This year we will continue our online series of seminars, given last year’s success.
Ordinarily, seminars will take place on Tuesdays at 4PMItalian time (CEST/CET). [NB: the time was changed from 2:30PM to 4PM.]
All seminars will take place on Zoom; you can join the room via the link https://l.infn.it/stringwebseminar. (Meeting ID: 876 4300 0411 – Please use your NAME+LAST NAME when logging in to be allowed in the room.)
All seminars are recorded for your convenience: the recording will be linked below the corresponding seminar post on this website.
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Title: Adiabatic continuity, mixed anomalies and semi-classical description of confinement
I describe an anomaly-preserving compactification of four dimensional gauge theories, including Yang-Mills theory, its supersymmetric version and QCD, down to 2d by turning on ‘t Hooft flux through a 2-torus. This provides a new framework to analytically calculate nonperturbative properties such as confinement, chiral symmetry breaking, and multi-branch structure of vacua. We give the semiclassical description of these phenomena based on the center vortices, and show that it enjoys the same anomaly matching condition with the original 4d gauge theory. For YM, the long distance theory maps to TQFT deformed by local topological operators. We conjecture that the weak-coupling vacuum structure on small T2 x R2 is adiabatically connected to the strong-coupling regime in infinite volume without any phase transitions.
Title: Line defects in CFTs: renormalization group flows and semiclassical limits
I will discuss line defects in d-dimensional Conformal Field Theories (CFTs). I will first review recent general results on the monotonicity of defect RG flows for line defects. I will then discuss three physically interesting examples of line defects: magnetic field defects, spin impurities, and Wilson lines. In particular, I will present a recently developed semiclassical approach, which allows studying spin impurities and Wilson lines in large representations.
Title: SUSY breaking in branes at singularities (or: The octagon rising from the swamp)
After motivating the search for string theory configurations where supersymmetry is spontaneously broken, I will discuss the approach focused on branes at singularities, in the context of the open/closed duality (a.k.a. gauge/gravity correspondence). The search for SUSY breaking configurations is made difficult by the peculiarities of the QFT models of dynamical SUSY breaking models one wants to reproduce with branes, and by the instabilities inherent with the brane construction. I will finally present a configuration, based on a particular singularity (which we dubbed the Octagon), that is the only one to pass all the stability tests. We comment on its properties and possible generalizations, and geometric/supergravity realizations. We will make some comments on the relevance of our results for some Swampland conjectures. Based on 1909.04682, 2005.09671, 2007.13762, 2009.11291 + work in progress.
Title: Integrating out in string field theory: effective actions and background independence
Abstract: I review recent results on the procedure of integrating out unwanted degrees of freedom from a fundamental microscopic string field theory action. A first application is the construction of effective actions/potentials for the strings’ light fields by integrating out massive string fields. I will give a few examples of D-branes effective potentials obtained in this way. A second, physically different, application concerns analytic classical solutions of open string field theory (OSFT) describing generic D-brane systems in a given closed string background. This time, by integrating out peculiar “pure gauge” degrees of freedom, we can precisely relate the action for fluctuations on the classical solution to the OSFT directly formulated on the new background thus explicitly realizing (open string) background independence. I end up discussing possible new directions for future explorations.
UPDATE (Dec 9): The timetable and scientific program of both events (Dec 13 & Dec 16) have been published here below. (All times are CET.) All recordings and presentations will be uploaded during the days following the events.
UPDATE (Dec 5): There will be 2 Young Days, on Dec 13 & Dec 16, 2021. The Dec 13 event will be fully online (zoom talks only), whereas the Dec 16 one will be in hybrid mode (zoom talks in the morning, in-person talks also streamed on zoom in the afternoon). All seminars will be recorded and posted online for your convenience.
The timetable and scientific program will be posted soon.
Those who wish to attend the Dec 16 event in person should follow the same rules as on Nov 16 (see here below). There will be a (complimentary) social dinner on the night of Dec 16: please send us an email ASAP if wish to attend it.
UPDATE (Dec 1): The applications to give a 20′ seminar are closed.
Rules for attending the in-person meeting at the University of Milan-Bicocca (Sironi hall, building U4, floor -1):
1) Those who wish to attend the meeting in person (many spots available) should contact the organizers and fill in the (Google) form available at the link https://forms.gle/GM86PqSFLTtFLwss7 the day of their arrival in Milan, or the day before (the in-person speakers should also fill in the same form).
