33rd Nordic Network Meeting on "Strings, Fields and Branes"

29 Oct 2024, 09:00 → 31 Oct 2024, 17:00 Europe/Stockholm

Albano 2: C2207 - Auditorium 4 (80 seats) (Albano Building 2)

Henrik Johansson (Uppsala University, Nordita), Konstantin Zarembo (Stockholm University, Nordita), Magdalena Larfors (Uppsala University), Paolo Di Vecchia (Stockholm University, Nordita), Watse Sybesma (University of Cambridge)

Venue

Nordita, Stockholm, Sweden

Zoom link:
https://eu01web.zoom.us/j/9437491344?pwd=ZTQyWHFENjR4ZlBReWtBdG0yWlpoQT09&omn=66829800888

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Scope

The Nordic Meetings on "Strings, Fields and Branes" started as informal meetings around 1994-1995 and have since been hosted in turn by various institutes in the Nordic countries. This series of meetings is intended to especially provide opportunities for (PhD) students and early postdoc researchers in High Energy Theory physics and related topics working within the Nordic community to interact, exchange ideas, and give presentations. The meeting also aims to put students and junior researchers in contact with the forefront of current research in the field, through a series of pedagogical lectures by leading experts on topics of significant recent interest. More senior people are also warmly invited to attend!

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Preliminary programme schedule

This year we organize the meeting starting from 12:55 on Tuesday 29 October 2024 until 14:30 on Thursday 31 October. The conference dinner is scheduled on the evening of Wednesday 30 October. The programme will consist of three longer talks and shorter talks about exciting new research. You can register to give a short talk. In addition there will be two 'career' talks by speakers with a HEPTH background.

BONUS:

On Thursday at 15:30 there is the opportunity to attend the Oskar Klein Lecture, a separate event, given by Renata Kallosh.

 

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Invited speakers

Long talks:

• Bo Sundborg (Stockholm University) 
• Nele Callebaut (Cologne University) 
• Pietro Longhi (Uppsala University) 
  
  

Career talks:

• David Marsh (Stockholm University)
• Marjorie Schillo (EliseAI) 
  
  

Regular talks:

• Alexia Nix (University of Iceland)
• Andrea Sangiovanni (Uppsala University)
• Anton Nedelin (King's College London)
• Emil Have (Niels Bohr Institute)
• Evangelos Tsolakidis (University of Iceland)
• Ingrid Vazquez-Holm (Uppsala University and Nordita)
• Istvan Mate Szecsenyi (U. of Modena and Reggie Emilia)
• Marcus Sperling (University of Vienna)
• Martin Cederwall (Chalmers)
• Matthias Harksen (University of Iceland)
• Max Huebner (Uppsala)
• Niels Obers (Niels Bohr Institute and Nordita)
• Oscar Henriksson (Åbo Akademi University)
• Roman Mauch (Uppsala University)
• Shani Nadir Meynet (Uppsala University)
• Troels Harmark (Niels Bohr Institute)
• Victor Mishnyakov (Nordita)
• Vincent Van Hemelryck (Uppsala University)
• Vyshnav Mohan (University of Iceland)
• William Lindved (University of Edinburgh)

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Accommodation

Nordita has reserved a block of rooms at the following hotels:

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Elite Hotel Arcadia | 10 rooms for single or double use - For details and reserving a room, click here. Last day to book your room is 30th of September.

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Biz Apartment Gärdet | 15 Studio small (single-use) - For reserving a room, contact at reservations@bizapartment.se. You can inform the hotel that you are making a reservation for the workshop by referring the code SFB. Last day to book your room is 30th of September.

Nightly rate for studio small - 1295 SEK/night incl. breakfast 

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All reservations, payments, date adjustments and/or cancellations are to be made by the interested participant directly with the hotels.

Please be aware that scammers sometimes approach participants claiming to be able to provide accommodation and asking for credit card details. Do not give this information to them! If you are in any doubt about the legitimacy of an approach, please get in contact with the organizers.

