# Physics Events

• Friday, February 23, 2018
High Energy Theory Seminar
“Splittability and Noether's Theorem in Quantum Field Theory”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): Daniel Harlow, Massachusetts Institute of Technology

Description: Noether's theorem is textbook material in quantum field theory, but among experts it has been known for a while that there are quantum field theories with continuous global symmetries which possess no conserved current.  In this talk I will give a few examples of this, and also describe a relationship between this phenomenon and a general property of algebraic quantum field theory called the split property.  In particular we will see that violations of the split property on manifolds other than $R^d$ can prevent the existence of a Noether current on $R^d$, even if the split property holds on $R^d$.  We will extend this notion to discrete global symmetries, and we will also see that all examples so far with "unsplittable" global symmetries  have the property that there is a topological sector with unbreakable surface operators''.  Finally we will conjecture that Noether's theorem, or more generally splittability of global symmetries, should hold in any quantum field theory which does not possess such a sector.

• Monday, February 26, 2018
High Energy Theory Seminar
“The Large N Melonic Limit of O(N) Tensor Models”

Location: Jadwin Hall, PCTS Seminar Room 407
Time: 2:30 PM
Speaker(s): Sylvain Carrozza, Perimeter Institute

Description: It has been recently recognized that the same type of melonic large N structure governs SYK models and tensor models alike. Following Witten and Klebanov-Tarnopolsky, this has led to the introduction of new SYK-like tensor models, which reproduce key features of SYK models in the familiar context of large N field theories.

Most of the literature on tensor models focuses on tensor fields transforming under r independent copies of a symmetry group G, where r is the rank of the tensor (for definiteness, I will focus on r=3 and G=O(N)). The Feynman expansion of such models is indexed by colored stranded diagrams, whose large N scalings are governed by a combinatorial quantity known as the Gurau degree. Tensor models transforming under a single copy of O(N) can be obtained by symmetrization and/or anti-symmetrization of the indices of the tensor. However, such theories turn out to generate a family of stranded diagrams with unbounded Gurau degree, which seems to preclude the construction of an interesting 1/N expansion. Nonetheless, Klebanov and Tarnopolsky recently reported compelling evidence in favour of the conjecture that symmetric tensors can actually support a melonic 1/N expansion, provided that they are also taken to be traceless. In this talk, I will outline the recent complete proof of this conjecture, and will explain why it holds more generally for arbitrary irreducible rank-3 tensor representations. Along the way, I will emphasize the crucial role of the traceless condition. I will conclude by discussing implications and possible generalizations of this result.

• Tuesday, February 27, 2018
Pheno & Vino Seminar
“Exploring Dark Sectors at FASER: ForwArd Search ExpeRiment at the LHC”

Location: Jadwin Hall, Room 303
Time: 4:00 PM
Speaker(s): Iftah Galon, Rutgers University

Description: New physics has traditionally been expected in the high-pT region at high-energy collider experiments. If new particles are light and weakly-coupled, however, this focus may be completely misguided: light particles are typically highly concentrated within a few mrad of the beam line, allowing sensitive searches with small detectors, and even extremely weakly-coupled particles may be produced in large numbers there.

In this talk I will discuss the recent proposal of FASER, ForwArd Search ExpeRiment at the LHC: a detector placed 480 m downstream of the ATLAS or CMS interaction point (IP) in the very forward region and operated concurrently there.

Even with a small and inexpensive cylindrical detector, of volume ~1 $m^3$, FASER would have a new physics discovery potential in a swath of currently unconstrained parameter-space which is comparable to, and complementary to, much larger proposed experiments. I explore this in the talk for models such as dark photons, dark higgses, axion-like particles, and heavy neutral leptons, and discuss some of the future experimental challenges involved.

• Wednesday, February 28, 2018
High Energy Physics Seminar
“The Tau Lepton as a Tool for SM Physics at CMS”

Location: Jadwin Hall, Room 303
Time: 2:00 PM
Speaker(s): Isobel Ojalvo, Princeton University

Description: This past year with data collected from the Large Hadron Collider (LHC) using the Compact Muon Solenoid experiment the first observation of the higgs in its decay to tau leptons with a single experiment was announced.  Due to its very short lifetime, the tau lepton is normally only possible to detect in its decay to lighter leptons and mesons and in a hadron collider it can be very easily mistaken for a quark or gluon jet. We discuss this exciting result, along with recent advances in tau trigger, reconstruction and identification which made this observation possible as well as prospects for future measurements at the LHC.