2) The attendees should also fill in, print, sign, and bring with them the Covid form (covid_form.pdf) available at that same link. (All attendees will be required to show a valid EU digital covid pass / Italian green pass at the entrance of the building, and will be required to wear a face mask during the entire duration of the event, and on all university’s premises.)
Natalia Pinzani-Fokeeva (MIT & University of Florence)
Title: Enstrophy and black hole supertranslations
Abstract: Enstrophy is an approximately conserved quantity in 2+1 dimensional fluid flows that has dramatic consequences for the phenomenology of nonrelativistic turbulence: it implies an inverse energy cascade. In this talk, I will present an algorithm on how to construct an enstrophy current for generic fluid flows (relativistic and non). In addition, I will show how a subset of certain horizon symmetries of 3+1 dimensional AdS black holes also lead to enstrophy conservation in the dual holographic fluid theory.
UPDATE (Nov 17): all recordings and presentations of the Nov 16 event are available at the links below.
On November 16 and December 13 [UPDATE (Nov 10): was December 14], 2021 we will hold the first INFN Strings “Young Days”: on each day there will be two/three 20′ seminars by young researchers (PhD students or postdocs), starting at 4PM Italian time.
UPDATE (Nov 2): The applications for the November 16 event are now closed. (You can still apply for the December 14 one.) The selected speakers will be contacted soon.
UPDATE (Nov 9): Given the quality of the applicants, the diversity of the topics, the number of applications received, we will host more seminars than originally planned. Each day will be divided into two sessions (a morning and an afternoon one), featuring both in-person and remote seminars. All seminars will be recorded.
The in-person seminars will be held at the University of Milan-Bicocca and live-streamed on Zoom; the remote seminars will be held in the usual Zoom room https://infn-it.zoom.us/j/87643000411.
Those who wish to attend the meeting in person (many spots still available) should contact the organizers and fill in the (Google) form available at the link https://forms.gle/GM86PqSFLTtFLwss7 the day of their arrival in Milan, or the day before (the in-person speakers should also fill in the same form). NB: the attendees should also fill in, print, sign, and bring with them the Covid form (covid_form.pdf) available at that same link.
The meeting will be held in the Sironi hall (https://www.unimib.it/node/13763) inside building U4 (https://goo.gl/maps/TcLBtxoZkr31P1Pk6), floor -1: as you enter the building, take the flight of stairs immediately to your left, go down one floor, then go right and left around the corner. The room number is U4-8. (Do not hesitate to contact us in case you have problems finding the room.) NB: all attendees will be required to show their EU digital covid pass / Italian green pass at the entrance of the building, and will be required to wear a face mask during the entire duration of the event, and on all university’s premises.
Abstract: I will discuss the fundamentals of quantum field theory on a rigid de Sitter space. First, I will show that the perturbative expansion of late-time correlation functions to all orders can be equivalently generated by a non-unitary Lagrangian on a Euclidean AdS geometry. This finding simplifies dramatically perturbative computations, as well as allows us to establish basic properties of these correlators, which comprise a Euclidean CFT. Second, I use this to infer the analytic structure of the spectral density that captures the conformal partial wave expansion of a late-time four-point function, to derive an OPE expansion, and to constrain the operator spectrum. Third, I will prove that unitarity of the de Sitter theory manifests itself as the positivity of the spectral density. This statement does not rely on the use of Euclidean AdS Lagrangians and holds non-perturbatively.
Abstract: We prove dualities involving four dimensional N=1 gauge theories with rank-2 matter. We assume only elementary dualities, that is Seiberg and Intriligator-Pouliot dualities. The strategy is to use multiple times elementary S-confining dualities and elementary electric-magnetic dualities, until the desired dual theory is reached. As a first example, we derive the Wess-Zumino description of all S-confining single node quivers with rank-2 matter. As a second example, we derive a ‘fully deconfined’ dual of USp(2N) with an antisymmetric and 2F fundamental fields, then use it to prove a self-duality valid at F=4. These results are based on ongoing work with Stéphane Bajeot, and uplift 3d results obtained with Ivan Garozzo and Gabriele Lo Monaco.
Title: Conformal boundary conditions for free fields
Abstract: I will discuss the problem of classifying (interacting) conformal boundary conditions for the simplest bulk conformal field theories: free fields. I will mention concrete examples based on perturbation theory, and then describe results using the numerical conformal bootstrap approach, specifically in the case of a scalar field in four and three bulk dimensions.