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Speaker: David Griffiths, Reed University
Title: "Critical Dipoles and Singular Potentials"
The Schrodinger equation for a point charge in the field of a stationary electric dipole admits bound states when the dipole moment exceeds a certain critical value. It is not hard to see why this might be the case, but it is surprisingly difficult to calculate the critical dipole moment. One method exploits a connection between this problem and the infamous 1/x-squared potential on the half-line, an intriguing system that confounds all our quantum intuitions. Resolving its paradoxes requires sophisticated theoretical machinery: renormalization, anomalies, and self-adjoint extensions.
Ian Shipsey, Purdue University
Title:"Bringing Hearing to the Deaf Cochlear Implants: a Technical and Personal Account"
Cochlear implants are the first device to successfully restore neural function. They have instigated a popular but controversial revolution in the treatment of deafness, and they serve as a model for research in neuroscience and biomedical engineering. In this talk the physiology of natural hearing will be reviewed from the perspective of a physicist, and the function of cochlear implants will be described in the context of historical treatments, electrical engineering, psychophysics, clinical evaluation of efficacy and personal experience. The social implications of cochlear implantation and the future outlook for auditory prostheses will also be discussed.
Speaker: Marlan Scully, Texas A&M and Princeton University
Title: "Time and the Quantum:
erasing the Past and Impacting the Future"
As Aharonov and Scully explain: The quantum eraser effect of Scully and Drühl dramatically underscores the difference between our classical conceptions of time and how quantum processes can unfold in time. Such eyebrow-raising features of time in quantum mechanics have been labeled ''the fallacy of delayed choice and quantum eraser'' on the one hand and described ''as one of the most intriguing effects in quantum mechanics'' on the other. In the present paper, we discuss how the availability or erasure of information generated in the past can affect how we interpret data in the present. The quantum eraser concept has been studied and extended in many different experiments and scenarios, for example, the entanglement quantum eraser, the kaon quantum eraser, and the use of quantum eraser entanglement to improve microscopic resolution.
Speaker: Prof. Mikhail Medvedev University of Kansas
Title:"DO EXTRAGALACTIC COSMIC RAYS INDUCE CYCLES IN FOSSIL DIVERSITY?"
Recent work has revealed a 62 +/- 3 Myr cycle in fossil diversity in the past 542 Myr; however, no plausible mechanism has been found. We propose that the cycle may be caused by modulation of cosmic-ray (CR) ﬂux by the solar system vertical oscillation (64 Myr period ) in the Galaxy, the Galactic north-south anisotropy of CR production in the Galactic halo/wind /termination shock (due to the Galactic motion toward the Virgo Cluster), and the shielding by Galactic magnetic ﬁelds. We revisit the mechanism of CR propagation and show that CR ﬂux can vary by a factor of about 5 and reach a maximum at northernmost displacement of the Sun. The very high statistical signiﬁcance of (1) the phase agreement between solar northward excursions and the diversity minima and (2) the correlation of the magnitude of diversity drops with CR amplitudes through all cycles provide solid support for our model. Various observational predictions which can be used to confirm or falsify our hypothesis are presented.
Speaker: Neil Gehrels, NASA GSFC
Title:" "Gamma Ray Burst Discoveries with the Swift Mission"
Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe.
They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation.
The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings.
Observations are made of the X-ray and optical afterglow from ~1 minute after the burst, continuing for days.
Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts.
The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking.
Bursts are providing a new tool to study the high redshift universe.
Swift has detected several events at z>5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances.
The talk will present the latest results from Swift in GRB astronomy.
Speaker: Albert Libchaber, Professor of Physics, Rockefeller University
Title: "Bacteria response to temperature and oxygen"
Sensing changes in the environment is a fundamental property of living organisms. It allows them to respond and adapt to their new surroundings. In the case of bacteria the response can take different forms, such as, modifying their gene-expression profile or altering their swimming pattern. We study the response of E-coli bacteria to a spatial variation of temperature. We examine the temporal behavior of the culture under the temperature gradient and how it is affected by the bacterial density. The response to an oxygen gradient is also presented.
Speaker: Clifford Will, Washington University, St Louis
Title:“The Confrontation between General Relativity and Experiment"
We review the experimental evidence for Einstein's general relativity. Tests of the Einstein Equivalence Principle support the postulates of curved spacetime, while solar-system experiments strongly confirm weak-field general relativity. We describe the status of the recently concluded Gravity Probe B experiment, and of observations of binary pulsar systems. Future tests of the theory in the radiative and strong-field regimes may be possible using gravitational-wave observatories on Earth and in space, and using observations of stars orbiting the central black hole in our galaxy.
