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Quantum Fields and Strings

This series consists of talks in the area of Quantum Fields and Strings.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Mardi nov 03, 2015
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Quantum field theory on curved space has long been studied for its interesting phenomenology, and more recently also as a means to obtain non-perturbative results in supersymmetric theories. In this talk I will describe the holographic dual for N=4 SYM coupled to massive N=2 flavors on spaces of constant curvature. With that in hand, I will discuss a topology-changing phase transition on S^4 and confront holographic computations with exact field theory results obtained using supersymmetric localization.

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Mardi oct 27, 2015
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We consider quantum quench from a gapped to a gapless system in 1+1 dimensions. We

provide a rigorous proof of the thermalization of the reduced density matrix, hence that of

an arbitrary string of local operators in an interval. In case the system is integrable, the "thermalization" leads to a generalized Gibbs ensemble (GGE). We model the critical quench in terms of an initial state in terms of a conformal boundary state deformed by exponential cutoffs involving hamiltonian and other charges. We justify this choice of the initial state by explicitly

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Lundi oct 26, 2015
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I will revisit the A-twisted gauged linear sigma model (GLSM) in the case of (2,2) supersymmetry in two dimensions, and its Omega-background deformation. Exact results for correlation functions on the sphere can be obtained in terms of Jeffrey-Kirwan residues on the Coulomb branch, which has a number of interesting applications. I will also explain an interesting generalization to (0,2) supersymmetric GLSMs of a special type.

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Mardi oct 20, 2015
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I will describe entanglement entropy of a cap-like region for a generic quantum field theory residing in the Bunch-Davies vacuum on de Sitter space. Entanglement entropy in this setup is identical with the thermal entropy in the static patch of de Sitter, and it is possible to derive a simple relation between the vacuum expectation value of the energy-momentum tensor trace and the RG flow of entanglement entropy. In particular, renormalization of the cosmological constant and logarithmic divergence of the entanglement entropy are interrelated in this setup.

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Lundi oct 19, 2015
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In this talk I will discuss the most singular point and T^2 compactifications of a 6d N=(1,0) supersymmetric conformal field theory (SCFT) which arises as the worldvolume theory on coincident N of M5 branes probing the singular locus of the ALE orbifold. When N=1, the compactified theory can be describe by a class S theory of three punctured sphere. Generalization to multiple M5s case results in a pair of 4d N=2 SCFTs which are connected by a IR free gauge multiplet. Along the line, we see that the “dynamical version" of class S simple puncture plays a role.

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Mardi oct 13, 2015

We derive the constitutive relations of first order charged hydrodynamics for theories with Lifshitz scaling and broken parity in 2+1 and 3+1 spacetime dimensions. In addition to the anomalous (in 3+1) or Hall (in 2+1) transport of relativistic hydrodynamics, there is an additional non-dissipative transport allowed by the absence of boost invariance. We analyze the non-relativistic limit and use a phenomenological model of a strange metal

to argue that these effects can be measured in principle by using electromagnetic fields with non-zero gradients.

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Mardi oct 06, 2015
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I will discuss the Higgs-branch CFT2 dual to string theory on AdS3 x S3 x T4. States localised near the small instanton singularity can be described in terms of vector multiplet variables. This theory has a planar, weak-coupling limit, in which anomalous dimensions of single-trace composite operators can be calculated. At one loop, the calculation reduces to finding the spectrum of a spin chain with nearest-neighbour interactions.

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Mardi sep 29, 2015
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I will overview recent progress in understanding Weyl anomalies and the a-theorem in supersymmetric six-dimensional field theories.

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Lundi sep 28, 2015
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String theory is starting to provide novel all-loop precision tools for the computation of scattering amplitudes in the high energy (HE) limit of N=4 SYM theory. After a review of some key insights and results for hexagon amplitudes, I will describe ongoing developments addressing higher numbers of external gluons.

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Vendredi sep 25, 2015
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I will discuss how to classify (up to discrete identifications) all rigid 4D N=2 supersymmetric backgrounds in both Lorentzian and Euclidean signatures that preserve eight real supercharges. These include backgrounds such as warped S_3×R, warped AdS_3×R, and AdS_2×S^2, as well as some more exotic geometries. I will also address how to construct all supersymmetric two-derivative actions involving hypermultiplets and vector multiplets in these backgrounds.

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