# Graduate Lunch Club

##### Spring 2006 schedule of talks

##### When

Fridays, 12:00pm - 1:00pm

##### Location

Center for Theoretical Physics, building NE25

4th floor, CTP seminar room 4-107

Massachusetts Institute of Technology

##### Organizers

Vijay Kumar

The CTP Lunch Club meets at 12 noon in the CTP seminar room every Friday (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).

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.

Workshops are aimed at teaching students about particular areas of research rather than presenting cutting edge research. The goal is learning, and to encourage participation, faculty are asked not to attend the workshop portion of these seminars.

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 listed above.

##### February 17

*Experimental Particle Physics Through The Ages*

**Eric Fitzgerald**

MIT

A discussion of some of the most famous particle physics experiments from
the

last century, with an emphasis on the techniques for creation and detection.

Then a look forward to the LHC and possible new discoveries there.

##### February 24

*A "funny" interesting problem in "semi-quantum"
gravity*

**Stefano Ansoldi**

MIT

Interesting systems can be modelled by co-dimension one branes

in General Relativity; although their classical dynamics is a

well-established subject, the quantization procedure still presents some

dark sides. After giving an overview of the basic classical formalism

using a specific example, we then introduce a "funny" problem in
the

semiclassical quantization procedure. We show how this problem raises

some issues about the Euclidean description of gravitational tunnelling

and comment about the interest that a more precise understanding of it

might have in connection with "semi-quantum" gravity.

##### March 3

*Vortices Vacate Vales and other Singular Tales*

**Ari Turner**

Harvard

If you ever wondered what it would be like to live in two dimensions, but
couldn't find a good wormhole, (gedanken) experimentation on thin layers of
superfluids turns out to be a fun alternative. The vortices in a superfluid
film behave like particles--from ordinary fluid

mechanics arises a 1/r Coulomb force among these vortices. When the film is
spread onto a curved surface, the vortices also interact

with the curvature of the surface. Although it is neat to imagine that

this force is like two-dimensional gravity, it can be explained more

accurately with another foray into fluid mechanics, and used to invent problems
for a two-dimensional edition of Jackson.

##### March 10

*LOFF Phase in QCD and Chromomagnetic (In)stability*

**Marco Ruggieri**

University of Bari

We have recently proposed a model of color-superconductor which

describes the crystalline pairing (LOFF) among the quarks Up, Down and

Strange in high density QCD. After a brief introduction to color

superconductivity with three flavors, we discuss such a model. Moreover,

we show that the LOFF phase with three flavors is free from the pathology

of Chromo-Magnetic Instability.

##### March 17

*Topological order and quantum entanglement*

**Michael Levin**

MIT Condensed Matter Theory Group

Topological quantum field theories (TQFTs) were first discovered in 1989
in the context of string theory. Surprisingly, TQFTs also describe the low
energy physics of certain quantum spin systems. These quantum spin systems
are said to contain "topological order." But what exactly is topological
order? In my talk, I will show that topological order manifests itself in
nonlocal quantum entanglement in the ground state. I will introduce a quantity
- called "topological entropy" that

measures precisely this nonlocal entanglement.

##### March 24 - at 1:00pm*

A Gentle Introduction to Lattice QCD

**Patrick Varilly**

MIT

(Note: This week's seminar will start one hour later than usual.)

QCD is a theory that resists perturbative analysis at low energies. I will

give an overview of lattice QCD, a numerical Monte Carlo approach to

calculating observables in this regime. I will start by showing an analogous

method to solving the Schroedinger equation numerically, and slowly

generalizing until we can solve full QCD. Then I will show some examples of

quantities others have calculated in the past from first principles, such
as

particle masses, the potential energy between two static quarks (which shows

the principle behind confinement) and action densities in mesons, baryons
and

the vacuum. Finally, I'll briefly mention some of my own work on mapping the

quark density in mesons and baryons with heavy quarks.

##### April 7

*Constraining Torsion by Gravity Probe B*

**Yi Mao**

MIT

Most torsion gravity theories adopt the interpretation that

the source of torsion is the intrinsic spin of elementary particles, and

that rotational angular momentum does not couple to torsion. We argue

that this interpretation is problematic, by explicitly showing a

counterexample that a rotating body generates torsion field in the

Weitzenbock spacetime with Hayashi-Shirafuji Lagrangian. Given that

torsion is coupled to rotational angular momentum, a gyroscope should

feel torsion. We investigate the way to test torsion gravity theories

by the spin precession of a gyroscope in Gravity Probe B. Modelling

Earth to be a uniformly spinning spherical massive object, the torsion

around Earth is determined by seven parameters by symmetry requirement.

We calculate the instantaneous precession rate of a gyroscope and its

Fourier moments along a circular polar orbit. A gyroscope experiment

such as Gravity Probe B can (1) test or rule out some torsion theories

(e.g. Hayashi-Shirafuji Lagrangian) by measuring the average rate (and,

if technically possible, higher moments) of the precession, and (2) test

the General Relativity by constraining the smallness of torsion

parameters.

##### April 14

*Ads/CFT and an Index for Supersymmetric Gauge Theories*

**Suvrat Raju**

##### April 21

*Implications of the measurement of the B^0_S -\bar{B}^0_S mass difference*

**Zoltan Ligeti**

MIT

##### April 28

*Electromagnetic analogies in weak-field GR*

**Robyn Sanderson**

##### May 5

*Perturbative dynamics of non-commutative
(topologically massive, supersymmetric) QED*

**Nicola Caporaso**

##### May 12

*Spontaneous Parity Breaking at theta= 0 Gauge* Theories

**Dr. Peter Richard Crompton**

##### May 19

*Nu experiments*

**Phillip Harris
**MIT-LNS

Because of the recent affirmation that neutrinos have mass, the number of

neutrino experiments has grow drastically. In this presentation, we will

discuss both the strengths and weaknesses of a number of the new and

proposed neutrino experiments. We will also survey some of their most

recent results as well as past important results.