Triangle Seminars
Tuesday, 27 May 2025
Lonti: Superstring Perturbation Theory (1/4)
Ashoke Sen
(ICTS, Bangalore)
Abstract:
Please register at https://forms.gle/pHFLVU2XeZu39gzVA
The world-sheet CFT for bosonic string theory, matter and ghost system, BRST charge, physical state condition
Definition of higher genus Riemann surfaces, defining CFT correlations on higher genus Riemann surfaces, bosonic string amplitudes at any loop order
Heterotic and superstring theory, world-sheet CFT of matter and ghosts, picture number and picture changing operator, superstring amplitude at any loop order
Vertical integration and removal of spurious divergences
Please register at https://forms.gle/pHFLVU2XeZu39gzVA
The world-sheet CFT for bosonic string theory, matter and ghost system, BRST charge, physical state condition
Definition of higher genus Riemann surfaces, defining CFT correlations on higher genus Riemann surfaces, bosonic string amplitudes at any loop order
Heterotic and superstring theory, world-sheet CFT of matter and ghosts, picture number and picture changing operator, superstring amplitude at any loop order
Vertical integration and removal of spurious divergences
Posted by: andrea
Uplifting Massive Graphs from Minkowski to de Sitter
📍 London
Sadra Jazayeri
(Imperial College London)
Abstract:
Identifying useful flat-space limits of cosmological correlators defined on the future boundary of de Sitter space is challenging due to their inherent scale invariance. In this talk, I present a massive flat-space limit in which cosmological correlators arising from the exchange of heavy fields can be expressed in terms of massive Feynman diagrams in Minkowski space. As a phenomenological application, I use this limit to compute the imprints of massive particles during inflation on primordial non-Gaussianity. These results offer new channels for discovering inflation-era particles with the next generation of CMB and large-scale structure surveys, such as Simons Observatory and SPHEREx.
Identifying useful flat-space limits of cosmological correlators defined on the future boundary of de Sitter space is challenging due to their inherent scale invariance. In this talk, I present a massive flat-space limit in which cosmological correlators arising from the exchange of heavy fields can be expressed in terms of massive Feynman diagrams in Minkowski space. As a phenomenological application, I use this limit to compute the imprints of massive particles during inflation on primordial non-Gaussianity. These results offer new channels for discovering inflation-era particles with the next generation of CMB and large-scale structure surveys, such as Simons Observatory and SPHEREx.
Posted by: QMUL2
Thursday, 29 May 2025
Dialogues on AI and Science
Michael Douglas
(Harvard)
Abstract:
informal seminar and dialogues with Mike in our historical rooms.
informal seminar and dialogues with Mike in our historical rooms.
Posted by: oxford
de Sitter Space as a coherent state
📍 London
Radu Tatar
(university of Liverpool)
Abstract:
We consider an M theory/string theory approach to support the fact that a four-dimensional effective field theory description with de Sitter isometries can exist if de Sitter space is realised as a coherent state.
We consider an M theory/string theory approach to support the fact that a four-dimensional effective field theory description with de Sitter isometries can exist if de Sitter space is realised as a coherent state.
Posted by: QMW
Cosmological correlators in gravitationally constrained de Sitter states
📍 London
Tuneer Chakraborty
(Tata Institute of Fundamental Research (TIFR), Mumbai)
Abstract:
We study perturbative cosmological correlators in wavefunctionals which solve the Wheeler-DeWitt equation in asymptotically de Sitter spacetimes and were constructed in arxiv:2303.16315. Even in the G_N -> 0 limit, it is necessary to impose the gravitational Gauss law, which forces states to be de Sitter invariant. We set up Feynman rules for computing cosmological correlators in such states. We enumerate some necessary (but not sufficient) conditions that must be imposed on states and observables to avoid group-volume divergences. We provide sample computations to show that such cosmological correlators can be nontrivial even when the Hartle-Hawking wavefunction is Gaussian. We show that, in the presence of a heavy background state, it is possible to construct a class of state-dependent relational observables that approximate correlators in the Hartle-Hawking state.
We study perturbative cosmological correlators in wavefunctionals which solve the Wheeler-DeWitt equation in asymptotically de Sitter spacetimes and were constructed in arxiv:2303.16315. Even in the G_N -> 0 limit, it is necessary to impose the gravitational Gauss law, which forces states to be de Sitter invariant. We set up Feynman rules for computing cosmological correlators in such states. We enumerate some necessary (but not sufficient) conditions that must be imposed on states and observables to avoid group-volume divergences. We provide sample computations to show that such cosmological correlators can be nontrivial even when the Hartle-Hawking wavefunction is Gaussian. We show that, in the presence of a heavy background state, it is possible to construct a class of state-dependent relational observables that approximate correlators in the Hartle-Hawking state.
Posted by: QMW
Friday, 30 May 2025
Lonti: Superstring Perturbation Theory (2/4)
Ashoke Sen
(ICTS, Bangalore)
Abstract:
Please register at https://forms.gle/pHFLVU2XeZu39gzVA
The world-sheet CFT for bosonic string theory, matter and ghost system, BRST charge, physical state condition
Definition of higher genus Riemann surfaces, defining CFT correlations on higher genus Riemann surfaces, bosonic string amplitudes at any loop order
Heterotic and superstring theory, world-sheet CFT of matter and ghosts, picture number and picture changing operator, superstring amplitude at any loop order
Vertical integration and removal of spurious divergences
Please register at https://forms.gle/pHFLVU2XeZu39gzVA
The world-sheet CFT for bosonic string theory, matter and ghost system, BRST charge, physical state condition
Definition of higher genus Riemann surfaces, defining CFT correlations on higher genus Riemann surfaces, bosonic string amplitudes at any loop order
Heterotic and superstring theory, world-sheet CFT of matter and ghosts, picture number and picture changing operator, superstring amplitude at any loop order
Vertical integration and removal of spurious divergences
Posted by: andrea