Cosmology and General Relativity

Our research interests range from the understanding of the early universe, the place and time at which the candidate unified theories of Nature may have been at work, to late-time cosmology, data analysis and model testing with cosmological observables.
Our data analysis activities have been focused on the Planck satellite measurements and are now turning to the next generation of CMB polarization experiments, such as the CORE satellite. We are also part of the EUCLID and LISA missions, with measurements of the large scale structure of the Universe and gravitational waves, respectively.
Our works on late-time cosmology concern the reionization era and the development of numerical codes to solve for the cosmological perturbations at second order. For this we have developed the SONG code. In particular, our results are used to implement General Relativity effects within the numerical simulations of the formation of the large scale structures.
With respect to early universe cosmology, we explore the observable consequences of Cosmic Inflation and the existence of topological defects, and maintain the public numerical libraries ASPIC and FieldInf allowing to solve any slow-roll and multifield inflationary models.
Another part of our theoretical activities is concerned with modified gravity theories as well as supersymmetric model building for dark matter candidates.



Dark matter and neutrino masses in SUSY models

We study supersymmetric models in which modifications of the neutrino sector, to include a mass term, are connected to the dark matter sector. We analyse if the dark matter particles can be good dark matter candidates by considering cosmological and astrophysical constraints, as well as if the new neutrino sector can accommodate neutrino data.

External collaborators: Suchitat Kulkarni (OAW Wien).

Scalar-tensor theories of gravitation

The strong equivalence principle (SEP) does not hold anymore in various extensions of General Relativity. Its violations can be revealed by the non-universality of free-falling for compact objects and we have developed a generic and effective way to test the SEP in the Cosmic Microwave Background (CMB). A violation of the SEP indeed alters the amplitude of the acoustic oscillations in the primeval plasma. Using the WMAP data, we have contrained a possible SEP violation for the baryons.

Our interests are also focused on the scalar-tensor theories of gravitation and their cosmologies. In a more specific way, we are currently studying a model where the scalar sector is conformally invariant. The effective fluid related to the non-minimally coupled scalar field differs from the other cosmological fluids of radiation by its very particular anisotropic pressure and we are studying its impact on the CMB anisotropies by modifying the CAMB code.

Past projects

Hide past projects.

Averaging problem

Due to the non-commutation of spatial averaging and temporal evolution, inhomogeneities and anisotropies (cosmic structures) influence the evolution of the averaged Universe via the cosmological backreaction mechanism. We study the dynamics of backreaction effects and further introduce a relative entropy to characterize the structure formation in the perturbed Universe. We show this entropy increases during the cosmological evolution.

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).

Cosmic strings

Based on our knowledge of particle physics at very high energy, cosmic strings are a natural consequence of the symmetry breaking mechanism and are expected to be formed during the cooling of the universe. However, they have not been observed yet and our research is concentrated into the various effects they may have in cosmology. The technical difficulties to deal with such systems are overcome using super-computer numerical simulations. We are focusing our present work to the effects induced in the CMB and in other astrophysical observables.

External collaborators: Jun'ichi Yokoyama (University of Tokyo, Japan), Daisuke Yamauchi (RESCUE, Tokyo, Japan), Mairi Sakellariadou (King's College London, U.K.), Patrick Peter, François Bouchet (Institut d'Astrophysique de Paris, France).

Cosmological data

Our expertise on inflation and cosmic strings is involved in the CMB data analysis of the PLANCK satellite.
Our current efforts concern the study of future CMB polarization experiments, ground based, and in space, as the CORE satellite.
We are part of the EUCLID collaboration and interested in the impact of high precision measurements of the matter power spectra of the large scale structures for cosmic inflation.
We are also involved in the LISA project, the giant space interferometer dedicated to gravitational wave astronomy, which should open a new window on cosmic string physics and other early universe phenomena.
Another direction concerns the 21cm cosmological radiation. This radiation is emitted by neutral hydrogen atoms and should shed light into the so-called "dark ages": from the recombination to the reionisation of the universe by the first stars. This new observable is expected to be sensitive to the nature of dark matter as well as to some properties of the inflationary era.

External collaborators: Sébastien Clesse (RWTH, Aachen), V. Vennin (Portsmooth, U.K.), CORE Coll., Euclid Coll., eLISA Coll.

Dark energy

Although the undergoing cosmic acceleration may be explained by a non-vanishing cosmological constant in Einstein gravity, various dynamical effects could very well explain current observations, all dubbed as dark energy.