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Financial support

Unfortunately, we will not be able to provide financial support towards travel or accommodation. However, lunches, coffee breaks and the dinner on Wednesday are complementary.

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Application/Registration

We have two deadlines. The first deadline is 8 September 2024, for those who also want to be considered to give a talk. The second deadline is 30 September 2024, for those who just want to attend. Digital attendance is possible. Due to venue restrictions we will prioritize people with Nordic affiliations (Groningen included).

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History

The Nordic Meetings on "Strings, Fields and Branes" (originally called Nordic meetings on "Supersymmetric Field and String Theories") started as informal meetings around 1994-1995 and have since been hosted in turn by various institutes in the Nordic countries.

An incomplete list of the previous meetings is as follows:

Meeting #	Location	Dates
1	Copenhagen	30/8-4/9/1993
2	Stockholm/Copenhagen?	1994/1995?
3	Stockholm	6-8/5/1996
4	Gothenburg	9-11/9/1996
5	Helsinki	10-12/3/1997
6	?
7	Uppsala	24-26/11/1997
8	Stockholm	9-12/3/1998
9	Gothenburg	17-19/8/1998
10	Helsinki	2-4/12/1999
11	Copenhagen	4-6/5/2000
12	Gothenburg	16-18/11/2000
13	Uppsala	3-5/5/2001
14	Stockholm	15-17/11/2001
15	Karlstad	9-11/5/2002
16	Copenhagen	28-30/11/2002
17	Oslo	8-10/5/2003
18	Groningen	13-15/5/2004
19	Uppsala	18-20/11/2004
20	Helsinki	27-28/10/2005
21	Stockholm	15-17/2/2007
22	Stockholm	27-29/11/2008
23	Copenhagen	16-18/4/2009
24	Groningen	3-5/12/2009
25	Stockholm	25-27/3/2010
26	Gothenburg	21-23/10/2010
27	Copenhagen	24-26/3/2011
28	Stockholm	1-3/12/2011
29	Nordita	7-9/11/2013
30	Nordita	22-24/11/2021
31	Copenhagen	14-16/11/2022
32	Stavanger	4-6/12/2023
33	Nordita	29-31/10/2024

 

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Sponsored by:

Tuesday 29 October

13:00 → 14:00 Quantum scalar fields in D=4: What have we missed?

I review some background, as well as recent developments and puzzles which may shed light on old problems with scalar QFTs. Scalar fields are ubiquitous in string theory and cornerstones in inflationary models. They are both central and alien to the Standard Model. Many problems are tamed by symmetries, but it would be interesting with other alternatives.

Speaker: Bo Sundborg (Stockholm University)

Quantum scalar fields in D=4 — Nordic Network.pdf

14:00 → 14:40 Coffee break

14:40 → 15:00 BV actions for extended geometry

I present a first order formulation of gravitational theories which is suitable for constructing their dynamics, in particular when the structure group is infinite-dimensional, and which leads to Batalin-Vilkovisky actions for extended geometry.

Speaker: Martin Cederwall (Chalmers Univ. of Technology)

talk-cederwall.pdf

15:00 → 15:20 A deformed Schwarzian action

Motivated in finding a non-relativistic counterpart of the conjectured duality between the Jackiw-Teitelboim (JT) gravity model and the quantum mechanical Sachdev-Ye-Kitaev (SYK) model we consider a two dimensional dilaton model with Lifshitz-like symmetries. We show how this dilaton model arises from a dimensional reduction of a Lifshitz-like black hole. We derive a one dimensional Lifshitz boundary action which only retains U(1) symmetries (as opposed to the SL(2,R) symmetries of the Schwarzian action) and use this boundary action to compute logarithmic corrections to the entropy of the Lifshitz-like black hole.

