Monday, June 22nd, 2026
Workshop: Nathan Seiberg - Part 1
Time: 9:30 AM - 10:30 AM
Location: SCGP 102
Title: Proliferation Transitions from a 2+1d TQFT - Part 1
Speaker: Nathan Seiberg - Part 1
Abstract: It is common to study maps between different topological quantum field theories. We will explore descriptions of such maps as phase transitions in a non-topological transition field theory. From a field-theoretic perspective, these are phases of Chern-Simons matter theories and the transitions between them. From a condensed-matter perspective, these are distinct topological orders, e.g., distinct quantum Hall states. In particular, we will describe transitions between different phases that are misleadingly being referred to as “anyon condensation.” This is joint work with Meng Cheng. Although there will be some overlap, this talk will be quite different from recent talks I gave on related topics and will include several new unpublished results. In particular, we will analyze the symmetries of the transition field theories and will uncover unusual global symmetries.
Title: Proliferation Transitions from a 2+1d TQFT - Part 1
Speaker: Nathan Seiberg - Part 1
Abstract: It is common to study maps between different topological quantum field theories. We will explore descriptions of such maps as phase transitions in a non-topological transition field theory. From a field-theoretic perspective, these are phases of Chern-Simons matter theories and the transitions between them. From a condensed-matter perspective, these are distinct topological orders, e.g., distinct quantum Hall states. In particular, we will describe transitions between different phases that are misleadingly being referred to as “anyon condensation.” This is joint work with Meng Cheng. Although there will be some overlap, this talk will be quite different from recent talks I gave on related topics and will include several new unpublished results. In particular, we will analyze the symmetries of the transition field theories and will uncover unusual global symmetries.
Workshop: Nathan Seiberg - Part 2
Time: 11:00 AM - 12:00 PM
Location: SCGP 102
Title: Proliferation Transitions from a 2+1d TQFT - Part 2
Speaker: Nathan Seiberg - Part 2
Abstract: It is common to study maps between different topological quantum field theories. We will explore descriptions of such maps as phase transitions in a non-topological transition field theory. From a field-theoretic perspective, these are phases of Chern-Simons matter theories and the transitions between them. From a condensed-matter perspective, these are distinct topological orders, e.g., distinct quantum Hall states. In particular, we will describe transitions between different phases that are misleadingly being referred to as “anyon condensation.” This is joint work with Meng Cheng. Although there will be some overlap, this talk will be quite different from recent talks I gave on related topics and will include several new unpublished results. In particular, we will analyze the symmetries of the transition field theories and will uncover unusual global symmetries.
Title: Proliferation Transitions from a 2+1d TQFT - Part 2
Speaker: Nathan Seiberg - Part 2
Abstract: It is common to study maps between different topological quantum field theories. We will explore descriptions of such maps as phase transitions in a non-topological transition field theory. From a field-theoretic perspective, these are phases of Chern-Simons matter theories and the transitions between them. From a condensed-matter perspective, these are distinct topological orders, e.g., distinct quantum Hall states. In particular, we will describe transitions between different phases that are misleadingly being referred to as “anyon condensation.” This is joint work with Meng Cheng. Although there will be some overlap, this talk will be quite different from recent talks I gave on related topics and will include several new unpublished results. In particular, we will analyze the symmetries of the transition field theories and will uncover unusual global symmetries.
