Triangle Seminars
Wednesday, 7 Oct 2026
Proliferation Transitions for Non-Abelian Anyons
📍 London
Andrea Antinucci
(Oxford U., Inst. Math.)
Abstract:
Phases of matter and the transitions between them are famously characterized within the Landau paradigm and Landau–Ginzburg theory: phases are labeled by broken or unbroken symmetries, while phase transitions are described in terms of scalar order parameters. There are, however, phases beyond the standard Landau paradigm that are distinguished not by the realization of ordinary symmetries, but by that of generalized global symmetries. Among these, topologically ordered phases in (2+1)d possess non-invertible 1-form symmetries described by anyon lines. In this talk, I will present a framework for describing transitions between topologically ordered phases related by anyon proliferation, which can be viewed as a non-invertible generalization of the choice of the unbroken symmetry. The resulting theories involve scalar fields coupled to gauge fields. A crucial ingredient in this construction is the (3+1)d Symmetry Topological Field Theory (SymTFT), which allows to separate symmetry from dynamics and will be employed in a rather unconventional way.
Phases of matter and the transitions between them are famously characterized within the Landau paradigm and Landau–Ginzburg theory: phases are labeled by broken or unbroken symmetries, while phase transitions are described in terms of scalar order parameters. There are, however, phases beyond the standard Landau paradigm that are distinguished not by the realization of ordinary symmetries, but by that of generalized global symmetries. Among these, topologically ordered phases in (2+1)d possess non-invertible 1-form symmetries described by anyon lines. In this talk, I will present a framework for describing transitions between topologically ordered phases related by anyon proliferation, which can be viewed as a non-invertible generalization of the choice of the unbroken symmetry. The resulting theories involve scalar fields coupled to gauge fields. A crucial ingredient in this construction is the (3+1)d Symmetry Topological Field Theory (SymTFT), which allows to separate symmetry from dynamics and will be employed in a rather unconventional way.
Posted by: Kiarash Naderi
Friday, 9 Oct 2026
Are All Phase Transitions of Landau Type in Disguise?
📍 London
Sakura Schafer-Nameki
(Oxford)
Abstract:
The answer is no. Landau's paradigm characterizes phases of matter by their pattern of spontaneous symmetry breaking, traditionally for groups, and has more recently been extended to so-called non-invertible or categorical symmetries. In this colloquium we will see how recent insights into these new symmetries teach us even new things about ordinary group symmetries.
Central to this endeavour is the symmetry topological field theory (SymTFT), which conveniently separates symmetry from dynamics. Gapped phases correspond to topological boundary conditions of the SymTFT, their order parameters, local operators as well as string-operators, to the topological lines in the SymTFT, and phase transitions to condensable algebras.
Many transitions that appear to be beyond Landau, such as transitions between symmetry-protected topological (SPT) phases and certain deconfined quantum critical points in 1+1d, become symmetry-breaking transitions, i.e. of Landau type, after gauging. This may hint at the possibility that all transitions are, after suitable gauging and other manipulations, of Landau symmetry-breaking type. I will explain how, with the help of the SymTFT, we can uncover phase transitions which do not admit any dual frame that would make them of Landau type. Such so-called twin phase transitions occur already for finite groups. This brings us full circle: even for group symmetries, we can learn something new from the recent developments in generalized and categorical symmetries.
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Colloquium at 3 PM, 9 Oct 2026
https://lims.ac.uk/event/are-all-phase-transitions-of-landau-type-in-disguise/
The answer is no. Landau's paradigm characterizes phases of matter by their pattern of spontaneous symmetry breaking, traditionally for groups, and has more recently been extended to so-called non-invertible or categorical symmetries. In this colloquium we will see how recent insights into these new symmetries teach us even new things about ordinary group symmetries.
Central to this endeavour is the symmetry topological field theory (SymTFT), which conveniently separates symmetry from dynamics. Gapped phases correspond to topological boundary conditions of the SymTFT, their order parameters, local operators as well as string-operators, to the topological lines in the SymTFT, and phase transitions to condensable algebras.
Many transitions that appear to be beyond Landau, such as transitions between symmetry-protected topological (SPT) phases and certain deconfined quantum critical points in 1+1d, become symmetry-breaking transitions, i.e. of Landau type, after gauging. This may hint at the possibility that all transitions are, after suitable gauging and other manipulations, of Landau symmetry-breaking type. I will explain how, with the help of the SymTFT, we can uncover phase transitions which do not admit any dual frame that would make them of Landau type. Such so-called twin phase transitions occur already for finite groups. This brings us full circle: even for group symmetries, we can learn something new from the recent developments in generalized and categorical symmetries.
–-
Colloquium at 3 PM, 9 Oct 2026
https://lims.ac.uk/event/are-all-phase-transitions-of-landau-type-in-disguise/
Posted by: JUVEN WANG