# Graduate Lunch Club

##### Fall 2005 schedule of talks

##### When

Fridays, 11:50am - 1:00pm

##### Location

Center for Theoretical Physics, building NE25

4th floor, CTP seminar room 4-107

Massachusetts Institute of Technology

##### Organizers

David Guarrera and Antonello Scardicchio

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.

##### September 16

*Coherent Decay of a Bose-Einstein Condensate*

**George Cragg**

MIT

##### September 23

*Quantum Blackbox Algorithms*

**Stephen Jordan**

MIT

##### September 30

*Family Symmetry Model Building*

**Brian Patt**

MIT

##### October 7

*V _{ub} *from B -> pi ell nu and Complex Magic

**Chris Arnesen**

MIT

##### October 21

*LHC Olympics: A theorist's adventures in collider physics*

**Can Kilic**

Harvard

The LHC will start taking data in a couple of years and likely discover new physics around the TeV scale. While there exist a lot of theoretical models for 'Beyond The Standard Model' scenarios, there is no well established framework of telling these models apart experimentally, in fact experimentalists mostly hold the viewpoint that in most cases this cannot be done beyond simply establishing the existence of new physics. The LHC Olympics is a collective effort by theorists to train themselves in establishing a rough correspondence between theoretical models and experimental signatures and to come up with more efficient inclusive signatures using collider simulation. I will talk about what has been done so far in the LHC Olympics and what still remains to be done.

##### October 28

*Nongeometric Structures in String Theory*

**Brian Wecht**

MIT

Typically, one thinks of string theory as living in a

ten-dimensional background spacetime. It is becoming increasingly apparent

that this is not general enough, and in order to consider all backgrounds

one must include structures which even locally have no interpretation as

geometry. In this talk, I will describe what is known about nongeometric

backgrounds, and how their existence is forced on us by symmetries of

string theory. No previous knowlege about string theory will be assumed.

##### November 4

*Still trying to get V _{ub}*...

**Bjorne Lange**

MIT

I will talk about recent progress in our understanding of QCD effects in a precision measurement of

Vfrom inclusive B decays. Words like "shape functions", "jet functions", "OPE region" will dominate the discussion, but I do not assume prior knowledge about them and try to make it interesting for everybody. In essence this talk summarizes the three presentations I have given for Iain Stewart's group this semester, but at a less technical level._{ub}

##### November 18

*Gauge mediated supersymmetry breaking in the
Minimal Supersymmetric Standard Model*

**Wouter Waalewijn**

MIT

The Standard Model has been very succesful in describing nature and up to today no significant deviations have been found. There are however hints indicating that there should be more. One popular extension is supersymmetry. It turns out to be quite easy to make the Standard Model supersymmetric, but supersymmetry has to be broken and it is not clear how this should happen. Several models have been suggested, but all have certain disadvantages. In my talk I will first give an introduction on supersymmetry and how this can be put to practice for the Standard Model. After that I will focus on Gauge Mediated Supersymmetry Breaking, discuss the way it works and spend a little bit of time on its phenomenology.

##### December 2

*Some New Results on Time Dependence in String Theory*

**Matthew Headrick**

MIT

Whereas the conventional quantum field theories of particle physics live in a fixed spacetime, in string theory spacetime itself is represented by a quantum field theory. In this talk I will explain what I mean by this statement, from which it follows that the dynamics of string theory can be thought of as motion on the space of couplings of a QFT. I will then present recent results on the equations of motion of string theory, and how they relate to such familiar concepts from QFT as renormalization group flow.

##### December 9

*A Closed String Tachyon Vacuum and Rolling Tachyons*

**Haitang Yang**

MIT

I will talk about the evidence that the closed string field theory (OSFT) tachyon potential has a critical point and the physical decay induced by the the bulk bosonic closed string tachyon. The first question is about the existence of a stable vacuum of OSFT. At this stable vacuum, the space-time ceases to be dynamical. Then the low energy effective action is used to study the rolling process of the tachyon, when coupled to gravity and dilaton. We do

find that the Einstein metric collapses when the rolling solution is induced by tachyon. No previous knowlege about string theory will be assumed.