The CTP Lunch Club meets every Friday at noon in the Cosman seminar room, 6C-442 (provided that there are sufficient speakers). Pizza will be provided begining at 11:55am.

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, Michael Crossley at mikeyc[at]mit[dot]edu, Paolo Glorioso at paolo_g[at]mit[dot]edu, and Yifan Wang at yifan[at]mit[dot]edu.

- February 10

Ethan Dyer

Stückelberging Anomalies and the Heterotic String

The heterotic string is an interesting playground for studying string compactifications. In addition to its positive phenomenological attributes, heterotic backgrounds allow the study of interesting geometric spaces, for which the mathematical tools lag behind the field theoretic ones. In this talk I will provide a strings-free introduction to how to understand anomalous gauge theories as perfectly good effective field theories, the basics of the gauge linear sigma model, and ultimately conclude with how these can be combined to yield interesting backgrounds for the heterotic string.

*Faculty and postdocs are welcome.* - February 17

Yasunori Nomura

Quantum Mechanics, Gravity, and the Multiverse

The discovery of the accelerating universe has led to the dramatic new view that our universe may be one of the many universes in which low energy physical laws take different forms: the multiverse. I explain why/how this view is supported both observationally and theoretically, especially by string theory and eternal inflation. I then describe how quantum mechanics plays a crucial role in understanding the multiverse, even at the largest distance scales. The resulting picture leads to a revolutionary change of our view on spacetime and gravity, and provides complete unification of the eternally inflating multiverse and many worlds in quantum mechanics. The talk is based mainly on the work presented in arXiv:1104.2324 and arXiv:1110.4630. (The content of the latter is a new part beyond what I talked at MIT the last time I visited.)

*Faculty and postdocs are welcome.* -
February 24

Fabio Franchini

Random Matrices, Topological Strings & Anderson Transition?

After a quick introduction on the ubiquity of (random) matrix models in theoretical physics, I will provide an overview of the non-perturbative technique of orthogonal polynomials. Then I'll discuss a peculiar matrix ensemble, sometimes known as "weakly confined", for which the probability distribution asymptotically approaches a log-normal. These models do not belong to the standard universality class and have intermediate eigenvalue distribution, which is neither Wigner-Dyson, nor Poisson. Recently, it was shown that they have the same partition function as some Chern-Simons theories and thus can describe certain topological string theories. Moreover, as the confinement grows weaker, the eigenvalues crystallize and tend to localize the eigenvectors, indicating a spontaneous breaking of the U(N) symmetry, which can be interpreted as a signature of the Anderson Metal/Insulator Transition.

*Faculty and postdocs are welcome.* -
March 2

Daniel Park

Bubble Nucleation and Correlators in CDL Backgrounds

Although we have had much success on thinking about quantum gravity in asymptotically AdS spaces through the AdS/CFT correspondence, going beyond AdS is still a challenge. There are many proposals on how to think about quantum gravity beyond AdS inspired by the success of holography. One such proposal put forth by Freivogel, Sekino, Susskind and Yeh goes by the name of FRW-CFT. FRW-CFT builds upon the fact that it is natural to have bubble nucleation in de Sitter backgrounds and proposes that there is a dual to the gravity theory living at the boundary of the FRW patch inside the bubble wall. I show that the correlators in these bubble backgrounds have nice structure that serve as circumstantial evidence for such a holographic correspondence.

*Faculty and postdocs are welcome.* -
March 9

Shelby Kimmel

The quantum query complexity of read-many formulas

We would like to use quantum computers to evaluate Boolean formulas, yet for many specific Boolean formula evaluation problems, the optimal quantum algorithm is not known. I will describe an algorithm that is optimal for general, "read-many" Boolean formulas. The tools developed for this algorithm have applications to other (less general) Boolean formulas, and to classical circuit complexity.

*Faculty and postdocs are welcome.* -
March 16

Andrea Allais

A quantum electron star

The holographic conjecture is the conjecture of the existence of a strong-coupling/weak-coupling duality between certain quantum field theories and certain theories of quantum gravity with one additional dimension. It can be used to shed some light in the strong coupling regime of quantum field theory. After a brief introduction, I will report recent progress in developing a holographic approach to strongly interacting fermions at finite density.

*Faculty and postdocs are welcome.* -
March 23

Matthew McCullough

Flavor Mediation Delivers Natural SUSY

I will talk about Natural Supersymmetry, first discussing the implications of recent LHC bounds for weak-scale SUSY as a natural solution to the hierarchy problem, and then covering some recent theoretical developments, with a focus on 'Flavor Mediation'.

*Faculty and postdocs are welcome.* -
April 6

Jae Hoon Lee

How to use gauge theories to study CY geometries

In string theory, strings probe geometry differently from particles due to their extended nature. In this talk, I will talk about how one can study this stringy geometry using 2d gauge theories by technique called Gauged Linear Sigma Models(GLSM). I will first introduce and explain what GLSM is and how it is related to NLSMs; the natural worldsheet description of string theory. Then using an explicit example in GLSM, I will describe how one simply constructs a geometry of one's interest (especially Calabi-Yau) and how to learn about its property as a string background. The talk will be accessible with some familiarity with QFT. Prior knowledge on supersymmetry and string theory will be helpful but not necessary.

*Students and post-docs are welcome.* -
April 13

Sho Yaida

Disordered Holographic Systems

I will first review what quenched (time-independent) disorder is and what they can do. Then we see how quenched disorder can be set up in holographic systems. After presenting my work with Allan Adams, I will conclude with speculations.

*Faculty and post-docs are welcome.* -
April 27

Brian Swingle

How entangled can quantum ground states be?

I will give an informal introduction (with lots of examples) to the question of maximal entanglement in local quantum systems. Audience participation will be encouraged. For example, we want to know how fast the entanglement entropy can scale with subsystem size. This question is crucially important for understanding the global structure of quantum ground states as well as for improving various entanglement based numerical approaches. I will introduce some recent ideas that may help answer this question and construct new physical examples that are highly entangled.

*Faculty and post-docs are welcome.* -
May 11

David Mross

Stripe melting and quantum criticality in correlated metals

Motivated by High-Tc experiments, I will discuss the possible fate of an electronic Fermi-surface coupled to a stripe (static charge modulations at some finite wave-vector) order parameter. Close to a quantum critical point where the order melts, weak-coupling approaches are problematic and no controlled theory is known. I will present a tractable strong-coupling theory of such a melting transition, from which various physical properties can be extracted. The focus will lie on a field theoretical description, and no in-depth knowledge of solid-state physics will be required.

*Faculty and post-docs are welcome.* -
May 18

Daniele Bertolini

Visible Supersymmetry Breaking?

Keith, Jesse and I asked ourselves the following question: 'Is it possible to break supersymmetry in the visible sector?' After some work we provided an answer and I will try to explain why should we matter at all about this, what is our answer, and what that answer unexpectedly brings about in Higgs phenomenology.

*Faculty and post-docs are welcome.*

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