The Department of Physics and Astronomy at the University of Kentucky is pleased to offer seminar speakers for undergraduate student associations at Colleges and Universities within reasonable driving distance from Lexington. Speakers are available free of charge, all expenses to be paid by our department. To request a speaker and arrange a suitable date, please contact Professor Michael Cavagnero (859-257-6733 or mike@pa.uky.edu) or contact the speaker directly.

Modern Cosmology has come of age. It is now an observable and testable science with verifiable hypotheses. What do current observations and theory tell us about our origins and ultimate destiny? What is curved space? Why is time called the fourth dimension? Where did all the matter and energy in the universe come from? How did structure form? This talk will describe, for the interested undergraduate in Physics, our current understanding of the universe.

A charge-density-wave (CDW) is a state in which the electron density is periodically modulated. In the last two decades, CDW's have been observed to cause some of the most unusual properties ever observed. CDW materials are "super-dielectrics" which also do not obey Ohm's Law -- the current is not proportional to the voltage -- because at very small voltages the CDW can become depinned and slide through the crystal. When the CDW slides, dc currents produce ac voltages. At the depinning voltage, the materials exhibit dramatic "electromechanical" (the elastic constants change) and "electro-optic" (the infrared properties change) effects.

Lithium-Fluoride is very similar to a hydrogen atom. When driven by electromagnetic radiation, the molecule begins to separate ionically as a positively charged lithium ion and a negatively charged fluorine ion with any remaining binding energy due almost entirely to the Coulomb attraction of the massive ions. What results is a vibrational Rydberg series with a reduced mass of approximately 9200 times the electron mass. The vibrationally-hot molecules dissociate to neutral atoms by an elementary quantum process--electron tunneling. This talk, aimed at undergraduate students who are studying quantum mechanics, will illustrate how basic aspects of quantum physics -- including exchange interactions, tunneling, the uncertainty principle, wave packets, and resonance formation -- contribute to the beautiful and remarkable spectra of the alkali-halide salts.

While the quark model has been hugely successful in predicting the various subatomic particles and their properties, we still do not know the equivalent of a "Coulomb's Law" that describes the forces between quarks. I will describe some of the tools that experimentalists have at their disposal to study the strong force.

Masers, the microwave counterparts of lasers, can be constructed in the laboratory only under special circumstances. Yet nature seems to produce them easily in astronomical environments. Intense maser emission from a variety of species is observed in many sources, including far away galaxies. Thanks to their extreme brightness, masers enables us to follow the motion of the masing gas across the sky and to measure accurately the gas velocity, enabling detailed mapping of the geometry and kinematics of the emission region. The most powerful masers nature produces are found in regions of our galaxy where stars are being formed and in the nuclei of ``active galaxies'', systems powered by super-massive (10^6--10^9 solar masses) black holes. In star forming regions, masers provide evidence for jet-driven expanding shells. In active galaxies they give the best evidence yet for black-holes that are surrounded by Keplerian disks.

The dream of Quantum Computing as an intrinsically efficient, massively parallel approach to bit manipulations has provoked widespread interest for its promise of solving otherwise intractable computational problems. This vision has run headlong into another, much older dream -- that of Uncrackable Codes. The last twenty years has witnessed the discovery of the RSA encryption scheme (among others), which is, in practice, a code that not only allows one to distribute encoding keys publicly but which could not be broken even if every computer in the Galaxy were devoted to the task for many ages of the Universe. Or so one hoped. An algorithm invented by Peter Shor to factor large numbers using a hypothetical quantum computer would allow one to decode these indecipherable ciphers after all by efficiently factoring large numbers. We will review a brief history of cryptology, what RSA encryption is and why it is practical (so far), how a quantum computer might function, and how it could be used to crack RSA-encrypted messages.

Supermassive black holes lie at the hearts of the most luminous sources in the Universe, quasars. The bright emission at the wavelength of ordinary visible light has been used to find most quasars, although they are even more powerful at the higher energy of X-rays. Using X-ray observations to investigate quasars is also advantageous because the X-rays directly probe material that is located close to the black holes. I will explain the basic physics behind energetic quasars and present recent results from the latest generation of satellite X-ray observatories.

The history of elementary particle physics before the 1970's is reviewed: From electron to hadrons. I then discuss new discoveries from the 70's to the present: The Standard Model of Electroweak Interactions and the theory of Strong Interactions. Finally, I speculate on the future of elementary particle physics.

Atoms that are excited by laser light or collisions, or which are formed naturally when a free electron drops onto a positive atomic ion, can have enormous size. Consequently, they can have other extreme properties such as long excitation lifetimes, sensitivity to electric and magnetic fields and radiation, and huge collision cross sections. Furthermore, as representatives of the quantum world on nearly macroscopic scales (well ... not as big as the Ritz, perhaps, but thousands to millions of times bigger than normal!) they raise questions of how quantum and classical descriptions of matter correspond. In this talk I will describe the world of highly excited "Rydberg" atoms, as known through experiments at U. Kentucky and other labs worldwide.

Quantum Dots are mesoscopic systems containing a few to a few hundred electrons and exhibit many fascinating features. Due to the inevitable imperfections in making the dot, electrons are scattered chaotically from the walls, leading to their energies near the Fermi energy being random, and governed by Random Matrix Theory (RMT). RMT was initially proposed by Wigner to account for the highly excited spectra of nucleii, but has since been recognized as a universal "statistical mechanics" of mesoscopic systems. When interactions of the Fermi-liquid type between electrons are taken into account, things become even more interesting, but remain fully controllable theoretically in a certain limit. I will describe a strongly-correlated state which spontaneously breaks time-reversal symmetry and its experimental signatures.

Achieving a basic understanding of the life cycles of the stars is one of the triumphs of 20th century physics and astronomy. We now understand much of the formation process. And many aspects of stellar death are known, from the quiet deaths of low-mass stars like the sun to the spectacular explosive deaths of rare massive stars. Recent observations, including space-borne observations have provided a wealth of detail and spectacular images of both stellar birth and death. In this presentation I highlight these new results and images, and I describe some of the important questions that remain to be answered.