BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Gustavo Joaquin Turiaci (UCSB) DTSTART:20200921T183000Z DTEND:20200921T193000Z DTSTAMP:20260404T111416Z UID:PUHET/1 DESCRIPTION:Title: The gravitational path integral near extremality\nby Gustavo Joaq uin Turiaci (UCSB) as part of Princeton HET seminar\n\n\nAbstract\nI will explain the relation between the Euclidean path integral over near-extrema l black hole geometries and its dimensional reduction to 2D Jackiw-Teitelb oim gravity. I will focus mostly on the case of 3D gravity and a particula r application to pure 3D gravity. I will also mention a connection between more general 2D dilaton-gravity theories\, matrix integrals and the minim al string.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Oscar Varela (USU) DTSTART:20200925T174500Z DTEND:20200925T184500Z DTSTAMP:20260404T111416Z UID:PUHET/2 DESCRIPTION:Title: AdS4/CFT3 Squashed\, Stretched\, Warped and Invaded\nby Oscar Var ela (USU) as part of Princeton HET seminar\n\n\nAbstract\nThe spectrum of single-trace operators of holographic CFTs at strong coupling and large N can be mapped to the spectrum of Kaluza-Klein modes over the dual AdS supe rgravity solutions. In this talk\, I will focus on two specific CFT3s with AdS4xS7 gravity duals that arise as infrared fixed points of the ABJM M2- brane field theory deformed with a certain quadratic and a certain cubic s uperpotential. In both cases\, the AdS4xS7 product is warped and the metri c on S7 is squashed and stretched. In the quadratic case\, I will show how Exceptional Field Theory techniques can be used to compute the entire spe ctrum. In the cubic case\, I will show that the spectrum exhibits a space- invaders scenario\, similar to that known to occur for another squashed Ad S4xS7 solution.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Tarek Anous (University of Amsterdam) DTSTART:20201009T174500Z DTEND:20201009T184500Z DTSTAMP:20260404T111416Z UID:PUHET/3 DESCRIPTION:Title: Towards a microscopic model of AdS fragmentation\nby Tarek Anous (University of Amsterdam) as part of Princeton HET seminar\n\n\nAbstract\n A salient feature of black holes near extremality is the appearance of an AdS$_2$ throat in their near-horizon geometry. Depending on the underlying theory\, these AdS$_2$ throats may be unstable to fragmentation\, wherei n a single throat is instead replaced by a tree-like structure of branched AdS$_2$ throats. For Einstein-Maxwell theory\, the underlying reason behi nd this instability is the existence of multi-centered configuration in th e moduli space of black hole solutions at fixed total charge. Given the su ccess of the Schwarzian/SYK paradigm for understanding a single AdS$_2$ it is time to revisit the fragmentation story. To build up intuition\, I wil l present a model\, studied in the statistical mechanics literature\, that shares many features with SYK\, including exact solvability at large-N an d an emergent conformal symmetry that gets weakly broken in the UV. The no vel feature of this model is the appearance of a spin glass phase at O(1) temperatures\, which I will try to relate to the fragmentation story.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Amirhossein Tajdini (UCSB) DTSTART:20201019T183000Z DTEND:20201019T193000Z DTSTAMP:20260404T111416Z UID:PUHET/4 DESCRIPTION:Title: The fast conformal bootstrap and sphere packing in high dimensions\nby Amirhossein Tajdini (UCSB) as part of Princeton HET seminar\n\n\nAbs tract\nThe conformal bootstrap program seeks to map the space of possible conformal field theories and to identify those on the boundary of theory s pace. In this talk\, I will discuss a numerical method that is applicable to certain bootstrap problems\, such as the spinless modular bootstrap in two dimensions. This method extends the conformal bootstrap to the regime of large central charge which is relevant to three-dimensional gravity. Th e same method applies to the sphere packing problem and gives new bounds o n the packing density in high dimensions. I will talk about these new boun ds and give a summary of existing bounds. I will also talk about bootstrap ping four-point functions on a plane by using the fast bootstrap method.