8 results on '"Melville, Scott A."'
Search Results
2. On the time evolution of cosmological correlators
- Author
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Céspedes, Sebastián, Davis, Anne-Christine, and Melville, Scott
- Published
- 2021
- Full Text
- View/download PDF
3. Improved positivity bounds and massive gravity
- Author
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de Rham, Claudia, Melville, Scott, and Tolley, Andrew J.
- Published
- 2018
- Full Text
- View/download PDF
4. Generalised matter couplings in massive bigravity
- Author
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Melville, Scott and Noller, Johannes
- Published
- 2016
- Full Text
- View/download PDF
5. Cosmological Cutting Rules
- Author
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Melville, Scott and Pajer, Enrico
- Subjects
Effective Field Theories ,Regular Article - Theoretical Physics ,16. Peace & justice ,Classical Theories of Gravity - Abstract
Primordial perturbations in our universe are believed to have a quantum origin, and can be described by the wavefunction of the universe (or equivalently, cosmological correlators). It follows that these observables must carry the imprint of the founding principle of quantum mechanics: unitary time evolution. Indeed, it was recently discovered that unitarity implies an infinite set of relations among tree-level wavefunction coefficients, dubbed the Cosmological Optical Theorem. Here, we show that unitarity leads to a systematic set of “Cosmological Cutting Rules” which constrain wavefunction coefficients for any number of fields and to any loop order. These rules fix the discontinuity of an n-loop diagram in terms of lower-loop diagrams and the discontinuity of tree-level diagrams in terms of tree-level diagrams with fewer external fields. Our results apply with remarkable generality, namely for arbitrary interactions of fields of any mass and any spin with a Bunch-Davies vacuum around a very general class of FLRW spacetimes. As an application, we show how one-loop corrections in the Effective Field Theory of inflation are fixed by tree-level calculations and discuss related perturbative unitarity bounds. These findings greatly extend the potential of using unitarity to bootstrap cosmological observables and to restrict the space of consistent effective field theories on curved spacetimes.
6. Cosmological Cutting Rules
- Author
-
Melville, Scott and Pajer, Enrico
- Subjects
Effective Field Theories ,Regular Article - Theoretical Physics ,16. Peace & justice ,Classical Theories of Gravity - Abstract
Primordial perturbations in our universe are believed to have a quantum origin, and can be described by the wavefunction of the universe (or equivalently, cosmological correlators). It follows that these observables must carry the imprint of the founding principle of quantum mechanics: unitary time evolution. Indeed, it was recently discovered that unitarity implies an infinite set of relations among tree-level wavefunction coefficients, dubbed the Cosmological Optical Theorem. Here, we show that unitarity leads to a systematic set of “Cosmological Cutting Rules” which constrain wavefunction coefficients for any number of fields and to any loop order. These rules fix the discontinuity of an n-loop diagram in terms of lower-loop diagrams and the discontinuity of tree-level diagrams in terms of tree-level diagrams with fewer external fields. Our results apply with remarkable generality, namely for arbitrary interactions of fields of any mass and any spin with a Bunch-Davies vacuum around a very general class of FLRW spacetimes. As an application, we show how one-loop corrections in the Effective Field Theory of inflation are fixed by tree-level calculations and discuss related perturbative unitarity bounds. These findings greatly extend the potential of using unitarity to bootstrap cosmological observables and to restrict the space of consistent effective field theories on curved spacetimes.
