# Graduate Student Lunch Club

The CTP Lunch Club meets at 11 am every Friday (provided that there are sufficient speakers).

**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.

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: Elba Alonso-Monsalve, Joshua Lin and Zhiquan Sun.

February 19**Atakan Firat****Title:** Hyperbolic Three-String Vertex

In this talk, I begin developing tools to compute off-shell string amplitudes with the recently proposed hyperbolic string vertices of Costello and Zwiebach. Exploiting the relation between a boundary value problem for Liouville’s equation and a monodromy problem for a Fuchsian equation, I construct the local coordinates around the punctures for the generalized hyperbolic three-string vertex and investigate their various limits. This vertex corresponds to the general pants diagram with three boundary geodesics of unequal lengths. I derive the conservation laws associated with such vertex and compute the t^3 term in the closed string tachyon potential. I note the relevance of this construction to the calculations of the higher-order string vertices using the pants decomposition of hyperbolic Riemann surfaces. Based on 2102.03936.

February 26**Elba Alonso-Monsalve****Title:** Should I care about primordial black holes?

Ever wondered whether dark matter (DM) might be something other than a particle? In this talk I’ll introduce you to a lesser known, yet hefty, DM candidate: primordial black holes (PBH). I’ll explain how PBH may have formed in the early universe and take you for a walk around parameter space. I’d heard both that “PBH are definitely most of the DM” and that “PBH have been ruled out” from people I respect, so I set out to shed some light on this mystery. Come to learn some fun history, see pretty figures, hear about exciting experiments, and leave with an answer to the question “should I care about primordial black holes?”. Disclaimer: I don’t research PBH myself. If you have strong opinions on the topic, there will be plenty of time for discussion at the end.

March 5**Patrick Oare**

Title: **Short-Distance Nuclear Matrix Elements for Neutrinoless Double Beta Decay****Abstract**: Neutrinoless double beta decay is a long-sought after process which would provide evidence of lepton number violation in our universe. Computing the rate from first principles requires non-perturbative input in the form of a nuclear matrix element which must be computed on the lattice. In this talk, I will discuss the contribution to this matrix element from short-distance, dimension-9 operators. I will develop some of the methodology used to perform this computation on the lattice, and I will present some preliminary results in which we evaluate this matrix element on an ensemble of domain-wall fermions for the unphysical π- → π+ e- e- decay.

March 12**Johannes Michel**

Title: **Resummation for the LHC 101****Abstract:** Differential measurements at the LHC involve several physical scales set by the hard production process and the soft or collinear dynamics that contribute to the measurement and describe the incoming protons. When these scales are widely separated, the perturbative series becomes dominated by logarithms of their ratios. Precise (or, sometimes, even just convergent) theory predictions require the resummation of these logarithms to all orders. Focusing on the case of transverse momenta spectra, an important precision observable at the LHC, I give a pedagogical introduction to the key concepts of factorization and renormalization group evolution that achieve this resummation, and outline how they enter in state-of-the-art theory predictions that will help stress-test the Standard Model at the percent level.

March 19

**Xiaojun Yao**

Title: Baked Alaska in Heavy-Ion Collisions**Abstract**: I will explain everything you need to know to make baked Alaska in heavy-ion collisions. For those serious physicists, I will cover the basics of the quark-gluon plasma and explain how to use heavy-ion collisions to study its properties. Furthermore, I will review a particular probe of the quark-gluon plasma, quarkonium, which is the bound state of a heavy quark-antiquark pair. I will focus on physics ideas and try to connect the current interest of the heavy-ion community with the local CTP research activities.

March 26**Nicole Yunger-Halpern**

Title: **Quantum Politics**

Abstract: TBA

April 9**Josh Foster**

Title: TBA

Abstract: TBA

April 16**Siddharth Mishra Sharma**

Title: TBA

Abstract: TBA

April 23**Pouya Asadi**

Title: TBA

Abstract: TBA

April 30**Aasmund Folkestad**

Title: Holography Abhors Visible Trapped Surfaces

Abstract: TBA

May 7**MIT Student Holiday**

May 14**Manki Kim**

Title: TBA

Abstract: TBA

May 21**Wenzer Qin**

Title: Effective Field Theory of 21cm Cosmology

Abstract: TBA

May 28