Speaker: Matthias Harksen (University of Iceland)

matthias-harksen.pdf

15:20 → 15:40 Toward double copy on arbitrary backgrounds

Double copy relates scattering amplitudes in a web of gravitational and gauge theories. Although it has seen great success when applied to amplitudes in vacuum, far less is known about double copy in arbitrary gravitational and gauge backgrounds. Focussing on the simplest pair production amplitudes of scalar QCD in a background gauge field, we construct, at next-to-leading order in perturbation theory, a double copy map to particle production in general metrics constructed from the gauge background. We connect our results to convolutional and classical double copy and, turning to examples, identify a class of gauge fields which generate FRW spacetimes via double copy. For this case we are able to conjecture an all-orders form of the double copy map.

Speaker: William Lindved (Edinburgh University)

William Lindved.pdf

15:40 → 16:20 Coffee + Biscuits

16:20 → 16:40 The Equivariant B Model

In this talk I will introduce an equivariant deformation of the B model on the sphere with a CY target. The theory is equivariant with respect to azimuthal rotations which have two fixed points, the north and south pole. Equivariance allows for novel observables with an explicit position-dependence on the sphere which have no analogue in the standard B model. For instance, while physical operators in the B model with superpotential are given by the chiral ring, in the equivariant case we can introduce generalised superpotentials such that the theory interpolates between models with different chiral rings. Using localisation we can compute observables like topological metrics and structure constants in the presence of such superpotentials. Finally, I will comment on ongoing work about an equivariant theory which resembles the B model on one pole and the \bar{B} model on the other. This theory does not require a CY target and, among other things, could be used to investigate topological anti-topological fusion.

Speaker: Roman Mauch (Uppsala University)

Nordic24_RomanMauch.pdf

16:40 → 17:00 The dynamics of first-order phase transitions in holographic theories

First-order phase transitions are somewhat neglected by theorists in favor of their second-order counterparts. Yet they contain rich physics, and are of importance in everything from condensed matter physics to (perhaps) early-universe cosmology. I will discuss the dynamics of first-order transitions at strong coupling, using holographic duality. First, I describe how to construct effective actions which can be used to compute all quasi-equilibrium parameters relevant for bubble nucleation. Second, I discuss computations of the terminal velocity of expanding bubbles. Lastly, I focus on the case where bubble nucleation is suppressed, allowing the system to reach the edge of metastability, the spinodal point. Spinodals harbor critical phenomena akin to those of second order transitions, including diverging relaxation times which disrupt adiabatic evolution. I explain how this is realized in a simple holographic setup.

Speaker: Oscar Henriksson (Åbo Akademi University)

Nordic Strings 2024 Nordita Henriksson.pdf

Nordic Strings 2024 Nordita Henriksson.pptx

17:00 → 17:20 Symmetries from Geometry

Many non-Lagrangian and strongly coupled quantum field theories (QFTs) can be realized via string constructions. These often serve as progenitor theories for large families of QFTs which in this setting admit constructions via deformation and compactification of the former. As standard, the dynamics of such QFTs are constrained by symmetries, and in this talk we discuss how to map a given string construction onto the symmetry data of the associated QFT. We focus on geometrically engineered QFTs (with dual brane constructions) and characterize their symmetries, and their anomalies, via a system of topological quantum field theories. The methods presented avoid the complicated dynamics of the QFT and we present their application to superconformal QFTs in 5D and 6D.

Speaker: Max Huebner (Uppsala University)

HuebnerSlot6Tuesday29th.pdf

17:20 → 17:25 Welcome by Nordita Director

Wednesday 30 October

10:00 → 11:00 Different perspectives on TTbar: a review

TTbar-deformed CFT's have been intensely studied as highly interesting, integrable theories, despite being obtained from an irrelevant deformation. In this review I will discuss TTbar theory from a perspective that allows to understand different proposed descriptions of the theory as different gauge choices. Finally, the holographic perspective will also be covered.