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Shai Chester (Weizmann) DTSTART:20201023T174500Z DTEND:20201023T184500Z DTSTAMP:20260404T111416Z UID:PUHET/5 DESCRIPTION:Title: Derivation of AdS/CFT for Vector Models\nby Shai Chester (Weizman n) as part of Princeton HET seminar\n\n\nAbstract\nWe derive an explicit m ap between the singlet sector of the free and critical O(N) and U(N) vecto r models in any spacetime dimension above two and to all orders in 1/N\, a nd a bulk higher spin theory in anti-de Sitter space in one higher dimensi on. For the boundary theory\, we use the bilocal formalism of Jevicki et a l to restrict to the singlet sector of the vector model. The bulk theory i s defined from the boundary theory via our mapping\, and is a consistent q uantum higher spin theory with a well defined action. Our mapping relates bilocal operators in the boundary theory to higher spin fields in the bulk \, while single trace local operators in the boundary theory are related t o boundary values of higher spin fields.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Dumitrescu (UCLA) DTSTART:20201102T193000Z DTEND:20201102T203000Z DTSTAMP:20260404T111416Z UID:PUHET/6 DESCRIPTION:Title: 2-Group Symmetries in Six Dimensions\nby Thomas Dumitrescu (UCLA) as part of Princeton HET seminar\n\n\nAbstract\nI will review the notion of (continuous) 2-group global symmetries\, which mix ordinary and higher- form global symmetries\, and explain why they naturally arise in many 6d g auge theories. Most 6d SCFTs and little string theories have weakly-couple d infrared phases with gauge fields. While non-trivial 2-group symmetries are often present in little string theories\, I will explain why they can never arise in unitary SCFTs. This observation can be used to establish a previously conjectured algorithm for computing ’t Hooft anomalies of suc h SCFTs. Finally\, I will use this understanding to shed light on the a-th eorem in six dimensions. In particular I will show that all unitary 6d SCF Ts have positive a-anomaly.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Mykola Dedushenko (SCGP) DTSTART:20201106T184500Z DTEND:20201106T194500Z DTSTAMP:20260404T111416Z UID:PUHET/7 DESCRIPTION:Title: Yangians and other algebras you can find at boundaries and interfaces \nby Mykola Dedushenko (SCGP) as part of Princeton HET seminar\n\n\nAb stract\nI will discuss protected sectors in the 4d N=4 SYM with the half-B PS boundary or interface. Algebraic structures of various levels of comple xity appear in this context\, such as U(g) (universal enveloping algebra)\ , W(g\,e) (fintie W-algebra)\, their quantum Hamiltonian reductions\, and the Yangian (or rather its truncation). One can use the power of algebra\, as well as integrability in the latter case\, to solve for correlation fu nctions. In particular\, for an interface engineered by a pair of fivebran es\, one can leverage connection to the inhomogeneous XXX spin chain to co mpute correlators quite explicitly.\nBased on 2009.11197 and 2009.11198 .\n LOCATION:https://stable.researchseminars.org/talk/PUHET/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexey Milekhin (Princeton) DTSTART:20201116T193000Z DTEND:20201116T203000Z DTSTAMP:20260404T111416Z UID:PUHET/8 DESCRIPTION:Title: Quantum error correction and large N\nby Alexey Milekhin (Princet on) as part of Princeton HET seminar\n\n\nAbstract\nIn recent years quantu m error correction (QEC) has become an important part of AdS/CFT. Unfortun ately\, there are no field-theoretic arguments about why QEC holds in know n holographic systems. The purpose of this talk is to fill this gap by stu dying the error correcting properties of the fermionic sector of various l arge N theories. Specifically we examine SU(N) matrix quantum mechanics an d 3-rank tensor O(N)^3 theories. Both of these theories contain large gaug e groups. We argue that gauge singlet states indeed form a quantum error c orrecting code. Our considerations are based purely on large N analysis an d do not appeal to a particular form of Hamiltonian or holography.