Workshop: Sahand Seifnashri
Time: 1:20 PM - 1:50 PM
Location: SCGP 102
Title: TBD
Speaker: Sahand Seifnashri
Abstract: TBD
Title: TBD
Speaker: Sahand Seifnashri
Abstract: TBD
Workshop: Shlomo Razamat
Time: 2:10 PM - 2:40 PM
Location: SCGP 102
Title: TBD
Speaker: Shlomo Razamat
Abstract: TBD
Title: TBD
Speaker: Shlomo Razamat
Abstract: TBD
Workshop: Zechuan Zheng
Time: 3:00 PM - 3:30 PM
Location: SCGP 102
Title: TBD
Speaker: Zechuan Zheng
Abstract: TBD
Title: TBD
Speaker: Zechuan Zheng
Abstract: TBD
Workshop: Rishi Mouland
Time: 4:00 PM - 4:30 PM
Location: SCGP 102
Title: A Tale of Two Fermions
Speaker: Rishi Mouland
Abstract: An anomaly for a global symmetry G says “no”. It stops us from driving the theory to a trivially gapped phase while preserving G. Relatedly, it also prevents us from constructing boundary conditions that preserve G, without adding additional boundary degrees of freedom. Does a vanishing anomaly say “yes”? It has been proposed that both of these statements can be upgraded to “if and only if” statements. We probe both of these proposals in the simplest theory in which they are non-trivial: the theory of two Dirac fermions in two dimensions, with G chiral. Along the way, we will construct all self-duality defects of two free Weyl fermions that arise from gauging an invertible symmetry. These play a central role then in the construction of symmetric boundaries for two Dirac fermions.
Title: A Tale of Two Fermions
Speaker: Rishi Mouland
Abstract: An anomaly for a global symmetry G says “no”. It stops us from driving the theory to a trivially gapped phase while preserving G. Relatedly, it also prevents us from constructing boundary conditions that preserve G, without adding additional boundary degrees of freedom. Does a vanishing anomaly say “yes”? It has been proposed that both of these statements can be upgraded to “if and only if” statements. We probe both of these proposals in the simplest theory in which they are non-trivial: the theory of two Dirac fermions in two dimensions, with G chiral. Along the way, we will construct all self-duality defects of two free Weyl fermions that arise from gauging an invertible symmetry. These play a central role then in the construction of symmetric boundaries for two Dirac fermions.
Tuesday, June 23rd, 2026
Workshop: David Tong - Part 1
Time: 9:30 AM - 10:30 AM
Location: SCGP 102
Title: What I Don't Understand About Monopole-Fermion Scattering - Part 1
Speaker: David Tong - Part 1
Abstract: The scattering of chiral fermions off monopoles is weird. The fermions bounce back in a twisted sector of the Hilbert space, with quantum numbers that can't be described by conventional particle scattering. This process has now been described from various perspectives, including CFT boundary states, rotor models, half-gauging and non-invertible symmetries. I'll describe this progress but also explain what we (or I) don't yet understand, both the technical challenges and the interpretational issues.
Title: What I Don't Understand About Monopole-Fermion Scattering - Part 1
Speaker: David Tong - Part 1
Abstract: The scattering of chiral fermions off monopoles is weird. The fermions bounce back in a twisted sector of the Hilbert space, with quantum numbers that can't be described by conventional particle scattering. This process has now been described from various perspectives, including CFT boundary states, rotor models, half-gauging and non-invertible symmetries. I'll describe this progress but also explain what we (or I) don't yet understand, both the technical challenges and the interpretational issues.
Workshop: David Tong - Part 2
Time: 11:00 AM - 12:00 PM
Location: SCGP 102
Title: What I Don't Understand About Monopole-Fermion Scattering - Part 2
Speaker: David Tong - Part 2
Abstract: The scattering of chiral fermions off monopoles is weird. The fermions bounce back in a twisted sector of the Hilbert space, with quantum numbers that can't be described by conventional particle scattering. This process has now been described from various perspectives, including CFT boundary states, rotor models, half-gauging and non-invertible symmetries. I'll describe this progress but also explain what we (or I) don't yet understand, both the technical challenges and the interpretational issues.
Title: What I Don't Understand About Monopole-Fermion Scattering - Part 2
Speaker: David Tong - Part 2
Abstract: The scattering of chiral fermions off monopoles is weird. The fermions bounce back in a twisted sector of the Hilbert space, with quantum numbers that can't be described by conventional particle scattering. This process has now been described from various perspectives, including CFT boundary states, rotor models, half-gauging and non-invertible symmetries. I'll describe this progress but also explain what we (or I) don't yet understand, both the technical challenges and the interpretational issues.
