Effective dynamics of the hybrid quantization of the Gowdy T^3 universe

The quantum dynamics of the linearly polarized Gowdy T^3 model (compact inhomogeneous universes admitting linearly polarized gravitational waves) is analyzed within Loop Quantum Cosmology by means of an effective dynamics. The analysis, performed via analytical and numerical methods, proves that the behavior found in the evolution of vacuum (homogeneous) Bianchi I universes is preserved qualitatively also in the presence of inhomogeneities. More precisely, the initial singularity is replaced by a big bounce which joins deterministically two large classical universes. In addition, we show that the size of the universe at the bounce is at least of the same order of magnitude (roughly speaking) as the size of the corresponding homogeneous universe obtained in the absence of gravitational waves. In particular, a precise lower bound for the ratio of these two sizes is found. Finally, the comparison of the amplitudes of the gravitational wave modes in the distant future and past shows that, statistically (i.e., for large samples of universes), the difference in amplitude is enhanced for nearly homogeneous universes, whereas this difference vanishes in inhomogeneity dominated cases. The presented analysis constitutes the first systematic effective study of an inhomogeneous system within Loop Quantum Cosmology, and it proves the robustness of the results obtained for homogeneous cosmologies in this context.Comment: 21 pages, 11 figures, RevTex4-1 + BibTe

Quantum fluctuations and semiclassicality in an inflaton-driven evolution

A semiclassical description of quantum systems is applied to probe the dynamics of the cosmological model of an inflationary universe with quadratic inflaton potential, described in a quantum framework of geometrodynamics. The systematic analysis, focusing in particular on the inflationary and post-inflationary epochs, revealed several surprising and counterintuitive features: $(i)$ during inflation the universe undergoes a large amount of squeezing that leads to considerable variance in the volume at its end; $(ii)$ despite that, the quantum evolution can still be described to high accuracy by semiclassical methods; $(iii)$ moreover, in the post-inflationary epoch, as the order of included quantum corrections increases, the quantum trajectory approaches the classical one and the description involving second-order corrections only is actually the least accurate there. The consequence of the latter is that fluctuation effects (usually hoped to provide a source for a small cosmological constant) are washed out by the higher-order quantum corrections

Modeling the ionospheric response to the 28 October 2003 solar flare due to coupling with the thermosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94973/1/rds5664.pd

Description of Supernova Data in Conformal Cosmology without Cosmological Constant

We consider cosmological consequences of a conformal invariant formulation of Einstein's General Relativity where instead of the scale factor of the spatial metrics in the action functional a massless scalar (dilaton) field occurs which scales all masses including the Planck mass. Instead of the expansion of the universe we get the Hoyle-Narlikar type of mass evolution, where the temperature history of the universe is replaced by the mass history. We show that this conformal invariant cosmological model gives a satisfactory description of the new supernova Ia data for the effective magnitude - redshift relation without a cosmological constant and make a prediction for the high-redshift behavior which deviates from that of standard cosmology for $z>1.7$.Comment: 13 pages, 1 figure, includes discussion of SN1997ff, text revise

Developing a Yeast Model of Amyotrophic Lateral Sclerosis Involving the SOD1 Gene

Amyotrophic lateral sclerosis (ALS), one of the most common neuromuscular diseases in the world, is an unremittingly progressive disease that degenerates motor neurons in the brain and spinal cord. Roughly 10% of ALS cases are considered familial and can result from mutations in more than dozen different genes. The most common mutations in familial ALS occur in the SOD1 gene. SOD1 encodes a copper-zinc superoxide dismutase that detoxifies oxygen free radicals.  To date, approximately 140 mutations in SOD1 (many of which are missense) have been linked to familial ALS.  Evidence suggests that these mutations induce SOD1 protein misfolding and aggregation into cytotoxic structures.  We are developing a yeast model of ALS based on the expression of mutant human SOD1 proteins.  Such a yeast system will permit high throughput genetic screens to identify genes that enhance or suppress the toxic phenotypes associated with mutant SOD1 expression (thereby identifying critical supporting or suppressing pathways), as well as chemical screens to identify compounds that inhibit mutant SOD1 toxicit