Speaker: Nele Callebaut (University of Cologne)

Note Oct 29, 2024.pdf

11:00 → 11:40 Coffee

11:40 → 12:00 Weak G2-manifolds and scale separation in M-theory from type IIA backgrounds

Whether flux compactifications can feature scale separation, i.e. whether the Kaluza-Klein length scale is much smaller than the cosmological scale, is still debated in the string community. In this talk, I will provide evidence for the existence of supersymmetric and scale-separated AdS4 vacua in M-theory of the Freund-Rubin type. The internal space has weak G2-holonomy, which is obtained from the lift of AdS vacua in massless type IIA on a specific SU(3)-structure with O6-planes. Such lifts require a local treatment of the O6-planes, therefore going beyond the usual smeared approximation. I will show how this can be achieved while preserving supersymmetry manifestly, extending on previous work.

Speaker: Vincent van Hemelryck (Uppsala University)

VanHemelryck.pdf

12:00 → 12:20 Strings near black holes are Carrollian

I will discuss strings probing the near-horizon region of a non-extremal black hole and show that this corresponds to understanding string theory in the Carroll regime. This is done by first performing a Carroll expansion and then a near-horizon expansion of a closed relativistic string, subsequently showing that they agree. There exist two different Carroll strings: a magnetic and an electric string. The magnetic string has a Lorentzian worldsheet, whereas the worldsheet of the electric string is Carrollian. The geometry near the horizon of a four-dimensional (4D) Schwarzschild black hole takes the form of a string Carroll expansion, and the solution space of relativistic strings near the horizon bifurcates and the two sectors precisely match with the magnetic/electric Carroll strings with an appropriate target space. Magnetic Carroll strings near a black hole shrink to a point on the two-sphere and either follow null geodesics or turn into folded strings on the 2D Rindler spacetime. Electric Carroll strings wrap the two-sphere and follow a massive geodesic in the Rindler space.

Speaker: Emil Have (NBI)

Presentation_Emil_Have.pdf

12:20 → 12:40 An eye for an $i$ will saturate the two-point functions

In the coarse-grained semiclassical limit, the two-sided two-point functions in the thermofield double state decay exponentially at late times. The decay is intimately tied to the existence of black holes in the dual bulk description and signals a loss of information. Necessitated by the chaotic behaviour of black holes, we refine the semiclassical limit by adding a universal non-perturbative correction to the CFT density of states. This correction stops the late-time decay of the correlation functions. Expanding the resulting late-time expression in a double-scaled limit, we obtain a series in powers of the boundary time and the black hole entropy. We then present a bulk calculation that reproduces this series. The origin of the non-perturbative correction can be traced to an infinite number of complex constrained instanton configurations. We will also discuss how our results fit perfectly with the principle of black hole complementarity.

Speaker: Vyshnav Mohan (University of Iceland)

Vyshnav_Mohan.pptx

Vyshnav_Mohan_Stockholm.pdf

12:40 → 13:00 Yangian symmetric conformal Feynman integrals and GKZ-systems

We demonstrate that Yangian symmetry property of fishnet Feynman integrals can be extended to the so-called Loom graphs. Further, we describe the general structure of the corresponding differential operators. In particular we show, that they are conjecturaly equivalent to the so-called Gelfand-Kapranov-Zelevisnky systems, which have already appeared in the context of Feynman integrals, but also in the study of mirror symmetry in string theory. Moreover, it appears that the equations themselves impose certain consistency conditions, which constrain the types of graph topologies that could support Yangian symmetry.

Speaker: Victor Mishnyakov (Nordita)

Mishnyakov_Slides_Nordic_Meeting.pdf

13:00 → 14:30 Lunch

14:30 → 14:50 Emergent Non-Invertible Symmetries -- The Adjoint QCD Example

After reviewing some general properties of the renormalization group (RG) flow for quantum field theories (QFT), I'll described how the recently descovered non-invertible symmetries can be used to put constraints on the dynamics of strongly coupled QFTs. I'll illustrate these facts using (3+1)-dimensional Adjoint QCD with two flavors as an example. This theory can be obtained by mass deforming a pure N=2 super Yang-Mills theory. Relaying on supersymmetric results, dynamical abelianization and monopole condensation, we are able to get to the description of an infrared (IR) phase characterized by an CP1 sigma model. In this scenario, the IR phase has an emergent non-invertible symmetry, which is matched with the non-invertible symmetry of the IR CP1 phase. This result illustrate how an emergent non-invertible symmetry can be used to provide a bridge connecting the IR and its properties with the ones of microscopic degrees of freedom in gauge theories with one-form symmetries.

