2017-2018 Postgraduate seminars
First term meetings take place on Tuesday
at 13:45, Room 54/8031 -- unless otherwise specified --
Schedule:
- 03/10/17 - Introductory Meeting
- 10/10/17 - Marika
- 18/10/17 - Aaron ***3 pm, Room 54/7033 (7C)***
- 24/10/17 - David Turton - String Theory Seminar
- 31/10/17 - Panos Betzios - String Theory Seminar
- 07/11/17 - Ramon
- 14/11/17 - CANCELLED
- 21/11/17 - Kazem Bitaghsir Fadafan - String Theory Seminar
- 28/11/17 - Carlos
- 05/12/17 - Federico
- 12/12/17 - Beth
[ winter break Sunday 17 December 2017 - Sunday 7 January 2018 ]
- 30/01/18 - Joan
- 06/02/18 - Ramon
- 13/02/18 - Masanori
- 20/02/18 - Anton
- 27/02/18 - Arpan Bhattacharyya (Yukawa Inst., Kyoto U.) - String Theory Seminar
- 06/03/18 - Olga
- 13/03/18 - CANCELLED
[ spring break Sunday 18 March 2018 - Sunday 15 April 2018 ]
- 17/04/18 - Georgios Papathanasiou (DESY) - String Theory Seminar
- 24/04/18 - Ioannis Papadimitriou (KIAS) - String Theory Seminar
- 01/05/18 - CANCELLED
- 02/05/18 - Andy ***15:15, Room 54/7033 (7C)***
- 08/05/18 - Oliver Schlotterer (AEI Potsdam) - String Theory Seminar
- 15/05/18 - CANCELLED
Wiki Page:
Topics:
1. Out-of- time- correlators/ Chaos
2. SYK/ Melonic diagrams
3. LIGO
4. Dualities (Seiberg)
5. Bulk reconstruction/ Traversable Wormholes/ Complexity/ Black Holes
6. Weak Gravity Conjecture/ Swampland
7. Exotic Branes
8. BMS/ Soft Theorems
Talks Details:
Journal Club: 02/05 at 15:15, Room 54/7033
- Andy is going to talk about T Tbar deformation, especially for the following paper by Cardy
https://arxiv.org/abs/1801.06895
Cardy is building on work initiated by Zamolodchikov and then developed by many others here are some more references:
https://arxiv.org/abs/hep-th/0401146
https://arxiv.org/abs/1608.05499
https://arxiv.org/abs/1608.05534
https://arxiv.org/abs/1611.03470
https://arxiv.org/abs/1706.06604
https://arxiv.org/abs/1801.02714
Journal Club: 06/03 at 13:45, Room 54/8031
- Olga is going to talk about Gerard 't Hooft's ideas on black holes
- Basic reference:
http://www.staff.science.uu.nl/~hooft101/lectures/GtHBlackHole_2018.pdf
Journal Club: 20/02 at 13:45, Room 54/8031
- Anton is going to talk about
"Higher Spin Gauge theories and Holographic duals" :
It is known that string theory contains an infinite tower of massive Higher Spin fields (Regge spectra). For appropriate length scale we can obtain either low energy irrelevant massive modes or tensionless limit, where the latter corresponds to the tower of massless HS fields and theory contains HS gauge symmetry. It is expected that HS gauge algebra underlies string theory and Higgsed form of the symmetry leads to a massive infinite tower. Though initially HS was formulated for flat backgrounds (Fronsdal), a compete (non-linear) HS formalism for Einstein gravity can be formulated in terms of Vasiliev equations (by infinite auxiliary fields in dS/AdS), physical implications of unfolded formalism are of current active research. HS theory provides D=3,4 bulk duals for particular CFTs (HS/CFT) and might find applications in twistor geometry (SA).
Journal Club: 13/02 at 13:45, Room 54/8031
- Masanori is going to talk about
"(New) Universality in Chaos and Random Matrix Theory"
Abstract:
In the first half, I will explain well-know "late-time" universality in quantum chaos. I will try to convince you that,
while this universality is useful for certain purpose, in some sense this universality describes "universally boring" physics.
In the second half, I will suggest a new "early-time" universality, both in classical and quantum chaos.
I will argue why it can be more fun.
Journal Club: 06/02 at 13:45, Room 54/8031
- Ramon is going to talk about
"The TTbar deformation and holography"
This is not going to be a talk by me, but the intention is to do as last week with Joan, and other times in the Journal Club. I will have things to say and explain, but if anyone knows better, they can come along or start a discussion.
I will first talk about the TTbar deformation, references hep-th/0401146 and 1608.05499
Then about recent attempts to relate this deformation to holography 1611.03470 and 1801.02714
Other references include 1608.055341710.084151801.09708
Journal Club: 30/01 at 13:00, Room 54/8031
- Joan is going to talk about Holographic Complexity
Abstract:
The aim will be to have a discussion about holographic complexity. We will see the idea behind the conjectures 'complexity = volume' and 'complexity = action', and if time allows we will finish with the main result presented in https://arxiv.org/pdf/1709.10184.pdf .
