Contact
For internal use only
Christophe Ringeval
Position
Academic staff
Address
Université catholique de Louvain
2, Chemin du Cyclotron - Box L7.01.05
B-1348 Louvain-la-Neuve
Belgium
2, Chemin du Cyclotron - Box L7.01.05
B-1348 Louvain-la-Neuve
Belgium
Phone
+32 10 47 2075
Office
Personal homepage
UCL member card
People responsibilities
Postdocs
PhD students
Visitors
Interns
Former members
Chiara Animali
(Other)
(member since November 2024)
Pierre Auclair
(member since October 2021)
I am a cosmologist mostly interested with the physics of the very early Universe mainly through the prism of gravitational wave detectors. My specialities range from the study of topological defects to the aftermath of a first order phase transition and the formation of Primordial Black Holes; but I am always keen to discover new things. I have been involved in gravitational wave experiments, both ground-based (Virgo) and space-bound (LISA).
I am a cosmologist mostly interested with the physics of the very early Universe mainly through the prism of gravitational wave detectors. My specialities range from the study of topological defects to the aftermath of a first order phase transition and the formation of Primordial Black Holes; but I am always keen to discover new things. I have been involved in gravitational wave experiments, both ground-based (Virgo) and space-bound (LISA).
PhD students
Baptiste Blachier
(FNRS)
(member since October 2023)
Visitors
André Füzfa
(member since October 2006)
Professor at FUNDP, working in theoretical cosmology: interpretations of dark energy, observational constraints from structure formation, Hubble diagram, CMB, ... and on complex systems in general relativity: dynamical systems, multi-physics N-body simulations, numerical relativity.
Professor at FUNDP, working in theoretical cosmology: interpretations of dark energy, observational constraints from structure formation, Hubble diagram, CMB, ... and on complex systems in general relativity: dynamical systems, multi-physics N-body simulations, numerical relativity.
Interns
Former members
Jose Beltran Jimenez
(Postdoc
in IRMP from October 2012 to January 2015)
Current position: Post-doctoral position at CPT, Marseille University
Current position: Post-doctoral position at CPT, Marseille University
Niels Beuseling
(Master student
in IRMP)
Disrael Dacunha
(Postdoc
in IRMP from October 2019 to September 2022)
Antonio De Felice
(Postdoc
in IRMP from October 2007 to October 2009)
Current position: Associate Professor at Yukawa Institute for Theoretical Physics, Kyoto
Current position: Associate Professor at Yukawa Institute for Theoretical Physics, Kyoto
Vittoria Demozzi
(Postdoc
in IRMP from October 2011 to September 2012)
Current position: Department of Electrical Engineering and IT, Patent Attorneys' office Hoffmann-EitlePatent, Munich
Current position: Department of Electrical Engineering and IT, Patent Attorneys' office Hoffmann-EitlePatent, Munich
Marie-Hélène Deproost
(Visitor
in IRMP from September 2013 to December 2013)
Anne-Sylvie Deutsch
(Master student
in IRMP from October 2011 to September 2012)
Current position: PhD student at Penn State University
Current position: PhD student at Penn State University
Martin Evrard
(Master student
in IRMP)
Geoffrey Feraut
(Master student
in IRMP from September 2013 to September 2014)
Christian Fidler
(Postdoc
in IRMP from October 2014 to September 2017)
Current position: Postdoc at RWTH, AAchen University, Germany
Current position: Postdoc at RWTH, AAchen University, Germany
David Frenay
(Master student
in IRMP from September 2010 to June 2011)
Cristian Joana
(PhD student
in IRMP from January 2019 to December 2022)
Francois Kinard
(Master student
in IRMP from September 2012 to September 2013)
Marc Lilley
(Postdoc
in IRMP from March 2010 to September 2010)
Current position: Post-doctoral position at IAP, Paris
Current position: Post-doctoral position at IAP, Paris
Larissa Lorenz
(Postdoc
in IRMP from September 2009 to July 2011)
Current position: Researcher in Future Technologies and Innovation (Bauhaus Luftfahrt e.V., Munich)
Current position: Researcher in Future Technologies and Innovation (Bauhaus Luftfahrt e.V., Munich)
Charles Modera
(Master student
in IRMP)
Marcello Musso
(Postdoc
in IRMP from January 2012 to December 2014)
Sandrine Schlögel
(PhD student
in IRMP from January 2013 to October 2016)
Vincent Spies
(Master student
in IRMP from February 2014 to August 2014)
Teruaki Suyama
(Postdoc
in IRMP from October 2008 to March 2010)
Current position: Professor at RESCUE, the University of Tokyo.