Workshop: Thomas Dumitrescu- Part 1
Time: 1:15 PM - 2:15 PM
Location: SCGP 102
Title: TBD
Speaker: Thomas Dumitrescu- Part 1
Abstract: TBD
Title: TBD
Speaker: Thomas Dumitrescu- Part 1
Abstract: TBD
Workshop: Thomas Dumitrescu- Part 2
Time: 2:30 PM - 3:30 PM
Location: SCGP 102
Title: TBD
Speaker: Thomas Dumitrescu- Part 2
Abstract: TBD
Title: TBD
Speaker: Thomas Dumitrescu- Part 2
Abstract: TBD
Wednesday, June 24th, 2026
Workshop: Ruben Verrensen - Part 1
Time: 9:30 AM - 10:30 AM
Location: SCGP 102
Title: Gapless Symmetry-Protected Topological Phases: Meta-Anomalies and Exact Solvability - Part 1
Speaker: Ruben Verresen - Part 1
Abstract: Symmetry-protected topological (SPT) phases are well-understood when the low-energy theory is topological, i.e., the ground state is gapped. However, some SPT properties, like response functions and edge modes, can persist even if the bulk energy gap closes. More interesting still, gapless systems can enable SPTs which are impossible in any gapped theory. In this blackboard talk, I will explain such 'intrinsically gapless SPT phases' using an exactly-solvable lattice model. I will argue that its edge theory is meta-anomalous: its anomalous symmetry that can only live on the boundary of a higher-dimensional anomalous theory.
Title: Gapless Symmetry-Protected Topological Phases: Meta-Anomalies and Exact Solvability - Part 1
Speaker: Ruben Verresen - Part 1
Abstract: Symmetry-protected topological (SPT) phases are well-understood when the low-energy theory is topological, i.e., the ground state is gapped. However, some SPT properties, like response functions and edge modes, can persist even if the bulk energy gap closes. More interesting still, gapless systems can enable SPTs which are impossible in any gapped theory. In this blackboard talk, I will explain such 'intrinsically gapless SPT phases' using an exactly-solvable lattice model. I will argue that its edge theory is meta-anomalous: its anomalous symmetry that can only live on the boundary of a higher-dimensional anomalous theory.
Workshop: Ruben Verrensen - Part 2
Time: 11:00 AM - 12:00 PM
Location: SCGP 102
Title: Gapless Symmetry-Protected Topological Phases: Meta-Anomalies and Exact Solvability - Part 2
Speaker: Ruben Verresen - Part 2
Abstract: Symmetry-protected topological (SPT) phases are well-understood when the low-energy theory is topological, i.e., the ground state is gapped. However, some SPT properties, like response functions and edge modes, can persist even if the bulk energy gap closes. More interesting still, gapless systems can enable SPTs which are impossible in any gapped theory. In this blackboard talk, I will explain such 'intrinsically gapless SPT phases' using an exactly-solvable lattice model. I will argue that its edge theory is meta-anomalous: its anomalous symmetry that can only live on the boundary of a higher-dimensional anomalous theory.
Title: Gapless Symmetry-Protected Topological Phases: Meta-Anomalies and Exact Solvability - Part 2
Speaker: Ruben Verresen - Part 2
Abstract: Symmetry-protected topological (SPT) phases are well-understood when the low-energy theory is topological, i.e., the ground state is gapped. However, some SPT properties, like response functions and edge modes, can persist even if the bulk energy gap closes. More interesting still, gapless systems can enable SPTs which are impossible in any gapped theory. In this blackboard talk, I will explain such 'intrinsically gapless SPT phases' using an exactly-solvable lattice model. I will argue that its edge theory is meta-anomalous: its anomalous symmetry that can only live on the boundary of a higher-dimensional anomalous theory.