More references:
https://arxiv.org/pdf/1406.2678.pdf
https://arxiv.org/pdf/1509.07876.pdf
Journal Club: 12/12 at 13:15, Room 34/4005
- Beth is going to talk about Holographic Cosmology
Abstract:
The holographic cosmology framework expresses inflationary predictions
in terms of the observables of a 3D quantum field theory (QFT). It
predicts two possible regimes for power spectra of primordial curvature
perturbations. The first is well approximated by the standard power law
expansion (for strongly coupled QFT), while the second is a new
holographic expansion, dual to a weakly coupled QFT in the UV, but
strong coupling in the IR. We compare the two regimes against the state
of the art cosmological observations and show that they do equally well
at l>30, where a holographic perturbative expansion can be trusted.
However, the (naive) holographic expansion is disfavored by data at
low l's at ~2 sigma level.
- Basic References:
https://arxiv.org/pdf/1607.04878.pdf
https://arxiv.org/pdf/1703.05385.pdf
Journal Club: 05/12 at 13:00, Room 34/4005
- Federico is going to talk about
" The BMS group: an overview "
I will give an overview of the BMS group and why it has raised a lot of interest recently.
The talk will be both an introduction to what we already know about it and a brief discussion of what I'm doing currently (BMS in higher dimensions). In doing so I'll cover some subtle aspects concerning the BMS group in 4 dimensions, including the debate on the proper definition of asymptotic flatness and the charges associated to BMS supertranslations and superrotations. If time permits I will give an idea of how the BMS transformations are related to Weinberg soft theorems and to the problem of IR divergences in quantum gauge theories.
- Basic References:
arXiv:1510.03386v4 and arXiv:1312.2229v2
Journal Club: 28/11 at 13:15, Room 34/4005
- Carlos is going to talk about
Title: Double-copy structure of one-loop open-string amplitudes
Abstract:
In this talk I will report on a surprising duality
between BRST invariants in pure spinor superspace and elliptic
functions on a genus-one Riemann surface.
Kinematic identities that are valid up to BRST-exact terms have
corresponding elliptic duals that vanish up to total derivatives
on moduli space. These relations were found in pursuit of a general
expression for the one-loop open string correlators and they reveal
an underlying double-copy structure in the open string: replacing
one copy of elliptic functions by its kinematic dual in
the open string leads to gravitational matrix elements of the
(supersymmetrized) R^4 operator.
- Basic References:
Journal Club: 14/11 at 13:00, Room 34/4005
CANCELLED
Journal Club: 07/11 at 13:00, Room 34/4005
- Ramon is going to talk about his own work
"Instabilities of charged black holes and small hairy black holes"
Reissner-Nordstrom black holes (RN BH) in AdS suffer from two linear instabilities, superradiance and the near horizon instability. The endpoint of these instabilities is a hairy black hole. I will present an analytic perturbative construction of these hairy black holes and analyse the phase space of solutions. In asymptotically flat spacetime, inspired by the black hole bomb of Press and Teukolsky, one can surround a RN BH by a reflecting box. It is known that this system suffers from superradiant instability. We show that the near horizon instability is also present there. As in the AdS case, the endpoint is a hairy black hole that we construct analytically in a perturbative expansion. We comment on the matter content of the box.
- Basic References:
https://arxiv.org/pdf/1610.03496.pdf
Journal Club: 18/10 at 15:00, Room 54/7033(3C)
- Aaron is going to talk about SYK.
- Basic References:
https://arxiv.org/pdf/1606.01857.pdf
Journal Club: 10/10 at 13:00, Room 34/4005
- Marika is going to talk about SYK.
- Basic References:
https://arxiv.org/pdf/1604.07818.pdf
https://arxiv.org/pdf/1503.01409.pdf
https://arxiv.org/pdf/1608.07018.pdf
https://arxiv.org/pdf/1706.07812.pdf
https://arxiv.org/pdf/1610.09758.pdf
https://arxiv.org/pdf/1706.05362.pdf
- Introductory Meeting - 03/10
The aim of this first meeting is to discuss about the format of the seminars, to allocate time slots and decide on the topics.
Currently, the idea is to have each of us presenting their work or interesting papers that we want to understand better. Moreover, if someone has to give a talk at another institution, they can use this seminar as an opportunity to rehearse their talk in a friendly environment.
There is also the possibility to have a small discussion in the beginning of each seminar (about 10- 20 minutes) for papers that we saw on arXiv the week before and then to move on to the actual talk.
Any suggestions are welcome, please bring them forward during the first meeting.