Shear viscosity of strongly interacting fermionic quantum fluids

Eighty years ago Eyring proposed that the shear viscosity of a liquid, $\eta$, has a quantum limit $\eta \gtrsim n\hbar$ where $n$ is the density of the fluid. Using holographic duality and the AdS/CFT correspondence in string theory Kovtun, Son, and Starinets (KSS) conjectured a universal bound $\frac{\eta}{s}\geq \frac{\hbar}{4\pi k_{B}}$ for the ratio between the shear viscosity and the entropy density, $s$. Using Dynamical Mean-Field Theory (DMFT) we calculate the shear viscosity and entropy density for a fermionic fluid described by a single band Hubbard model at half filling. Our calculated shear viscosity as a function of temperature is compared with experimental data for liquid $^{3}$He. At low temperature the shear viscosity is found to be well above the quantum limit and is proportional to the characteristic Fermi liquid $1/T^{2}$ dependence, where $T$ is the temperature. With increasing temperature and interaction strength $U$ there is significant deviation from the Fermi liquid form. Also, the shear viscosity violates the quantum limit near the crossover from coherent quasi-particle based transport to incoherent transport (the bad metal regime). Finally, the ratio of the shear viscosity to the entropy density is found to be comparable to the KSS bound for parameters appropriate to liquid $^{3}$He. However, this bound is found to be strongly violated in the bad metal regime for parameters appropriate to lattice electronic systems such as organic charge transfer salts.Comment: Revised manuscript with added references, 14 pages 5 figure

Formation of caustics in Dirac-Born-Infeld type scalar field systems

We investigate the formation of caustics in Dirac-Born-Infeld type scalar field systems for generic classes of potentials, viz., massive rolling scalar with potential, $V(\phi)=V_0e^{\pm \frac{1}{2} M^2 \phi^2}$ and inverse power-law potentials with $V(\phi)=V_0/\phi^n,~0<n<2$. We find that in the case of\texttt{} exponentially decreasing rolling massive scalar field potential, there are multi-valued regions and regions of likely to be caustics in the field configuration. However there are no caustics in the case of exponentially increasing potential. We show that the formation of caustics is inevitable for the inverse power-law potentials under consideration in Minkowski space time whereas caustics do not form in this case in the FRW universe.Comment: 16 pages, 14 figures, major revision, conclusions strengthen, to appear in PR

First-principles study of possible shallow donors in ZnAl2O4 spinel

ZnAl2O4 (gahnite) is a ceramic which is considered a possible transparent conducting oxide (TCO) due to its wide band gap and transparency for UV. Defects play an important role in controlling the conductivity of a TCO material along with the dopant, which is the main source of conductivity in an otherwise insulating oxide. A comprehensive first-principles density functional theory study for point defects in ZnAl2O4 spinel is presented using the Heyd, Scuseria, and Ernzerhof hybrid functional (HSE06) to overcome the band gap problem. We have investigated the formation energies of intrinsic defects which include the Zn, Al, and O vacancy and the antisite defects: Zn at the Al site (Zn-Al) and Al at the Zn site (Al-Zn). The antisite defect Al-Zn has the lowest formation energy and acts as a shallow donor, indicating possible n-type conductivity in ZnAl2O4 spinel by Al doping

Observation of the Fresnel and Arago laws using the Mach-Zehnder interferometer

An experimental study is conducted to determine the effect of polarization on the interference of light waves. By using the temporal coherence property of light in a Mach-Zehnder interferometer, we verified the four important Fresnel and Arago laws for linearly polarized and circularly polarized light. This experiment provides a simple method for undergraduates to study the phenomena of interference and polarization. (C) 2008 American Association of Physics Teachers

Implementasi Dan Perancangan Sistem Pakar Untuk Diagnosa Penyakit Mata Pada Manusia Berbasis Pemrograman Clips

Seperti kita ketahui penyakit mata pada manusia ada bermacam-macam seperti Glaukoma, Hordeolum, Kalazion, Katarak, Konjungtivitis, Entropion. Penyakit mata adalah penyakit yang berbahaya, bila tidak segera didiagnosa dan diobati maka dapat menimbulkan kebutaan pada mata ataupun timbul penyakit lainnya. Penyakit mata tersebut dapat didiagnosa melalui gejala-gejala yang timbul yang diderita oleh manusia tersebut ataupun melalui gambaran klinisnya. Dengan menggunakan sistem pakar maka penyakit mata tersebut dapat didiagnosa dan diobati secara tepat dengan prinsip pembentukan basis aturan dan pembangunan komponen dilakukan pada lingkungan pengembangan, sedangkan lingkungan konsultasi digunakan sebagai sistem konsultasi oleh orang yang bukan ahli ataupun yang sudah ahli.Sistem pakar sebagai sistem yang mengadopsi kepakaran manusia ke dalam komputer dan memiliki kedudukan strategis sebagai sistem yang dapat membantu menyelesaikan permasalahan di bidang kedokteran. Sulitnya menentukan jenis penyakit karena rumitnya berbagai gejala yang mengiringinya, dapat dibantu dengan merepresentasikan gejala suatu penyakit ke dalam suatu bahasa pemrograman komputer (Wardana, 2008). Pada penelitian ini, dikembangkan suatu metode untuk mediagnosa 26 jenis penyakit mata berdasarkan 53 jenis gejala , gambaran klinis yang mengiringi serata pengobatan yang sesuai. Lingkungan pengembangan sistem pakar pada penelitian ini menggunakan bahasa pemrograman CLIPS

Onset of stimulated Raman scattering of a laser in a plasma in the presence of hot drifting electrons

Stimulated Raman scattering of a laser in plasmas with energetic drifting electrons was investigated by analyzing the growth of interacting waves during the Raman scattering process. The Langmuir wave and scattered electromagnetic sideband wave grow initially and are dampened after attaining a maximum level that indicates a periodic exchange of energy between the pump wave and the daughter waves. The presence of energetic drifting electrons in the laser-produced plasma influences the stimulated Raman scattering process. The plasma wave generated by Raman scattering may be influenced by the energetic electrons, which enhance the growth rate of the instability. Our results show that the presence of energetic (hot) drifting electrons in a plasma has an important effect on the evolution of the interacting waves. This phenomenon is modeled via two-dimensional particle-in-cell simulations of the propagation and interaction of the laser under Raman instability. (C) 2015 AIP Publishing LLCopen

Effect of Inorganic Fertilizer and Crop Residue on Carbohydrate and Fat Content in Basmati Rice (Oryza sativa L.)

A field experiment was conducted during Kharif season of July 2013 & 2014at crop research farm SHIATS Allahabad to study the effect of inorganic fertilizer and wheat residue on carbohydrate and fat content in basmati rice. Treatments were arranged using (4x3) factorial R.B.D with three replications. Increasing level of NPK fertilizer significantly increases carbohydrate content in grain in 100% RDF ha-1over control. Among incorporation/ retention of wheat residue also increase the carbohydrate content with increasing level from 0 to 5 tone ha-1. It was lower in control and higher in highest level of wheat residue, which was at par with 2.5 t ha-1 wheat residues in the year of experiment 2013-2014. In the fat content maximum increased in 100% RDF (NPK) over control. Among the fat content maximum increased in incorporation of 5 t ha-1 wheat residue was found better than the rest of the treatment both the years of experiment 2013,14 respectively