scholarly journals Tree-level scattering amplitude in de Sitter space

2004 ◽  
Vol 68 (1) ◽  
pp. 15-18 ◽  
Author(s):  
S Rouhani ◽  
M. V Takook
Keyword(s):  
Scattering Amplitude ◽  
De Sitter Space ◽  
Tree Level ◽  
De Sitter

scholarly journals LECTURE NOTES ON INTERACTING QUANTUM FIELDS IN DE SITTER SPACE

2014 ◽  
Vol 23 (01) ◽  
pp. 1430001 ◽  
Author(s):  
E. T. AKHMEDOV
Keyword(s):  
De Sitter Space ◽  
The Self ◽  
Field Theories ◽  
Tree Level ◽  
Main Concern ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Quantum Fields ◽  
De Sitter ◽  
Invariant States

We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the self-interacting massive real scalar, minimally coupled to the gravity background. Nonconformal quantum field theories (QFTs) in dS space show very special infrared behavior, which is not shared by quantum fields neither in flat nor in anti-dS space: in dS space loops are not suppressed in comparison with tree level contributions because there are strong infrared corrections. That is true even for massive fields. Our main concern is the interrelation between these infrared effects, the invariance of the QFT under the dS isometry and the (in)stability of dS invariant states (and of dS space itself) under nonsymmetric perturbations.

scholarly journals The inflationary wavefunction from analyticity and factorization

2021 ◽  
Vol 2021 (12) ◽  
pp. 018
Author(s):  
David Meltzer
Keyword(s):  
Analytic Continuation ◽  
De Sitter Space ◽  
Conformal Group ◽  
Tree Level ◽  
Late Time ◽  
De Sitter ◽  
Scale Invariant ◽  
Arbitrary Mass ◽  
Lower Point ◽  
Finite Sum

Abstract We study the analytic properties of tree-level wavefunction coefficients in quasi-de Sitter space. We focus on theories which spontaneously break dS boost symmetries and can produce significant non-Gaussianities. The corresponding inflationary correlators are (approximately) scale invariant, but are not invariant under the full conformal group. We derive cutting rules and dispersion formulas for the late-time wavefunction coefficients by using factorization and analyticity properties of the dS bulk-to-bulk propagator. This gives a unitarity method which is valid at tree-level for general n-point functions and for fields of arbitrary mass. Using the cutting rules and dispersion formulas, we are able to compute n-point functions by gluing together lower-point functions. As an application, we study general four-point, scalar exchange diagrams in the EFT of inflation. We show that exchange diagrams constructed from boost-breaking interactions can be written as a finite sum over residues. Finally, we explain how the dS identities used in this work are related by analytic continuation to analogous identities in Anti-de Sitter space.

scholarly journals REDUCTION FORMALISM FOR DIRAC FERMIONS ON DE SITTER SPACE–TIME

2008 ◽  
Vol 23 (07) ◽  
pp. 1075-1087 ◽  
Author(s):  
COSMIN CRUCEAN ◽  
RADU RACOCEANU
Keyword(s):  
Perturbation Theory ◽  
Dirac Equation ◽  
Exact Solutions ◽  
Scattering Amplitude ◽  
De Sitter Space ◽  
Space Time ◽  
Green Functions ◽  
Dirac Fermions ◽  
De Sitter

The reduction formulas for Dirac fermions is derived using the exact solutions of free Dirac equation on de Sitter space–time. In the framework of the perturbation theory one studies the Green functions and derives the scattering amplitude in the first orders of perturbation theory.

Tree-level scattering amplitudes in de Sitter space diverge

1987 ◽  
Vol 197 (3) ◽  
pp. 373-378 ◽  
Author(s):  
E.G. Floratos ◽  
J. Iliopoulos ◽  
T.N. Tomaras
Keyword(s):  
Scattering Amplitudes ◽  
De Sitter Space ◽  
Tree Level ◽  
De Sitter

HELICITY CONSERVATION IN COULOMB SCATTERING OF THE DIRAC FIELD IN THE EXPANDING DE SITTER SPACE

2011 ◽  
Vol 26 (24) ◽  
pp. 4217-4238 ◽  
Author(s):  
NISTOR NICOLAEVICI
Keyword(s):  
Scattering Amplitude ◽  
Scattering Problem ◽  
Classical Case ◽  
De Sitter Space ◽  
Complete Agreement ◽  
Dirac Field ◽  
Polarization Angle ◽  
De Sitter ◽  
Helicity Conservation ◽  
Telegdi Equation