Patrick A. Lee, Professor of Physics, MIT
Title:"Quantum spin liquid; from drought to deluge"
The idea of anti-ferromagnetic order was initially greeted with skepticism when Louis Néel introduced it in the '30s but is now considered obvious. Indeed, the search for an exception has turned up empty-handed for 30 years until recently, when a couple of promising examples have surfaced. I shall argue that if confirmed, this represents a new state of matter, called quantum spin liquid, which exhibits novel properties such as emergent fermionic excitations and gauge fields and is related to the de-confinement of a strongly coupled lattice gauge theory.
Speaker: André de Gouvêa, Northwestern University
Title: "The Brave nu World"
Over the past ten years, we have discovered that, different from initial expectations, neutrinos have mass. After quickly reviewing the history of the neutrino and how we came to know that they have tiny but non-zero masses, I'll discuss all that we still know we don't know about neutrinos. In the end, I'll discuss why massive neutrinos are a big deal and how they may have changed our understanding of the particle physics world.
Speaker: Sasha Kopp, University of Texas
Title: "Neutrino Oscillations at the Fermilab Main Injector"
The near-degeneracy of the three known types of neutrinos permits, in quantum mechanics, a mixing of these states, and thus a pure beam of one type of neutrino may transmute to species over time.Measurements of this effect from the Fermilab MINOS experiment will be presented, in particular measurements of the mixing probability, frequency, and searches for neutrino mixing to electron or sterile neutrino flavors.MINOS is the first step in a staged program, to include studies of the mass hierarchy of the neutrino states and searches for CP violation in neutrinos.Future experiments at Fermilab promise a wealth of insight regarding these unique particles, as well as an opportunity to take advantage of the scientific capabilities of the proposed Deep Underground Science and Engineering Laboratory (DUSEL) planned by the NSF.
Speaker: Peter Fisher, MIT
Title: "WiTricity: an odd adventure into the real world"
At one time or another, most physicists have an idea for an invention,
but usually, it comes to not. In this colloquium, I will talk about an
invention I got involved with for wireless energy transfer that turned
into an interesting little adventure involving theorists, venture
capitalists, angels, DARPA, space flight and a truly frightening piece
of apparatus. The colloquium will focus on the science behind the idea
(which is *very* simple) but will include some observations and
cautions for would-be physicists-inventors.
Speaker: Adam Burrows, Princeton University
Title:"Simulating Supernova Explosions"
What has emerged from recent multi-dimensional supernova simulations is the conviction that instabilities and the breaking of spherical symmetry are crucial to explosion, whatever the mechanism. In this talk, I will summarize and motivate the various mechanisms that still contend as the agency of core-collapse explosions and the multi-dimensional complexity that numerical experiments suggest. In the process, I will address future plans to achieve the physical fidelity and numerical precision necessary to engender confidence in what emerges from the next-generation of simulations and the character of the radiation-magneto-hydrodynamics tools in the offing.
Speaker: Reinhard Genzel, Max-Planck-Institute for Extraterrestrial Physics
Title: "The Massive Black Hole at the Center of the Milky Way"
Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of black holes
with masses between a few million to a few billion time the mass of the Sun. I will discuss measurements over the last decade, employing adaptive
optics imaging and spectroscopy on large ground-based telescopes thatprove the existence of such a massive black hole in the Center of our
Milky Way, beyond any reasonable doubt. These data also provide keyinsights into its properties and environment. Future interferometric
studies of the Galactic Center black hole promise to be able to test gravity in its strong field limit. I will also briefly discuss the
cosmological evolution of massive black holes.
Speaker: Felix Aharonian, Dublin Institute for Advanced Studies and Max Planck Institute for Nuclear Physics
Title:"Probing Extreme Cosmic Accelerators with high energy gamma-rays and neutrinos"
The recent very high energy (VHE) gamma-ray observations revealed many galactic and extragalactic nonthermal sources in which acceleration of relativistic particles (electrons and protons) proceeds at the maximum (theoretically possible) rates. I will discuss properties of these extreme accelerators in the VHE gamma-ray regime and highlight the approaches towards understanding their origin in the context of future observations with next generation high energy gamma-ray and neutrino detectors.