Found 12 result(s)

### 15.11.2021 (Monday)

#### Lonti: An Introduction to Observables in Gauge Theories

 at: 10:30 Otherroom Online abstract: Lonti Autumn 2021 Series: Lecture 4. Live Tutorial. Please register at https://lonti.weebly.com/registration.html to receive joining instructions for this live session which will be held via Zoom. Gauge theories are ubiquitous in theoretical physics, not to mention that the standard model is one. It is therefore of utmost importance to know what the observables of these theories are, quantities that can be calculated and measured. I start with a long discussion based on the most familiar gauge theory, Maxwell's electromagnetism, where a lot of computations can be done explicitly. I then take the lessons from that to non-abelian gauge theories. The observables covered are local, Wilson loops, and briefly 't Hooft loops and surface operators.

### 08.11.2021 (Monday)

#### Lonti: An Introduction to Observables in Gauge Theories

 at: 10:00 Otherroom Youtube abstract: Lonti Autumn 2021 Series: Lecture 4. Release of Recorded Lecture. Available at https://youtu.be/JLbuSnt2OyA. Gauge theories are ubiquitous in theoretical physics, not to mention that the standard model is one. It is therefore of utmost importance to know what the observables of these theories are, quantities that can be calculated and measured. I start with a long discussion based on the most familiar gauge theory, Maxwell's electromagnetism, where a lot of computations can be done explicitly. I then take the lessons from that to non-abelian gauge theories. The observables covered are local, Wilson loops, and briefly 't Hooft loops and surface operators.

### 14.01.2020 (Tuesday)

#### Moduli spaces of BPS Wilson loops in 3d and quiver varieties

Regular Seminar Nadav Drukker (King's College London)

 at: 13:30 ICroom H503 abstract: In this talk I will reexamine the classification of BPS Wilson loops in 3d super Chern-Simons-matter theories. Over the last several years a large class of increasingly intricate constructions of such operators have been found. They involve both discrete and continuous parameters chosen to satisfy varied conditions. In my talk I will explain that the discrete parameters are related to choosing a graded quiver diagram, which may be a subquiver or a cover of the one defining the theory. The continuous parameters are then a singular limit of the variety, a complex manifold, associated to that quiver.

### 24.01.2017 (Tuesday)

#### Matrix models for the gauge-gravity correspondence

 at: 15:00 City U.room B103 abstract: The gauge-gravity correspondence identifies a field theory with a gravitational theory. The gravitational theory is weakly coupled when the field theory has large coupling and vice versa, which mostly prevents matching nontrivial results between the two descriptions. I will discuss cases when the field theory calculation can be reduced to a finite dimensional matrix integral, representing some counting problems. I will then evaluate the integral exactly and reexpand the exact result, which is valid for all coupling, at strong coupling. The resulting expression should match a weak coupling gravitational (or string theoretic) calculation and Iâ€™ll comment on what is known from that direction.

### 20.01.2016 (Wednesday)

#### Polygon Seminar: SUSY field theories and matrix models

 at: 15:00 ICroom LT3 Level 1 Blackett abstract: Matrix models are toy models for quantum field theories. They can be extremely complicated but can also be solved in a variety of ways. In my talk I will discuss general properties of matrix models and their solutions and focus on particular matrix models that arise in the study of 4d SUSY field theories. Those matrix models describe the index of the field theory, counting the number of states of the theory (with + sign for a boson and - for a fermion) and have been known for over 10 years. Though they look very complicated I will show how some simple tricks allow in certain cases to solve those matrix models exactly in terms of elementary functions. My talk will focus on the matrix model calculation and no specialized knowledge of SUSY field theories or indices would be required to follow it.

### 10.12.2014 (Wednesday)

#### Localization and quantum AdS_4/CFT_3 holography

Regular Seminar Nadav Drukker (King's College)

 at: 14:00 ICroom H139 abstract: I will review the calculation of the partition function of 3d supersymmetric field theories on S^3 using the fermi-gas approach to solve the matrix integral. The resulting expression is an Airy function and is valid perturbatively to all orders in 1/N for a wide class of theories (including ABJM). This suggests that a similar formula can be derived by studying quantum gravity on AdS_4. I will explain several of the steps needed to implement this idea and some intriguing results.

### 22.02.2012 (Wednesday)

#### Generalized quark antiquark potential and the TBTBA.

 at: 15:30 KCLroom Edmond J Safra Lecture Theatre abstract: Note: Sunil Mukhi's talk was cancelled!

### 10.02.2011 (Thursday)

#### (de)Tails of Toda CFT

 at: 14:00 QMWroom 602 abstract:

### 20.10.2010 (Wednesday)

#### A supermatrix model for ABJM theory

 at: 13:15 KCLroom 423 abstract: I will review the matrix model which calculates the partition function of ABJM theory on S3 as well as the expectation value of Wilson loop operators. I will then explain how this matrix model is solved and present the results for these quantities at all values of the couplings. At strong coupling these calculations reproduce the results of supergravity on Ads4 x CP3 and in particular the N to the 3/2 scaling of the free energy of the theory.

### 04.02.2010 (Thursday)

#### A supermatrix model for super-Chern-Simons-Matter

 at: 12:00 ICroom Blackett 741 abstract: I will present the 1/2 BPS Wilson loop operator of N=6 super Chern- Simons-matter (ABJM theory) which is dual to the simplest macroscopic open string in AdS4 x CP3. The Wilson loop couples, in addition to the gauge and scalar fields of the theory, also to the fermions in the bi-fundamental representation of the U(N) x U(M) gauge group. These ingredients are naturally combined into a superconnection whose holonomy gives the Wilson loop, which can be defined for any representation of the supergroup U(NlM). Using the localization calculation of Kapustin et al. I will then show that the circular loop is computed by a supermatrix model and discuss the connection to pure Chern-Simons theory with supergroup U(NlM).