7. Cosmological Cutting Rules
- Author
-
Enrico Pajer, Scott Melville, Melville, Scott [0000-0003-3516-856X], and Apollo - University of Cambridge Repository
- Subjects
High Energy Physics - Theory ,Nuclear and High Energy Physics ,Infinite set ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Field (physics) ,media_common.quotation_subject ,FOS: Physical sciences ,QC770-798 ,General Relativity and Quantum Cosmology (gr-qc) ,01 natural sciences ,General Relativity and Quantum Cosmology ,symbols.namesake ,Theoretical physics ,Friedmann–Lemaître–Robertson–Walker metric ,Nuclear and particle physics. Atomic energy. Radioactivity ,0103 physical sciences ,Effective field theory ,010306 general physics ,media_common ,Inflation (cosmology) ,Physics ,Unitarity ,010308 nuclear & particles physics ,Observable ,Effective Field Theories ,16. Peace & justice ,Universe ,High Energy Physics - Theory (hep-th) ,symbols ,Regular Article - Theoretical Physics ,Classical Theories of Gravity ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Primordial perturbations in our universe are believed to have a quantum origin, and can be described by the wavefunction of the universe (or equivalently, cosmological correlators). It follows that these observables must carry the imprint of the founding principle of quantum mechanics: unitary time evolution. Indeed, it was recently discovered that unitarity implies an infinite set of relations among tree-level wavefunction coefficients, dubbed the Cosmological Optical Theorem. Here, we show that unitarity leads to a systematic set of "Cosmological Cutting Rules" which constrain wavefunction coefficients for any number of fields and to any loop order. These rules fix the discontinuity of an n-loop diagram in terms of lower-loop diagrams and the discontinuity of tree-level diagrams in terms of tree-level diagrams with fewer external fields. Our results apply with remarkable generality, namely for arbitrary interactions of fields of any mass and any spin with a Bunch-Davies vacuum around a very general class of FLRW spacetimes. As an application, we show how one-loop corrections in the Effective Field Theory of inflation are fixed by tree-level calculations and discuss related perturbative unitarity bounds. These findings greatly extend the potential of using unitarity to bootstrap cosmological observables and to restrict the space of consistent effective field theories on curved spacetimes., Comment: 48+11 pages, 5 figures
- Published
- 2021
- Full Text
- View/download PDF
8. On the time evolution of cosmological correlators
- Author
-
Scott Melville, Sebastian Cespedes, Anne-Christine Davis, Melville, Scott [0000-0003-3516-856X], Apollo - University of Cambridge Repository, Melville, S [0000-0003-3516-856X], and UAM. Departamento de Física Teórica
- Subjects
High Energy Physics - Theory ,Nuclear and High Energy Physics ,Scalar (mathematics) ,Boundary (topology) ,FOS: Physical sciences ,General Relativity and Quantum Cosmology (gr-qc) ,Supergravity ,01 natural sciences ,General Relativity and Quantum Cosmology ,De Sitter universe ,0103 physical sciences ,lcsh:Nuclear and particle physics. Atomic energy. Radioactivity ,010306 general physics ,Mathematical physics ,Inflation (cosmology) ,Physics ,Unitarity ,010308 nuclear & particles physics ,Space-Time Symmetries ,Equations of motion ,Física ,Effective Field Theories ,Inflation ,Cosmos ,High Energy Physics - Theory (hep-th) ,lcsh:QC770-798 ,Schrödinger picture ,Regular Article - Theoretical Physics ,Scalar field ,Classical Theories of Gravity - Abstract
Developing our understanding of how correlations evolve during inflation is crucial if we are to extract information about the early Universe from our late-time observables. To that end, we revisit the time evolution of scalar field correlators on de Sitter spacetime in the Schrodinger picture. By direct manipulation of the Schrodinger equation, we write down simple "equations of motion" for the coefficients which determine the wavefunction. Rather than specify a particular interaction Hamiltonian, we assume only very basic properties (unitarity, de Sitter invariance and locality) to derive general consequences for the wavefunction's evolution. In particular, we identify a number of "constants of motion": properties of the initial state which are conserved by any unitary dynamics. We further constrain the time evolution by deriving constraints from the de Sitter isometries and show that these reduce to the familiar conformal Ward identities at late times. Finally, we show how the evolution of a state from the conformal boundary into the bulk can be described via a number of "transfer functions" which are analytic outside the horizon for any local interaction. These objects exhibit divergences for particular values of the scalar mass, and we show how such divergences can be removed by a renormalisation of the boundary wavefunction - this is equivalent to performing a "Boundary Operator Expansion" which expresses the bulk operators in terms of regulated boundary operators. Altogether, this improved understanding of the wavefunction in the bulk of de Sitter complements recent advances from a purely boundary perspective, and reveals new structure in cosmological correlators., Comment: 63 pages + 2 appendices, 4 figures
- Published
- 2020
- Full Text
- View/download PDF
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