Search Talks

The spacetime or histories approach is a whole attitude to quantum mechanics in which histories are fundamental rather than states. In this talk we will review a suggested dynamics and a suggested interpretation in this framework, phrasing the dynamics of stochastic collapse models in the histories language then proceeding to explore a new realist interpretation suggested by Rafael Sorkin and examining its perspective on the Kochen-Specker result.

We describe the measurement statistics of the balanced homodyne detection scheme in terms of the moment operators of the associated positive operator measures. In particular, we give a mathematically rigorous proof for the fact that the high amplitude limit in the local oscillator leads to a measurement of a rotated quadrature operator of the signal _eld. Using these results, we also show that each covariant phase space observable can be measured with the eight-port homodyne detector.

With the discovery of many new satellite galaxies, in recent years our understanding of the Milky Way environment has undergone a dramatic transformation. I will discuss what these discoveries are telling us about galaxy formation and the nature of dark matter itself. Issues I will focus on include: identifying the least luminous dark matter halo in the Universe, distinguishing between warm and cold dark matter, and indirect dark matter detection.

In the first part of the talk we introduce a technique to compute large scale correlations in LQG and spinfoam models. Using this formalism we calculate some components of the graviton propagator and of the n-points function. In the second part we apply the ideas suggested by LQG to the black hole interior . The result of the quantum analysis is that the classical singularity disappears in loop quantum gravity. Solving the semiclassical Einstein equation of motion we obtain a metric regular and singularity free in contrast to the classical one. By using the new metric we calculate the Hawking temperature, entropy and we study the mass evaporation process.

One of the most significant questions in quantum information is about the origin of the computational power of the quantum computer; namely, from which feature of quantum mechanics and how does the quantum computer obtain its superior computational potential compared with the classical computer? In my talk, I address this open question more concisely through the study of measurement-based quantum computer, in which all the quantum resource is attributed to entanglement since computation is carried through its consumption by local measurements. I also show a simple model of the phase transition of quantum computer occurring at some threshold, below which the quantum computer comes to allow an efficient classical simulation in accordance with an exponential drop in the amount of entanglement.

Quantum fields in the Minkowski vacuum are entangled with respect to local field modes. This entanglement can be swapped to spatially separated quantum systems using standard local couplings. A single, inertial field detector in the exponentially expanding (de Sitter) vacuum responds as if it were bathed in thermal radiation in a Minkowski universe. Using two inertial detectors, interactions with the field in the thermal case will entangle certain detector pairs that would not become entangled in the corresponding de Sitter case.The two universes can thus be distinguished by their entangling power.

We demonstrate a number of effective field theory constructions developed to capture the effects of new physics on the Higgs sector of the standard model. We demonstrate that as the self couplings of the Higgs could be significantly effected by new physics, novel phenomenology such as a two Higgs bound state (Higgsium) may be possible. We also demonstrate that the effects of new physics on the Higgs fermion couplings, and thus the Higgs width, could be significant. We show that it is possible this could happen while the new physics cannot be directly detected at LHC. This could lead to an early Higgs discovery or a missing Higgs in the first 100 fb^(-1) of data at LHC.

Cosmic strings are non-trivial configurations of scalar (and vector) fields that are stable on account of a topological conservation law. They can be formed in the early universe as it cools after the Big Bang. The scalar fields required to form cosmic strings arise naturally if Nature is supersymmetric at high energies. A common feature of supersymmetric theories are directions in the scalar potential that are extremely flat. Combining these two ingredients, the cosmic strings associated with supersymmetric flat directions are qualitatively different from ordinary cosmic strings. In particular, flat-direction strings have very stable higher-winding modes, and are very wide relative to the scale of their energy density. These novel features have important implications for the formation and evolution of a network of flat-direction cosmic strings in the early universe. They also affect the observational signatures of the strings, which include gravity waves, dark matter, and modifications to the nuclear abundances and the blackbody spectrum of the microwave background radiation