Workshop: Enrico Andriolo
Time: 1:20 PM - 1:50 PM
Location: SCGP 102
Title: TBD
Speaker: Enrico Andriolo
Abstract: TBD
Title: TBD
Speaker: Enrico Andriolo
Abstract: TBD
Workshop: Luisa Eck
Time: 2:10 PM - 2:40 PM
Location: SCGP 102
Title: Non-invertible symmetry enriched topological orders
Speaker: Luisa Eck
Abstract: Topological orders enriched by group symmetries are well studied in both mathematics and physics, with symmetry twist defects described by G-crossed braided extensions. In this talk, I will outline a generalization to non-invertible symmetries. The starting point is a full inclusion of one fusion category into another, and the resulting twist defects are described by the relative center. I will explain how the symmetry action on anyons can be computed using tube algebra methods, and how it can send a single anyon to a sum of anyons and twist defects. The main example comes from Z2 inside S3, giving a non-invertible symmetry action on toric code anyons. Time permitting, I will also describe extensions of this framework to condensation string-net models and chiral topological orders. The talk is based on arXiv:2605.28794 with Peter Huston, Kyle Kawagoe, and David Penneys.
Title: Non-invertible symmetry enriched topological orders
Speaker: Luisa Eck
Abstract: Topological orders enriched by group symmetries are well studied in both mathematics and physics, with symmetry twist defects described by G-crossed braided extensions. In this talk, I will outline a generalization to non-invertible symmetries. The starting point is a full inclusion of one fusion category into another, and the resulting twist defects are described by the relative center. I will explain how the symmetry action on anyons can be computed using tube algebra methods, and how it can send a single anyon to a sum of anyons and twist defects. The main example comes from Z2 inside S3, giving a non-invertible symmetry action on toric code anyons. Time permitting, I will also describe extensions of this framework to condensation string-net models and chiral topological orders. The talk is based on arXiv:2605.28794 with Peter Huston, Kyle Kawagoe, and David Penneys.
Workshop: Abijith Krishnan
Time: 3:00 PM - 3:30 PM
Location: SCGP 102
Title: TBD
Speaker: Abijith Krishnan
Abstract: TBD
Title: TBD
Speaker: Abijith Krishnan
Abstract: TBD
Thursday, June 25th, 2026
Workshop: Hayden Lee - Part 1
Time: 9:30 AM - 10:30 AM
Location: SCGP 102
Title: TBD
Speaker: Hayden Lee - Part 1
Abstract: TBD
Title: TBD
Speaker: Hayden Lee - Part 1
Abstract: TBD
Workshop: Hayden Lee - Part 2
Time: 11:00 AM - 12:00 PM
Location: SCGP 102
Title: TBD
Speaker: Hayden Lee - Part 2
Abstract: TBD
Title: TBD
Speaker: Hayden Lee - Part 2
Abstract: TBD
Workshop: Neil Turok
Time: 1:30 PM - 2:00 PM
Location: SCGP 102
Title: Conformally Flat Limit of Quadratic Gravity
Speaker: Neil Turok
Abstract: Quadratic Gravity is a renormalizable theory of quantum gravity. However, it is plagued by ghosts making its Lorentzian version hard to interpret. In the limit where one of its two dimensionless couplings vanishes, the theory reduces to an interacting, asymptotically free four-derivative scalar theory, describing the local scale factor of spacetime. Through a careful covariant quantization, we show that the four-derivative theory is causal and physically unitary, yielding only positive transition probabilities in spite of the presence of negative norm (or ghost) states. The key to the proof is a hidden ghost parity symmetry, revealed by embedding the four-derivative theory in a larger, two-derivative O(1,1) symmetric model. The resulting theory appears to be a UV-complete, non-perturbative formulation of quantum gravity in four dimensions, albeit without gravitons. If time allows I will briefly discuss implications for Polchinski's conjecture and the a-theorem.