Quintessence, as a light scalar field minimally coupled to gravity, is a dark energy candidate to explain the recent acceleration of the Universe expansion. The Ratra-Peebles potential and its corrected form in supergravity are under study. Using a modified version of CAMB, including perturbations of the scalar field, we use the latest SNIa and CMB observations to select acceptable points in the parameter space. Starting with the associated matter power spectrum, in collaboration with the LUTh (Paris-Meudon Obs., France) we run N-body simulations of growth of large scale structures where the background evolution is modified by quintessence. We are involved in the Dark Energy Universe Simulation Series (DEUSS) collaboration.

Another dark energy candiate involves cosmic inflation, currently the best explanation of the origin of large scale structures and CMB anisotropies. Similarly, if dark energy is a light scalar field, the current acceleration can be the consequence of quantum fluctuations during cosmic inflation, provided this one occurs at TeV scale.

External collaborators: Jean-Michel Alimi, Yann Rasera, Pier Stefano Corasaniti (Observatoire de Paris-Meudon, France). Teruaki Suyama (The University of Tokyo, Japan), Tomo Takahashi (Saga University, Japan), Masahide Yamaguchi (Tokyo Institute of Technology, Japan), Shuichiro Yokoyama (Nagoya University, Japan).


It is possible to construct classical models of extra-dimensions based on Field Theory and General Relativity. The goal is to gain deeper understanding into these systems based on tractable and well known theories. In particular, the so-called Randall-Sundrum (RS) models in various dimensions can be modelised as hyper-dimensional topological defects. Our present studies concern the realisation of the Dvali-Gabadadze-Porrati mechanism inside hyper-dimensional monopoles, in which four-dimensional gravity can be obtained by trapping gravitons.

External collaborators: Antonio De Felice (The University of Tokyo, Japan).

Large Scale Structures

The statistical properties of large scale structures contain a large amount of information on cosmological observables. The abundance of halos of given mass is sensitive to various cosmological observables such as the equation of state of dark energy, to the amount of primordial non-Gaussianity as well as to the mass and cross section of the dark matter particles. Various of our activities and research are equally focused to the future EUCLID satellite mission.

External collaborators: M. Musso.

Modifications of gravity

The recent acceleration of the universe is explained in the standard model by the presence of a non-vanishing cosmological constant. However, one may also question the validity of General Relativity on length scales that have never been so accurately tested so far. However, it is not trivial to modify gravity and to build at the same time a model which can survive all the experimental tests. In collaboration with S. Capozziello, we looked for cosmological exact solutions for modifications of gravity in the form f(R) where f possesses a constant of motion during the evolution of the universe. In the future we plan to look for the subset of solutions which can describe experimental data from radiation domination up to today's accelerated expansion.

I have been working also in the so called f(G) gravity. This is a work made in collaboration with Shinji Tsujikawa, which aims to give some necessary conditions for a cosmologically viable f(G) gravity, where G is the Gauss-Bonnet scalar, that is a particular quadratic combination of the Riemann tensor. This scalar, G, has the property that, if not coupled, it can be written as a total derivative. Along with these conditions, we provide also some toy-models which fulfill them.

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).


The forthcoming cosmological experiments should provide new insights on the amount of non-Gaussianity eventually present in the Cosmic Microwave Background fluctuations and large scale structures surveys. We study various early universe models that could potentially let some imprints in these observables and especially cosmic strings.

External collaborators: Teruaki Suyama (The University of Tokyo, Japan), Mark Hindmarsh (Sussex University, U.K.), Stéphane Colombi, François Bouchet (Institut d'Astrophysique de Paris, France).

Primordial magnetic fields

Observations show that magnetic fields are present everywhere in the universe. Planets, galaxies, clusters carry magnetic fields of varying strength and coherence size. There are evidences of their presence also in the intergalactic medium and this strongly suggests that their origin might be primordial. A promising candidate for the generation of primordial magnetic fields is inflation. Our work concerns the construction of efficient inflationary mechanisms which could produce the large-scale magnetic fields observed today and it deals in particular with the possible effects that such mechanisms have on the physics of the universe after inflation.

External collaborators: Chiara Caprini (CEA Saclay, France), Teruaki Suyama (The University of Tokyo, Japan).


