# Joint Theory Seminar

## SS2019

### Schedule

Date Location Title Speaker Abstract
05.03.2019 -- no seminar -- No seminar this week.
12.03.2019 ESI Symmetric orbifolds and tensionless string field theory Joris Raeymaekers This talk is given as part of the programme of the Higher Spins and Holography conference.
I will give a pedestrian review of holography for symmetric orbifold CFT's. These include the tensionless string on $$AdS_3$$ as the example of interest, though I will illustrate the main idea in a toy model (the symmetric orbifold of a free scalar). The dual theory in the bulk can be formulated as a higher spin gauge theory with `higher spin square' gauge invariance. I will propose gauge-invariant field equations capturing some three-point couplings in this theory, including those of twisted sector fields.
19.03.2019 ESI Anti anti-de Sitter black holes Stéphane Detournay This talk is given as part of the programme of the Higher Spins and Holography conference.
Most known black holes in 3 dimensional space-times have an entropy that can be accounted for by Cardy-type counting formulas. In almost all of these cases, the match can be traced back to the presence of an $$(A)dS$$ factor either in the asymptotic or the near-horizon regions. In this talk I will focus on space-times devoid of this property and discuss some of their geometric and thermodynamic properties.
26.03.2019 ESI The Status of the String Landscape Savdeep Sethi This talk is given as part of the programme of the Higher Spins and Holography conference.
Whether string theory admits a multiverse of de Sitter solutions that look approximately like our universe is a hotly debated current topic. I will overview the basics of landscape constructions and explain my view on this question.
02.04.2019 UV Spectral dimension and other geometry estimators
in random fuzzy spaces
Lisa Glaser Random fuzzy spaces are a matrix model of non-commutative geometries. Calculating the path integral over these geometries numerically has shown indications of a phase transition, and given rise to the idea that the geometries at this phase transition might be two dimensional.To better understand these geometries and the phase transition we have explored spectral estimators for different geometric properties. In this talk, based on arXiv:1902.03590, I will introduce the ensemble of random fuzzy spaces and show some of the spectral estimators we constructed.
09.04.2019 TU Renormalization in large-N QCD and open/closed string duality Marco Bochicchio We demonstrate that the asymptotic freedom and renormalization group imply that the large-$$N$$ ’t Hooft expansion of the YM S-matrix is ultraviolet (UV) finite nonperturbatively, while the large-$$N$$ expansion of the QCD S matrix is only renormalizable, due to UV divergences starting from the order of $$N_f/N$$, with $$N_f$$ the number of quark flavors. We investigate the compatibility of the aforementioned renormalization properties with the existence of a supposed canonical string solution, matching the topology of ’t Hooft large-$$N$$ expansion, for the S matrix of large-$$N$$ YM theory and QCD. The UV finiteness of the large-$$N$$ YM S matrix is compatible with the universally believed UV finiteness of closed string theories. Yet, we demonstrate that the aforementioned renormalization properties of the large-$$N$$ QCD S matrix to the order of $$N_f/N$$ are incompatible with the open/closed string duality of the would-be canonical string solution, which therefore does not exist. We suggest a noncanonical way-out based on topological string on noncommutative twistor space.
16.04.2019 Easter break
23.04.2019 Easter break
30.04.2019 UV Abundant sets of internal spaces for string theory Harald Skarke String model building usually relies on compactification on a Calabi-Yau (CY) threefold or involves a construction known as F-theory which combines the data of the internal space and of some background fields into those of a CY fourfold. The most fertile construction method for CY manifolds comes from a branch of algebraic geometry known as toric geometry, where families of CY n-folds are associated to (n+1)-dimensional polytopes that have a certain property called reflexivity. I will explain the concepts introduced above. Then I will outline how we managed to classify all 476,800,776 reflexive 4-polytopes almost 20 years ago, thereby creating what is still the world's largest list of CY threefolds. Finally I will report on recent work on the classification of a particular class of reflexive 5-polytopes (there are 322,383,760,930), which resulted in the largest existing database for CY fourfolds.
07.05.2019 TU On positivity of energy in higher dimensions Piotr Chruściel I will review the notion of total energy of asymptotically flat and asymptotically hyperbolic manifolds in general relativity, and sketch the recent proof, together with Erwann Delay, of positivity of hyperbolic energy in all dimensions.
14.05.2019 UV Gravitational duality near cosmological space-times Sergio Hörtner We shall present a $$SO(2)$$ duality-symmetric form of the linearized ADM action principle on anti de Sitter and Kasner backgrounds. The analysis is based on the two-potential formalism, obtained upon resolution of the Hamiltonian constraints, and generalizes previous works that focused on Minkowski and de Sitter backgrounds.
21.05.2019 TU Euclidean Wormholes and Holography Olga Papadoulaki In this talk I will discuss asymptotically $$AdS$$ wormhole solutions in the context of holography. I will present how to compute correlation functions of local operators as well as non local observables such as correlation functions of Wilson loops on the distinct boundaries and I will discuss their behavior. Moreover, I will present deformations of the theory with multi-trace operators. From the computations mentioned we observe that, the dual theory is expected to factorize in the UV, and the two sectors to be coupled by a soft non-local interaction. Finally, I will present a simple effective field theory model that can model the behaviors that we observe from the gravity computations.
28.05.2019 UV A proposal for nonabelian mirrors in two-dimensional theories Eric Sharpe In this talk we will describe a proposal for nonabelian mirrors to two-dimensional $$(2,2)$$ supersymmetric gauge theories, generalizing the Hori-Vafa construction for abelian gauge theories. Specifically, we will describe a construction of B-twisted Landau-Ginzburg orbifolds whose classical physics encodes Coulomb branch relations (quantum cohomology), excluded loci, and correlation functions of A-twisted gauge theories. The proposal has been checked in a wide variety of cases, but the talk will focus on exploring the proposal in two examples: Grassmannians (constructed as $$U(k)$$ gauge theories with fundamental matter), and $$SO(2k)$$ gauge theories. If time permits, we will also discuss how this mirror proposal can be applied to test and refine recent predictions for IR behavior of pure supersymmetric $$SU(n)$$ gauge theories in two dimensions.
04.06.2019 TU On two-vierbein gravity action from gauge theory of conformal group Iva Lovrekovic TBA
11.06.2019 Pentecost/Pfingsten
18.06.2019 UV TBA René Meyer TBA
25.06.2019 TU TBA Jakub Vošmera TBA

The Joint Theory Seminar is held alternately at the University of Vienna and the Technische Universität Wien.

The Topic of the seminar is recent theoretical research in the areas of mathematical physics, high energy physics, physics of fundamental interactions and particle physics.

The target audience for the talks are PhDs, postdocs and faculty members.

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#### How to participate

###### Attending

Anyone can attend. If you are interested in a talk, just come.

###### Giving a talk

If you want to give a talk contact Raphaela or David.

#### Vienna Theory Lunch Seminiar

The Vienna Theory Lunch Seminar, which is held right before this seminar, might also be of interest to you.

### Location

##### Technische Universität Wien (TU)

Wiedner Hauptstraße 8

Yellow Area, 9th floor, Seminar Room (DB 09 E23)

##### University of Vienna (UV)

Boltzmangasse 5

5th floor, Erwin Schroedinger Lecture Hall

### Contact

##### Daniel Grumiller
###### Associate Prof. Dr.techn.

Black holes and holography

Technische Universität Wien

##### Stefan Fredenhagen
###### Univ.-Prof. Dr.

Mathematical physics

University of Vienna

##### Raphaela Wutte

Black holes and holography

Technische Universität Wien

##### David Erkinger

Mathematical physics

University of Vienna