Current position: Professor at RESCUE, the University of Tokyo.
Hiroyuki Tashiro
(Postdoc
in IRMP from October 2009 to August 2011)
Current position: Lecturer at the department of Physics and Astrophysics, Nagoya University
Current position: Lecturer at the department of Physics and Astrophysics, Nagoya University
Olivier Welcomme
(Visitor
in IRMP from February 2019 to May 2019)
Projects
Research directions:
Experiments and collaborations:
Non-active projects
Experiments and collaborations:
Non-active projects
Averaging problem
Christophe Ringeval
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.
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
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.
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).
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
Christophe Ringeval
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).
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
André Füzfa, Christophe Ringeval
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.
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
André Füzfa, Christophe Ringeval
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).
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).
Extra-dimensions
Christophe Ringeval
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).
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).
Gravitational Wave Physics with Virgo
Giacomo Bruno, Antoine Depasse, Jan Govaerts, Jean-Marc Gérard, Vincent Lemaitre, Christophe Ringeval, Andres Tanasijczuk
In July 2018 CP3 members have joined the Virgo Collaboration at the European Gravitational Observatory (EGO) near Pisa in Italy. Virgo is the European laser interferometer for gravitational wave detection. After several years of instrument upgrades, Virgo went in observation mode in August 2017, about one year and half after the two LIGO interferometers in the US had detected for the first time gravitational waves. Virgo and LIGO work in close collaboration, sharing data, analysing data and publishing together. Fundamental research in gravitational wave experimental physics was funded for the first time in Belgium at the end of 2018 with a project led by UCLouvain and ULiege. On the data analysis side the plan is on one side to investigate the properties of binary black hole coalescence events, possibly relating them to theoretical models of dark matter and/or primordial black holes, and on the other to search for a stochastic gravitational wave background originating from the very early moments of the life of the Universe, a discovery that would be foundational for cosmology. On the instrumentation side, contributions to computing and the optical system of the Virgo interferometer are planned.
CP3 members are also actively supporting the Einstein Telescope project, a proposed underground laser interferometer project for gravitational wave detection that is expected to take over from LIGO and Virgo around 2030.
In July 2018 CP3 members have joined the Virgo Collaboration at the European Gravitational Observatory (EGO) near Pisa in Italy. Virgo is the European laser interferometer for gravitational wave detection. After several years of instrument upgrades, Virgo went in observation mode in August 2017, about one year and half after the two LIGO interferometers in the US had detected for the first time gravitational waves. Virgo and LIGO work in close collaboration, sharing data, analysing data and publishing together. Fundamental research in gravitational wave experimental physics was funded for the first time in Belgium at the end of 2018 with a project led by UCLouvain and ULiege. On the data analysis side the plan is on one side to investigate the properties of binary black hole coalescence events, possibly relating them to theoretical models of dark matter and/or primordial black holes, and on the other to search for a stochastic gravitational wave background originating from the very early moments of the life of the Universe, a discovery that would be foundational for cosmology. On the instrumentation side, contributions to computing and the optical system of the Virgo interferometer are planned.
CP3 members are also actively supporting the Einstein Telescope project, a proposed underground laser interferometer project for gravitational wave detection that is expected to take over from LIGO and Virgo around 2030.
Large Scale Structures
André Füzfa, Christophe Ringeval
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.
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
Christophe Ringeval
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.
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
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).
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).
Non-Gaussianity
Christophe Ringeval
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).
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
Christophe Ringeval
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).
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).
Reionisation
Christophe Ringeval
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.
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
Christophe Ringeval
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).
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).
Publications in IRMP
All my publications on Inspire
Number of publications as IRMP member: 50
Last 5 publications
More publications
Number of publications as IRMP member: 50
Last 5 publications
2018
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