When computing cosmological predictions it is often assumed that reionisation is homogenous and completely described by only one parameter, it's optical depth. However, reionisation is driven by the local collapse of matter and therefore highly inhomogeneous.
The above method is therefore only an approximation and large corrections can be expected for quantities which depend on the exact dynamics of reionisation.
We study more realistic models on reionisation and their impact on the cosmic microwave background, especially in polarization.

SONG -- Simulations of the early Universe

We work on the development and update of the numerical code SONG which solves the dynamics of the primordial Universe after Inflation. The computational methods used are comparable to the ones employed in the public codes CLASS and CAMB, but we solve the equations of motion beyond the linear order approximation, providing greater precision.
This is crucial for several dynamical effects which are absent in the leading order equations such as the generation of B-mode polarization and non-Gaussianity.

Furthermore, the code plays a central role in the recently developed Newtonian motion gauge framework. In this framework, a Newtonian N-body simulation can be promoted to a full relativistic simulation by interpreting it on the space-time of a specific Newtonian motion gauge. SONG can be used to compute the structure of these space-times up to second order in perturbation theory, thereby including for example the impact of relativity on the dark matter bispectrum.

External collaborators: Guido W. Pettinari, Thomas Tram, Cyril Pitrou (IAP, France).



Cosmology in the era of Euclid and the Square Kilometre Array
Sprenger, Tim and Archidiacono, Maria and Brinckmann, Thejs and Clesse, Sébastien and Lesgourgues, Julien
[Abstract] [PDF] 48 pages, 11 figures, 8 tables
Refereed paper. 6th February.
Observational bounds on extended theories of gravity from energy conditions
Penna-Lima, M. and Vitenti, S. D. P. and Alves, M. E. S. and de Araujo, J. C. N. and Carvalho, F. C.
[Abstract] [PDF] Submitted to PRD
Refereed paper. 19th January.
Optical Follow-up of Planck Cluster Candidates with Small Instruments
Vincent Boucher, Simon de Visscher and Christophe Ringeval
[Abstract] [PDF] [Journal]
Refereed paper. 15th January.


LIGO Lo(g)Normal MACHO: Primordial Black Holes survive SN lensing constraints
Garcia-Bellido, Juan and Clesse, Sebastien and Fleury, Pierre
[Abstract] [PDF] [Journal] 7 pages, 7 figures
Refereed paper. 21st December.
Seven Hints for Primordial Black Hole Dark Matter
Clesse, Sebastien and García-Bellido, Juan
[Abstract] [PDF] [Journal] 11 pages, 3 figures
Refereed paper. 21st December.
Constraints from microlensing experiments on clustered primordial black holes
García-Bellido, Juan and Clesse, Sebastien
[Abstract] [PDF] [Journal] 6 pages, 3 figures
Refereed paper. 21st December.
Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravity
Alves, M. E. S. and Carvalho, F. C. and de Araujo, J. C. N. and Penna-Lima, M. and Vitenti, S. D. P.
[Abstract] [PDF] [Journal] Submitted to JCAP
Refereed paper. 28th November.
CMB constraints on the inflaton couplings and reheating temperature in $alpha$-attractor inflation
Drewes, Marco and Kang, Jin U and Mun, Ui Ri
[Abstract] [PDF] [Journal] [Full text] This was submitted already in August, but published now in JHEP 1711 (2017) 072, so I decided to add UCL as secondary affiliation.
Refereed paper. 22nd November.
ARS Leptogenesis
Drewes, M. and Garbrecht, B. and Hernandez, P. and Kekic, M. and Lopez-Pavon, J. and Racker, J. and Rius, N. and Salvado, J. and Teresi, D.
[Abstract] [PDF] [Journal] 46 pages, 8 figures. Chapter 2 of the review volume: Leptogenesis: Current Challenges for Model Building, Phenomenology and Non-Equilibrium Field Theory
Refereed paper. 20th November.
Multi-Scale Pipeline for the Search of String-Induced CMB Anisotropies
A. Vafaei Sadr, S. Movahed, M. Farhang, C. Ringeval and F. R. Bouchet
[Abstract] [PDF] [Journal]
Refereed paper. 3rd October.
Stochastic gravitational waves from cosmic string loops in scaling
Christophe Ringeval and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in JCAP 1712 (2017) 027
Refereed paper. 13th September.
CMB anisotropies from patchy reionisation and diffuse Sunyaev-Zel'dovich effects
Christian Fidler and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 1710 (2017) 026
Refereed paper. 6th September.
General relativistic weak-field limit and Newtonian N-body simulations
Fidler, Christian and Tram, Thomas and Rampf, Cornelius and Crittenden, Robert and Koyama, Kazuya and Wands, David
[Abstract] [PDF] [Journal]
Refereed paper. 4th September.
The effect of early radiation in N-body simulations of cosmic structure formation
Adamek, Julian and Brandbyge, Jacob and Fidler, Christian and Hannestad, Steen and Rampf, Cornelius and Tram, Thomas
[Abstract] [PDF] [Journal]
Refereed paper. 4th September.
Relativistic initial conditions for N-body simulations
Fidler, Christian and Tram, Thomas and Rampf, Cornelius and Crittenden, Robert and Koyama, Kazuya and Wands, David
[Abstract] [PDF] [Journal]
Refereed paper. 4th September.
Kinetic theory of fermions in curved spacetime
Fidler, Christian and Pitrou, Cyril
[Abstract] [PDF] [Journal]
Refereed paper. 4th September.
Consistent Scalar and Tensor Perturbation Power Spectra in Single Fluid Matter Bounce with Dark Energy Era
Bacalhau, Anna Paula and Pinto-Neto, Nelson and Dias Pinto Vitenti, Sandro
[Abstract] [PDF] [Journal] Submitted to PRD
Refereed paper. 28th June.
Exploring Cosmic Origins with CORE: Survey requirements and mission design
Delabrouille, J. and others
[Abstract] [PDF] [Journal]
Refereed paper. 16th June.
Cosmological constraints from a joint analysis of cosmic microwave background and large-scale structure
Doux, Cyrille and Penna-Lima, Mariana and Vitenti, Sandro D. P. and Tréguer, Julien and Aubourg, Eric and Ganga, Ken
[Abstract] [PDF] [Journal] Submitted to MNRAS
Refereed paper. 15th June.
Anisotropic multiple bounce models
Bacalhau, Anna Paula and Peter, Patrick and D. P. Vitenti, Sandro
[Abstract] [PDF] [Journal] Published in Phys. Rev. D 96, 023517 (2017)
Refereed paper. 16th May.
Exploring Cosmic Origins with CORE: Inflation
Finelli, Fabio and others
[Abstract] [PDF] [Journal]
Refereed paper. 10th January.


