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).
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 organizers, Andrew Lutomirski at luto_at_mit[dot]edu, and Evangelos Sfankianakis at esfaki_at_mit[dot]edu
Supercurrents and the Meissner effect in the Sakai-Sugimoto model
Bibliography Management Software
The matching of the spectrum of N=4 super Yang-Mills with that of type IIB string theory on an AdS_5 x S^5 background is central to the AdS/CFT correspondence. In recent year much progress has been made in the calculation of these spectra. To a large extent this progress has followed from the identification of integrable structures of both sides of the correspondence, and the resulting Bethe ansatz equations. However, these equations are only asymptotically valid and need to be adjusted due to finite-size effects. I will review how the Bethe ansatz equations appear in N=4 super Yang-Mills, and discuss how the leading finite-size corrections can be obtained.
Faculty and post-docs are welcome. There will be pad thai, hot basil
fried rice, and the usual assortment of soft drinks.
When Precision Physics meets SCET: a global Thrust fit for alphas(mZ)
Tons of data on jets have been accumulated by e+e- experiments run at particle accelerators, but they have not been fully exploited because of a lack of a theoretical description that is able to simultaneously describe all center of mass energies and kinematic regions in a coherent way. This is also reflected by the dominance of theoretical uncertainties in the usual determinations of the strong coupling constant from jet data.
We are now in a position to change this. Using SCET we are able to treat non perturbative contributions in a field theoretical way (without relying on Monte Carlo's), and consistently combine them with O(alphas^3) fixed order computations and a summation of large logs at next-to-next-to-next-to-leading order. The resulting computer package allows us to perform a GLOBAL fit to thrust, using all the available data, and therefore obtain a high precision determination of the strong coupling constant, alphas(mZ).
In this talk, I will give an overview of the theoretical methods behind our analysis and present the results of our fit.
Faculty and post-docs are welcome. Food TBD
Ice, Spin Ice, and Magnetic Monopoles
Infrared Renormalization group Flow for Heavy Quark Masses and QCD Matrix Elements
It is well known that perturbative expansions in quantum field theory are asymptotic, and that one place where this has direct implications for analyzing experimental data is for heavy quark masses. The asymptotic behavior of perturbation theory is effected by so-called renormalon ambiguities, and can be improved by defining short distance masses. A short distance mass depends on an infrared scale R controlling the absorption of infrared fluctuations, along side a renormalization scale mu. Treating R as a variable yields a new type of renormalization group flow equation, which I will demonstrate improves stability of conversion between mass schemes, allowing us to avoid large logs and the renormalon simultaneously. I will also show that this RGE allows one to quantify the strength of the order Lambda_QCD renormalon ambiguity in the heavy quark pole mass. Further I will generalize these ideas to consider higher order renormalons and other matrix elements in QCD.Faculty and post-docs are welcome.
Cosmological and astrophysical signatures of braneworld models
Braneworld models have been proposed as an alternative "explanation" for cosmic acceleration. I will discuss some interesting signatures of such models in the growth of structure and our solar system.
The talk will be in the usual place (6C-442 at noon), but it will be a bit shorter than usual due to a space conflict – we need to clear out at about 12:55 PM.
Lunch will be provided, although I haven't decided what we'll eat yet. Grad students and post-docs welcome.
Things all theorists should know about quantum gravity
Finding a consistent quantum theory of gravity is generally seen as the ultimate challenge of modern theoretical physics. I will attempt to review a few key results about quantum gravity that I feel any theorist should be familiar with:
- How to derive GR from a quantum field theory with a massless spin-2 particle
- Why the quantum theory looks non-renormalizable and how serious a problem this is
- The large and small cosmological constant problems
- The relation between Lorentz invariance, spin-2 gauge symmetry, general coordinate invariance, and the principle of equivalence
- The conserved gravitational stress-energy tensor and why it's not a local observable
My discussion will rely heavily on Steven Weinberg's work on the subject, from the mid 1960's to the early 1980's. The talk is intended for graduate students, but postdocs and faculty are welcome.
As usual, the talk will be in the large seminar room. Food TBD.
On quasinormal modes of Rotating Black Holes and Area Quantization
Perturbations of black holes give very important tools for understanding physical properties of black holes. The relaxation of the perturbation is described by quasinormal modes with complex frequency. Using this, there has been some phenomenological proposals that one can obtain quantization of the area of black holes. This idea, when applied to rotating black holes were less than controversial. Here we will address the area quantization of rotating black holes. We also comment on application of this to other black holes in 3 dimensional spacetime.
Everyone's invited, and we'll have Brazilian food again.
Questions in Bound State Physics
Bound state physics is a rich area for phenomenological physics, but presents numerous challenges for doing first-principles theoretical physics calculations. In this talk I will go over some of the successes, problems, and failures with respect to spin physics in hadrons. I will close with some work I have been doing along different avenues to tackle some of these questions in bound state physics.
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