International Conference on String Field Theory and String Perturbation Theory

6 May 2019, 08:40 → 10 May 2019, 18:00 Europe/Rome

A (Arcetri, Firenze)

Carlo Maccaferri

This is the X edition of the annual conference on String Field Theory and related aspects.

Previous editions were held in India (2018), Brazil (2016),  China (2015), Italy (2014), Israel (2012), Czechia (2011), Japan (2010), Russia (2009), Germany (2008).

The related aspect of this year will be String Perturbation Theory.

 

The conference is the concluding event of the long-term workshop at the GGI Institute on "String Theory from a world-sheet perspective" which also includes an initial training week of Review Lectures on World-Sheet Aspects of String Theory.

 

REGISTRATION

Monday 6 May

Registration and Opening

Talks

1 A worldline approach to theories with infinite many fields in flat spacetime

The talk tries to address the question: how to construct a local field
theory with infinite many fields. First the effective action method is
presented. It is shown how it naturally leads to the definition of
(generally non-local) field theories. It has however strong technical
limitations. Then the more powerful and systematic worldline approach is
introduced, which carries the L-infinity symmetry and relevant Ward
indentities. The latter can be integrated, leading to a set of new
theories: YM-like theories in any dimension and CS-like theories in any
odd dimension. The structure the YM-like theories, in particular the
absence of propagating ghosts, is discussed. Finally a possible
connection with string theory is suggested.

Speaker: Loriano Bonora (TS)

video

2 Winding number with arbitrary integer value in Cubic String Field Theory

We examined in the previous paper whether winding number could be defined
in CSFT. We have found that the quantity N=\int (UQU^-1)^3 has many desirable properties as topological quantity. However, N could not realize an arbitrary integer
value, since it is not possible to suppress the anomaly.
This time, by generalizing the KBc-type solution, we were able to obtain N with arbitorary integer value while maintaining the topological properties.
These classical solutions are different from related study arXiv:1901.01681 [hep-th]
in that it holds equivalence of K=0 and K=infinity, where K is a kind of Hamiltonian of
world sheet, and the solution is constructed by finite term.

Speaker: Toshiko Kojita

Video

11:30 Coffee Break

Talks

3 Classical solutions in string field theory: a review

We review some of the older as well as more recent progress in attempts to construct and study classical solutions in string field theory.

Speaker: Martin Schnabl

GGI_2019.pdf

Video

13:00 Lunch Break

Talks

4 Unconventional D-branes on T^4

We show that apart from the conventional Dp-branes and their supersymmetric bound states, the weakly coupled type II superstring compactified on a 4-torus admits new stable non-BPS fundamental D-branes. We construct the corresponding elementary superconformal boundary states at special values of closed string moduli for which the worldsheet theory admits a Gepner-like description and check a number of BCFT consistency conditions. The open string spectrum of these new non-BPS D-branes is tachyon free despite the fact that they carry no RR charges. New explicit superconformal boundary states for certain 1/4-BPS bound states of Dp-branes are also found.

Speaker: Jakub Vosmera

ggi2019.pdf

Video

5 Closed string amplitudes from single-valued correlation functions

Closed string theory amplitudes display the remarkable property of presenting only single-valued multiple zeta in its low-energy expansion. At genus zero we show how this emerges by identifying the building blocks of any closed string amplitudes with the value at z=1 of single-valued correlation functions in two dimensional conformal field theory. We use the single-valuedness condition to determine uniquely the correlation function and determine the role of the momentum kernel in the singlevalued projection. We will present a similar construction at genus one and explain the appearance of a new class of modular functions so-called modular graph functions.

Speaker: Pierre Vanhove

svMZV-GGI-mai-2019.pdf

Video

16:00 Coffee Break

Talks

6 Manifest T-Duality from a World-Sheet Perspective

After discussing some proposals for a string world-sheet manifestly invariant under the $O(D,D)$ Abelian T-duality, the more general notion of Poisson-Lie T-duality will be introduced together with the one of Drinfeld double that constitutes the algebraic structure necessary to the existence of such duality. As illustrating examples, the three-dimensional Isotropic Rigid Rotor and the Principal Chiral Model will be investigated, aiming at understanding how such duality explicitly works. Both the models are described by sigma models having the group manifold of SU(2) as target space and their respective duals are introduced having the Poisson-Lie dual of SU(2) as configuration space. A “double” generalized action, i.e. a sigma model having SL(2,C), i.e. the Drinfeld double of SU(2), as target space is then defined containing twice as many variables as the original. It reduces to the original action or to its dual, once constraints are suitably implemented. Furthermore, the geometric structures of these double actions can be understood in terms of Generalized Geometry.

