Eric Sembrat's Test Bonanza

The history of the universe in a nutshell, from the Big Bang to now, and on to the future – John Mather will tell the story of how we got here, how the Universe began with a Big Bang, how it could have produced an Earth where sentient beings can live, and how those beings are discovering their history.  Mather was Project Scientist for NASA’s Cosmic Background Explorer (COBE) satellite, which measured the spectrum (the color) of the heat radiation from the Big Bang, discovered hot and cold spots in that radiation, and hunted for the first objects that formed after the great explosion.  He will explain Einstein’s biggest mistake, how Edwin Hubble discovered the expansion of the universe, how the COBE mission was built, and how the COBE data support the Big Bang theory.  He will also show NASA’s plans for the next great telescope in space, the James Webb Space Telescope.  It will look even farther back in time than the Hubble Space Telescope, and will peer inside the dusty cocoons where stars and planets are being born today. It is capable of examining Earth-like planets around other stars using the transit technique, and future missions may find signs of life. 

Blazar astronomy is rapidly progressing thanks in large part to the successes of the Fermi Gamma-ray Space Telescope and the ground-based gamma-ray telescopes. More than 1000 active galaxies have been detected at GeV energies, and nearly 50 at Very-High Energies (VHE,  > 100 GeV). We can now explore multiwavelength and multi-messenger connections in unprecedented detail, and derive the astroparticle implications of those results. In this presentation, leptonic and hadronic spectral modeling of blazars is reviewed with the intent of identifying ultra-high energy cosmic rays (UHECRs) in  the spectral energy distributions of these objects.  We consider a number of unusual results that could be explained by UHECRs in blazars:

(1) distinct spectral components revealed by deabsorption of blazar VHE spectra;
(2) flattening at moderate redshift in the Stecker-Scully relation showing the GeV - TeV spectral   index difference versus redshift;
(3) conflicting results for the location of the gamma-ray emission site in blazars;
(4) the unusually short variability times of luminous blazars.

The arguments for and against radio galaxies and blazars being the sources of the UHECRs are reviewed, and predictions for UHECR composition is made if BL Lac objects accelerate most of the UHECRs. Unusual effects of UHECR acceleration in blazars is illustrated by the strange case of 4C +21.35.  We also discuss effects of hypothetical axions, a dark matter candidate, in the interpretation of unusual blazar behavior, and a recent Fermi-LAT search for axions in occultations of bright AGNs by the Sun.

The recent advance in coherently controlling and manipulating strong, long-range Rydberg interactions has triggered extensive research in studying interesting many-body effects as, e.g. the use of Rydberg blockade effects for quantum information processing and crystal formation. In this talk I show that Rydberg interactions can be used to alter the photon statistics of a weak probe field after propagating in a coherently prepared atomic Rydberg gas under conditions of Electromagnetically Induced Transparency (EIT).

The Rydberg blockade mechanism leads to an effective two-level physics when two photons are separated by less than the blockade radius resulting in a strong anti-correlation of two photons given by an avoided volume. For large separations the repulsive long-range interaction between the Rydberg atoms induces repulsive interactions between the photons leading to quasi-crystalline states of photons. Confining the system to one dimension the low-energy physics of the excitations can be described in terms of a Luttinger Liquid.

Using DMRG simulations the Luttinger K-parameter is calculated and conditions on the formation of long-range ordered states are derived. Implications of the formation of such hard-sphere photons for the recent experiment of Pritchard et al. [Phys. Rev. Lett. 105, 193603 (2010)] and the observation of long-range correlations in future experiments will be discussed.

Here I present our experimental work synthesizing static gauge fields for ultracold neutral atoms (bosonic and fermionic alkali atoms).  I will discuss this gauge field in the language of spin-orbit coupling where it consists of an equal sum of Rashba and Dresselhaus couplings. In experiment, we couple two internal states of our alkali atoms with a pair of ``Raman'' lasers and load our degenerate quantum gas into the resulting adiabatic eigenstates.