Exploring Cosmic Origins with CORE: Cosmological Parameters
Di Valentino, Eleonora et al.
[Abstract] [PDF] [Journal]
Refereed paper. 2nd December.
Wavelet-Bayesian inference of cosmic strings embedded in the cosmic microwave background
J. D. McEwen, S. M. Feeney, H. V. Peiris, Y. Wiaux, C. Ringeval and F. R. Bouchet
[Abstract] [PDF] [Journal]
Refereed paper. 2nd December.
Cosmological N-body simulations including radiation perturbations
Jacob Brandbyge, Cornelius Rampf, Thomas Tram, Florent Leclercq, Christian Fidler, Steen Hannestad
[Abstract] [PDF] [Journal] Submitted to MNRAS
Refereed paper. 26th October.
Shortcomings of New Parametrizations of Inflation
Jerome Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in Phys. Rev. D94, 123521 (2016).
Refereed paper. 16th September.
Relativistic Interpretation of Newtonian Simulations for Cosmic Structure Formation
Fidler, Christian and Tram, Thomas and Rampf, Cornelius and Crittenden, Robert and Koyama, Kazuya and Wands, David
[Abstract] [PDF] [Journal] to be published in JCAP
Refereed paper. 4th July.
Information Gain on Reheating: the One Bit Milestone
Jérôme Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in Phys. Rev. D93, 103532 (2016)
Refereed paper. 9th March.
The Intrinsic Matter Bispectrum in $Lambda$CDM
Tram, Thomas and Fidler, Christian and Crittenden, Robert and Koyama, Kazuya and Pettinari, Guido W. and Wands, David
[Abstract] [PDF] [Journal]
Refereed paper. 1st March.