Speaker: Franco Pezzella

FirenzeGGI2019.pdf

Video

Reception

Tuesday 7 May

Talks

7 High Energy Scattering in AdS/CFT

Speaker: Hirosi Ooguri

Video

8 Uniqueness of Closed-Superstring Field Theory Interaction Vertices

Speaker: Faroogh Moosavian

Video

11:30 Coffee Break

Talks

9 The structure of higher genus Gromov-Witten theory of quintic 3-folds

One of biggest and most difficult problems in the subject of Gromov-Witten
theory is to compute higher genus Gromov-Witten theory of compact Calabi-Yau 3-fold.
There have been a collection of remarkable conjecture from physics for so called 14 one-parameter models,
simplest compact Calabi-Yau 3-folds similar to the quintic 3-folds. These conjectures were
originated from universal properties of BCOV B-model. The backbone of
this collection are four structural conjectures: (1) Yamaguchi-Yau finite generation;
(2) Holomorphic anomaly equation; (3) Orbifold regularity and (4) Conifold gap condition. In
the talk, I will present background and our approach to the problem.
This is a joint work with F. Janda and S. Guo. Our proof is based on certain localization formula from
log GLSM theory developed by Q. Chen, F. Janda and myself.

Speaker: Yongbin Ruan

Video

13:00 Lunch Break

Talks

10 Generic properties of OSFT solutions in level truncation

Speaker: Matej Kudrna

Video

11 Rolling Near the Tachyon Vacuum

Speaker: Theodore Erler

GGItalk.pdf

Video

16:00 Coffee Break

Talks

12 Emergent Geometries from String Field Theory: Supergeometry and Non-associative algebras

Inspired by the analogy between different types of differential forms
on supermanifolds and string fields in superstring theory,
I describe new multilinear non-associative products of forms
which yield an A-infinity algebra for any supermanifold.

Speaker: Pietro Antonio Grassi

Video

Wednesday 8 May

Talks

13 Nonperturbative definition of closed string theory via open string field theory

In open bosonic string field theory with the cubic interaction in terms of the star product a gauge-invariant operator can be defined for each on-shell closed string state. In the theory on N coincident D-branes we claim that the evaluation of correlation functions of the gauge-invariant operators in the 1/N expansion can be interpreted as a closed string perturbation theory in a low-energy limit. Therefore, open string field theory can provide a nonperturbative definition of closed string theory if it is a consistent quantum theory for finite N, which motivates us to explore the generalization to open superstring field theory.

Speaker: Yuji Okawa

SFT2019-Okawa.pdf

Video

14 The underlying gauge theory of the pure spinor superstring

Previous attempts to determine the worldsheet origin of the pure spinor formalism were not completely successful, but introduced important concepts that seem to be connected to its fundamental structure. I will present here a new proposal for the underlying gauge theory of the pure spinor superstring, based on an extension of Berkovits' twistor-like constraint. I will start with a quick review of previous approaches and then proceed to the BRST quantization of the new model. I will show that, after a field redefinition, spacetime supersymmetry emerges and the resulting action describes the pure spinor superstring.

Speaker: Rennan Lipinski Jusinskas

Video

11:30 Coffee Break

Talks

15 Open, closed and heterotic strings at one loop: Elliptic multiple zeta values versus modular graph forms

This talk is dedicated to one-loop amplitudes in open, closed and heterotic string theories
and aims to illustrate connections between their low-energy expansions. For open strings,
the coefficients in the one-loop alpha’-expansion are elliptic multiple zeta values which arise
from moduli-space integrals over punctured cylinders. Closed and heterotic strings in turn
introduce moduli-space integrals over punctured tori which evaluate to so-called modular
graph forms. These modular forms are observed to exhibit striking parallels to the elliptic
multiple zeta values in open-string expansions which should generalize the single-valued
projection of multiple zeta values known from genus zero.

Speaker: Oliver Schlotterer

eMZV and modular graph forms.pdf

Video

13:00 Lunch Break

Talks

16 Scattering Amplitudes from Intersection Theory

It has long been known that intersection theory on the moduli space of punctured Riemann surfaces computes all observables in the two-dimensional quantum gravity. It is natural to ask whether interacting theories could also admit a similar description. In the genus-zero case we construct a twisted version of intersection theory on the moduli space and propose that it gives rise to tree-level scattering amplitudes in a range of quantum field theories. We present recursion relations for intersection numbers on the natural fibration of moduli spaces.