For a Bose gas, a function of the Raman laser strength, a new exchange-driven interaction between the two dressed spins develops, which drives a (quantum) phase transition from a state where the two dressed spin states spatially mix, to one where they phase separate.   Going beyond this simple modification to the spin-dependent interaction, we show that in the limit of large laser intensity, the particles act as free atoms, but interact with contributions from higher even partial waves.

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mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Recent cold atom researches are reaching out far beyond the realm that was conventionally viewed as atomic physics. Many long standing issues in other physics disciplines or in Gedanken-experiments are nowadays common targets of cold atom physicists. Two prominent examples will be outlined in this talk: BEC-BCS crossover and Efimov physics. Here, cold atoms are employed to emulate electrons in superconductors, and nucleons in nuclear reactions, respectively.

The ability to emulate exotic or thought systems using cold atoms stems from the precisely determined, simple, and tunable interaction properties of cold atoms. New experimental tools have also been devised toward an ultimate goal: a complete control and a complete characterization of a few- or many-body quantum system. We are tantalizingly close to this major milestone, and will soon open new venues to explore new quantum phenomena that may (or may not!) exist in scientists’ dreams.

color:black;mso-themecolor:text1">Our group is applying the techniques of modern atomic physics to the system of diatomic molecules.  Molecules are more complex than atoms because of their vibrational and rotational degrees of freedom, and this makes them difficult to control.  However, we have identified a variety of simple principles that allow us to make use of these "new" properties to provide powerful types of leverage on a broad range of problems.  These span fields all the way from particle physics to quantum computation to chemical physics. This talk will give an overview of the field, along with some specific examples of our recent work. These include the first-ever laser cooling of a molecule, and the search for the CP-violating electric dipole moment of the electron.

We have performed absorption imaging of a single atom for the first time [1]. A trapped Yb+ atomic ion scatters light out of an illumination beam tuned to atomic resonance at 369.5 nm. When the beam is reimaged onto a CCD camera, we observe an absorption image of 440 nm diameter and 5% contrast. The absorption contrast is investigated as a function of laser intensity and detuning, and closely conforms to the limits imposed by simple quantum theory and known properties of our imaging system. Defocused absorption images provide spatial interferograms of the scattered light, permitting accurate retrieval of the amplitude and phase of the scattered wave. We measure a phase shift of >1 radian in the scattered light as a function of laser detuning, which may be useful in quantum information protocols. The interferograms point to the possibility of observing the focusing of light by a single atom.

I will discuss some recent computer simulations of three different systems; nematic shells, sticky colloidal particles on surfaces and the bulk phases of liquid crystalline bolaamphiphiles. For nematic shells, a layer of liquid crystal is used to coat a microscopic particle. In this geometry, defects necessarily occur – the system is frustrated so that the director profile and local orientational ordering is not constant everywhere. We examine the interactions between the defects for a number of different types and shapes of particles and other cavities. I will also discuss sticky colloids on a flat surface. We will observe how different phases (or different shaped 'nets') can be templated onto the surface by minor modifications to the size and interactions of the sticky patches. Finally, we will examine the bulk phases of liquid crystalline bolaamphiphiles. These are unusual liquid crystals, with long side chains off a relatively rigid rod that form unusual columnar phases. They differ from conventional liquid crystal columnar phases in that the columns are aliphatic with aromatic walls, rather than aromatic columns with aliphatic walls. We examine how frustration in these systems can lead to novel phases, with unit cells significantly larger than single molecules.

Directed cell motility is a process whereby the motility machinery of the cell (involving the interaction of actin with myosin) is organized spatially so as to cause directed motion. In Dictyostelium, this occurs as the cell responds to cAMP gradients during the aggregation process. In keratocytes, the cell spontaneously polarizes itself (without external cues). This talk will focus on spatially extended modeling of both the signaling system which encodes the directional information and the downstream mechanical response and the comparison of these models to detailed experimental studies of both of these systems.