Article
Astronomy & Astrophysics
Enrico Parisini, Kostas Skenderis, Benjamin Withers
Summary: We generalize the embedding space formalism to conformal field theories (CFTs) on nontrivial states and curved backgrounds using the ambient metric of Fefferman and Graham. The construction of CFT n-point functions in these settings is based on appropriate geometric invariants of the ambient space. Exact agreement with holographic computations and expectations from thermal operator product expansions (OPEs) is found for two-point functions of thermal CFT, and the method is also applied to CFTs on squashed spheres with no prior results available, demonstrating its utility.
Article
Physics, Nuclear
Gary Nash
Summary: This article discusses how the multi-spin Klein-Gordon equation of quantum field theory can be adapted to curved space-time, focusing on spins 0, 1, and 1/2 particles. By establishing connections between spin-1 KG equation, spin-0 KG equation, Dirac spinor KG equation, and the energy-momentum tensor in Modified General Relativity, the article explores the unification of various theories. Additionally, the importance of instantaneous information transmission, entanglement concept in a Lorentzian formalism is highlighted.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2021)
Article
Astronomy & Astrophysics
Golam Mortuza Hossain, Susobhan Mandal
Summary: In the study of spherical degenerate stars, effects of general relativity and gravitational time dilation are crucial and ignoring them can lead to significantly underestimating the mass limits of these compact stars.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Benito A. Juarez-Aubry, Bernard S. Kay, Tonatiuh Miramontes, Daniel Sudarskya
Summary: Semiclassical gravity is a theory that combines classical Einstein tensor with quantum matter fields in a quantum state. The article explores two issues, focusing on the Klein Gordon equation as the model quantum field theory. The first issue deals with finding a suitable initial value formulation for the theory, taking into account the surface Hadamard condition and the complications arising from geodesic distances. The second issue discusses the combination of semiclassical gravity with theories of spontaneous quantum state collapse, proposing a jump rule for the metric and/or extrinsic curvature to ensure unique time evolution. The simpler cases of semiclassical scalars model and semiclassical electrodynamics are also studied.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
A. P. C. M. Lima, G. Alencar, R. R. Landim
Summary: The study demonstrates that in a static weak gravitational background, the Casimir Energy for a real massless scalar field obeying Dirichlet boundary conditions on rectangular plates remains unchanged from its flat space-time value at least to second order in the gravitational parameters. By considering a rather general class of backgrounds, the result provides further generality and consistency testing for previous work.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Stavros Mougiakakos, Pierre Vanhove
Summary: The study derives the static Schwarzschild-Tangherlini metric by extracting classical contributions from the multiloop vertex functions of a graviton emitted from a massive scalar field. By computing scattering amplitudes, an expansion of the metric up to the fourth post-Minkowskian order in four, five, and six dimensions is explicitly derived, with the introduction of higher-derivative nonminimal couplings to cancel ultraviolet divergences. The standard Schwarzschild-Tangherlini metric is recovered through an appropriate coordinate transformation induced from the de Donder gauge condition.
Article
Astronomy & Astrophysics
Eleni-Alexandra Kontou, Ken D. Olum
Summary: This paper demonstrates that eternal inflation is possible even when energy conditions are obeyed. While energy conditions restrict the evolution of any single quantum state, the process of eternal inflation involves selecting a subsector of the previous state, avoiding violation of the conditions.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Golam Mortuza Hossain, Susobhan Mandal
Summary: We compute the equation of state for degenerate fermions in the curved spacetime of a slowly rotating axially symmetric star. Our results show that the equation of state in this curved spacetime depends on the gravitational time dilation and dragging of inertial frames, different from a globally flat spacetime. The effect of gravitational time dilation significantly enhances the maximum mass limit of a degenerate neutron star, while the enhancement due to the frame-dragging effect is extremely small. The frame-dragging effect is crucial for computing the angular momentum of the star, which is also significantly enhanced by the usage of curved spacetime in computing the equation of state.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Review
Physics, Multidisciplinary
Andreas Brandhuber, Jan Plefka, Gabriele Travaglini
Summary: Scattering amplitudes are important concepts and techniques in quantum field theory. This chapter introduces foundational concepts and techniques, aiming to make readers understand and apply this knowledge.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Review
Multidisciplinary Sciences
Antonio Capolupo, Aniello Quaranta, Raoul Serao
Summary: This article provides an extensive review on the quantum field theory of particle mixing in curved spacetime. It discusses the rich mathematical structure of the theory for fermions and bosons, arising from the interplay of curved space quantization and field mixing, and explores its phenomenological implications. Fermionic and bosonic oscillation formulae for arbitrary globally hyperbolic spacetimes are derived, and transition probabilities are computed on metrics of cosmological and astrophysical interest. The deviations from flat space probabilities are demonstrated through numerical analyses. The condensate structure of the flavor vacuum of mixed fermions is studied, considering its potential role as a dark matter component in a cosmological context.