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexander Zhiboedov (CERN) DTSTART:20201204T184500Z DTEND:20201204T194500Z DTSTAMP:20260404T111416Z UID:PUHET/10 DESCRIPTION:Title: Solving unitarity with contraction mappings\nby Alexander Zhiboe dov (CERN) as part of Princeton HET seminar\n\n\nAbstract\nI will discuss the problem of constructing relativistic\, unitary and crossing-symmetric\ nscattering amplitudes in higher-dimensional gapped theories. I will revie w the implications of \nelastic unitarity and crossing\, as well as the ob servation that the resulting structure can be nonperturbatively realized\n using the contraction mapping theorem. I will report on the numerical impl ementation of the idea of solving unitarity\nwith contraction mappings in a simplified context of 2d S-matrices.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Lupsasca (Princeton Gravity Initiative) DTSTART:20210212T184500Z DTEND:20210212T194500Z DTSTAMP:20260404T111416Z UID:PUHET/11 DESCRIPTION:Title: The Black Hole Photon Ring\nby Alex Lupsasca (Princeton Gravity Initiative) as part of Princeton HET seminar\n\n\nAbstract\nThe photon rin g is a narrow ring-shaped feature\, predicted by GR but not yet observed\, that appears on images of sources near a black hole. It is caused by extr eme bending of light within a few Schwarzschild radii of the event horizon and provides a direct probe of the unstable bound photon orbits of the Ke rr geometry. I will review the origin and structure of the photon ring\, b efore discussing the prospects for its future detection. I will argue that the precise shape of the observable photon ring is remarkably insensitive to the astronomical source profile and can therefore be used as a stringe nt test of GR. A space-based interferometry experiment targeting the photo n ring of M87* could test the Kerr nature of the source to the sub-sub-per cent level.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Ying-Hsuan Lin (Harvard) DTSTART:20210222T193000Z DTEND:20210222T203000Z DTSTAMP:20260404T111416Z UID:PUHET/12 DESCRIPTION:Title: Lorentzian Dynamics and Factorization Beyond Rationality\nby Yin g-Hsuan Lin (Harvard) as part of Princeton HET seminar\n\n\nAbstract\nI mo tivate my talk with three questions in (1+1)d CFT: (1) What is the interpr etation of correlators in neither Euclidean nor Lorentzian regime? (2) Is there a connection between Lorentzian dynamics and line operators? (3) Can the Verlinde algebra be made sense of in irrational theories? I will argu e that the answer to (3) is "yes"\, and via (2) this "algebra" can put non trivial unitarity bounds ("opacity bound") on the conformal Regge limit of four-point functions. Topological defect lines play a key role in this st ory. More details can be found in my paper 2012.01429.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Scott Collier (PCTS) DTSTART:20210226T184500Z DTEND:20210226T194500Z DTSTAMP:20260404T111416Z UID:PUHET/13 DESCRIPTION:Title: Comments on the Narain ensemble of free CFTs\nby Scott Collier ( PCTS) as part of Princeton HET seminar\n\n\nAbstract\nI will discuss the s pectral statistics of primary operators in the recently formulated ensembl e average of Narain's family of free boson CFTs\, which provides an explic it (though rather exotic) example of an averaged AdS$_3$/CFT$_2$ holograph ic duality. I will focus on the computation of higher moments of the torus partition function\, and will present an explicit computation of the spec tral form factor of the dual ``U(1) gravity\,'' which can be written in te rms of a suitable analytic continuation of a degree-two Eisenstein series. I will identify the terms in the sum over ``geometries'' that lead to a l ate-time plateau in the spectral form factor\, and will demonstrate the ab sence of a linear ramp approaching the plateau from below. If time permits \, I will also discuss some ongoing work using Narain's family of CFTs as a testing ground for the incorporation of the spectral theory of automorph ic forms into the two-dimensional conformal bootstrap.