Strong Lensing Probabilities in a Cosmological Model with a Running Primordial Power Spectrum

The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dFGRS and Lyman $\alpha$ forest) suggest a $\Lambda$CDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat $\Lambda$CDM model with a running spectral index (RSI-$\Lambda$CDM model). It is shown that the RSI-$\Lambda$CDM model suppress the predicted lensing probabilities on small splitting angles of less than about 4$^{''}$ compared with that of standard power-law $\Lambda$CDM (PL-$\Lambda$CDM) model.Comment: 11 pages including 1 figures. Accepted for publication in Modern Physics Letters A (MPLA), minor revision

Turn-on speed of grounded gate NMOS ESD protection transistors

The turn-on speed of nMOS transistors (nMOST) is of paramount importance for robust Charged Device Model (CDM) protection circuitry. In this paper the nMOST turn-on time has been measured for the first time in the sub-halve nanosecond range with a commercial e-beam tester. The method may be used to improve CDM-ESD hardness by investigating the CDM pulse responses within circuit. Furthermore it is shown that the CDM results of various protection layouts can be simulated with a SPICE model

Viscous Cold Dark Matter in agreement with observations

We discuss bulk viscous cosmological models. Since the bulk viscous pressure is negative, viable viscous cosmological scenarios with late time accelerated expansion can in principle be constructed. After discussing some alternative models based on bulk viscous effects we will focus on a model very similar to the standard $\Lambda$CDM. We argue that a $\Lambda${\rm v}CDM model, where we assign a very small (albeit perceptible) bulk viscosity to dark matter is in agreement with available cosmological observations. Hence, we work with the concept of viscous Cold Dark Matter ({\rm v}CDM). At the level of the perturbations, the growth of {\rm v}CDM structures is slightly suppressed when compared with the standard CDM ones. Having in mind that the small scale problems of the $\Lambda$CDM model are related to an excess of clustering, our proposal seems to indicate a possible direction for solving the serious drawbacks of the CDM paradigm within the standard cosmological model.Comment: 16 pages, 2 figures, to the proceedings of "49th Winter School of Theoretical Physics Cosmology and non-equilibrium statistical mechanics", L{\ka}dek-Zdr\'oj, Poland, February 10-16, 201

A closer look at interacting dark energy with statefinder hierarchy and growth rate of structure

We investigate the interacting dark energy models by using the diagnostics of statefinder hierarchy and growth rate of structure. We wish to explore the deviations from $\Lambda$CDM and to differentiate possible degeneracies in the interacting dark energy models with the geometrical and structure growth diagnostics. We consider two interacting forms for the models, i.e., $Q_1=\beta H\rho_c$ and $Q_2=\beta H\rho_{de}$, with $\beta$ being the dimensionless coupling parameter. Our focus is the I$\Lambda$CDM model that is a one-parameter extension to $\Lambda$CDM by considering a direct coupling between the vacuum energy ($\Lambda$) and cold dark matter (CDM), with the only additional parameter $\beta$. But we begin with a more general case by considering the I$w$CDM model in which dark energy has a constant $w$ (equation-of-state parameter). For calculating the growth rate of structure, we employ the "parametrized post-Friedmann" theoretical framework for interacting dark energy to numerically obtain the $\epsilon(z)$ values for the models. We show that in both geometrical and structural diagnostics the impact of $w$ is much stronger than that of $\beta$ in the I$w$CDM model. We thus wish to have a closer look at the I$\Lambda$CDM model by combining the geometrical and structural diagnostics. We find that the evolutionary trajectories in the $S^{(1)}_3$--$\epsilon$ plane exhibit distinctive features and the departures from $\Lambda$CDM could be well evaluated, theoretically, indicating that the composite null diagnostic $\{S^{(1)}_3, \epsilon\}$ is a promising tool for investigating the interacting dark energy models.Comment: 17 pages, 4 figures; accepted for publication in JCA

Technically natural dark energy from Lorentz breaking

We construct a model of dark energy with a technically natural small contribution to cosmic acceleration, i.e. this contribution does not receive corrections from other scales in the theory. The proposed acceleration mechanism appears generically in the low-energy limit of gravity theories with violation of Lorentz invariance that contain a derivatively coupled scalar field Theta. The latter may be the Goldstone field of a broken global symmetry. The model, that we call Theta-CDM, is a valid effective field theory up to a high cutoff just a few orders of magnitude below the Planck scale. Furthermore, it can be ultraviolet-completed in the context of Horava gravity. We discuss the observational predictions of the model. Even in the absence of a cosmological constant term, the expansion history of the Universe is essentially indistinguishable from that of Lambda-CDM. The difference between the two theories appears at the level of cosmological perturbations. We find that in Theta-CDM the matter power spectrum is enhanced at subhorizon scales compared to Lambda-CDM. This property can be used to discriminate the model from Lambda-CDM with current cosmological data.Comment: A few equations in the Appendix correcte