Cosmic inflation and model comparison
Vincent Vennin, Jérôme Martin and Christophe Ringeval
[Journal] [Full text] Published in Comptes Rendus Physique, Volume 16, Issue 10, December 2015, Pages 960–968
Refereed paper. 11th December.
Precise numerical estimation of the magnetic field generated around recombination
Fidler, Christian and Pettinari, Guido and Pitrou, Cyril
[Abstract] [PDF] [Journal]
Refereed paper. 25th November.
Large scale CMB anomalies from thawing cosmic strings
Christophe Ringeval, Daisuke Yamauchi, Jun'ichi Yokoyama and François R. Bouchet
[Abstract] [PDF] [Journal] Published in JCAP 1602 (2016) 033
Refereed paper. 8th October.
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.
General relativistic corrections to $N$-body simulations and the Zel'dovich approximation
Fidler, Christian and Rampf, Cornelius and Tram, Thomas and Crittenden, Robert and Koyama, Kazuya and Wands, David
[Abstract] [PDF] [Journal]
Refereed paper. 21st May.


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.
Observing the Inflationary Reheating
Jerome Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in Phys. Rev. Lett. 114, 081303 (2015)
Refereed paper. 30th October.
How Well Can Future CMB Missions Constrain Cosmic Inflation?
Jerome Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in JCAP 1410 (2014) 038
Refereed paper. 16th July.
Planck 2013 results. I. Overview of products and scientific results
Ade, P.A.R. and others
[Abstract] [PDF] [Journal] Published in Astron. Astrophys, 571, A1 (2014)
Refereed paper. 11th July.
Compatibility of Planck and BICEP2 in the Light of Inflation
Jerome Martin, Christophe Ringeval, Roberto Trotta and Vincent Vennin
[Abstract] [PDF] [Journal] Published in in Phys. Rev. D90, 063501 (2014)
Refereed paper. 1st June.
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.
On the Markovian assumption in the excursion set approach: the approximation of Markov Velocities
Marcello Musso and Ravi K. Sheth
[Abstract] [PDF] [Journal] Published in MNRAS 443 (2014) 1601-1613
Refereed paper. 3rd February.
Stochasticity in halo formation and the excursion set approach
Marcello Musso and Ravi K. Sheth
[Abstract] [PDF] [Journal] Published in MNRAS 442 (2014) 401-405
Refereed paper. 15th January.


The Best Inflationary Models After Planck
Jerome Martin, Christophe Ringeval, Roberto Trotta and Vincent Vennin
[Abstract] [PDF] [Journal] Published in JCAP 1403 (2014) 039
Refereed paper. 13th December.
Fast Bayesian inference for slow-roll inflation
Christophe Ringeval
[Abstract] [PDF] [Journal] Published in MNRAS 439, 3253 (2014)
Refereed paper. 10th December.
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.
The importance of stepping up in the excursion set approach
Marcello Musso and Ravi K. Sheth
[Abstract] [PDF] [Journal] Published in MNRAS 438 (2014) 2683-2693
Refereed paper. 4th June.
The excursion set approach in non-Gaussian random fields
Marcello Musso and Ravi K. Sheth
[Abstract] [PDF] [Journal] Pubished in MNRAS 439 (2014) 3051-3063
Refereed paper. 6th May.
Encyclopaedia Inflationaris
Jerome Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in Phys. Dark Univ. 003, 01 (2014)
Refereed paper. 25th March.
Planck 2013 results. XV. CMB power spectra and likelihood
Planck Collaboration
[Abstract] [PDF] [Journal] Published in Astron. Astrophys, 571, A15 (2014)
Refereed paper. 25th March.
Planck 2013 results. XXV. Searches for cosmic strings and other topological defects
Planck Collaboration
[Abstract] [PDF] [Journal] Published in Astron. Astrophys, 571, A25 (2014)
Refereed paper. 25th March.
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.
K-inflationary Power Spectra at Second Order
Jerome Martin, Christophe Ringeval and Vincent Vennin
[Abstract] [PDF] [Journal] Published in JCAP 06 (2013) 021
Refereed paper. 12th March.
Magneto-reheating constraints from curvature perturbations
Christophe Ringeval, Teruaki Suyama and Jun'ichi Yokoyama
[Abstract] [PDF] [Journal] Published in JCAP 09 (2013) 020
Refereed paper. 26th February.
A Boltzmann treatment for the vorton excess problem
Patrick Peter and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 05 (2013) 005
Refereed paper. 6th February.
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.
Early Universe Tomography with CMB and Gravitational Waves
Sachiko Kuroyanagi, Christophe Ringeval and Tomo Takahashi
[Abstract] [PDF] [Journal] Published in Phys. Rev. D87, 083502 (2013)
Refereed paper. 10th January.