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Belin (CERN) DTSTART:20210308T193000Z DTEND:20210308T203000Z DTSTAMP:20260404T111416Z UID:PUHET/14 DESCRIPTION:Title: The OPE Randomness Hypothesis and Euclidean Wormholes\nby Alex B elin (CERN) as part of Princeton HET seminar\n\n\nAbstract\nRecent develop ments in holography indicate that the semi-classical Euclidean path-integr al of Einstein gravity is much more powerful than previously anticipated. It is capable of reproducing a unitary Page curve for black hole evaporati on\, and can even capture some features of the discrete nature of black ho le microstates. Wormhole geometries play a key role in this context. I wil l propose a mechanism to explain this in the CFT: the OPE Randomness Hypot hesis. This ansatz is a generalization of the Eigenstate Thermalization Hy pothesis which applies to chaotic CFTs\, and treats OPE coefficients of he avy operators as random variables with a given probability distribution. I will present two applications of this framework: First\, it resolves a fa ctorization puzzle in AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz and Maldacena. Second\, it provides an argument against global sym metries in quantum gravity.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Harlow (MIT) DTSTART:20210312T184500Z DTEND:20210312T194500Z DTSTAMP:20260404T111416Z UID:PUHET/15 DESCRIPTION:Title: Algebra of diffeomorphism-invariant operators in JT gravity from the Peierls bracket\nby Daniel Harlow (MIT) as part of Princeton HET semi nar\n\n\nAbstract\nIn this talk I will discuss recent work with Jie-qiang Wu\, where we use the covariant method of Peierls to compute the algebra o f a wide variety of diffeomorphism-invariant operators in arbitrary states of Jackiw-Teitelboim gravity coupled to matter. We are then able to reca st many recent results as consequences of this algebra\, including the scr ambling time calculations of Shenker and Stanford\, the traversable wormho le of Gao\, Jafferis\, and Wall\, and the SL(2\,R) generators of Lin\, Mal dacena\, and Zhao. We are also able to clarify some aspects of the "firew all typicality" argument of Marolf and Polchinski. The algebra is quite r ich\, so we suspect there are more applications to be discovered.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Grisha Tarnopolskiy (Harvard) DTSTART:20210326T174500Z DTEND:20210326T184500Z DTSTAMP:20260404T111416Z UID:PUHET/16 DESCRIPTION:Title: Conformal operators in SYK-like models and their numerical effects\nby Grisha Tarnopolskiy (Harvard) as part of Princeton HET seminar\n\n\ nAbstract\nQuantum mechanical models with random interactions have an infi nite number of bilinear operators\,\nthe scaling dimensions of which can b e computed explicitly in the large N limit.\nThe lowest dimension operator s play an important role in thermodynamical\nproperties of these models an d define the behavior of various\ncorrelation functions in the infrared li mit.\nIn this talk I’ll show that some SYK-like models have operators\nw ith unusual anomalous dimensions. I also demonstrate how\nthey can be obse rved in numerical computations.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Alfredo Guevara (Harvard) DTSTART:20210409T174500Z DTEND:20210409T184500Z DTSTAMP:20260404T111416Z UID:PUHET/17 DESCRIPTION:Title: New holomorphic features of celestial correlation functions\nby Alfredo Guevara (Harvard) as part of Princeton HET seminar\n\n\nAbstract\n The talk will be split in two parts. In part I we present a new infinite d imensional symmetry algebra underlying scattering of gluons and gravitons. It extends the leading and subleading generators by an infinite tower of soft modes located at negative integer weights. We derive the correspondin g OPEs and show how this is the minimal consistent extension of previous r esults. Based on hep-th/2103.03961.\n\nIn part II we will analyze celestia l holography in the context of 3D models such as large-N O(N) and Chern-Si mons matter theory. In these models a non-perturbative computation can be carried out leading to novel features in the celestial 4-point function\, including crossing-symmetry relations and the conformal partial wave expan sion\, extending previous work of Lam and Shao. Work in progress with J. K ulp\, J. Wu (Perimeter) and Garcia-Sepulveda (Chicago).