Zobrazeno 1 - 10
of 170
pro vyhledávání: '"João Magueijo"'
Autor:
João Magueijo
Publikováno v:
Physics Letters B, Vol 858, Iss , Pp 139001- (2024)
In this paper we entertain a Machian setting where local physics is non-locally affected by the whole Universe, taking the liberty to identify the local (“Newton's bucket”) with our visible Universe, and the whole Universe (Mach's “fixed stars
Externí odkaz:
https://doaj.org/article/2d4c392740aa434f8eb330314b6a0abb
Autor:
Raymond Isichei, João Magueijo
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 84, Iss 4, Pp 1-9 (2024)
Abstract We study the Hamiltonian structure of unimodular-like theories, where the cosmological constant (or other supposed constants of nature) are demoted from fixed parameters to classical constants of motion. No new local degrees of freedom are p
Externí odkaz:
https://doaj.org/article/c64ad35d0dfa4040ba8cbea966912c90
Publikováno v:
Physics Letters B, Vol 855, Iss , Pp 138810- (2024)
We relate physical time with the topology of magnetic field vortices. We base ourselves on a formulation of unimodular gravity where the cosmological constant Λ appears as the canonical dual to a variable which on-shell becomes four-volume time. If
Externí odkaz:
https://doaj.org/article/cc6fe31808154a91affbb0ea6a3d4317
Autor:
João Magueijo
Publikováno v:
Physics Letters B, Vol 820, Iss , Pp 136487- (2021)
We propose that cosmological time is effectively the conjugate of the constants of nature. Different definitions of time arise, with the most relevant related to the constant controlling the dynamics in each epoch. The Hamiltonian constraint then bec
Externí odkaz:
https://doaj.org/article/d3eac8a4d3934b91a0bba77bec203d2a
Publikováno v:
Physics Letters B, Vol 781, Iss , Pp 510-516 (2018)
We explore the possibility that well known properties of the parity operator, such as its idempotency and unitarity, might break down at the Planck scale. Parity might then do more than just swap right and left polarized states and reverse the sign o
Externí odkaz:
https://doaj.org/article/d34bb0e50d74488b8de55e90155511c6
Publikováno v:
Physics Letters B, Vol 736, Iss C, Pp 317-320 (2014)
Several approaches to quantum gravity suggest that the standard description of spacetime as probed at low-energy, with four dimensions, is replaced in the Planckian regime by a spacetime with a spectral dimension of two. The implications for relativi
Externí odkaz:
https://doaj.org/article/a707cae0e3ee4df6822fd532d9886d21
Autor:
João Magueijo, Lee Smolin
Publikováno v:
Universe, Vol 5, Iss 3, p 84 (2019)
In this paper, we propose that cosmological time is a quantum observable that does not commute with other quantum operators essential for the definition of cosmological states, notably the cosmological constant. This is inspired by properties of a me
Externí odkaz:
https://doaj.org/article/7676e28ef3084ec49976b4e7ce9828ad
Autor:
Bruno Alexandre, João Magueijo
Publikováno v:
Physical Review
We re-examine the Hartle-Hawking wave function from the point of view of a quantum theory which starts from the connection representation and allows for off-shell non-constancy of $\Lambda$ (as in unimodular theory), with a concomitant dual relationa
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::42de799436f6a8b1a752454f4f0b8f6a
https://doi.org/10.1103/physrevd.107.063501
https://doi.org/10.1103/physrevd.107.063501
Autor:
Raymond Isichei, João Magueijo
Publikováno v:
Physical Review
We derive the fixed-Λ and unimodular propagators using the path integral formalism as applied to the Einstein-Cartan action. The simplicity of the action (which is linear in the lapse function) allows for an exact integration starting from the lapse
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ccc15456aa5e4fd11659550204a00583
https://doi.org/10.1103/physrevd.107.023526
https://doi.org/10.1103/physrevd.107.023526
Autor:
Steffen Gielen, João Magueijo
Publikováno v:
Physical Review D. 107
We formulate the transition from decelerated to accelerated expansion as a bounce in connection space and study its quantum cosmology, knowing that reflections are notorious for bringing quantum effects to the fore. We use a formalism for obtaining a
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::8033790cb7cb6415ebf8d16de451340d
https://doi.org/10.1103/physrevd.107.023518
https://doi.org/10.1103/physrevd.107.023518