves by a factor of ~1.7 at low redshift (consistent with previous results), and the variance ({\sigma}^2) shows a change of up to 18% between optimal and sub-optimal cases (note, however, that these discrepancies may depend in detail on the procedure used to isolate the BAO signal). We finally discuss the impact of this work on current data analyses.Comment: 13 pages, 11 figures, MNRAS accepte

A limit on the detectability of the energy scale of inflation

We show that the polarization of the cosmic microwave background can be used to detect gravity waves from inflation if the energy scale of inflation is above 3.2 times 10^15 GeV. These gravity waves generate polarization patterns with a curl, whereas (to first order in perturbation theory) density perturbations do not. The limiting ``noise'' arises from the second--order generation of curl from density perturbations, or rather residuals from its subtraction. We calculate optimal sky coverage and detectability limits as a function of detector sensitivity and observing time.Comment: 4 pages, 3 figures, submitted to PR

A new approach to spherically symmetric junction surfaces and the matching of FLRW regions

We investigate timelike junctions (with surface layer) between spherically symmetric solutions of the Einstein-field equation. In contrast to previous investigations this is done in a coordinate system in which the junction surface motion is absorbed in the metric, while all coordinates are continuous at the junction surface. The evolution equations for all relevant quantities are derived. We discuss the no-surface layer case (boundary surface) and study the behaviour for small surface energies. It is shown that one should expect cases in which the speed of light is reached within a finite proper time. We carefully discuss necessary and sufficient conditions for a possible matching of spherically symmetric sections. For timelike junctions between spherically symmetric space-time sections we show explicitly that the time component of the Lanczos equation always reduces to an identity (independently of the surface equation of state). The results are applied to the matching of FLRW models. We discuss `vacuum bubbles' and closed-open junctions in detail. As illustrations several numerical integration results are presented, some of them indicate that the junction surface can reach the speed of light within a finite time.Comment: new version - corrected boundary surface discussion, improved presentation, and corrected reference 22 pages, many figure

Probing the equation of state of the early universe with a space laser interferometer

We propose a method to probe the equation of state of the early universe and its evolution, using the stochastic gravitational wave background from inflation. A small deviation from purely radiation dominated universe ($w= 1/3$) would be clearly imprinted on the gravitational wave spectrum $\Omega_{GW}(f)$ due to the nearly scale invariant nature of inflationary generated waves.Comment: 10 pages, 1 figur

Classification of Inflationary Einstein--Scalar--Field--Models via Catastrophe Theory

Various scenarios of the initial inflation of the universe are distinguished by the choice of a scalar field {\em potential} $U(\phi)$ which simulates a {\it temporarily} non--vanishing {\em cosmological term}. Our new method, which involves a reparametrization in terms of the Hubble expansion parameter $H$, provides a classification of allowed inflationary potentials and of the stability of the critical points. It is broad enough to embody all known {\it exact} solutions involving one scalar field as special cases. Inflation corresponds to the evolution of critical points of some catastrophe manifold. The coalescence of its nondegenerate critical points with the creation of a degenerate critical point corresponds the reheating phase of the universe. This is illustrated by several examples.Comment: 12 pages, REVTeX, no figure

Oblique Confinement and Phase Transitions in Chern-Simons Gauge Theories

We investigate non-perturbative features of a planar Chern-Simons gauge theory modeling the long distance physics of quantum Hall systems, including a finite gap M for excitations. By formulating the model on a lattice, we identify the relevant topological configurations and their interactions. For M bigger than a critical value, the model exhibits an oblique confinement phase, which we identify with Lauglin's incompressible quantum fluid. For M smaller than the critical value, we obtain a phase transition to a Coulomb phase or a confinement phase, depending on the value of the electromagnetic coupling.Comment: 8 pages, harvmac, DFUPG 91/94 and MPI-PhT/94-9

Interpolating the Stage of Exponential Expansion in the Early Universe: a possible alternative with no reheating

In the standard picture, the inflationary universe is in a supercooled state which ends with a short time, large scale reheating period, after which the universe goes into a radiation dominated stage. An alternative is proposed here in which the radiation energy density smoothly decreases all during an inflation-like stage and with no discontinuity enters the subsequent radiation dominated stage. The scale factor is calculated from standard Friedmann cosmology in the presence of both radiation and vacuum energy density. A large class of solutions confirm the above identified regime of non-reheating inflation-like behavior for observationally consistent expansion factors and not too large a drop in the radiation energy density. One dynamical realization of such inflation without reheating is from warm inflation type scenarios. However the solutions found here are properties of the Einstein equations with generality beyond slow-roll inflation scenarios. The solutions also can be continuously interpolated from the non-reheating type behavior to the standard supercooled limit of exponential expansion, thus giving all intermediate inflation-like behavior between these two extremes. The temperature of the universe and the expansion factor are calculated for various cases. Implications for baryongenesis are discussed. This non-reheating, inflation-like regime also appears to have some natural features for a universe that is between nearly flat and open.Comment: 26 pages, Latex, 2 figures, In press Physical Review