Title: Conformally Flat Limit of Quadratic Gravity
Speaker: Neil Turok
Abstract: Quadratic Gravity is a renormalizable theory of quantum gravity. However, it is plagued by ghosts making its Lorentzian version hard to interpret. In the limit where one of its two dimensionless couplings vanishes, the theory reduces to an interacting, asymptotically free four-derivative scalar theory, describing the local scale factor of spacetime. Through a careful covariant quantization, we show that the four-derivative theory is causal and physically unitary, yielding only positive transition probabilities in spite of the presence of negative norm (or ghost) states. The key to the proof is a hidden ghost parity symmetry, revealed by embedding the four-derivative theory in a larger, two-derivative O(1,1) symmetric model. The resulting theory appears to be a UV-complete, non-perturbative formulation of quantum gravity in four dimensions, albeit without gravitons. If time allows I will briefly discuss implications for Polchinski's conjecture and the a-theorem.
Workshop: Isabel Garcia-Garcia
Time: 2:20 PM - 2:50 PM
Location: SCGP 102
Title: TBD
Speaker: Isabel Garcia-Garcia
Abstract: TBD
Title: TBD
Speaker: Isabel Garcia-Garcia
Abstract: TBD
Workshop: Liantao Wang
Time: 3:10 PM - 3:40 PM
Location: SCGP 102
Title: TBD
Speaker: Liantao Wang
Abstract: TBD
Title: TBD
Speaker: Liantao Wang
Abstract: TBD
Public Lecture: Neil Turok, Higgs Chair of Theoretical Physics, University of Edinburgh and Roger Penrose Distinguished Visiting Chair, Perimeter Institute for Theoretical Physics
Time: 5:00 PM - 6:00 PM
Location: 102
Title: A Simpler Cosmology
Abstract: Observations of the universe on the largest and smallest accessible scales have revealed surprising simplicity and confirmed many basic principles of physics. Might we be closer than we expected to understanding the fundamental laws governing the universe? In this lecture, I’ll outline a new, radically minimal approach guided by the observations and respecting the deepest symmetries we know of. According to the new picture, the big bang was a mirror at the beginning of time. The dark matter is a close cousin of a particle we already know, the neutrino. The large-scale fluctuations in the universe provide us with a direct view of the big bang and new insights into the unification of quantum physics with gravity.
Title: A Simpler Cosmology
Abstract: Observations of the universe on the largest and smallest accessible scales have revealed surprising simplicity and confirmed many basic principles of physics. Might we be closer than we expected to understanding the fundamental laws governing the universe? In this lecture, I’ll outline a new, radically minimal approach guided by the observations and respecting the deepest symmetries we know of. According to the new picture, the big bang was a mirror at the beginning of time. The dark matter is a close cousin of a particle we already know, the neutrino. The large-scale fluctuations in the universe provide us with a direct view of the big bang and new insights into the unification of quantum physics with gravity.
Friday, June 26th, 2026
Workshop: Chong Wang - Part 1
Time: 9:30 AM - 10:30 AM
Location: SCGP 102
Title: Self-dual Higgs transitions: Toric code and beyond - Part 1
Speaker: Chong Wang - Part 1
Abstract: The toric code, when deformed in a way that preserves the self-duality Z_2 symmetry exchanging the electric and magnetic excitations, admits a transition to a topologically trivial state that spontaneously breaks the Z_2 symmetry. Numerically, this transition was found to be continuous, which makes it particularly enigmatic given the longstanding absence of a continuum field-theoretic description. We propose an SO(4) Chern-Simons-Higgs (CSH) theory at level k=2 and argue that it serves as a natural field theory description of the self-dual transition. Moreover, it can be generalized to an entire series of theories labeled by an integer k. For each k>2, the theory describes an analogous transition involving different non-Abelian topological orders, such as the double Fibonacci order (k=3) and the S_3 quantum double (k=4). For k=1, we conjecture that the corresponding CSH transition is in fact infrared-dual to the 3d Ising transition, in close analogy with the particle-vortex duality of a complex scalar.