• Thursday, March 1, 2018
Hamilton Colloquium Series
“Magic Angle Graphene: A New Platform for Strongly Correlated Physics”

Location: Jadwin Hall, Room A10
Time: 4:00 PM
Speaker(s): Pablo Jarillo-Herrero, MIT

Description: The understanding of strongly correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, based on graphene moiré superlattices. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly correlated electronic system. These flat bands exhibit half-filling insulating phases at zero magnetic field, which we show to be a Mott-like insulator arising from electrons localized in the moiré superlattice. These unique properties of magic-angle twisted bilayer graphene open up a new playground for exotic many-body quantum phases in a 2D platform made of pure carbon and without magnetic field. The easy accessibility of the flat bands, the electrical tunability, and the bandwidth tunability through a twist angle may pave the way towards more exotic correlated systems, such as quantum spin liquids. I will end my talk with an interesting experimental surprise.

• Friday, March 2, 2018
High Energy Theory Seminar
“TBA”

Location: Jadwin Hall, PCTS Seminar Room 407
Time: 1:45 PM
Speaker(s): Shai Chester, Princeton University

• Monday, March 5, 2018
High Energy Theory Seminar
“Going with the Flow: A Solution to the Sign Problem”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): Kemal Gokce Basar, University of Illinois at Chicago

Description: I will explore the generalization of the Feynman path integral in quantum field theory to complexified fields, and explain how it can be utilized to tackle the famous "sign problem". The sign problem prevents first principle studies of real-time dynamics and finite density systems via lattice field theory and appears in many different areas in physics. I will discuss both conceptual and computational aspects of this idea and give examples of several interacting quantum field theories where it successfully solves the sign problem.

• Tuesday, March 6, 2018
Pheno & Vino Seminar
“TBA”

Location: Jadwin Hall, Room 303
Time: 4:00 PM
Speaker(s): Zackaria Chako, University of Maryland

• Friday, March 9, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, March 12, 2018
High Energy Theory Seminar
“TBA”

Location: Jadwin Hall, PCTS Seminar Room 407
Time: 2:30 PM
Speaker(s): Thomas Dumitrescu, Harvard University

• Tuesday, March 13, 2018
Pheno & Vino Seminar
“TBA”

Location: Jadwin Hall, Room 303
Time: 4:00 PM
Speaker(s): Patrick Meade, Stony Brook University

• Friday, March 16, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, March 19, 2018
High Energy Theory Seminar
“Tensor Networks as Geometry”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): Guifre Vidal, Perimeter Institute

Description: The multiscale entanglement renormalization ansatz (MERA) is a tensor network that can efficiently approximate ground states of critical spin chains --that is, lattice versions of 1+1 CFTs. Its network structure extends in an additional dimension corresponding to renormalization group scale. Accordingly, MERA has has been proposed to be a discrete realization of the AdS/CFT correspondence. While a first proposal speculated that MERA = discrete hyperbolic plane (time slice of AdS3), a second proposal conjectured that MERA = discrete 1+1 de Sitter. In this talk I will attach a geometry to MERA from the perspective of a CFT path integral. Surprisingly, the corresponding metric does not have euclidean nor lorentzian signature, but is instead degenerate. I will also describe how MERA can be modified to represent either the hyperbolic plane or 1+1 de Sitter.

• Tuesday, March 20, 2018
Pheno & Vino Seminar
“TBA”

Location: Jadwin Hall, Room 303
Time: 4:00 PM
Speaker(s): Patrick Meade, Stony Brook University

• Friday, March 23, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, March 26, 2018
High Energy Theory Seminar
“TBA”

Location: Jadwin Hall, PCTS Seminar Room 407
Time: 2:30 PM
Speaker(s): Ibrahima Bah, Johns Hopkins University

• Tuesday, March 27, 2018
Pheno & Vino Seminar
“TBA”

Location: Jadwin Hall, Room 303
Time: 4:00 PM
Speaker(s): Gustavo Marquis Tavares, Stanford University

• Friday, March 30, 2018
High Energy Theory Seminar
“TBA”

Location: Jadwin Hall, Room A06
Time: 1:45 PM
Speaker(s): Bruno Le Floch, Princeton University

• Monday, April 2, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): Cumrun Vafa, Harvard University

