Unparticle effects in Supernovae cooling

Recently H. Georgi suggested that a scale invariant unparticle ${\mathcal{U}}$ sector with an infrared fixed point at high energy can couple with the SM matter via a higher-dimensional operator suppressed by a high cut-off scale. Intense phenomenological search of this unparticle sector in the collider and flavour physics context has already been made. Here we explore it's impact in cosmology, particularly it's possible role in the supernovae cooling. We found that the energy-loss rate (and thus the cooling) is strongly dependent on the effective scale \LdaU and the anomalous dimension \dU of this unparticle theory.Comment: 9 pages, 2 figures, text is modified, references updated and version accepted for publication in Phys. Rev.

M\"{o}ller and Bhabha scattering in the noncommutative standard model

We study the M\"{o}ller and Bhabha scattering in the noncommutative extension of the standard model(SM) using the Seiberg-Witten maps of this to first order of the noncommutative parameter $\theta_{\mu \nu}$. We look at the angular distribution $d\sigma/d\Omega$ to explore the noncommutativity of space-time at around $\Lambda_{NC} \sim$ TeV and find that the distribution deviates significantly from the one obtained from the commutative version of the standard model.Comment: 15 pages, 14 eps figures.Text is modified a little and version to appear in Phys.Rev.

Bright and Dark periods in the Entanglement Dynamics of Interacting Qubits in Contact with the Environment

Interaction among the qubits are basis to many quantum logic operations. We report how such inter-qubit interactions can lead to new features, in the form of bright and dark periods in the entanglement dynamics of two qubits subject to environmental perturbations. These features are seen to be precursors to the well known phenomenon of sudden death of entanglement [Yu & Eberly, Phys. Rev. Lett. {\bf 93}, 140404 (2004)] for noninteracting qubits. Further we find that the generation of bright and dark periods are generic and occur for wide varieties of the models of environment. We present explicit results for two popular models.Comment: New published version, corrected figure

Landauer formula for phonon heat conduction: relation between energy transmittance and transmission coefficient

The heat current across a quantum harmonic system connected to reservoirs at different temperatures is given by the Landauer formula, in terms of an integral over phonon frequencies \omega, of the energy transmittance T(\omega). There are several different ways to derive this formula, for example using the Keldysh approach or the Langevin equation approach. The energy transmittance T({\omega}) is usually expressed in terms of nonequilibrium phonon Green's function and it is expected that it is related to the transmission coefficient {\tau}({\omega}) of plane waves across the system. In this paper, for a one-dimensional set-up of a finite harmonic chain connected to reservoirs which are also semi-infinite harmonic chains, we present a simple and direct demonstration of the relation between T({\omega}) and {\tau}({\omega}). Our approach is easily extendable to the case where both system and reservoirs are in higher dimensions and have arbitrary geometries, in which case the meaning of {\tau} and its relation to T are more non-trivial.Comment: 17 pages, 1 figur