Speaker: Sebastian Mizera

Video

17 Strings on Celestial Sphere

Speaker: Tomasz Taylor

Taylor_GGI.pdf

16:00 Coffee Break

Talks

18 Making (excited) spin fields and twist fields pointlike defects on the worldsheet

Speaker: Igor Pesando

Video

Thursday 9 May

Talks

19 String field theory and self-dual forms

Speaker: Ashoke Sen

ggisft.pdf

Video

20 Light-cone reduction of covariant string field theory

We extract a light-cone string field theory from Witten’s covariant string field theory.
The covariant string field splits into the light-cone string field and trivial excitations of BRST quartets:
The latter generates the gauge symmetry and covariance.
A new light-cone theory, which has an A-infinity type action, is obtained by path-integrating it out from the Witten theory.
We show that the process of path-integrating-out fields is described by the homological perturbation lemma (for A-infinity) and thus our A-infinity light-cone string field theory has the same tree-level amplitudes as the Witten theory.
[arXiv:1901.08555]

Speaker: Hiroaki Matsunaga

H.Matsunaga_SFT2019.pdf

Video

11:30 Coffee Break

Talks

21 Towards the Construction of New Democratic Theories

Speaker: Michael Kroyter

FirenzeDemocraticNew.pdf

Video

13:00 Lunch Break

Talks

22 Deriving on-shell open string field amplitudes without using the Feynman rule

We present a series of new gauge invariant quantities in Witten's open string field theory. They are defined against a set of open-string states which satisfy the physical state condition around a classical solution. We discuss that, for known classical solutions, these gauge invariant quantities compute the on-shell tree-level scattering amplitudes on a D-brane configuration represented by the classical solution. (Based on collaborative work with H. Matsunaga)

Speaker: Toru Masuda

presentation_SFT2019.pdf

Video

23 Closed string symmetries in open string field theory: tachyon vacuum as sine-square deformation

We revisit the identity-based solutions for tachyon condensation in
open bosonic string field theory (SFT) from the viewpoint of the
sine-square deformation (SSD). We show that the open string system with
SSD exhibits decoupling of the left and right moving modes and so it
behaves like a system with a periodic boundary condition. With a method
developed by Ishibashi and Tada, we construct pairs of Virasoro
generators in this system, which represent symmetries for a closed
string system. Moreover, we find that the modified BRST operator in the
open SFT at the identity-based tachyon vacuum decomposes to holomorphic
and antiholomorphic parts, and these reflect closed string symmetries in
the open SFT. On the basis of SSD and these decomposed operators, we
construct holomorphic and antiholomorphic continuous Virasoro algebras
at the tachyon vacuum. These results imply that it is possible to
formulate a pure closed string theory in terms of the open SFT at the
identity-based tachyon vacuum

Speaker: Tomohiko Takahashi

SSD_talk_sft19.pdf

Video

16:00 Coffee Break

Talks

24 On Finite Size D-branes

I will discuss the marginal deformation describing the blow-up of a zero-size D-brane within super string field theory as well as the world sheet description. By analyzing the equations of motion of superstring field theory we find that this marginal deformation is obstructed, at third order in the size of the D- brane. This obstruction is due to subtleties in the integration over odd moduli in super-moduli space, which are missed by the standard worldsheet approach in terms of vertex operators of various pictures.

Speaker: Ivo Sachs

Video

Reception: Social Dinner

Friday 10 May

Talks

25 Heterotic string field theory with cyclic L-infinity structure

We construct a complete heterotic string field theory that includes
both the Neveu-Schwarz and Ramond sectors. We give a construction
of general string products, which realizes a cyclic L-infinity structures
and thus provides with a gauge invariant action in the homotopy
algebraic formulation. Through a map of the string fields, we also
give the Wess-Zumino-Witten-like action in the large Hilbert space,
and verify its gauge invariance independently.

Speaker: Hiroshi Kunitomo

GGI_201905.pdf

Video

26 Crossing symmetry in superstring theory

We prove crossing symmetry of superstring amplitudes to all orders in
perturbation theory. This is achieved by showing that the Green
functions are analytic in a specific region of the complex momentum
space ("primitive domain") and making use of results from Bros, Epstein
and Glaser. The original derivation relies on locality and causality of
the underlying QFT in position space: since this representation is not
available in string theory due to the non-locality of the interactions,
analyticity is obtained directly in momentum space. By reversing the
argument, this teaches important facts on the nature of the QFT
describing string theory.

Speaker: Harold Erbin

ggi_crossing_symmetry_sft.pdf

Video

11:30 Coffee Break

Talks

27 Gluing string amplitudes with coherent states

Speaker: Dimitri Skliros

Video

28 Final Discussion

13:00 Lunch and Salutations