In my talk I will describe some of the cutting edge experiments that aregoing on in my research group. Our focus is the growth of thin films withatomic level control for both basic science and applications.I will focuson the area of Oxide Electronics where we are focused on a number ofimportant problems.The first will be the observation of ferromagnetism in oxides with nomagnetic dopants such as Nb or Ta doped TiO2. In both these cases,magnetic signatures were first seen by the observation of strong Kondoscattering observed in the low temperature resistivities. We confirm thatthe observed resistivity anomalies arise with a strong Kondo contributionwith a small weak localization contribution.. With further optimizationroom temperature ferromagnetism is seen in these materials. I will discussthe various experimental supporting factors besides just SQUID measurementthat give evidence for this ferromagnetism and how we rule out the effectsof artifacts, a common problem with SQUID only measurements. I will touchupon our recent efforts in the formation of Super Hydrogenic Systems, anew class of materials and give one specific example, that of Ce dopedLu2O3. Lastly but not the least I will cover some of our recentexperiments on integrating oxides with futuristic materials such asgraphene.
08/09/2009 at 4:00 pm
Dr. A. K. Choudhury, VECC, Kolkata
Seminar of General Interest
Lecture Hall Block A, Institute of Physics
Document Date:
Elliptic flow scaling in ideal and viscous hydrodynamics.
Elliptic flow scaling in ideal and viscous hydrodynamics.
Abstract
STAR and PHENIX measurements of elliptic flow, in Au+Au collisions at RHIC,revealed an interesting scaling property: elliptic flow, of different particle species at differentcollisions centrality, when scaled by the initial eccentricity and constituent quark numbers ($n_q$)is a singlefunction of $KE_T/n_q$, $KE_T=m_T-m$. Initial eccentricity scaling suggests that elliptic flow is driven by the initial spatial asymmetry. Constituentquark number scaling indicate existence of initial collective partonic state. Elliptic flow is best explained in ahydrodynamic model. In non-zero impact parameter collisions, the reaction zone is spatially asymmetric.Differential pressure gradient convert the spatial asymmetry to momentum asymmetry, resulting in elliptic flow. Inthe Israel-Stewart’s theory of 2nd order dissipative hydrodynamics, we study the universal scaling of ellipticflow in ideal and viscous fluid evolution. Initial eccentricity scaling is only approximate in ideal hydrodynamicsand gets better with viscosity. Ideal or viscous hydrodynamic do not indicate constituent quarks number scaling anduniversal scaling is only approximate,violated by $sim\% or more in ideal or viscous fluid evolution. We also showthat RHIC data on elliptic flowdemand very small QGP viscosity, $eta/s ~0.08$, indicating nearly ideal fluid isproduced in Au+Au collisions
There is a remarkable similarity between the laws of black hole dynamics and the laws of thermodynamics. One of the great problems of quantum gravity is to understand the entropy of black-holes. String Theory has been successful in accounting for the entropy of several simple black-holes. From a modern perspective, this is a manifestation of the celebrated gauge-gravity correspondence. We will review some of the successes of the theory and conclude with some open questions.