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.
Dark energy from inflation
Christophe Ringeval
[Journal] [Full text] Published in J.Phys.Conf.Ser. 485, 012023 (2014)
Contribution to proceedings. 12th September.
Background reionization history from omniscopes
Sebastien Clesse, Laura Lopez-Honorez, Christophe Ringeval, Hiroyuki Tashiro and Michel H. G. Tytgat
[Abstract] [PDF] [Journal] Published in Phys. Rev. D86, 123506 (2012)
Refereed paper. 21st August.
Searching for Standard Clocks in the Primordial Universe
Xingang Chen and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 08 (2012) 014
Refereed paper. 29th May.
Scale dependent halo bias in the excursion set approach
Marcello Musso, Aseem Paranjape and Ravi K. Sheth
[Abstract] [PDF] [Journal] Published in MNRAS 427 (2012) 3145-3158
Refereed paper. 17th May.
All sky CMB map from cosmic strings integrated Sachs-Wolfe effect
Christophe Ringeval and François R. Bouchet
[Abstract] [PDF] [Journal] Published in Phys. Rev. D86, 023513 (2012)
Refereed paper. 24th April.
Reheating constraints in inflationary magnetogenesis
Vittoria Demozzi and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 05 (2012) 009
Refereed paper. 15th February.
One step beyond: The excursion set approach with correlated steps
Marcello Musso and Ravi K. Sheth
[Abstract] [PDF] [Journal] Published in MNRAS 423 (2012) L102-L106
Refereed paper. 23rd January.
De l'éclipse totale du Soleil à l'énigme de l'énergie sombre
Jean-Marc Gérard
[Full text] Published in Revue des Questions Scientifiques, 183 (2012) 145-168
Refereed paper. 10th January.


Observational signatures of a non-singular bouncing cosmology
Marc Lilley, Larissa Lorenz, Sebastien Clesse
[Abstract] [PDF] [Journal] Published in JCAP 06 (2011) 004.
Refereed paper. 19th April.
Ionized bubble number count as a probe of non- Gaussianity
Tashiro, Hiroyuki and Sugiyama, Naoshi
[Abstract] [PDF] [Journal] submitted to MNRAS
Refereed paper. 4th April.


Primordial magnetic fields with X-ray and S-Z cluster survey
Tashiro, Hiroyuki and Takahashi, Keitaro and Ichiki, Kiyotomo
[Abstract] [PDF] Submitted to Monthly Notices of the Royal Astronomical Society
Refereed paper. 22nd October.
Hunting Down the Best Model of Inflation with Bayesian Evidence
Jerome Martin, Christophe Ringeval and Roberto Trotta
[Abstract] [PDF] [Journal] Published in Phys. Rev. D83, 063524 (2011)
Refereed paper. 22nd September.
Second order cross-correlation between kSZ and 21 cm fluctuations from the EoR
Hiroyuki Tashiro, Nabila Aghanim, Mathieu Langer, Marian Douspis, Saleem Zaroubi, Vibor Jelic
[Abstract] [PDF] Accepted for publication by MNRAS
Refereed paper. 31st August.
Introducing the Dark Energy Universe Simulation Series (DEUSS)
Y. Rasera, J-M. Alimi, J. Courtin, F. Roy, P-S. Corasaniti, A. Füzfa and V. Boucher
[Abstract] [PDF] [Journal] Invisible Universe International Conference, UNESCO-Paris, 2009. DEUS Consortium reference paper.
Contribution to proceedings. 15th July.
Hybrid inflation along waterfall trajectories
Sébastien Clesse
[Abstract] [PDF] [Journal] updated version accepted for publication in Phys.Rev.D.
Refereed paper. 23rd June.
Initial conditions in hybrid inflation: exploration by MCMC technique
Sébastien Clesse
[Abstract] [PDF] Proceedings of the 2010 Moriond Conference - Cosmology Session
Contribution to proceedings. 23rd June.
Cosmic string loop distribution on all length scales and at any redshift
Larissa Lorenz, Christophe Ringeval and Mairi Sakellariadou
[Abstract] [PDF] [Journal] Published in JCAP 10 (2010) 003
Refereed paper. 7th June.
Dark energy from primordial inflationary quantum fluctuations
Christophe Ringeval, Teruaki Suyama, Tomo Takahashi, Masahide Yamaguchi, Shuichiro Yokoyama
[Abstract] [PDF] [Journal] Published in Phys. Rev. Lett. 105, 121301 (2010)
Refereed paper. 3rd June.
Cosmic strings and their induced non-Gaussianities in the cosmic microwave background
Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Advances in Astronomy, vol. 2010, Article ID 380507 (2010)
Refereed paper. 27th May.
Cosmological perturbation in f(R,G) theories with a perfect fluid.
Antonio De Felice, Jean-Marc Gerard and Teruaki Suyama
[Abstract] [PDF] [Journal] Phys. Rev. D82 (2010) 063526
Refereed paper. 14th May.
First CMB constraints on the inflationary reheating temperature
Jerome Martin and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Phys. Rev. D82, 023511 (2010)
Refereed paper. 3rd May.
Geometrically Consistent Approach to Stochastic DBI Inflation
Larissa Lorenz, Jerome Martin, Jun'ichi Yokoyama
[Abstract] [PDF] [Journal] Published in Phys. Rev. D82, 023515 (2010)
Refereed paper. 22nd April.
Nonabelian Bosonic Currents in Cosmic Strings
Lilley, Marc and Di Marco, Fabrizio and Martin, Jerome and Peter, Patrick
[Abstract] [PDF] [Journal] Published in Physical Review D
Refereed paper. 29th March.
Graviton confinement inside hypermonopoles of any dimension
Seán Murray, Christophe Ringeval and Simone Zonetti
[Abstract] [PDF] [Journal] Published in JCAP 09 (2010) 015
Refereed paper. 26th February.
Anamorphosis in Hybrid Inflation: How to avoid fine-tuning of Initial Conditions?
Sébastien Clesse
[Abstract] [PDF] [Journal] AIP Proceedings of the "Invisible Universe" conference, Palais de l'Unesco, Paris, 29th June to 4th July 2008.
Contribution to proceedings. 2nd February.
Imprints of dark energy on cosmic structure formation: II) Non-Universality of the halo mass function
Jérôme Courtin, Yann Rasera, Jean-Michel Alimi, Pier-Stefano Corasaniti, Vincent Boucher, André Füzfa
[Abstract] [PDF] [Journal] Published in MNRAS (410) 1911, 2011.
Refereed paper. 20th January.
Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity
Kobayashi, Tsutomu and Tashiro, Hiroyuki and Suzuki, Daichi
[Abstract] [PDF] [Journal] Phys.Rev.D81:063513,2010
Refereed paper. 20th January.