• Friday, April 6, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, April 9, 2018
PCTS Workshop
“Elastic Turbulence”

Location: Jadwin Hall, PCTS Seminar Room, Room 407
Time: 8:30 AM
Note: FREE, but REQUIRED REGISTRATION is limited and available online: http://wwwphy.princeton.edu/pcts/Turbulence2018/Turbulence2018.html

Description: Elastic turbulence is a chaotic, strongly fluctuating regime of a fluid flow, which, amazingly, occurs at low Reynolds numbers. This phenomenon, observed in polymer solutions, is driven by the strong coupling between the fluid velocity and its elasticity. The statistical features of the flow in this regime have been suggested to be universal, insensitive to the details of the viscoelastic fluid. As such, it may even be relevant as a source of chaos in flows of living organisms on microscopic scales, if the latter exhibit elastic stresses.

The aim of the workshop will be to bring together theoreticians and experimentalists to take stock of the field, and determine what are the outstanding problems and open questions.

We will be selecting a limited number of posters for display during the meeting. If you want to be considered, email the title and abstract for your poster to Anna Frishman, no later than the April 2nd, at frishman@princeton.edu.

• Tuesday, April 10, 2018
PCTS Workshop
“Elastic Turbulence”

Location: Jadwin Hall, PCTS Seminar Room, Room 407
Time: 8:30 AM
Note: FREE, but REQUIRED REGISTRATION is limited and available online: http://wwwphy.princeton.edu/pcts/Turbulence2018/Turbulence2018.html

Description: Elastic turbulence is a chaotic, strongly fluctuating regime of a fluid flow, which, amazingly, occurs at low Reynolds numbers. This phenomenon, observed in polymer solutions, is driven by the strong coupling between the fluid velocity and its elasticity. The statistical features of the flow in this regime have been suggested to be universal, insensitive to the details of the viscoelastic fluid. As such, it may even be relevant as a source of chaos in flows of living organisms on microscopic scales, if the latter exhibit elastic stresses.

The aim of the workshop will be to bring together theoreticians and experimentalists to take stock of the field, and determine what are the outstanding problems and open questions.

We will be selecting a limited number of posters for display during the meeting. If you want to be considered, email the title and abstract for your poster to Anna Frishman, no later than the April 2nd, at frishman@princeton.edu.

• Wednesday, April 11, 2018
PCTS Workshop
“Elastic Turbulence”

Location: Jadwin Hall, PCTS Seminar Room, Room 407
Time: 8:30 AM
Note: FREE, but REQUIRED REGISTRATION is limited and available online: http://wwwphy.princeton.edu/pcts/Turbulence2018/Turbulence2018.html

Description: Elastic turbulence is a chaotic, strongly fluctuating regime of a fluid flow, which, amazingly, occurs at low Reynolds numbers. This phenomenon, observed in polymer solutions, is driven by the strong coupling between the fluid velocity and its elasticity. The statistical features of the flow in this regime have been suggested to be universal, insensitive to the details of the viscoelastic fluid. As such, it may even be relevant as a source of chaos in flows of living organisms on microscopic scales, if the latter exhibit elastic stresses.

The aim of the workshop will be to bring together theoreticians and experimentalists to take stock of the field, and determine what are the outstanding problems and open questions.

We will be selecting a limited number of posters for display during the meeting. If you want to be considered, email the title and abstract for your poster to Anna Frishman, no later than the April 2nd, at frishman@princeton.edu.

• Thursday, April 12, 2018
Donald R. Hamilton Lecture
“TBA”

Location: McDonnell Hall, A02 Auditorium
Time: 8:00 PM
Speaker(s): Kip Thorne, Richard P. Feynman Professor of Theoretical Physics, Emeritus, California Institute of Technology (Caltech) and Winner of the 2017 Nobel Prize in Physics

• Friday, April 13, 2018
High Energy Theory Seminar
“TBA”

Location: Jadwin Hall, PCTS Seminar Room 407
Time: 1:45 PM
Speaker(s): Sarah Harrison, McGill University

• Monday, April 16, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): Nissan Itzhaki, Tel Aviv University

• Friday, April 20, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, April 30, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): TBA, TBA

• Friday, May 4, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 1:45 PM
Speaker(s): TBA, TBA

• Monday, May 7, 2018
High Energy Theory Seminar
“TBA”

Location: Bloomberg Lecture Hall
Time: 2:30 PM
Speaker(s): TBA, TBA