Triangle Seminars
Tuesday, 27 Apr 2021
Topics in inflationary cosmology: reheating, gauge fields and gravitational waves
Kaloian Lozanov
(University of Illinois)
Abstract:
We will review our current understanding of reheating after inflation, including various aspects of the linear and nonlinear dynamics of the inflaton field, such as parametric resonance, the generation of metric perturbations and the effects of the nonlinear evolution on the post-inflationary expansion history. We will also review the recent progress in the understanding of the non-perturbative dynamics of dark vector fields during reheating and whether they can play the role of dark matter in the late universe. Finally, we will discuss phenomenologically interesting models of gauge fields during inflation which can give rise to detectable gravitational wave signatures.
[please email a.held@imperial.ac.uk for zoom link or password]
We will review our current understanding of reheating after inflation, including various aspects of the linear and nonlinear dynamics of the inflaton field, such as parametric resonance, the generation of metric perturbations and the effects of the nonlinear evolution on the post-inflationary expansion history. We will also review the recent progress in the understanding of the non-perturbative dynamics of dark vector fields during reheating and whether they can play the role of dark matter in the late universe. Finally, we will discuss phenomenologically interesting models of gauge fields during inflation which can give rise to detectable gravitational wave signatures.
[please email a.held@imperial.ac.uk for zoom link or password]
Posted by: IC
Wednesday, 28 Apr 2021
Higher-derivative Supergravity and AdS4 Holography
📍 London
Valentin Reys
(Leuven U.)
Abstract:
This talk will discuss higher-derivative corrections to four-dimensional gauged supergravity and their holographic implications. After briefly reviewing the construction of N=2 supersymmetric higher-derivative invariants, I will introduce a four-derivative action parameterized by two real constants. In this theory, one can show that the two-derivative solutions are not modified by the higher-derivative corrections. This fact has important consequences for the regularized on-shell action, as well as for the thermodynamics of black hole solutions. Moreover, in the context of AdS4/CFT3 holography, I will explain how our results lead to an explicit expression for subleading corrections in the large-N expansion of supersymmetric partition functions of a large class of dual field theories arising from M2 and M5 branes.
[please email alejandro.cabo_bizet@kcl.ac.uk for the zoom link]
This talk will discuss higher-derivative corrections to four-dimensional gauged supergravity and their holographic implications. After briefly reviewing the construction of N=2 supersymmetric higher-derivative invariants, I will introduce a four-derivative action parameterized by two real constants. In this theory, one can show that the two-derivative solutions are not modified by the higher-derivative corrections. This fact has important consequences for the regularized on-shell action, as well as for the thermodynamics of black hole solutions. Moreover, in the context of AdS4/CFT3 holography, I will explain how our results lead to an explicit expression for subleading corrections in the large-N expansion of supersymmetric partition functions of a large class of dual field theories arising from M2 and M5 branes.
[please email alejandro.cabo_bizet@kcl.ac.uk for the zoom link]
Posted by: andrea
Kaluza-Klein spectrometer from exceptional field theory
Henning Samtleben
(ENS Lyon)
Abstract:
I review new tools for the computation of Kaluza-Klein mass spectra associated with compactifications around various background geometries relevant for string theory. This includes geometries with little to no remaining symmetries, hardly accessible to standard methods. The new tools build on exceptional field theory, the duality covariant formulation of supergravity. Among the applications I discuss the stability of several non-supersymmetric AdS4 and AdS3 vacua, as well as Kaluza-Klein spectra around type IIB S-fold backgrounds.
Zoom:
https://zoom.us/j/98264204601?pwd=Z0xYdG1vVlEwU1M1bDhVcXQvWURPQT09
Meeting ID: 982 6420 4601
Passcode: 196883
I review new tools for the computation of Kaluza-Klein mass spectra associated with compactifications around various background geometries relevant for string theory. This includes geometries with little to no remaining symmetries, hardly accessible to standard methods. The new tools build on exceptional field theory, the duality covariant formulation of supergravity. Among the applications I discuss the stability of several non-supersymmetric AdS4 and AdS3 vacua, as well as Kaluza-Klein spectra around type IIB S-fold backgrounds.