\n LOCATION:https://stable.researchseminars.org/talk/PUHET/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Jordan Cotler (Harvard) DTSTART:20210322T183000Z DTEND:20210322T193000Z DTSTAMP:20260404T111416Z UID:PUHET/19 DESCRIPTION:Title: Black hole microstate statistics from Euclidean wormholes\nby Jo rdan Cotler (Harvard) as part of Princeton HET seminar\n\n\nAbstract\nIn m odels of 2D dilaton gravity\, it has been shown that wormhole amplitudes e ncode black hole microstate level statistics. These statistics quantitati vely agree with predictions of random matrix theory for chaotic quantum sy stems\; this behavior is realized since the 2D theories in question are du al to matrix models. But what about black hole microstate statistics for Einstein gravity in 3D and higher spacetime dimensions\, and ultimately in string theory? We will discuss progress in these directions. In AdS3\, we compute a wormhole amplitude that encodes the energy level statistics o f BTZ black holes. In 4D and higher\, we discover analogous wormholes whi ch appear to encode the level statistics of small black holes just above t hreshold\; we find that the 1-loop approximations have a short-distance di vergence in pure Einstein gravity and so are sensitive to the details of U V completion. Finally\, we study analogous Euclidean wormholes in supergr avity on AdS5 x S5 and provide evidence that they encode the level statist ics of small black holes just above threshold. Remarkably\, these wormhol es appear stable in a certain parameter regime\, and dominate over the nuc leation of brane-anti-brane pairs in the computation of the spectral form factor at late Lorentzian time.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Soumyadeep Chaudhuri (Hebrew University of Jerusalem) DTSTART:20210423T174500Z DTEND:20210423T184500Z DTSTAMP:20260404T111416Z UID:PUHET/20 DESCRIPTION:Title: Thermal order in large N conformal gauge theories\nby Soumyadeep Chaudhuri (Hebrew University of Jerusalem) as part of Princeton HET semin ar\n\n\nAbstract\nOur experience with many physical systems tells us that usually when a symmetry is spontaneously broken at low temperatures\, it i s restored upon increasing the temperature sufficiently. The abundance of such systems raises the question of whether this is a universal feature o f all quantum systems. In this talk\, I will present examples of (3+1)-dim ensional non-supersymmetric large N gauge theories which demonstrate viola tions of the above feature. I will argue that in the N tending to infinity limit\, these theories have conformal manifolds which survive under all l oop corrections to the beta functions of the couplings. I will show that u nder certain conditions\, a subset of points on such a conformal manifold demonstrates the spontaneous breaking of a global symmetry at all nonzero temperatures. Furthermore\, I will demonstrate that this symmetry breaking is accompanied by the Higgsing of a subset of gauge bosons leading the sy stem to be in a persistent Brout-Englert-Higgs phase\n LOCATION:https://stable.researchseminars.org/talk/PUHET/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Anatoly Dymarsky (University of Kentucky) DTSTART:20210514T174500Z DTEND:20210514T184500Z DTSTAMP:20260404T111416Z UID:PUHET/21 DESCRIPTION:by Anatoly Dymarsky (University of Kentucky) as part of Prince ton HET seminar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/PUHET/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Philip Saad (IAS) DTSTART:20210419T183000Z DTEND:20210419T193000Z DTSTAMP:20260404T111416Z UID:PUHET/22 DESCRIPTION:Title: Wormholes without averaging\nby Philip Saad (IAS) as part of Pri nceton HET seminar\n\n\nAbstract\nAfter averaging over fermion couplings\, SYK has a collective field description that sometimes has “wormhole” solutions. We study the fate of these wormholes when the couplings are fix ed. Working mainly in a simple model\, we find that the wormhole saddles p ersist\, but that new saddles also appear elsewhere in the integration spa ce – “half-wormholes.” The wormhole contributions depend only weakly on the specific choice of couplings\, while the half-wormhole contributio ns are strongly sensitive. The half-wormholes are crucial for factorizatio n of decoupled systems with fixed couplings\, but they vanish after averag ing\, leaving the non-factorizing wormhole behind.\n LOCATION:https://stable.researchseminars.org/talk/PUHET/22/ END:VEVENT END:VCALENDAR