Talks

In this talk I will discuss an alternative to infation models, namely non singular bouncing models.Their advantage is to supress both the transplanckian problem and the big bang singularity. It also gives a scale invariant power spectrum in the case of amatter bounce.First we will study a toy model, the non singular matter bounce. Then we will try to see what is the effect when we add upradiation through a gauge fields. To do that we add up a coupling term between the scalar fields and the gauge fields to see if it destroys the bounce or not.

(n+1)-dimensional Lifshitz spacetime is deformed by logarithmic expansions in the way to admit a marginally relevant mode in which z is restricted by n=z+1. According to the holographic principle, the deformed spacetime is assumed to be dual for quantum critical theories, and then thermodynamics of generic black holes in the bulk describe the field theory with a dynamically generated momentum scale $Lambda$. This is a basically UV-expanded theory considered in higher dimensions of the Lifshitz holography from the previous works. By finding the proper counterterms, the renormalized action is obtained and by performing the numerical works, the free energy and energy density is expressed in terms of $T/Lambda^2$.

A recent analysis of gamma rays from the centre of our galaxy has provided possible evidence for a dark matter annihilation signal, with the dark matter taking the form of low-mass WIMPs annihilating predominantly to taus. We study an extended Higgs model proposed to yield such a dark matter candidate. Scanning over parameter space in this model, we find suitable areas that feature fairly little fine-tuning. In favoured areas, the cross-sections for invisible decays of neutral Higgses are predicted to be too low for detection atcolliders. However, dark matter direct detection experiments are currently becoming relevant for constraining parameter space in the model.

This is a very informal talk about some of the issues associated with the notion of "macroscopic realism" (MR) and its relation to quantum mechanics (QM). After a brief discussion of the motivation for attempts to modify QM at some point between the level of the atom and that of our own direct experience, and a survey of some candidate experimental systems, I will discuss attempts to quantify the notion of "macroscopic distinctness", the use of temporal Bell inequalities to discriminate between the predictions of QM and those of MR, the related concept of "noninvasive measurement" and existing and possible ways to implement it. I will also comment briefly on the relation between Bell-EPR experiments and those on MR.

Magnetic fields of stars can provide insight on their structure and evolution. These magnetic fields can be detected by exploiting the Zeeman effect. The theory behind detection and the method of Lease Squares Deconvolution will be described and preliminary results will be presented.

Neutron stars are the collapsed cores of massive stars that went under supernova explosions. They are found with high surface magnetic fields, rapid but steady rotation and high density comparable to that inside an atomic nucleus. In the past 20 years, many different classes of neutron stars have been discovered. One of the most enigmatic classes of neutron stars is the compact central objects (CCOs). Only seven of them have been discovered and their emission process are still not well understood. Three of them have magnetic field estimates which are found to be significantly lower than those of the other neutron stars of comparable age. I will describe our project searching for more of these mysterious objects with NASA's Chandra X-ray Observatory. We compiled a list of eleven nearby weak-field neutron stars to look for CCO-like X-ray emission. Chandra carried short observations of six of them and no x-ray emission was found. The physical implications of the results will be discussed.

The large number of high-energy rotational lines of C18O, available via the Herschel Space Observatory, provides an unprecedented ability to model the total C18O column density in hot cores. Using the emission from all the observed lines (up to J=16-15) we use an automated algorithm to model all transitions simultaneously. Under Local Thermodynamic Equilibrium (LTE) assumptions and knowledge of source size, centroid velocity and line width, the model determines the values for total C18O column densities in 4 separate line-of-sight components of Orion KL known as the Extended Ridge, the Outflow/Plateau, the Compact Ridge, and the Hot Core. These values are determined to be: 2.5 X 10^16, 5.9 X 10^16, 1.8 X 10^16, and 6.0 X 10^16 cm^(-2) respectively. We also explain the difficulties in using the said algorithm to model optically thick molecules such as CO which require non-LTE modeling.

Neutron stars are collapsed remnants of massive stars. One form of neutron star, pulsars, produce clock-like radio pulses, a result of their rotation combined with a misalignment of their rotation and magnetic axes. These pulses can be used in a variety of experiments in fundamental physics, including tests of gravity theories, constraining the properties of supranuclear density matter, and gravitational wave detection. In this talk, I will describe pulsar properties and explain how the above experiments are carried out, as well as show interesting recent results.