Graduate Student Lunch Club

When & Where

The CTP Lunch Club meets every Friday at noon in the Cosman seminar room, 6C-442 (provided that there are sufficient speakers). A light lunch will be provided begining at 11:50am (usually pizza, however some other options may be explored).

About the Seminar

The seminars are designed for graduate students and should be accessible to all students. First year students are particularly encouraged to attend so that they may learn about research being performed in the CTP. The goal is learning, and to encourage participation, the seminars will be for students only.

Email notification of the club will be sent to the ctp-all, ctp-postdocs and ctp-students email lists as appropriate. If you wish to speak, or have suggestions about speakers and/or possible workshop topics, please contact the organizer, Eric Fitzgerald.

 

Schedule for Spring 2008

• February 8
  Eric Fitzgerald
  

  Bound State Quantum Field Theory: The Lamb Shift

  Usual calculations in QFT involve calculating scattering states that asymptotically move to free fields. What happens when that is no longer the case? There are corrections to the energy levels of the electron in the hydrogen atom that can only be found using QFT, but the electron itself cannot be treated as an asymptotically free particle. We'll explore how to overcome these difficulties to find the celebrated Lamb Shift for the hydrogen atom.
  

• February 15
  Daniel Nagaj
  

  Hamiltonian Quantum Cellular Automata in 1D

  What are the simplest pieces one can build a (quantum) computer from? I will present a simple nearest-neighbor, translationally invariant Hamiltonian on a chain of spins (with 10 states per spin) and show that it is powerful. In fact, we can do any quantum computation with it by initializing it in a basis state, letting it evolve freely for a while and measuring one of the spins.
  The talk will include analyzing a diffusion of free fermions on a line and also some chicken.
  This is joint work with Pawel Wocjan (UCF).
  http://lanl.arxiv.org/abs/0802.0886

• February 22
  Prof. Gordon Semenoff

  Finite Size Spectrum of the Giant Magnon

• February 29
  Wouter Waalewijn

  't Hooft anomaly matching conditions (with correct pronounciation!)

  't Hooft anomaly matching conditions put restrictions on confining gauge theories that have chiral symmetries. They imply that chiral symmetry must be broken in QCD and are a useful tool in studying (possible) quark compositeness.

• March 14
  Ambar Jain

  Phenomenology of Heavy Quark Masses
  I will discuss the Heavy Quark Effective Theory and problems with heavy quark pole mass. Then I will motivate the need of various mass schemes to define heavy quark mass and discuss the scales involved in such schemes. I will discuss issues in converting between these schemes and present some new ideas in this context.

• March 21
  Vijay Kumar

  Everything I know about Instantons
  I will introduce instantons as quanta of tunneling and then talk about
  the vacuum structure of a Yang-Mills theory, where they have a dramatic
  effect. Lastly, I will discuss Theta-Vacua and the breaking of the axial U(1)
  in two-flavor QCD by instanton effects. An excellent reference for this
  talk is Coleman’s Aspects of Symmetry, chapter 7.

• April 4
  David Guarrera

  Linear Sigma Models: Making the Extra Dimensions With Algebra and Calculus
  I will talk briefly about the extra dimensions in string theory, and about how some of their properties can be investigated by studying two dimensional supersymmetric gauge theories. This will lead us to a discussion of the vacuum manifolds of these theories. Towards the end, I'll also talk about spacetime topology change, which is friggin' cool. The aim of the talk is very introductory; my hope is that you will only need to know a bit about quantum field theory (beta functions, etc.), calculus, and algebra to get something from it.

• April 11
  Mauro Brigante

  Derivatives
  

• April 18
  Qudsia Ejaz

  Flavorful AdS/CFT
  In this talk, I will discuss how fundamental matter might be introduced into N=4 SYM using probe D7-branes, both at zero and finite temperatures.

• April 25
  Claudio Marcantonini

  DIS - More Than Just a Great Place to Live
  

• May 2
  Alejandro Jenkins

  When Did Ignorance Become a Point of View? or The decoherence interpretation of quantum mechanics
  The problem of measurement in quantum mechanics (QM) has driven many smart people (e.g. Einstein) crazy and generated much mystical twaddle, but many physicists are not aware that over the last fifty years or so theorists have worked out an interpretation of QM in which the observers and the observed are placed on equal footing, and the ultimate laws of nature are not statistical.

  A measurement involves an interaction between the system being observed and the observer. The observer's ignorance about the effect of this interaction on her and her surroundings is the source of her inability to predict the outcome of the measurement with certainty. I will show how this works for two examples: the Stern-Gerlach experiment and Born's statistical interpretation of the wavefunction for a particle in space.

  This is an application of the so-called "decoherence interpretation" of QM. Even without nosy physicists, systems decohere by interacting with their environment. We may describe the system by classical physics to the extent that we are indifferent to how the environment was affected by that interaction. In this interpretation, the notion of time evolution emerges from our indifference to the quantum state of some subsystem that we think of as the "environment." In the complete quantum description of the universe there would be no time flow, as captured by the Wheeler-DeWitt equation.

• May 9
  Mark Hertzberg

  Axion Cosmology and Inflation
  I will discuss two highly appealing physical theories: Inflation, which is our paradigm of early universe physics, and QCD-Axion, which is our paradigm of strong physics. Each theory is governed by an energy scale, whose value is unknown. I will give some naive expectations from theory as to what these energy scales might be, and confront these expectations with observational data. By examining the topic of axion-cosmology, I will demonstrate that constraints from gravitational waves, stars, dark matter, and isocurvature fluctuations, are incompatible with the naive theory. This means we need to modify our ideas about either Inflation or the QCD-Axion.

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