Article
Physics, Mathematical
Daniel Harlow, Hirosi Ooguri
Summary: This paper refines and establishes a set of old conjectures about symmetries in quantum gravity using the AdS/CFT correspondence. It shows the absence of bulk global symmetries in AdS/CFT and discusses how long-range bulk gauge symmetries lead to global boundary symmetries. The results are extended to higher-form symmetries and the weak gravity conjecture is applied to more general gauge groups.
COMMUNICATIONS IN MATHEMATICAL PHYSICS
(2021)
Article
Astronomy & Astrophysics
J. R. Espinosa, J. -f. Fortin
Summary: The tunneling potential method is an attractive alternative to the Euclidean bounce method for calculating the action of vacuum decay. This paper extends the formalism to general spacetime dimension d > 2 and uses it to provide simple proofs of several results. It shows that gravity or higher barriers increase the lifetime of Minkowski or Anti de Sitter false vacua and presents a clear picture of the gravitational quenching of vacuum decay. The paper also derives the thin-wall limit of the action, demonstrates how detailed balance for dS to dS transitions works in the new formalism, and outlines a method for obtaining analytical solutions for vacuum decay potentials.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Particles & Fields
Zi-Chao Lin, Hao Yu, Yu-Xiao Liu
Summary: In this paper, the universe is considered as a codimension-2 brane in a noncompact six-dimensional AdS spacetime. The gravitational horizon radius on the brane under the low energy approximation is derived, indicating the effect of extra dimensions on gravitational waves. The time delay between a GW signal and an EM wave signal is studied in the low-redshift limit, giving an upper limit for the AdS(6) radius as l(2) ? 3.84 Mpc(2) based on joint observations of GW170817 and GRB 170817A. For high-redshift sources, a stronger constraint on the AdS6 radius is required to detect the EM counterpart of a GW event within a reasonable observation time. Our research suggests that the AdS6 radius should satisfy l(2) ? 0.02 Mpc(2) for DECIGO and BBO.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Adria Delhom, T. Mariz, J. R. Nascimento, Gonzalo J. Olmo, A. Yu. Petrov, Paulo J. Porfirio
Summary: The metric-affine bumblebee model with fermionic matter minimally coupled to the connection is analyzed. The model is shown to have an Einstein frame representation with a non-minimal Dirac action for the matter sector. This non-minimal terms involve unconventional couplings between the bumblebee and fermion field. The coefficients for Lorentz/CPT violation in all orders of the non-minimal coupling are identified by rewriting the quadratic fermion action in the Einstein frame based on 16 Dirac matrices.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Bogeun Gwak
Summary: We investigate the weak cosmic censorship conjecture in extremal and near-extremal Kerr-Newman-(anti-)de Sitter black holes by scattering a massive scalar field with charge. While the black hole may exceed its extremal condition due to changes in its state caused by the scattering, it cannot be overcharged or overspun. The weak cosmic censorship conjecture is valid for any scalar field boundary conditions and is thermodynamically preferred for this scattering process.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Cedric Deffayet, Gilles Esposito-Farese, Daniele A. Steer
Article
Physics, Particles & Fields
Nicolas Boulanger, Cedric Deffayet, Sebastian Garcia-Saenz, Lucas Traina
JOURNAL OF HIGH ENERGY PHYSICS
(2018)
Article
Astronomy & Astrophysics
Cedric Deffayet, Ted Jacobson
CLASSICAL AND QUANTUM GRAVITY
(2012)
Article
Astronomy & Astrophysics
Cedric Deffayet, Daniele A. Steer
CLASSICAL AND QUANTUM GRAVITY
(2013)
Editorial Material
Astronomy & Astrophysics
Eugeny Babichev, Cedric Deffayet
CLASSICAL AND QUANTUM GRAVITY
(2013)
Article
Astronomy & Astrophysics
C. Deffayet, S. Randjbar-Daemi
Article
Astronomy & Astrophysics
Cedric Deffayet, Gilles Esposito-Farese, Richard P. Woodard
Article
Astronomy & Astrophysics
Maximo Banados, Cedric Deffayet, Miguel Pino
Article
Physics, Multidisciplinary
Cedric Deffayet, Shinji Mukohyama, Alexander Vikman
Summary: In this study, we introduce a class of mechanical models with a canonical degree of freedom interacting with a ghost. Analytically, we prove that the classical motion of the system is completely stable for all initial conditions, contradicting the common belief that systems with negative kinetic terms are unstable.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Cedric Deffayet, Francois Larrouturou
Summary: Domain walls, or kinks, can be constructed in simple scalar theories without potential. These theories, belonging to a class of k-essence, show distinguishable characteristics through higher order perturbations or energy examination. The constructed domain walls are local, not global minima of the energy among field configurations with fixed topological charge.
Article
Astronomy & Astrophysics
Cedric Deffayet, Sebastian Garcia-Saenz
Article
Astronomy & Astrophysics
Nicolas Boulanger, Cedric Deffayet, Sebastian Garcia-Saenz, Lucas Traina
Article
Astronomy & Astrophysics
Cedric Deffayet, Sebastian Garcia-Saenz, Shinji Mukohyama, Vishagan Sivanesan
Article
Astronomy & Astrophysics
Cedric Deffayet, Shinji Mukohyama, Vishagan Sivanesan