Speaker: Shani Nadir Meynet (Uppsala University)

SMeynet_talk.pdf

14:50 → 15:10 Elliptic Integrable Models and Their Spectra from Superconformal Indices

In my talk I will review our recent progress in understanding the intricate relationship between elliptic finite-difference integrable models and 4D superconformal indices. Although this connection has been known for some time, we have recently achieved significant advancements in this area. I will begin by briefly reviewing how these models arise in superconformal index computations, particularly when surface defects are introduced into 4D gauge theory. I will then discuss several such models that we have recently derived using these constructions. Finally, I will present our novel, physics-inspired approach to deriving the spectra of elliptic integrable models that have not been previously known. I will also touch upon the relation of our construction to 5D ramified instanton partition functions.

Speaker: Anton Nedelin (Uppsala Univerity)

nedelin_nordic_meeting.pdf

15:10 → 15:30 3d SCFTs and Precision Holography

In this talk we will investigate the behaviour of the vacuum expectation value (vev) of the Wilson loop of a class of 3-dimensional $\mathcal{N}=2$ SCFTs beyond the large 't Hooft coupling limit. This will be achieved through the means of holography, by studying its holographic counterpart, namely the partition function of a fundamental string, beyond leading order. In turn, this will lead us to a prediction for the sub-leading behaviour of the Wilson loop vev, from holography.

Speaker: Alexia Nix (University of Iceland)

15:30 → 15:50 Regge spectroscopy of higher twist states in N=4 supersymmetric Yang-Mills theory

We study a family of higher-twist Regge trajectories in N=4 supersymmetric Yang-Mills theory using the Quantum Spectral Curve. We explore the many-sheeted Riemann surface and show the interplay between the higher-twist trajectories and the several degenerate non-local operators, called (near-)horizontal trajectories, that have a strong connection to light ray operators, objects omnipresent in 4-dimensional Minkowskian CFTs. We resolve the encountered degeneracy analytically by computing the first non-trivial order of the Regge intercept at weak coupling, which exhibits new behaviour: it depends linearly on the coupling. This is consistent with our numerics, which interpolate all the way to strong coupling.

Speaker: István Máté Szécsényi (Stockholm University)

2024_10_30_Nordic_Strings_Stockholm_Istvan_M_Szecsenyi.pdf

15:50 → 16:30 Coffee

16:30 → 16:50 5d conformal matter theories across dimensions

The exploration of the landscape of 5d superconformal field theories (5d SCFTs) has undergone steadfast progress in the last few years, thanks to the multi-faceted toolbox provided by string theory and its cousins. Recently, a novel class of 5d SCFTs dubbed "5d conformal matter theories" have been discovered via M-theory geometric engineering: these behave as generalized bifundamental matter theories with non-trivial interacting dynamics, and can be neatly classified in terms of irreducible building blocks. Conformally gauging such blocks produces infinite families of more complicated 5d SCFTs, amenable to a low-energy gauge theory analysis and displaying interesting UV dualities. We present upcoming work that deepens the understanding of 5d conformal matter theories and clarifies their status in the arena of SCFTs in various dimensions: we show that their compactification on a circle yields 4d N=2 class S theories, we produce their interpretation in terms of brane-web constructions, and we exhibit their 3d N=4 magnetic quiver duals. All these pieces of the puzzle are intimately related and finally come together to form a coherent characterization of the Higgs branch of 5d conformal matter theories.