CMB temperature trispectrum of cosmic strings
Mark Hindmarsh, Christophe Ringeval and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in Phys. Rev. D81, 063505 (2010)
Refereed paper. 6th November.
Dirac-Born-Infeld and k-inflation: the CMB anisotropies from string theory
Christophe Ringeval
[Abstract] [PDF] [Journal] Published in J. Phys. Conf. Ser. 203, 012056 (2010)
Contribution to proceedings. 12th October.
Fractal initial conditions and natural parameter values in hybrid inflation
Sébastien Clesse, Christophe Ringeval, Jonathan Rocher
[Abstract] [PDF] [Journal] Published in Phys. Rev. D80, 123534 (2009)
Refereed paper. 2nd September.
Cosmological perturbations of a perfect fluid and noncommutative variables
Antonio De Felice, Jean-Marc Gerard and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in Physical Review D81 (2010) 063527
Refereed paper. 25th August.
CMB temperature bispectrum induced by cosmic strings
Mark Hindmarsh, Christophe Ringeval and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in Phys. Rev. D80, 083501 (2009)
Refereed paper. 4th August.
Scalar mode propagation in modified gravity with a scalar field
Antonio De Felice and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in Physical Review D
Refereed paper. 31st July.
Solar system constraints on f(G) gravity models
Antonio De Felice and Shinji Tsujikawa
[Abstract] [PDF] [Journal] Published in Physical Review D
Refereed paper. 13th July.
Definition of a time variable with Entropy of a perfect fluid in Canonical Quantum Gravity
Francesco Cianfrani, Giovanni Montani, Simone Zonetti
[Abstract] [PDF] [Journal] Published in Class.Quant.Grav.26:125002,2009
Refereed paper. 27th April.
Vacuum structure for scalar cosmological perturbations in Modified Gravity Models
Antonio De Felice and Teruaki Suyama
[Abstract] [PDF] [Journal] Published in JCAP
Refereed paper. 14th April.
Fluid Entropy as Time-Variable in Canonical Quantum Gravity
Francesco Cianfrani, Giovanni Montani, Simone Zonetti
[Abstract] [PDF] Proceedings of The 3rd Stueckelberg Workshop on Relativistic Field Theories
Contribution to proceedings. 6th April.
Charged seven-dimensional spacetimes with spherically symmetric extra-dimensions
Antonio De Felice and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Phys. Rev. D79, 123525 (2009)
Refereed paper. 2nd April.
Imprints of Dark Energy on Cosmic Structure Formation I) Realistic Quintessence Models and the Non-Linear Matter Power Spectrum
Jean-Michel Alimi, André Füzfa, Vincent Boucher, Yann Rasera, Jérôme Courtin, Pier-Stefano Corasaniti
[Abstract] [PDF] [Journal] Published in the Monthly Notices of the Royal Astronomical Society, 401, 775-790 (2010).
Refereed paper. 31st March.