Zoom:
https://zoom.us/j/98264204601?pwd=Z0xYdG1vVlEwU1M1bDhVcXQvWURPQT09
Meeting ID: 982 6420 4601
Passcode: 196883
Posted by: IC
Thursday, 29 Apr 2021
The Topology of Data: from String Theory to Cosmology to Phases of Matter
Gary Shiu
(Wisconsin U., Madison)
Abstract:
Abstract: We are faced with an explosion of data in many areas of physics, but very so often, it is not the size but the complexity of the data that makes extracting physics from big datasets challenging. As I will discuss in this talk, data has shape and the shape of data encodes the underlying physics. Persistent homology is a tool in computational topology developed for quantifying the shape of data. I will discuss three applications of topological data analysis: 1) identifying structure of the string landscape, 2) constraining cosmological parameters from CMB measurements and large scale structures data, and 3) detecting and classifying phases of matter. Persistent homology condenses these datasets into their most relevant (and interpretable) features, so that simple statistical pipelines are sufficient in these contexts. This suggests that TDA can be used in conjunction with machine learning algorithms and improves their architecture. [for zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]
Abstract: We are faced with an explosion of data in many areas of physics, but very so often, it is not the size but the complexity of the data that makes extracting physics from big datasets challenging. As I will discuss in this talk, data has shape and the shape of data encodes the underlying physics. Persistent homology is a tool in computational topology developed for quantifying the shape of data. I will discuss three applications of topological data analysis: 1) identifying structure of the string landscape, 2) constraining cosmological parameters from CMB measurements and large scale structures data, and 3) detecting and classifying phases of matter. Persistent homology condenses these datasets into their most relevant (and interpretable) features, so that simple statistical pipelines are sufficient in these contexts. This suggests that TDA can be used in conjunction with machine learning algorithms and improves their architecture. [for zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]
Posted by: QMW
Scattering Amplitudes Near the Origins: Localization and Globalization
Benjamin Basso
(ENS Paris)
Abstract:
I will talk about the behaviour of gluon scattering amplitudes in planar N=4 SYM near kinematical corners coined Origins where maximally-helicity-violating amplitudes are expected to be exactly Gaussian in the logs of the cross ratios and exactly predictable. In part 1, I will recall how much is known about this behaviour for the 6-gluon amplitude and interpret the result as a sort of quantum area convoluting the minimal surface TBA data with an effective coupling constant, known as the tilted cusp anomalous dimension. In part 2, I will present a generalization to any number of gluons and explore (some bit of) the emerging parterre of Origins. If time permits, I will discuss applications to scattering amplitudes in the null limit where all two-particle Mandelstam vanish simultaneously. The talk is based on a work in progress with Lance Dixon, Yu-Ting Liu and Georgios Papathanasiou. –– Part of the London Integrability Journal Club. If you are a new participant please register at integrability-london.weebly.com. The link will be emailed.
I will talk about the behaviour of gluon scattering amplitudes in planar N=4 SYM near kinematical corners coined Origins where maximally-helicity-violating amplitudes are expected to be exactly Gaussian in the logs of the cross ratios and exactly predictable. In part 1, I will recall how much is known about this behaviour for the 6-gluon amplitude and interpret the result as a sort of quantum area convoluting the minimal surface TBA data with an effective coupling constant, known as the tilted cusp anomalous dimension. In part 2, I will present a generalization to any number of gluons and explore (some bit of) the emerging parterre of Origins. If time permits, I will discuss applications to scattering amplitudes in the null limit where all two-particle Mandelstam vanish simultaneously. The talk is based on a work in progress with Lance Dixon, Yu-Ting Liu and Georgios Papathanasiou. –– Part of the London Integrability Journal Club. If you are a new participant please register at integrability-london.weebly.com. The link will be emailed.
Posted by: andrea