We comment on a previous calculation1 for the scattering amplitude for the Dirac field in an external Coulomb potential in the expanding de Sitter space. The result implies that for initial and final fermion states with identical momenta |pi|=|pf| the helicity of the particle is conserved. We make a classical analysis of the scattering problem in the small scattering angle approximation using the Bargmann–Michel–Telegdi equation and show that helicity conservation also manifests in the classical case. We also show that in Minkowski space there is a complete agreement between the classical and quantum polarization angle of the scattered particle.

scholarly journals On the consistency of (partially-)massless matter couplings in de Sitter space

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Charlotte Sleight ◽  
Massimo Taronna
Keyword(s):  
Gauge Invariance ◽  
Point Processes ◽  
Scalar Fields ◽  
Flat Space ◽  
De Sitter Space ◽  
Tree Level ◽  
De Sitter ◽  
Scalar Matter ◽  
Carry Over ◽  
Massless Fields

Abstract We study the consistency of the cubic couplings of a (partially-)massless spinning field to two scalars in (d + 1)-dimensional de Sitter space. Gauge invariance of observables with external (partially)-massless spinning fields translates into Ward-Takahashi identities on the boundary. Using the Mellin-Barnes representation for boundary correlators in momentum space, we give a systematic study of Ward-Takahashi identities for tree-level 3- and 4-point processes involving a single external (partially-)massless field of arbitrary integer spin-J. 3-point Ward-Takahashi identities constrain the mass of the scalar fields to which a (partially-)massless spin-J field can couple. 4-point Ward-Takahashi identities then constrain the corresponding cubic couplings. For massless spinning fields, we show that Weinberg’s flat space results carry over to (d+1)-dimensional de Sitter space: for spins J = 1, 2 gauge-invariance implies charge-conservation and the equivalence principle while, assuming locality, higher-spins J > 2 cannot couple consistently to scalar matter. This result also applies to anti-de Sitter space. For partially-massless fields, restricting for simplicity to those of depth-2, we show that there is no consistent coupling to scalar matter in local theories. Along the way we also give a detailed account of how contact amplitudes with and without derivatives are represented in the Mellin-Barnes representation. Various new explicit expressions for 3- and 4-point functions involving (partially-)massless fields and conformally coupled scalars in dS4 are given.

scholarly journals Gravitational turbulent instability of anti-de Sitter space

2012 ◽  
Vol 29 (19) ◽  
pp. 194002 ◽  
Author(s):  
Óscar J C Dias ◽  
Gary T Horowitz ◽  
Jorge E Santos
Keyword(s):  
De Sitter Space ◽  
De Sitter

scholarly journals Open quantum entanglement: a study of two atomic system in static patch of de Sitter space

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Samim Akhtar ◽  
Sayantan Choudhury ◽  
Satyaki Chowdhury ◽  
Debopam Goswami ◽  
Sudhakar Panda ◽  
...  
Keyword(s):  
Scalar Field ◽  
Density Matrix ◽  
Master Equation ◽  
Quantum Entanglement ◽  
De Sitter Space ◽  
Thermal Bath ◽  
Massless Scalar Field ◽  
De Sitter ◽  
Open Quantum ◽  
Non Locality

Abstract In this work, our prime objective is to study non-locality and long range effect of two body correlation using quantum entanglement from various information theoretic measure in the static patch of de Sitter space using a two body Open Quantum System (OQS). The OQS is described by a system of two entangled atoms, surrounded by a thermal bath, which is modelled by a massless probe scalar field. Firstly, we partially trace over the bath field and construct the Gorini Kossakowski Sudarshan Lindblad (GSKL) master equation, which describes the time evolution of the reduced subsystem density matrix. This GSKL master equation is characterized by two components, these are-Spin chain interaction Hamiltonian and the Lindbladian. To fix the form of both of them, we compute the Wightman functions for probe massless scalar field. Using this result alongwith the large time equilibrium behaviour we obtain the analytical solution for reduced density matrix. Further using this solution we evaluate various entanglement measures, namely Von-Neumann entropy, R$$e'$$e′nyi entropy, logarithmic negativity, entanglement of formation, concurrence and quantum discord for the two atomic subsystem on the static patch of De-Sitter space. Finally, we have studied violation of Bell-CHSH inequality, which is the key ingredient to study non-locality in primordial cosmology.

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