Speaker: Andrea Sangiovanni (Uppsala University)

Andrea_Sangiovanni_Nordita.pdf

16:50 → 17:10 Higgs Branch RG-flows - Decay and Fission of Magnetic Quivers

Supersymmetric theories with 8 supercharges in dimensions 3 through 6 have a large moduli space of vacua, and the Higgs branches are one of the most significant parts of this space. These (singular) hyper-Kahler spaces can be characterised by a combinatorial object known as the magnetic quiver. By using this technique, we can fully encode the Higgs branch geometry for both the low energy effective description and the strongly coupled conformal fixed point. Here, I present the decay and fission algorithm for unitary magnetic quivers. It efficiently derives complete phase diagrams (Hasse diagrams) through convex linear algebra. It allows magnetic quivers to undergo decay or fission, reflecting Higgs branch RG-flows in the theory. In this talk, I will discuss this construction in the context of 5d and 6d theories. Based on arXiv:2312.05304 and 2401.08757 with A. Bourget and Z. Zhong.

Speaker: Marcus Sperling (University of Vienna)

Talk_Sperling.pdf

17:10 → 17:30 Matrix theory reloaded: a BPS road to holography

Building on a recently developed web of decoupled theories related by U-duality, a new view point on matrix theories is presented, which includes connections with non-Lorentzian geometries. This will lead to a novel perspective on holography and point the way to interesting generalizations.

Speaker: Niels Obers (Niels Bohr Institute)

BPSholo_Nordita_2024_obers.pdf

17:30 → 18:00 Career Talk

Speaker: Marjorie Schillo

NorditaCareerTalk2024.pdf

18:30 → 20:00 Dinner

Thursday 31 October

10:00 → 11:00 3d N=2 Dualities From Linked M2 branes

In this talk I will review recent progress on supersymmetry-protected interactions among M2 branes with boundaries on M5 branes, and related implications for dualities of 3d N=2 QFTs. We consider M theory in the background of the resolved conifold, with M5 branes wrapping a Lagrangian submanifold L. For a large class of Lagrangians, known as knot conormals, we establish a Lagrangian description of the 3d-3d dual QFT, and show that the spectrum of BPS vortices is described by a quiver, whose structure encodes the linking of finitely many M2 branes with boundaries on L. A duality web of 3d N=2 QFTs is shown to arise by modifying the linking structure of the basic M2 branes. Based on works with Kucharski, Ekholm, Nakamura, and Gupta.

Speaker: Pietro Longhi (Uppsala University)

11:00 → 11:30 Coffee

11:30 → 11:50 TTbar in d dimensions from Massive Gravity

In this talk, I will present a systematic approach to stress-tensor deformations in d dimensions, using the massive gravity formulation. In two dimensions, the resulting deforming operator is of quadratic order and correctly reduces to TTbar or TTbar+Λ_2 at certain limits. Moreover, the quantum mechanical spectrum of this generalized operator exhibits interesting behaviour. In d>2, higher order terms also appear, but the quadratic part of the deformation precisely matches with prior findings. Under certain assumptions, all but the quadratic terms vanish identically.

Speaker: Evangelos Tsolakidis (University of Iceland)

11:50 → 12:10 The dilaton double copy

We study the direct double copy to massive amplitudes with propagating dilaton states, motivated by finding a prescription to directly double copy to Einsten-Hilbert gravity amplitudes

Speaker: Ingrid Vazquez-Holm (Uppsala University and Nordita)

ingridvazquezholm.pdf

12:10 → 12:30 Gravitational solitons and non-relativistic string theory

Starting with a 4D CFT we consider two null-reductions, one being of the CFT on a three-sphere, the other being a recent construction of Lambert et al. After the null-reduction they live on two different torsional Newton-Cartan geometries. However, they share the same exotic conformal group SU(1,2). We show that the reason behind this is that they are two sides of a novel state-operator correspondence, realized both geometrically and algebraically.

Speaker: Troels Harmark

2024 Nordic strings Nordita.pdf

12:30 → 13:00 Career Talk

Speaker: David Marsh (Stockholm University)

13:00 → 14:30 Lunch