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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Professor Pedro Ferreira

Professor of Astrophysics

Research theme

  • Particle astrophysics & cosmology

Sub department

  • Astrophysics

Research groups

  • Beecroft Institute for Particle Astrophysics and Cosmology
pedro.ferreira@physics.ox.ac.uk
Telephone: 01865 (2)73366
Denys Wilkinson Building, room 757
Personal Webpage
  • About
  • Publications

Constraints on quantum gravity and the photon mass from gamma ray bursts

(2021)

Authors:

Deaglan J Bartlett, Harry Desmond, Pedro G Ferreira, Jens Jasche
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Euclid preparation. XIV. The complete calibration of the Color-Redshift Relation (C3R2) survey: data release 3

Astrophysical Journal Supplement Series IOP Science 256:1 (2021) 9

Authors:

Sa Stanford, D Masters, B Darvish, D Stern, Jg Cohen, P Capak, N Hernitschek, I Davidzon, J Rhodes, Db Sanders, B Mobasher, Fj Castander, S Paltani, N Aghanim, A Amara, N Auricchio, A Balestra, R Bender, C Bodendorf, D Bonino, E Branchini, J Brinchmann, V Capobianco, C Carbone, J Carretero, R Casas, M Castellano, S Cavuoti, A Cimatti, R Cledassou, Cj Conselice, L Corcione, A Costille, M Cropper, H Degaudenzi, M Douspis, F Dubath, S Dusini, P Fosalba, M Frailis, E Franceschi, P Franzetti, M Fumana, B Garilli, C Giocoli, F Grupp, Svh Haugan, H Hoekstra, W Holmes, F Hormuth

Abstract:

The Complete Calibration of the Color–Redshift Relation (C3R2) survey is obtaining spectroscopic redshifts in order to map the relation between galaxy color and redshift to a depth of i ∼ 24.5 (AB). The primary goal is to enable sufficiently accurate photometric redshifts for Stage iv dark energy projects, particularly Euclid and the Nancy Grace Roman Space Telescope (Roman), which are designed to constrain cosmological parameters through weak lensing. We present 676 new high-confidence spectroscopic redshifts obtained by the C3R2 survey in the 2017B–2019B semesters using the DEIMOS, LRIS, and MOSFIRE multiobject spectrographs on the Keck telescopes. Combined with the 4454 redshifts previously published by this project, the C3R2 survey has now obtained and published 5130 high-quality galaxy spectra and redshifts. If we restrict consideration to only the 0.2 < zp < 2.6 range of interest for the Euclid cosmological goals, then with the current data release, C3R2 has increased the spectroscopic redshift coverage of the Euclid color space from 51% (as reported by Masters et al.) to the current 91%. Once completed and combined with extensive data collected by other spectroscopic surveys, C3R2 should provide the spectroscopic calibration set needed to enable photometric redshifts to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for Roman.
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R2/Higgs inflation and the hierarchy problem

arXiv (2021)

Authors:

Pedro G Ferreira, Christopher T Hill, Johannes Noller, Graham G Ross

Abstract:

We analyse Starobinsky inflation in the presence of the Brout Englert Higgs (BEH) boson with a non-minimal coupling to the Ricci scalar, R. The latter induces a coupling of the massive scaleron associated with the R2 term to the BEH boson and this leads to a radiative correction to the BEH mass that must be fine tuned to keep the scalar light. For the case of R2 driven inflation this requires a high level of fine tuning of order 1 part in 108; for the case of Higgs inflation it is very much greater. We consider a scale invariant extension of the R2/Higgs model and find that for R2 driven inflation but not for Higgs inflation the required fine tuning is significantly reduced to one part in 103–4. We consider the vacuum stability of the fine tuned model and its reheating and dilaton abundance after inflation. We also discuss possible gravitational wave signals associated with the model and the constraint on the mass of scalar or fermion dark matter candidates if they are produced by the gravitational couplings of the scalaron.

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Constraints on Equivalence Principle Violation from Gamma Ray Bursts

(2021)

Authors:

Deaglan J Bartlett, Dexter Bergsdal, Harry Desmond, Pedro G Ferreira, Jens Jasche
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Constraints on equivalence principle violation from gamma ray bursts

Physical Review D American Physical Society 104 (2021) 084025

Authors:

Deaglan J Bartlett, Dexter Bergsdal, Harry Desmond, Pedro G Ferreira, Jens Jasche

Abstract:

Theories of gravity that obey the Weak Equivalence Principle have the same Parametrised Post-Newtonian parameter $\gamma$ for all particles at all energies. The large Shapiro time delays of extragalactic sources allow us to put tight constraints on differences in $\gamma$ between photons of different frequencies from spectral lag data, since a non-zero $\Delta \gamma$ would result in a frequency-dependent arrival time. The majority of previous constraints have assumed that the Shapiro time delay is dominated by a few local massive objects, although this is a poor approximation for distant sources. In this work we consider the cosmological context of these sources by developing a source-by-source, Monte Carlo-based forward model for the Shapiro time delays by combining constrained realisations of the local density field using the Bayesian origin reconstruction from galaxies algorithm with unconstrained large-scale modes. Propagating uncertainties in the density field reconstruction and marginalising over an empirical model describing other contributions to the time delay, we use spectral lag data of Gamma Ray Bursts from the BATSE satellite to constrain $\Delta \gamma < 2.1 \times 10^{-15}$ at $1 \sigma$ confidence between photon energies of $25 {\rm \, keV}$ and $325 {\rm \, keV}$.
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