Triangle Seminars
Tuesday, 5 Oct 2021
Aspects of the black hole/string transition
Yiming Chen
(Princeton University)
Abstract:
Abstract: It has long been speculated that a black hole in string theory turns into highly excited strings close to the Hagedorn temperature. Gravitational attraction pulls different parts of the string together, forming a star-like configuration. In this talk, I will review the properties of a concrete solution of this kind, first discovered by Horowitz and Polchinski. I will discuss whether the Horowitz-Polchinski solution can be smoothly connected with the black hole as worldsheet CFTs. I will also discuss how the story can be generalized to charged cases, as well as its implication on the near extremal limit.
Abstract: It has long been speculated that a black hole in string theory turns into highly excited strings close to the Hagedorn temperature. Gravitational attraction pulls different parts of the string together, forming a star-like configuration. In this talk, I will review the properties of a concrete solution of this kind, first discovered by Horowitz and Polchinski. I will discuss whether the Horowitz-Polchinski solution can be smoothly connected with the black hole as worldsheet CFTs. I will also discuss how the story can be generalized to charged cases, as well as its implication on the near extremal limit.
Posted by: IC
Wednesday, 6 Oct 2021
Instantons, symmetries and anomalies in five dimensions
📍 London
Pietro Benetti Genolini
(KCL / Cambridge Univ. DAMTP)
Abstract:
Five-dimensional non-abelian gauge theories have a U(1) global symmetry associated with instantonic particles. I will describe a mixed 't Hooft anomaly between this and other global symmetries of the theory, namely the one-form center symmetry or ordinary flavor symmetry for theories with fundamental matter. I will then apply these results to supersymmetric gauge theories, analysing the symmetry enhancement patterns occurring at their conjectured RG fixed points.
Five-dimensional non-abelian gauge theories have a U(1) global symmetry associated with instantonic particles. I will describe a mixed 't Hooft anomaly between this and other global symmetries of the theory, namely the one-form center symmetry or ordinary flavor symmetry for theories with fundamental matter. I will then apply these results to supersymmetric gauge theories, analysing the symmetry enhancement patterns occurring at their conjectured RG fixed points.
Posted by: andrea
Constructing the 6 Loop 4 Point N=4 super-Yang-Mills Integrand
Alex Edison
(Uppsala U.)
Abstract:
In this talk, we'll discuss the current state-of-the-art for constructing multi-loop integrands in N=4 super-Yang-Mills. After briefly covering some of the key goals, background, and ideas behind the multiloop integrand program, we turn to the cutting edge: constructing the complete (planar and non-planar) integrand for the six-loop four-point amplitude in maximal \(D\le10\) super-Yang-Mills. This construction employs new advances that combat the proliferation of loops and state-sums when evaluating multi-loop \(D\)-dimensional unitarity cuts. Concretely, it uses two graph-based approaches, applicable in a range of theories, to evaluating generalized unitarity cuts in \(D\) dimensions: 1) recursively from lower-loop cuts, or 2) directly from known higher-loop planar cuts. Neither method relies on explicit state sums or any sewing of tree-level amplitudes. The first method meshes particularly well with the Method of Maximal Cuts to allow direct construction of the complete six-loop integrand.
In this talk, we'll discuss the current state-of-the-art for constructing multi-loop integrands in N=4 super-Yang-Mills. After briefly covering some of the key goals, background, and ideas behind the multiloop integrand program, we turn to the cutting edge: constructing the complete (planar and non-planar) integrand for the six-loop four-point amplitude in maximal \(D\le10\) super-Yang-Mills. This construction employs new advances that combat the proliferation of loops and state-sums when evaluating multi-loop \(D\)-dimensional unitarity cuts. Concretely, it uses two graph-based approaches, applicable in a range of theories, to evaluating generalized unitarity cuts in \(D\) dimensions: 1) recursively from lower-loop cuts, or 2) directly from known higher-loop planar cuts. Neither method relies on explicit state sums or any sewing of tree-level amplitudes. The first method meshes particularly well with the Method of Maximal Cuts to allow direct construction of the complete six-loop integrand.
Posted by: QMW
Thursday, 7 Oct 2021
The Gravitino and the Swampland
Dieter Lust
(Munich)
Abstract:
[for zoom details please email s.nagy@qmul.ac.uk]
In this talk we discuss a new swampland conjecture stating that the limit of vanishing gravitino mass corresponds to the massless limit of an infinite tower of states and to the consequent breakdown of the effective field theory. The proposal can be tested in large classes of models coming from compactification of string theory to four dimensions, where we identify the Kaluza-Klein nature of the tower of states becoming light. We point out a general relation between the gravitino mass and an abelian gauge coupling, which allows us to connect our conjecture to the weak gravity conjecture or the absence of global symmetries in quantum gravity. We discuss phenomenological implications of our conjecture in (quasi-)de Sitter backgrounds and extract a lower bound for the gravitino mass in terms of the Hubble parameter.
[for zoom details please email s.nagy@qmul.ac.uk]
In this talk we discuss a new swampland conjecture stating that the limit of vanishing gravitino mass corresponds to the massless limit of an infinite tower of states and to the consequent breakdown of the effective field theory. The proposal can be tested in large classes of models coming from compactification of string theory to four dimensions, where we identify the Kaluza-Klein nature of the tower of states becoming light. We point out a general relation between the gravitino mass and an abelian gauge coupling, which allows us to connect our conjecture to the weak gravity conjecture or the absence of global symmetries in quantum gravity. We discuss phenomenological implications of our conjecture in (quasi-)de Sitter backgrounds and extract a lower bound for the gravitino mass in terms of the Hubble parameter.
Posted by: QMW
Renormalization Group Flows on Line Defects
Zohar Komargodski
(Simons Center)
Abstract:
We will review the subject of line defects in d-dimensional Conformal Field Theories (CFTs). We discuss an exact formula governing the renormalization group flow on line defects and consider some examples involving line defects in 2,3, and 4 space-time dimensions.
–––––––– Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant. The link will be emailed on Tuesday.
We will review the subject of line defects in d-dimensional Conformal Field Theories (CFTs). We discuss an exact formula governing the renormalization group flow on line defects and consider some examples involving line defects in 2,3, and 4 space-time dimensions.
–––––––– Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant. The link will be emailed on Tuesday.
Posted by: andrea