Title: Self-dual Higgs transitions: Toric code and beyond - Part 1
Speaker: Chong Wang - Part 1
Abstract: The toric code, when deformed in a way that preserves the self-duality Z_2 symmetry exchanging the electric and magnetic excitations, admits a transition to a topologically trivial state that spontaneously breaks the Z_2 symmetry. Numerically, this transition was found to be continuous, which makes it particularly enigmatic given the longstanding absence of a continuum field-theoretic description. We propose an SO(4) Chern-Simons-Higgs (CSH) theory at level k=2 and argue that it serves as a natural field theory description of the self-dual transition. Moreover, it can be generalized to an entire series of theories labeled by an integer k. For each k>2, the theory describes an analogous transition involving different non-Abelian topological orders, such as the double Fibonacci order (k=3) and the S_3 quantum double (k=4). For k=1, we conjecture that the corresponding CSH transition is in fact infrared-dual to the 3d Ising transition, in close analogy with the particle-vortex duality of a complex scalar.
Workshop: Chong Wang - Part 2
Time: 11:00 AM - 12:00 PM
Location: SCGP 102
Title: Self-dual Higgs transitions: Toric code and beyond - Part 2
Speaker: Chong Wang - Part 2
Abstract: The toric code, when deformed in a way that preserves the self-duality Z_2 symmetry exchanging the electric and magnetic excitations, admits a transition to a topologically trivial state that spontaneously breaks the Z_2 symmetry. Numerically, this transition was found to be continuous, which makes it particularly enigmatic given the longstanding absence of a continuum field-theoretic description. We propose an SO(4) Chern-Simons-Higgs (CSH) theory at level k=2 and argue that it serves as a natural field theory description of the self-dual transition. Moreover, it can be generalized to an entire series of theories labeled by an integer k. For each k>2, the theory describes an analogous transition involving different non-Abelian topological orders, such as the double Fibonacci order (k=3) and the S_3 quantum double (k=4). For k=1, we conjecture that the corresponding CSH transition is in fact infrared-dual to the 3d Ising transition, in close analogy with the particle-vortex duality of a complex scalar.
Title: Self-dual Higgs transitions: Toric code and beyond - Part 2
Speaker: Chong Wang - Part 2
Abstract: The toric code, when deformed in a way that preserves the self-duality Z_2 symmetry exchanging the electric and magnetic excitations, admits a transition to a topologically trivial state that spontaneously breaks the Z_2 symmetry. Numerically, this transition was found to be continuous, which makes it particularly enigmatic given the longstanding absence of a continuum field-theoretic description. We propose an SO(4) Chern-Simons-Higgs (CSH) theory at level k=2 and argue that it serves as a natural field theory description of the self-dual transition. Moreover, it can be generalized to an entire series of theories labeled by an integer k. For each k>2, the theory describes an analogous transition involving different non-Abelian topological orders, such as the double Fibonacci order (k=3) and the S_3 quantum double (k=4). For k=1, we conjecture that the corresponding CSH transition is in fact infrared-dual to the 3d Ising transition, in close analogy with the particle-vortex duality of a complex scalar.
Workshop: Gongjun Choi
Time: 1:20 PM - 1:50 PM
Location: SCGP 102
Title: Symmetry perspective on an exotic axion-photon coupling
Speaker: Gongjun Choi
Abstract: When the axion–photon coupling is generated by dyonic fermions in axion–Maxwell theory, it acquires an unconventional structure that differs from the standard coupling induced by purely electrically charged fermions. In this talk, we explore the construction of non-invertible chiral symmetry defect operators in this novel setting and investigate their implications for the Standard Model and the QCD axion.
Title: Symmetry perspective on an exotic axion-photon coupling
Speaker: Gongjun Choi
Abstract: When the axion–photon coupling is generated by dyonic fermions in axion–Maxwell theory, it acquires an unconventional structure that differs from the standard coupling induced by purely electrically charged fermions. In this talk, we explore the construction of non-invertible chiral symmetry defect operators in this novel setting and investigate their implications for the Standard Model and the QCD axion.
Workshop: Ruixian Siew
Time: 2:10 PM - 2:40 PM
Location: SCGP 102
Title: TBD
Speaker: Ruixian Siew
Abstract: TBD
Title: TBD
Speaker: Ruixian Siew
Abstract: TBD