Events Archive

Oct
21
2014
Women’s Careers in Science: Lessons from the Global Survey of Physicists
Previous studies of women in physics mostly focused on the lack of women in the field. The Global Survey of Physics goes beyond the obvious shortage of women and shows that there are much deeper issues. For the first time, a multinational study was conducted with 15000 respondents from 130 countries, showing that problems for women in physics transcend national borders. Across all countries, women have fewer resources and opportunities and are more affected by cultural expectations concerning child care. We show that limited resources and opportunities hurt career progress, and because women...
Oct
07
2014
Quantum Control of Spin Interactions in Spin-1 Bose Condensates
Effects of dipolar and spin-exchange interactions are entangled in spin-1 Bose-Einstein condensates, due to their coexistence. We propose to independently manipulate the magnetic dipolar and the spin-exchange interactions by applying generalized WAHUHA sequences of rf pulses and by applying periodic dynamical decoupling sequences of optical Feshbach resonance pulses, respectively. While suppressing one interaction, we can make the other interaction dominate the spin dynamics in the condensates. Furthermore, by suppressing both interactions, this method can be harnessed to realize spinor-...
Oct
06
2014
Optical Metamaterials: from Linear Responses to Nonlinear Interactions and beyond
Metamaterials are commonly viewed as artificially-structured media capable of realizing arbitrary effective parameters, in which metals and dielectrics are delicately combined to facilitate the index contrast and plasmonic response required for a particular purpose. We aim to drive beyond this limited vision and explore the use of optical metamaterials as a generalizable platform for optoelectronic information technology: Metals will provide tailored plasmonic behavior as before, but will serve double duty by providing electrical functions including voltage input,...
Oct
02
2014
Frontiers in Science Lecture Series
   
Sep
29
2014
Puzzles of the glass transition and why it is still interesting
For thousands of years people are using glass transition process and glasses in their everyday life. For hundreds of years researchers are studying the glass transition phenomenon. However, understanding the microscopic mechanism underlying the tremendous slowing down of structural relaxation remains one of the main challenges in the current condensed matter...
Sep
25
2014
2014 Stelson Lecture: How quantum theory and statistical mechanics gave a polynomial of knots
We will see how a result in von Neumann algebras (a theory developed by von Neumann to give the mathematical framework for quantum physics) gave rise, rather serendipitously, to an elementary but very useful invariant in the theory of ordinary knots in three dimensional space. Then we'll look at some subsequent developments of the theory, and talk about a thorny problem which remains open.
Sep
22
2014
Walter Kohn and the Creation of Density Functional Theory
The theoretical physicist Walter Kohn was awarded one-half the 1998 Nobel Prize for Chemistry for his mid-1960's creation of an approach to the many-particle problem in quantum mechanics called density functional theory (DFT). DFT establishes that the ground state charge density provides a complete description of ALL the properties of any atom, molecule, or solid. This was a breakthrough (both conceptually and computationally) because it had been presumed previously that the vastly more complicated many-electron wave function was essential for this purpose. In this talk, I present a biographical sketch of Kohn's unusual educational experiences and the events...
Sep
22
2014
Polaritons in Quantum Optomechanics
The concept of polariton is ubiquitous in the context of radiation-matter interaction. It refers to a generic quasi-particle resulting from the mixing of light with some kind of material excitation (e.g. a plasmon, phonon, or exciton). Cavity optomechanics offers an ideal system to study the coupling between trapped photons and the oscillations of a mechanical resonator. We can thus describe the coherent dynamics in terms of polaritonic excitations. The role of...
Sep
18
2014
The XENON1T Dark Matter Detector
The nature of dark matter remains one of the most fascinating yet unsolved problems in modern science. A large compelling body of evidence supports the theory that almost 27% of the mass-energy density of the universe is made of cold dark matter. The XENON Project aims at the direct detection of dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via nuclear recoils in a LXe Dual-phase Time Projection Chamber. The third phase of the project XENON1T, a ton scale LXe dark matter detector is currently under construction at the Laboratori Nazionali del Gran Sasso in Italy and...
Sep
18
2014
Thinking Beyond The Phonon Gas Model
Understanding the thermal conductivity of bulk crystalline solids is essentially a solved problem and it is well described by the phonon gas model (PGM). The PGM treats individual phonons (e.g., quanta of lattice vibration energy) as gas molecules that carry energy at a certain speed for some averaged distance, termed the mean free path (MFP). This model does an excellent job at explaining the thermal conductivity of crystalline solids and due to advancements in modeling over the last decade, one can now calculate phonon energies, velocities...

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