Jose Beltran Jimenez
Former member
Postdoc in CP3 from October 2012 to January 2015
Current position: Post-doctoral position at CPT, Marseille University.
Past projects
Hide past projects.

I am involved in the following research direction:

Backreaction in modified cosmologies and gravities

Our universe is homogeneous an isotropic on very large scales. However, when we go down to smaller scales inhomogeneities become more and more important. Given that Einstein equations are non-linear, it is clear than averaging and time-evolution are operations that do not commute. Thus, it is a crucial question to be addressed the importance of the non-commutativity of these two operations when we measure observables of the background cosmology. In General Relativity and a universe dominated by dust, there seems to be a general consensus that these corrections are small. However, when we consider modified cosmologies (either multifluid scenarios or alternative theories of gravity), the issue remains unclear. Moreover, this will need to be addressed to be able to use the next generation of high precision cosmological data to constrain such alternative scenarios.

External collaborators: Peter Dunsby (University of Cape Town), Alvaro de la Cruz Dombriz (Universidad Complutense de Madrid), Diego Saez (University of the Basque Country.

Cosmic inflation

The first measurements of acoustic peaks in the CMB anisotropies strongly suggest that the birth of cosmological fluctuations may have taken place during an early inflationary era of the universe.
In this domain, our activities deal with the construction of explicit models of inflation as well as the extraction of their observable consequences. Our fields of expertise comprise some actively debated subjects as the existence of features (e.g. trans-Planckian effects), inflation with non-minimally coupled scalar fields, DBI- and brane inflation as in the context of String Theory.
For all these theories, we are maintaining various numerical tools such as the ASPIC and FieldInf librairies allowing to compute reheating-consistent predictions for comparison with cosmological data.

External collaborators: Jérôme Martin (IAP, Paris, France), Vincent Vennin (Portsmouth, U.K.), Sébastien Clesse (RWTH, Aachen, Germany).

Modified gravity

Born-Infeld inspired theories. Although General Relativity has proven to be very successful in the scales where it has been tested, when going to high curvature regimes it is commons the appearance of singularities like the Big Bang and/or black holes singularities. This motivates the modification of gravity in such a regime to try to regularize those singularities. We study a natural extension of these models and study their predictions in cosmology and astrophysics

External collaborators: Jose Beltran Jimenez (CPT, Université de Marseille), Lavinia Heisenberg (University of Stockholm), Gonzalo Olmo (University of Valencia).

Publications in CP3
All my publications on Inspire


Cascading dust inflation in Born-Infeld gravity
Jose Beltran Jimenez, Lavinia Heisenberg, Gonzalo J. Olmo and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 1511 (2015) 046
Refereed paper. 22nd September.


On the consistency of universally non-minimally coupled f(R,T,RT) theories
Ismael Ayuso, Jose Beltran Jimenez and Alvaro de la Cruz Dombriz
[Abstract] [PDF] [Journal] Published in Phys.Rev. D91, 104003 (2015)
Refereed paper. 9th December.
Infrared lessons for ultraviolet gravity: the case of massive gravity and Born-Infeld
Jose Beltrán Jiménez, Lavinia Heisenberg and Gonzalo Olmo
[Abstract] [PDF] [Journal] Published in JCAP 1411 (2014) 004
Refereed paper. 30th October.
Backreaction mechanism in multifluid and extended cosmologies
Jose Beltran Jimenez, Alvaro de la Cruz-Dombriz, P.K.S. Dunsby and Diego Saez-Gomez
[Abstract] [PDF] [Journal] Published in JCAP 1405 (2014) 031
Refereed paper. 17th March.
Anisotropic expansion and SNIa: an open issue
Jose Beltran Jimenez, Vincenzo Salzano and Ruth Lazkoz
[Abstract] [PDF] [Journal] Published in Phys. Lett. B741, 168 (2015)
Refereed paper. 3rd March.
Extended Gauss-Bonnet gravities in Weyl geometry
Jose Beltran Jimenez and Tomi S. Koivisto
[Abstract] [PDF] [Journal] Published in Class.Quant.Grav. 31 (2014) 135002
Refereed paper. 3rd March.


Stability of Horndeski vector-tensor interactions
Jose Beltrán Jiménez, Ruth Durrer, Lavinia Heisenberg and Mikjel Thorsrud
[Abstract] [PDF] [Journal] Published in JCAP 1310 064 (2013)
Refereed paper. 4th September.
Exact Mapping between Tensor and Most General Scalar Power Spectra
Jose Beltran Jimenez, Marcello Musso and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Phys. Rev. D88, 043524 (2013)
Refereed paper. 15th March.
Cosmology with a Continuous Tower of Scalar Fields
Jose Beltran Jimenez, Paulo Santos and David F. Mota
[Abstract] [PDF] [Journal] Published in Phys.Lett. B723 (2013) 7-14
Refereed paper. 11th January.


A longitudinal gauge degree of freedom and the Pais Uhlenbeck field
Jose Beltran Jimenez, Enea Di Dio and Ruth Durrer
[Abstract] [PDF] [Journal] Published in JHEP 1304 (2013) 030
Refereed paper. 12th December.
Screening Vector Field Modifications of General Relativity
Jose Beltrán Jiménez, Andre Luis Delvas Froes and David F Mota
[Abstract] [PDF] [Journal] Published in Phys.Lett. B725 (2013) 212-217
Refereed paper. 12th December.

[UCLouvain] - [SST] [IRMP] - [SC]
Contact : Jérôme de Favereau
Job opportunities Post-doctoral positions in BSM phenomenology at colliders and in astrophysics
Postdoctoral Position on advanced analysis techniques applied to the CMS di-Higgs study
Post-doctoral positions in collider phenomenology and particle astrophysics
EOS be.h : 10 PhD positions