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Name

Jose Beltran Jimenez

Position

Former member
Member from October 2012 to January 2015
Current position: Post-doctoral position at CPT, Marseille University

Projects

Research directions:

Cosmology and General Relativity

Non-active projects

Backreaction in modified cosmologies and gravities

Christophe Ringeval

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

Christophe Ringeval

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

Christophe Ringeval

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 IRMP

All my publications on Inspire

Number of publications as IRMP member: 11
Last 5 publications

2015

CP3-15-32: Cascading dust inflation in Born-Infeld gravity

Jose Beltran Jimenez, Lavinia Heisenberg, Gonzalo J. Olmo and Christophe Ringeval

[Abstract] [PDF] [Journal] [Dial]
Published in JCAP 1511 (2015) 046
Refereed paper. September 22.

2014

CP3-14-83: 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] [Dial]
Published in Phys.Rev. D91, 104003 (2015)
Refereed paper. December 9.

CP3-14-69: Infrared lessons for ultraviolet gravity: the case of massive gravity and Born-Infeld

Jose Beltrán Jiménez, Lavinia Heisenberg and Gonzalo Olmo

[Abstract] [PDF] [Journal] [Dial]
Published in JCAP 1411 (2014) 004
Refereed paper. October 30.

CP3-14-16: 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] [Dial]
Published in JCAP 1405 (2014) 031
Refereed paper. March 17.

CP3-14-15: Anisotropic expansion and SNIa: an open issue

Jose Beltran Jimenez, Vincenzo Salzano and Ruth Lazkoz

[Abstract] [PDF] [Journal] [Dial]
Published in Phys. Lett. B741, 168 (2015)
Refereed paper. March 3.

More publications

2014

CP3-14-14: Extended Gauss-Bonnet gravities in Weyl geometry

Jose Beltran Jimenez and Tomi S. Koivisto

[Abstract] [PDF] [Journal] [Dial]
Published in Class.Quant.Grav. 31 (2014) 135002
Refereed paper. March 3.

2013

CP3-13-44: Stability of Horndeski vector-tensor interactions

Jose Beltrán Jiménez, Ruth Durrer, Lavinia Heisenberg and Mikjel Thorsrud

[Abstract] [PDF] [Journal] [Dial]
Published in JCAP 1310 064 (2013)
Refereed paper. September 4.

CP3-13-09: Exact Mapping between Tensor and Most General Scalar Power Spectra

Jose Beltran Jimenez, Marcello Musso and Christophe Ringeval

[Abstract] [PDF] [Journal] [Dial]
Published in Phys. Rev. D88, 043524 (2013)
Refereed paper. March 15.

CP3-13-02: Cosmology with a Continuous Tower of Scalar Fields

Jose Beltran Jimenez, Paulo Santos and David F. Mota

[Abstract] [PDF] [Journal] [Dial]
Published in Phys.Lett. B723 (2013) 7-14
Refereed paper. January 11.

2012

CP3-12-54: A longitudinal gauge degree of freedom and the Pais Uhlenbeck field

Jose Beltran Jimenez, Enea Di Dio and Ruth Durrer

[Abstract] [PDF] [Journal] [Dial]
Published in JHEP 1304 (2013) 030
Refereed paper. December 12.

CP3-12-53: Screening Vector Field Modifications of General Relativity

Jose Beltrán Jiménez, Andre Luis Delvas Froes and David F Mota

[Abstract] [PDF] [Journal] [Dial]
Published in Phys.Lett. B725 (2013) 212-217
Refereed paper. December 12.