An Awesome Hypothesis for Dark Energy : The Abnormally Weighting Energy
A. Füzfa, J.-M. Alimi
[Abstract] [PDF] [Journal] Proceedings of the 11th Marcel Grossmann meeting on general relativity
Contribution to proceedings. 31st December.
Construction of cosmologically viable f(G) dark energy models
Antonio De Felice and Shinji Tsujikawa
[Abstract] [PDF] [Journal] Published in Physics Letters B
Refereed paper. 3rd November.
Is Dark Energy Abnormally Weighting?
J.-M. Alimi, A. Füzfa
[Abstract] [PDF] [Journal] Published in International Journal of Modern Physics, D 16, 2587 (2008)
Refereed paper. 3rd October.
The Abnormally Weighting Energy Hypothesis: the Missing Link between Dark Matter and Dark Energy
J.-M. Alimi, A. Füzfa
[Abstract] [PDF] [Journal] JCAP09(2008)014
Refereed paper. 3rd October.
Avoiding the blue spectrum and the fine-tuning of initial conditions in hybrid inflation
Sébastien Clesse and Jonathan Rocher
[Abstract] [PDF] [Journal] Published in Phys. Rev. D79, 103507 (2009)
Refereed paper. 26th September.
Massive gravitons trapped inside a hypermonopole
Antonio De Felice and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Physics Letters B 671, 158-161 (2009)
Refereed paper. 2nd September.
K-inflationary power spectra in the uniform approximation
Larissa Lorenz, Jerome Martin and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Phys. Rev. D78, 083513 (2008)
Refereed paper. 18th July.
Constraints on kinetically modified inflation from WMAP5
Larissa Lorenz, Jerome Martin and Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Phys. Rev. D78, 063543 (2008)
Refereed paper. 15th July.
f(R) cosmology by Noether's symmetry
Antonio De Felice, Salvatore Capozziello
[Abstract] [PDF] [Journal] JCAP0808(2008)016
Refereed paper. 27th June.


Toward a Unified Description of Dark Energy and Dark Matter from the Abnormally Weighting Energy Hypothesis
A. Füzfa, J.-M. Alimi
[Abstract] [PDF] [Journal] Published in PRD 75 123007 (2007)
Refereed paper. 6th December.
Brane inflation and the WMAP data: a Bayesian analysis
Larissa Lorenz, Jérôme Martin, Christophe Ringeval
[Abstract] [PDF] [Journal] Published in JCAP 04 (2008) 001.
Refereed paper. 24th September.
Small-angle CMB temperature anisotropies induced by cosmic strings
Aurélien Fraisse, Christophe Ringeval, David Spergel and François Bouchet
[Abstract] [PDF] [Journal] Published in Phys. Rev. D78 (2008) 043535
Refereed paper. 13th August.
Cosmological evolution of cosmic string loops
Christophe Ringeval, Mairi Sakellariadou, François R. Bouchet
[Abstract] [PDF] [Journal] Published in JCAP 0702 (2007) 023.
Refereed paper. 19th February.
The exact numerical treatment of inflationary models
Christophe Ringeval
[Abstract] [PDF] [Journal] Published in Lect. Notes Phys 738, 243-273 (2008)
Refereed paper. 14th January.


The strong equivalence principle from a gravitational gauge structure
Jean-Marc Gerard
[Abstract] [PDF] [Journal] Published in Class.Quantum Grav. 24 (2007) 1867-1877
Refereed paper. 5th July.


A cosmological test for general relativity
V. Boucher
[Abstract] [PDF] Published in Gravitation & Cosmology 11 (2005) 71-74
Contribution to proceedings. 26th September.

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